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Testing the Mettle of Genetically Modified Fish

Photo by Chris J. Benson.

Bigger, better, faster, stronger? Maybe, maybe not.

In the first-ever investigation of its kind, Minnesota Sea Grant-funded researchers examined the long-term consequences of actually letting genetically modified fish mingle with wild-type populations of the same species. Prior to this study, investigators worked with hypothetical populations and computer models to study what might happen to wild populations if transgenic animals escaped captivity.

Kelly Pennington, Minnesota Sea Grant's 2010 Knauss Fellow, and Anne Kapuscinski, Sherman Fairchild Distinguished Professor of Sustainability Science at Dartmouth College (formerly with the University of Minnesota), led the study and co-authored a resulting article in Environmental Biosafety Research. Using the laboratory-friendly Japanese medaka, Pennington, Kapuscinski, and their colleagues found that after 19 months, the equivalent to nine generations, only a single fish in one of six replicated environments still carried a growth-enhancing gene construct. The starting populations were made up of 477 wild-type and 40 transgenic medaka each. By the end of the 19 months, about 50 fish remained in each population.

During an earlier six-month experiment, 20 transgenic medaka were released amongst 353 of the wild-type. Of the six replicates, three retained transgenic members.

"U.S. regulators are currently debating whether to approve the farming of transgenic salmon modified to grow to market size faster," said Pennington. "Other fish species with various engineered traits are being developed around the world. Our work in the laboratory represents a first attempt to document the potential impacts transgenic fish might have on wild populations after multiple generations."

Pennington and her colleagues also found that although males of one strain of the genetically engineered medaka were more fertile than wild-type males, the modified medaka were less apt to secure mating opportunities. Other studies suggest the beefier transgenic males could have a mating advantage over their peers.

"Factors like the genetic diversity of wild populations and natural environmental conditions are difficult to simulate in a laboratory," said Pennington. "We still have a lot to learn before risk assessments can confidently predict the population-level impact of escaped transgenic fish."

By Sharon Moen
October 2011

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