Influences of type and orientation of bait on catches of swordfish (Xiphias gladius) and other species in an artisanal sub-surface longline fishery off northeastern Brazil

Two experiments were done to examine the relative effectiveness of squid and mackerel as bait for artisanal longliners operating off the northeast coast of Brazil. In experiment 1, compared to clusters of hooks baited with vertically orientated squid, those with vertically orientated mackerel (attached to hooks according to normal commercial operations) showed significantly more contact by fish and had less bait remaining at the end of each set, but retained significantly less total fish by weight and fewer swordfish, Significantly more swordfish swallowed hooks baited with vertically orientated squid, than those with vertically orientated mackerel and showed greater mortality. In experiment 2. clusters of hooks baited with horizontally orientated mackerel had significantly greater contact by fish and less bait remaining than those baited with vertically orientated squid. No other significant differences were detected between baits. Type of bait showed no significant effect on anatomical hook location and mortality for total catch (all species combined) and swordfish. The results are discussed in terms of possible factors influencing behaviour of fish during the hooking process and the importance of the visual stimuli of baits for subsurface longlines. (C) 2001 Elsevier Science B.V. All rights reserved.