After two decades of deliberation, the USA's Food and Drug Administration has approved the first ever genetically engineered food animal, a fast-growing Atlantic Salmon called AquAdvantage salmon.

According the agency, which announced the approval Thursday, the modified salmon are safe to eat, equally nutritious as other salmon, and should pose no threat to the environment.

First created in 1989 and submitted to the agency for approval in 1995, the Atlantic salmon are modified to carry a growth hormone gene from Chinook salmon. That gene is further engineered to be under the control of a tiny bit of DNA, called a promoter, from the eel-like ocean pout fish. In general, DNA promoters are non-coding sequences that help control the expression level of a gene—how much protein product is synthesized from the gene. With the engineered promoter boosting hormone production, the modified salmon grow to market-size in about half the time of conventional Atlantic salmon.

In the long approval process, the FDA assessed the nutritional profiles and hormone levels, comparing the modified fish to unmodified farm-raised Atlantic salmon. The agency found no significant differences.

The agency also assessed potential environmental effects and the proposed containment method. In accordance with the FDA’s approval, the fish must be kept in inland tanks, specifically tanks at two facilities—one in Canada and the other in Panama. The Canadian facility will keep the breeding stock, and the Panama site will be used to raise the fish to market-size.

Both facilities have multiple, redundant physical barriers to keep the fish and eggs from escaping, the agency noted. Tanks have covers, nets, jump fences, covered drains, and closed septic systems. In addition, conditions of natural water systems surrounding the Panama site, particularly the warm temperatures, are expected to be lethal to the salmon. The Panama site will raise all-female, sterile fish.

Because the agency found no material differences from conventional salmon, the modified salmon are not required to be labeled as such.