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<br />
<br />net i c,analys is has greater powe rthan e lectrophoret i ci nvest i gat ion or exami-,
<br />nation of external morphology.' There are further applications of cytogenetics.
<br />Pollutants and radiation could be assayed by their effects on chromosomes
<br />(Kl t gehnanand B 100m,"1976) .Th i scoul d be used forenvi ronmentalmoni tori g
<br />or examining the consequerices of.habitatalterations,'such as oil shale develop-
<br />ment or nuclear waste disposal. Certain pathological condi tions in fishes couTd
<br />have a chromosomal basis, well-documented for humans (Swansonetal., -1981).
<br />A distinctive cytogenetic state would be usable as a hidden tag, allowing an
<br />investigator to follow stocks. Breeding programs could use cytogenetics .to'
<br />further guarantee the purity of stocks. In an evolutionary context, the
<br />genetic relatedness of stocks or species could be traced using cytogenetics.
<br />Thorgaard (1978) established relationships between rainbow trout (Salmo gaird-
<br />neri), as well as sockeye salmon (Oncorhynchus nerka), populations along the
<br />Pacific coast with chromosome analysis. Sex determination is another problem
<br />that, for some taxa, is resolvable with chromosomes. Sexual chromosomal hetero-
<br />morphy in mammals is well-known. A similar condition is recorded for rainbow
<br />trout (Thorgaard, 1978). Since chromosome characters are fixed at fertiliza-
<br />tion, sexes could be differentiated before the appearance of external secondary
<br />sexual characters. The study of chromosomes in fishes is still at an incipient
<br />level; however, the advent of better methodology will expand the capabil ity of
<br />the fishery biologist to study and manage stocks.
<br />
<br />!s
<br />
<br />>m
<br />
<br />ACKNOWLEDGMENTS
<br />
<br />:k
<br />
<br />The author gratefully acknowledges J. Valentine, D. Archer, and W. Miller
<br />of the U. S. Fish and Wildlife Service, Colorado River Fisheries Project, for
<br />financial support and specimens. O. Cuellar and K: Johnson, University of
<br />Utah, provided helpful criticism and comment on this work. Editorial assis-
<br />tance on the manuscript was given by L. C. Rosenfeld.
<br />
<br />s.
<br />
<br />L1TEAATURE CITED
<br />
<br />nd-
<br />ne
<br />
<br />B 1 axha 11, P. C.
<br />1 i terature.
<br />
<br />1975. Fish chromosome techniques -- a review of selected
<br />J. Fish Biol. 7: 315-320.
<br />
<br />: i-
<br />!ss.
<br />
<br />H~lden, P. B., and C. B. Stalnaker. 1970. Systematic studies of th~ cyprinid
<br />genus Gila in the up~er Colorado River basin. Copeia 1970~ 409-420.
<br />
<br />Hubbs, C. L., and K. R. Lag1er. 1964. Fishes of the Great Lakes Region;
<br />University of Michigan Press, Ann Arbor.
<br />
<br />
<br />nes.
<br />
<br />Kl igerman, A. D., and S. E. BloolT.I. 1976. Sister chromatid differentiation and
<br />exchanges in adult mudminnows (Umbra 1imi) after in vivo exposure to
<br />5-bromodeoxyuridine. Chromosoma 56: ~-109.
<br />
<br />
<br />
<br />o
<br />
<br />"",," ...
<br />
<br />Kl igerman, A..cO. ,and S. E. Bloom. ''t977. Rapid chromosome preparations from
<br />sol id~i~s~eso~.ljshes.,J.Fish. . Res. Board Can. .34:
<br />
<br />
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<br /><Ru i z,1. R. ,G. ,,'"J:M! "Cei s, and W."'B~c~k~'J982. -,Ch romosomalHl!vo1 uti on in,
<br />a1,1 iFi c,'popu1ations.o'f,the Odontophryn'usoccidenta 1 is 9 roup (Amph i b i a,' ~
<br />Ariu :f rOrTlwes ie" A.rgent ina::.Cy togel"let .Ce 11 ;G~net'1 ,33::' .~'303- 311,',c
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