Histopathology of brown bullhead (Ameiurus nebulosus), smallmouth bass (Micropterus dolomieu), and yellow perch (Perca flavescens) in relation to polychlorinated biphenyl (PCB) contamination in the Hudson River.

From the 1940s through 1977, at least 590,000kg of polychlorinated biphenyls (PCBs) were released into the Hudson River from General Electric manufacturing plants located in Hudson Falls and Fort Edward, New York. In 1984, the U.S. Environmental Protection Agency designated a nearly 322km reach as the Hudson River PCBs Superfund Site. Here we describe a Fish Health Assessment study, part of a Natural Resource Damage Assessment, that evaluated the prevalence of toxicopathic lesions in adult brown bullhead (Ameiurus nebulosus), smallmouth bass (Micropterus dolomieu), and yellow perch (Perca flavescens). In fall 2001, 29-51 fish of each species were collected in fall 2001 from highly contaminated areas below the plants (Thompson Island Pool (TIP) and Stillwater Dam Pool (STW)), an upriver reference area (Feeder Dam Pool (FDP)), and a reference lake, Oneida Lake (ODA). The focus was on histopathologic lesions and observations associated with contaminant exposure: liver-neoplasms, foci of cellular alteration, bile duct hyperplasia; testes-ovotestis (testicular oocytes), germ cell degeneration, altered developmental stage; ovaries-atresia and altered developmental stage. Lesions associated with PCB exposure were defined as those with significantly greater prevalence and/or severity in TIP and STW compared with ODA and FDP. For brown bullhead and smallmouth bass, no lesions or changes in gonadal development met those criteria. In yellow perch, ovarian atresia was the only lesion associated with PCB exposure. Prevalence was 53% in FDP, 75% in ODA, and 100% in both STW and TIP; severity increased from mostly minimal to mild-moderate. Because of the high prevalence of atresia in reference collections, it is likely that factors other than PCBs are also involved. As part of a post-dredging monitoring plan, we recommend assessing gonad structure and function in yellow perch collected at the time of spawning in locations with a range of PCB contamination.

Very low embryonic crude oil exposures cause lasting cardiac defects in salmon and herring.

The 1989 Exxon Valdez disaster exposed embryos of pink salmon and Pacific herring to crude oil in shoreline spawning habitats throughout Prince William Sound, Alaska. The herring fishery collapsed four years later. The role of the spill, if any, in this decline remains one of the most controversial unanswered questions in modern natural resource injury assessment. Crude oil disrupts excitation-contraction coupling in fish heart muscle cells, and we show here that salmon and herring exposed as embryos to trace levels of crude oil grow into juveniles with abnormal hearts and reduced cardiorespiratory function, the latter a key determinant of individual survival and population recruitment. Oil exposure during cardiogenesis led to specific defects in the outflow tract and compact myocardium, and a hypertrophic response in spongy myocardium, evident in juveniles 7 to 9 months after exposure. The thresholds for developmental cardiotoxicity were remarkably low, suggesting the scale of the Exxon Valdez impact in shoreline spawning habitats was much greater than previously appreciated. Moreover, an irreversible loss of cardiac fitness and consequent increases in delayed mortality in oil-exposed cohorts may have been important contributors to the delayed decline of pink salmon and herring stocks in Prince William Sound.

Aluminum smelter-derived polycyclic aromatic hydrocarbons and flatfish health in the Kitimat marine ecosystem, British Columbia, Canada.

From 2000-2004 a monitoring study was conducted to evaluate the impacts of aluminum smelter-derived polycyclic aromatic hydrocarbons (PAHs) on the health of fish in the marine waters of Kitimat, British Columbia, Canada. These waters are part of the historical fishing grounds of the Haisla First Nation, and since the 1950s the Alcan Primary Metal Company has operated an aluminum smelter at the head of the Kitimat Arm embayment. As a result, adjacent marine and estuarine sediments have been severely contaminated with a mixture of smelter-associated PAHs in the range of 10,000-100,000 ng/g dry wt. These concentrations are above those shown to cause adverse effects in fish exposed to PAHs in urban estuaries, but it was uncertain whether comparable effects would be seen at the Kitimat site due to limited bioavailability of smelter-derived PAHs. Over the 5-year study we conducted biennial collections of adult English sole (Parophrys vetulus) and sediment samples at the corresponding capture sites. Various tissue samples (e.g. liver, kidney, gonad, stomach contents) and bile were taken from each animal to determine levels of exposure and biological effects, and compare the uptake and toxicity of smelter-derived PAHs with urban mixtures of PAHs. Results showed significant intersite differences in concentrations of PAHs. Sole collected at sites nearest the smelter showed increased PAH exposure, as well as significantly higher prevalences of PAH-associated liver disease, compared to sites within Kitimat Arm that were more distant from the smelter. However, measures of PAH exposure (e.g., bile metabolites) were surprisingly high in sole from the reference sites outside of Kitimat Arm, though sediment and dietary PAHs at these sites were low, and fish from the areas showed no biological injury. PAH uptake, exposure, and biological effects in Kitimat English sole were relatively lower when compared to English sole collected from urban sites contaminated with PAH mixtures from other sources. These findings indicate that while smelter-associated PAHs in Kitimat Arm appear to be causing some injury to marine resources, they likely have reduced bioavailability, and thus reduced biological toxicity, compared to other environmental PAH mixtures.

Chronic low-level domoic acid exposure alters gene transcription and impairs mitochondrial function in the CNS.

Domoic acid is an algal-derived seafood toxin that functions as a glutamate agonist and exerts excitotoxicity via overstimulation of glutamate receptors (AMPA, NMDA) in the central nervous system (CNS). At high (symptomatic) doses, domoic acid is well-known to cause seizures, brain lesions and memory loss; however, a significant knowledge gap exists regarding the health impacts of repeated low-level (asymptomatic) exposure. Here, we investigated the impacts of low-level repetitive domoic acid exposure on gene transcription and mitochondrial function in the vertebrate CNS using a zebrafish model in order to: (1) identify transcriptional biomarkers of exposure; and (2) examine potential pathophysiology that may occur in the absence of overt excitotoxic symptoms. We found that transcription of genes related to neurological function and development were significantly altered, and that asymptomatic exposure impaired mitochondrial function. Interestingly, the transcriptome response was highly variable across the exposure duration (36 weeks), with little to no overlap of specific genes across the six exposure time points (2, 6, 12, 18, 24, and 36 weeks). Moreover, there were no apparent similarities at any time point with the gene transcriptome profile exhibited by the glud1 mouse model of chronic moderate excess glutamate release. These results suggest that although the fundamental mechanisms of toxicity may be similar, gene transcriptome responses to domoic acid exposure do not extrapolate well between different exposure durations. However, the observed impairment of mitochondrial function based on respiration rates and mitochondrial protein content suggests that repetitive low-level exposure does have fundamental cellular level impacts that could contribute to chronic health consequences.

Zebrafish as a model for Vibrio parahaemolyticus virulence.

Vibrio parahaemolyticus is a Gram-negative, naturally occurring marine bacterium. Subpopulations of strains belonging to this species cause an acute self-limiting gastroenteritis in humans and, less commonly, wound infections. In vivo models to differentiate avirulent and virulent strains and evaluate the pathogenic potential of strains of this species have been largely focused on the presence of known virulence factors such as the thermostable direct haemolysin (TDH), the TDH-related haemolysin (TRH) or the contributions of the type 3 secretion systems. However, virulence is likely to be multifactorial, and additional, yet to be identified factors probably contribute to virulence in this bacterium. In this study, we investigated an adult zebrafish model to assess the overall virulence of V. parahaemolyticus strains. The model could detect differences in the virulence potential of strains when animals were challenged intraperitoneally, based on survival time. Differences in survival were noted irrespective of the source of isolation of the strain (environmental or clinical) and regardless of the presence or absence of the known virulence factors TDH and TRH, suggesting the influence of additional virulence factors. The model was also effective in comparing differences in virulence between the wild-type V. parahaemolyticus strain RIMD2210633 and isogenic pilin mutants ΔpilA and ΔmshA, a double mutant ΔpilA : ΔmshA, as well as a putative chitin-binding protein mutant, ΔgbpA.

Toxicity of forest fire retardant chemicals to stream-type chinook salmon undergoing parr-smolt transformation.

Long-term fire retardants are used to prevent the spread of wildland fires. These products are normally applied by aircraft and are intended specifically for terrestrial application, but fire retardants have entered aquatic habitats by misapplication and/or accidental spills and have resulted in fish mortalities. The authors examined the toxicity of two fire retardant products, PHOS-CHEK 259F and LC-95A, to salmon undergoing parr-smolt transformation. Yearling stream-type chinook salmon at the smolt stage were exposed to eight concentrations of each retardant in freshwater and a no-PHOS-CHEK control for 96 h to determine acute toxicity. Concentrations of the products that caused 50% mortality were 140.5 and 339.8 mg/L for 259F and LC-95A, respectively, and could occur during accidental drops into aquatic habitats. Damage to gill tissues seen in histopathological sections was attributed to fire retardant exposure. Un-ionized ammonia levels, from 259F, were sufficient to cause acute mortality; but additional factors, indicated by increased phagosome prevalence in the gills, might have contributed to mortality during LC-95A exposure. Seawater and disease challenges were performed to determine sublethal effects of product exposures on fish health. Although PHOS-CHEK exposure did not adversely affect chinook salmon's susceptibility to Listonella anguillarum, exposure did significantly reduce seawater survival. Reduced salmon survival resulting from prior fire retardant exposure during their transition from freshwater rearing environments to seawater may decrease the abundance of salmon populations.

Ichthyosporidium weissii n. sp. (Microsporidia) infecting the arrow goby (Clevelandia ios).

Gonadal infections by a novel microsporidium were discovered in 34% (13/38) of arrow gobies, Clevelandia ios, sampled over a 3-yr period from Morro Bay Marina in Morro Bay, California. Gonadal tumors had been reported in arrow gobies from this geographic area. The infected gonads, found primarily in females, typically appeared grossly as large, white-gray firm and lobulated masses. Histological examination revealed large, multilobate xenomas within the ovaries and no evidence of neoplasia. Typical of the genus Ichthyosporidium, the large xenomas were filled with developmental stages and pleomorphic spores. Wet mount preparations showed two general spore types: microspores with mean length of 6.2 (7.0-4.9, SD = 0.6, N = 20) µm and mean width of 4.3 (5.3-2.9, SD = 0.8) µm; and less numerous macrospores with mean length of 8.5 (10.1-7.1, SD = 1.0, N = 10) µm and mean width of 5.5 (6.2-4.8, SD = 0.5) µm. Transmission electron microscopy demonstrated stages consistent with the genus and 35-50 turns of the polar filament. Small subunit rDNA gene sequence analysis revealed that the parasite from arrow gobies was most closely related to, but distinct from Ichthyosporidium sp. based on sequences available in GenBank. We conclude that this microsporidium represents a new species of Ichthyosporidium, the first species of this genus described from a member of the family Gobiidae and from the Pacific Ocean.

Potent phototoxicity of marine bunker oil to translucent herring embryos after prolonged weathering.

Pacific herring embryos (Clupea pallasi) spawned three months following the Cosco Busan bunker oil spill in San Francisco Bay showed high rates of late embryonic mortality in the intertidal zone at oiled sites. Dead embryos developed to the hatching stage (e.g. fully pigmented eyes) before suffering extensive tissue deterioration. In contrast, embryos incubated subtidally at oiled sites showed evidence of sublethal oil exposure (petroleum-induced cardiac toxicity) with very low rates of mortality. These field findings suggested an enhancement of oil toxicity through an interaction between oil and another environmental stressor in the intertidal zone, such as higher levels of sunlight-derived ultraviolet (UV) radiation. We tested this hypothesis by exposing herring embryos to both trace levels of weathered Cosco Busan bunker oil and sunlight, with and without protection from UV radiation. Cosco Busan oil and UV co-exposure were both necessary and sufficient to induce an acutely lethal necrotic syndrome in hatching stage embryos that closely mimicked the condition of dead embryos sampled from oiled sites. Tissue levels of known phototoxic polycyclic aromatic compounds were too low to explain the observed degree of phototoxicity, indicating the presence of other unidentified or unmeasured phototoxic compounds derived from bunker oil. These findings provide a parsimonious explanation for the unexpectedly high losses of intertidal herring spawn following the Cosco Busan spill. The chemical composition and associated toxicity of bunker oils should be more thoroughly evaluated to better understand and anticipate the ecological impacts of vessel-derived spills associated with an expanding global transportation network.

Unexpectedly high mortality in Pacific herring embryos exposed to the 2007 Cosco Busan oil spill in San Francisco Bay.

In November 2007, the container ship Cosco Busan released 54,000 gallons of bunker fuel oil into San Francisco Bay. The accident oiled shoreline near spawning habitats for the largest population of Pacific herring on the west coast of the continental United States. We assessed the health and viability of herring embryos from oiled and unoiled locations that were either deposited by natural spawning or incubated in subtidal cages. Three months after the spill, caged embryos at oiled sites showed sublethal cardiac toxicity, as expected from exposure to oil-derived polycyclic aromatic compounds (PACs). By contrast, embryos from the adjacent and shallower intertidal zone showed unexpectedly high rates of tissue necrosis and lethality unrelated to cardiotoxicity. No toxicity was observed in embryos from unoiled sites. Patterns of PACs at oiled sites were consistent with oil exposure against a background of urban sources, although tissue concentrations were lower than expected to cause lethality. Embryos sampled 2 y later from oiled sites showed modest sublethal cardiotoxicity but no elevated necrosis or mortality. Bunker oil contains the chemically uncharacterized remains of crude oil refinement, and one or more of these unidentified chemicals likely interacted with natural sunlight in the intertidal zone to kill herring embryos. This reveals an important discrepancy between the resolving power of current forensic analytical chemistry and biological responses of keystone ecological species in oiled habitats. Nevertheless, we successfully delineated the biological impacts of an oil spill in an urbanized coastal estuary with an overlapping backdrop of atmospheric, vessel, and land-based sources of PAC pollution.

Recurrent die-offs of adult coho salmon returning to spawn in Puget Sound lowland urban streams.

Several Seattle-area streams in Puget Sound were the focus of habitat restoration projects in the 1990s. Post-project effectiveness monitoring surveys revealed anomalous behaviors among adult coho salmon returning to spawn in restored reaches. These included erratic surface swimming, gaping, fin splaying, and loss of orientation and equilibrium. Affected fish died within hours, and female carcasses generally showed high rates (>90%) of egg retention. Beginning in the fall of 2002, systematic spawner surveys were conducted to 1) assess the severity of the adult die-offs, 2) compare spawner mortality in urban vs. non-urban streams, and 3) identify water quality and spawner condition factors that might be associated with the recurrent fish kills. The forensic investigation focused on conventional water quality parameters (e.g., dissolved oxygen, temperature, ammonia), fish condition, pathogen exposure and disease status, and exposures to metals, polycyclic aromatic hydrocarbons, and current use pesticides. Daily surveys of a representative urban stream (Longfellow Creek) from 2002-2009 revealed premature spawner mortality rates that ranged from 60-100% of each fall run. The comparable rate in a non-urban stream was <1% (Fortson Creek, surveyed in 2002). Conventional water quality, pesticide exposure, disease, and spawner condition showed no relationship to the syndrome. Coho salmon did show evidence of exposure to metals and petroleum hydrocarbons, both of which commonly originate from motor vehicles in urban landscapes. The weight of evidence suggests that freshwater-transitional coho are particularly vulnerable to an as-yet unidentified toxic contaminant (or contaminant mixture) in urban runoff. Stormwater may therefore place important constraints on efforts to conserve and recover coho populations in urban and urbanizing watersheds throughout the western United States.

Reduced cytochrome P4501A activity and recovery from oxidative stress during subchronic benzo[a]pyrene and benzo[e]pyrene treatment of rainbow trout.

This study assessed the role of aryl hydrocarbon receptor (AHR) affinity, and cytochrome P4501A (CYP1A) protein and activity in polyaromatic hydrocarbon (PAH)-induced oxidative stress. In the 1-100nM concentration range benzo[a]pyrene (BaP) but not benzo[e]pyrene (BeP) competitively displaced 2nM [(3)H]2, 3, 7, 8-tetrachloro-dibenzo-p-dioxin from rainbow trout AHR2α. Based on appearance of fluorescent aromatic compounds in bile over 3, 7, 14, 28 or 50days of feeding 3µg of BaP or BeP/g fish/day, rainbow trout liver readily excreted these polyaromatic hydrocarbons (PAHs) and their metabolites at near steady state rates. CYP1A proteins catalyzed more than 98% of ethoxyresorufin-O-deethylase (EROD) activity in rainbow trout hepatic microsomes. EROD activity of hepatic microsomes initially increased and then decreased to control activities after 50days of feeding both PAHs. Immunohistochemistry of liver confirmed CYP1A protein increased in fish fed both PAHs after 3days and remained elevated for up to 28days. Neither BaP nor BeP increased hepatic DNA adduct concentrations at any time up to 50days of feeding these PAHs. Comet assays of blood cells demonstrated marked DNA damage after 14days of feeding both PAHs that was not significant after 50days. There was a strong positive correlation between hepatic EROD activity and DNA damage in blood cells over time for both PAHs. Neither CYP1A protein nor 3-nitrotyrosine (a biomarker for oxidative stress) immunostaining in trunk kidney were significantly altered by BaP or BeP after 3, 7, 14, or 28days. There was no clear association between AHR2α affinity and BaP and BeP-induced oxidative stress.

Sublethal exposure to crude oil during embryonic development alters cardiac morphology and reduces aerobic capacity in adult fish.

Exposure to high concentrations of crude oil produces a lethal syndrome of heart failure in fish embryos. Mortality is caused by cardiotoxic polycyclic aromatic hydrocarbons (PAHs), ubiquitous components of petroleum. Here, we show that transient embryonic exposure to very low concentrations of oil causes toxicity that is sublethal, delayed, and not counteracted by the protective effects of cytochrome P450 induction. Nearly a year after embryonic oil exposure, adult zebrafish showed subtle changes in heart shape and a significant reduction in swimming performance, indicative of reduced cardiac output. These delayed physiological impacts on cardiovascular performance at later life stages provide a potential mechanism linking reduced individual survival to population-level ecosystem responses of fish species to chronic, low-level oil pollution.

Improved flatfish health following remediation of a PAH-contaminated site in Eagle Harbor, Washington.

Eagle Harbor in Puget Sound, WA became a Superfund site in 1987 due to polycyclic aromatic hydrocarbons (PAHs) released chronically from a nearby creosoting facility. Early studies here (1983-1986) demonstrated up to an approximately 80% prevalence of toxicopathic liver lesions, including neoplasms, in resident English sole (Parophrys vetulus). These lesions in English sole are consistently associated with PAH exposure in multiple field studies, and one laboratory study. Later studies (1986-1988) incorporated biomarkers of PAH exposure and effect, including hepatic CYP1A expression and xenobiotic-DNA adducts, and biliary fluorescent aromatic compounds (FACs). Before site remediation, lesion prevalences and other biomarker values in this species from Eagle Harbor were among the highest compared to other sites in Puget Sound and the US Pacific Coast. To sequester PAH-contaminated sediments, in 1993-1994, a primary cap of clean sediment was placed over the most-contaminated 54acres, with a 15-acre secondary cap added from 2000-2002. Lesion prevalences and biomarker values before primary capping were reduced compared to 1983-1986, consistent with facility closure in 1988 and shore-based source controls begun in 1990. Liver lesion risk, hepatic CYP1A activities, and levels of biliary FACs from fish collected immediately after and at regular intervals up to 2 years after primary capping were variable relative to pre-capping. Over the entire monitoring period since primary capping (128 months), but particularly after 3 years, there was a significantly decreasing trend in biliary FACs, hepatic DNA adducts and lesion risk in English sole. In particular, lesion risk has been consistently low (<0.20) compared to primary cap initiation (set at 1.0), from approximately 4 years after primary capping through April 2004. These results show that the sediment capping process has been effective in reducing PAH exposure and associated deleterious biological effects in a resident flatfish, and that longer term monitoring of pollutant responses in biological resources, such as resident fish, is needed in order to demonstrate the efficacy of this type of remediation.

Xenoestrogen exposure and effects in English sole (Parophrys vetulus) from Puget Sound, WA.

Vitellogenin, a yolk protein produced in the liver of oviparous animals in response to estrogens, normally occurs only in sexually mature females with developing eggs. However, males can synthesize vitellogenin when exposed to environmental estrogens, making the abnormal production of vitellogenin in male animals a useful biomarker for xenoestrogen exposure. In 1997-2001, as part of the Washington State's Puget Sound Assessment and Monitoring Program, we surveyed English sole from a number of sites for evidence of xenoestrogen exposure, using vitellogenin production in males as an indicator. Significant levels of vitellogenin were found in male fish from several urban sites, with especially high numbers of fish affected in Elliott Bay, along the Seattle Waterfront. Intersex fish were rare, comprising only two fish out of more than 2900 examined. Other ovarian and testicular lesions, including oocyte atresia, were also observed, but their prevalence did not appear to be related to xenoestrogen exposure. However, at the Elliott Bay sites where abnormal vitellogenin production was observed in male sole, the timing of spawning in both male and female English sole appeared altered. Sources of xenoestrogens and types of xenoestrogens present in Elliott Bay are poorly documented, but the compounds are likely associated with industrial discharges, surface runoff, and combined sewer outfalls.

Liver lesions in demersal fishes near a large ocean outfall on the San Pedro Shelf, California.

The prevalence of toxicopathic liver lesions in demersal fish on the San Pedro Shelf, California was determined for a 15-year period (1988-2003). Fish livers were sampled at fixed locations as part of the Orange County Sanitation Districts (OCSD) ocean monitoring program. Histopathological examination of selected fish liver tissues was studied to determine whether the wastewater discharge had affected fish health. The prevalence of toxicopathic lesion classes neoplasms (NEO), preneoplastic foci of cellular alteration (FCA), and hydropic vacuolation (HYDVAC) varied among species and locations. For all species sampled, severe lesions occurred in 6.2% of the fish examined (n=7,694). HYDVAC (4.1%) was the most common toxicopathic lesion type followed by FCA (1.4%) and NEO (0.7%). HYDVAC occurred only in white croaker (Genyonemus lineatus), accounting for 84.8% of the toxicopathic lesions for this species. Prevalence of HYDVAC, NEO, and FCA in white croaker was 15.2, 2.0, and 0.7%, respectively. The prevalence of HYDVAC and NEO in white croaker increased with age and size but there was no sexual difference. A linear regression model was used for hypothesis testing to account for significant differences in fish size (and age for croakers) at the different sampling locations. This analysis showed that for HYDVAC there was no spatial or location effect for lesion rate or size/age of onset. For NEO, the model predicted that white croaker near the wastewater outfall may acquire these lesions at a smaller size/younger age, and at a higher rate, than at other sites. However, this result may be biased due to the unequal size frequency distributions and the low prevalence of NEO in white croaker at the different sampling sites. Bigmouth sole (Hippoglossina stomata) had a prevalence of FCA and NEO of 1.3 and 0.35%, respectively, but the prevalence and distribution of lesions was too few for statistical testing. There was no sexual difference for lesion prevalence in hornyhead turbot (Pleuronichthys verticalis) and the prevalence of FCA and NEO was 3.4 and 0.37%, respectively. FCA prevalence increased with size in hornyhead turbot and there were no significant spatial differences for lesion rates and fish size at lesion onset. Overall, consistent spatial differences for lesion prevalence were not demonstrated and highlight the analytical difficulties of detecting a possible point source impact when the effect is rare, correlated with the size/age structure of the population, and may be caused by exposure to unknown multiple sources. Thus, the usefulness of liver histopathology as a point-source monitoring tool is best applied to where the spatial scale of impact generally exceeds the home range of the target species.

Accumulation and clearance of orally administered erythromycin and its derivative, azithromycin, in juvenile fall chinook salmon Oncorhynchus tshawytscha.

Fall Chinook salmon Oncorhynchus tshawytscha were fed practical diets medicated with azithromycin (30 mg kg(-1) fish for 14 d) or erythromycin (100 mg kg(-1) fish for 28 d) either 1, 2, or 3 times beginning 14 d after initiation of exogenous feeding (February) and ending at smoltification (June). Average tissue concentrations of azithromycin increased from 19.0 microg g(-1) in fry to 44.9 microg g(-1) in smolts, and persisted in the tissues > 76 d after treatment ceased. Tissue concentrations of erythromycin were comparatively low, ranging from 0.2 microg g(-1) in fry to 10.4 microg g(-1) in smolts. Erythromycin was not detectable 21 d post-treatment. Neither antibiotic caused histopathologically significant lesions in the trunk kidney or other organ tissues. The high tissue concentrations and prolonged retention of azithromycin in Chinook may be factors that increase the efficacy of the antibiotic against Renibacterium salmoninarum, compared with erythromycin, particularly in early life history stages before covertly infected fish show clinical signs of disease.

Toxicopathic liver lesions in English sole and chemical contaminant exposure in Vancouver Harbour, Canada.

The prevalence of toxicopathic liver lesions in English sole (Pleuronectes vetulus) was determined along a presumed gradient of chemical contamination in Vancouver Harbour, Canada. Fish were captured from five sites in or near Vancouver Harbour, British Columbia, Canada. No toxicopathic lesions were observed in fish examined at the reference site (Howe Sound outside Vancouver Harbour), or at the outer harbour site. In contrast, 20-23% of the fish from three sites located in the central harbour, Indian Arm and Port Moody Arm had one or more types of toxicopathic lesions. Likewise, aromatic hydrocarbon (AH) metabolites measured in bile exhibited a gradient in levels from lower concentrations at the reference site to significantly higher levels in fish from Indian Arm and Port Moody Arm harbour sites. The occurrence of toxicopathic liver lesions was statistically associated with concentrations of AHs measured in sediment and AH metabolite levels measured in bile.