Effects of tidal currents on Pacific salmon migration: results from a fine-resolution coastal model

Abstract

Experiments with a numerical model of salmon homing migration show that tidal currents can significantly affect return timing of sockeye salmon (Oncorhynchus nerka) off the northern coast of British Columbia. The numerical model combines results from a fine-resolution hydrodynamic model of the waters off northern British Columbia with an individual-based model of salmon migration. Results suggest that coastal tidal currents affect the return timing by causing the number of returning salmon to vary at a cycle corresponding to the dominant tidal period of 12.4 h. Such variations are associated with a patchiness that develops in the spatial distribution of simulated salmon. These features occur as the salmon swim through an oscillating tidal current that exhibits relatively sharp gradients in amplitude. The results may be of use to the design of sampling strategies where aliasing problems may occur.