Genetics helps reel in bigger fish.

Genetics helps reel in bigger fish

Scientists in maryland and Alabama are using a string of DNA to fish for advances in genetic engineering. So far the catch has been good: A growth-hormone gene transferred from rainbow trout into carp has produced bigger, faster-growing fish.

The scientists injected the growth-hormone gene into thousands of carp eggs, out of which grew 400 fish. Preliminary results show that 20 of the fish have incoporated the gene into their DNA, and most of those are making trout growth hormone and growing significantly faster than normal carp. This is one of the first successful attempts at genetic alteration of fish in the United States, says Thomas Chen of the University of Maryland's Center of Marine Biotechnology in Baltimore, who is conducting the research along with scientists from John Hopkins University in Baltimore and Auburn (Ala.) University. The new work adds fish to a genetically engineered menagerie that already includes such animals as pigs, fruit flies and mice.

The experiments may help reveal how genes are regulated, says Hopkins researcher Dennis Powers. Although most of the fish carrying the trout gene are growing faster, a few are growing more slowly than normal, and the researchers would like to know why. The difference may relate to where a carp incorporates the gene into its DNA, says Powers. The team also would like to know if the carp pass on the inserted gene to the next generation, he says.

The research could prove a boon to the aquaculture industry. Chen says, because altered fish may keep eating and growing during the winter months, when most normal fish do little of either. If this turns out to be the case, genetic alteration might allow fish farmers to shorten the time it takes to produce full-grown fish. The genetically altered fish might not survive well in the wild, outside of aquaculture ponds. Powers says. "The growth-hormone gene might make the fish want to keep eating and growing in winter," he says, "but there's not that much food in ponds at that time of year, so they might starve to death."