Diel Movements of Beaked Redfish and the Implications of These for Stratified Random Bottom Trawl Estimates of Biomass and Abundance

Abstract

Beaked redfish Sebastes spp. in the northwest Atlantic Ocean exhibit diel vertical migrations, moving off the bottom at night in pursuit of their prey. This movement is quite well documented and has implications not only for commercial fisheries, but also for researchers who may conduct 24-h trawling surveys. Catch data obtained from 6,898 research fishing sets in depths of 180 m or greater in the northwest Atlantic, involving two different trawls, were analyzed to determine the relative catch rates for beaked redfish during different time periods. The results were applied, as correction factors, to the catches of three time series of stratified random surveys. Application of these correction factors did not have any significant effect on the trends in either abundance or biomass determined from these surveys or on the perceived geographic distribution of the fish. It is concluded that diel movements do not have to be accounted for during trawling surveys for beaked redfish under the current sampling and data analysis regime.