Migration speed, run timing and migration route for Interior Fraser Steelhead Trout (Oncorhynchus mykiss)

Abstract

The purpose of this process was to compile information and estimate key parameters (run timing, migration speed and route) required for the development of a fishery planning tool to assess the risk to returning adult Interior Fraser River Steelhead Trout from marine and freshwater fisheries in Southern British Columbia. Existing information on the migration speed of returning adult Steelhead Trout, including but not limited to Interior Fraser River Steelhead Trout, in marine and freshwater habitats is sparse and variable, but could be used to parameterize the fishery planning tool. Adult Steelhead Trout appear to use migration routes on both sides of Vancouver Island, but available information is insufficient to estimate the proportion of Interior Fraser River Steelhead Trout that use each route. The timing of upstream migration of Interior Fraser River Steelhead Trout was estimated using data from the Albion test fishery in the lower Fraser River. A model with a hierarchical structure and asymmetric run timing predicts that 95% of Interior Fraser River Steelhead Trout pass the test fishing location between September 8 and November 23, with 50% passing by October 10. Sensitivity analyses indicated run-timing estimates were robust to data uncertainties and were not substantively affected by sparse Steelhead Trout catch data in recent years.