We were pleased to contribute whale shark tracking data to assist with a new global study led by the Marine Biological Association. For the full press release please click here, an excerpt is provided below:
Even the remotest parts of the ocean appear to offer highly migratory sharks little refuge from
industrialised fishing fleets, a ground-breaking study published in the journal Nature reports.
Blue shark | photo credit: Neil Hammerschlag
Large sharks inhabiting the open ocean account for over half of all identified shark catch globally in
target fisheries or as bycatch. Regional declines in abundance of some populations such as shortfin
mako shark – the fastest shark in the sea – have led to widespread calls for catch limits in the High
Seas (areas beyond national jurisdiction; ABNJ) where there is currently little or no management for
But precisely where in the vast expanse of the oceans sharks aggregate and how much fishing takes
place in those chosen habitats remains poorly known globally, even though it will be crucial to
selecting sites to conserve sharks.
Now, an international team of over 150 scientists from 26 countries have tackled this knowledge gap
by collating movement data from nearly 2,000 sharks tracked with satellite transmitter tags.
Researchers mapped shark positions and revealed ‘hotspots’ of space use in unprecedented detail.
They found multi-species pelagic shark hotspots were mostly located in frontal zones, boundaries in
the sea between different water masses that are highly productive and food-rich.
They then calculated how much the hotspots were overlapped by global fleets of large, longline
fishing vessels – the type of fishing gear that catches most pelagic sharks – with each vessel capable
of deploying 100 km long lines bearing 1200 baited hooks on a daily basis.
Tiger shark | photo credit: Neil Hammerschlag
Strikingly, they found 24% of the mean monthly space used by sharks globally falls under the
footprint of pelagic longline fisheries. For commercially exploited sharks such as North Atlantic blue
and shortfin makos sharks overlap was much higher, with on average 76% and 62% of their space
use, respectively, overlapping with longlines each month. Even internationally protected species
such as great white and porbeagle sharks had overlap values exceeding 50%.
“Our results show major high seas fishing activities are currently centred on ecologically important
shark hotspots worldwide” says Professor David Sims, who led the study as part of the Global Shark
Movement Project based at the Marine Biological Association Laboratory in Plymouth, UK.
Equally alarming was that shark hotspots showing high overlap with longline fishing were often also
subjected to high fishing effort, a potential ‘double whammy’ for sharks that will result in higher
catch rates and potentially accelerate declines in abundance.
“Some shark hotspots were exposed to higher than average fishing effort for as much as half the
year” said Dr Nuno Queiroz, a lead researcher in the study from the University of Porto in Portugal.
Given the high fishing effort in hotspots of many species for significant portions of the year, and the
very few tracked hotspots free from exploitation, the study reveals exposure risk of sharks to
fisheries in the high seas is spatially extensive – stretching across entire ocean-scale population
ranges for some species.
The team’s findings indicate large sharks – some of which are already endangered globally – face a
future with limited spatial refuge from industrial longline fishing effort.
The researchers propose that the detailed maps of shark hotspots and exposure to longline fishing
effort they have produced can provide a ‘blueprint’ for use in deciding where to place large-scale
marine protected areas (MPAs) aimed at conserving sharks, in addition to the need for strict quotas
to reduce catches elsewhere.
“Some of the shark hotspots we studied may not be there in as little as a few years’ time if
management measures are not put in place now to conserve the sharks and the habitats on which
they depend” Sims says.
The research was published online in Nature on 24th July 2019.
Corresponding author of the research: Prof David Sims, MBA Laboratory, Plymouth, UK.
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Guy Baker, Communications Co-ordinator
Marine Biological Association (MBA), The Laboratory, Citadel Hill, Plymouth, Devon, PL1 2PB,
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