Oceana, a group dedicated to preserving the ocean ecosystem, is testing fish nationwide to find out whether seafood fraud is as widespread as some people think it is. It is now possible to determine exactly what species is being served at the local fish shack, thanks to recent advances in genetic sequencing. Oceana has thus far found seafood mislabeling everywhere it has done testing, including Boston, Los Angeles, Miami and Monterey. The DNA-testing campaign, in which dozens of volunteers are provided testing kits with instructions and monitoring sheets, created an uproar when the early results came out. In South Florida ... results showed that 31 percent of the fish tested at restaurants and markets was mislabeled. In Los Angeles, 55 percent, and in Boston, 48 percent of the fish sold was not what it was touted to be. In Los Angeles ... eight out of nine sushi samples labeled as white tuna," or shiro maguro, were actually escolar, which [has been called] the "ex-lax fish" for its purgative effect on the digestive system. Escolar is not among the 14 species that can legally be labeled as tuna. Oceana found that 87 percent of the sushi venues tested misrepresented the fish being served. The results follow several Consumer Reports studies that had similar results, including a 2006 report that found that 56 percent of the salmon marketed in the United States as wild was actually farmed. Thirty-one percent of grocery stores misidentified fish. In many cases, there is no way for the consumer to know whether the fish is what the restaurant, fish market or grocery store claims it is.