Comparative fishing experiments by research trawlers for cod and haddock in the North Sea

Abstract

For 10 days in June 1986 a comparative fishing experiment was carrried out in a small area of 240 nm ² in the northern North Sea. Three ship-gear combinations were compared: (1) the FRV “Walther Herwig”. with the French “GOV trawl (36/47 m)” but with a rubber disc groundrope; (2) the FRV “Anton Dohrn”, with the “GOV trawl (36/47 m)”; and (3) FRV “Anton Dohrn”, with the German “180-foot herring trawl”, in each case rigged with a heavy bobbin groundgear. A significant difference in the efficiency of capture of haddock was found only with the different nets, higher values occurring with the “180-foot herring trawl” (conversion factor = 1.45). The combined vessel and groundgear effect on the haddock catches was statistically insignificant. In contrast to haddock, the capture efficiency for small cod was strongly dependent on the groundgear. Compared with the rubber disc groundrope, about 85% of cod smaller than 32 cm escaped between the heavy bobbins under the fishing line. For bigger cod (32cm), the capture efficiency of the “GOV trawl” is significantly higher (conversion factor = 2.4) than that of the “180-foot herring trawl”.