Assessing the potential of selective fish passage using trap-and sort fishways
Developing methods of blocking and removing invasive fishes, while allowing the passage of desirable fishes (selective fish passage) is becoming an issue of great importance to fisheries managers in the Great Lakes. We propose to assess the potential for selective fish passage with currently operated trap-and-sort fishways used to remove invasive Sea Lampreys (Petromyzon marinus) and pass desirable fishes. Trap and sort fishways consist of sequential downstream and upstream compartments. The downstream compartment has a large (12-30 cm) funnel entrance and the upstream compartment a small (5 cm) funnel entrance to achieve some passive separation of Sea Lampreys and non-target fishes based on size and shape. Additional separation is achieved by physical removal (netting) and sorting of the fish. Presently, trap-and-sort fishways are the most promising option for achieving selective fish passage; however, the efficiency of passive sorting needs to be improved. We will conduct (i) analyses of daily records for >30 trap years of data from three trap-and-sort fishways: Big Creek (Lake Erie), Big Carp (Lake Superior), and Cobourg Brook (Lake Ontario) to estimate current levels of passive sorting being achieved in trap-and-sort fishways, (ii) field experiments testing the effects of discharge and light as means of increasing passive sorting of Sea Lamprey from desirable fishes, (iii) simulation models to evaluate passive sorting options in terms of the risk of Sea Lamprey escapement and the benefits of passing desirable fishes.