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Trawl fisheries cause significant mortality to albatrosses

Black-browed Albatross: collisions between foraging birds and trawl cables often result in serious injury or death. © Peter Exley, RSPB

Trawl fisheries are a cause of significant levels of seabird bycatch when birds (primarily larger bodied albatrosses and petrels) collide with warp cables at the back of boats, and become entangled in nets during the later stages of hauling. Up to 40 species are thought to be affected, with 10’s of thousands estimated to be dying each year.


An illustration of how seabirds are caught by Trawl fisheries

While seabird bycatch in long-line fishing has been known since the 1980s, the threat posed by trawl fisheries has also become apparent in recent years (Bartle 1991, Weimerskirch et al. 2000, Sullivan et al. 2006). No global review of the impact of trawl fishing on seabirds has been undertaken, but there are a number of regional and national levels studies that highlight the significance of the problem (Wilson et al. 2004).

In Argentina, studies (Gonzalez-Zevallos et al. 2007, Yorio et al. 2010) on Magellanic Penguin Spheniscus magellanicus and Imperial Shag Phalacrocorax atriceps breeding at a newly designated marine park in Golfo San Jorge, assessed the potential spatial conflict between these seabirds and commercial hake and shrimp trawl fisheries. The observed foraging patterns suggest a high probability of spatial conflict and incidental mortality was regularly recorded in both fisheries, at rates that varied between 0.02 and 0.34 individuals per haul depending on species and fishery (Yorio et al. 2010).

In New Zealand, Bartle (1991) recorded an average bycatch catch rate of 0.263 birds/haul in a squid trawl fishery. 83% were recovered from the net sonde cable, with the remainder entangled in various parts of the net.

At Kerguelen, Weimerskirch et al. (2000) recorded a mean mortality rate of 0.48 birds/day on trawl vessels targeting toothfish Dissostichus eliginoides or mackerel icefish Champsocephalus gunnari. Higher rates were observed on vessels using net sonde cable and targeting the smaller icefish. Approximately 1/3 of mortality was caused by net sonde cable.

In Alaska, Zador et al. (2008) highlighted the potential year-round overlap of Short-tailed Albatross Phoebastria albatrus distribution and fishing areas of the vast Alaska groundfish trawl fishery, in which the catch of one of the target species, walleye pollock Theregra chalcogramma, is the second largest in tons among all fisheries.


Tracks of foraging Magellanic Penguin instrumented at Caleta Malaspina during the chick stage of 2006 (a and c) and 2007 (b and d), and spatial distribution of hauls made by hake trawlers (a and b) and shrimp trawlers (c and d) between November 15 and March 15 of the 2001–2007 fishing seasons at Golfo San Jorge, Argentina. Grey areas indicate the areas of high intensity use by hake and shrimp trawl fisheries (95, 75 and 50% kernel contours).

Yorio et al. (2010)

In the Falklands/Malvinas, Sullivan et al. (2006) estimated that >1500 seabirds, predominantly Black-browed Albatross Thalassarche melanophris, were killed by demersal (bottom) finfish trawlers in 2002/2003.

Historically the Bengula Current (covering the Exclusive Economic Zones of South Africa, Namibia and Angola, and adjacent international waters) has had high levels of seabird bycatch in trawl fisheries (Petersen et al. 2007, 2008). In 2005/06 it was estimated that 18,000 seabirds were killed in the South African hake trawl fishery, one of the first trawl fisheries in which this problem was identified (Watkins et al. 2008). In South Africa, it was estimated that 85% of birds were killed by the powerful warp cables that attach the trawl net to the fishing vessel, entangling particularly the long-winged albatrosses and dragging them under the water. The remaining 15% died entangled in nets during shooting and hauling (Watkins et al. 2008). Of the birds killed, 70% were Shy T. cauta and Black-browed Albatross T. melanophrys, 14% were Cape Gannet Morus capensis and 9% White-chinned Petrel Procellaria aequinoctialis. All of these species are globally threatened or near-threatened. BirdLife’s Albatross Task Force has been working with the trawl fleet in South Africa since 2006 to reduce this bycatch, and began work in Namibia in 2008. This work has succeeded in significantly reducing the scale of the problem in these areas.



Related Case Studies in other sections

Related Species

References

Bartle, J. A. (1991) Incidental capture of seabirds in the New Zealand Subantarctic Squid trawl fishery, 1990. Bird Conservation International 1, 351–359.
 
Gonzalez-Zevallos, D., Yorio, P., and Caille, G. (2007) Seabird mortality at trawler warp cables and a proposed mitigation measure: a case of study in Golfo San Jorge, Patagonia, Argentina. Biological Conservation 136: 108–116.
 
Petersen, S. L., Honig, M. B. and Nel, D. C. (2007) The impact of longline fisheries on seabirds in the Benguela Current Large Marine Ecosystem. Pp 9–31 in S. Petersen, D. Nel and A. Omardien, eds, Towards an ecosystem approach to longline fisheries in the Benguela: an assessment of impacts on seabirds, sea turtles and sharks. WWF South Africa Report (Series - 2007/Marine/001).
 
Petersen, S. L., Nel, D. C., Ryan, P. G., and Underhill, L. G. (2008) Understanding and mitigating vulnerable bycatch in southern African trawl and longline fisheries. WWF South Africa Report Series, 2008/Marine/002.
 
Sullivan, B. J., Reid, T. A., and Bugoni, L. (2006) Seabird mortality on factory trawlers in the Falkland Islands and beyond. Biological Conservation 131: 495–504.
 
Watkins, B. P. Petersen, S. L. and Ryan, P. G. (2008) Interactions between seabirds and deep-water hake trawl gear: an assessment of impacts in South African waters. Anim. Conserv. 11: 247–254.
 
Weimerskirch, H., Capdeville, D. and 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.
 
Wilson, B., Rivera, K., Fitzgerald, S. and Rose, C. (2004) Discussion paper on seabird interactions with trawl vessel gear. North Pacific Fishery Management Council, Protected Resources Report No.2, Anchor¬age, Alaska.
 
Yorio P., Quintana F., Dell’arciprete P. and Gonzalez-zevallos D. (2010) Spatial overlap between foraging seabirds and trawl fisheries: implications for the effectiveness of a marine protected area at Golfo San Jorge, Argentina. Bird Conservation International 20: 320–334.
 
Zador, S. G., Parrish, J. K., Punt, A. E., Burke, J. L. and Fitzgerald, S. M. (2008) Determining spatial and temporal overlap of an endangered seabird with a large commercial trawl fishery. Endang. Species Res. 5: 103–115.

Compiled 2008, updated 2013

Recommended Citation:
BirdLife International (2013) Trawl fisheries cause significant mortality to albatrosses . Presented as part of the BirdLife State of the world's birds website. Available from: http://birdlife.org/datazone/sowb/casestudy/167. Checked: 21/04/2014