Exploring the If's, When's and Where's of Steelhead Estuarine and Ocean Habitat Use (with speculation about the why's?)

Steelhead have the greatest life history variability among the Pacific salmon, providing inherent resilience to change of many types. In the face of large scale anthropogenic perturbations such as habitat alteration, migration barriers, and climate change, steelhead can persist via altered life-history strategies, often biased to certain habitat types, suggesting other unused habitats are impaired. Such resilience can provide management insights, for when other species are simply lost, it may be hard to determine the ultimate cause of decline.  Often some fraction of the population persists in an alternate strategy, allowing direct quantification of the costs and benefits of different life histories.  These large-scale experiments are happening across thousands of rivers in response to both long term environmental change and novel anthropogenic challenges.  Part of the steelhead’s success lays with its ‘ace in the hole’- the ability of a resident rainbow trout phenotype to persist even where anadromy is disfavored.  While much is coming to light about the mechanistic underpinnings of this, we will focus on how varying environmental conditions in the fish’s three primary habitats: river, estuary and ocean result in tradeoffs among growth, survivorship and fecundity, ultimately influencing if, when and how far out to sea a steelhead will go.