In August, a report by the University of Hawaii at Mānoa criticized the labeling practices of the Marine Stewardship Council in regards to its MSC-certified Chilean sea bass. Now, the council is disputing the validity of the study and saying it is "highly confident about the integrity" of its certified foods.

The study by University of Hawaii at Mānoa published in PLos ONE is titled "Seafood Substitutions Obscure Patterns of Mercury Contamination in Patagonian Toothfish (Dissostichus eleginoides) or 'Chilean Sea Bass.'" It found that the use of fish "substitutions," or fish that is presented as the same species but comes from a different place of origin, are misleading and distort "the true abundance of fish in the sea, defrauds consumers and can also cause unwanted exposure to harmful pollutants" like mercury.

Peter Marko, lead author of the study and UH Mānoa biologist, and his co-authors, Holly A. Nance and Peter van den Hurk, took an especially close look at MSC-certified Chilean sea bass, which consumers are led to believe come from South Georgia's Southern Ocean waters, far from pollution.

"What's happening is that the species are being substituted," Marko said. "The ones that are substituted for MSC-certified Chilean sea bass tend to have very low mercury, whereas those substituted for uncertified fish tend to have very high mercury. These substitutions skew the pool of fish used for MSC comparison purposes, making certified and uncertified fish appear to be much more different than they actually are."

Dr. David Agnew, MSC standards director, defended the council's certification process.

"We take supply chain integrity extremely seriously and have high confidence in the traceability of MSC-labeled seafood," Dr. Agnew said in a statement to Latin Post. "Results from independent DNA testing of MSC-labeled products show that over 99 percent are correctly labeled."

According to the MSC blog, the council conducts DNA testing on its product samples "so that our auditing system is working and that the MSC ecolabel is correctly identifying certified sustainable seafood."

This is not the first time that the MSC and Marko have bumped heads. In 2011, the two disagreed over the MSC's alleged mislabeling of toothfish.

Because of their history, Dr. Agnew has his doubts regarding the validity of Marko and his team's most recent report.

"Having previously sought to investigate the findings of the Marko et al (2011), we have serious concerns about the scientific rigour of this research," Dr. Agnew's statement said. "Flaws in the research include low sample sizes and a lack of robust sampling. The authors have been unable to provide evidence that the fish tested were MSC-labeled."

In a statement, the MSC claimed that "the sample size for the new study has been further reduced, with the authors drawing some of the conclusions based on only a single fish."

In addition, the MSC said it is has conducted studies that "confirm [the] integrity of the supply chain."

"The results also contradict the findings of our own DNA testing which has shown that when seafood is sold with the MSC ecolabel, businesses and consumers can be assured that the seafood they are buying and consuming is the seafood they purchased," MSC said in a statement to Latin Post.

MSC defines itself as "the world's leading certification and ecolabelling program for sustainable seafood" and boasts that it "developed standards for sustainable fishing and seafood traceability. ... [that ensure] that MSC-labelled seafood comes from, and can be traced back to, a sustainable fishery," according to its official website.

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 Follow Scharon Harding on Twitter: @ScharHar.