Ken Currens, hatchery genetics manager at the Northwest Indian Fisheries Commission, recently gave an interesting talk on the evolution and diversity of steelhead.

The presentation includes a mix of salmon genetics (obviously), geology and the genetic history of salmon parasites. His main thesis is that rather than spreading up the coast through the ocean, steelhead spread through ancient connections between three major historic river systems — the Columbia, Klamath and Sacramento.

You can view the entire presentation below and listen to Currens’ talk at the same time below:

Here is Currens’ write-up for his talk:

“The first salmonid, Eosalmo driftwoodensis, occurred in British Columbia nearly 50 million years ago just after the Age of Dinosaurs. Whether it is a coincidence that its fossil remains were found in sediments of a stream named for its large woody debris (which we now associate with good steelhead streams), we may never know. In this talk, however, I trace the evolution and biogeography of Pacific salmonids as climates changed, continents drifted apart, mountains formed, and rivers changed courses to explain the presence of forms such as the 10-foot 500-pound “saber tooth salmon” (Oncorhynchus rastrosus) leading to the extant patterns of diversity in steelhead and rainbow trout (O. mykiss). Genetic and morphological differences in O. mykiss suggest the species originated near the Gulf of California and moved northward probably entering the Columbia River 50 – 32 thousand years ago. Internal connections through the Oregon desert basins between the Columbia River and the Sacramento and Klamath Rivers may have been a major avenue for that dispersal. These patterns suggest the persistence and diversity of O. mykiss had more to do with the persistence of large river systems and the ability of the species to adopt multiple life-history strategies (such as anadromy, adfluvial migration, and residency) than it did with more localized effects of Pleistocene glaciations”.