Effectiveness of tori line use to reduce seabird bycatch in pelagic longline fishing

Abstract

Industrial longline fisheries cause the death of large numbers of seabirds annually. Various mitigation measures have been proposed, including the use of tori lines. In this study the efficiency of a single tori line to reduce seabird bycatch was tested on pelagic longline vessels (25-37m length). Thirteen fishing trips were carried out in the area and season of the highest bycatch rates recorded in the southwest Atlantic (2009–2011). We deployed two treatments in random order: sets with a tori line and without a tori line (control treatment). The use of a tori line significantly reduced seabird bycatch rates. Forty three and seven birds were captured in the control (0.85 birds/1,000 hooks, n = 49 sets) and in the tori line treatment (0.13 birds/1,000 hooks, n = 51 sets), respectively. In 47% of the latter sets the tori line broke either because of entanglement with the longline gear or by tension. This diminished the tori line effectiveness; five of the seven captures during sets where a tori line was deployed were following ruptures. Nine additional trips were conducted with a tori line that was modified to reduce entanglements (2012–2016). Seven entanglements were recorded in 73 longline sets. The chance of a rupture on these trips was 4% (95% c.l. = 1–18%) of that during 2009–2011. This work shows that the use of a tori line reduces seabird bycatch in pelagic longline fisheries and is a practice suitable for medium size vessels (~25-40m length). Because the study area has historically very high bycatch rates at global level, this tori line design is potentially useful to reduce seabird bycatch in many medium size pelagic longline vessel fishing in the southern hemisphere.

Foraging distribution of breeding northern fulmars is predicted by commercial fisheries

“…Camphuysen & Garthe 1997, Skov & Durinck 2001. The recent decline of this species, as well as importance of intensely fished areas for foraging fulmars, highlights the need for targeted conservation that may involve adaptation of fishing gears or fishing practices to mitigate bycatch risk (Løkkeborg 2011, Domingo et al 2017, Da Rocha et al 2021). This study would also suggest that negative effects of other threats to fulmars such as oil pollution could be compounded if present in areas of intense fishing activity.…”

Trends in numbers of the Critically Endangered Chinese Crested Tern Thalasseus bernsteini and sympatrically nesting Greater Crested Tern T. bergii in the Matsu Archipelago, Taiwan

“…decoys, audio playbacks, mirror panels). In addition, bird scaring lines (tori lines) are used by longline fisheries to effectively deter albatrosses and petrels from ingesting baited hooks (Domingo et al 2017). A combination of social attraction at islands in the MITR that are free of human disturbance, and ropes, stakes, and flagging at Sheshan would be effective tools for dissuading tern nesting on Sheshan early in the breeding season and attracting GCTs and CCTs to colonise other islands instead.…”

Hookpod-mini: a smaller potential solution to mitigate seabird bycatch in pelagic longline fisheries

“…On-board Vessel B tori lines were not deployed on the final 4 sets (out of 12) due to an entanglement with the fishing gear and tori line in windy conditions on the seventh set. It has been well documented that such entanglements reduce both the deployment rate and effectiveness of tori lines once they are deployed (Domingo et al 2017). Currently, there are low levels of at-sea observer coverage, typically <5% (Allain et al 2012), and even lower uptake rates of electronic monitoring on the world's pelagic longline fisheries.…”