Farmed Fish Genetically Modified: Why GE Fish, Anyway?

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Farmed Fish Genetically Modified: Why GE fish, Anyway? JoAnn Guest Jul 31,

2003 20:27 PDT

Farmed Fish: Genetic Modification With

Human Growth Hormone Could Be Fish's Downfall

 

 

 

Why Genetically Engineer a Fish, Anyway?

 

Well, thats a good question. The short answer is the most obvious-money.

The seafood industry is worth $50 billion annually, and many of the fish

sold in your local grocery or market were raised on commercial farms.

 

Farm-raised fish, such as salmon, trout, or catfish, genetically

engineered to grow bigger, faster could bolster the industry's bottom

line.

 

Scientists in Britain and the United States have already begun

experimenting with salmon modified to carry a gene that induces

production of human growth hormone, also known as hGH.

 

So, you might ask, why not go ahead and genetically engineer these

super-fish?

 

Aside from wading into potentially murky ethical waters by placing a

human gene in a fish, there may be unexpected ecological consequences.

 

William Muir and Richard Howard, a pair of biologists from Purdue

University, studied Japanese medaka fish implanted with the hGH gene,

and found that the engineered fish grow to sexual maturity more quickly

than natural medaka fish.

 

Large medaka males, similar to the males of other species of fish

including salmon, attract up to four times as many mates as their

smaller competitors. Thus, the genetically modified males would mate

with more females.

 

On top of that, the early-maturing modified females would produce a

greater number of eggs than the unmodified females. Soon, the vast

majority of the fish population, be it medaka or salmon or

what-have-you, would consist of the genetically modified version.

Everything sounds good, so far, right?

 

 

Enter the Trojan Gene

 

Problems arise with unintended side effects. Muir and Howard found that

over 30% of the fish born with the hGH gene did not survive to sexual

maturity.

 

This creates a situation in which the fish least likely to produce

viable offspring are most likely to find mates.

 

Once the fish with the engineered gene make up a certain portion of the

total population, fewer of the fish spawned each season will survive to

create a succeeding generation.

 

The population will shrink. " This resembles the Trojan horse, " Muir

said. " It gets into the population looking like something good and it

ends up destroying the population. "

 

 

Bioengineered Extinction

 

In fact, Muir and Howard have predicted that the inability of the

modified fish to successfully reproduce could lead to extinction of the

species. They ran a computer model to explore the effects if 60 modified

fish joined a population of 60,000 of their natural cousins. The species

became extinct in a matter of 40 generations.

 

The same results occurred even if only one modified fish joined the

population pool, though the final extinction in this case took many more

generations. Muir explained, " The sexual selection drives the gene into

the population and reduced viability drives the population to

extinction. "

 

http://www.centerforfoodsafety.org/facts & issues/gefish.html

 

 

Additional information:

 

Possible ecological risks of transgenic organism release when transgenes

affect mating success: Sexual selection and the Trojan gene hypothesis

William M. Muir*, and Richard D. Howard

* Department of Animal Sciences and Department of Biological Sciences,

Purdue University, West Lafayette, IN 47907

 

Genetically Engineered Fish: Swimming Against the Tide of Reason

 

JoAnn Guest

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