Gains reported in growth hormone treatment of fish

March 19, 1991|By New York Times News Service

COLLEGE PARK -- The world may soon be able to use genetic engineering or special hormones to make fish grow to market size faster and to increase world food supplies, says a University of Maryland marine biologist who is working to make it happen.

Thomas Chen, a biologist and professor in the biological sciences department at the University of Maryland Baltimore County, said that he already has rainbow trout and oysters growing at least 20 percent faster than normal -- and sometimes as much as 50 percent faster -- depending on the method used.

Dr. Chen said his project was one of several in which researchers are concentrating on fish, rather than cattle, partly because fish could be a readily available, economical food source for much of the world, and partly to reduce the United States' dependence on fish imports.

The U.S. trade deficit for fish products was about $4 billion in 1989, he said.

"The idea to make fish grow faster has been around for a long time," said Dr. Chen, who has been experimenting at the Center for Marine Biotechnology at the New Community College of Baltimore.

"From a scientific standpoint," Dr. Chen said, "fish represent a good model system because there are several different species from simple to highly evolved. A pragmatic reason is the ongoing situation with population increases and awareness of nutrition. Fish show a great potential to feed people."

Dr. Chen and two collaborators at other universities are experimenting with two different processes.

The first approach relies on a growth hormone cloned from rainbow trout. Fish are dipped in water that has the hormone dissolved in it for 1 1/2 minutes once weekly for four weeks.

The second approach involves altering the genetic makeup of a fish by transferring a gene for growth into the fish, which is passed on to subsequent generations.

Unlike humans, fish continue to grow throughout their lives, but Dr. Chen said he and his eight graduate assistants are not interested in creating bigger fish. They simply want fish to reach market size faster, thus getting more fish to market in a shorter time and saving fish farmers money.

Dr. Chen has been working on fish growth since 1982, starting at McMaster College in Hamilton, Ontario. He came to Maryland in 1986, when he began his collaboration with Dennis Powers at Stanford University and Rex Dunham at Auburn University.

The project is underwritten by grants from the National Science Foundation, the federal government and state grants from the Department of Natural Resources and the Maryland University Sea Grant.

The effects of both experimental processes need further testing, Dr. Chen said. He also said that he and his colleagues must research methods for producing large quantities of the growth hormone economically before they can make it available

commercially. The timetable will depend on the project's finances, Dr. Chen said.

Dr. Chen said rainbow trout and oysters have responded to both methods, growing 20 to 50 percent faster with the dipping process and 20 percent to 40 percent faster with the gene transfers.

But he said the researchers need to determine which nutrients, and in what amounts, to feed to the fish so that they do not grow abnormally.

"A trout usually takes two years to get to market size, which is about a pound to a pound and a half," Dr. Chen said, adding that with the application of the hormones or using the gene-transfer technique, the fish should reach market size in a year and a few months.

Dr. Chen said he could not foresee any negative effects of the techniques on fish, humans or the environment.

"We have done experiments with higher doses of hormones, and they won't make the fish grow faster, so we only use a small dose," he said. And, he said, "because the hormone is a protein, the hormone will be degraded in the fish," unlike the growth hormone, estrogen, that was once used to increase growth in beef cattle but was found to leave residues.

With continued research, Dr. Chen said he hoped that the hormone would be available for government approval in two to four years and the gene transfer in five to eight years.

"The work we are doing is especially important for developing countries," said Yan Lin Tang, a graduate student in biotechnology from China, who has been working on the project for three years while attending the College Park campus. "After working on the gene, we can watch the process of evolution, and we can use this gene and this hormone to study from."

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