New Zealand Journal of Marine and Freshwater Research abstracts
Preliminary performance assessment of an underwater line setting device for
pelagic longline fishing
DECLAN O'TOOLE
Emerald Fisheries Science
P. O. Box 2145
Tauranga, New Zealand
email: Emerald1@ihug.co.nz
JANICE MOLLOY
Department of Conservation
P. O. Box 10 420
Wellington, New Zealand
email: jmolloy@doc.govt.nz
Abstract Baited branchlines were set from a tuna longlining
vessel using an underwater setting device and their sink patterns compared with
those of baited branchlines that were hand-thrown. Using a paired
t-test
at an hypothesised mean difference of 2 m, at a point 100 m astern of
the vessel, baited branchlines set using the device were significantly deeper
than those that were hand-thrown. Baited branchlines set using both methods
showed a high variation in their sink patterns; on some sets they sank faster
than others. The underwater setting device has potential to reduce seabird
bycatch substantially with minimal intrusion on the normal operation of a
longline fishing vessel. It delivers baits underwater (removing the visual cue
of a hand-thrown baited hook to seabirds) and immediately places baited hooks
outside the diving range of some vulnerable albatross species (
Diomedea
spp.,
Phoebastria spp.,
Thalassarche spp., and
Phoebetria
spp.).
Keywords seabirds; incidental mortality; longline fisheries;
mitigation devices; underwater setting; sink rates; time depth recorders
M99034
Received 24 June 1999; accepted 28 March 2000
PDF file of entire paper: medium quality (542K); (scanned from paper original: notes about this process)
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