Neurotoxic pesticides are known to contaminate surface waters that provide habitat for salmonids, including some listed for protection under the U.S. Endangered Species Act. Despite their widespread use, the impacts of these pesticides on the neurological health of wild salmon are not well understood. Of particular concern are the organophosphate and carbamate insecticides that block synaptic transmission by inhibiting neuronal acetylcholinesterase. Here we assess the effects of diazinon, an organophosphate insecticide, on alarm pheromone induced antipredator responses and homing behavior in chinook salmon (Oncorhynchus tshawytscha). Nominal exposure concentrations (0.1, 1.0, and 10.0 µg·L-1) were chosen to emulate diazinon pulses in the natural environment. In the antipredator study, diazinon had no effect on swimming behavior or visually guided food capture. However, the pesticide significantly inhibited olfactory-mediated alarm responses at concentrations as low as 1.0 µg·L-1. Similarly, homing behavior was impaired at 10.0 µg·L-1. Our results suggest that olfactory-mediated behaviors are sensitive to anticholinesterase neurotoxicity in salmonids and that short-term, sublethal exposures to these insecticides may cause significant behavioral deficits. Such deficits may have negative consequences for survival and reproductive success in these fish.

Yearling juvenile coho and Chinook salmon were sampled on 28 cruises in June and September 1981-85 and 1998-07 in continental shelf and oceanic waters off the Pacific Northwest. Oceanographic variables measured included temperature, salinity, water depth, and chlorophyll concentration (all cruises) and copepod biomass during the cruises from 1998-07. Juvenile salmonids were found almost exclusively in continental shelf waters, and showed a patchy distribution: half were collected in 5% of the collections and none were collected in 40% of the collections. Variance-to-mean ratios of the catches were high, also indicating patchy spatial distributions for both species. The salmon were most abundant in the vicinity of the Columbia River and the Washington coast in June; by September, both were less abundant, although still found mainly off Washington. In June, the geographic center-of-mass of the distribution for each species was located off Grays Harbor, WA, near the northern end of our sampling grid, but in September, it shifted southward and inshore. Coho salmon ranged further offshore than Chinook salmon: in June, the average median depth where they were caught was 85.6 and 55.0 m, respectively, and in September it was 65.5 and 43.7 m, respectively. Abundances of both species were significantly correlated with water depth (negatively), chlorophyll (positively) and copepod biomass (positively). Abundances of yearling Chinook salmon, but not of yearling coho salmon, were correlated with temperature (negatively). We discuss the potential role of coastal upwelling, submarine canyons and krill in determining the spatial distributions of the salmon.

1988. Contaminant effects on ovarian development in English sole (Parophrys vetulus) from Puget Sound, Washington. Can. 8. Fish. Aquat. Sci. 45: 21 33-2146.In a study evaluating the effects sf exposure to xenobiotic compounds on ovarian development in English sole (Parophrys V~~UIUS), prespawni ng females were sampled from four sites in Puget Sound, Washington, during the 1986 and 1987 spawning seasons. Two sampling sites had high concentrations sf xenobiotic compounds in the sediment, while the other sites were less contaminated. The following factors associated with ovarian maturation were measured: ovarian developmental stage, ovarian atresia, gonadosornatic index, plasma estradiol, and plasma vitellsgenin as estimated from alkali-labile phosphorus. contaminant exposure was assessed by measuring concentrations of fluorescent aromatic compounds in the bile, hepatic aryl hydrocarbon hydrowytase (AHH) activity, and hepatic polychlorinated biphenyl levels, and liver tissue was examined histologically for the presence sf suspected towicopathic lesions. Female English sole from the heavily csntaminated sites were significantly less likely to undergo gonadal recrudescence and had lower mean levels of plasma estradiol than females From the less contaminated sites. The risk sf inhibited gonadal recrudescence was significantly increased in sole with elevated hepatic AHH activity, and AHH activity was also significantly negatively correlated with plasma estradiol level. These findings suggest that contaminant exposure may interfere with ovarian development in female English sole.Dans le cadre de lt6valuation des effets sur le developpernent ovarien de la sole anglaise (Parophrys vetulus) de I'exposition 21 des composes x6wobiotiques, des femelles au stade prefrai ont kt6 prelevees en quatre endroits du detrsit Puget (Washington) au cours des saisons de frai de 1986 et 1987. Les s6diments de deux des sites de prelevements presentaient des concentrations elevkes de csrnpss6s w6nobistiques, ceuw des deux autres sites &ant moins contatmines. Les facteurs lies 2 la maturation ovarienne mesurbes snt 6t6 : \'&ape de develsppement svarien, IPatr6sie ovarienne, I'indice gonadssomatique, la teneur en estradiol plasmatique et la teneur en vitellogenine plasmatique estirnee 2 partir du phssphsre labile era milieu alcalin. L'expssitisn aux contaminants a etk determinee par la mesure des eesncentrations des compss6s arsmatiques Fluorescents prksents dans la bile, de l'activite de Bfaryl-hydroxylase des hydrscarbures EAHH) du foie et des teneurs en biphenyles polyehlor~s du fsie et par urn examen kistslogique des tissus hkpatiques pour la recherche de Iksions toxicopathiques. bes soles anglaises femelles des sites forternent contarnines prksentaient, de fasesn significative, un rktablissement gsnadique moins important et des teneurs rnoyennes en estradisl plasmatique inferieures cornparativement aux femelles des sites moins contaminks. Le risque d'une inhibition du rktablissement gonadique etait significativement accru chez les soles p...

Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) from field-contaminated sediments by 2 infaunal invertebrates, Rhepoxynius abronius (a non-deposit feeding amphipod) and Armandia brevis (a non-selective, deposit-feeding polychaete), was examined. Sediments were selected over a large geographical area of the Hudson-Raritan estuary (New York, USA) to assess the potential for bioaccumulation from a typical urban estuary. Assessment of bioaccumulation in these invertebrates is important because of the need to understand their health and role in ecosystem functioning and because they are vectors of sediment-associated contaminants to demersal fish. Our study compared the response of these 2 species over a wide range of PAH concentrations to learn how feeding mode may affect contaminant accumulation. After 10 d of exposure to sedirnents, we assessed the tissue concentrations of 24 PAHs and found no significant differences for the low molecular weight PAHs (LPAHs) between R. abronius and A. brevis. There was, however, a large differential observed between species for bioaccumulated high molecular weight PAHs (HPAHs). Because we assumed that the amphipod was not feeding and most of its tissue burden was received through ventilation of interstitial water (IW), we concluded that IW was probably the major route of uptake for the LPAHs for both species and that sediment ingestion was a much more important uptake route of HPAHs for the polychaete. Analysis of correlations between amphipod and polychaete tissue burdens found that the species were responding similarly to a gradient of PAH concentrations in sediment; however, when the associations between concentrations in tissue and exposure matrix (e.g. sediment, IW) were examined the interpretations were less clear. Concentrations of PAHs in IW and sediment indicated that the partition coefficient (&,) was generally 2 orders of magnitude higher than expected for LPAHs and highly variable between sites for HPAHs. When K, , was re-calculated using free PAH, it became much less variable and was uniformly elevated above the predicted values. The BAF,,, (lipid/organic carbon normalized bioaccumulat~on factor) in the polychaete was generally consistent over the series of PAHs, as expected, and when metabolism and pre-steady state conditions were considered, partitioning of PAHs between tissue and sediment was relatively close to the theoretical maximum. Despite much lower than predicted 1W concentrations, the LPAH bioconcentration factors (BCF) for the amphipod were close to expected, but the HPAH BCFs were close to the predicted values only when expressed in terms of the free PAH. From these data, and previous studies, we conclude that there was a significant reduction in bioavailability of HPAHs to R. abronius due to partitioning of HPAHs to dissolved organic carbon.

The effect of short-term stress on blood clotting times, cell counts, haematocrits, and blood glucose levels was studied in a hatchery strain and wild type rainbow trout, Salmo gairdneri. Blood clotting times declined and thrombocyte counts, haematocrits, and blood glucose levels increased after stress in both strains of trout. The wild type of rainbow trout, however, required less time to recover from the stress than the hatchery strain of rainbow trout. The implications of a stress activated blood coagulation system in fish are discussed.

Previous studies have shown that juvenile chinook salmon Oncorhynchus tshawytscha from a contaminated estuary of Puget Sound, Washington, are immunosuppressed. Immunosuppressed fish may be more susceptible to disease and ultimately experience an increase in mortality. To evaluate this possibility, differences in susceptibility to a marine pathogen in outmigrating juvenile chinook salmon from an urban estuary and a nonurban estuary in Puget Sound were assessed. Juvenile chinook salmon were sampled from hatcheries before their release and subsequently from their respective estuaries as the population outmigrated from freshwater to the saltwater environment during the springs of 1993 and 1994. The study was repeated during a 3-month period to assess the duration of the effect after the fish were removed from the source of contaminants and was replicated during a 2-year period to examine interannual variation. Bile, liver, and stomach contents were collected from fish after capture to determine exposure to organic chemical pollutants. Examination of these tissues demonstrated that juvenile salmon from the urban estuary were exposed to higher concentrations of polycyclic aromatic hydrocarbons and polychlorinated biphenyls than juveniles from the nonurban estuary or hatcheries. Juvenile salmon were challenged with serial doses of a marine pathogen, Vibrio anguillarum (serotype 1575), and mortality was measured daily for 7 d. In both years, salmon from the urban estuary challenged with V. anguillarum exhibited a higher cumulative mortality after exposure to the pathogen than salmon from the hatcheries or the nonurban estuary. Our results together with our previous findings support the hypothesis that contaminant-associated immunodysfunction in juvenile chinook salmon may lead to increased susceptibility to infection by a virulent marine bacterium.

A suite of chemical and biochemical variables responsive to contaminant exposure was measured in three species of benthic flatfish (English sole, Parophrys vetulus, rock sole, Lepidopsetta bilineata, and starry flounder, Platichthys stellatus) sampled from up to five sites in Puget Sound, Washington, to assess the sensitivity of the parameters to differences in levels of contaminant exposure The examined indexes were levels of (a) polychlorinated biphenyls (PCBs) in liver, (b) fluorescent aromatic compounds in bile, (c) hepatic aryl hydrocarbon hydroxylase and ethoxy‐resorufin O deethylase, (d) total hepatic GSH and (e) hydrophobic DNA xenobiotic adducts in liver as measured by 32P postlabeling The sediment concentrations of PCBs and the sum of selected polycyclic aromatic hydrocarbons at the sampling sites ranged from 21 to 570 and 21 to 5,300 ng/g wet weight sediment, respectively The results showed (a) that all the examined indexes could discriminate among sites exhibiting different degrees of chemical contamination, (b) that species differed in the range of response of most of the measured indexes, and (c) that the use of the indexes in concert appeared to enhance the assessment of contaminant exposure and sublethal effects

Anthropogenic factors have contributed to the precipitous decline of wild Pacific salmon stocks, although the mechanisms and processes at work are largely unknown. Pollution may be one of these factors. Sediments in estuaries are known to act as repositories for contaminants , and estuaries are important habitats for ocean-and river-migrating salmon. We have shown that juvenile salmon Oncorhynchus spp. and their prey bioaccumulate chlorinated hydrocarbons and aromatic hydrocarbons-important classes of toxic xenobiotics. Furthermore, we have shown that exposure to these pollutants can lead to immunosuppression and increased disease susceptibility in juvenile salmon. Whether pollution influences natural disease outbreaks in host populations, including salmon, is currently unknown. It is postulated that the occurrence of disease depends on the interaction of the host, the environment, and the pathogen. Absence of pathogens would reduce the potential for adverse environments to influence disease outbreaks. However, a recent reconnaissance survey of juvenile chinook salmon Oncorhynchus tshawytscha from Oregon coastal rivers revealed that pathogens were an integral component in all systems studied, although the prevalence of the pathogens varied. Furthermore, recent studies of natural fish populations have demonstrated that infectious-disease-induced mortality can significantly reduce the size of the host population. By creating adverse environments (e.g., polluted estuaries) which alter the susceptibility of the host to pathogens that are integral and ubiquitous components of the habitat, pollution increases the probability of disease-related impacts on fish populations.