A new study found that are sharks are much rarer in habitats near large human populations and fish markets.
A team of researchers, led by the Zoological Society of London, found that that the average body size and number of sharks and other marine predators fell significantly in proximity to cities with more than 10,000 people and associated fishing fleets. Their finding were published in the most recent journal of PLOS Biology.
“Human activity is now the biggest influence on sharks’ distribution, overtaking every other ecological factor,” Lead author Dr. Tom Letessier, of ZSL’s Institute of Zoology, said. “Just 13% of the world’s oceans can be considered ‘wilderness’ but sharks and other predators are much more common and significantly larger at distances greater than 1,250 kilometres from people. This suggests that large marine predators are generally unable to thrive near to people and is another clear example of the impact of human overexploitation on our seas.”
The research team recorded 23,200 animals representing 109 species using video recorded around baited canisters at 1,041 sites across the Indian and Pacific Oceans. These sites were chosen based on proximity to fish markets and human populations, where sharks are caught and killed intensively for their meat and fins.
“Our study also found that shallower water habitats, of depths less than 500 metres, were vital for marine predator diversity. We therefore need to identify sites that are both shallow and remote and prioritise them for conservation,” Dr. Letessier said. “However, there are still numerous shallow hotspots in the vicinity of human markets that are not appropriately protected, and this must change. Existing large, no-take MPAs need to be better enforced and extended to focus on the last refuges where these extraordinary animals remain abundant.
“Large marine predators—and sharks in particular—play a unique and irreplaceable role in the ocean ecosystem. They control populations of prey species, keep those populations healthy by removing sick or injured animals, and transport nutrients between loosely connected habitats over vast distances.”
