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Barriers in a sea of sharks and rays

New James Cook University research about sharks and rays movements will be used in future marine decision making.

Scientists have studied 173 publications examining the genetic structure of 70 species of sharks and 32 species of skates and rays.

James Cook University PhD candidate Maximilian Hirschfeld, who led the study, says they found 45 unique marine barriers

“For example, deep ocean trenches, drastic changes in temperature and salinity, ocean currents, and even large river deltas, can limit genetic connectivity in sharks and rays at large to surprisingly small spatial scales,” he says.

He says some large oceanic species, such as plankton-feeding basking sharks, can maintain global connectivity.

But smaller species that live close to the seafloor and in shallow water can lack genetic exchange across deeper water at distances of less than 100 km.

“The impact of barriers on connectivity also depends on the ecology of individual species," he says.

"We found that ecological factors, including the habitat a species lives in, how deep it can dive, and its body size, are good indicators for its capacity to move across potential barriers."

With a third of the world's shark population under threat the research will be used in future decision making.


Photo credit: Maximilian Hirschfeld