Sharks under threat because of global fisheries, study says
CANBERRA, Australia — About a quarter of shark habitats are actively targeted by global commercial fishing fleets, leaving the predators with limited places to hide from the longlines, or baited hooks, on which they frequently get caught, according to study published Wednesday.
The researchers found areas frequented by protected species had much higher overlap with active fishing zones where longlines were used, directly threatening the iconic ocean predators.
Longlining is a commercial fishing technique that uses a drifting long line with baited hooks attached on shorter branch lines at intervals. Hundreds or thousands of baited hooks can hang from a single line that mostly target species like tuna and swordfish.
The study by a team of Australian and international researchers was published in the science journal Nature.
The researchers tracked the movements of 1,600 sharks using satellite tags and monitored the movements of global fishing fleets to see where their paths crossed.
They found that 24% of the space used by pelagic, or oceanic, sharks in an average month falls under the footprint of longline fisheries, while areas frequented by protected species, like great white sharks, had an even higher overlap — 64% — with longline fleets.
Pelagic sharks are highly migratory, covering vast ocean areas. On average, large pelagic sharks account for half of all identified shark catch worldwide in target fisheries or as bycatch.
The researchers said the findings indicated that pelagic sharks have limited places of refuge from fisheries and thus more protected areas are needed urgently to sustain their declining population.