Factors affecting the number and mortality of seabirds attending trawlers and long-liners in the Kerguelen area

Published source details Weimerskirch H., Candeville D. & Duhamel G. (2000) Factors affecting the number and mortality of seabirds attending trawlers and long-liners in the Kerguelen area. Polar Biology, 23, 236-249.
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This study is summarised as evidence for the following.

	Action	Category
	Reduce seabird bycatch by releasing offal overboard when setting longlines Action Link
	Set longlines at night to reduce seabird bycatch Action Link
	Use streamer lines to reduce seabird bycatch on longlines Action Link

Reduce seabird bycatch by releasing offal overboard when setting longlines

A replicated, controlled study in the sub-Antarctic Indian Ocean in 1994-7 (Weimerskirch et al. 2000) found that significantly fewer white-chinned petrels Procellaria aequinoctialis were caught on longlines when offal was released over the side of the boat as lines were being set (0.46 birds/1,000 hooks caught when offal was released vs. 1.00 birds/1,000 hooks with no release, total of 524 lines studied). There were no significant changes in other species caught, possibly due to smaller sample sizes. The authors caution that significantly more birds followed fishing boats when they released offal (significant increases for six of ten species) and the practice may therefore enforce long-term associations between fishing boats and food. This study is also discussed in ‘Set longlines at night to reduce seabird bycatch’ and ‘Use streamer lines to reduce seabird bycatch on longlines’.
Set longlines at night to reduce seabird bycatch

A replicated, controlled study in the sub-Antarctic Indian Ocean in 1994-7 (Weimerskirch et al. 2000) found that longlines set at night had significantly lower seabird bycatch, compared to those set during the day (0.91 birds caught/1,000 hooks for day-set lines vs. 0.17 birds/1,000 hooks for night-set lines, total of 524 lines studied). This result was consistent across all species, except for wandering albatross Diomedea exulans, which was only caught on 12 occasions. The authors note that whilst the number of white-chinned petrels Procellaria aequinoctialis caught was half that caught during the day, these levels may still be unsustainably high: they quote an unpublished figure of 340 petrels caught during a single line set off Kerguelen Island. The study took place on three Ukranian and one Japanese longliners fishing for Patagonian toothfish Dissostichus eleginoides off Kerguelen Island (France). Deck lights were not switched on during night setting. This study is also discussed in ‘Use streamer lines to reduce seabird bycatch on longlines’ and ‘Reduce seabird bycatch by releasing offal overboard when setting longlines’.
Use streamer lines to reduce seabird bycatch on longlines

A replicated, controlled study in the sub-Antarctic Indian Ocean in 1994-7 (Weimerskirch et al. 2000) found that using a streamer line whilst setting longlines did not appear to reduce seabird bycatch for all species combined, or for white-chinned petrels Procellaria aequinoctialis, the most frequently caught birds (0.57 birds/1,000 hooks on sets with a streamer vs. 0.52 birds/1,000 hooks for sets without, total of 524 lines studied). Streamer lines were 150-175 m long propylene ribbons (2 m long) every 2-3 m. This study is also discussed in ‘Set longlines at night to reduce seabird bycatch’ and ‘Reduce seabird bycatch by releasing offal overboard when setting longlines’.