An attempt to improve size selection in pelagic longline fisheries for haddock

Abstract

Bycatches of haddock ( Melanogrammus aeglefinus) below legal size (44 cm total length) in the pelagic longline fisheries off the coast of Finnmark, northern Norway, are often high. To reduce the bycatch of undersized haddock, we conducted experiments involving modifications in gear technology and fishing strategy. We tested longlines with a greater rate of sinking, hooks with an inedible plastic body attached to the shank, hooks with nylon bristles attached to the shank, restructured bait based on mackerel ( Scomber scombrus) and sandeel ( Ammodytes lancea), mackerel bait of twice the normal size and restructured mackerel bait of twice the normal size. The inedible plastic body reduced the catch of undersized haddock, as well as the total catch. Restructured sandeel bait gave a significant decrease in catches of undersized haddock, but the number of hooks deployed in this part of the experiment was small. Traditional mackerel bait of twice the normal size resulted in about a 40% reduction in the catch of undersized fish. Catch proportions between length groups in the alternative gears compared to control gear or length distribution based on acoustical data indicate a unimodal selection curve for the alternative gears.