The state of our oceans

Trawl catch

A trawl catch.

Credit: Mike Gerner/AFMA

Scallop dredge

A scallop dredge after being dragged along the bottom of the sea floor.

Credit: Mike Gerner/AFMA

Tuna in tow

A school of Southern bluefin tuna swim in a tuna fishery tow cage.

Credit: Getty images

Japan Tuna Market

Fishmongers check the quality of meat on frozen tuna fish before trading at Tokyo's Tsukiji fish market.

Credit: Getty Images

Hammerhead killed in net

A hammerhead shark is fatally caught in a gill net.

Credit: Getty Images

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All this talk about tuna

One type of fishing technique has attracted more criticism from conservationists than any other. Purse seine nets, sometimes the size of city-blocks, are hung in the water at shallow depths and are popular in tuna fisheries.

A 2003 report from the Australian Department of Agriculture, Fisheries and Forestry found that when Fish Aggregating Devices (floating shades which encourage schools of fish to gather) were used with these nets, bycatch rates in tuna fisheries were as high as 10 per cent.

Earlier this year, Greenpeace released a report entitled Out of Stock, Out of Excuses, documenting a litany of environmental disasters related to the tuna fishing industry in the Pacific, where at least half the world's tuna is produced. Of the region's seven tuna species, big-eye, yellowfin and albacore were already overfished and stocks of Southern bluefin tuna had collapsed. Only the region's skipjack stocks were sustainable.

If this wasn't bad enough, the report cites evidence that purse seine and longline tuna fishing are having an unacceptable impact on other species. Boats using longlines, some more than 100 km in length with as many as 3,000 baited hooks, were recording bycatch rates as high as 35 per cent, with sharks and seabirds being affected. Some 250,000 loggerhead turtles and 60,000 leatherback turtles are caught this way every year, with thousands killed.

Southern bluefin tuna, listed as critically endangered by the IUCN, continues to be fished in South Australia at a rate of 5,000 tonnes of mainly juvenile fish a year.

Last year the Commission for the Conservation of Southern Bluefin Tuna, which sets global catch limits, announced that stocks of adult fish were down to between three and eight per cent of their original state, well below the 20 per cent considered safe by the commission. A reduction to the global quota from 11,810 tonnes to 9,449 tonnes has since been introduced.

These juvenile Southern bluefin tuna caught in South Australia are placed into pens in the Port Lincoln area and fed mainly fish meal before being exported to the lucrative Japanese sashimi market.

"It's the most extravagant example of unsustainable fishing practices,'' claims Greenpeace's Quirk. "It takes about 10 kg of sardines to make one kg of tuna."

Quirk says Australians eat more canned tuna than any other fish, all of which is imported. "The majority - about 60 per cent - of that tuna comes from the western Central Pacific where you have between 21 and 46 per cent pirate fishing. Even the legal operations have fished big-eye tuna down to 17 per cent of their original biomass.''

Greenpeace Australia Pacific has produced a guide to buying canned tuna that ranks different brands. "Some brands couldn't even tell us where their tuna came from,'' says Quirk. The guide currently has the Fish4Ever brand leading the way, with Aldi and IGA making positive moves to change their buying practices and label their own-brand tuna more clearly.

Keith Symington, bycatch strategy leader for the WWF Coral Triangle Program, says major canning operations tend to group together tuna catches before exporting it across the globe, making it hard to know just what's in each can.

He says: "It's difficult for a consumer to know if a fishery is doing something that's positive and more responsible."

Old King Neptune had a farm

The United Nations Food and Agriculture Organisation (FAO) defines aquaculture as "the farming of aquatic organisms including fish, molluscs, crustaceans and aquatic plants with some sort of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc". According to the FAO, fish farming provides about half of all the fish eaten on the planet.

Jessica Meeuwig, director of the Centre for Marine Futures at the University of Western Australia, is critical of marine aquaculture.

"Sea cage aquaculture is a concern - they are the marine equivalent of battery chicken farms," she says. But considering the world has ever more people to feed, Meeuwig says we'll have to get more of our fish from aquaculture.

"When we ask if aquaculture is sustainable, the question to ask is what is being farmed," says Meeuwig. Because fish farming tends to focus on larger, more valuable species, this increases pressure on wild stocks of smaller fish that are used as feed.

Preferred aquaculture methods, according to Meeuwig, are land-based farms where it is easier to stop chemicals, disease and waste from affecting the environment, although these tend to be more expensive to run. Farmed seafood, including mussels, oysters and abalone, are in general better choices, she adds.

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