A new study shows how industrial fishing zones are increasingly overlapping with shark hotspots, leaving these animals little space in the open ocean to avoid the threat of capture.
In the past, most fishing activity was concentrated in coastal areas. But from the 1950s onwards, industrial fishing fleets expanded their range into the open ocean, raising concerns for the marine species that inhabit this environment, such as sharks. Pelagic sharks that live in the open ocean account for more than half of all shark species and, as apex predators at the top of the food chain, play a fundamental role in maintaining marine ecosystems.
Read also: The world fishes far more than we think
In a recent study published in the journal Nature, a team of more than 150 scientists from 26 countries compiled a large dataset of observations obtained by tracking more than two thousand sharks across the world's oceans. By studying the movements of these animals, the scientists identified areas, known as "shark hotspots", where many shark species congregate. These hotspots are found in productive regions such as the Gulf Stream and the California Current. The team then analysed the overlap between shark hotspots and the global distribution of fishing activity, in particular industrial longlining. This technique involves the use of lines up to one hundred kilometres long, to which hundreds, if not thousands, of baited hooks are attached. Longlines are responsible for the greatest number of shark catches, both for commercial purposes and unintentionally (bycatch).
The study's findings are alarming: longlining areas overlap considerably, both spatially and temporally, with habitats important to sharks: 24 per cent of the space occupied by sharks on a monthly basis falls within the range of these activities. The highest levels of overlap are recorded for commercially exploited species (up to 76 per cent for the blue shark), but internationally protected sharks are also at high risk (overlap of up to 64 per cent for great white sharks). Unfortunately, the regions least exploited by industrial fishing are also those least frequented by sharks, suggesting that the safe areas remaining for these species are becoming increasingly limited.
Read also: Galápagos: a new reserve created to protect sharks
The study concludes with a call for timely action and adequate protective measures. Establishing large marine protected areas around the hotspots is no easy task, and enforcing bans in these remote zones presents many complexities, but there are innovative technologies that could help. For instance, satellite tracking of both sharks and fishing vessels could be used to develop dynamic fishing bans for specific areas. Without swift, targeted interventions to protect these species and their habitats, shark hotspots are at risk of disappearing in the near future.
Translated by Patrick Bracelli
