Tori line designs and specifications for small pelagic longline vessels
Tori lines are one of the most thoroughly tested seabird bycatch reduction measures available, and have been proven effective in reducing seabird bycatch in both trawl and longline fisheries. However, most of the work to date has been carried out on vessels over 20 m in length. In WCPFC-SC12-2016/ EB-WP-10 Pierre et al reported trials conducted on land and on four different smaller vessels at sea, to explore tori line designs and materials appropriate for use during demersal and pelagic longline fishing methods. The approach was structured by vessel speed, which broadly correlates with small-vessel longline fisheries targeting different species. This report describes further work producing tori line designs suitable for use under normal commercial fishing conditions in the New Zealand pelagic longline fleet, comprising small vessels 12-25m in length. The project also sought to address any concerns raised by fishers. In particular, designs were developed that addressed safety concerns, minimised tangling, and allowed deployment at night and in poor weather conditions. Achieving a 75 m aerial extent with a combination of long tube streamers and short tape streamers is feasible as a minimum standard, which corresponds favourably to internationally recognised best practice advice for larger pelagic vessels. Design considerations are focussed on the aerial section, the drag section and the tori poles and their attachment. Advice is provided on how to optimise each of these elements for deployment on small vessels. In developing specifications or guidance for tori lines to be used on small vessels we recognise the need to incorporate a degree of flexibility to allow designs to be optimised to each individual vessel. For example, allowing considerable flexibility in the design of the drag section of the tori line is recommended as the method of generating drag is not important.