Evaluation of a Modified Codend Configuration for a Marine Mammal Bycatch Reduction Device in a Midwater Trawl Gear

A modified single-layer codend configuration developed from previous studies was evaluated using BRDs with guide net angles of 30° and 45°. For target species, catch loss rates based on the number and weight of individuals were 9% and 13%, respectively for herring (Culpea pallasii) with the 30° guide net and 16% and 18% with the 45° guide net. For Korean pomfret (Pampus echinogaster), catch loss rates were 24% and 23% at 30° and 4% at 45°. Catch loss rates of target mackerel (Scomber jamponicus) with the 30° guide net reached 56%, whereas hairtail (Trichiurus lepturus) had loss rates of 60% and 65% with the 45° guide net. These results suggest that further modification of BRD is necessary. However, no bycatch of marine mammals occurred during the experimental operations, despite dolphins being observed nearby.