Fish is a Health Halo food. It's high protein, and either low fat or loaded with healthy omega-3 fats. But there's a growing problem as ocean fish populations are depleted: fish fakery. According to a report from Oceana, 1/3 of fish samples collected around the U. S. were labeled incorrectly. No surprise: cheaper fish were substituted for more expensive varieties. Oceana is on the lookout for seafood fraud, testing fish in grocery stores and restaurants. In Denver, the problem was worse with restaurant fish, where you pay a premium for supposedly expensive and high quality fish. While this isn't necessarily a health problem, it is an economic problem for the unsuspecting restaurant customer.
Why do we have this problem? Again, global over-fishing is severely impacting fish supplies. Take North Atlantic cod, once plentiful. Canada placed a moratorium on cod fishing off the east coast 20 years ago. It's still in place. The catch limit for New England cod fishing is cut almost 80%. That would make real North Atlantic cod very expensive, if you can even find it to buy. The stage is set for some unscrupulous fish vendor to pass off some other white fleshed fish as "cod", and charge a premium.
It's not that hard to do. White fleshed fish varieties don't have particularly strong identifying flavors or textures. They're much the same. Testing, such as that done by Oceana, is done by expensive DNA technology. It's not at all practical or affordable for restaurants or even fish wholesale markets.
Meanwhile, the Dietary Guidelines encourage everyone to eat at least 8 oz of fish per week. The U.S. government is apparently unaware of the global pressures of expanding human population and deteriorating fish stocks. According to a United Nations report, the recent horse meat scandal in Europe is a another sign that deliberate food adulteration will become more common in the future, as production of animal source foods, from beef to fish becomes increasingly expensive. Producers will be tempted to cut costs by illegally substituting cheaper look-alikes.
So what do you do if you love fish? Buy fish labeled "sustainable"? A recent series on NPR calls the sustainable seafood accreditation process into question, so buyer beware. If you want to avoid fish fraud, you could just stick to easily identifiable fish, like canned sardines, shrimp, whole trout, whole lobster or salmon, which has a reliable pink color and distinctive flavor. Keep in mind, salmon, shrimp and other popular species are increasingly farmed, and fish farming comes with it's own set of environmental controversies.