Biochemical Genetic Detection of Natural and Artificial Hybridization of Chinook and Coho Salmon in Northern California

Abstract

Allelic products of seven isozyme loci were used to identify presumptive hybridization between chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch in northern California. First-generation hybrid salmon (N = 3) were observed in samples from a tributary creek to the Trinity River; from rearing ponds at Camp Creek, a tributary to the Klamath River (N = 14); and from the ocean salmon fishery near Eureka (N = 2). The sample from the Camp Creek rearing ponds consisted of progeny from an inadvertent cross of coho and chinook salmon by hatchery personnel at the Irongate Hatchery. In addition to the artificial production of hybrid salmon at Irongate Hatchery, the alteration of traditional salmon spawning routes by Lewiston Dam on the Trinity River may have lead to natural hybridization between chinook and coho salmon in Deadwood Creek. Accurate quantification of the occurrence of hybridization was impossible due to nonrandom sampling of populations, but we presume to have underestimated the actual hybridization between these two species.