Long-term trends in liver neoplasms in brown bullhead in the Buffalo River, New York, USA.

The Buffalo River area of concern (AOC) was assigned an impaired status for the fish tumors and other deformities beneficial use impairment category by the New York State Department of Environmental Protection in 1989. This was initially based on an inadequately documented brown bullhead (Ameiurus nebulosus) feeding study using river sediment extracts. The presence of liver tumors was subsequently supported by reports of a 19 to 27% prevalence in wild brown bullhead between 1983 and 1988 and a 4.8% prevalence in 1998. However, neither fish size (or age) nor sample locations were given, and histopathological definitions were inconsistent in these previous studies. Therefore, in 2008, we re-evaluated the prevalence of hepatocellular and chloangiocellular tumors (as well as other gross indicators of fish health) in brown bullhead averaging 25 cm in length collected from three reaches of the Buffalo River and recorded our collection sites by global positioning system. Among the 37 fish of appropriate size collected, only three exhibited liver tumors (8%). The tumors were evenly distributed within the three reaches, and only hepatocellular tumors were found. There were no differences in the prevalence of hepatic foci of alteration, body weight, length, or hepatosomatic index among the three reaches, but the conditions factor was significantly lower in fish from reach 2. Natural attenuation of water and sediment quality are the most likely causes for the decrease in liver tumors. The prevalence of liver tumors between 1998 and 2008 in the Buffalo River is similar to that found in recovery-stage AOCs and some Great Lakes reference areas.