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Some fishermen targeting tuna, swordfish and halibut in the southwest Atlantic are cutting the beaks off live albatrosses to free them from hooks, before tossing the birds back into the ocean to die.
The accidental catch of marine mammals, turtles and seabirds in fishing gear is one of the biggest causes of the global decline of these animals.
Lots of work in recent years has tried to limit or reduce the impact that commercial fishing has on these creatures, from lights and acoustic pingers on nets, to setting gear at night and reducing the profile of nets when they are in the water.
However, a worrying trend is emerging involving seabirds that are caught on the hooks of longline fishing equipment.
A picture posted on social media in 2015 showed a live albatross with the top half of its beak sliced clean off. This led to a group of researchers gathering as many records of this kind of seabird mutilation as they could. What they found revealed a worrying trend that has emerged in the south-west Atlantic Ocean.
Dr Alex Bond, Senior Curator in Charge of Birds at the Museum, has been involved in documenting these cases. His work has revealed that the practice is likely far more common than anyone suspected and dates back over two decades.
'It appears to be a very specific thing that fishermen in this region are doing,' explains Alex. 'It's clear that some operators are literally taking a blade and cutting the bill off to more expeditiously unhook the bird, and then tossing the bird overboard.'
The reports have been collated and published in the journal Biological Conservation.
Longline fishing is a technique used around the world to target a range of fish. It involves a length of cable with baited hooks spread out at regular intervals along it.
In the South Atlantic Ocean it is frequently used to fish for pelagic species, which live in the open water such as tuna and swordfish, although it is also used for deeper living species like hake and Patagonian toothfish.
Longline fishing can be a significant problem for seabirds like albatrosses. When the lines are being set, the birds will dive for the bait attached to the hooks and get caught themselves. When this happens there are safe ways for fishermen to help free the birds while reducing the risk of harm, something that Birdlife's Albatross Task Force teaches to fishermen around the world.
Some fisheries are not employing these techniques, and are instead taking a blade to the bill of these seabirds, including those that are considered to be endangered such as the northern royal albatross and the spectacled petrel.
Despite longlining occurring in much of the world's oceans this particularly brutal practice appears to be very localised.
'We put out a call out around the world for anyone who had any records of this kind of mutilation,' says Alex. 'The only places that came back with these cases were from the south-west Atlantic, so off the coasts of Brazil, Uruguay, Argentina and one or two from Chile.
'It could not be one group of people, just because of the sheer geographic and temporal extent.'
They found records of bills being cut off in eight different species of seabirds. The amount of damage ranged from either the top or lower bill having been removed to the entire beak having been removed, with the earliest record being from 1999.
Reports came in showed both of live birds with no bills spotted at sea, alongside sightings of dead birds on beaches.
Pelagic seabirds such as albatrosses and petrels are extremely wide ranging. Typically breeding on the islands that dot the southern oceans and along coastlines, they will travel great distances to feed and breed. They also live to more than 60 years old.
This means that there may be significant implications of this practice on the survival of albatross and petrels in the short and long term.
'These are high seas fleets operating far from shore,' explains Alex. 'So in order for any birds that do get thrown overboard and ultimately die to be recorded, they have to be washed up on a beach hundreds of miles away.
'This means that we don't know the true extent of the problem, but the fact that we are seeing it in this volume suggests that it is uncomfortably common.'
It also means that it is difficult to determine if and how albatross are able to survive such dramatic injuries.
'There is no way to tell how long these birds have had their injuries,' says Alex. 'It could have happened an hour ago, a year ago or five years ago, we simply don't know.'
This makes it tricky to understand how it might be impacting the long-term survival of such long-lived, wide-ranging species, although it is unlikely to be having any positive effect on them.
The discovery of this practice is particularly worrying given there are already a number of techniques used by fishing vessels to help limit the number of seabirds caught as bycatch.
One of these involves attaching pieces of pole to the lines that stick out and effectively prevent the birds from diving for the bait. In a similar vein, fishermen can add streamers to the cables as the hooks descend which also keeps the birds from going after them. Weighted hooks also help the baits sink more quickly, taking it out of the birds' reach sooner.
Finally, the lines can simply be deployed at night when seabirds such as albatrosses are not actively foraging.
'Ultimately, the way to prevent this practice is to increase education around safe handling practices of live birds that come aboard ship,' explains Alex.
This is something that is already being done by the Albatross Task Force, an international team of experts whose goal is to reduce the bycatch of the birds. They work onboard vessels and in ports and show the fishing crews how safely handle and remove birds from fishing gear.
Now that this brutal practice has been identified as a highly localised problem, it is hoped that targeted action can improve the outlook for birds in the south-west Atlantic.