Catch difference of groundfishes between two survey trawl nets having differing headrope and groundrope configurations in the East China Sea

Abstract

We compared the shapes and catches of two trawl nets having differing headrope and groundrope configurations based on paired tow data collected by two research vessels (Yoko Maru and Kumamoto Maru) in the East China Sea. According to the paired data, the vertical opening of the net was significantly higher on the Yoko Maru, which employed a headrope kite, than the Kumamoto Maru, which uses floats on the headrope, while the horizontal opening of the net was significantly wider on the Kumamoto Maru than Yoko Maru (p < 0.01). According to generalized linear model (GLM) analysis of paired data, the capture of Dentex hypselosomus and Photololigo edulis increased when either or both the vertical and horizontal openings of the net of Yoko Maru increased or the horizontal opening of the net of Kumamoto Maru decreased. The catch of these fishes was estimated to be 0.9–4.0 times greater for Yoko Maru compared with Kumamoto Maru, depending on the vertical opening of the net of Yoko Maru. The catch of Champsodon snyderi was only influenced by the horizontal opening of the net, while for two Carangidae species, Trachurus japonicus and Kaiwarinus equula, no influence of the net shape was detected.