Swim speeds and energy use of upriver-migrating sockeye salmon (Oncorhynchus nerka): simulating metabolic power and assessing risk of energy depletion

Peter S. Rand and Scott G. Hinch
Can. J. Fish. Aquat. Sci./J. Can. Sci. Halieut. Aquat. 55(8): 1832-1841 (1998)

Abstract: We simulated metabolic power consumed by Fraser River sockeye salmon (Oncorhynchus nerka) during upriver migration based on direct measures of activity from physiological field telemetry. The most accurate prediction of energy expenditure was obtained by expressing activity as a fine time scale (5 s) stochastic process. By imposing a daily time step, predictions of energy use were considerably lower than observed energy use, suggesting that the practice of modeling field energetics at a daily time scale, particularly for relatively active fish, may render dubious results. Daily mean power consumption through the Fraser River Canyon by the average migrant was about 20 W, about fourfold higher than for less constricted reaches. Power consumption predicted at fine time scales ranged from <1 W (0.1 body length·s^-1) during periods of reduced activity to 1700 W (8 body lengths·s^-1) during bursts while navigating through turbulent canyon reaches. Through Monte Carlo simulations representing environmental variability observed during 1950-1994, we determined that 8% of the salmon runs during this time resulted in high risk of exhaustion for the average migrant that could lead to elevated in-river mortality. Reducing harvest levels on sockeye salmon that may be exposed to these unfavourable conditions may assist agencies in achieving a risk-averse management strategy.