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48 Flagg (1981) suggested that exotic fishes carried pathogen groups that differed from those carried by native fishes. No diseases were apparently introduced to native fishes. Osmundson (1987) reported the first occurrence of Asian tapeworm in the upper basin. The parasite had been introduced from hatchery reared Colorado squawfish stocked into riverside ponds and indicated the potential for disease introduction from man-introduced fishes. Incidental take of endangered fishes by anglers was confirmed by several authors (Vanicek 1967; Wick et al. 1985; Osmundson and Kaeding 1989a; Tyus and Karp 1989) and up to 10% of tagged Colorado squawfish in the Green River have been caught by angling (Tyus and Karp 1989) leading some to believe it to be a serious problem. There is no evidence of habitat alteration by exotic fishes in the upper basin. Hybridization has not been documented between any exotic fish and the four threatened or endangered fishes. (2uestionnaire Background information established the nature and quality of the expertise comprised by respondents to the questionnaire. Most respondents had expertise as biologists, researchers, or managers and experience with threatened and endangered fishes, nongame fish, and sport fisheries. Much of the expertise was based on familiarity with the major rivers in the upper basin. Consensus or majority opinion was achieved on seven of the nine questions whose subject was common to all respondents (Questions 2, 3,5,6, 8, 13, 15, 16, 17). The remaining eight informational questions demonstrated a diversity of responses. The objectives of questions 2, 3, 4, and 5 were to determine if a problem exists, where it occurs, which species are involved, how native fishes are affected, and is the problem documented. Introduced species were considered by most respondents to impact native fishes in most rivers in the Colorado River Basin. One third of the respondents indicated the impacts have yet to be documented. Six species comprised of three traditional gamefish species and three nongame cyprinid species were clearly of greatest or more widespread concern. Criteria for concern due to these species were based on abundance (channel catfish, red shiner, fathead minnow, and common carp), predatory habits (northern pike, green sunfish), and the adaptation as an riverine omnivore (channel catfish). The remaining species that were ranked lower were considered to be problems more on a localized scale or in certain environmental conditions. Most respondents felt most introduced species affect native fishes through both predation and competition. They listed 19 of the 28 species in Table 3 as potential predators and 17 as potential competitors. Colorado squawfish, razorback sucker, the young of these two species, and all native fish larvae in general were most commonly identified in interactions with introduced species. While 77-81% of respondents considered introduced fish to be a problem and provided specific species and interactions, only 50-62% indicated documented evidence existed. References cited totalled only 10 sources for predatory interactions and much fewer for competitive interaction. This 1 1 j