UC Davis

Intraspecific diversity is a crucial part of conservation genetics because it buffers populations from decline after catastrophic events. There is incredible intraspecific life history diversity within the species Oncorhynchus mykiss, commonly known and rainbow trout and steelhead. The life history of a freshwater residing rainbow trout differs greatly from that of a steelhead, who’s life history mirrors a salmon. There are many gaps in understanding of the life history variation in O. mykiss that can aid in its’ conservation and management. Here we apply genetics to better understand the ecology of steelhead throughout their range. We used a genetic marker in the North Umpqua River in Oregon to identify where early migrating steelhead are spawning. We also ran genetic associations with the half-pounder life history and early migration steelhead in northern latitudes. We found that some streams have variable use by early migrating steelhead depending on the spawning year. Additionally, the half-pounder life history is not likely to be genetically controlled, even though this variant occurs in two locations at the extreme ends of the species’ range: Kamchatka, Russia and California, USA. We also found the genetic region that controls migration time in the Situk River, Alaska, which is different, but close in position to the GREB1L/ROCK1 genes that control migration time in souther latitude populations. These results show unique differences in life-history diversity O. mykiss that are population specific. Ultimately, discoveries in conservation genetics in salmonids should not be extrapolated, but should be tested due to the incredible intraspecific diversity.