Experimental determinations of factors affecting the sink rates of baited hooks to minimize seabird mortality in pelagic longline fisheries


Robertson, G., Candy, S., Wienecke, B. and Lawton, K.



Journal/Publisher Name: 

Aquatic Conservation: Marine and Freshwater Ecosystems

Volume (Issue #): 


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Contact information: 

G. Robertson, Australian Antarctic Division, Channel Highway, Kingston Tasmania 7050, Australia graham.robertson@aad.gov.au

Experiments were conducted aboard pelagic longline vessels off the east coast of Australia to determine the effects of different bait species (blue mackerel, yellow tail mackerel and squid), live and dead bait, weight of leaded swivels (60 g, 100 g and 160 g) and leader length (2 m, 3 m and 4 m distances between leaded swivel and hook) on the sink rates of hooks.  Live bait sank more slowly than dead bait, increasing the exposure of hooks to seabirds but the sink rates of individual live bait species were very variable.  With respect to dead bait, those on the 160 g leaded swivel with a distance of 2 m leader length had the fastest sink rate, while the 60 g swivel on the 4 m leader length had the slowest.  Overall, small changes to the weight of leaded swivels and the length of the leader are not likely to subtantial reductions in seabird mortality.