How fast do demersal longlines sink?

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 seawater of longlines commonly used in the world's demersal fisheries. Lines with integrated weight (lead cores) sank two to three times faster (45-52 cm/s) than conventional (unweighted) lines. Conventional 9 mm diameter lines made from polyester sank at 23 cm/s compared to 18 cm/s for 9 mm Silver lines (blend of polyester, polyethylene and polypropylene). Samples of lines set by hand in still water sank significantly faster than longlines set from a fishing vessel, presumably because of the effect of the sea swell and upwellings from the propeller on the line set from the vessel. (C) 2002 Elsevier Science B.V. All rights reserved.