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183 <br />.r <br />"~TA'~?AGEP,~"dT PL_ArT FOR TFW F.A20RBACK SUCKER (;~YI~.~IUCI~N TE'•fAn'US~ <br />IP1 CAI,IFORdIA <br />Linda C. Ulmer <br />Fishery ?3iologist <br />California Department of risk and Game <br />Region 5 <br />ABSTRACT <br />Historically the razorback sucker eras the most abundant fish species in <br />the low Colorado River. Since the late 1950's physical, chemical and bio- <br />logical alterations of the lower river ecosystem have resulted in a si;nif- <br />icant decline in population numbers. Today, althouh .remnant populations are <br />found in the mainstream storage reservoirs and in Sen~:tor ':+'ash Reservoir, <br />Imperial County, CA there is no evidence of successful recruitment. In the <br />riverine sections and canals of the lower river bordering California only 33 <br />razorbacks, all adults, have been collected since 196;'. In 1984-1985 seven <br />sub-adults, less than 356 mm total length, were taken Arom equalizing reser- <br />voirs off the Coachella Caral in Imperial County, CA. This collection~ind~cated <br />possible mainstrem spawning in the Imperial Division of the lower river. <br />In 1985 the State of California approved a management plan for the razor- <br />back. This plan is based on a decade of reintroduction and research program <br />data and retiresents a viable and conservative approach by which th ~ ger <br />.~is.h-mayLhP recover~d~ith;n hi Q+~r,.. n~~ , fs,~,ia habit s. In the winter of <br />1986 California ~`epartment of Fish and Game in association with the U.S. Fish <br />and ~7ildlife Service will initiate a ten year reintroduction and monitoring <br />program iri the lovrer Colorado River. .Yithout this effort this once-abundant <br />native suecie~ vrill continue to decline until ertiiiction. <br />