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4.2 Fish Disease Data 4.2 SAN WAN RIVER BASIN FISH DISEASE DATA San Juan River researchers have, in the course of their work, noted what seems to be an unusually high occurrence of abnOlmal growths on fishes (Shanks 1993a). The New Mexico Water Quality Control Commission (1992) has stated that "to date, no fish abnormalities have been identified which are attributable to man-induced pollutants." Thi!! is true to the extent that abnormalities have not been positively traced to specific pollutant sources. There is, however, limited but strong evidence suggesting a correlation between contaminants and abnormalities. In 1992, in response to repeated observations of abnonnalities, Carol Shanks of the Pinetop Fish Health Center, FWS, undertook a preliminary histopathological survey of San Juan River fish. Samples from diseased and healthy fish were collected from the San Juan River between the Hogback diversion and Mexican Hat (October 1992), and from secondary channels of the river between Shiprock and Bluff (May 1993). A total on 1 apparently diseased and 11 healthy fish was sampled in October and 15 diseased and 3 healthy fish were collected in May (Appendix 5) (Shariks 1993b). Fish were examined in the field and tissue samples were transferred to the Pinetop Fish Health Center for pathogen identification (Shanks 1993a). Of the diseased fish taken in October 1992, 77% (N=24) were tlannelmouth sucker, common CaIp (Cyprinus carpio) was 10% (N=3), channel catfish (Icialurus punctaius) was 6% (N=2), and both roundtail chub and bluehead sucker were 3% (N= 1). Of diseased fish collected in May 1993, tlannelmouth sucker constituted 47% (N=7), channel catfish were 27% (N=4), and both common carp and bluehead sucker were 13% (N=2) (Shanks 1993). Skin lesions, which occurred primarily near the dorsal fm, identified the presence of disease. Three. species of bacteria were isolated from the lesions of fish collected in May 1993: Aeromonas hydrophila (also isolated in October 1992), Ciirobacter freundii, and Acinetobacter sp. According to Shanks (1993a), "these bacterial species have been designated as fish pathogens but usually require stressors such as high contaminant levels or malnutrition to invade the host. " A Colorado squawfish taken in May 1993 appeared healthy, but Acinetobacter sp. was isolated from its skin. Shanks hypothesized that either Colorado squawfish are less susceptible than tlannelmouth sucker to contaminants stress and subsequent bacterial invasion, or the fish was in an early stage of infection and tissue abnormalities had not yet occurred (Shanks 1993a). The results of the fish surveys indicate that disease is a problem in San Juan River fish, particularly in tlannelmouth sucker. Histological examinations of the fish sampled are currently being perfonned by a researcher at Bozeman Technical Center to detennine what contaminants, if any, caused the abnormalities (Shanks 1993). In the San Juan DOl Irrigation Drainage Study, discussed in greater detail under the IRRIGATION section (4.10), high percentages of abnormalities were found in tlannelmouth sucker and channel catfish. A total of 49 fish from 7 species was sampled from the San Juan River in the spring and fall of 1990 (Blanchard et al. 1993). Of these, 28% oftlannelmouth sucker and 35% of channel catfish had e~ lesions. In the Shiprock to Cudei reach of the river, 50% oftlannelmouth sucker and 37% of channel catfish sampled had lesions. It was suggested that the lesions were the result of exposure to polycyclic aromatic hydrocarbons (PAHs)and that the.physiological stress caused by the lesions could exacerbate or synergistically work with other contaminants, further weakening the fish (U.S. Fish and Wildlife Service 1991b). Hepato-histological examinations have also been perfonned on San Juan River fish. In one sampling, the livers from 36 tlannelmouth sucker from the San Juan River were examined, and 77% of them exhibited large nwnbers of eosinophillic granulocytes (U.S. Fish and Wildlife Service 1991 b, Herman 1991a). At the time of the analysis, the condition, as manifested in intlammatory tissues around the bile ducts; was interpreted as either being normal and age-related or an abnormality due to accwnulation of toxic substances (Herman 1991a). A sample of six livers from tlannelmouth sucker collected from Alkali Creek in Colorado suggested that the San Juan River flannelmouth sucker livers had experienced unusual tissue. breakdown and that the large nwnber of granulocytes in the fish was abnonnal (Herman 1991b). 16