Bait loss from bottom-set longlines as determined by underwater observations and comparative fishing trials

Abstract

Losses of herring, capelin and squid baits from bottom-set longlines for cod ( Gadus morhua) were compared using underwater observation techniques and comparative fishing methods. Underwater observations revealed that squid was better at staying on hooks than herring and capelin. The percentage of bait lost after a given soaking time and the duration a piece of bait remained on a hook at a given intensity of attack by fish were used as criteria to estimate bait tenacity. Capelin bait was lost more readily (44%) than squid (20%, P < 0.1), but herring was lost more significantly (75%) than either squid ( P < 0.001) or capelin bait ( P < 0.05). At the same intensity of attack, squid tended to stay on the hook for longer than herring or capelin. Comparative fishing trails revealed that the rate of bait loss was related to fishing ground depth, bait type and mainline type. More bait was lost in deeper waters for both squid and herring bait and on both floating polypropylene (PP) and sinking polyester (PES) mainlines. For both bait types, significantly more bait was lost in sinking PES mainlines set on the bottom than floating PP mainline set off the bottom ( P < 0.01). For both mainline types (PP and PES), significantly more herring bait was lost than squid bait ( P < 0.01).