| High Incidence of a Male-Specific Genetic Marker in Phenotypic Female Chinook Salmon from the Columbia River James J. Nagler,1 Jerry Bouma,1 Gary H. Thorgaard,2 and Dennis D. Dauble3 1Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, Idaho, USA
2School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington, USA
3Battelle Pacific Northwest National Laboratory, Richland, Washington, USA Abstract
Numerous populations of anadromous salmonids in the northwestern United States have been declining for many years, resulting in Endangered Species Act listings and in some cases extinction. The degradation of river ecosystems has been proposed as one of the major reasons for the inability of salmon to maintain their populations. However, the specific factors interfering with the reproduction and survival of salmon during the freshwater phase of their life cycle have not been fully described. This study was initiated to determine the incidence of phenotypic sex reversal in wild, fall chinook salmon (Oncorhynchus tshawytcha) that returned to spawn in the Columbia River. Fish were sampled at different locations within this watershed to determine whether they were faithfully expressing their genotype. We report a high incidence (84%) of a genetic marker for the Y chromosome in phenotypic females sampled from the wild, which was not observed in female fish raised in hatcheries. It appears likely that female salmon with a male genotype have been sex reversed, creating the potential for an abnormal YY genotype in the wild that would produce all-male offspring and alter sex ratios significantly. Key words: chinook salmon, genetic marker, genotype, phenotype, sex linkage. Environ Health Perspect 109:67-69(2001) . [Online 15 December 2000] http://ehpnet1.niehs.nih.gov/docs/2001/109p67-69nagler/ abstract.html Address correspondence to J.J. Nagler, Department of Biological Sciences, University of Idaho, Moscow, ID 83844-3051 USA. Telephone: (208) 885-4382. Fax: (208) 885-7905. E-mail: jamesn@uidaho.edu We thank the staffs at the Washington Department of Fish and Wildlife and Dworshak National Fish Hatchery for assistance with sample collection. J. Cloud, H. Wichman, and J. Bull provided critical comments on the manuscript. This research was supported by a University of Idaho Seed Grant to J.J. Nagler. Received 29 June 2000 ; accepted 7 September 2000.
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