Global fish production is at record levels thanks to fish farming, says the UN FAO, but much is wasted and many species are worryingly overfished

One in three fish caught around the world never makes it to the plate, either being thrown back overboard or rotting before it can be eaten, according to the UN Food and Agriculture Organization.

Its biannual report on the state of the world’s fisheries, released on Monday, also shows that total fish production has reached a record high thanks to more fish farming, particularly in China, with over half the fish eaten in the world now coming from aquaculture.

In contrast, the amount of wild caught fish has barely changed since the late 1980s and a third of commercial fish species are overfished, the FAO says. Fish farms will continue to expand and the FAO projects that almost 20% more fish will be eaten by 2030, helping sustain the growing global population. However, farmed fish can harm wild populations because often their feed, made from wild fish such as sardines and anchovies, is caught at sea and they can cause pollution.

Fish are a crucial source of nutrition for billions of people around the globe, but overfishing is rife in some regions, with two-thirds of species overexploited in the Mediterranean and Black Seas and the Southeast Pacific. Previous analyses that include estimates for illegal fishing indicate that wild fish stocks are declining faster than FAO data suggest and that half the world’s oceans are now industrially fished.

“Since 1961 the annual global growth in fish consumption has been twice as high as population growth, demonstrating that the fisheries sector is crucial in meeting the FAO’s goal of a world without hunger and malnutrition,” said José Graziano da Silva, FAO director general. Many challenges remain, he said, but recent initiatives to crack down on illegal fishing will mark “a turning point” in favour of long-term conservation.

The FAO reports that 35% of global catches are wasted. About a quarter of these losses are bycatch or discards, mostly from trawlers, where unwanted fish are thrown back dead because they are too small or an unwanted species. But most of the losses are due to a lack of knowledge or equipment, such as refrigeration or ice-makers, needed to keep fish fresh.

The FAO has worked with developing nations to cut losses, including the use of raised racks for fish drying, which resulted in a 50% cut in losses of fish from Lake Tanganyika in Africa. Around the Indian Ocean, better facilities for handling the crab harvest cut losses by 40%.

Aquaculture now dominates the fish people eat, providing 53% of the total recorded by the FAO in 2016, the latest data available (excluding fish not used as human food). Farming also dominates the fishing economy, providing two-thirds of the $362bn (£274bn) earned from sales at the dockside.

The FAO report sets out the huge scale of global fishing: it employs 60 million people and there are 4.6m fishing vessels on the planet. This huge effort is worrying in many places, the FAO says, with too many boats chasing too few fish.

As a result, the number of species being overfished has trebled in the last 40 years. The report also states that climate change will drive fish away from warm tropical waters, where nations are often especially reliant on seafood, towards more temperate regions.

Lasse Gustavsson, executive director of Oceana in Europe, said huge improvements were needed across the fishing industry. “Food waste on a hungry planet is outrageous,” he said. “The fact that one-third of all fish caught goes to waste is a huge cause for concern for global food security.”

On overfishing, particularly in the Mediterranean, he said: “We know the situation, we have the solutions: setting fish catch limits to scientific advice and stopping illegal and destructive fishing. All we’re missing is political action.”

Gustavsson added: “Aquaculture is far from being the magic bullet, as it is often unsustainable. Using 20m tonnes of fish like mackerel, sardines and anchovies to feed farmed fish instead of people is a blatant waste of food.”

Prof Daniel Pauly, at the Sea Around Us research initiative at the University of British Columbia, Canada, has been very critical of previous FAO reports, which he says significantly underestimated the total catch by failing to account for illegal fishing.

But he welcomed the new report for considering a much wider range of information: “The crisis of [overfishing] will be hard to solve. However, collaborations between different stakeholders may help turn around some of the negative trends. This is the best issue of [the FAO fisheries report] that I have ever read.”