Accuracy of fish population estimates in a navigation canal with heavytraffic

摘要

A high sampling efficiency and precision of fish population density estimates with three seine nets laid together and hauled individually towards a stop net were achieved in the Shropshire Union Canal (England) despite very heavy boat traffic (9500-10000 number of movements per hectare per year). For roach, and also for perch and ruffe, for 14.3% of estimates, the number of fish collected equalled estimated density ((N) over cap); and also for 52.4% of estimates, 95% CL constituted less than 10% of (N) over cap, which assures precision of production estimation, especially of yield. The method may have an application in many water bodies where the bed is level and without obstacles for hauling net, and water current is less than 2 km h(-1).