Using decades of spawning data and hydraulic models to construct a temperature-dependent resource selection function for management of an endangered salmonid

Abstract

In North America, impassable, man-made barriers block access to salmonid spawning habitat and require costly restoration efforts in the remaining habitats. Evaluating restored spawning habitat quality requires information on salmon water velocity and depth preferences, which may vary in relation to other variables (e.g., water temperature). We demonstrate a generalizable, low-cost method to gather and analyze these data by combining aerial redd surveys of winter-run Chinook salmon (Oncorhynchus tshawytscha), 2D hydraulic modeling, and generalized linear models to calculate spawning resource selection functions (RSFs). Our method permits the examination of interactions between environmental variables and habitat selection, which are frequently treated as independent. Our methods resulted in an RSF that shows interactions between both velocity and depth preference with changing temperature. Preferred depth increased and preferred velocity decreased with increasing temperature. Spawning RSFs for environmental variables may change as other environmental conditions (i.e., water temperature) change; thus, it is important to account for potential interactions when using or producing RSFs.