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Sew ~. research facilities for laboratory )studies. Fish stocking programs can benefit management for recovery, but only in coordination with a comprehensive program in which life requirements of target species are well understood, and these requirements provided. If habitats have not improved, reintroduction of fishes `into them should be considered only stop-gap measure (Rinne et al. 1986). i ~.`-Z~~~~~~'~ p~diec,~~ev.. ~-~4~~. iw Y.ql~~~ ~ ~ w~,~. G~Q,~n4,~'~c. r~~o~kt VM~L~' ~kj~ :~l"Cw ~r~w.2~r caN,s~~2Ti~ lf~ Stocking of Colorado squawfish for recovery has not been attem~ed for qNy the Green River basin because of the naturally reproducing population there. 5~-0 ~~iµS Re-introduction of Colorado squawfish into areas of the lower Colorado River ~-,~,~~-~l, basin from which they have been extirpated, was initiated in 1985 by the Arizona Game and Fish Department, and USFWS- Dexter National Fish Hatchery (Hendrickson and Brooks 1987). It is too soon to determine-the success of that endeavor, but it is doubtful if stocking alone will be sufficient to recover the squawfish there. Indeed, the complex life cycle of the Colorado squawfish, in which there are spatial separations of life stages, ~ ~- incorporation of an energetically-costly migratory behavior, and other ~ov ~^- components (Tyus 1986, 1990) suggests that stocking programs can only be ~ ~~ ~,~ successfulif life history attributes are understood and considered. ~ ~ ~~~5 Stocking of razorback suckers have been initiated in the Green River, ~a~ but as yet this is only being done to augment a non-recruiting population ~~~ \~ v--- (Lanigan and Tyus 1988, Severson et al. 1989). ~1 Non-native Species and Sportfishing ~~v~~l~a~w~- Stocking of nonnative, warmwater species ha bee reduced in the upper Colorado River basin recent years, and under the R would not occur in watersheds occupied by listed fishes. The reverse of stocking, elimination or removal of non-natives, is worth considering, but this issue has not been meaningfully addressed. Introductions of non-native fishes into habitats occupied by native fishes is not usually accompanied by a positive affect on native fishes, especially if habitats have been altered. Direct effects include: Elimination, reduced growth and survival, changes in community structure, and no effect (Moyle et al'. 1986). In addition, fish are usually introduced into habitats that are changing due to the effects of man, making it difficult to determine if habitat change, competition, or both, are responsible for declines that are noted in the native fauna. This already complex issue is further confounded by past introductions into waters in which species interactions were not well understood, and were usually not subsequently studied. Thus, impacts of introduced fishes on native populations are seldom understood. Because it is difficult to assess such impacts, and the effects are usually inferred from major alterations of species composition. Competition between native and introduced forms is difficult to observe experimentally, and perhaps impossible to prove in natural riverine habitats. The introduction of non-native fishes in the Colorado River has been documented by many, and some data on their present status provided by Minckley (1982) and Tyus et al. (1982). Competition of these non-natives with Colorado squawfish has been proposed by various workers (Behnke and Bensen 1983; Holden and Wick 1982; Osmundson 1987). Predation of introduced fishes on razorback 7