An all-season trap for downstream-migrating fish and other aquatic organisms

AN INVESTIGATION OF THE LARVAL STAGES OF THE SEA LAMPREY (Petromyzon marinus), which started in 1960, required a trap that could capture lamprey larvae moving downstream, and that would operate efficiently throughout the year. Sub zero temperatures in the winter and flooding during the spring were the most critical operational problems. Part of the trap was based on the principles of an inclined-plane trap described by Wolf (1951), but the design also incorporated features to prevent ice formation during the winter and to and to strain high flows during the spring runoff.