Steelhead (Oncorhynchus mykiss) populations have declined throughout their range in the last century and many populations, including those of the Snake River Basin are listed under the Endangered Species Act. The reasons for their decline are many, but include habitat loss and degradation, overharvest, and the construction of dams. Unlike Pacific salmon, which all die after they spawn, post-spawning steelhead (known as kelts) can migrate back to the ocean to feed and replenish their energy stores, then return to freshwater and spawn in subsequent years (known as iteroparity). However, it is estimated that