SOME genetically modified fish are like ferocious tigers in a bare tank but appear to be pussy cats under more natural conditions. This finding suggests it will not be easy for biologists to predict the ecological consequences of escaped transgenic animals.
Salmon genetically engineered to overproduce growth hormone can put on up to 25 times the weight of wild salmon and could provide aquaculturists with a faster way to raise fish to market size. However, lab tests showed that these transgenic fish are more aggressive predators than wild salmon, raising concerns that they could harm wild ecosystems if they escape.
Fredrik Sundstr枚m and his colleagues at Fisheries and Oceans Canada鈥檚 Center for Aquaculture and Environmental Research in Vancouver tested whether the GM fish would have the same superiority in more natural conditions. When they raised the fish alongside unmodified salmon in stream tanks complete with gravel, large rocks, logs and natural live prey, they found that the GM fish still grew a little faster and ate a little more than the others, but their advantage was much smaller than when they lived in a simple metal tank and ate pelleted food (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0608767104).
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That does not mean escaped GM fish would not cause ecological damage, says Sundstr枚m 鈥� only that biologists will need to work harder to answer the question. 鈥淵ou can鈥檛 use fish reared in the lab to predict what will happen in nature,鈥� he says.
