The worldwide average of fish consumption is just over 16 kilos a year, but in China the average person will get through almost twice that.

Every year, there is a three-month ban on fishing to allow stocks to breed and recover, but it has done little to stop a massive decline.

Fishermen themselves blame pollution, but environmental experts say overfishing has in particular decimated the numbers of mature adult fish and has made many varieties almost impossible now to find.

For locals in Ningbo, the annual sight of the boats once again setting out into the Pacific Ocean at the start of the fishing season is a good reason for a day trip out.

But for the fishermen themselves, the start of the season is unlikely to bring good news.

Catches of the four main species – the Japanese Spanish mackerel, eel and the large and small yellow croaker – have plummeted.

In the past, a successful fishing trip might have netted hundreds of kilograms of the large yellow croaker, but according to one captain most fishermen only get a few a year now, meaning prices were now forty or fifty times as much.

Mo Zhaolan, a researcher at China’s Institute of Oceanology, said that overfishing and pollution were having a much bigger impact than a decade ago.

Once large and valuable fish have been overfished, attention turns to a less valuable species, with the process continuing until all species have been over-exploited, fisheries depleted and biodiversity irreparably damaged.