Migratory Movements of Adult Sockeye Salmon (Oncorhynchus nerka) in Coastal British Columbia as Revealed by Ultrasonic Tracking

Abstract

Individual courses, obtained by ultrasonic tracking nine sockeye in 1969 and nine in 1970, ranged up to 130.8 km (24.2 median) and 66.6 hr (9.6 median). Course directions were mainly to the north and west in 1969 and to the south and east in 1970. This difference may have arisen from differences in home river affiliation of the tracked sockeye. Swimming speeds showed a pronounced diel rhythm with higher values at 1400 hr and lower values at 0200 hr. The average speed of 53 cm/sec was consistent with rate of movement estimates obtained previously from tagging–recapture studies. A 13 cm/sec greater average speed in 1970 than in 1969 was observed, and possible reasons for the difference were discussed. Differences in speed within or beyond 2 km from land were not observed for either year. A diel rhythm in the magnitude of course change appeared, with a decrease in the frequency of large angular changes occurring in the afternoon. An orientation mechanism involving a daily reorientation process is hypothesized.