Industrial Fishing Behind The Number Of Sharks

Editorials News | Aug-13-2019

Industrial Fishing Behind The Number Of Sharks

A team of researchers, led by the international conservation charity ZSL (London Zoological Society), discovered that sharks are much rarer in habitats closer to large human populations and fish markets. The team also discovered that the average body size of sharks and other marine predators decreased dramatically in these areas, where sharks are caught and killed intensely for their meat and fins.
The study, published today in the journal PLOS Biology, shows that average body size and the number of sharks and other marine predators, vital for maintaining healthy ocean ecosystems, decreased significantly in the proximity of cities with more than 10,000 people and fishing fleets. associated.
The minimum distance of people and fishing that had no measurable effect was 1,250 kilometers. This goes far beyond what previous studies have suggested and probably reflects the increase in distances that fishing boats can now travel. As a result, sharks were only observed in 12% of the monitored sites.
Interestingly, the researchers also found that sea surface temperature had a strong influence on the average body size of predators, with a marked decrease to more than 28 ° C. While this is consistent with normal biogeographic patterns, it is known that many smaller species live in tropical waters. It could become a problem as global temperatures continue to rise.
The lead author, Dr. Tom Letessier, from the ZSL Institute of Zoology, said: "Human activity is now the biggest influence on shark distribution, surpassing all other ecological factors. Only 13% of the oceans of the world can be considered 'wild', but sharks and other predators are much more common and significantly larger at distances greater than 1,250 kilometers from people. This suggests that large marine predators generally cannot thrive near people and it is another clear example of the impact of human overexploitation in our seas. "
To collect their data, the team analyzed video images taken at 1,041 sites in the Indian and Pacific oceans, selected to test the widest possible range of conditions and habitats. The sites varied in proximity to fish markets and human populations, with some near cities and others at up to 1,500 kilometers. Sharks, and other predators that swim freely, were studied with cameras connected to boats filled with bait. In total, the team recorded 23,200 animals representing 109 species. These included 841 individual sharks of 19 different species.
From the monitoring of the coral reefs that surround the British Indian Ocean Territory (BIOT) to the protection of the last breeding grounds of angels in critical danger of extinction, ZSL is committed to preserving ocean and life habitats wild they sustain. Only one year after the end of the UN Aichi Biodiversity objectives, there are considerable deficiencies in the current location of Marine Protected Areas (MPAs).
Dr. Letessier added: "Our study also found that shallow water habitats, of depths less than 500 meters, were vital to the diversity of marine predators. Therefore, we need to identify sites that are both shallow and remote and prioritize them for conservation, however, there are still many shallow access points in the vicinity of human markets that are not adequately protected, and this must change. The existing large and uncaptured MPAs must be enforced and extended better to focus in the last shelters where these extraordinary animals are still abundant.

By: Preeti Narula
Content: https://www.sciencedaily.com/releases/2019/08/190806142332.htm


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