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Liver and skin tumor prevalences in brown bullheads Ameiurus nebulosushave been used in the North American Great Lakes to designate highly contaminated areas of concern and monitor their recovery. Here we interpret the results of six surveys conducted in the Chesapeake Bay watershed between 1992 and 2006, with data for 647 fish. The objective has been to develop an adequate database to critically evaluate the use of tumor prevalence as a habitat quality indicator within the watershed. Surveys featured randomized fish collection; recording of sex, length, weight, and age; and histopathology of all livers and all raised skin lesions. The Bayes information criterion was used to analyze all possible combinations of age, gender, length, and weight as covariates for logistic regression. Length and gender were the covariates that best described liver tumor prevalence. There were no covariates in the model for skin tumor prevalence. In some surveys, biomarkers, such as biliary polynuclear aromatic hydrocarbon (PAH)-like metabolites, hepatic cytochrome P450 activity, and hepatic DNA adducts, were used with sediment and tissue chemistry data to evaluate classes of chemicals as likely contributors to tumor prevalence. We highlight two surveys of the Anacostia River, Washington, D.C. (average = 55% liver tumors, 23% skin tumors), where sediment PAHs, biliary PAH-like metabolites, and hepatic DNA adducts were high, suggesting that PAHs play a major role. We show that logistic regression is an appropriate procedure for comparing “contaminated” versus “reference” locations, and we evaluate the utility of tumor surveys as an environmental indicator for the Chesapeake Bay watershed.

Mummichogs Fundulus heteroclituswere collected in 2002–2004 from six locations within the Delaware Estuary watershed and examined histopathologically. The objective was to compare the prevalence of skin and liver tumors in fish from locations with a range of sediment polynuclear aromatic hydrocarbons (PAHs) based on available data. Fish were collected from (1) three locations within the industrialized Christina River subwatershed (Hershey Run, Newport Marsh (upriver and downriver)); (2) one location in the Motiva Enterprises refinery discharge canal to the Delaware River; (3) one location in the St. Jones River; and (4) one location in Blackbird Creek. Adult mummichogs (=70 mm; n= 21–30 fish per location) were seined and held for necropsy. No neoplastic skin lesions were diagnosed in any fish. No liver tumors were diagnosed in the St. Jones, Motiva, Newport Marsh upriver, or Newport Marsh downriver collections. One of 30 Blackbird Creek mummichogs had foci of hepatocellular alteration (a putative preneoplastic lesion) and one had hepatocellular carcinoma. There was a significant difference in hepatocellular carcinoma prevalence in Hershey Run mummichogs in 2002 (9 of 21 fish, or 43%) and in 2003 (3 of 29 fish, or 10%) compared with all other locations pooled (1 of 145 fish, or 0.7%). Hershey Run is contaminated with creosote from an adjacent Superfund site, where sediments were frequently reported to have total PAH concentrations greater than 100 mg of total PAH/kg and a maximum of 13,300 mg/kg. No other locations had reports of total PAHs higher than 11 mg/kg. In conclusion, liver neoplasia was associated with exposure to sediment containing high concentrations of PAHs derived from creosote. Studies that include tumor prevalence, biomarkers (e.g., DNA adducts and PAH metabolites in bile), and sediment and/or tissue chemistry are recommended to develop a weight of evidence for specific chemical classes.

Elevated liver and skin tumor prevalence has been reported in brown bullhead Ameiurus nebulosusfrom the tidal Anacostia River, Washington, D.C. Movement data are needed to effectively use tumor prevalence as an indicator of habitat quality. We used ultrasonic telemetry to verify the residency of 40 adult brown bullheads (250–310 mm total length) in the Anacostia River during summer 2000, spring 2001, and fall–winter 2001–2002. During summer (10 fish tagged), fish remained within 500 m of their capture–release location, and their mean 95% minimum area polygon (MAP) and linear home ranges were 4.5 ha and 0.50 km. During spring (12 fish tagged), most fish traveled upstream of the capture–release location as water temperatures increased; they were approximately 1 km upriver by the end of the season. Mean 95% MAP and linear home ranges in spring were 19.7 ha and 2.1 km. During fall–winter (18 fish tagged), fish released in the river remained within 4.2 km upstream and 3.1 km downstream of their capture– release location, and their mean 95% MAP and linear home ranges were 15.9 ha and 2.1 km. In comparison, the 95% MAP and linear home ranges of fish released in Lake Kingman (a tidal freshwater impoundment of the Anacostia) were 5.8 ha and 0.58 km. No fish were located outside of the Anacostia River. We conclude that adult brown bullheads were resident in the system throughout the year.

Our objective was to compare the ability of brown bullheads Ameiurus nebulosus to tolerate the implantation of ultrasonic transmitters with different coatings. A total of 14 brown bullheads were surgically implanted with ultrasonic transmitters; 7 transmitters were coated with paraffin wax and 7 with Scotchcast, an inert epoxy resin. Six brown bullheads were held as controls with no surgical procedures. Fish were held for 75 d in a flow-through, gravity-filtered series of tanks and monitored for transmitter expulsion, growth (i.e., percent relative weight change), condition (i.e., relative weight), and mortality. All fish with paraffin-coated implants retained their transmitters for the duration of the experiment, whereas two fish with Scotchcast implants expelled their transmitters within 50 d. All fish in the experiment survived, and the implanted fish exhibited growth and condition similar to those of the controls. On the basis of these results, we conclude that brown bullheads tolerate implantation of paraffin-coated transmitters and this attachment method may be used for brown bullheads in telemetric field studies.

This study was designed to evaluate survival of striped bass yolk-sac larvae and yearlings at three locations in their natural spawning habitat in the upper Chesapeake Bay (Chesapeake and Delaware Canal) using “in-situ” chambers; correlate larval and yearling survival with the presence of 11 water quality parameters, 10 inorganic contaminants and 21 organic contaminants and assess histological effects on yearlings after exposure to habitat water. The cumulative percent survival ranged from 42–59.5% for striped bass larvae after 96 hr of exposure to habitat water during two experiments. Survival in control conditions during these two experiments was 77.5 and 80.5%. Data from previous studies have shown that mortality rates for wild yolk-sac larvae ranged from 7–19% per day. Daily mortality of larvae in the present study was 13–16%; therefore, suspected acutely harmful water quality or contaminant conditions affecting survival were not substantiated. All yearling striped bass survived 10 days of exposure to habitat water. Although habitat water was not acutely toxic, histological examination of surviving yearling striped bass indicated sublethal effects. Telangiectases (lamellar dilations) of the gills was reported for yearlings exposed to habitat water. This pathological change was not found in the controls.

Numerous factors have been implicated in the decline of striped bass Morone saxatilis along the east coast of the United States. This study was designed to evaluate the effects of contaminants and water quality on survival of striped bass larvae in a natural spawning habitat (Nanticoke River, Maryland). Larvae were tested in chambers submerged in the river. Organic and inorganic contaminants and water quality variables were monitored to correlate survival of larvae with habitat quality. In two 96-h experiments at three river stations, 90–99% of larvae died whereas control mortality was only 15–25%; the differences were significant. None of the 69 organic contaminants specifically analyzed were detected in river water and can be eliminated as causes of larval mortality. Of the eight metals analyzed, seven never exceeded 50 µg/L in river water, but total aluminum concentrations were 480–4,100 µg/L (39–181 µg/L filtered sample). Factors suspected as contributors to mortality were low pH (6.0–6.8), high aluminum concentrations, and the softness of the fresh river water (23–136 mg/L total hardness).

Effects of tributyltin (TBT) on survival, growth, morphometry, and RNA-DNA ratio in larval striped bass(Morone saxatilis) were assessed in three experiments. In Experiment I, 13 day old larvae were exposed to 0, 0.067, 0.766, or 2.284 µg TBT/L for 6 days. All larvae exposed to 2.284 µ/L died by day 5; exposure to 0.766 µg/L significantly reduced survival relative to controls (59.8% vs. 81.8%). Significant, concentration-dependent decreases in body depth occurred in larvae exposed to 0.067 and 0.766 µg/L. In Experiment II, all 16 day old larvae exposed to 1.498 µg/L died by day 6. Survival, weight, and morphometry parameters were not significantly different in larvae exposed to 0, 0.052, or 0.444 µg/L for 7 days. In Experiment III, survival was similar in 21 day old larvae exposed to 0, 0.055, 0.218, or 0.514 µ/L for 7 days. Notochord length and dry weight decreased significantly in larvae exposed to 0.514 µg/L. Weight and morphometry parameters were more sensitive indicators of sublethal stress than RNA-DNA ratio. Maximum TBT concentrations reported in Chesapeake Bay marinas are likely to cause increased larval mortality. Longer-term studies are needed to assess effects at <0.050 µg/L, which may be more representative of habitat conditions.