Nearly 40 of the 73 species of sharks and rays assessed are threatened, with 31 of them evaluated as Critically Endangered and Endangered.

The conservation status of the sharks and rays in the Mediterranean Sea show no sign of improvement, experts warn.

This rapid decline in the number of shark and ray species in the Mediterranean waters is mainly due to overfishing, with most species being taken as bycatch, according to the report.

More than 50 percent of the sharks and rays native to the Mediterranean Sea are at a high risk of extinction, the International Union for Conservation of Nature (IUCN) announced Monday.

The major driver of their decline is overfishing, researchers say.

In the 2016 regional assessment of the Mediterranean Sea, experts from the IUCN evaluated the status of 73 species of sharks and rays in the region, and found that more than 50 percent of the species (22 of 41 shark species; 16 of the 32 species of rays) are threatened with extinction. Of these, 31 species are either Critically Endangered (20 species) or Endangered (11 species). The level of threat may be higher because the status of 13 species remains uncertain due to insufficient data.

The conservation status of the sharks and rays in the Mediterranean Sea show no sign of improvement, researchers warn. In fact, the status of 11 species, including Basking Shark, White Shark, Blue Shark, and Smooth Hammerhead Sharks, have worsened by at least one Red List category since their last assessment in 2007 .

Moreover, 13 species have become locally extinct in the Mediterranean waters over the last 50 years, the authors write. Most of these local extinctions have occurred in the North West Mediterranean waters of Spain, France, and Italy, and in the waters of the countries bordering the Adriatic Sea and northwest African countries.

This rapid decrease in the number of shark and ray species in the Mediterranean Sea is largely due to overfishing, the researchers say, with most species being taken as bycatch by fisheries targeting other species like swordfishes and tuna.

The use of illegal drift nets also continues to be intense and widespread throughout the Mediterranean Sea, the authors write, despite being banned in 2002. This is likely to be one of the most important — and largely hidden — source of mortality for sharks, they add.

“Governments need to support catch monitoring and data collection, regulate gears and establish fishing quotas and protected areas at domestic level. Consumers on the other hand need to be aware of the risk of what buying these products entails” Nick Dulvy, Co-chair of the IUCN Shark Specialist Group and researcher at Simon Fraser University in Vancouver, said in a statement.