14 Aug 2019

Tracking down threats

How tracking technology is improving our understanding of threats to seabirds

A Light-mantled Albatross, one of many at risk of bycatch, in flight. © Oli Prince
By Thomas Clay

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 have increased the 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.

Two photos, 40 years apart, show the decline of albatrosses on bird island © 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 recently published in the 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.

Over the last two decades, dedicated field assistants 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 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.

Ultimately, the 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, or use weights on lines so that they sink quicker, reducing the risk of birds swallowing the hooks. Flapping streamers next to fishing lines and trawl cables act like a scarecrow, discouraging albatrosses and petrels from approaching and, reducing fatal interactions.

“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,” says Professor Richard Phillips, a co-author of the study from the British Antarctic Survey. “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.

“Having enough ship-based observers can be difficult for large fleets operating in the high seas,” says Dr Cleo Small, who leads the BirdLife International Marine Programme. “Electronic solutions now exist though, 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.”

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.