Conservation efforts are about to become serious for sharks and rays, as one-quarter of their population is in danger of extinction within the next few decades.

In a new study, the International Union for Conservation of Nature's (IUCN's) Shark Specialist Group (SSG) authored a study to definitively reveal the status of cartilaginous fish. According to a press release, the study appears in the journal eLife Thursday.

SSG co-chair and Simon Fraser University Canada Research marine biologist Nick Dulvy, study lead author, said this study is the first to examine costal sea and ocean populations. Where previous studies only calculate overfishing of sharks and rays, this one shows 249 of 1,041 populations of shark, ray and chimaera fell under the global ICUN red list.

"We now know that many species of sharks and rays, not just the charismatic white sharks, face extinction across the ice-free seas of the world," Dulvy said in the release. "There are no real sanctuaries for sharks where they are safe from overfishing."

For the 20-year study, the researchers used ICUN's red list to examine the 1,041 different populations. Some 300 experts looked at the data at 17 workshops, weighing all sorts of factors like distribution, catch, abundance, population trends, habitat use, life histories, threats and conservation measures.

The researchers identified the Gulf of Thailand, the Red Sea and the Mediterranean Sea as three main problem areas for shark and ray population.

"In the most peril are the largest species of rays and sharks, especially those living in relatively shallow water that is accessible to fisheries. The combined effects of overexploitation-especially for the lucrative shark fin soup market-and habit degradation are most severe for the 90 species found in freshwater," said Dulvy. "A whole bunch of wildly charismatic species is at risk. Rays, including the majestic manta and devil rays, are generally worse off than sharks. Unless binding commitments to protect these fish are made now, there is a real risk that our grandchildren won't see sharks and rays in the wild."

He said the loss of the seas biggest predator would be devastating for the underwater ecosystem. The ICUN SSG is trying to protect the populations by urging governments to prohibit fishing the most endangered species, certain fishing quotas and guards against specific habitats.

"They are the only living representatives of the first lineage to have jaws, brains, placentas and the modern immune system of vertebrates," said Dulvy. "The biggest species tend to have the greatest predatory role. The loss of top or apex predators cascades throughout marine ecosystems."