The FDA is currently reviewing genetically modified salmon for consumers. The engineered fish have an added growth gene that doubles its growth rate.
AquaBounty Technologies developed the salmon over a decade ago and have been trying to get approval ever since. This year, they submitted key data that show the salmon are safe for consumption and the environment. Some consumer groups and experts are voicing concerns over the claims of safety. For example, the sample size might be too small and there isn't enough information on the environmental impact. Even if AquaBounty's data withstand scrutiny, there are some legitimate questions about the benefits and risks of having genetically engineered salmon.
In terms of nutrition, modified salmon is reported to be similar to the farmed variety, but that's not saying much. Farmed salmon have more PCB and heavy metal contaminants and lower levels of Omega-3 fats than wild salmon. Thus, modified salmon can't compare to wild salmon and isn't better for you than regular farmed salmon. Its only advantage seems to be a faster growth rate, but whether that translates to savings for consumers is unknown.
As for environmental impacts, what happens if unnatural salmon get released into nature? How will that affect wild habitats? What if the engineered salmon mate with native fish? Modified salmon are supposed to be all sterile females, but mistakes can happen. It just takes one oversight to create an environmental disaster.
Many members of the House of Representatives and Senate have asked the FDA to halt the review process and obtain more transparent data analysis. It would be wise for the FDA to take their advice, especially as the current review process may be inadequate for dealing with the unprecedented issues that come with genetically engineered animals for food.