Horizontal and Vertical Movements of Adult Steelhead Trout, Oncorhynchus mykiss, in the Dean and Fisher Channels, British Columbia

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Abstract
Horizontal and vertical movements of adults steelhead trout, Oncorhynchus mykiss, in the Dean and Fisher channels, British Columbia, were examined using radio and ultrasonic telemetry. Nineteen steelhead, captured by purse seine in 1987 and fitted with radio tags, averaged 17.2 ± 2.2 (SE) km/d to travel 96.4 km from the capture/release site to the Dean River mouth. Detailed movement patterns were assessed from six steelhead tracked for 224 h (21.0–49.8 h/fish) using ultrasonic tags in 1988. Gross and net travel rates of steelhead averaged 2.0 and 0.8 km/h, respectively, indicating considerable milling by the fish. Gross movement during daylight was twice that during the night and most movement at night was attributed to tidal currents. The steelhead swam primarily on the surface throughout the fjord, regardless of salinity and temperature stratification. Geometric mean depth was 1.6 m and the fish spent, on average, 72% of the time in the top 1 m (the warmest and least saline water available). Median time between dives to 5 m (near the halocline) was 9 min, although 14% of the surface intervals exceeded 1 h. These results are discussed in relation to several hypotheses regarding guidance mechanisms used by migrating fishes.

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