The numbers 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 Wild Fund for Nature (WWF) conservation group said yesterday. Populations of some commercial fish stocks, such as a group including tuna, mackerel and bonito, had fallen by almost 75%, says a study by the WWF and the Zoological Society of London (ZSL).Marco Lambertini, director general of WWF International, said mismanagement was "pushing the oceans to the brink of collapse"."There is a massive decrease in species critical to both the ocean ecosystem and food security for billions," he said.The report said populations of fish, marine mammals, birds and reptiles had fallen 49% between 1970 and 2012. For fish alone, the decline was 50%.The analysis said it tracked 5829 populations of 1 234 species, such as seals, turtles and dolphins and sharks. It said the ZSL data sets were almost twice as large as past studies.Damage to coral reefs and mangroves, which are nurseries for fish, added to problems led by over-fishing. Other threats included coastal development, pollution and climate change - which is raising temperatures and making waters more acidic.The study said the world's fishing fleets were too big and supported by subsidies totalling $14-billion to $35-billion a year.Later this month, governments are to adopt new UN sustainable development goals, which including ending over-fishing and destructive fishing practices by 2020 and restoring stocks "in the shortest time feasible"...