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OlJZ::l~j 4.3.1 EPA Water Quality Standards The San Juan Rivei sample also included a black bullhead (Ameiurus melas) with a papilloma, a type of skin lesion, that showed an unusual number of mucous cells. Papillomas are rare in this species, and the condition has been reported to be related to water quality. Conversely, papillomas have been found on brown bullheads (Ameiurus natalis) from apparently clean water (Herman 1991a). The remaining fish disease data from the San Juan River basin comes from the lower Animas River. In July 1992 the Colorado Department of Wildlife (CDOW), the U.S. Bureau of Reclamation (BR), the FWS, and the Southern Ute Tribe conducted an electrofishing survey of the Animas from the Purple Cliffs area, four miles south of Durango, to the New Mexico state line (Japhet 1993). Diseased bluehead, flannelmouth, and bluehead x white hybrid suckers were first sighted approximately 0.3 miles upstream of a large natural gas well located within 300 feet of the river high water line at T3 3N, R1 OW, S36 (Figure 9) (Walker 1992, Japhet 1993). Two of the fish had large tumors protruding from their bodies, and an estimated 5% of the suckers had large lesions, ulcers, and open sores (Japhet 1993). That percentage can be considered to represent a major feral fish disease outbreak (Walker 1992, Japhet 1993). Pete Walker, a CDOW fish pathologist, examined the aforementioned fish and reported that he suspected Aeromonas salmonicida nova, a bacteria, of causing furunculosis (Walker 1992). Furunculosis is a stress-mediated disease arising in poor water quality. Because the affected fish were found only in the inunediate vicinity of the gas well, there is strong evidence to support that water quality indirectly caused the outbreak of furunculosis (Walker 1992). Following the diagnosis of furunculosis, an additional nine suckers were collected from the Animas River near Bondad, Colorado. Five of the fish had open sores or lesions, while the remaining four had no external signs of disease. When tested, the five fish with lesions and two without showed evidence of exposure to P AHs (Japhet 1993). The above-mentioned studies represent all disease research that has been performed on San Juan River basin fish. With the exception of the hepato-histological investigations and the P AH analyses, the studies have relied on external ell:pressions of disease, which were the most obvious clues of contamination. When such clues have not been available, researchers have often compared tissue, food item, water, or sediment concentrations of a given contaminant with criteria derived from toxicity studies. 4.3. WATER QUALITY STANDARDS 4.3.1 EPA WATER QUALITY STANDARDS Once sampling data have been generated, researchers must decide to which standards the numbers should be compared. When evaluating water quality data, many researchers look to the criteria set by the Enviromnental Protection Agency (EP A); these standards are officially published in the Federal Register. These standards are often considered high, especially for sensitive species, but in the absence of better standards for certain contaminants they are generally used. Below are the EP A criteria for a number of common parameters, trace elements, and organics. All EP A criteria, except where otherwise stated, are from the I July 1993 edition of the Federal Register (Table 3) (Office of the Federal Register 1993). . Alkalinity - The EP A criterion for freshwater aquatic life is a minimum of20 mgll as CaCo, except where natural concentrations are less. Ammonia - The EP A found that acute toxicity of ammonia for 29 species of freshwater fish from 9 farni1ies and 18 genera was 0.083-1.09 mgll NH,. The 96-hour LCso (concentration that resnlted in death of half the test population over the course of 96 hours) was 0.083-1.09 mgll for salmonids and 17 ....