Effects of Swim Speed and Activity Pattern on Success of Adult Sockeye Salmon Migration through an Area of Difficult Passage

Abstract
We used electromyogram telemetry to examine swim speeds and passage success for 12 adult sockeye salmon Oncorhynchus nerka migrating through Hell's Gate, a reach in the Fraser River canyon that is notorious for creating conditions that impede salmon migrations. Fishways exist in one segment; however, the approach immediately downstream of the fishways is also very challenging to migration. Average swim speeds (in body lengths per second; BL/s) were slower (P = 0.017) and residency times shorter (P = 0.058) in the approach for fish that successfully entered the fishways (mean = 1.85 BL/s, SE = 0.71; mean = 34.57 min, SE = 17.39; n = 7) compared with those of fish that were unsuccessful (mean = 4.23 BL/s, SE = 0.85; mean = 1,742 min, SE = 1,367; n = 5). Migrant-specific swim-speed patterns revealed that fish alternated at different time scales between relatively fast and slow speeds. Continuous swimming at greater than maximum sustained speeds (Ucrit) never exceeded 3 min in the case of any of the ...

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