Genetic Analysis of Trout (Oncorhynchus mykiss) in Southern California Coastal Rivers and Streams
Jacobson, S., Marshall, J., Dalrymple, D., et al.
Trout of the species Oncorhynchus mykiss, commonly known as rainbow trout, redband trout or steelhead, historically populated coastal streams and the near-shore ocean throughout California. While both forms reproduce in fresh water, steelhead migrate between the ocean and fresh water while resident rainbow trout live entirely in fresh water. Urbanization and dam construction in Southern California have inhibited or completely blocked steelhead ocean migration. As a result, many O. mykiss populations are isolated in freshwater streams often near remote headwaters of their native basins, and have adopted a completely resident life history. These populations are relicts of native coastal steelhead lineage and are referred to as rainbow trout. In addition to habitat degradation, poor water quality and low flows, and stocking of hatchery raised rainbow trout of different genetic backgrounds and reduced fitness into many southern California streams and reservoirs are further threats to survival of native O. mykiss at the southern end of their range. Understanding the ancestry of current rainbow trout populations is needed to determine which extant populations of O. mykiss are part of the genetic lineage of the endangered Southern California Steelhead Distinct Population Segment (DPS). The focus of this study is to document the location and genetic lineage of existing rainbow trout populations in the southernmost extent of their native range to support ongoing and future steelhead recovery efforts.
Jacobson, S., Marshall, J., Dalrymple, D., et al. "Genetic Analysis of Trout (Oncorhynchus mykiss) in Southern California Coastal Rivers and Streams" California Department of Fish and Wildlife (2014): 675–689