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<br />Aquatic Sciences
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<br />tential for permanence as might a continuing "trickle" from
<br />a separate source. In I l)(Jl). managers inlroduced striped bass
<br />into Lake Mead, primarily because largemouth bass popula-
<br />tions had declined significantly. A stocking program for rain-
<br />bow trout (Oncorhyne!J/Is II/ykiss) and other salmonids was
<br />initiated the same year. Striped bass reproduction upstream
<br />from Lake Mead was reported in 1973.47.4H The trout fishery
<br />was successful through 1975 but essentially collapsed in 1976.
<br />Introduced striped bass first impacled the forage base (threadfin
<br />shad), resulting in adverse effects on trout condition and size;
<br />striped bass had little alternative than to begin feeding on
<br />troUt.4HAY The collapse of the forage base and decline of the
<br />trout fishery was initially attributed to the introduction of striped
<br />bass.4H Striped bass simililarly impacted the forage base in
<br />Santee-Cooper Reservoir, South Carolina, the first site of im-
<br />poundment of striped bass in a reservoir. ,0 Therefore, such a
<br />possibility in Lake Mead could have been anticipated.
<br />Investigations on fish population biology in Lake Mead by
<br />Paulson and Baker" have indicated thaI the collapse of Ihread-
<br />fin shad in Lake Mead may not have been due solely to pre-
<br />dation by introduced striped bass. Their studies indicated that
<br />more recenlly completed upstream reservoirs, Lake Powell on
<br />the Colorado an~J:;lamine Gorge on the Green River, b~e
<br />nut~ienl.!I.fWs, thus depriving thr~adfin shad oLplankJ9JLfQr~
<br />u~which they depend. In 1987, liquid fertilizer was applied
<br />into the Overton Arm of Lake Mead in an attempt to reslore
<br />the shad population,52 and initial indications are that this effort
<br />is working 10 restore the forage base. A better understanding
<br />of the nutrient base, its cycling and relationship to threadfin
<br />shad prior to attempting introduetion of striped bass, and per-
<br />haps trout, into Lake Mead might have avoided these problems,
<br />especially considering dam construction upstream had already
<br />occurred. The introductions, however, were made because they
<br />probably appeared to be a good substitute for determining and
<br />perhaps correcting the causes for decline of largemouth bass
<br />populations.
<br />~ allay fears of negative impacts on trout expressed by
<br />\ concerned trout fishermen on Lake Mohave below Lake Mead,
<br />!!lanagers who introduced strip~ti bass to Lake Mead stated
<br />that striped bass would not survive passage through the turbines'
<br />of Hoover Dam. Easterners may rememher a similar conten-
<br />tioll, at about the same time, that striped bass popul,ltiolls in
<br />the Hudson River, New York, would be adversely impacted
<br />by pump and turbine impellers at the Storm King Mountain
<br />project. In 1981, however, scarred, adult striped bass began
<br />to appear in Lake Mohave, and young-of-the-year, possibly
<br />hatched in Lake Mohave, were first found there the same year
<br />and in every year since. 53 Either this species is now established
<br />in Lake Mohave (reproduction has not yet been documented
<br />there) or there is an annual supply of young enlering Lake
<br />Mohave through penstocks of Hoover Dam." Thus, anotheL
<br />claimed "contained" introduction did not occur as most have
<br />"~and future managcment of hoth game and Ilollegame fishes
<br />
<br />below Lake ("lead has allot her factor, slr:p'~d bass, to contend
<br />with.
<br />The most-recently completed (1l)(J2) big reservoir 011 the
<br />Colorado River, Lake Powell, lies at the base or the Upper
<br />Colorado basin (,In the Arizona-Utah border. Like other rcs-
<br />ervoirs downstream, Lake Powell hosts a mostly introduced
<br />fish fauna. The forage base for sport fishes in Lake Powell.
<br />particularly for striped bass introduced in 1974, has been
<br />threadfin shad, which were themselves introduced in 1968 to
<br />1969. Claims were made in 1974 that striped bass \vould nQt
<br />reproduce in Lake Powell,s~ which we find astounding became
<br />their reproduction iust above dowstream LLlke [vIead was kno~1
<br />~.47 Catch size of striped bass in Lake Powell initiaily
<br />increased, dramatically, but has been decreasing since 19S4.
<br />and threadfin shad populations also decreased, attributed to
<br />predation on shad by striped bass. ,. Instead of trying to 0(....
<br />with the management problem of decreasing shad production
<br />.md a declining sport fishery on an ecological or limnologicd
<br />basis, as is apparently happening in Lake Meld. the U::,h
<br />Division of Wildlife Resources developed J proposal to intro-
<br />duce rainbow smelt (Oslllerl{~n~ordax) into Lake PQ\.vell ~:s a
<br />forage base in addition to thread fin-shad . ~.j Utah's proposal is
<br />based on a premise that larger predators, such as striped bass
<br />and walleye (Stiz~s[~di()..!l l'i!rellln:j!'!!.!-tn;), would shift to feed
<br />on smelt. Only centr<lrchids would utilize threadfin shad. leau-
<br />ing to a shad popubtion recovery. This proposal (<Ime to the --
<br />authors' attention only 3 months after the Chid of Fisheries
<br />of the Utah Division of \Vildlife Resources (UDWR), in a
<br />personal communication, that nonnative fishes would no, be
<br />introduced to Utah waters in the future. Utah has also intro-
<br />duced the crayfish, Orcull('c/<:s\'ir~is, bolh in the C010::lC;O ....
<br />and Bonneville systems. Anglers ha\e mo\'cd the crayri.<l
<br />around, and UDWR and the U.S Fish and Wildlife Service
<br />planted them in northwestern Utah." This crayfish is 1,0\'"
<br />round throughout much of the stale and has resulted in decliile
<br />of growth of rainbow trout by altering the food web. It \\':\s
<br />further suggested that, "The inability of rainbow troul to ef-
<br />kctively consume crayfish.. .may require the introduction of
<br />other species to prey on Ihe crayfish... ,,'s This tiering of in-
<br />troductions is neither new, nor procedurally sound. It is rem-
<br />iniscenl of the childhood story, "The King, the 1\1ice and the
<br />Cheese. . . ",
<br />Because rainbow smelt have been used elsewhere as a for:lge
<br />base for trout and other fishes, including walleye, one might
<br />expect that Utah would have learned from experiences of other
<br />states. First, rainbow smelt generally remain below the hy-
<br />polimnion; predators that feed on smelt, therefore, can be pre-
<br />dicted to leave surface waters to feed, resulting in a lower C:ltch
<br />rate, particularly by fishermen v,,'ho arc used to fishing shal-
<br />lower waters for striped bass and I:tck gear for deeper fishing.
<br />Second, rainbow smelt arc-k.nill-vn to feed on eggs and Ian~
<br />~ other fishes, including their own, and may have been o~
<br />of the callses for the decline of walleye in Lake Sabkawea,
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<br />1989
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<br />163
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