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~ I t-~ , ICALl olN ICI~O"ETU. 10 100 '" 100 . IN 110 UTAH Figure 1. The hydrologic subregions of the Upper Colorodo River Basin. (After Joseph et 0/. 1977) (or circle) indicates point collections and suggests the species is incidental or extremely rare. Species that were locally abundant in a small tributary but rare elsewhere would appear so on the maps but might be classified in tables as rare for a sub-basin. The status of fishes is designated as: EN endemic - a species or subspecies found only. in the Colorado River Basin; NA native - a species or subspecies recent to the Colorado Hiver Basin but occur- ring there before introductions by man; EX exotic - a species or subspecies newly introduced into the Colorado River Basin (non-native); TH threatened - a species or subspecies which may become endangered in the near future; or ED = endangered - a species or subspecies in danger of extinction. The separation between native and endemic fishes is presented according to Behnke and Benson. (1980), whose treatment varied significantly from that of others (Kirch 1977). All endemic fishes are native; however, native fishes also include those species which have invaded the Upper Colorado River Basin naturally and were not introduced by man. Fishes are classified as threatened or endangered according to designations by the U.S. Fish and Wildlife Service (1973, 1974, 1980a, 1980b) or the State of Colorado (1980). Where these do not agree, the most restrictive classification is given. Information on distribution and abundance of fishes was obtained primarily from recent studies by the 0 Colorado Division of Wildlife and the U.S. Fish and Wildlife Service. The New Mexico Depart- ment of Game and Fish, the Utah Division of Wildlife Resources, and the Wyoming Game and Fish Dep.artment also furnished information. Other published sources were sought where recent collec- tions were unavailable. All such sources of informa- tion are referenced by sub-basin, tributary, or reser- voir. Scientific and common names of fishes were ob- tained from Robins et aL (1980) except for the bony tail, which we refer to as bony tail chub. Distribution maps contain both scientific and com- mon names in the order presented by Robins et aL (1980), except when the distribution of two species are combined on one map. Because source material (Table 1) varied widely in sampling design and effort, it was necessary to use judgement in many cases for designating relative abundance. Some incidental species may have been overlooked or unpublished collections not obtained. General RESULTS A total of 55 fishes (52 species and 3 subspecies) presently exist in the Upper Colorado River Basin (Table 2). Relative abundance of fishes found in riverine habitat is provided according to major tributary (Table 3). A list of' species found in major reservoirs (Table 4) and graphic displays of distribu- tion and specific locations for abundance (Figs. 2-46) are provided. Abundance designations for some species were difficult, and judgement was required in those in~ stances. An example of this is the fathead minnow, a widely distributed species that is abundant in backwater habitat throughout the system. Because this species was restricted largely to one habitat, it was designated as common. Other species, for exam- ple the red shiner, were also widely distributed but occurred abundantly in a wide variety of habitats (backwaters, shorelines, eddies, riffles). The red shiner was designated as abundant. Although reservoir fishes were not a primary ob- jective of this study, 42 species occurred in reser- voirs, with 7 species primarily restricted to them. Reservoirs in the Upper Colorado River Basin are managed primarily for exotic sport fishes; salmonids are in the upper zone, and primarily centrarchid and percid fishes are in the lower zone. Table 5 presents status for 42 exotic, 13 native, 8 endemic, 1 threatened, and 5 endangered fishes of 13