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<br />Aquatic Sciences
<br />
<br />been increasing, due in large part to inflows from agricultural
<br />drains.,,,.'7
<br />EvermannlH recorded the fish fauna of the newly formed
<br />Salton Sea as consisting of common carp (Cyprilllls carpio).
<br />bony tail (Gila robllsfa 1= G. elegalls]), razorback sucker (X)'-
<br />rlIllcllen /exanlls), rainbow trout (later determined by Miller''!
<br />to be the Colorado River cullhroat trout [SallllO clarki plell-
<br />ri/ic/ls]), striped mullet (Mllgil cepllallls), and desert pupfish
<br />(Cyprinot!on maclllarills). All species had come from the Col-
<br />orado River. By 1929, carp, bony tail, and razorback sucker
<br />had disappeared; eullhroattrout persisted, but in reduced num-
<br />bers; mullet had declined (a result of their being unable to
<br />migrate to the sea); and desert pupfish were common.20.21
<br />The first "wave" of introductions began in 1929, the year
<br />in which mosquitofish (GallllJ/lsia a[finis) were first found (and
<br />already becoming abundant) in shallows along the sea. Striped
<br />bass (Morllnc sa.wtilis) were stocked in 1929 and 1930 but
<br />failed to survive. In 1930, a goby, the longjaw mud sucker
<br />(Gillicllthys mirabilis), was brought from San Diego Bay and
<br />became established. In 1934, coho salmon (Ollcorh\'llcllllS kis-
<br />II/ch) were introduced, but failed,21 doomed because of the
<br />warmth of waters of the Salton Sea. This period of initial
<br />introductions included releases of a polychaete annelid (Nc(/lIrhes
<br />sllccinea) and a ghost shrimp (Ca!iall(/ssa sp.) from San Diego
<br />Bay; only the polychaete survived.22
<br />Following World War II, a second set of introductions was
<br />initiated by the California Department of Fish and Game. Be-
<br />ginning in 1948 and ending in 1956, a total of 33 species of
<br />marine fishes was released into the Salton Sea.2' A II but two
<br />of these were brought from San Felipe, Baja California del
<br />Norte, Mexico, on the Gulf of California; the two that origi-
<br />nated elsewhere were northern anchovy (Ellgmlllis mordax)
<br />from Los Angeles Harbor and anchoveta (Cerengralllis IIlYs-
<br />/iccllls) from an undesignated location on the Gulf of California.
<br />Walker et al.21 termed these efforts "of the shotgun type."
<br />Indeed, the stocking agency was clearly attempting a "try this
<br />and see if it works" approach which has typified many intro-
<br />ductions. The I ist of fishes introduced, 2\ however, indicates
<br />dominance in numbers of certain species. For example, both
<br />the 1948 and first of four 1950 stockings included a total of
<br />6000 anchoveta, evidence of an attempt to establish a forage
<br />base for other fishes introduced later. Anchoveta failed, prob-
<br />ably because they, themselves, had no persistent forage base.
<br />Beginning in 1950, predatory species dominated by sciaenids
<br />were released.
<br />Of the 33 species introduced, only three became established,
<br />a haemulid, the sargo (Anisotremlls davidsoJ/i), and two sciaen-
<br />ids, bairdiella (Bairdiel/(/ icistia) and orangemouth corvina
<br />(Cynoscion xantlwllls). Native desert pupfish persisted, as did
<br />the longjaw mudsucker introduced in 1930. One other, thread-
<br />fin shad (Doroso/lla petenense), entered through irrigation ca-
<br />nals from the Colorado River and persists in the sea. 2.1.2) Among
<br />the few invertebrates present arc the polychacte N. .I/lcciIlC(/
<br />
<br />and a b,irIwcle (Baloll/ls Wl1fJ/iiiriie), t:,c ;"ic':'. r".\)11,li1;Y ilLi()-
<br />duced in the 1940s or early 1950s from cither tllC CalifOii1;,l
<br />coast or the Gulf of California.2:
<br />This "shotgun" effort was a good m'll1~lgCIl1C. Ilt ap.proaCh il~ )
<br />a body of water where, In terms of essentially ,!bscnt natl\'C
<br />fauna or flora. there was nothing to losc aml eVCfything to
<br />gain. Seemingly, all suitable and important parts of a marine
<br />ecosystem were moved into a VIrgin, essentially marine en-
<br />vironment. Sargo and particularly bairdiella, whieh ate the'
<br />depauperate invertebrate fauna, formed thl~ forage hase for
<br />orangclllouth corvina. The result was establishment of a viabk,
<br />important sport fishery that has largely persisted in a relcltively
<br />unchanged manner since, turning an otherwise "dead sea"
<br />into productive waters.
<br />In the early 1970s, however, some additional exotic fishes
<br />began to appear in agricultural drains around the Salton Sea.
<br />Among those was the redbelly tilapia (Tilofli(/ zilli), apparently
<br />introduced for biological control 0'. aquatic weeds2.'.2" and per-
<br />haps to reduce mosquitos and chironomid midges. 27 Redbelly
<br />tilapia did not invade the Salton Sea. In 1964, Mozambique
<br />tilapia (T. /J/os.w/J/bica) were found to be established in a pond
<br />and a drain on the eastern side of the sea - an escape from
<br />a tropical fish farm. It was suggested that they could enter the
<br />sea and survive there.2H
<br />Mozambique tilapia were common in the lower Colorado
<br />River before the 1970s, including the water intakes for Imperial
<br />Va1ley, which begin near Yuma, Ariwna2'!,v, They probably
<br />entered the southern end of the Salton Sea via the Alamo and
<br />All American canals, remaining undetected there for several
<br />years. This species was more widely released after 1976 in the
<br />Imperial Valley for aquatic weed control, c,,1 and by 1971) it
<br />was found established in the Salton Sea.'2 By 1980, it, or what
<br />was then believed to be an unknown tilapia hybrid, had beCOJ1l'2
<br />a dominant, apparently permanent part of the ichthyofauna of
<br />the sea; electlOphoretie studies by the U.S. Fish and Wild!ik
<br />Service have confirmed that this tilapia is indeed the 1\107-
<br />ambique tilapia.'~ Although the population of tilapia in the sea
<br />has become massive, particularly in warm weather, it d(1cS not
<br />appear to have thus far adversely impacted other introducl'd
<br />fishes. In fact, a recreational fishery for tiLIpia has developed.:;
<br />Some concern had been expressed that bairdiella had decreased
<br />substantially, attributed to massive population increases of
<br />Mozambique tilapia,'~ but observed decreases appear 10 have
<br />been a normal, seasonal phenomenon." Desert pupfish ['op-
<br />ulations, however, mostly collapsed, probably due to predation
<br />by mosquitofish, perhaps predation and compclitilln from in-
<br />troduced sailfin mollies (Poecilia la/ipil1lw), and competition
<br />from juvenile Mozambique tilapia.~' The pupfish is now fed-
<br />erally listed as endangered.
<br />Future viability of the recreational fishery for the sargo and
<br />sciaenids in the continuing presence of tilapias in the S,tltOI:
<br />Sea remains speculative. This represents a situation where good
<br />management through agency-sanctioned introductions has [)IXII
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<br />1989
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<br />151
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