Underwater observations on fish behavior to determine the coefficient of catchability for Danish seine

Abstract

Underwater observations were conducted to assess the impact of the research Danish seine elements on behavior of walleye pollock Theragra chalcogramma in its active zone. The underwater video equipment was installed on specially designed and constructed experimental platform and on elements of the Danish seine. In the experiment with pollock, the experimental platform demonstrated its low efficiency, however, it could be used for observations on sedentary benthic organisms on homogeneous soils without sharp changes in the terrain. With the equipment installed directly on the Danish seine, high efficiency of the seine ropes was observed: up to 92 % of fish from encircled volume remained in the towed area. Taking into account this estimation and features of fish biomass distribution, the coefficient of catchability for Danish seine is determined as 0.40 ± 0.15.