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CDOW -BRUSH TEL No.303- 842 - 2849 Apr 10,92 14:09 No.003 P.04 <br />PAGE 3 - UPPER COLORADO T &E FISH HEALTH CONCERNS <br />Sacramento squawfish (continued): <br />Leeches 1 <br />Copepod crustacean 1 <br />Northern squawfish (P. oregonensls) <br />Trematoda 5 <br />Cestoda 3 <br />Nematoda 5 <br />Acanthocephala 1 <br />Leeches 1 <br />Mollusca 1 <br />Copepod crustacean 2 <br />Utah chub (Gila atrada) <br />Trematoda 9 <br />Cestoda 6 <br />Nematoda 4 <br />Acanthocephala 2 <br />Copepod crustacean 1 <br />It can be assumed that a detailed study of the parasites of <br />Upper Colorado River Basin T &E species would produce similar lists. <br />The effects of various parasites on their fish hosts are in many <br />cases still unknown. An ever increasing number of papers are <br />showing that many detrimental effects such as disadvantageous mate <br />selection, longevity and growth rate are.subtle and very difficult <br />to measure. However, a few metazoan fish parasites - usually those <br />with a broad host range - cause well - dosumented pathology in <br />certain host species. It is these that warrant discussion here. <br />The Asian tapeworm Bothdocephalus opsarlchthyidis (a. k. a. B. gowkongensis, B. <br />achellognathl, B. opsalichthydis) has been found in Colorado River squawfish <br />and fathead minnows in gravel pit ponds in the Grand Junction area. <br />It is believed that the source of this tapeworm was either Dexter <br />National Fish Hatchery, where the parasite is known to have been <br />present since 1981, or possibly from one of the sources of fathead <br />minnows introduced to the ponds as forage for the squawfish. <br />Although it has not been confirmed, the worm may by now also be <br />present in feral squawfish and other species in the Colorado River <br />itself. <br />The Asian tapeworm is believed to have been introduced into <br />North America in the 1960s via infected grass carp. It is a large <br />and fast - growing adult tapeworm parasite of fishes with little if <br />any host specificity within the families Cyprinidae, Catostomidae <br />and Cyprinodontidae. Pathology and often mortalities have been <br />recorded in many new host species in North America as the worm has <br />41 steadily expanded its range. The specific effects on Basin T &E <br />species have not been recorded. <br />The Colorado Division of Wildlife for a time attempted to <br />