The behaviour of seaward migrating juvenile Pacfic salmonids: implications for enhanced fish passage

Kemp, P.S., Gessel, M.H and Williams, J.G (2004) The behaviour of seaward migrating juvenile Pacfic salmonids: implications for enhanced fish passage. River Restoration North West Conference, Skamania, United States. 02 - 06 Feb 2004.

Abstract

In an effort to restore populations of migratory salmonids on the Columbia River, attempts have been made to aid fish passage and enhance survival at the HEP projects. The guidance efficiencies associated with mechanical structures designed to divert fish away from turbines towards alternative routes of passage are often much lower than expected. Site-specific macro-scale studies that use remote tracking technology have traditionally provided the evidence on which our understanding of fish passage is based. Recent research, however, suggests that fish react to localized environmental factors that operate at a fine-scale. There is a need to integrate information collected across scales to develop on existing models of fish passage that presently are based on assumptions that may or may not be true. We conducted a series of fine-resolution flume experiments at McNary dam, on the Columbia River, to assess the influence of hydraulic transition and overhead cover on the behavior of seaward migrating juvenile Pacific salmonids. Smolts passing through the flume were given a choice of passage route that varied based on rates of velocity acceleration, flow, and overhead cover. Direct observation of behavior revealed that individuals elicit strong avoidance behavior when they encounter areas where hydraulic conditions change rapidly or are covered. Further, the behavioral response varies with species and fork length. Our findings have implications relevant to diversion structure design and culvert passage.

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