Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line longline trials

The presence of permanent magnets on hook and line and inshore longline gear was tested for its ability to reduce the bycatch of sharks and rays.  Neodymium-iron-boron magnets were affixed to hook and line gear and barium-ferrite magnets were attached to longline gear.  Both types of fishing gear showed species specific responses but overall elasmobranch capture was significantly reduced when magnets were used. In the hook and line fishery catches of the Atlantic sharpnose shark and smooth dogfish were both significantly reduced when magnets were used but catches of spiny dogfish and clearnose skate were not.  Similarly, in the longline fishery blacktip sharks and southern stingray catch rates were reduced but sandbar shark catch rates were not when magnets were used.  There were no differences in the catch rates of several fish species, including Atlantic croaker, oyster toadfish, black sea bass and bluefish when magnets were used.