One fish, two forms, many questions

From the FishBio blog:

Steelhead“Genetically they are the same species, but rainbow trout and steelhead lead very different lives. These fish represent two separate life strategies of the species Oncorhynchus mykiss: a resident form that stays in freshwater (rainbow trout), and an anadromous form that migrates to the ocean (steelhead). For years, researchers have been unable to identify specific traits that will determine whether a given O. mykiss will exhibit anadromy or residency. This lack of definitive evidence has compelled managers to treat the species as a single population. Most management actions on the West Coast focus on the fact that steelhead are threatened or endangered in California, Oregon, Washington, and Idaho; however, most populations of resident rainbow trout are abundant in their native streams. In a study published in the Canadian Journal of Fisheries and Aquatic Sciences earlier this year, a group of scientists from agencies, universities, and non-profit groups came together in an effort to better understand why O. mykiss can possess both anadromous and residency life-history traits. Understanding the tendencies of these fish may help researchers determine best-fit management strategies for populations in different environments. … ”

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