The amount of fish in the oceans has halved since 1970, in a plunge to the “brink of collapse” caused by over-fishing and other threats, the World Wildlife Federation conservation group said on Wednesday.

Populations of some commercial fish stocks, such as a group including tuna, mackerel and bonito, had fallen by almost 75 percent, according to a study by the WWF and the Zoological Society of London.

Marco Lambertini, director general of WWF International, told Reuters mismanagement was pushing “the ocean to the brink of collapse”.

“There is a massive, massive decrease in species which are critical”, both for the ocean ecosystem and food security for billions of people, he said. “The ocean is resilient but there is a limit.”

Click here for the full report.