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(~) (,:, I ('.) , ,.1 , ( ) m ) ; ~! . ~, '. -) '~ " .;. '.' '" , " " " ",1 ':':; .:\ '. ..S ". ? '. ; INTRODUCTION Historical surveys of fish fauna have been conducted on most major tributaries of the upper San Juan River (Smith 1976, Anderson et al. 1993), Fish surveys that were conducted prior to 1970 are rare, however during the 1970's fish surveys became much more common and expanded into most drainages (Table I), Only well documented surveys are presented in this study, although there have been numerous unconfirmed or "hearsay" reports, Most of the unconfirmed reports suggest that the native fish were once more numerous and widespread in distribution (Koster 1957), Some of the fish surveys presented here support this premise, In most cases historical surveys of fish fauna document the introduction and distribution of non-native fish species, Data for this report were supplied by the Colorado Division of Wildlife, New Mexico Department of Game and Fish, U,S, Fish and Wildlife Service, Utah Department of Wildlife and Southern Ute Indian Tribe. The objectives of this report were: I) to compile historical fish collection information for the tributaries to the San Juan River downstream of Navajo Dam; 2) compile data collected as part of this project during the years 1992 - 1994; and 3) to compile, as practicable, collections made upstream of Navajo reservoir during the study period 1992 - 1994. Many of the fish collections that have occurred since 1994 are included in this report, however, these were not included as part of the original scope of work or objectives for this project. The primary objectives and goals of biologists have varied since fish fauna sampling began in this drainage. Many of the early objectives included the eradication of native fish species, and the introduction of non-native game species, Olson (\962a) reported that lethal levels of rotenone were used to eliminate native fish from sections of the Los Pinos, Navajo, and San Juan rivers, Several other reports from this time period recommend that non-native species be stocked in Navajo Reservoir and nearby sections of the San Juan drainage (Olson 1 962b, Olson 1967, Graves and Haines 1968). Graves and Haines (1969) reported that prior to 1969, five non-native species including more than I million channel catfish and 4 million rainbow trout had been stocked into Navajo Reservoir. In fact, most of the sampling and fish related work prior to 1970 was directed toward the introduction of non-native fish or removal of native species. Native fish were often not reported during these early sampling events. After the late 1960s, the objectives for most fishery work in the San Juan drainage began to change. Although game fish species were important in many areas, the preservation of native species became an important objective as well. Smith (1976) conducted one of the earliest fish surveys that emphasized native and non-native fish populations, ,This work was followed by numerous studies that were designed to account for native as well as non-native species (Sublette 1977, Robertson 1977, Platania and Bestgen ] 988, Platania 1990, Platania and Young ]990, Anderson. et al. 1993, Miller et al. 1995), Most fish fauna studies since the mid-1970s have emphasized the need for research involving native species. Draft Final Tributary Report Miller Ecological Consultants, Inc. Januar}' 31, 2000 Page I