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Reviews In cumplic;lted through private introductions, although other agencies (local, state, or federal) may have been involved with releasing tilapias or supplying them to individuals. Ill. Ti:::: LEGp,CY OF THE SALTON SEA E}( f.\ PIi ~:) ~_ E Some other western states, seeing the success of the reere- ~Hional sport fishery created in the Salton Sea during the 1950s, attempted to introduce some of the same marine fishes into brackish water lakes; we term this "copycat management". The number of failures was exceeded only by the costs of such efforts. Had they conducted chemical and physical analyses on their waters, as did California prior to stockings, those i;itroductions might not have been attemflted, saving state and kderal agencies (and ultimately taxpayers) considerable expenditures. Ti1C Texas Department of Parks and Wildlife began con- ducting introductions of scveral marine fishes into inland waters in the 1950s and 1960s, a program that was greatly expanded in ['ie 1970s and 1980s. One of the fishes introduced into the S;liton Sea in the 1950s, in small numbers and typically with other sciaenids, was the presently endangered totoaba (TolOaha mCl::donaldi), an important commercial and sport fish from the Pacific coast of rv1exico;23 its introduction failed. Nonetheless, an lOng those fishes proposed for importation to Texas in 1984 \':as the totoaba, under the guise of protecting an endangered sjJCl.ies. f,,1any ichthyologists and fishery biologists objected to this proposal, suggesting that Texas was seeking introduction of this giant sciaenid for Spol1 purposes, and Mexico refused (a supply specimens. Failing in that effort. Texas succeeded in obtaining orangemouth corvina from California, hybridized it \vllh spotted seatrout (CYlloseiollllebllloslIS ). and introduced the hybrids and both parent species into reservoirs, mostly \vhere tilapi,ls were to be used as forage. 35 The spotlcd seatrout X oi"angemouth corvina hybrid was very successful and more co iLl tolerant than orange mouth corvina, and the hybrid and both pacnt stocks persisted.36 Texas has had a history of "try it and see if it works" management by introducing marine and m::ny other nonnative fishes into inland waters, which certainly qualifies as a no management plan. The situation in Texas is vcry different from that of the Salton Sea: because the primary goal is supplying new sport fishes, typically predators. possible diquptions of previously existing sport fisheries, forage bases, and perhaps nativc fish populations can oC\2ur. The Texas use of hybrids between exotic.C. xall/IIlIIIIS and iElive C. lIebllloslIS, an important food fish around the entire Gulf of Mexico and the eastern seaboard as far north as New York, is pal1icularly disturbing. Similarly, Texas has intro- duced intergeneric hybrids of red drulll (Sciacllops OCl'lIallls) :1fld black dnlIn (Pogollias crOll/is) into reservoirs. If success- fully established, inlrogrcssion and modificllio!1 of the gene sIC:'!.:: of imf10rtailt n:l~ive species could result. Such genetic ..l .,,") dilution has occurred in the white ibis (ElldocilllUS alblls) pop- ulation in southeastern Florida, which bred with scarlet ibis (E. mbcr), introduced from South America. There is no in- formation on the adaptive consequences of such unintended genetic experiments, to which we will return later. IV. MANAGEMENT OF COLORADO RIVER RESERVOIRS Closure of Hoover Dam in 1935 began a period of change in the history of the Colorado River and its fish fauna. Dam after dam was built downstream, followed by channelization and dredging activities. Fishes that historically thrived in flow- ing water, with periodic high flow rates and increased sediment loads, had "plup"', crealing decreased flows and turbidity, imposed on them. Dams on the Colorado River presently con- trol flow rates to occasionally the point of no flow.]7 With reservoirs behind new dams came introductions of nonnative fishes. To fishery managers, reservoirs are a challenge. Some river- ine fishes may thrive in lacustrine conditions, but others may not. Where managers and immigrants from eastern states con- sider large cyprinids and both large and small catostomids to be' 'trash fish", the challenge became even greater. Lake Mead was initially stocked with nonnative centrarchids (largemouth bass [MicI"IIJ!tcms .wl/l/oidcsl, bluegill [LcJ!oll1is II/acrochims[, black crappie I/JoII/oxi.1 nigrolllllculal/lsj) and channel catfish (Ieralllms lilli/Cia/Us). A respectable sport fishery resulted. Red shiner (Nolropis III/rel/sis) were introduced into Colorado River waters as forage, in waters south of Lake Mead. in the early and mid-1950s,.\X bter reaching Lake Mead via bait buckets. This common and unfortunate practice of fishermen releasing bait resulled in establishment of red shiner in Lake Mead. Red shiners have had adverse impacts on sevcral. Ill;W endangered fishes in both the Moapa River and Virgin River, which drain into Lake Mead's Overton Arm."'." In 1953, Lake Mead was stocked with threadfin shad (D. J!l'iCIICIISC) to supplement the for;lgc basc for largemouth bass..'~ That introduction. howevcr, was only temporarily successful and improved the sport fishery for I argemout h bass unt i I 1960. .1,' Reservoirs downstream from Lake Mead also underwent introductions and doubtless re- ceived some escapes from earlier Lake Mcad stockings. Stress from changes in historical !low pallerns. coupled with preda- tion and perhaps other behavioral impacts from introduced fishes, brought about a sharp decline in survival and recruit- ment of native fishes in the lower Colorado basin. Beginning in 1959 and periodically through the 1970s. striped bass (Mo/"(}J/c .w.llIlilis) were introduced into the lower Colo- rado River below Lake Mead.,II,I(. Specimens were caught as far dowllslrc;ull as the llnpcrial Division. but Ihe species faikd to establish. although some evidence of reproduction was found. ~"..I" Periodic releases, however, may not have the po- Volume I, Issue 1