Transgenic fish pose extinction threat

WASHINGTON, Feb. 17 (UPI) -- New evidence shows commercial fish that have been genetically modified to be larger could drive wild fish populations to extinction, if they escaped into the environment, scientists told United Press International Tuesday.

Consumer groups said the finding promises to reopen the debate about how these transgenic animals should be regulated.

Fish that are genetically modified to be larger or reach adult size more rapidly are sought after by commercial fish producers, and at least one company is developing such a species.

None of these growth-enhanced fish has yet been approved by the Food and Drug Administration for human consumption.

However, the first transgenic fish commercially available in the United States - an aquarium fish, known as the Glofish - went on the market in January.

The Glofish may not pose the same extinction threat as the growth-enhanced fish being bred for food because its genetic alterations do not involve its size. Instead, it has been genetically modified to fluoresce reddish-pink and is sold at pet food stores as a novelty fish for home aquariums.

Watchdog groups are concerned about the impact transgenic fish could have on both humans and the environment. The new study by Purdue University researchers, which will appear this week in the online edition of the Proceedings of the National Academy of Sciences journal, suggests those concerns might be warranted, at least for fish genetically altered to be larger.

"This study shows for the first time that genetically modified fish can have better mating success than wild-types," Richard Howard, a Purdue biologist and leading study author, told UPI.

Howard's team inserted a salmon gene for growth hormone into male medaka fish, resulting in animals that were 83 percent larger than their wild counterparts. Further research showed the larger transgenic fish out-competed the wild males for females and were responsible for 75 percent of all matings. The resultant offspring from the transgenic fish matings, however, had a reduced viability.

Putting this information into a mathematical model, Howard's group calculated that within 50 generations the entire fish population would become extinct.

The researchers called this phenomena the "Trojan gene effect" and said it could have an impact on other species as well. The change in the gene pool could alter behavior of the fish and this in turn could affect the ecological dynamics of other species they interact with, they noted.

Devising ways to prevent accidental releases of these fish must be examined more closely, Howard said.

"This is something that needs to be really at the forefront of things before we put transgenic fish into actual production," he added.

Greg Jaffe, director of the biotechnology project at the consumer group Center for Science in the Public Interest in Washington, agreed.

"This study shows transgenic animals could have serious detrimental environmental consequences," he said.

A panel of experts convened by the National Academy of Sciences concluded in a report, issued in August 2002, there was no way to predict what might happen if transgenic animals escaped into the environment and noted its concern about the possibility of reversing such a situation if it had disastrous consequences.

The species closest to market in the United States is a salmon that has been genetically modified to produce more growth hormone, which causes it to grow more rapidly than non-modified fish. The salmon producer, Aqua Bounty Farms of Waltham, Mass., could not be reached for comment Tuesday but a statement on the company's Web site addressed the "Trojan gene" concerns.

The company said its fish, known as AquAdvantage, unlike the medaka fish used in the study, are not larger than wild salmon, "invalidating the key proposition in the (Trojan gene) hypothesis."

Aqua Bounty's application for FDA approval of its transgenic fish is still being evaluated by the agency.

The Aqua Bounty statement also said studies of escaped farmed salmon, which generally are larger than wild types, have only 3 percent of the mating success the wild fish have, showing that in salmon at least larger size does not translate into a mating advantage.

As a further safeguard, the company said it would only market sterile, female fish in areas where escape into the wild is a concern.

Howard said sterilization is one possibility for keeping these fish in check, but "it has to be done very carefully because you have to be extremely sure that all of the fish are sterilized."

Commercial fish producers deal with such large volumes that a sterilization assurance of anything less than 100 percent is unacceptable, he said.

As an example, he noted a few years ago some 100,000 commercial fish escaped off the coast of Maine in a storm. If sterilization was even 99.9 percent effective that still means about 100 unsterilized fish would have been released into the environment.

If these fish had been genetically modified to reach a larger size, they could have out-competed the wild types for mating and rapidly replaced the entire population, perhaps even causing extinction, he added.

Aqua Bounty said on its Web site its sterilization procedure, known as triploidy, is 100 percent effective in females because it prevents the development of ovaries needed to produce eggs. The company acknowledged, however, there still are lingering uncertainties about the effectiveness of the technique in male salmon.

Jaffe said a recently released report from a panel convened by the National Research Council on the containment of genetically modified organisms specifically addressed Aqua Bounty's fish and said the company's sterilization method alone is not sufficient. The report said multiple layers of containment are needed.

The panel's concern stems from the fact triploidy sometimes can fail and that even if it is 100 percent effective, the sterile transgenic fish likely would interrupt wild fish breeding, which could have detrimental consequences, particularly considering wild salmon populations are in decline.

One method the panel recommended is growing fish in inland ponds but noted this entails higher operating costs, so the fish industry, which prefers the cheaper alternative of floating cages in coastal waters, might object to it.

The FDA requires transgenic animals be shown to be safe for the environment but how the agency will ensure this still is uncertain, Jaffe said.

"The biggest problem is a lack of transparency in the approval process," he said. "We don't know if the studies Aqua Bounty are doing are adequate to address the environmental impact ... because the process FDA is going through with Aqua Bounty is done behind closed doors."

In addition, the agency has given no indication "whether transgenic fish will be approved tomorrow, next week or three years from now," he said.

The FDA did not return calls requesting comment.

In December the agency decided not to regulate Glofish -- a breed of tropical zebra fish distributed by Yorktown Technologies Inc., in Austin, Texas, that has had a gene from sea coral added to its genome to make it glow reddish-pink.

The FDA said in a statement the fish posed no risk to the food supply because they generally are not consumed by people and "there is no evidence that these genetically engineered zebra danio fish pose any more threat to the environment than their unmodified counterparts, which have long been widely sold in the United States."

Howard said he plans to conduct experiments with the Glofish to determine if they do pose an environmental risk.

"Right now, the indications are that they would not because the gene put into the fish doesn't increase body size or affect things that would necessarily elevate the mating success of males," he said.

He noted, however, that data on other types of fish show slight differences in color or ornament of males "really can make a male much more attractive to females," so a glowing male could perhaps out-compete a non-glowing one.

Yorktown's Chief Executive Officer Alan Blake said the Glofish was unlikely to have any adverse environmental impact. Blake pointed out that since the Glofish stems from a tropical fish, the zebra fish, it would not survive in the colder U.S. waters, and according to a July, 2003, study done by the U.S. Geological Survey there are no native populations of these fish in the United States with which it could interact even if it did survive.

"Despite the fact that (non-glowing) zebra fish have been sold into the ornamental fish trade by the tens of millions over the last 50 years, this remains the case because tropical zebra fish are unable to establish populations in the non-tropical North American climate," Blake told UPI. "Accordingly, there are no wild populations of zebra fish in North America upon which a change in color might have an adverse effect."