Individual study: Use of streamer lines may reduce rate of seabird bycatch mortality from bluefin tuna Thunnus maccoyii longlining in New Zealand waters
Murray T.E., Bartle J.A., Kalish S.R. & Taylor P.R. (1993) Incidental Capture of Seabirds by Japanese Southern Bluefin Tuna Longline Vessels in New Zealand Waters, 1988-1992. Bird Conservation International, 3, 181-210
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Set longlines at night to reduce seabird bycatch
A study using data from bluefin tuna Thunnus thynnus boats operating off New Zealand between 1988 and 1992 (Murray et al. 1993) found that the effects of night-setting on seabird bycatch rates varied between fishing areas, probably due to different species making up the majority of bycatch. In southern areas, 87% of 47 identified birds caught were albatrosses and 73% of 88 birds were caught between 0600 and 1400 (when 41% of 1,009 lines were set). In contrast, in northern fishing grounds, where 59% of 75 identified birds were petrels, 44% of the 181 birds caught were hooked within 90 minutes of dawn or dusk and 42% were caught at night (when 54% of 1,180 lines were set).
Use streamer lines to reduce seabird bycatch on longlines
A comparative study of ten bluefin tuna Thunnus thynnus longlining boats fishing off New Zealand in 1992 (Murray et al. 1993), found that none of five vessels that used a streamer line over 51% of the time caught any birds (over 100 line sets). The remaining five boats used streamer lines for less than 12% of the time and caught 14 birds over 157 sets. However, the authors cautioned that these results were preliminary, with limited observer coverage, no controls and no statistical tests.