China is the world's top seafood consumer, followed by Japan and the United States, a trio leading an "unsustainable" assault on global fish stocks, according to a new study which measures the impact of fishing practices.

China, Japan, US top list of world seafood consumers: study

The study, written up in October's National Geographic magazine, found that China's enormous population gives it the world's biggest "seafood print" -- 694 million metric tonnes of the sea's resources consumed each year.

Japan has a seafood print of 582 million metric tonnes while the United States consumes about 348.5 million metric tonnes of the sea's resources.

The figures are not the raw tonnage of fish and shellfish consumed by a nation: the study measures what the researchers called "primary production" of seafood -- a figure weighted to reflect not only the total amount of seafood consumed, but also the place each seafood species occupies on the food chain.

The novel SeafoodPrint study, sponsored by the magazine along with the Pew Charitable Trusts, allows researchers to take into account the amount of smaller fish and other organisms at the bottom of the marine food web in assessing the environmental impact of seafood consumption.

The United States ranks high on the list, for example, because Americans prefer top predators such as Atlantic salmon and bluefin tuna.

"Every fish is different," said Daniel Pauly, a fisheries scientist at the University of British Columbia and one of the lead researchers on the study.

"A pound (0.45 kilograms) of tuna represents roughly a hundred times the footprint of a pound of sardines," he said in a press release.

The researchers also found that a pound of bluefin tuna might require 1,000 pounds (454 kilograms) or more of primary production.

The report found that fishing fleets each year harvest more than 170 billion pounds (78 million metric tonnes) of wild fish and shellfish -- from the oceans, and that this so-called "world catch" is essentially unfair and becoming increasingly difficult to sustain without risking a future global collapse in fishing stocks.

"These quantities are not just extremely large but also fundamentally unsustainable," the report says, noting that wealthy countries are monopolizing fisheries in the developing world by snapping up their most high-value species, essentially denying people in poorer countries access to the very fish their citizens are catching.

Among its recommendations, the study advocates reducing the world's fishing fleets by half, establishing large no-catch zones, and limiting the use of wild fish as feed in fish-farming to reduce the impact of the seafood industry on the world's fish stocks.

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