Similarly, farmed Australian prawns are often priced more cheaply than the more labour-intensive wild prawns. The two main prawn species farmed in Australia, according to the CSIRO, are the black tiger and banana varieties. Manettas Seafood Market, for example, advertised tiger prawns for $39.90 to $45.50 per kilo, while ocean king prawns were between $45.50 to $49 per kilo (although prices are subject to regional fluctuations).

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Farmed prawns from Australia have received the AMCS’s tick of approval, as have Spencer Gulf prawns, described as affordable and sustainable.

Wild prawns caught in NSW and Queensland have been linked to overfishing and problems with bycatch, while scallops have been overfished.

However, Seafood Industry of Australia chief executive Veronica Papacosta challenges AMCS’s assertion that wild-caught prawns had unacceptable levels of bycatch.

“There is always work going on to reduce interaction with other species, and it’s one of the best-performing issues in the country in terms of bycatch,” she said.

“We stand very strongly by the fact that if you’re buying Australian, [you’re buying from] one of the highest regulated and best-performing fisheries management systems in the world ... we do an excellent job here and we should be proud of that.”

Wild barramundi in the Northern Territory and Queensland is still often sourced from gillnets, which shark advocates and scientists describe as indiscriminate killers that also net dugongs and turtles.

GoodFish program manager Stephanie McGee, who helped compile the report for the AMCS, said consumers should instead look for farmed barramundi.

“Barramundi farms are found all over the country, usually in land-based tanks and ponds that are well managed to have little impact on the local environment.”

Meanwhile, Tasmanian farmed salmon was among the worst on the “naughty list”.

“Salmon farms there continue to cause significant environmental harm, with farming waste causing algal blooms, while efforts to deter seals, such as underwater explosive charges and lead-filled bean bag projectiles, can have lethal impacts,” McGee said.

“Critically, farms in Macquarie Harbour have drastically depleted oxygen levels, pushing the endangered Maugean skate to the brink of extinction.”

Whatever their costs, Australian-farmed mussels and oysters are among the most sustainable seafood choices. Both mussels and prawns filter water and contribute to removing nitrogen from waterways.

Managing director of South Coast Mariculture Sam Gordon has marine leases in Jervis Bay and Eden in NSW. He started harvesting mussels several years ago in deep waters off Jervis Bay.

Mussel and oyster farming is part of the emerging field of restorative aquaculture, which Gordan says promotes a “net benefit” approach to farming.

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“The Nature Conservancy has done some work on restorative aquaculture that shows, in the case of mussel farming and oyster farming, that it actually increases the biodiversity of species on and around the leases where they’ve been growing and also increases the total population of marine life around the leases – and removes nitrogen from the water,” Gordon said.

“Our mussel farms and oyster farms are like a big floating reef out in the middle of the ocean.”

He says along with mussels, seaweeds grow on the lines. “There’s sponges and seahorses out there, and then fish coming to feed on all those different animals that are on the ropes … it’s one of those few foods that actually have a net benefit to the environment.”

Other sustainable shellfish options include tropical, eastern and western rock lobsters, which are plentiful and caught by hand or baited traps, causing minimal habitat damage (southern rock lobsters are of more concern to researchers).

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