Genetic Purity of Paiute Cutthroat Trout Oncorhynchus clarki seleniris Populations in the Silver King Creek Drainage, Alpine County, California

For more information contact: jfcordes@ucdavis.edu

Collaborators

    This project is being done in conjunction with and is funded by the California Department of Fish and Game (CDFG) and the U.S. Forest Service (USFS).

Background and Significance of Study 

    First described by Snyder (1933), Paiute cutthroat trout (PCT) in Silver King Creek were distinguished from the Lahontan cutthroat native to the rest of the East Carson River drainage based on the near-absence of body spots (Benke 1965). After introduction of rainbow trout and Lahontan cutthroats into the Silver King Creek system in the 1940’s and 1950’s, a number of attempts to halt contamination of the Paiute cutthroat gene pool through introgression with these introduced species were made (see Ryan and Nicola 1976, Busack and Gall 1981 for reviews), with varying degrees of success. 

    The objectives of the proposed study are 1) to use highly variable nuclear DNA markers (microsatellites) to characterize genetic variation and stock structure in Paiute cutthroat trout populations in the Silver King Creek drainage and a number of out-of-basin transfers, and 2) use a single copy nuclear (scnDNA) marker to look for evidence of hybridization with introduced rainbow trout. 

Materials and Methods

    Sample Collections. Fin clips samples of Paiute cutthroat will be collected by California Department of Fish and Game personnel from various sites in the Silver King Creek drainage.

   Genetic Analysis. Whole genomic DNA will be isolated from fin clip samples using standard protocols. Microsatellite loci previously shown in this laboratory to be polymorphic in various lineages of the rainbow trout (O. mykiss spp.) complex will then be amplified from the isolated DNA samples via the polymerase chain reaction (PCR). Differences in the presence/ absence and frequencies of alleles will be used to assess population structure in Paiute cutthroat trout. A PCR-amplified scnDNA marker will be used to investigate the possibility of Paiute cutthroat/rainbow trout hybridization.

Recent Results

   Results of this study were presented as a report to the California Department of Fish and Game Threatened Trout Committee (Israel et al. 2001) and were published in 2004 (Cordes et al. 2004). No evidence of rainbow trout introgression was found in any of the PCT populations based on the scnDNA marker and 4 microsatellite loci. Average genetic diversity in Paiute populations was generally low, probably a result of small historic population sizes and repeated chemical treatment and subsequent restocking of many of the populations.  Genetic relationships among populations closely reflected the stocking history of PCT.

Literature Cited

Benke, R.J. 1965. A systematic study of the family Salmonidae with special reference to the genus Salmo. Ph.D. thesis, University of California, Berkeley, CA. 273 p. 

Busack, C.A., and G.A.E. Gall. 1981. Introgressive hybridization in populations of Paiute cutthroat trout (Salmo clarki seleniris). Can. J. Fish. Aquat. Sci. 38: 939-951. 

Cordes, J.F., J.A. Israel and B. May. Conservation of Paiute cutthroat: the genetic legacy of population transplants in an endemic California salmonid. CA Fish and Game. 90-101-118 (pdf).

Israel, J.A., J.F. Cordes, and B. May. 2002. Genetic divergence among Paiute cutthroat trout populations in the Silver King Creek drainage and out-of-basin transplants. Report to the California Department of Fish and Game Threatened Trout Committee. February 2002. 20 p.

Ryan, J.H., and S.H. Nicola. 1976. Status of the Paiute cutthroat trout, Salmo clarki seleniris Snyder, in California. Calif. Dep. Fish Game, Inland Fish Admin. Rep. 76-3: 56 p. 

Synder, J.O. 1933. Description of Salmo seleniris, a new California trout. Proc. Calif. Acad. Sci. 20: 471-472.  

Last Updated: 11/04/02