Half of oceanic shark and ray species are at risk of extinction because of severe overfishing, according to an international study that is calling for new government safeguards.

Findings of the study by the International Union for the Conservation of Nature (IUCN) Shark Specialist group are published in the latest edition of Aquatic Conservation: Marine and Freshwater Ecosystems and was released last week.

The findings show that 16 of 21 species are caught in high seas fisheries and are targeted for their valuable fins and meat, to meet a growing demand in Asia for shark fin soup.

Simon Fraser University biologist Nicholas Dulvy, the paper’s lead author, says the current rate of biodiversity loss is 10 to 100 times greater than historic extinction rates.

He says the findings are only a "first cut" and that estimates remain "conservative," noting that some areas of the Indian Ocean and southern Atlantic Ocean haven’t been accounted for.

Dulvy puts the loss of individual sharks and rays at between seven and eight million a year. "We’ve suspected that these species have been in big trouble for awhile," he says.

The study looked at data compiled at regional workshops around the world that would help decipher the link between catch rates and productivity of the species.

Once brought together, the information formed an alarming picture, says Dulvy.

In addition: "It takes a long time for these animals to become sexually mature and they produce few offspring, so recovery from overfishing is no easy task," he notes.

Dulvy says fisheries managers and officials in all levels of government have an opportunity and obligation to reverse the rate of loss of biodiversity. "With sufficient public support and resulting political will, we can turn the tide," he says.