Despite being introduced to reduce the amount of by-catch caused by trawling, longlining still attracts a variety of animals that are not their targets – albatrosses and other seabirds among them.
What is longlining?
Longlining attracts fish with a central fishing line that can typically be up to 100km long. Smaller lines of baited hooks are strung along the central line, which hang at spaced intervals. The bait used can either be small pelagic fish or artificial bait and the number of hooks depends on the length of the central line, but can amount to several thousand.
Pelagic longlines are designed to catch open ocean fish such as tuna and swordfish, and the hooks are hung near the surface, kept in position by buoys.
Demersal longliners float their hooks just off of the sea floor to catch fish such as cod and halibut that live on or near the bottom.
Longliners leave the line for a period of time to attract the fish and then return to haul in their catch.
What’s the problem?
The problem is that the baited hooks attract a variety of other animals aside from their targets, including birds. The birds reach for the bait (or the fish hooked on the bait) but eat the hooks, get pulled under water and drown.
According to the Sea Shepherd Conservation Society, as many as 100 million hooks a year are set by the Japanese fleet alone in the Southern bluefin tuna fishery and a conservative calculation for albatross killed on Japanese longliners is 44,000 per year.
Overall, BirdLife International states that more than 300,000 seabirds are killed this way each year.
What can be done?
Implementing solutions to reduce the amount of birds caught on the hooks will stop birds being needlessly killed, and also benefit fisherman because the more bait being eaten by birds, the smaller the catch of fish.
According to BirdLife International, a number of measures can be taken to prevent birds swallowing the baited hook, which are both cheap and easy to implement.
• Towing bird scaring lines behind the vessels (with plastic streamers tied to them that flap in the wind to scare the birds away from the baited line)
• Using an underwater setting tube. These set the fishing line underwater out of reach of the birds
• Tying enough weights to the fishing line so that it sinks more quickly out of reach of the birds
• Using thawed, not frozen, bait as it sinks more quickly
• Dying the bait blue, as it puts birds off eating it
• Setting the lines at night, as most albatrosses feed mainly by day
Other species affected
Aside from albatrosses and other sea birds, a number of other animals are caught by longline hooks.
Sea turtles are one species affected. According to the United Nations Food and Agriculture Organization (FAO), 40,000 sea turtles are killed annually in global longline fisheries.
This is an issue that could be avoided by sinking the longline deeper, avoiding the turtle’s migratory path.
Sharks are also caught in the process. Some organisations blame longlining for the reduction of shark populations by around 90%.
In May this year, Michael M. Herrmann from SharkDefense – a research company in New Jersey – won the WWF’s Internationational Smart Gear Competition for his idea to use a shark’s ability to to detect magnetic fields as a way to protect them. He found that placing strong magnets just above the baited hooks on a longline repels certain shark species, averting potential harm to the shark and the fishing gear.
Longline fishing is a very effective way of catching fish, and by taking the measures suggested in this article, unnecessary by-catch can be significantly reduced. For more information on reducing albatross by-catch, please visit www.savethealbatross.net
