Since 1970, “relative fishing pressure” (exploitation of fish stocks relative to the number of fish left) has increased 18-fold – and the researchers say catch limits are now urgently needed to “avert population collapse”.

The study reveals an alarming 71% decline in shark and ray populations over the last 50 years, primarily due to overfishing. All the oceanic shark and ray species, except for the Smooth Hammerhead, decreased in abundance over the last half-century. Some formerly abundant, wide-ranging sharks – including the Oceanic Whitetip and Great Hammerhead – have declined so steeply that they are now classified as critically endangered.

A few bright spots in the data demonstrate that even these long-lived animals can recover when science-based fishing restrictions are enacted and enforced.”

The paper highlights some positive changes, including the recovery of White Sharks in several regions, and signs of population growth among Northwest Atlantic Hammerheads. These improvements appear to have been caused by strictly enforced fishing rules – and the researchers say further science-based catch limits and landing bans are needed immediately.

They conclude: “These steps are imperative for long-term sustainability, including potentially increased catch once populations are rebuilt, and a brighter future for some of the most iconic and functionally important animals in our oceans.”

The study is a project of the Global Shark Trends Project (GSTP), a collaboration of the IUCN Shark Specialist Group, Simon Fraser University, James Cook University and the Georgia Aquarium, established with support from the Shark Conservation Fund to assess the extinction risk for chondrichthyan fishes (sharks, rays and chimaeras).

The paper, published in the journal Nature, is entitled: “Half a century of global decline in oceanic sharks and rays”.

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