Effect of ground gear type on catch efficiency of demersal trawls

Demersal trawls are among the most widespread and important fishing gears worldwide. However, due to issues with catch efficiency, high energy demand and damage to the seabed, gear improvements are searched for that could reduce fishing effort to harvest the catch quota. Several components of demersal trawls, including the ground gear, affect its capture efficiency. Recent progress has led to the development of the semi-circular spreading ground gear (SCSG), which has resulted in increased catch efficiency compared to the traditional rockhopper ground gear (RH). However, little is known about the mechanisms explaining this increased catch efficiency. The present study compared capture rates for cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and redfish (Sebastes spp.) in a trawl equipped with the RH and a trawl equipped with the SCSG in the Barents Sea demersal trawl fishery. The results showed that the ground gear catch efficiency was clearly length dependent for cod and haddock, with high fractions of smaller fish escaping through or underneath the ground gear. The results confirmed that the trawl with the SCSG could capture more cod between lengths of 25 – 50 cm, but also that more cod between 50 – 80 cm escaped beneath or through the center part of this ground gear compared to the RH gear. The higher catch efficiency of the SCSG can likely be explained by increased gear spreading an improved herding efficiency compared to the RH gear. Nonetheless, a substantial fraction of fish still escaped beneath or through both ground gears, demonstrating potential for further improvements in catch efficiency.