Identifying fishery risk zones for seabird populations

Part of our Spotlight, Management of wide-ranging species, Thomas A. Clay explains how advances in remote tracking technology are offering us a glimpse into the mysterious life of the albatross in the hope of developing conservation measures to protect seabirds from bycatch risks.

The authors have adapted this post from an article they previously shared with BirdLife International.

Albatrosses are iconic voyagers, well known for their ability to glide on ocean winds with barely a flap of their wings. Their perilous association with fishing boats, made famous by Samuel Taylor Coleridge’s The Rime of the Ancient Mariner, has put some species at risk of extinction. Birds are frequently caught on baited fishing hooks or break their wings colliding with cables that drag trawl nets – known as incidental mortality or bycatch.

Over the last three to four decades, industrial fisheries have expanded into far-flung oceans in search of lucrative fish such as bluefin tuna. Larger fishing areas and more fishing vessels mean a likelihood of fatal interactions between boats and hooks, and birds. It is estimated that around 100,000 albatrosses and petrels are killed each year by longline fisheries alone. Many breeding populations, such as those on Bird Island, South Georgia (below), have more than halved over this period.

Before and after
A colony of grey-headed albatrosses on Bird Island, South Georgia, taken from the same position almost 40 years apart (in 1979 and in 2017). Since the late 1970s, numbers have decreased by over 75%, mostly as a result of unsustainable fishing practices and climate change. The two photos were taken at approximately the same time of year, when birds are incubating their eggs. © British Antarctic Survey

Albatrosses are extremely long-lived – they can live for over sixty years. Spending 95% of their time at sea means their lives have been somewhat a mystery to us. Gaps in our understanding of where birds go when at sea have prevented accurate assessments of the threats posed by fisheries. Today, advances in remote tracking technology, such as GPS, make it possible for scientists to gather detailed information about their movements and feeding habits.

A group of scientists from the British Antarctic Survey, the RSPB and BirdLife International in the UK, CSIRO in Australia and Dalhousie University in Canada, teamed up to join pieces of the puzzle. In a recent study, published in Journal of Applied Ecology, we combined information on seabird locations with fishing activity to determine where and when birds are most at risk from bycatch.

Wandering albatross w. geolocator_Richard Phillips
A wandering albatross with a geolocator attached to its leg band. The device weighs less than 5g and records the bird’s position during its long migration around the Southern Ocean. © Richard Phillips

Over the last two decades, dedicated field assistant have attached miniature electronic tags to birds to record their movements. The tags are placed either on the back feathers (weighing less than 50g) or are attached to rings on the legs of birds (less than 5g). We used these the information collected to create monthly maps of seabird densities which were compared to maps of fishing activity to predict ‘hotspots’ of risk.

After tracking almost 800 individual birds from four species, we learnt that albatrosses are at highest risk of bycatch during the southern hemisphere winter, and these risk zones were mainly located in the south Atlantic and Indian Oceans. When we looked at which fishing nations were responsible, Taiwan and Japan stuck out, together representing 70-80% of risk scores (depending on the species). These fleets target high-value tuna such as bluefin – individual fish can sell for over £1 million in Tokyo’s fish market. Yet only a small percentage (<5%) of vessels are independently monitored, so little is known about levels of seabird bycatch and whether appropriate conservation measures are used to protect them.

Maps showing annual predicted bycatch risk for four seabird populations from Bird Island, South Georgia, with red colours indicating greatest risk.

Ultimately, our hope is that this research will allow for greater regulation and accountability for fishing fleets. Fortunately for seabirds, there are a variety of ways to reduce bycatch to negligible levels. Fleets can cast their baited fishing lines at night when birds aren’t feeding, reducing the risk of birds swallowing the hooks. Flapping streamers next to fishing lines and trawl cables act like a scarecrows, discouraging albatrosses and petrels from approaching and, reducing fatal interactions.

Co-author on the study, Professor Richard Phillips at British Antarctic Survey, says:

A suite of bycatch-reduction measures are available that can be extremely effective when used properly, for example in the toothfish fishery around South Georgia. However, South Georgia seabird populations continue to decline at alarming rates which indicates the failure of many fisheries elsewhere in the southern hemisphere to take full responsibility for impacts on seabirds and to become truly eco-friendly.

The main challenge is enforcement. Dr Cleo Small who leads the BirdLife International Marine Programme (hosted by the Royal Society for the Protection of Birds) and a co-author of the paper, says:

Having enough ship-based observers can be difficult for large fleets operating in the high seas, but electronic solutions now exist, including tamper-proof video monitoring and satellite-surveillance to detect breaches. Action needs to be taken now by fisheries managers to ensure bycatch mitigation is mandatory and that there is independent monitoring of compliance, particularly targeted at the areas, times of year and fleets with which birds overlap the most.

In the short term, seabird numbers continue to fall but in recent years there has been substantial progress. The Albatross Task Force, established in 2005 by the RSPB and BirdLife to reduce bycatch in target fisheries in South America and southern Africa, have seen albatross bycatch reduced by 99% in some fishing fleets. Through engagement with the fishing community and enforcement of regulations, the unnecessary deaths of these iconic species can be halted. In the meantime, identifying problem ‘hotspots’ and fishing nations responsible, will enable resources to be better targeted to maximise conservation success.

Read the full, open access paper, A comprehensive largescale assessment of fisheries bycatch risk to threatened seabird populations in issue 56:8 of Journal of Applied Ecology. This work features as part of a Spotlight on the management of wide-ranging species.



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