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Abstract
Fish of the Chung-Kung stream of Miau-Li County, northern Taiwan, were sampled on seven occasions from March 1994 through to August 1995. A total of 45 species belonging to seven orders and 25 families were caught at 6 sites along the stream. There were ten species of Cyprinidae, and four or fewer of the other 24 families. Major species found upstream at site F were Varicorhinus barbatulus and Hemimyzon formosanum. This section of the stream is considered unpolluted if these water quality sensitive species are present. Acrossocheilus formosanus and Crossostoma lacustre can thrive in slightly polluted water and occurred in the middle reaches at site D. Zacco pachycephalus could also survive in mildly polluted water and occurred at site C. the major species at site B were tilapia (Oreochromis hybrid species) and thus this section was considered heavily polluted. Site A in the lower, tidal, reaches contained species of Mugilidae and was considered as moderately polluted.
Thirty seven fish muscle samples were analyzed for residues of nine organochlorine pesticides. Only 4-4′DDD was detected in the majority of the samples (70%). Trace amounts of heptachlor-epoxide, endrin, 4,4′ DDT (> 10 ng g−1) were found in 13-23% of samples. These low levels were considered a persistent residue of the use of organochlorine pesticides before they were banned 20 years ago.