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    How fast do demersal longlines sink?

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    G. Robertson (Australia), E. Moe, R. Haugen (Norway) and B. Wienecke (Australia)
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    Longlines that sink fast reduce the time available to seabirds to attack baited hooks and are important in efforts to minimise seabird by-catch in longline fisheries. We measured sink rates in still water of longlines made by Fiskevegn, the world’s leading manufacturer of demersal longlines. Lines with integrated weight (lead cores) sank two-three times faster (45- 52 cm/second) than conventional (unweighted) lines. Conventional lines made from 9 mm polyester sank at 23 cm/second compared to 18 cm/second for Silver lines of the same diameter. Samples of lines set by hand in still water sank significantly faster than longlines set from a fishing vessel.