WASHINGTON — Tinker with the genetics of salmon and maybe you create a revolutionary new food source that could help the environment and feed the hungry.

Or maybe you're creating what some say is an untested "frankenfish" that could cause unknown allergic reactions and the eventual decimation of the wild salmon population.

The Food and Drug Administration hears both arguments today when it begins a two-day meeting on whether to approve the marketing of the genetically engineered fish, which would be the first such animal approved for human consumption. The agency has already said the salmon, which grows twice as fast as conventional salmon, is as safe to eat as the traditional variety.

Approval of the salmon would open the door for a variety of other genetically engineered animals, including an environmentally friendly pig that is being developed in Canada or cattle that are resistant to mad cow disease.

"For future applications out there the sky's the limit," said David Edwards of the Biotechnology Industry Association. "If you can imagine it, scientists can try to do it."

AquaBounty submitted its first application for FDA approval in 1995, but the agency decided not until two years ago to consider applications for genetically engineered animals — a move seen as a breakthrough by the biotechnology industry.

Genetic engineering already is widely used for crops, but the government until now has not considered allowing the consumption of modified animals. Although the potential benefits — and profits — are huge, many individuals have qualms about manipulating the genetic code of other living creatures.

Genetically engineered — or GE — animals are not clones, which the FDA has already said are safe to eat. Clones are copies of an animal. With GE animals, their DNA has been altered to produce a desirable characteristic.

In the case of the salmon, AquaBounty has added a growth hormone from a Chinook salmon that allows the fish to produce their growth hormone all year long. The engineers were able to keep the hormone active by using another gene from an eel-like fish called an ocean pout that acts like an on switch for the hormone, according to the company. Conventional salmon only produce the growth hormone some of the time.

In documents released ahead of the hearing, the FDA said there were no biologically relevant differences between the engineered salmon and conventional salmon, and there is a reasonable certainty of no harm from its consumption.

Critics have two main concerns: The safety of the food to humans and the salmon's effect on the environment.

Because the altered fish has never been eaten before, they say, it could include dangerous allergens, especially because seafood is highly allergenic. They also worry that the fish will escape and intermingle with the wild salmon population, which is already endangered. They would grow fast and consume more food to the detriment of the conventional wild salmon, the critics fear.

A wide range of environmental, food safety and consumer groups have argued that more public studies are needed and the current FDA process is inadequate because it allows the company to keep some proprietary information private. Modified foods are regulated under the same process used for animal drugs.

"It is outrageous to keep this vital information secret," said Wenonah Hauter, director of the advocacy group Food & Water Watch. "Consumers have a right to know what FDA is trying to allow into our food supply."