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Journal Articles: River Deltas and Fish

Articles  :   Geology  |   Ecosystems  |   Climate Change  |   Sea Level Rise  |   Fauna  |   Birds  |   Fish

Allman, R. J. and C. B. Grimes (1998). "Growth and mortality of little tunny (Euthynnus alletteratus) larvae off the Mississippi River plume and Panama City, Florida." Bulletin of Marine Science 62(1): 189-197.

Larval and early juvenile little tunny, Euthynnus alletteratus, were collected from the northern Gulf of Mexico (434 fish from the Mississippi River delta region and 150 off Panama City, Florida) using a I x 2 m, 0.947-mm mesh neuston net and a 1 x 1 m, 0.333-mm mesh Tucker trawl. Sagittae were removed from 200 fish collected from the Mississippi River delta region and 150 collected from off Panama City, Florida, and examined whole at 800X magnification. Daily growth increments were visible in the sagittae of little tunny (2.5-14.0 mm SL) which ranged in age from 2 to 13 d. Growth estimated as the slope of a regression of SL on age, was rapid (1.07 mm d(-1)). Fish collected off Panama City grew faster than those collected in the vicinity of the Mississippi River discharge plume. Instantaneous daily mortality rates, estimated from survivorship curves were higher in the Mississippi River plume fish (0.95) than those from Panama City, Florida (0.72).

Alongi, D. M., P. Christoffersen, et al. (1992). "The Influence of Fresh-Water and Material Export on Sedimentary Facies and Benthic Processes within the Fly Delta and Adjacent Gulf of Papua (Papua-New-Guinea)." Continental Shelf Research 12(2-3): 287-326.

Large volumes of freshwater and suspended material debouch from the Fly River in southwestern Papua New Guinea into the Gulf of Papua, greatly influencing the hydrography and sedimentary processes within the river delta and adjacent shelf region. Sedimentary facies within the subtidal regions of the Fly Delta are composed mainly of compacted and eroded very fine black sand, and highly laminated, muddy sand and sandy mud, progressing to prodelta mud with intermixed primary and biogenic structures in the inner Gulf of Papua. These prodelta muds grade further to mixed terrigenous-carbonate deposits southwards into the northern Great Barrier Reef and Torres Strait, and to well-bioturbated, fluid mud northwards into the Gulf of Papua. The transition from physically-dominated, estuarine conditions within the delta to more quiescent, marine conditions on the shelf leads to concomitant changes in sediment chemistry, microbial activity and infaunal and epifaunal communities. Particulate (C, N, P) and dissolved inorganic and organic nutrient concentrations were a function of sediment type (higher in finer deposits) rather than location (delta vs gulf). C:N:P ratios of solid-phase nutrients varied greatly, but were usually less than those predicted by the Redfield ratio. Mean interstitial concentrations of dissolved inorganic nutrients were low (mu-M range), but dissolved organic carbon, nitrogen and phosphorus levels were equivalent to those found in higher latitude systems. Fluxes of dissolved inorganic nutrients were generally low (mu-mol m-2 day-1). Flux rates were mostly negative (into the sediment) in the delta suggesting that these deposits are a sink for nutrients. In the offshore deposits, dissolved inorganic fluxes were higher and mostly positive indicating that they are a source for dissolved nutrients. Standing crops of bacteria (range: below detection limits-2.5 x 10(10) cells g-1 dry wt), meiofauna (range: 5-750 individuals 10 cm-2; 9-1006-mu-g dry wt 10 cm-2) and infauna (range: 86-5555 individuals m-2; 0.10-5.85 g AFDW m-2) were generally lower in the delta than in the gulf. The infauna was dominated by nematodes, copepods, foraminifera and small, tube-building, deposit- and suspension-feeding polychaetes and amphipods. Rates of bacterial productivity were very erratic with sediment depth across stations, ranging from 0-2108 mg C m-2 day-1 (DNA synthesis) and from 0-228 mg C m-2 day-1 (protein synthesis), respectively. Rates of benthic respiration and DOC flux across the sediment-water interface were generally high, ranging from 63-780 mg C m-2 day-1 and from -797 to 514 mg C m-2 day-1, respectively. Epibenthos were more diverse (at the phyletic level) at the mid-shelf than inshore, composed mainly of sponges, crabs, crinoids, echinoids, bivalves, hydroids and asteroids. Demersal nekton abundance was low, dominated by the leatherjacket, Paramonacanthus filicauda, the pony fish, Leiognathus splendens and the grunter, Pomadasys argyreus, suggesting limited transfer of infaunal biomass to higher trophic levels. The response of the benthic regime to the export of freshwater and material from the Fly River generally conforms to the RHOADS et al. [(1985) Continental Shelf Research, 4, 189-213] model of benthic response to effluent derived from the Changjiang River in the East China Sea and is similar to infaunal and sedimentary patterns off the Amazon. Nutrient release from the delta sediments contributes little to water-column production, but in the gulf, nutrient efflux from the benthos contributes, on average, 38 and 61% of the annual N and P requirements of phytoplankton production, reflecting closer benthic-pelagic coupling and enrichment of biological productivity in the Gulf of Papua due to nutrient export from the Fly River.

Amadi, A. A. (1990). "A Comparative Ecology of Estuaries in Nigeria." Hydrobiologia 208(1-2): 27-38.

A bar-built estuary, a drowned river valley and two river delta estuaries were compared and contrasted to elucidate the impact of some abiotic factors, notably climate, salinity, and oxygen on the distribution of the aquatic fauna and flora. Salinity was recognizable as the key factor responsible for the population dynamics in these habitats. The mangrove community is characteristically zoned, but development and distribution of the trees is restricted in view of coastal geomorphic and hydrological processes to the western banks of the estuaries. The preponderance of marine fish species in estuaries was confirmed, although the wide salinity tolerance of some prolific-breeding Cichlidae from freshwater was noted. Forty-eight species of bony fishes were recorded in Lagos Lagoon, the Escravos, and Qua Ibo estuaries and classified by salinity tolerance into stenohaline and euryhaline marine species (66%), and freshwater species (34%). The same estuarine ichthyofauna were split into trophic groups: piscivores (46%), zooplankton feeders (10%), meiobenthos feeders (27%), and macrobenthos feeders (17%).

Baker, P. F., T. P. Speed, et al. (1995). "Estimating the Influence of Temperature on the Survival of Chinook Salmon Smolts (Oncorhynchus-Tshawytscha) Migrating through the Sacramento-San-Joaquin River Delta of California." Canadian Journal of Fisheries and Aquatic Sciences 52(4): 855-863.

Data from the U.S. Fish and Wildlife Service are used to investigate the relationship between water temperature and survival of hatchery-raised fall-run chinook salmon (Oncorhynchus tshawytscha) smelts migrating through the Sacramento - San Joaquin Delta of California. A formal statistical model is presented for the release of smelts marked with coded-wire tags (CWTs) in the lower Sacramento River and the subsequent recovery of marked smelts in midwater trawls in the Delta. This model treats survival as a logistic function of water temperature, and the release and recovery of different CWT groups as independent mark-recapture experiments. Iteratively reweighted least squares is used to fit the model to the data, and simulation is used to establish confidence intervals for the fitted parameters. A 95% confidence interval for the upper incipient lethal temperature, inferred from the trawl data by this method, is 23.01 +/- 1.08 degrees C This is in good agreement with published experimental results obtained under controlled conditions (24.3 +/- 0.1 and 25.1 +/- 0.1 degrees C for chinook salmon acclimatized to 10 and 20 degrees C, respectively): this agreement has implications for the applicability of laboratory findings to natural systems.

Bano, N., M. U. Nisa, et al. (1997). "Significance of bacteria in the flux of organic matter in the tidal creeks of the mangrove ecosystem of the Indus River delta, Pakistan." Marine Ecology-Progress Series 157: 1-12.

We studied bacterial biomass and production in 3 tidal creeks (Isaro, Gharo and Phitti Creeks) in the mangrove forests in the Indus River delta, Pakistan, to assess the significance of bacteria-mediated carbon fluxes in the creek ecosystem. Bacterial biomass, bacterial carbon production (BCP) and primary productivity (PP) were measured periodically for over a year during 1991-92. BCP was high, generally 50 to 300 mu g C l(-1) d(-1). Despite such high BCP, bacterial abundance remained between 1 x 10(6) ml(-1) and 4 x 10(6) ml(-1) (20 to 80 mu g C l(-1)) indicating tight coupling between bacterial production and removal. Specific growth rates generally ranged from 1 to 7 d(-1) but the rate reached 24 d(-1) during a phytoplankton bloom, apparently a red tide, and this was an unprecedented growth rate for a natural assemblage. The abundance of attached bacteria exhibited a large variation, ranging from 4 to 92 % (mean 35 +/- 21 %, n = 41) in Isaro Creek and from 14 to 84% (mean 37 +/- 28%, n = 10) in Gharo Creek. Bacterial production due to attached bacteria was 73 to 96 % of the total. Thus, a major fraction of BCP may have been directly available to metazoan grazers. BCP was generally much higher than net PP; the yearly integrated average BCP/PP for all sites was 2.0. Thus, the growth of bacteria, attached and free, probably represented the major pathway of the production of high quality (low C:N) biomass potentially available to the grazers. Average yearly integrated bacterial carbon demand (BCD), estimated conservatively by assuming a 30 % growth efficiency for all sites, was 6.9 times net PP. Thus, the creek water columns were strongly and persistently net heterotrophic. Data integrated over the entire study period show that even if all phytoplankton production was utilized by bacteria it would satisfy only 7 to 20% of the BCD; the remaining 80 to 93% of BCD would be met by reduced carbon from other sources. Phytoplankton production was light Limited due to high turbidity and, apparently, the majority of BCP could be supported by the input of mangrove detritus. Estimates of utilizable dissolved organic carbon (UDOC) in selected samples were 97 to 656 mu g C l(-1), indicating that in order to sustain the measured BCD (643 +/- 671 mu g C l(-1) d(-1)) the UDOC pool would turnover in <1 d to a few days. Limited data suggest that bacterial production was carbon rather than N or P limited, consistent with sustained high levels of inorganic N and P in the surface water. Since mangrove detritus provides most of the energy for bacterial production, which in turn is a significant source of high quality food for grazers, particularly via ingestion of attached bacteria, we predict that the ongoing destruction of mangrove forests in the Indus delta and elsewhere could have a major impact on mangrove ecosystem structure and functioning and the production of economically important fish and shrimp in mangrove creeks.

Bardin, O. and D. Pont (2002). "Environmental factors controlling the spring immigration of two estuarine fishes Atherina boyeri and Pomatoschistus spp. into a Mediterranean lagoon." Journal of Fish Biology 61(3): 560-578.

Atherina boyeri, a pelagic species, mainly entered it Mediterranean lagoon in the Rhone River Delta, during the day, whatever the flow direction, Flow velocity did not appear to be a significant factor and its swimming abilities, seemed to he sufficient to cope with the observed velocity. The combined responses of Pomatoschistus spp,. benthic species, to the different environmental factors clearly demonstrated it change in behavioural response during their ontogenic development, i.e. a shift from passive to active or active-passive migration, Young Pomatoschistus spp. (<20 mm L-T) exhibited it behaviour that correspond to the classical selective tidal stream transport of young fishes towards estuarine areas (passive drifting). Large Pomatoschistus spp. were also able to enter the lagoon with the flow but they remained negatively affected by the flow velocity, The diel cycle appeared to be the main factor controlling the immigration of A. bolyeri. into the lagoon whereas Pomatoschistus spp, seemed more sensitive to hydrographic conditions prevailing at the connection. (C) 2002 The Fisheries Society of the British Isles Published by Elsevier Science Ltd. All rights reserved.

Baron, J. S., N. L. Poff, et al. (2002). "Meeting ecological and societal needs for freshwater." Ecological Applications 12(5): 1247-1260.

Human society has used freshwater from rivers, lakes, groundwater,, and wetlands for many different urban, agricultural, and industrial activities, but in doing so has overlooked its value in supporting ecosystems. Freshwater is vital to human life and societal well-being, and thus its utilization for consumption, irrigation, and transport has long taken precedence over other commodities and services provided by freshwater ecosystems. However, there is growing recognition that functionally intact and biologically complex aquatic ecosystems provide many economically valuable services and long-term benefits to society. The short-term benefits include ecosystem goods and services, such as food supply, flood control, purification of human and industrial wastes, and habitat for plant and animal life-and these are costly, if, not impossible, to replace. Long-term benefits include the sustained provision of those goods and services, as well as the adaptive capacity of aquatic ecosystems to respond to future environmental alterations, such as climate change. Thus, maintenance of the processes and properties that support freshwater ecosystem integrity should be included in debates over sustainable water resource allocation. The purpose of this report is to explain how the integrity of freshwater ecosystems depends upon adequate quantity, quality, timing, and temporal variability of water flow. Defining these requirements in a comprehensive but general manner provides a better foundation for their inclusion in current and future debates about allocation of water resources. In this way the needs of freshwater ecosystems can be legitimately recognized and addressed. We also recommend ways in which freshwater ecosystems can be protected, maintained, and restored. Freshwater ecosystem structure and function are tightly linked to the watershed or catchment of which they are a part. Because riverine networks, lakes, wetlands, and their connecting groundwaters, are literally the "sinks" into 'Which landscapes drain, they are greatly influenced by terrestrial processes, including many human uses or modifications of land and water. Freshwater ecosystems, whether lakes, wetlands, or rivers, have specific requirements in terms of quantity, quality, and seasonality of their water supplies. Sustainability normally requires these systems to fluctuate within a natural range of variation. Flow regime, sediment and organic matter inputs, thermal and light characteristics, chemical and nutrient characteristics, and biotic assemblages are fundamental defining attributes of freshwater ecosystems. These attributes impart relatively unique characteristics of productivity and biodiversity to each ecosystem. The natural range of variation in each of these attributes is critical to maintaining the integrity and dynamic potential of aquatic ecosystems; therefore, management should allow for dynamic change. Piecemeal approaches cannot solve the problems confronting freshwater ecosystems. Scientific definitions of the requirements to protect and maintain aquatic ecosystems are necessary but insufficient for establishing the appropriate distribution between societal and ecosystem water needs. For scientific knowledge to be implemented science must be connected to a political agenda for sustainable development. We offer these recommendations as. a beginning to redress how water is viewed and managed in the United States: (1) Frame national and regional water management policies to explicitly incorporate freshwater ecosystem needs, particularly those related to naturally variable flow regimes and to the linking of water quality with water quantity; (2) Define water resources to include watersheds, so that freshwaters are viewed within a landscape, or systems context; (3) Increase communication and education across disciplines, especially among engineers, hydrologists, economists, and ecologists to facilitate an integrated view of freshwater resources; (4) Increase restoration efforts, using well-grounded ecological principles as guidelines; (5) Maintain and protect the remaining freshwater ecosystems that have high integrity; and (6) Recognize the dependence of human society on naturally functioning ecosystems.

Boyer, M. E., J. O. Harris, et al. (1997). "Constructed crevasses and land gain in the Mississippi River delta." Restoration Ecology 5(1): 85-92.

Extensive land loss, which is mostly wetland loss, has taken place during this century in the Mississippi River delta and other river deltas. Our purpose was to evaluate the effectiveness of constructing ''artificial'' crevasses, or cuts in the natural levee, made by the U.S. Fish and Wildlife Service in the Delta National Wildlife Refuge (DNWR) to slow or reverse this type of land loss. Land growth of the crevasses was determined from aerial photographs and was related to crevasse-site characteristics. The newly constructed crevasses create emergent wetlands after 2 years of subaqueous growth at about 4.7 ha/year and an average cost of $21,377 per crevasse. The present total cost per hectare declines with age as new land builds, and it will equal $48 per hectare if all the open water in the receiving ponds fills in. At these rates, the net land loss rates in the DNWR measured from 1958 to 1978 would be compensated for by the building of 63 crevasses, 24 of which are already in place.

Butala, H., C. Metzger, et al. (2004). "Microsomal estrogen metabolism in channel catfish." Marine Environmental Research 58(2-5): 489-494.

Our goal was to study the involvement of cytochrome P450 genes in estrogen metabolism and the extent to which the potentially carcinogenic 4-hydroxyestradiol metabolite is formed by channel catfish (Ictalurus punctatus; CC). Estradiol metabolism and ethoxyresorufin-O-deethylase (EROD) activity were assessed in several tissues from fish collected from three variably contaminated sites in the Mississippi River Delta, from laboratory control fish, and from fish exposed to 20 mg/kg benzo(a)pyrene (BaP) i.p. for 4 days. Liver EROD activity was induced by BaP, but Delta fish EROD activities were not statistically higher than activities in control fish. Gill microsomal EROD activity was also induced by BaP, but activities were 8- to 77-fold lower than those from liver. The predominant estrogen metabolites formed by CC liver, gill and gonad microsomes were 2-hydroxyestradiol and estrone as detected by GC/MS. Liver and gill 2-hydroxyestradiol formation was induced in BaP-dosed fish. The trends in hydroxyestradiol formation in field collected fish were more variable. In all fish liver microsomes there was more 2- compared to 4-hydroxyestradiol formed. However, BaP-treatment increased the 4:2 hydroxyestradiol ratio from 0.04 in control fish to 0.2 in BaP-exposed fish, suggesting that BaP induces the formation of the potentially genotoxic estrogen metabolite. No detectable 4-hydroxyestradiol was produced by gill and gonad microsomes. These results will ultimately help in determining which fish P450 genes are susceptible to environmental contamination and may be involved in estrogen genotoxicity. (C) 2004 Elsevier Ltd. All rights reserved.

Castellanos, D. L. and L. P. Rozas (2001). "Nekton use of submerged aquatic vegetation, marsh, and shallow unvegetated bottom in the Atchafalaya River Delta, a Louisiana tidal freshwater ecosystem." Estuaries 24(2): 184-197.

We sampled nekton (fishes and decapod crustaceans) in submerged aquatic vegetation (SAV) (Potamogeton nodosus, Najas guadalupensis), in emergent marsh vegetation (Sagittaria spp. and Scirpus americanus), and over unvegetated bottom associated with three islands in the Atchafalaya River Delta, Louisiana. The purpose of our study was to quantify nekton densities in these major aquatic habitat types and to document the relative importance of these areas to numerically dominant aquatic organisms. We collected a total of 33 species of fishes and 7 species of crustaceans in 298 1-m(2) throw trap samples taken over three seasons: summer (July and August 1994), fall (September and October 1994), and spring (May and June 1995). Fishes numerically accounted for > 65% of the total organisms collected. Vegetated areas generally supported much higher nekton densities than unvegetated sites, although bay anchovies Anchoa mitchilli were more abundant over unvegetated bottom than in most vegetated habitat types. Among vegetation types, most species showed no apparent preference between SAV and marsh. However, inland silversides Menidia beryllina and freshwater gobies Gobionellus shufeldti were most abundant in Scirpus marsh in summer, and blue crabs Callinectes sapidus were most abundant in SAV (Potamogeton) in spring. Several species (sheepshead minnow Cyprinodon variegatus, rainwater killifish Lucania parva, and blue crab) apparently selected the vegetated backmarsh of islands (opposite of riverside) over streamside Scirpus marsh. Freshwater gobies, in contrast, were most abundant in streamside Scirpus marsh. Densities of juvenile blue crabs were high (up to 17 m(-2)) in vegetated delta habitat types and comparable to values reported from more saline regions of Gulf Coast estuaries. Shallow vegetated habitat types of the Atchafalaya River Delta and other tidal freshwater systems of the Gulf Coast may be: important nursery areas for blue crabs and other estuarine species.

Ceccherelli, V. U., M. Mistri, et al. (1994). "Predation Impact on the Meiobenthic Harpacticoid Canuella-Perplexa in a Lagoon of the Po River Delta, Italy." Estuaries 17(1B): 283-287.

The impact of predation by juvenile marbled gobies, Pomatoschistus marmoratus, on the meiobenthic harpacticoid copepod Canuella perplexa was investigated at a subtidal statio'' located in a shallow-water, brackish embayment of the Po River delta, northern Italy, in summer and fall 1978. In August, predation mainly centered on adults, with a very large number of prey for each predator; the energy supplied by the harpacticoid is high enough to sustain, almost entirely, the gobies' daily energy requirement. The situation is different in September and October, when the adult copepod population declines dramatically and predation is shifted to less energy-providing copepodites and marbled gobies sensibly widen their prey spectrum. C. perplexa showed alterations of biological parameters, such as clutch size and average brood size, to cope with such a heavy predation pressure.

Colombini, I., R. Berti, et al. (1995). "Environmental-Factors Influencing the Zonation and Activity Patterns of a Population of Periophthalmus-Sobrinus Eggert in a Kenyan Mangrove." Journal of Experimental Marine Biology and Ecology 190(1): 135-149.

The activity rhythms and zonation of a population of Periophthalmus sobrinus were studied along the muddy mangrove banks of the Tana river delta (Kenya). A transect, perpendicular to the water channel, was subdivided into sections 1 m in width parallel to the river bank. The number of surface-active mudskippers and their zonation was recorded over several tidal cycles. Fishes found resting on their nests were also recorded. The observations were carried out over two periods of 48 consecutive tidal hours corresponding to a spring and a neap tide, Environmental variables such as tidal level, air temperature and relative humidity were also recorded. Periophthalmus sobrinus was active both diurnally and nocturnally and during spring tide all the observed mudskippers were active on the mud surface. At neap tide more than half of the total number of animals sighted were found resting on their nests. During this synodic phase, daytime sightings decreased drastically because the mudskippers took refuge inside the nests. Since P. sobrinus normally tends to avoid water, its mean hourly zonation at spring tide was more variable than at neap tide. Differences in mean hourly zonation were also found between night and day of the spring tide. Activity patterns and zonation of the mudskippers were directly influenced by the synodic and tidal cycles and depended more on environmental factors such as air temperature and relative humidity than on the diel light cycle.

Colombini, I., R. Berti, et al. (1996). "Foraging strategy of the mudskipper Periophthalmus sobrinus Eggert in a Kenyan mangrove." Journal of Experimental Marine Biology and Ecology 197(2): 219-235.

The feeding behaviour of Periophthalmus sobrinus was studied in a population living along the channels of the Tana river delta. In November 1993 mudskippers were sampled every 2 tidal h for two consecutive spring and neap tides both during the day and night. The fishes were sexed and their stomach contents analysed. The results indicated that the mudskipper has a carnivorous diet and forages during both day and night although feeding greatly decreases after dark. Quantitative and qualitative differences in diet were found during the day and night of the two synodic and tidal phases. These differences were also demonstrable in the two sexes. The study showed that females of P. sobrinus are more selective than males and that differences between the two sexes may be related to reproductive condition. Furthermore, the mudskippers showed a tidal rhythm in feeding behaviour with peaks of activity around low tide (LT) on spring tides and around high tide (HT) on neap tides. Foraging activity seems to be influenced by the different spatial and temporal distributions of the mudskipper's prey caused by synodic, tidal and diel changes in the environment.

Corsi, I., M. Mariottini, et al. (2003). "Fish as bioindicators of brackish ecosystem health: integrating biomarker responses and target pollutant concentrations." Oceanologica Acta 26(1): 129-138.

Biological responses and contaminant levels in biological tissues were investigated in fish specimens of grass goby (Zosterisessor ophiocephalus) collected in spring 2000 in a moderately polluted brackish ecosystem, the Orbetello lagoon (southern coast of Tuscany, Italy). The complexity of harmful effects that contaminants may cause in fish over time was assessed. General condition indices (somatic liver index, and gonadal somatic index), cytochrome P450 enzymes, acetylcholinesterase activity and ovarian morphology were integrated with the content of organochlorines (OCs-hexachlorobenzene, DDTs and polychlorinated biphenyls) in liver and ovaries and p-nonylphenol (NP) and lower ethoxylate (NPE1-2) content in muscle and ovaries as well. Samples collected from the western basin of the lagoon near the Orbetello sewage treatment plant had somatic liver index values and two P450 activities significantly higher than those collected from the same basin at the Albegna river delta and in the Ansedonia canal in the eastern basin (P < 0.05). On the other hand, while muscle content of p-NP and NPE1-2 was significantly higher in samples from the Orbetello and Albegna river sites than in samples from the Ansedonia canal site, OC levels in liver (DDTs > PCBs > HCB) were particularly lower in samples from STP compared to levels detected in sites AC and AR. Light microscopy of ovaries revealed that although the gonads were sexually mature, the diameter of the oocytes and eggs was smaller than that commonly reported. High levels of M and NPs were, in fact, observed in grass goby ovaries, and the differences observed between acetylcholinesterase activities among investigated sites suggest exposure to insecticides as well. The integration of biological responses and contaminant tissue content reveals that certain areas of the lagoon are selectively impacted by various human activities and helps in distinguishing relationships between biological responses and contaminant load in the lagoon environment. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/CNRS/IRD. All rights reserved.

D'Agrosa, C., C. E. Lennert-Cody, et al. (2000). "Vaquita bycatch in Mexico's artisanal gillnet fisheries: Driving a small population to extinction." Conservation Biology 14(4): 1110-1119.

The world's most endangered marine cetacean, the vaquita (Phocoena sinus), continues to be caught in small-mesh gillnet fisheries throughout much of its range. We monitored fishing effort and incidental vaquita mortality in the upper Gulf of California, Mexico, from January 1993 to January 1995 to study the magnitude and causes of the incidental take. Of those factors studied, including net mesh size, soaktime, and geographic area, none contributed significantly to the incidental mortality rate of the vaquita, implying that the principal cause of mortality is fishing with gillnets per se. The total estimated incidental mortality caused by the fleet of El Golfo de Santa Clara was 39 vaquitas per year (95% CI = 14, 93), over 17% of the most recent estimate of population size. El Golfo de Santa Clara is one of three main ports that support gillnet fisheries throughout the range of the vaquita. Preliminary results indicate that fishing effort for San Felipe, Baja California, is comparable to that of El Golfo de Santa Clara, suggesting that this estimate of incidental mortality of vaquitas represents a minimum. We strongly recommend a complete and permanent ban on gillnets in the area. Alternative or supplemental mitigation strategies include (1) a maximum annual allowable mortality limit of vaquitas; (2) mandatory observer coverage of all boats fishing within the Upper Gulf of California and Colorado River Delta Biosphere Reserve; (3) extension of the Upper Gulf of California and Colorado River Delta Biosphere Reserve to encompass all known vaquita habitat; (4) rigorous enforcement of new and existing regulations; and (5) development of alternative sources of income for gillnet fishers.

Dagg, M. J. and J. J. Govoni (1996). "Is ichthyoplankton predation an important source of copepod mortality in subtropical coastal waters?" Marine and Freshwater Research 47(2): 137-144.

The significance of ichthyoplankton-induced mortality to copepods was examined at three localities in the northern Gulf of Mexico: in the winter at a site of an exceptionally high concentration of larval spot, Leiostomus xanthurus; in the winter at a highly productive region near the Mississippi River delta; and in the summer in a highly eutrophic estuary dominated by larval bay anchovy, Anchoa mitchilli. In each region, ichthyoplankton ingestion of copepod eggs, nauplii and copepodids was compared with production rates and stocks of the dominant copepod species in the same waters. In all cases, predation from the dominant larval species and from the total ichthyoplankton assemblage was much less than prey production. It is concluded that ichthyoplankton predation in these regions rarely has any significant effect on copepod population dynamics, and therefore larval competition for food is unlikely to contribute to density-dependent mortality.

Darnaude, A. M., C. Salen-Picard, et al. (2004). "Depth variation in terrestrial particulate organic matter exploitation by marine coastal benthic communities off the Rhone River delta (NW Mediterranean)." Marine Ecology-Progress Series 275: 47-57.

Carbon and nitrogen stable isotopes were used to study depth variation in terrestrial particulate organic matter (POM) sedimentation off the mouth of the Rhone River delta, and its use by the main benthic invertebrates (polychaetes, crustaceans, molluscs and echinoderms) and flatfishes (Arnoglossus laterna, Buglossidium luteum and Solea solea). Coastal water POM and surface sediment exhibited low delta(13)C values, denoting dominance of terrestrial material in their carbon pools (25 to 80% and >50%, respectively), but the importance of river input differed as a function of depth. Terrestrial organic matter contribution to the total POM was greatest at 30-50 m (72 to 99%), and least at 70-100 in depth (25 to 77%). Most of the invertebrate groups studied (delta(13)C = -24.5 to -17.5parts per thousand; delta(15)N = 4.3 to 9.7parts per thousand) mainly relied on marine primary production irrespective of depth. However, deposit-feeding polychaetes mainly exploited terrestrial POM, and carnivorous and suspension-feeding polychaetes, bivalves, brachyurans and shrimps (Caridea) showed a partial uptake of terrestrial POM, depending on its availability. Incorporation of terrestrial POM by flatfishes (delta(13)C = -22.4 to -16.8parts per thousand; delta(15)N = 9.7 to 11.2parts per thousand.) was species- and depth-dependent. It was related not only to the fishes' diets but also to the trophic adaptability of their prey. S. solea, the main consumer of deposit-feeding polychaetes, showed the lowest VC irrespective of depth, but flatfish exploitation of terrestrial POM peaked at 30-50 m, where both polychaete consumption by fishes and terrestrial POM use by the benthos were maximal. Unlike most estuarine systems, terrestrial inputs in deltaic areas can therefore peak at intermediate depths, where some of the marine macrobenthos, including flatfishes, efficiently exploit them. These results allow better assessment of the role of river input to marine coastal zones in increasing fish abundance, and will therefore be of major interest for demersal fisheries management off deltaic areas.

Delgado, M. and M. Alcaraz (1999). "Interactions between red tide microalgae and herbivorous zooplankton: the noxious effects of Gyrodinium corsicum (Dinophyceae) on Acartia grani (Copepoda  :  Calanoida)." Journal of Plankton Research 21(12): 2361-2371.

Gyrodinium corsicum is a dinoflagellate responsible for recurrent water discolourations during winter in Alfacs Bay (Ebre River delta, NW Mediterranean). Since first detected in 1994, episodic mortality of mussels and fish was attributed to this organism, although no direct evidence was obtained. In order to establish the direct role of the dinoflagellate in the mortality of marine fauna, we have studied the effects of G.corsicum on a potential predator, the co-occurring planktonic copepod Acartia grani. Female A.grani were exposed to different concentrations of intact cells, and <5 mu m and <0.2 mu m filtrates of the dinoflagellate. At concentrations of greater than or equal to 3100 cells ml(-1), G.corsicum reduced feeding and egg production rates, and caused paralysis and death of A,grani. Low dinoflagellate concentrations (630 cells ml(-1)) or the <5 mu m and <0.2 mu m filtrates were harmless, at least for the duration of the experiment. Our study demonstrated that a possible poisoning effect due to the ingestion of the dinoflagellate by the copepod must be disregarded, and the toxic effects of soluble substances excreted by the dinoflagellate, or accompanying free-living toxic bacteria, were not causes of copepad paralysis and death. Scanning electron microscopy of female A.grani exposed to G.corsicum indicated a clear tendency of the dinoflagellate to adhere to the copepod cuticle at preferential zones like the urosome and the antennae. Apparently, direct contact between the copepod and the dinoflagellate is a prerequisite for the noxious effects. Amongst other ecological consequences, the development of G.corsicum blooms represents a drastic reduction of grazing pressure in the system through the control of the herbivorous populations. Whether mechanical or chemical effects are the primary reasons for the observed effects is unknown, and to elucidate this will require further research.

Demestre, M., L. Recasens, et al. (1989). "Evolution of Fishing During the Last 2 Decades in the Lagoons of the Ebro River Delta (Catalonia, Spain)." Bulletin De La Societe Zoologique De France-Evolution Et Zoologie 114(4): 21-30.

Ditty, J. G., R. F. Shaw, et al. (1994). "A Re-Description of Atlantic Spadefish Larvae, Chaetodipterus-Faber (Family, Ephippidae), and Their Distribution, Abundance, and Seasonal Occurrence in the Northern Gulf-of-Mexico." Fishery Bulletin 92(2): 262-274.

The Atlantic spadefish (Chaetodipterus faber) is the only member of the family Ephippidae in the western Atlantic Ocean and its life history is poorly understood. We redescribe Atlantic spadefish larvae, discuss their relationship to known larvae of other ephippid genera, and discuss the distribution, abundance, and seasonal occurrence of Atlantic spadefish in the northern Gulf of Mexico. Larval Atlantic spadefish are characterized by a small, peak-like, median supraoccipital crest with a single, dorsally directed spine; large preopercle spines, numerous serrate ridges, and other spines on the head; a deep, robust body which becomes laterally compressed; heavy body pigmentation; and early development of specialized spinous scales or ''prescales'' (at about 5.5-mm standard length [SL]). Transition to juvenile stage begins about 8.0-8.5 mm SL. Developmental morphology and head spination of Atlantic spadefish is similar to that of Pacific spadefish, Chaetodipterus zonatus. Sequence of fin completion is pelvics - dorsal and anal soft rays - dorsal spines-pectorals. Overall, greater-than-or-equal-to 85% of Atlantic spadefish larvae were found in waters greater-than-or-equal-to 28.0-degrees-C and between 26.7 and 31.3 ppt. Larvae occur primarily in coastal waters, except near the Mississippi River delta, an area with a narrow shelf and rapidly increasing water depths. Delta waters may offer additional habitat suitable to Atlantic spadefish larvae because of lower salinities. Larvae are primarily collected between June and August and in the north-central Gulf of Mexico. Larval Atlantic spadefish are apparently rare in the eastern Gulf off Florida. Catch rates near the Mississippi River delta during August were higher than elsewhere in the north-central Gulf and suggest a possible association with riverine frontal areas which requires further study.

Ditty, J. G., R. F. Shaw, et al. (2004). "Distribution of carangid larvae (Teleostei  :  Carangidae) and concentrations of zooplankton in the northern Gulf of Mexico, with illustrations of early Hemicaranx amblyrhynchus and Caranx spp. larvae." Marine Biology 145(5): 1001-1014.

We examined 1,825 bongo-net samples collected during Southeast Area Monitoring and Assessment Program (SEAMAP) ichthyoplankton surveys of United States Gulf of Mexico waters (1982-1986) for carangid larvae. Objectives were to describe the distribution of carangid larvae and to examine distribution patterns relative to areas of higher zooplankton volumes in order to reveal areas that may be important nurseries. Samples contained about 29,200 carangid larvae from 13 species or species complexes in 11 genera. Chloroscombrus chrysurus and Decapterus punctatus accounted for 91.7% of all larvae. We found that the 'scads' (D. punctatus, Trachurus lathami, and Selar crumenophthalmus) utilize temporally and/or spatially distinct spawning strategies to reduce co-occurrence of larvae. Samples contained fewer larvae than expected of the amberjacks (Seriola spp.), Caranx crysos, and C. hippos/latus given the abundance of adults in the survey area, possibly due to inadequate sampling at appropriate times and locations, gear avoidance, or gear bias. Zooplankton displacement volumes (ZDVs) differed among regions and seasons and were inversely related to surface salinity and station depth. Differences among years were not significant. ZDVs were consistently highest near the Mississippi River delta and along the western Louisiana/eastern Texas shelf, and moderately high during summer and fall along the shelf break, with localized pockets of elevated volumes over the eastern Gulf shelf. We suggest that Chloroscombrus chrysurus, D. punctatus, T. lathami, and possibly Oligoplites saurus, Hemicaranx amblyrhynchus and Caranx crysos spawn in frontal areas and/or along other hydrographic features that promote higher productivity. We provide new illustrations and descriptive information for the larvae of H. amblyrhynchus and discuss characters that separate early larvae of several species of Caranx.

Doucett, R. R., W. Hooper, et al. (1999). "Identification of anadromous and nonanadromous adult brook trout and their progeny in the Tabusintac River, New Brunswick, by means of multiple-stable-isotope analysis." Transactions of the American Fisheries Society 128(2): 278-288.

Multiple-stable-isotope analysis was used to infer anadromous and nonanadromous origins of adult brook trout Salvelinus fontinalis and maternal migration history of age-0 progeny in the Tabusintac River, New Brunswick. Forty-seven adults collected above head of tide displayed deviations (delta) from standard ratios of C-13/C-12, N-15/N-14, and S-34/S-32 of -30.3 parts per thousand to -16.0 parts per thousand, 7.4 parts per thousand to 16.8 parts per thousand, and 1.5 parts per thousand to 14.1 parts per thousand, respectively; higher values (positive or less negative) denote relatively greater enrichment in the heavier isotope. Isotopically enriched brook trout exhibited isotope profiles typical of fish from marine environments, and those that were isotopically depleted were considered to be of freshwater origin. Age-0 brook trout from Home Camp Pool, the most downstream freshwater rearing site sampled, were more enriched (delta(13)C = -24.4 +/- 2.7 parts per thousand (mean +/- SD), delta(15)N = 12.5 +/- 3.1 parts per thousand, and delta(34)S = 7.4 +/- 1.8 parts per thousand) than those at two other sites, and were believed to be progeny of anadromous females. Age-0 brook trout from the Bathurst Highway site (delta(13)C = -27.9 +/- 0.6 parts per thousand, delta(15)N = 8.9 +/-: 0.8 parts per thousand, and delta(34)S = 5.8 +/- 0.8 parts per thousand) and the Little Eskedelloc River (delta(13)C = -28.6 +/- 0.5 parts per thousand, delta(15)N = 8.1 +/- 0.4 parts per thousand and delta(34)S = 2.9 +/- 0.8 parts per thousand), with less isotopic enrichment, were most likely from nonanadromous parents. Stable-isotope ratios varied with fork length; at Home Camp Pool, this relationship was thought to represent an "isotope dilution factor" as recently emerged juveniles assimilated new food from freshwater, grew, and masked the marine signatures of their maternal parents. This study suggests that stable-isotope ratios may be used to distinguish between sympatric anadromous and nonanadromous adult brook trout and their progeny as long as brook trout are collected before they dilute their maternal isotope signatures.

Elliott, J. E., I. E. Moul, et al. (1998). "Variable reproductive success of bald eagles on the British Columbia coast." Journal of Wildlife Management 62(2): 518-529.

To determine factors affecting productivity of bald eagles (Haliacctus leucocephalus) nesting near industrial sites in the Strait of Georgia, British Columbia, we compared their reproductive success to sites on the outer Pacific Coast. Mean production (fledged young per occupied territory) over the period 1992-95 was higher at sites in the Strait of Georgia, including the lower Fraser River Valley (1.2) and southeast Vancouver er Island (0.95), compared to subpopulations at putative reference areas at Clayoquot Sound (0.27) on the west coast of Vancouver Island and in northern Johnstone Strait (0.30: P < 0.001). Low breeding success was mainly the result of nest failure when no eggs were laid, or eggs were abandoned during incubation. Food supply apparently was the key factor limiting breeding success. Total lipids measured in nestling plasma samples varied among sites (P < 0.010), and there was a relation between mean plasma lipids and mean annual productivity (r(2) = 0.52, P = 0.043), suggesting that food was Limiting in areas of low productivity: even at successful nests. There were no differences in prey delivery rates to nests in the less productive Barkley Sound (0.56) compared to the more productive Fraser River Delta (1.1). There was, however, a difference in prey composition between the 2 sites (P < 0.001), with more small fish and few er birds and mammals brought to Barkley Sound nests. Mean hatching date was later at nests outside the Strait of Georgia but was not a determinant of productivity because we recorded the latest mean hatching date at Langara Island, a site of seasonal food abundance and fair productivity (0.61).

Fechhelm, R. G., R. E. Dillinger, et al. (1992). "Modeling of Insitu Temperature and Growth Relationships for Yearling Broad Whitefish in Prudhoe Bay, Alaska." Transactions of the American Fisheries Society 121(1): 1-12.

Daily length-frequency data were used to assess the effect of water temperature and salinity on the in situ summer growth of age-1 broad whitefish Coregonus nasus collected in the Sagavanirktok River delta in arctic Alaska. Summer growth patterns for the years 1982 and 1985-1989 were approximated as piecewise linear functions whose slopes were regressed against mean surface water temperature and salinity in the delta for each designated period. Multiple-regression analysis indicated that growth rate was significantly correlated with water temperature (P < 0.01) but not with salinity (P = 0.28). The growth-temperature relationship was described by both a linear and a polynomial function. Both functions were used to generate growth patterns for each of the six study years, based upon water temperature. The linear function modeled the 6 years of growth data with a mean absolute error of 2.1 mm (SD, 1.5 mm) and the polynomial function with a mean absolute error of 3.8 mm (SD, 3.0 mm). If independent verification proves the model to be applicable to other coastal regions of northern Alaska and Canada, the model would have direct application in assessing impacts of oil and gas development in the Arctic.

Fechhelm, R. G., W. B. Griffiths, et al. (1995). "Application of an in-Situ Growth-Model - Inferred Instance of Interspecific Trophic Competition between Anadromous Fishes of Prudhoe Bay, Alaska." Transactions of the American Fisheries Society 124(1): 55-69.

A previously described in situ growth model was used to predict the summer growth of age-1 and age-2 broad whitefish Coregonus nasus in the Sagavanirktok River delta near Prudhoe Bay, Alaska, during 1990-1992. Comparisons of observed versus predicted weekly growth increments over the entire 9-year study (1982 and 1985-1992) yielded r = 0.789 (N = 77; P < 0.01) for age-1 fish and r = 0.522 (N = 70; P < 0.01) for age-2 fish. Based on daily comparisons of observed versus predicted mean fork length, the model was able to predict growth in 1991 and 1992 with mean squared errors (MSE) of 3.0 and 1.8 mm for age-1 fish and 6.5 and 21.2 mm for age-2 fish. Results were similar to those previously described for 1982 and 1985-1989. The model failed noticeably in 1990 for age-1 fish (MSE = 48.6), and model fit for age-2 fish (MSE = 29.9) was the poorest of the 9 years examined. Poor model fit for both year-classes in 1990 was attributed to a divergence of observed from predicted growth; observed growth began lagging predicted growth about the third week of July. By the end of August, predicted mean length exceeded observed length by 13.6 mm for age-1 fish and 12.8 mm for age-2 fish. Data suggest that the divergence in growth began at the time of a massive immigration of least ciscoes C. sardinella into the delta. We speculate that the presence of least ciscoes may have overtaxed the trophic carrying capacity of the delta, thereby curtailing the growth of young broad whitefish.

Franzoi, P., R. Maccagnani, et al. (1993). "Life-Cycles and Feeding-Habits of Syngnathus-Taenionotus and S-Abaster (Pisces, Syngnathidae) in a Brackish Bay of the Po River Delta (Adriatic Sea)." Marine Ecology-Progress Series 97(1): 71-81.

We investigated the population structure, life cycles and gut contents of 2 species of pipefish, Syngnathus taenionotus and S. abaster, in a brackish embayment of the Po River Delta (North Adriatic Sea). These 2 species inhabit the nearshore environment of the bay where the sandy bottom is covered by macroalgae, and were sampled for 1 yr. The main differences in life history traits between S. taenionotus and S. abaster respecitvely can be summarized as follows: life span is about 24 vs 17 mo; reproductive season begins in February vs March, and lasts 5 vs 4 mo; average length of fingerlings at the time they hatch from the male brood pouch is 20.3 (+/- 1.2) vs 13.5 (+/- 1.0) mm; egg incubation period is 2 mo vs 1 mo; average number of ripe eggs per mature ovary is 46 (+/- 9) vs 104 (+/- 40); average number of embryos incubated by male is 84 (+/- 17) vs 109 (+/- 27). Finally, the sex ratio in the reproductive population is more male-biased in S. taenionotus than in S. abaster. The 2 species probably do not compete for food resources, remaining almost completely segregated in 2 different foraging micro-habitats during most of their life span. The new-born spring individuals of both species feed almost exclusively on harpacticoids of the genus Tisbe. As they mature, S. abaster continue to prey on phytal organisms while the larger S. taenionotus become zooplanktivorous.

Fu, J. M., B. X. Mai, et al. (2003). "Persistent organic pollutants in environment of the Pearl River Delta, China: an overview." Chemosphere 52(9): 1411-1422.

In the Pearl River Delta of China, the rapidly developing industrial and agricultural activities, municipal development and use of chemicals caused serious environmental problems. This report summarizes the published scientific data on POPs in the environment of the Pearl River Delta, including the levels of POPs in the air, water, soil, river and estuarine sediments, the marine organisms like fish and shellfish in this region. The data preliminarily reveal the state of contamination in this region and give insight into the fate of POPs in this sub-tropical area. However, most research in this area is limited to a few kinds of POP compounds. (C) 2003 Elsevier Ltd. All rights reserved.

Garcia, A. and I. Palomera (1996). "Anchovy early life history and its relation to its surrounding environment in the Western Mediterranean basin." Scientia Marina 60: 155-166.

This paper is a review on the anchovy early life history in the western Mediterranean. There is evidence of latitudinal differences in the duration of the spawning period associated with regional temperature variations. The main spawning areas of the anchovy are located in the Gulf of Lyons and at the shelf surrounding the Ebro river delta. The extensions of spawning grounds seem to be linked to the size of the shelf and to the degree of hydrographic enriching-process es. Punctual studies on egg and larval ecology have been made mainly in the areas of the main spawning grounds, reporting preliminary results on growth, feeding, condition and mortality estimates. Biomass estimation by the Daily Egg Production Method (DEPM) has also been applied at the northern region.

Garcia-Hernandez, J., E. P. Glenn, et al. (2000). "Bioaccumulation of selenium (Se) in the Cienega de Santa Clara wetland, Sonora, Mexico." Ecotoxicology and Environmental Safety 46(3): 298-304.

The Cienega de Santa Clara, on the east side of the Colorado River delta, is a brackish wetland supported by agricultural drainage water front the United States that provides habitat for endangered fish and bird species, Bioaccumulation of selenium has created toxicity problems for wildlife in similar wetlands in the United States. This is the first selenium survey in the Cienega de Santa Clara. Ten sites mere selected to collect water (dissolved), sediments (total), plants, invertebrates, and fish. Samples mere collected from October 1996 to March 1997, Selenium was detected in all samples. Concentrations in Rater ranged from 5 to 19 mu g/L and increased along a salinity gradient. Although water levels of selenium exceeded EPA criterion for protection of wildlife, Levels in sediments (0.8-1.8 mg/kg), aquatic plants (0.03-0.17 mg/kg), and fish (2.5-5.1 mg/kg whole body, dry wt) did not exceed USFWS recommended levels, It is concluded from this studs that the levels of selenium in water did not affect the overall health of the fish sampled. Therefore, it is important to maintain or improve the mater quality entering this wetland to continue to have normal levels of Se in the food chain components. (C) 2000 Academic Press.

Helfrich, L. A., C. R. Liston, et al. (2001). "Survival and injury of splittail and chinook salmon passed through a large hidrostal pump." North American Journal of Fisheries Management 21(3): 616-623.

The passage survival, descaling, and injury rates of marked splittail Pogonichthys macrolepidotus and juvenile chinook salmon Oncorhynchus tshawytscha that were inserted into the entrance (suction side) of a Hidrostal pump were compared with those of control fish inserted at the exit (pressure side) in 130 paired trials conducted from December 1998 to July 1999. The Hidrostal pump had no significant effect (P < 0.001) on immediate or latent (96-h) mortality, descaling, or body injury rates for all flow rates and sizes and densities of Fish tested, except for the 96-h mortality of splittail in June. The immediate survival rates for splittail and chinook salmon averaged 99%, and the cumulative (96-h) survival for these species averaged 93% and 96%, respectively. Average scale loss on splittail and chinook salmon usually was low (1.9% and 2.4%, respectively), and the frequency of injury to head, eyes, skin, and fins typically, as low and not significantly different among quality control, control, and treatment fish. Observations on wild fish (26 species; 7,197 fish) entrained from the Sacramento-San Joaquin River Delta during the Pumping trials indicated high immediate survival (99%). The Hidrostal pump transported a variety of sizes and numbers of native fishes with low mortality and injury rates over a range of pump velocities and environmental conditions. Hidrostal pumps that can safely transport fish screened from a water diversion canal through a bypass return to a river may have important fisheries management applications.

Hinojosa-Huerta, O., S. DeStefano, et al. (2002). "Evaluation of call-response surveys for monitoring breeding Yuma Clapper Rails (Rallus longirostris yumanensis)." Journal of Field Ornithology 73(2): 151-155.

During March-June 2000 we evaluated the use of call-response surveys to monitor breeding Yuma Clapper Rails (Rallus longirostris yumanensis) at the Cienega de Santa Clara, Colorado River Delta, Sonora, Mexico. We assessed the effect that time of day, stage of breeding season, and number of survey periods had on the average number of rails detected at a station. Conducting call-response surveys resulted in a significant increase in the number of detected rails and reduced the coefficient of variation of the average number or rails per station, which increases the statistical power to detect population trends. Using this technique also appears to reduce the variation of rates of responses by rails through the breeding season when compared to passive listening. There was no difference between the number of rails detected during morning and afternoon surveys. The established protocol developed by the U.S. Fish and Wildlife Service for Yuma Clapper Rail surveys is adequate for monitoring, and it should continue to be implemented on a yearly basis at the Cienega de Santa Clara and other wetlands of the Colorado River Delta in Mexico.

Hitchcock, G. L., W. J. Wiseman, et al. (1997). "Property fields in an effluent plume of the Mississippi river." Journal of Marine Systems 12(1-4): 109-126.

Surface property distributions were mapped in the Mississippi River plume during May and August, 1993 while following surface drifters. Prevailing winds were the primary factor controlling the orientation of the plume. In May, under typical southeasterly winds, the plume turned anticyclonically towards the coast, while in August, under anomalous westerly winds, the plume turned east. Remote imagery of sea surface temperature and suspended sediments confirmed the direction of the plume. Optimally interpolated maps of surface salinity, temperature, chlorophyll a fluorescence, and transmissivity from underway sampling, and periodic nutrient samples, reveal the plume structure. In May concentrations of nitrate, silicate, and phosphate decreased linearly with increasing salinity. Chlorophyll a increased to peak concentrations of 10 mu g l(-1) in the plume, although higher pigment biomass was observed near the coast. In August nitrate and silicate concentrations decreased conservatively near the mouth of SW Pass, except where pigment biomass was enhanced in a convergent surface front. Surface nutrient concentrations in the plume also decreased with increasing salinity. The observations provide the first Lagrangian view of surface property distributions in the Mississippi River plume, and indicate that significant temporal variability exists in physical and biological properties within a day after waters are discharged from the river delta. (C) 1997 Elsevier Science B.V.

Jassby, A. D. and J. E. Cloern (2000). "Organic matter sources and rehabilitation of the Sacramento-San Joaquin Delta (California, USA)." Aquatic Conservation-Marine and Freshwater Ecosystems 10(5): 323-352.

The Sacramento-San Joaquin River Delta, a complex mosaic of tidal Freshwater habitats in California. is the focus of a major ecosystem rehabilitation effort because of significant long-term changes in critical ecosystem functions. One of these functions is the production, transport and transformation of organic matter that constitutes the primary food supply, which may be sub-optimal at trophic levels supporting fish recruitment. A long historical data set is used to define the most important organic matter sources, the factors underlying their variability, and the implications of ecosystem rehabilitation actions for these sources. 2. Tributary-borne loading is the largest organic carbon source on an average annual Delta-wide basis; phytoplankton production and agricultural drainage are secondary; wastewater treatment plant discharge, tidal marsh drainage and possibly aquatic macrophyte production are tertiary; and benthic microalgal production, urban run-off and other sources are negligible. 3. Allochthonous dissolved organic carbon must be converted to particulate form-with losses due to hydraulic flushing and to heterotroph growth inefficiency-before it becomes available to the metazoan food web. When these losses are accounted for, phytoplankton production plays a much larger role than is evident from a simple accounting of bulk organic carbon sources, especially in seasons critical for larval development and recruitment success. Phytoplankton-derived organic matter is also an important component of particulate loading to the Delta. 4. The Delta is a net producer of organic matter in critically dry years but, because of water diversion from the Delta, transport of organic matter from the Delta to important, downstream nursery areas in San Francisco Bay is always less than transport into the Delta from upstream sources. 5. Of proposed rehabilitation measures, increased use of floodplains probably offers the biggest increase in organic matter sources. 6. An isolated diversion facility-channelling water from the Sacramento River around the Delta to the water projects-would result in substantial loading increases during winter and autumn, but little change in spring and summer when food availability probably matters most to developing organisms. 7. Flow and fish barriers in the channel could have significant effects, especially on phytoplankton sources and in dry years, by eliminating 'short-circuits' in the transport of organic matter to diversion points. 8. Finally, productivity of intentionally flooded islands probably would exceed that of adjacent channels because of lower turbidity and shallower mean depth, although vascular plants rather than phytoplankton could dominate if depths were too shallow. Copyright (C) 2000 John Wiley & Sons, Ltd.

Keyser, D., A. Khabibullayev, et al. (1999). "Research for rehabilitating the aral sea region." Nature & Resources 35(2): 26-37.

Aral Sea was once the fourth biggest lake in the world, with an area of 68,320 km(2), bat has now shrunk to barely half that size. From around 1957, the sea began to dry up as more and more water was directed to irrigate cotton and other thirsty crops. The sea used to receive 50-60 km(3) of water a year from its two main feeder rivers. By the mid-1980s, river flow into the sea had shrunk to 2-5 km3 a year. With the shrinking of the sea, salinity levels near tripled, many fish species disappeared and former fishing communities have become ghost communities. By studying the available literature, it is clear Chat such environmental effects were already foreseen during the planning of this major irrigation project in central Asia. The benefit for the economy of the region was tremendous in the first ten to fifteen years. But the planned relief for all the anticipated negative effects of the modifications were either not realized, or only slowly so. Through this shortfall between planning and realization, the situation in the broader Aral Sea region worsened, while it was still favourable in the newly developed irrigation areas. With the break-up of the former Soviet Union. the five newly independent central Asian republics of the Aral basin Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan - have been seeking to mobilize regional and international support for measures to rehabilitate degraded land and water resources in the basin. Among the scientific initiatives has been a three-year project of ecological monitoring and research in the river delta areas of the Aral, supported by the German Ministry of Education, Science, Research and Technology and coordinated by the University of Hamburg and UNESCO.

Khodorevskaya, R. P., G. F. Dovgopol, et al. (1997). "Present status of commercial stocks of sturgeons in the Caspian Sea basin." Environmental Biology of Fishes 48(1-4): 209-220.

Catches for the last 25 years are analyzed for beluga Huso huso, stellate sturgeon A. stellatus and Russian sturgeon Acipenser gueldenstaedtii, which are the three commercially important species of sturgeons found in the Caspian Sea Basin. Population sizes for generations born between 1961 and 1970 are estimated, and found to depend on natural reproduction and the number of young fish stocked annually from sturgeon hatcheries located in the Volga River Delta. A ban on sea fishing from 1962 to 1991 positively impacted the number and total biomass of commercial stocks. Sturgeon growth rates depend on water levels in the Caspian Sea. In order to preserve Caspian Sea sturgeon populations, it will be necessary to coordinate efforts of all countries surrounding the Caspian Sea to achieve rational harvests, preserve juveniles, and produce at least 100 million juveniles annually from hatcheries.

Leslie, J. K. and C. A. Timmins (1991). "Distribution and Abundance of Young Fish in Chenal Ecarte and Chematogen Channel in the St-Clair River Delta, Ontario." Hydrobiologia 219: 135-142.

Samples of fish larvae collected in 1983, 1984, and 1986 in two distributary channels of the St. Clair River delta were characteristically rich in species (a total of 48) and low in abundance (generally less than a mean of 5 100 m-3 of water filtered). Most species were residents of the delta; others apparently hatched in tributaries of the St. Clair River or in southern Lake Huron, and drifted into the delta. Highest species diversity was nearshore, although largest catches of larvae were of rainbow smelt, gizzard shad, and alewife, which were found mainly in mid-channel. Cyprinids (17 species) were better represented than other families.

Linhart, S. B., G. M. Baer, et al. (1997). "Acceptance of candidate baits by domestic dogs for delivery of oral rabies vaccines." Onderstepoort Journal of Veterinary Research 64(2): 115-124.

Protocols for evaluating oral rabies vaccine baits for domestic dogs were field tested in central Mexico, after which dog-food manufacturers and suppliers to the pet-food industry were advised as to potential ingredients for use in prototype dog baits. Bait-preference trials in which confined dogs were used were then undertaken, followed by field tests of free-ranging farmer-owned dogs in three towns in the Nile River Delta region of Egypt. Both confined and free-ranging dogs showed strong preferences for certain baits or bait coatings (poultry, beef tallow, cheese, egg and a proprietary product). Fish-meal polymer baits, widely used for wildlife species, were less preferred. In Egypt, a commercial dog-food-meal bait coated with beef tallow and dry cheese was consumed at a rate approaching that of a chicken-head bait. The percentage baits that were actually eaten after they had been offered to dogs, ranged from 71-96% for household dogs tested in Mexico, 65-91% for confined dogs (beagles and mixed breeds) tested in the United States, and 32-88% for farmer-owned dogs tested in Egypt.

Litvinov, A. G. and R. Ogorman (1996). "Biology of Amur sleeper (Perccottus glehni) in the delta of the Selenga River, Buryatia, Russia." Journal of Great Lakes Research 22(2): 370-378.

We determined the fecundity, growth, diet, and density of the Amur sleeper (Perccottus glehni) in the Selenga River Delta on Lake Baikal during 1986-1991 to better understand how this invading exotic will affect Baikal's endemic fishes. we also compared the Amur sleeper's diet with that of other fishes living in the delta. The largest Amur sleepers were about 200 mm long and weighed 200 g; the oldest were age 7. All females were mature at age 2. Fecundity ranged from 884 eggs at age 1 to 37,056 eggs at age 7. Highest densities of Amur sleepers were found in oxbow lakes where densities sometimes exceeded 4,000 fish per ha. The bulk of the diet of amur sleeper age 2 and older was chironomids, fish, an fish eggs. Chironomids were also important in the diet of the commercially valuable. Siberian roach (Rutilus rutilus lacustris) and Siberian dace (Leuciscus leuciscus baicalensis). Thus the Amur sleeper may cause population declines of these important endemic fishes through resource competition and predation on their juvenile life stages. However, Amur sleepers were the species of fish most frequently eaten by Eurasian perch (Perca fluviatilis) and northern pike (Esox lucius). So, maintaining vigorous populations of these two predators may well be an effective strategy for limiting the size of Amur sleeper populations.

Lloret, J., I. Palomera, et al. (2004). "Impact of freshwater input and wind on landings of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in shelf waters surrounding the Ebre (Ebro) River delta (north-western Mediterranean)." Fisheries Oceanography 13(2): 102-110.

Time series analyses (Box-Jenkins models) were used to study the influence of river runoff and wind mixing index on the productivity of the two most abundant species of small pelagic fish exploited in waters surrounding the Ebre (Ebro) River continental shelf (north-western Mediterranean): anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus). River flow and wind were selected because they are known to enhance fertilization and local planktonic production, thus being crucial for the survival of fish larvae. Time series of the two environmental variables and landings of the two species were analysed to extract the trend and seasonality. All series displayed important seasonal and interannual fluctuations. In the long term, landings of anchovy declined while those of sardine increased. At the seasonal scale, landings of anchovy peaked during spring/summer while those of sardine peaked during spring and autumn. Seasonality in landings of anchovy was stronger than in sardine. Concerning the environmental series, monthly average Ebre runoff showed a progressive decline from 1960 until the late 1980s, and the wind mixing index was highest during 1994-96. Within the annual cycle, the minimum river flow occurs from July to October and the wind mixing peaks in winter (December-April, excluding January). The results of the analyses showed a significant correlation between monthly landings of anchovy and freshwater input of the Ebre River during the spawning season of this species (April-August), with a time lag of 12 months. In contrast, monthly landings of sardine were significantly positively correlated with the wind mixing index during the spawning season of this species (November-March), with a lag of 18 months. The results provide evidence of the influence of riverine inputs and wind mixing on the productivity of small pelagic fish in the north-western Mediterranean. The time lags obtained in the relationships stress the importance of river runoff and wind mixing for the early stages of anchovy and sardine, respectively, and their impact on recruitment.

MacKenzie, R. A. and J. L. Kaster (2004). "Temporal and spatial patterns of insect emergence from a Lake Michigan coastal wetland." Wetlands 24(3): 688-700.

Emergence traps were used to sample insects along a transect through a river delta wetland on Green Bay, Lake Michigan in an attempt to document spatial and temporal patterns in insect emergence. Various abiotic factors were also measured to determine which factors influenced these dynamics. Significant decreasing gradients in dissolved oxygen and pH with distance from the river, coupled with trends in sum nitrate (nitrate + nitrite), revealed that riverine water was mixing with wetland water up to 100 m from the wetland-river interface. Annual emerging insect densities decreased exponentially with distance from the river while emerging insect biomass decreased linearly with distance, both of which were significant. Insects were largely comprised of Chironomidae, which represented 7-88% of the insects emerging. Loss of biomass was largely due to emergence of Aeshnidae (0-34%), Libellulidae (0-69%), Coenagrionidae (0-23%), Siphlonuridae (0-63%), and Chironomidae (1-25%). Major Chironomidae emergence events occurred from early spring until early summer and again from late summer to early fall. These events were likely an important source of energy needed for avian egg production, duckling growth, or migratory flights. Spatial and temporal patterns revealed the importance of wetland areas adjacent to the Peshtigo River to emerging insects, as well as to the transient organisms that use them as a. food source.

MacKenzie, R. A., J. L. Kaster, et al. (2004). "The ecological patterns of benthic invertebrates in a Great Lakes coastal wetland." Journal of Great Lakes Research 30(1): 58-69.

Benthic macroinvertebrates were sampled in the summer of 1997 using a standard D frame kick net along a transect across the Peshtigo wetland, a river delta wetland on the coast of Green Bay, Lake Michigan, to describe the spatial and temporal dynamics of the invertebrate community. Various abiotic factors, including sedimentation rates determined from Pb-210 and Cs-137 as a proxy for delivery of riverine organic matter, were also measured to determine which factors influenced these dynamics. Significant decreasing gradients in dissolved oxygen and pH with distance from the river, coupled with trends in sedimentation rates, chloride, and sum nitrate (nitrate + nitrite), revealed that riverine water was mixing with wetland water up to 100 in from the wetland-river interface. Aboveground primary production and total invertebrate densities exhibited Weibull type distributions, with highest rates and numbers occurring 20 to 100 in from the Peshtigo River. Invertebrate densities were largely represented by Asellus sp. isopods (12-53%) and exhibited highest numbers in September. Invertebrate diversity at the genus level linearly decreased with distance from the river based on the Simpson's index of diversity (r(2) = 0.60, p < 0.05) and the Shannon- Wiener function (r(2) = 0.73, p < 0.01). Patterns observed suggest that there is an "optimal" zone for benthic invertebrates in the Peshtigo wetland 20 to 60 m from the Peshtigo River that is protected from high-energy events (e.g., storms, boating) in the Peshtigo wetland by a buffer zone (0 to 20 in) but is close enough to benefit from replenished levels of dissolved oxygen, nutrients, and organic matter delivered via the Peshtigo River.

McCarthy, L. H., K. Robertson, et al. (1997). "Baseline studies in the Slave River, NWT, 1990-1994 .4. Evaluation of benthic invertebrate populations and stable isotope analyses." Science of the Total Environment 197(1-3): 111-125.

The Northwest Territories (NWT) portion of the Slave River is downstream of the Athabasca and Peace Rivers and the potential for contamination from industrial and agricultural processes from these sources and from long-range transport is very real. In response to this threat, the Slave River Environmental Quality Monitoring Program was established cooperatively between the government of the Northwest Territories and federal government agencies in 1991. A 5-year program was conducted to examine the quality of the water, suspended sediment, and fish in the territorial portion of the Slave River and to establish a baseline data set for comparison purposes in future monitoring programs. Additional facets of the study on the Slave River included an assessment of the benthic invertebrate population, since it was recognized that such a survey could be important for biomonitoring purposes. Abundance of organisms, taxon diversity, and presence or absence of sentinel species could all be used to assess environmental contamination. The final focus of the program was the examination of stable isotope ratios of carbon, sulphur, and nitrogen in the Slave River fish. Ecologically, these measurements can be used to determine the feeding and migration pattern of fish, and to define their trophic position in the food chain. From a toxicological Feint of view, these stable isotope ratios call help explain contaminant sources and transfer through the food chain. The benthic invertebrate survey was conducted in 1990 and 1991. The study concluded that the abundance of benthic invertebrates at the numerous sires examined in the Slave River was very low and organisms that had been used in other biomonitoring studies (e.g. bivalve molluscs, large oligochaetes) were rare or absent. Over 90% of the invertebrates collected from the Slave River were chironomids or small oligochaetes and comparisons of benthic invertebrate communities in the Slave River Delta indicated that few changes in percent composition or diversity had occurred over a 10-year period. The benthic invertebrate survey provided a baseline for future population analysis. Analysis of the stable isotope ratio of sulphur in fish from the Slave River indicated at least two significant food sources. One source is probably from Great Slave Lake, while the other is probably upstream of Fort Smith (Athabasca and Peace Rivers). Also, the stable isotope of carbon indicated that the food source is via different pathways and may include benthic as well as pelagic origins. It is difficult to make any conclusions regarding the organic concentrations found in fish tissues and their possible significance to isotope analysis, since the overall contaminant body burdens were generally very low or below analytical detection. (C) 1997 Elsevier Science B.V.

Meuleman, C., M. Leermakers, et al. (1995). "Mercury Speciation in Lake Baikal." Water Air and Soil Pollution 80(1-4): 539-551.

Research on mercury (Hg) distribution and speciation was carried out in Lake Baikal, a large, strong-oligotrophic freshwater reservoir in Siberia, Russia, during June 1992 and march 1993. In summer, total Hg in the water column ranged from 0.14 to 0.77 ng Hg/L, with the highest concentrations observed in the central basin of the lake in surface water samples. Labile inorganic Hg was found to be 7 to 20% of the total Hg content. Highest total Hg concentrations were found in river waters  :  up to 2 ng Hg/L. Labile methylmercury (MeHg) concentrations ranged from 2 to 38 pg Hg/L in the water column, with the higher concentrations in the central part of the lake, and showing a slight increase in near bottom waters. Labile MeHg makes up 1 to 15% of the total I-Ig content in the water column, with larger fractions in deep waters. The slight increase of the MeHg gradient with depth corresponds with the O-2 minimum region. Highest MeHg concentrations were observed in river waters (up to 145 pg Hg/L) and in some bays of the lake (up to 160 pg Hg/L). In these high temperature- and phytoplankton-rich water masses, the MeHg-fraction increased up to 35% of total Hg. Labile MeHg concentrations in water samples taken in winter in the southern basin (under the ice cover), showed slightly higher concentrations than in summer, possibly due to an early spring bloom. In rainwater, total Hg ranged from 3 to 20 ng Hg/L and MeHg from 0.1 to 0.25 ng Hg/L. In snow, a large fraction of total Hg is bound to particulate matter; concentrations of total Hg ranged from 8 to 60 ng Hg/L and labile MeHg from 0.1 to 0.25 ng Hg/L. Atmospheric Mg was found to be 0.73 to 2.31 ng/m(3) as gaseous Hg and 0.005 to 0.02 ng/m(3) in its particulate form. Spatial distribution patterns of atmospheric Hg show slightly higher to 0.02 ng/m concentrations over the central part of the lake and the Selenga river delta. In winter, atmospheric Hg values 3 (measured in the southern region), ranged from 1.2 to 6.1 ng/m(3) as total gaseous Hg and 0.02 to 0.09 ng/m(3) as total particulate Hg, and are higher than in summer, probably influenced by coal burning and traffic by the local population. MeHg contents in fish ranged from 20 ng Hg/g dry weight in small Cottocomephorus to 300 ng Hg/g dry weight in pike and trout species, which were caught in organic-rich waters.

Moffat, D. and O. Linden (1995). "Perception and reality: Assessing priorities for sustainable development in the Niger River Delta." Ambio 24(7-8): 527-538.

The Niger Delta is the richest part of Nigeria in terms of natural resources, The area has large oil and gas deposits, as well as extensive forests, good agricultural land and abundant fish resources. Despite the tremendous natural and human resource base, the region's potential for sustainable development remains unfulfilled and its future is being threatened by environmental degradation and deteriorating economic conditions which are not being addressed by present policies and actions. Twenty-five years of oil development have not brought significant benefits to the region. Resource-use decisions are being driven by a lack of development, poor health, stagnant agricultural productivity, very limited opportunities in urban areas, rapid population growth, and tenuous property rights. The article attempts to advance beyond the prevailing emotive arguments on the causes of environmental degradation by examining the full range of environmental issues to determine priorities and to suggest options for sustainable development within an integrated coastal zone management framework.

Moore, M. J., I. V. Mitrofanov, et al. (2003). "Cytochrome P4501A expression, chemical contaminants and histopathology in roach, goby and sturgeon and chemical contaminants in sediments from the Caspian Sea, Lake Balkhash and the Ily River Delta, Kazakhstan." Marine Pollution Bulletin 46(1): 107-119.

Roach, goby and sturgeon were examined for cytochrome P4501A (CYP1A) expression and histopathology, in relation to contaminant burdens in fish and sediment. Gradients of induction of CYP1A were observed. Roach from the Ural and Ily River Deltas and roach and goby from the two stations nearest the Caspian Sea oil fields displayed higher levels of CYP1A expression in several organs than was observed in fish from further offshore. Great sturgeon and Russian sturgeon showed higher levels of CYP1A expression than was seen in starred sturgeon and gobies in the Ural delta. No fish showed evidence of contaminant-related histopathologies in the organs examined, despite the elevated CYP1A levels. Low levels of polychlorinated biphenyls and elevated levels of inshore and riverine petroleum hydrocarbons from these habitats suggest that this ongoing hydrocarbon exposure, and that from natural sources and long-term oil exploration on the Northeastern Caspian shore, contributed to the CYP1A induction observed. (C) 2002 Elsevier Science Ltd. All rights reserved.

Ni, I. H. and K. Y. Kwok (1999). "Marine fish fauna in Hong Kong waters." Zoological Studies 38(2): 130-152.

Marine fish fauna in Hong Kong Waters. Zoological Studies 38(2). 130-152. Rapid industrialization and large-scale infrastructural projects in Hong Kong and the Pearl River Delta in recent years have placed an extraordinarily heavy burden on coastal environments. The magnitude of the problem will increase as sewage discharge, ocean dredging/disposal, and land reclamation continue to expand in the next few years. Fundamentals of marine environmental impact assessment are based upon a good understanding of biodiversity that allow us to monitor environmental changes. However, there is no baseline data on marine fauna that allow evaluation of the damage from various large-scale infrastructural projects to aquatic environments. A comprehensive database on local fish fauna is, therefore, urgently necessary for the planning and implementation of conservation strategies in Hong Kong. This paper is the ist systematic report on marine fish fauna in Hong Kong waters. From years of opportunistic fishing surveys and a thorough literature review, a total of 25 orders, 124 families, 390 genera, and 834 fish species in Hong Kong waters were identified. There are 97 fish species listed herein as new records to the area.

Nichols, S. J., G. Kennedy, et al. (2003). "Assessment of lake sturgeon (Acipenser fulvescens) spawning efforts in the lower St. Clair River, Michigan." Journal of Great Lakes Research 29(3): 383-391.

One of the most threatened remaining populations of lake sturgeon in the Great Lakes is found in the connecting channels between Lake Huron and Lake Erie. Only two spawning grounds are presently known to be active in this region, and both are in the St. Clair River. The spawning reef in the St. Clair River delta has been recently colonized by round gobies (Neogobius melanostomus) in densities up to 25/m(2), raising concerns regarding predation on the benthic-oriented eggs and larvae of the sturgeon. Investigations in 1998-1999 showed that while round goby predation does occur, a number of other factors may be equally affecting sturgeon spawning success, including few spawning adults (< 60), suspected poaching pressure, low retention rate of eggs on the reef low hatch rate (similar to0.5%), the presence of organic contaminants, and predation from native and exotic invertebrates and fish. Overall, we estimate that less than 1% of the eggs deposited during a spawning run survive to hatch. We were able to increase the egg hatch rate to 16% by placing eggs in predator-exclusion chambers on the reef. The fate of the larvae is uncertain. Two weeks after hatching, no larvae were found on the reef. We were unable to find them anywhere else in the river, nor was predation on larvae noted in either year. There were factors other than predation affecting larval survival in 1999. There was a higher silt load on the reef than in 1998 and large numbers of dead larvae were found. Recruitment success from this site could be improved by utilizing techniques to increase the number of eggs on the reef, such as reducing the illegal take of adult fish and by placing eggs in predator-exclusion chambers to increase hatch rate.

Nielsen, J. L., I. Williams, et al. (2003). "The importance of genetic verification for determination of Atlantic salmon in north Pacific waters." Journal of Fish Biology 62(4): 871-878.

Genetic analyses of two unknown but putative Atlantic salmon Salmo salar captured in the Copper River drainage, Alaska, demonstrated the need for validation of morphologically unusual fishes. Mitochondrial DNA sequences (control region and cytochrome b) and data from two nuclear genes [first internal transcribed spacer (ITS-1) sequence and growth hormone (GH1) amplification product] indicated that the fish caught in fresh water on the Martin River was a coho salmon Oncorhynchus kisutch, while the other fish caught in the intertidal zone of the Copper River delta near Grass Island was an Atlantic salmon. Determination of unusual or cryptic fish based on limited physical characteristics and expected seasonal spawning run timing will add to the controversy over farmed Atlantic salmon and their potential effects on native Pacific species. It is clear that determination of all putative collections of Atlantic salmon found in Pacific waters requires validation. Due to uncertainty of fish identification in the field using plastic morphometric characters, it is recommended that genetic analyses be part of the validation process. (C) 2003 The Fisheries Society of the British Isles.

Pampoulie, C., E. Rosecchi, et al. (1999). "Life history traits of Pomatoschistus minutus in the Rhone Delta, France." Journal of Fish Biology 55(4): 892-896.
Life history traits and migratory status of the Sand goby Pomatoschistus minutus were investigated in a brackish lagoon of the Rhone river Delta (Mediterranean Sea, south of France). (C) 1999 The Fisheries Society of the British Isles.

Papa, R., F. N. Marzano, et al. (2003). "Genetic diversity and adaptability of two species of Mugilidae (Teleostei  :  Perciformes) of the Po river delta coastal lagoons." Oceanologica Acta 26(1): 121-128.

Molecular polymorphisms (allozyme and amplified fragment length polymorphisms (AFLP)) were investigated in the mullet specie's Liza ramada and Liza saliens to determine levels of genetic variability and assess possible correlations between the population genetic structure and the specie's adaptability to shallow water environments. The thinlipped (L. ramada) and the sharpnose (L saliens) mullets are diadromous species-that enter coastal lagoons during early life stages to complete growth previous to sexual maturation. Bi-monthly samples (n = 30-50) were collected in the period 2000-2002 in different sites of the Sacca di Goro (Po river delta) and a nearby aquaculture lagoon (Valle Bertuzzi). Biochemical analyses were carried out by means of starch gel electrophoresis (SGE) on 24 genetic loci corresponding to 15 gene-enzyme systems. In addition, molecular species-specific AFLP (15 primer combinations) were obtained by means of capillary electrophoresis. The degree of allozyme variability determined at three polymorphic loci, GPI-A, GPI-B and G3PDH in L. saliens and L ramada (polymorphic loci P = 0.08; mean heterozygosity H = 0.010-0.022) and AFLP diversity (P = 0.110-0.430), seems lower than the one reported in the literature for ecologically similar teleost species. The identification of diagnostic alleles at GPI-A, G3PDH, AK-2, CK-A, CK-B, AAT, IDH, PGM-1, PGM-2 loci in the two mullet species was used for the taxonomic classification of L. saliens and L. ramada. Molecular taxonomy (allozyme and AFLP) demonstrated that the presence of small individuals inside the lagoons previously identified according to morphological characters has often been misinterpreted. The results are discussed in relation to the adaptive role of genetic variation and the migratory characteristics of Mugilidae. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/CNRS/IRD. All rights reserved.

Petreas, M. X., T. Wiesmuller, et al. (1992). "Aquatic Life as Biomonitors of Dioxin Furan and Coplanar Polychlorinated Biphenyl Contamination in the Sacramento-San-Joaquin River Delta." Chemosphere 25(4): 621-631.

A pilot study was designed to investigate the extent, magnitude and source of polychlorinated dibenzodioxin and furan (PCDD/F) and coplanar polychlorinated biphenyl (PCB) contamination using aquatic life as biomonitors. The study focused around a bleached pulp and paper mill operating, along with other industrial facilities, near the confluence of the Sacramento and San Joaquin rivers (Delta) in northern California. Four locations were selected for sampling: two upstream from the plant (one on each river), one in the vicinity of the plant and one downstream from the plant. Because of the salinity gradient of the riverine system, no single fish or bivalve species could be collected, but multiple comparisons were made instead. The target species were selected on the basis of their abundance and localized feeding range. Clams were transplanted in the three freshwater locations and retrieved two months later, while resident mussels were collected from the estuarine location. Surface sediment samples were collected from each location. Whole body fish samples were composited or analysed individually based on size. The samples were freeze-dried, cleaned by a modified Smith-Stalling procedure, and the coplanar PCBs and PCDD/Fs were isolated and analysed by HRGC/HRMS. Low levels of PCDD/Fs were found in all samples: 1-3 pg/g TEQ (wet wt) in fish; 1-5 pg/g I-TEQ (dry wt) in bivalves; and from 3-51 pg/g I-TEQ (dry wt) in sediments with variable PCB levels. With few exceptions, only 2,3,7,8-substituted PCDD/Fs were found in fish, whereas bivalves had both 2,3,7,8-substituted and non-2,3,7,8-substituted PCDD/Fs with relatively high levels of total TCDDs compared to total PeCDD or HxCDD. Sediments had a PCDD/F pattern consistent with pentachlorophenol contamination. Comparison of sediments and collocated bivalves did not indicate bioconcentration in PCDD/Fs, but it did reveal a tenfold increase in PCB #77 and #126. Within each sample type, the PCDD/F and PCB congener profiles were consistent across species and locations. Shifts in congener profiles from sediments to bivalves to fish were consistent across locations. From the available data, the influence of the pulp mill, if any, could not be distinguished from the other sources in the region.

Poizat, G., E. Rosecchi, et al. (1999). "Empirical evidence of a trade-off between reproductive effort and expectation of future reproduction in female three-spined sticklebacks." Proceedings of the Royal Society of London Series B-Biological Sciences 266(1428): 1543-1548.

Optimal life-history models generally predict that the reproductive effort of iteroparous organisms may increase with age, as their expectation of future reproduction decreases. The population of three-spined sticklebacks (Gasterosteus aculeatus) in the Camargue (Rhone River Delta, France) is annual, all adults dying after their first breeding season. As the three-spined stickleback is a multiple spawner, we tested the hypothesis that reproductive effort ma): increase during the breeding season on field data. From 1987 to 1998, 653 female sticklebacks were collected in the field during the breeding seasons. The body size, body weight and weights of the liver, gonads and carcass were measured for these individuals. Only gravid females with mature eggs (176 fish) were included in the analysis. Considering the female three-spined stickleback as a capital breeder, the energetic resources available for allocation between soma and gonads were estimated by its body weight. Somatic condition decreased during the breeding season and reproductive effort (gonad weight relative to body weight) increased. These patter ns did not vary significantly between years. These observed variations in reproductive effort during the breeding season can be interpreted as empirical evidence of a trade-off between reproductive effort and expectation of future reproduction.

Poizat, G., E. Rosecchi, et al. (2004). "Long-term fish and macro-crustacean community variation in a Mediterranean lagoon." Estuarine Coastal and Shelf Science 59(4): 615-624.

The fish and macro-crustacean community of the Vaccares lagoon (Rhone River delta, South France) was sampled monthly from 1993 to 2002. The lagoon salinity shifted from 15 in 1993 to 5 in 1994-1997 and went back to 15 in 1999-2002. Connections with the sea also varied during the study period with larger openings in 1996-1997. During the study period, the community changed to revert in 2002 to a state similar to 1993. These changes consisted of a sequence of increased and decreased patterns of freshwater species and some marine species. Typical lagoon species tended to resist to salinity changes. Freshwater species colonised the lagoon when the salinity was low. Marine species may have varied both in relation to connections with the sea and to indirect effects of freshwater outflow. This study shows that community changes following environmental variations can be delayed in time, and emphasises the need for long-term studies. (C) 2003 Elsevier Ltd. All rights reserved.

Poulet, N., P. Berrebi, et al. (2004). "Genetic and morphometric variations in the pikeperch (Sander lucioperca L.) of a fragmented delta." Archiv Fur Hydrobiologie 159(4): 531-554.

Agricultural development modified the connectivity of the Rhone River delta waterbodies (also called the Camargue) which is now isolated from the Rhone River by dikes. Furthermore, the hydrographic network of the Camargue is constituted of irrigation and drainage canals, which are not directly connected. Pikeperch (Sander lucioperca L.), an allochthonous freshwater species, colonised the Rhone and the Camargue more than 50 years ago. We used morphometric and meristic features, otolith shape descriptors and protein electrophoresis in order to assess whether the Camargue houses one or several pikeperch populations. All characters except the meristic counts highlighted the existence of two subpopulations: one in the drainage network and one in the irrigation network. Electrophoresis showed that the irrigation network population is closer to the Rhone population and that the drainage network population displayed a high inbreeding rate. The causes of such isolation and the implications for the pikeperch population dynamics are discussed.

Powers, S. P., M. A. Bishop, et al. (2002). "Intertidal benthic resources of the Copper River Delta, Alaska, USA." Journal of Sea Research 47(1): 13-23.

The Copper River Delta, Alaska is the largest contiguous coastal wetland system along the West Coast of North America. Vast expanses of tidal mud flats formed by sediments carried by the suspended load of the Copper River serve as a connection between the Gulf of Alaska and the extensive network of wetlands, rivers and sloughs of the delta system. In addition to providing habitat for resident fish, shrimp and crabs, these tidal flats serve as critical feeding grounds for up to 5 million migratory shorebirds as well as an entry and exit corridor for three species of commercially fished salmonids, Here we report the first description of the benthic community of these inter-tidal flats. Between April and September 2000, we conducted three samplings on the Copper River Delta in which we quantified benthic macro-invertebrates inhabiting silt-clay sediments, the dominant substrate in the system, over a range of tidal inundation. Specifically, sampling was performed in two areas on the delta: near the outflows of the Eyak River and Pete Dahl Slough. Pore-water salinity of surficial sediment ranged from 4 psu during peak summer flow of the Copper River to 14 psu in April prior to increased riverine input. Sediment temperatures corresponded to ambient air temperatures with lowest temperatures during the April-September observation period recorded in April (4degreesC) and warmest in August (16degreesC). The benthic community of the delta's tidal flats was characterised by low species diversity and was dominated by the tellinid bivalve Maconia balthica, which reached densities greater than 4000 m(-2). Age-length relationship of M balthica indicated slow growth and longevity of up to 8 years. Polychaete densities, primarily the phyllodocid,Eteone longa, were low throughout the study period, reaching a maximum of only 700 m(-2) in August. Amphipod densities, primarily the corophid amphipod Corophium salmonis, were high (up to 7000 m(-2)) only during the August sampling. Spatial patterns of benthic invertebrate abundance were best explained by differences in tidal inundation with longer inundation corresponding to greater invertebrate densities. Temporal changes in abundance of polychaetes, amphipods, and M balthica recruits corresponded to increases in sediment temperatures. Natural or human-induced changes to M. balthica populations could impact the food web of the delta, which could cascade to larger geographic impacts because of the importance of the delta to migratory species. (C) 2002 Elsevier Science B.V. All rights reserved.

Rabalais, N. N., R. E. Turner, et al. (2002). "Gulf of Mexico hypoxia, aka "The dead zone"." Annual Review of Ecology and Systematics 33: 235-263.

The second largest zone of coastal hypoxia (oxygen-depleted waters) in the world is found on the northern Gulf of Mexico continental shelf adjacent to the outflows of the Mississippi and Atchafalaya Rivers. The combination of high freshwater discharge, wind mixing, regional circulation, and summer warming controls the strength of stratification that goes through a well-defined seasonal cycle. The physical structure of the water column and high nutrient loads that enhance primary production lead to an annual formation of the hypoxic water mass that is dominant from spring through late summer. Paleoindicators in dated sediment cores indicate that hypoxic conditions likely began to appear around the turn of the last century and became more severe since the 1950s as the nitrate flux from the Mississippi River to the Gulf of Mexico tripled. Whereas increased nutrients enhance the production of some organisms, others are eliminated from water masses (they either emigrate from the area or die) where the oxygen level falls below 2 mg l(-1) or lower for a prolonged period. A hypoxia-stressed benthos is typified by short-lived, smaller surface deposit-feeding polychaetes and the absence of marine invertebrates such as pericaridean crustaceans, bivalves, gastropods, and ophiuroids. The changes in benthic communities, along with the low dissolved oxygen, result in altered sediment structure and sediment biogeochemical cycles. Important fisheries are variably affected by increased or decreased food supplies, mortality, forced migration, reduction in suitable habitat, increased susceptibility to predation, and disruption of life cycles.

Ramirez, C. S. and M. Rueda (1999). "Diversity and abundance variation of dominant fish species in the river Magdalena delta, Colombia." Revista De Biologia Tropical 47(4): 1067-1079.

The fish community in the Magdalena River Delta, Colombia, was studied to assess relationship with habitats and to generate additional information for resource evaluation and management programs. Monthly castnets fish collections (1995 - 1996) were made in Cienaga Grande de Santa Marta (CGSM), Complejo Pajaral (CP) and Complejo Salamanca Occidental (CSO), all in the Magdalena River Delta; 36 species are present in CGSM, 24 in CP and 42 in CSO, with 11 species common to the three areas. Abundance and catch-per-unit effort were greater in the rainy season, when food availability was greater. The diversity varied during the study period and was higher in CSO where the environmental conditions were better. The geomorphology and environmental conditions determine the habitat adaptation of the species in the Delta. The dominant species have adapted their spawning, nursery and feeding functions to a yearly salinity pattern.

Restrepo, J. D. and B. Kjerfve (2002). "The San Juan delta, Colombia: tides, circulations, and salt dispersion." Continental Shelf Research 22(8): 1249-1267.

The San Juan River delta (Colombia) with ail area of 800 km 2 is the largest delta environment oil the Pacific coast of South America. It consists of active distribtaries maintained by an average discharge of 2500 m(3) s(-1), is tide dominated, and has relatively narrow estuarine mixing zones <17 km wide and typically similar to7 kill wide. Water level and current time series in two distributary months indicate that the tide is semidiurnal with a form number 0.1-0.2 and a mean range of 3 m. Processes at tidal frequencies explain 75-95% of the water level variability with the remaining low-frequency variability attributed to meteorological forcing and river processes. The tidal phase for the main diurnal and semidiurnal Constituents progress from north to south along the coast. Only the Southernmost distributary experiences significant tidal asymmetry as a result of strong river discharge and shallow depths. In the northernmost distributary, shallow water constituents are insignificant. Tidal currents were more semidiurnal than file water level. with form number 0.09-0.13. Tidal ellipses indicated that currents were aligned with the channels and mean amplitudes < 1 m s(-1) the delta distributaries, circulation modes varied from seaward flow at all depths during intermediate runoff conditions to gravitational circulation during rising and high discharge periods. In San Juan and Chavica distributaries, the Currents were ebb-directed, while in Charambira they were flood-directed. The circulation appears to be controlled by the morphology of the distributaries, which were weakly stratified and only sometimes moderately stratified. The net salt transport was directed seaward in San Juan and Charambira, and landward at Chavica, indicating an imbalance ill the salt budget, and signifying non-steady state behavior. The net longitudinal salt flux in the San Juan delta is largely a balance between ebb-directed advective flux, and flood-directed tidal sloshing. Along the distributary channels, fringing vegetation is controlled by freshwater discharge, longitudinal distribution of salinity, and morphology. In the most active distributaries, Chavica and San Juan, the vegetation setting is strongly shaped by the short estuarine zone, and mangroves only occur 5km upstream of any distributary mouth, whereas in the tide-dominated distributaries, Charambira and Cacahual, dense mangroves intrude 14 and 17 km upstream. respectively. Also, salt dispersion, tidal intrusion, salinity distribution, and mangrove extent in the San Juan delta agree qualitatively With the productive coastal fishery at the tide-dominated distributaries. (C) 2002 Elsevier Science Ltd. All rights reserved.

Reyes, E., M. L. White, et al. (2000). "Landscape modeling of coastal habitat change in the Mississippi delta." Ecology 81(8): 2331-2349

A landscape model was developed to investigate and predict the environmental factors affecting wetland habitat change within the Barataria and Terrebonne basins of coastal Louisiana, USA. The model linked an overland-flooding hydrodynamic module, using cells of 100 km(2) in size and operating at a 1-h time step, and a spatially articulated ecosystem module, resolving habitat type and change for 1-km(2) cells in daily time steps. Integration across different temporal and spatial scales was accomplished with interpolation routines and averaging algorithms. Forcing functions included dominant regional processes, such as subsidence, sedimentation, and sea-level rise. Hydrologic functions were calibrated against existing climate and hydrologic time series, while habitat information was compared to maps prepared by the United States Fish and Wildlife Service (USFWS) for 1978 and 1988. Spatial calibration was done by initializing the landscape pattern of the model to a 1978 USFWS habitat map. After a 10-yr simulation, the results were compared against a 1988 USFWS habitat map. Simulated maps had an accuracy of 85-90 (out of a maximum of 100), based on a multiple resolution fit algorithm. For validation the model was initialized with a 1956 USFWS habitat map, and the results from a 32-yr simulation were compared to the 1988 USFWS habitat map. The landscape model produced reasonable regional agreement, despite the fact that small-scale processes and features were not included. The validation runs produced land-loss rates that matched historical trends with an accuracy fit above 75. The model simulated 30 years into the future, starting in 1988, testing for long-term climate variability under diverse scenarios. Results indicated that weather variability impacts land-loss rates more than replication of extreme weather years. Even when extreme dry and wet years were repeated, the model predicted lower land loss when compared to historical records. This is indicative of the ability of the simulated plant communities to adapt to repetitive climatic forcing functions.

Risnoveanu, G. and A. Vadineanu (2003). "Long term functional changes within the Oligochaeta communities within the Danube river delta, Romania." Hydrobiologia 506(1-3): 399-405.

Within the Danube River delta's lakes the Oligochaeta communities comprise between 7.9% and 36.2% of the total biomass of benthic fauna. Their importance in energy flow at the ecosystem level changed in relation to fast trophic transition of all shallow lakes to the hypertrophic state. The parameters of the energy budget of the dominant populations and the potential production of benthivorous fish species assessed during 1976-1994 interval support this conclusion. P/B ratio, K-1 and K-2 coefficients assessed for both the 1976-1980 and 1991-1994 intervals revealed different functional patterns of response of Potamothrix hammoniensis (Michaelsen, 1901) and Limnodrilus hoffmeisteri (Claparede, 1862) to varying trophic conditions. Changes in communities structure, size of the constituent populations and their age distribution, as well as the quantity and quality of food supply and level of hypoxia at the sediment/water interface were the main factors that affected the role of these populations as energy carrier from the huge energy pool represented by sedimented organic carbon to benthivorous fish species.

Rojas-Bracho, L. and B. L. Taylor (1999). "Risk factors affecting the vaquita (Phocoena sinus)." Marine Mammal Science 15(4): 974-989.

Despite the vaquita being commonly cited as one of the most endangered marine mammals in the world, there is still disagreement over which factors put the species at greatest risk of extinction. This lack of agreement hinders management decisions needed to reduce the risk to the species. To expedite decision-making we consider four major risk factors. Habitat alteration from reduced flow of the Colorado River does not currently appear to be a risk factor because productivity remains high in vaquita habitat. Pollutant loads are low and pose low to no risk. Reduced fitness from inbreeding depression and loss of genetic variability are unlikely to pose high risk currently, though risk will increase if vaquitas remain at low abundance over long periods of time. Mortality resulting from fisheries bycatch poses high risk. Thus, short term management should not be hindered by uncertainty in estimating the risk of these factors, and primary conservation efforts should be directed towards immediate elimination of incidental fishery mortality.

Ronnback, P., M. Troell, et al. (2003). "Mangrove dependence and socio-economic concerns in shrimp hatcheries of Andhra Pradesh, India." Environmental Conservation 30(4): 344-352.

There are many environmental and socio-economic concerns about the shrimp aquaculture industry. This study, based on interviews, direct observations and literature reviews, shows that the Indian hatchery industry is heavily dependent upon the continuous support of natural resources and ecosystem services generated by marine, freshwater and terrestrial ecosystems. The mangrove ecosystem support area ('ecological footprint') needed to supply the hatcheries with Penaeus monodon shrimp broodstock, and the aquaculture grow-out ponds with postlarvae, exemplify the dependence on external ecosystems. Each hectare of mangrove in the Godavari River delta generated an annual fisheries catch of 0.8-1.5 P. monodon spawners (gravid females), valued at US$ 92-184. The entire Godavari mangrove delta had a partial gross economic value of US$ 3.0-6.0 million per year for the provision of shrimp spawners alone. The average hatchery, producing 75 million postlarvae annually, had an ecological footprint of 534 ha mangrove for the life-support input of shrimp spawners. The ecological footprint of intensive shrimp ponds was up to 11 times the pond area for postlarval input alone. The shrimp ponds in the State of Andhra Pradesh needed 35000-138000 ha of mangroves to satisfy the spawner requirement to hatcheries, and this implied a need to appropriate mangroves in other regions. Hatcheries were prepared to pay up to US$ 2000 for a single shrimp spawner, which also illustrated that the mangrove support areas regionally available were too small. Other concerns about the industry are the net loss of employment if hatcheries replace wild postlarvae collection, the extensive use of groundwater creating direct resource-use conflicts, by-catch problems in broodstock fisheries, and pollution by effluents. The risk of hatcheries introducing, amplifying and propagating disease affecting both cultured organisms and wild biota is another concern that can, and should, be addressed.

Rosecchi, E. and A. J. Crivelli (1995). "Sand Smelt (Atherina-Boyeri) Migration within the Water-System of the Camargue, Southern Prance." Hydrobiologia 301: 289-298.

In the coastal lagoons of Southern France, sand smelt Atherina boyeri, is known as a sedentary species. However part of the sand smelt population living in the brackish water Vaccares lagoon in the Camargue annually migrates to fresh waters. The movements of sand smelts within the watersystem of the Camargue were studied from 1986 to 1990. Fish traps and fyke nets were set and catches were standardised to Catch Per Unit Effort (CPUE). A Stepwise Multiple Correlation analysis was carried out to link fish abundance with various environmental factors. Between September and November, sand smelts living in the Vaccares start to colonize fresh waters (drainage canals and then temporary marshes), until March. Spawning occurs from April to June, both in the shallow branches of the canal and in the marshes. From June onwards adults and young-of-the year leave the fresh waters and return to the Vaccares lagoon where they remain until the next migration. This autumnal migration to freshwater habitats involves mainly fish less than 3 years old, the oldest individuals remaining all year in the Vaccares. Water level and photoperiod contribute to 20.7% of the variation of CPUE within the drainage canal, while date, water temperature, and rainfall combined, only account for 2.5% of CPUE variations. Date and photoperiod contribute significantly to explaining the patterns of fish migrations between the canal and the marshes. The density of mature sand smelt in the marshes before spawning, varies between 4 and 4346 fish ha(-1). Fry mortality (against number of eggs spawned) over the first two months of life was assessed to vary between 97.5% and 99.9%. Physiological factors such as osmoregulation linked to water temperature are possibly the ultimate factors explaining these unusual annual migrations of sand smelt in the Camargue.

Salmon, D. K. (1997). "Lessons in political oceanography part I: A preliminary analysis of whether an oil spill off Cape Hinchinbrook, Alaska could (or would) directly impact the Copper River Delta." Spill Science & Technology Bulletin 4(3): 141-146.

Historical data and information collected during recent and ongoing oceanographic investigations of Prince William Sound, Alaska and adjacent coastal waters, are used for a preliminary analysis of the possibility of an oil spill at the southern end of Prince William Sound directly impacting the Copper River Delta (CRD). The CRD is an economically and ecologically important region located a few kilometers to the east of Prince William Sound. The prevailing winds and ocean currents both in the coastal and offshore regions of the northern Gulf of Alaska move toward the west, indicating that a spill off of Cape Hinchinbrook would be likely to be advected westward away from the CRD, thereby having no impact on the waters of the CRD. However, eastward excursions of the Alaska Coastal Current occur, in which case there is a possibility that a spill off of Cape Hinchinbrook would be advected into the waters of the CRD region. Eastward components of the flow field within the coastal current have been frequently observed during spring, summer and fall, periods that are often characterized by westerly wind events that interrupt the prevailing easterly sind field and westward setting current. These reversals appear to be quite persistent and may have alongshore length scales from about 10 to 100 km. Although these wind and current reversals are common knowledge amonst boat captains and commercial fisherman in the region, their input to government agencies has largely been disregarded because their observations are anecdotal information. However, the combination of empirical scientific evidence (ocean current structure) and anecdotal information (which is actually also empirical) provide a powerful argument, attesting to the importance of these reversals as possible transport mechanisms for the advection of oil into the CRD region. This preliminary analysis is partly responsible for the Alaska Department of Environmental Conservation mandating a trajectory study in which the spill scenario off to Cape Hinchinbrook is analyzed in greater detail. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Scribner, K. T., M. R. Petersen, et al. (2001). "Sex-biased gene flow in spectacled eiders (anatidae): Inferences from molecular markers with contrasting modes of inheritance." Evolution 55(10): 2105-2115.

Genetic markers that differ in mode of inheritance and rate of evolution (a sex-linked Z-specific microsatellite locus, five biparentally inherited microsatellite loci, and maternally inherited mitochondrial [mtDNA] sequences) were used to evaluate the degree of spatial genetic structuring at macro- and microgeographic scales, among breeding regions and local nesting populations within each region, respectively, for a migratory sea duck species, the spectacled eider (Somateria fisheri). Disjunct and declining breeding populations coupled with sex-specific differences in seasonal migratory patterns and life history provide a series of hypotheses regarding rates and directionality of gene flow among breeding populations from the Indigirka River Delta, Russia, and the North Slope and Yukon-Kuskokwim Delta, Alaska. The degree of differentiation in mtDNA haplotype frequency among breeding regions and populations within regions was high (phi (CT) = 0.189, P < 0.01; phi (SC) = 0.059, P < 0.01, respectively). Eleven of 17 mtDNA haplotypes were restricted to a single breeding region. Genetic differences among regions were considerably lower for nuclear DNA loci (sex-linked: phi (ST) = 0.001, P > 0.05; biparentally inherited micro satellites: mean theta = 0.001, P > 0.05) than was observed for mtDNA. Using models explicitly designed for uniparental and biparentally inherited genes, estimates of spatial divergence based on nuclear and mtDNA data together with elements of the species' breeding ecology were used to estimate effective population size and degree of male and female gene flow. Differences in the magnitude and spatial patterns of gene correlations for maternally inherited and nuclear genes revealed that females exhibit greater natal philopatry than do males. Estimates of generational female and male rates of gene flow among breeding regions differed markedly (3.67 X 10(-4) and 1.28 X 10(-2), respectively). Effective population size for mtDNA was estimated to be at least three times lower than that for biparental genes (30,671 and 101,528, respectively). Large disparities in population sizes among breeding areas greatly reduces the proportion of total genetic variance captured by dispersal, which may accelerate rates of inbreeding (i.e., promote higher coancestries) within populations due to nonrandom pairing of males with females from the same breeding population.

So, M. K., S. Taniyasu, et al. (2004). "Perfluorinated compounds in coastal waters of Hong Kong, South China, and Korea." Environmental Science & Technology 38(15): 4056-4063.

Perfluorinated compounds (PFCs), such as perfluorooctanesulfonate (PFOS) and related compounds, have recently been identified in the environment. PFOS, the terminal degradation product of many of the PFCs, has been found globally in many wildlife species, as well as open ocean waters, even in remote regions far from sources. In this study, a solid-phase extraction procedure coupled with high-performance liquid chromatography interfaced to high-resolution mass spectrometry was used to isolate, identify, and quantify small concentrations of PFCs in seawater. These techniques were applied to investigate the local sources of PFCs in several industrialized areas of Asia and provide information on how the PFCs are circulated by coastal currents. Ranges of concentrations of PFOS in coastal seawaters of Hong Kong, the Pearl River Delta, including the South China Sea, and Korea were 0.09-3.1, 0.02-12, and 0.04-730 pg/mL, respectively, while those of perfluorooctanoic acid (PFOA) were 0.73-5.5, 0.24-16, and 0.24-320 pg/mL, respectively. Potential sources of PFCs include major industrialized areas along the Pearl River Delta of southern China and major cities of Korea, which are several of the fastest growing industrial and economic regions in the world. Detectable concentrations of PFOS and PFOA in waters of southern China were similar to those in the coastal marine environment of Japan and certain regions in Korea. Concentrations of PFCs in several locations in Korean waters were 10-100-fold greater than those in the other locations on which we report here. The spatial and seasonal variations in PFC concentrations in surface seawaters in the Pearl River Delta and South China Sea indicate the strong influence of the Pearl River discharge on the magnitude and extent of PFC contamination in southern China. All of the concentrations of PFOS were less than those that would be expected to cause adverse effects to aquatic organisms or their predators except for one location in Korea adjacent to an industrialized area. Hazard quotients were from <0.001 to 0.002 for aquatic animals and ranged from <0.001 to 17 for predatory birds.

Sobczak, W. V., J. E. Cloern, et al. (2002). "Bioavailability of organic matter in a highly disturbed estuary: The role of detrital and algal resources." Proceedings of the National Academy of Sciences of the United States of America 99(12): 8101-8105.

The importance of algal and detrital food supplies to the planktonic food web of a highly disturbed, estuarine ecosystem was evaluated in response to declining zooplankton and fish populations. We assessed organic matter bioavailability among a diversity of habitats and hydrologic inputs over 2 years in San Francisco Estuary's Sacramento-San Joaquin River Delta. Results show that bioavailable dissolved organic carbon from external riverine sources supports a large component of ecosystem metabolism. However, bioavailable particulate organic carbon derived primarily from internal phytoplankton production is the dominant food supply to the planktonic food web. The relative importance of phytoplankton as a food source is surprising because phytoplankton production is a small component of the ecosystem's organic-matter mass balance. Our results indicate that management plans aimed at modifying the supply of organic matter to riverine, estuarine, and coastal food webs need to incorporate the potentially wide nutritional range represented by different organic matter sources.

Sorokin, Y. I., P. Y. Sorokin, et al. (1996). "On an extremely dense bloom of the dinoflagellate Alexandrium tamarense in lagoons of the Po river delta: Impact on the environment." Journal of Sea Research 35(4): 251-255.

An extremely dense bloom of the potentially toxic dinoflagellate Alexandrium tamarense was observed in the lagoons of Ca Pisani (Veneto, Italy) in summer 1993. The lagoons were experiencing a significant eutrophication impact, receiving waste waters from intensive fish culture plants. During their bloom dinoflagellates in the lagoons reached densities of 2 to 4 x 10(6) cells . dm(-3) and a biomass of over 100 g . m(-3). The bloom produced drastic ecological changes in the lagoons. It caused nocturnal anoxia, mortality of macrophytes and the build-up of labile organic matter in the water column. Grazing by the tintinnid Favella sp. contributed to the termination of the bloom of the flagellates. The results show that coastal aqua culture probably stimulates dinoflagellate blooms in shallow brackish lagoons.

Sorokin, Y. I., P. Y. Sorokin, et al. (1999). "Analysis of lagoonal ecosystems in the Po River delta associated with intensive aquaculture." Estuarine Coastal and Shelf Science 48(3): 325-341.

Observations on structure and functioning of coastal lagoon ecosystems experiencing a high level of eutrophication impact were accomplished in three lagoons of Ca'Pisani integrated within an experimental aquaculture enterprise variously fertilized by waste effluents discharged from and intensive fish culture plant. During August and early September an extremely dense bloom of dinoflagellate Alexandrium tamarense was recorded in these lagoons with the density of phytoplankton up to 190 g m(-3) of wet biomass, and primary production 2 to 6 mg Cl-1 day(-1). The diel dissolved oxygen fluctuations in water column during the bloom reached 15-20 mg O-2 l(-1). The wet biomass of bacterioplankton in the lagoons attained 5-9 g m(-3). The microzooplankton was dominated by ciliates with biomass 1 to 19 g m(-3). The daytime mesozooplankton was dominated by calanoid copepods with a biomass 0.05-0.25 g m(-3), while the biomass of the demersal zooplankton at night attained 2 to 14 gm(-3). In the lagoon of Ocaro, the phototrophic plankton was dominated by the symbiotic ciliate Mesodinium. The labile sulphides content in the upper layer of the bottom attained over 190 g dm(-3) of wet silt. The rate of microbial sulphate reduction was 5-10 mg S dm(-3) day(-1). The data are generalized within the energy balance in these specific anthropogenically transformed pelagic communities. (C) 1999 Academic Press.

Vizzini, S. and A. Mazzola (2003). "Seasonal variations in the stable carbon and nitrogen isotope ratios (C-13/C-12 and N-15/N-14) of primary producers and consumers in a western Mediterranean coastal lagoon." Marine Biology 142(5): 1009-1018.

Stable carbon and nitrogen isotope ratios (C-13/C-12 and N-15/N-14) of primary producers and consumers were investigated seasonally throughout 1999, in order to describe the food web in a western Mediterranean coastal lagoon (Lake of Sabaudia, central Italy). Particulate organic matter and algal material (seagrass epiphytes and macroalgae) seem to constitute the main food sources for primary consumers (zooplankton and small benthic invertebrates, respectively) throughout the sampling year, while the seagrass Cymodocea nodosa appears to play a negligible trophic role. As regards the ichthyofauna, carbon stable isotopes differentiated between planktivore and benthivore fish species. However, a benthic-pelagic coupling seems to occur, with some fish of higher trophic levels feeding both on benthic and pelagic materials. Analysis of variance showed that the interaction between the three main factors (speciesxsizexseason) significantly affects the isotopic composition of fish, suggesting the presence of intra- and inter-specific resource partitioning. Wide seasonal variations in the isotopic composition were observed in organic matter sources, invertebrates and fish, with a general trend towards depleted values in winter and enriched values in summer. The winter depletion of organic matter sources may be due to several environmental factors and seems to be mirrored in the upper trophic levels. Primary producers and invertebrates are known to have shorter time-integrated isotopic signatures than vertebrates, yet fish also exhibited seasonal isotopic differences. We concluded that the examined fish species can assume a new muscle isotopic signature relatively quickly in response to changes in the isotopic composition of their diet and/or diet shifts.

Wilson, R., S. Allengil, et al. (1995). "Organochlorine Contaminants in Fish from an Arctic Lake in Alaska, USA." Science of the Total Environment 161: 511-519.

A wide range of organochlorine pesticides and polychlorinated biphenyls (PCBs) were measured in muscle tissue and livers of lake trout (Salvelinus namaycush) and Arctic grayling (Thymallus arcticus) from Schrader Lake in Arctic Alaska. Results confirm the long-range transport of these contaminants to a US Arctic freshwater system. The most abundant group of compounds in all tissues was composed of PCBs. Mean concentrations of the sum of a selected group of PCB congeners ranged from 3.2 ng/g in grayling liver to 22.8 ng/g in trout liver and from 1.3 ng/g in grayling muscle to 6.6 ng/g in trout muscle (wet wt.). The second most abundant group was composed of chlordane-related compounds. No significant correlations of organochlorine concentrations with fish weight or length were observed for the data set as a whole. There were marked differences in Sigma PCB, Sigma chlordane and p,p'-DDE concentrations between species. The biomagnification factors for these compounds are similar to ratios reported for other aquatic systems. Comparisons showed that contaminant concentrations in lake trout from Schrader Lake were similar to levels found in burbot and slightly higher than levels in whitefish reported in Canadian studies from the Mackenzie River Delta.

Yunker, M. B., S. M. Backus, et al. (2002). "Sources and significance of alkane and PAH hydrocarbons in Canadian arctic rivers." Estuarine Coastal and Shelf Science 55(1): 1-31.

Hydrocarbon measurements have been made on dissolved, suspended particulate and sediment samples collected in 1987, 1993 and 1994 from the Mackenzie River delta and shelf and in 1993 from 10 smaller Northwest Territories and Nunavut rivers that drain into the Canadian Archipelago or Hudson's Bay. Suspended particulate samples from all rivers have a resolved higher alkane pattern with a well-defined odd-even predominance consistent with a major source in terrestrial, vascular plant material. Particulate samples from the 10 smaller rivers have alkane concentrations that are similar to the Mackenzie River during summer, but PAH (polycyclic aromatic hydrocarbon) concentrations are approximately 10 times lower for the parent PAHs and 100 times lower for alkyl PAHs. PAHs on suspended particulate from the Mackenzie River exhibit a uniform composition typical of mature petrogenic sources, while PAHs in the smaller rivers are typical of combustion. The virtual absence of petrogenic PAHs in the smaller rivers is the single most important difference between these and the Mackenzie River. During summer the alkane and PAH composition of suspended particulate in the Mackenzie River is sufficiently homogenous to estimate directly the hydrocarbon load from the particulate load. Mackenzie River particulates and sediments have the hopane and sterane ratios characteristic of immature bitumens, shales or coals from the Devonian Canol formation that outcrops in the lower Mackenzie River valley. The erosion of organic-rich rocks from this formation is likely the source of the refractory petrogenic material found in the Mackenzie River delta and shelf. Data are insufficient to determine whether the petrogenic lower alkanes and PAHs have the same source or whether more mature petroleum also contributes. Because sediment samples (suspended and bed) from the Mackenzie delta have natural PAH concentrations that exceed the level where adverse biological effects are expected to occur, there is an urgent need to establish whether these petroleum-derived PAHs are bioavailable and if they are inducing effects in bottom fish-and other biota. (C) 2002 Elsevier Science Ltd. All rights reserved.

Zanella, L., C. Tessarin, et al. (2000). "Seasonal fluctuations of the organic load of sediments in two ponds of a brackish-water fish farm ("valle") located in the Po River Delta (Italian North Adriatic)." Ophelia 53(2): 79-90.

Seasonal fluctuations of sedimentary Total Organic Carbon (TOC) and Total Kjeldahl Nitrogen (TKN) were investigated in two earthen ponds of a brackishwater extensive fish farm. One was subjected to periodic sediment "ploughing" (hydrocultivation), a practice performed by fishfarmers to oxidise sediments and fertilise the water column. Nutrients and chlorophyll-a were monitored for controlling the impact of hydrocultivation on water overlying treated sediments. The considered variables revealed a dystrophic event occurring in summer, when a dense biomass of macroalgae (7-10 kg m(-2)) died because of a rise in temperature (30 degreesC and over). From July to August a large amount of labile organic matter settled to sediments increasing TOC and TKN from 600 gC m(-2) and 38.5 gN m(-2) to 1500-1800 gC m(-2) and 50-68 gN m(-2), respectively. A phytoplankton bloom occurred, increasing living organic matter in the water column, as pointed out by high values of total-N, total-P and chlorophyll-a. Low levels of dissolved oxygen recorded in August attest to the danger represented by high macroalgae biomasses for the considered ecosystem, mainly because of the high oxygen demand induced by rapid decomposition of macroalgae tissues. In mid-October TOC dropped to 870-890 gC m(-2), and TKN to 42-43 gN m-2. In the two ponds no important difference in variable trends has been pointed out, despite the periodic "ploughing" interventions, probably because hydrocultivation cannot affect dystrophic environments dth such a heavy organic matter recycle.

Zapf-Gilje, R., G. Patrick, et al. (2001). "Overview of the remediation process at sites with creosote related contamination in soil, groundwater and river sediment." Canadian Journal of Civil Engineering 28: 141-154.

Industrial production and use of creosote dates back to the middle of the 1800s, with the largest production occurring in the first part of the 20(th) century. In British Columbia, the historical use of creosote for wood treatment and other industrial applications has been large. The characteristics of creosote have led to widespread contamination from spills and leaks at sites where creosote was used. Three such sites are located along the Fraser River within the Fraser River delta. Two of these sites have been subject to provincial remediation orders, as the potential risk to aquatic life in the Fraser River was considered to be high. Several phases of investigation and remediation have taken place over the past three years, with varying rates of progress, influenced by the complexity of the individual groups of responsible persons and by site conditions. The remediation is, to a large extent, completed at two of the sites, and is well underway at the third site. The remediation involved a combination of reduction of contaminant mass through removal of the near surface contaminated soils, in-place management of polycyclic aromatic hydrocarbon contamination at depth and in the river sediments, and hydraulic control of dissolved and free-phase contamination through pumping from on-site wells. The completed remediation works will allow for continued industrial and (or) commercial use of the site, and provide long-term protection of the Fraser River and its aquatic habitat. The measures implemented are expected to satisfy the provincial Waste Management Act and the Contaminated Sites Regulation for protection of human health and the environment, as well as the federal provisions under the Canadian Fisheries Act for controlling release of deleterious substances and for providing adequate foreshore fish habitat.

Zhang, G., J. Yan, et al. (2003). "Butyltins in sediments and biota from the Pearl River Delta, South China." Chemical Speciation and Bioavailability 14: 35-42.

Butyltins in sediments and biota collected from the Pearl River Delta, South China were analyzed by a gas chromatograph-atomic emission detector (GC-AED). The concentrations of tributyltin (TBT) in the sediments ranged from 1.7 to 379.7 ng/g dry weight. Their spatial distribution suggested that shipping activities, especially shipyards were mostly responsible for the TBT contamination in the region. A good linear relationship was observed between the DBT (dibutyltin)/TBT and MBT (monobutyltin) /TBT ratios of the samples in the Pearl River, the Pearl River estuary and the West River, suggesting that TBT in these areas came from similar sources but had undergone a different extent of degradation. The butyltins in the Macao waters seemed to have undergone a different degradation process. All TBT concentrations of the fish, mussel and shrimp samples collected in this study were below the seafood tolerable average residue level (TARL).

Zhou, H. Y. and M. H. Wong (2000). "Mercury accumulation in freshwater fish with emphasis on the dietary influence." Water Research 34(17): 4234-4242.

The first part of the study investigated mercury (Hg) concentrations in freshwater fish collected from the Pearl River Delta and Hong Kong. Mercury concentrations observed in freshwater fish and fish pond sediments collected from the Pearl River Delta were 17.5-267 ng/g (dry wt) and 96 ng/g (dry wt)-1.67 mug/g (dry wt), respectively. As to samples collected from Hong Kong, Hg concentrations were 15.8-84.4 ng/g (dry wt) in fish flesh and 57-435 ng/g (dry wt) In sediments. Accumulation of Hg in fish was related to the spatial difference of Hp in sediment. Significant linear relationships were obtained for the concentrations of Hg in grass carp (r(2) = 0.51, n = 12), big head (r(2) = 0.97, n = 12) and tilapia (r(2) = 0.55, n = 24). The second part of the study investigated the dietary influence on the uptake of Hg by different fish species cultured in the wastewater treatment system at Au Tau Fisheries Station in Hong Kong. The effect of feeding habits of the six fish species in Hg accumulation was apparent. The highest levels of Hg were observed in black bass with the value of 56.7 ng/g (dry wt), moderately in big head (33.8 ng/g dry wt), grass carp (26.3 ng/g dry wt) and silver carp (20.8 ng/g dry wt), and the least in common carp (18.9 ng/g dry wt) and tilapia (13.7 ng/g dry wt). (C) 2000 Elsevier Science Ltd. All rights reserved.

Zhou, H. Y. and M. H. Wong (2004). "Screening of organochlorines in freshwater fish collected from the pearl River Delta, People's Republic of China." Archives of Environmental Contamination and Toxicology 46(1): 106-113.

HCHs, DDTs, and PCBs were analyzed in fish flesh collected from fish ponds in the Pearl River Delta and compared with those from the Mai Po Marshes (a nature reserve) in Hong Kong, which was considered an unpolluted area. The concentrations for these contaminants were <0.01-7.8 ng/g lipid for HCHs, 22.3-381 ng/g lipid for DDTs, and 60-480 ng/g lipid for PCBs. Nevertheless, levels of HCHs and DDTs in fish flesh were lower than the China National Environmental Protection Agency maximum permissible limits set for foodstuffs. As for PCBs, 16% of fish collected from the Pearl River Delta exceeded the US EPA guideline concentration.