An international group tasked with giving fish a stamp of sustainable approval has been accused of failing in its duties. This could mean that your “sustainable” fish, isn’t guilt-free.

The London based Marine Stewardship Council (MSC) was established in 1997 to certify fisheries as sustainable and so label the fish products that use those fisheries. Currently, MSC certifies over 6.3 million tonnes of seafood per year, and has the support of major supermarket chains, such as Wal-Mart – who pledged to sell only MSC-certified fish by 2010. .

“Consumers think that when they buy MSC fish they are getting a guilt-free product,” says Jennifer Jacquet at the University of British Columbia Fisheries Centre, Canada. “But they aren’t.”

Jacquet and colleagues, claim that MSC is certifying unsustainable fisheries, and fisheries whose sustainability status is unknown.

In 2005 the US trawl fishery for Pollock (Theragra chalcogramma) was certified, and recertified in 2009, despite the spawning biomass of pollock falling by 64 percent since 2004, says Jacquet.

And earlier this year, MSC certified fisheries of Antarctic krill (Euphausia) notwithstanding a long term decline in krill populations, and links between krill depletion and declining sea ice.

But according to Mike DeCesare, a spokesperson for the MSC, the dropping pollock population is due to the variable environment that supports the fish, and it is being actively monitored by scientists. “The stock is rebuilding,” he says. “And continued improvements in Alaska pollock biomass is expected as favourable conditions prevail.”

Jacquet argues that it’s not just the fish being certified that is a problem. The process of certification is tainted with potential conflicts of interests, she says. To become certified a fishery must be assessed by paid accredited consultants, which may encourage certifiers to “leniently interpret” sustainability criteria to receive more work.

Jacquet also takes issue with MSC’s deficient sustainability criteria that do not ban destructive fishing practices, such as bottom trawling. Nor does the MSC promote small fisheries using low-impact fishing techniques – such as hook and line fishing, she says.

But DeCesare says the criteria for sustainable fishery are based on “well-defined scientific principles” which were initially set by 300 scientists, conservation groups and industry groups. It is “extremely robust and credible,” he says.