STEELHEAD 



Common Name: STEELHEAD 

 Scientific Name: Oncorhynchus mykiss 



Species Status: Proposed as Threatened/Endangered 



Species Trend: Unknown 



Current Estimated Population: Unknown 



SPECIES POPULATION STATUS 



10 ESUs of steelhead were proposed on August 9. 1996. Proposed as threatened were: Lower 

 Columbia River. Oregon Coast, Klamath Mountains Province. Northern California, and Snake 

 River Basin ESUs. Proposed as endangered were: Central California Coast. South-Central 

 California Coast, Southern California, Central Valley, and Upper Columbia River ESUs. A final 

 determination on all will be made in late summer. 1997. 



NMFS considered available information on the geographic extent and reproductive strategies 

 (e.g., run timing) of the ESU containing the Illinois River winter steelhead. In general, steelhead 

 are believed to have strong tendencies to home to their natal streams, but there are few studies 

 directly relevant to the area under consideration. There is evidence that some adult steelhead 

 move between the Klamath. Rogue, and Smith Rivers. However, it is not clear whether this 

 wandering results in spawning within non-natal streams. 



Available genetic information indicates that there is a genetic discontinuity (or at least a 

 transition) between steelhead from coastal streams in southern and northern Oregon. Although 

 the discontinuity/transition appears to be in the vicinity of Cape Blanco, the resolution of genetic 

 sampling does not allow for precise definition of this boundar\'. 



Several genetic samples from northern California steelhead were considered during this status 

 review. Samples from the Klamath River and the Trinity River (a tributary to the Klamath 

 River) do not differ substantially from steelhead populations to the north. However, there are 

 large genetic differences between samples from the Klamath River Basin and those taken from 

 rivers to the south. The differences between steelhead from these two areas are stronger than 

 those between southern and northern Oregon steelhead populations. 



Within the area bounded by Cape Blanco and the Klamath River Basin, there is evidence of 

 genetic heterogeneity, suggesting a reasonable degree of reproductive isolation between 



66 



