The Development and Operational Testing of an Underwater Bait Setting System to Prevent the Mortality of Albatrosses and Petrels in Pelagic Longline Fisheries

Graham Robertson^1*, Phillip Ashworth², Peter Ashworth², Ian Carlyle², Steven G. Candy¹

¹Australian Antarctic Division, Kingston, Australia.
²Amerro Engineering, Warana, Australia.

DOI: 10.4236/ojms.2015.51001                

Abstract

Longline fisheries for tunas and tuna-like species present an existential threat to many populations of albatrosses and petrels worldwide. To prevent this form of mortality we developed a new technology designed to deploy baited hooks underwater beyond the dive depths of seabirds (6 - 10 m for the species most commonly caught). The underwater bait setter is a stern-mounted, hydraulically-operated and computer-controlled device that catapults baited hooks underwater in a steel capsule connected to hydraulic winches by Spectra^® rope. Baits are flushed from the capsule by water pressure through a spring-loaded bait release door. The chief engineering challenges in the developmental stageswere ensuring: 1) bait delivery to target depths with cycle times (time from release to recovery) that were practical for fishing operations; 2) bait retention in the capsule (no drop-outs) on the descent phase of the cycle; 3) baits, upon release at target depth, were not drawn up the water column on the capsule recovery phase (from possible hook-ups and/or suction); and 4) the retention of baits on hooks post-release from the capsule was not affected by the mechanical release underwater. Operational trials with the final version of the capsule yielded satisfactory cycle times to depths of 6 - 10 m. All baits were retained in the capsule on the descent and released as required at target depths (n = 606 deployments). Bait retention on hooks post release from the capsule and retention on hooks hand-set at the surface (the conventional method) were statistically indistinguishable. The underwater bait setter is modular in construction and can be fitted to all types of vessel sterns.

Keywords

Seabird Bycatch, Longline Fisheries, Underwater Setting, Marine Engineering, Innovation, Co-Operative Research

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Anderson, A., Small, C., Croxall, J., Dunn, E., Sullivan, B., Yates, O. and Black, A. (2011) Global Seabird Bycatch in Longline Fisheries. Endangered Species Research, 14, 91-106. http://dx.doi.org/10.3354/esr00347
[2]	IUCN (2012) IUCN Red List of Threatened Species. www.iucn.redlist.org
[3]	Croxall, J.P., Prince, P.A., Rothery, P. and Wood, A.G. (1998) Population Changes in Albatrosses at South Georgia. In: Robertson, G. and Gales, R., Eds., Albatross Biology and Conservation, Surrey Beatty & Sons, Chipping Norton, 69- 83.
[4]	Poncet, S., Robertson, G., Phillips, R.A., Lawton, K., Phalan, B., Trathan, P. and Croxall, J.P. (2006) Status and Distribution of Wandering, Black-Browed and Grey-Headed Albatrosses at South Georgia. Polar Biology, 29, 772-781. http://dx.doi.org/10.1007/s00300-006-0114-9
[5]	IUCN (2014) IUCN Red List of Threatened Species. www.iucn.redlist.org
[6]	FAO (1999) International Plan of Action for Reducing Incidental Catch of Seabirds in Longline Fisheries. International Plan of Action for the Conservation and Management of Sharks. International Plan of Action for the Management of Fishing Capacity. FAO, Rome, 26.
[7]	Lokkeborg, S. (2011) Best Practices to Mitigate Seabird Bycatch in Longline, Trawl and Gillnet Fisheries Efficiency and Practical Applicability. Marine Ecology Progress Series, 435, 285-303. http://dx.doi.org/10.3354/meps09227
[8]	ACAP (2013) Report of the Seventh Meeting of the Advisory Committee. La Rochelle, 6-10 May 2013.
[9]	Melvin, E.F., Guy, T.J. and Read, L.B. (2014) Best Practice Seabird Bycatch Mitigation for Pelagic Longline Fisheries Targeting Tuna and Related Species. Fisheries Research, 149, 5-18. http://dx.doi.org/10.1016/j.fishres.2013.07.012
[10]	AAD (2006) Threat Abatement Plan for the Incidental Catch (or Bycatch) of Seabirds during Oceanic Fishing Operations. Australian Antarctic Division, Department of the Environment, Water, Heritage and the Arts, Hobart.
[11]	Prince, P.A., Huin, N. and Weimerskirch, H. (1994) Diving Depths of Albatrosses. Antarctic Science, 6, 353-354. http://dx.doi.org/10.1017/S0954102094000532
[12]	Rollinson, D.P., Dilley, B.J. and Ryan, P.G. (2014) Diving Behaviour of White-Chinned Petrels and Its Relevance for Mitigating Longline Bycatch. Polar Biology, 37, 1301-1308. http://dx.doi.org/10.1007/s00300-014-1521-y
[13]	Robertson, G., Candy, S.G. and Hall, S. (2013) New Branch Line Weighting Regimes to Reduce the Risk of Seabird Mortality in Pelagic Longline Fisheries without Affecting Fish Catch. Aquatic Conservation: Marine and Freshwater Ecosystems, 23, 885-900. http://dx.doi.org/10.1002/aqc.2346
[14]	McCullagh, P. and Nelder, J.A. (1989) Generalized Linear Models. 2nd Edition, Chapman and Hall, London. http://dx.doi.org/10.1007/978-1-4899-3242-6