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UBC Theses and Dissertations

Effects of coastal currents on pacific salmon migration inferred from a fine-resolution numerical model Bourque, Marie-Claude

Abstract

Experiments performed using a numerical model of salmon homing migration show that coastal currents can significantly affect sockeye salmon (Oncorhynchus nerka) returning on 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 a spatially-explicit 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 patchiness in the salmon distribution due to spatial variations of the tidal field. Moreover, results showed that wind-driven currents can cause the number of returning salmon to vary at storm periods of 3 to 18 days. Therefore, the salmon interactions with the coastal currents could provide an explanation for some of the variability seen in data of returning salmon. Simulations of continuous salmon diversion for 1992 to 1994 suggest that currents alone cannot produce a large interannual variability for these years. However, these simulations showed a large variability at storm period within the summer, which could have influenced the calculation of the Northern Diversion Rate. The findings of this thesis can then help to design appropriate sampling strategies, such that aliasing problems due to coastal currents are minimized.

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