Abstract
Experimental trials were conducted onboard a stern trawler to identify the relative efficacy of three emerging mitigation measures (tori lines, warp scarer and Brady baffler) designed to reduce seabird mortality caused by warp cable strikes. The use of mitigation measures was clearly shown to substantially reduce seabird mortalities from collisions between seabirds and warp cables. Based on an established significant relationship between contact rate and seabird mortality, when using contact rate as an index of mortality there was a clear performance hierarchy of the three measures. Tori lines and the warp scarer were significantly more effective at reducing contacts than the Brady Baffler, whilst tori lines represent a smaller, but still significant, improvement on the warp scarer. While further testing would be required under local environmental and operational conditions, our findings are likely to have application for many trawl fisheries around the world.
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Notes
Paravanes contain transducers for net monitoring equipment. They are typically suspended just below the surface near the stern of a vessel
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Acknowledgements
The Falklands Conservation Seabirds at Sea Team’s component of the trials was jointly funded by the International Association of Antarctic Tour Operators (IAATO) Save the Albatross Fund, the Falkland Islands Government, Fortuna Ltd., and Peter Harrison MBE and we appreciate their support. The support of the Falkland Islands Fisheries Department (FIFD), especially John Barton MBE (Director of Fisheries) has been critical to these trials. Thanks also to the crews of the Fishery Patrol Vessels Dorada and Sigma, and operators Byron Marine, for transfers. Thanks also to the Australian Antarctic Division and Australian Fisheries Management Authority for supporting our use of their data collection protocols. Tim Stenning provided line drawings and his assistance constructing the warp scarer was vital. Dr. David Agnew (Renewable Resources Research Group, Imperial College) and Dr. Graham Robertson (Australian Antarctic Division) provided helpful feedback on earlier analyses of these data. We are particularly grateful to the management Golden Touza Ltd. and the crew of the Hermanos Touza, particularly Alberto Vazquez (Captain) and Angel (Bosun) for their assistance and support.
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Appendices
Appendix 1
Contact codes describing interactions between seabirds and trawlers (AFMA protocol; Wienecke and Robertson 2002) .
Field | Code | Definition |
---|---|---|
Age | A | Adult |
SA | Sub-adult | |
Ja | Juvenile | |
Contact code (birds) | 1 | Bird on water, very light contact with vessel/gear |
2 | Bird on water, heavy contact with vessel/gear, causing at least part of the bird to be dragged underwater | |
3 | Bird flying, light contact with vessel/gear, bird does not deviate from course | |
4 | Bird flying, heavy contact with vessel/gear, bird deviates from course and/or dragged underwater | |
5 | Bird snagged on loose wire ends (eg. splice ends) | |
6 | Bird has high speed collision with vessel gear | |
7 | Bird caught in net | |
8 | Bird snagged on net while attempting to feed | |
9a | Bird hauled on trawl door | |
Contact point | 1 | Warp wire |
2 | Trawl doors | |
3 | Backstops, brides and sweeper | |
4 | Net | |
5 | Vessel | |
6 | Paravanes (includes towing wires) | |
7a | Ropes on bird scaring device | |
8 | Other | |
Fate of bird | 1 | No apparent damage |
2 | Possible minor injury | |
3 | Possible major injury | |
4 | Death | |
5 | Unknown | |
6a | Bird seen wrapped around warp wire (suspected death) |
Appendix 2
Environmental variables recorded during observation periods .
Variable | Code | Level |
---|---|---|
Relative wind direction | 1 | Ahead |
2 | 45° | |
3 | 90° | |
4 | 135° | |
5 | Stern | |
BBA abundance | 1 | 1–10 |
2 | 11–50 | |
3 | 51–200 | |
4 | 201–500 | |
5 | 501+ | |
6 | Present | |
Sea state (Beaufort scale) | 1 | ≤2 |
2 | 3 | |
3 | 4 | |
4 | ≥5 | |
Sea height (m) | 1 | 0 |
2 | >0,<0.5 | |
3 | ≥0.5 | |
Swell (m) | 1 | 0 |
2 | 0.5 | |
3 | >0.5,<1 | |
4 | 1 | |
5 | >1 |
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Sullivan, B.J., Brickle, P., Reid, T.A. et al. Mitigation of seabird mortality on factory trawlers: trials of three devices to reduce warp cable strikes. Polar Biol 29, 745–753 (2006). https://doi.org/10.1007/s00300-006-0111-z
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DOI: https://doi.org/10.1007/s00300-006-0111-z