LAURITZEN, Dean V.*; HERTEL, Fritz; GORDON, Malcolm S.: Experimental Studies of Jumping Preferences of Adult Migrating Pacific Salmon

The damming of streams has been a major contributor to the decline of many populations of anadromous fishes around the world. This is especially true for the endangered Pacific salmon. Fishladders have been built to help fishes overcome these obstacles but their designs are generally inadequate. This is a result of engineering based designs that paid little or no attention to the behavior of the fishes. To develop effective fishladders, one must consider the jumping preferences and abilities of the migrating fishes. We have made what we believe is the first experimental study of the jumping abilities and strategies of adult migrating Pacific salmon. We analyzed the behavior of kokanee, landlocked sockeye salmon (Oncorhynchus nerka), in a specially designed adjustable spillway. Jumping capacities, preferences, and methods were determined over a range of spillway heights, gradients and water velocities. The fish attempted to swim up stream in nearly all spillway conditions tested but jumping was only attempted over a narrow range of conditions. This study provides the first experimentally based foundation for improving fish ladder designs based upon actual fish behavior.