Summary

Description

The South River is a tributary of the Chesapeake Bay flowing near Annapolis, Maryland. In March 2005, brown bullheads were collected in a fyke net set about 1.25 km downriver of the Route 50 Bridge. A total of 30 brown bullheads Ameiurus nebulosus 260 mm were randomly selected for analysis, placed in coolers and transported live to the U.S. Fish and Wildlife Chesapeake Bay Field Office. The fish were held in aerated site water and necropsied over the next two days. A gross examination was performed of the external organs, focusing on raised skin lesions and the appearance of the barbels. For all fish, livers were excised, weighed, cut into sections and preserved in 10 buffered neutral formalin. Sixteen fish had raised skin lesions, which were excised along with adjacent tissues, decalcified, and preserved similarly. Tissues were processed and histopathological examinations were performed. The objective was to determine the prevalence of liver and skin tumors and preneoplastic lesions. We reported a 20 6 of 30 prevalence of liver tumors, split evenly between hepatocellular carcinomas and cholangiocarcinomas. All sixteen fish with the raised skin lesions were diagnosed with skin tumors 53 prevalence. Thirteen of these cases were invasive squamous carcinomas and three were noninvasive epidermal papillomas. Liver tumor prevalence was significantly p0.01, Fishers Exact Test higher than that observed previously in collections from the Tuckahoe River MD, considered a reference area prevalence 4 5 of 117. The liver tumor prevalence in South River bullheads also exceeded the 5 criterion suggested as indicative of highly contaminated areas. Skin tumor prevalence was significantly different between locations South River 1630 53, Tuckahoe: 1117 1, p0.001. The skin tumor prevalence in South River bullheads was about four times the 12 suggested criterion for highly contaminated areas. Barbel abnormalities were not significantly different South: 330 10, Tuckahoe: 387 3, p0.17.