Swimming Speeds of Sockeye and Coho Salmon on Spawning Migration

Abstract

The speed at which sockeye and coho salmon swim while on spawning migration through a river was determined by direct timing of individual fish over measured river sections and by measurement of opposing water velocities. Migration was accomplished by two locomotory patterns: dart and steady swimming. For steady swimming there was a critical opposing water velocity from 1.1 to 1.7 ft/sec (mean 1.4 ft/sec). Against currents slower than the critical range steady swimming to a maximum speed of approximately 3.4 ft/sec (1.7 body lengths (L)/sec) was sustained through the observation areas, but against currents faster than the critical range salmon broke into position-holding behaviour at intervals. The calculated inter-decile range of swimming speeds (excluding slowest 10% and fastest 10%) against water velocities below the critical range was 1.75–3.18 ft/sec (0.9–1.7 L/sec) for sockeye salmon and 1.70–3.14 ft/sec (0.9–1.7 L/sec) for coho salmon. These swimming speeds were below maximum sustained values which have been determined experimentally.