The Straits Times Forum Page, 19 January 2001
By Hew Choy Leong, Professor and Head Department of Biological Sciences
National University of Singapore
GM fish sterilised to protect ecology
THERE have been several reports recently on the possible impact of transgenic (genetically-modified) fish on the native fish populations, if they are released accidentally.
It was postulated that these bigger fish enjoy a mating advantage and would wipe out the wild type.
As a fish biologist working in this field, I wish to point out that this argument does not hold.
It is true that many scientists, including our own research team, have been successful in producing faster-growing fish.
In the early growth phase, these transgenic fish are bigger and can reach a marketable size much earlier.
Besides these faster-growing fish, many scientists around the world are also generating fish which are more resistant to diseases or more adaptable to the cold or a freezing environment.
This technology leads to higher yields and lower production costs.
The United States Department of Agriculture (USDA) has instituted a set of guidelines for scientists and the industry to handle this new variety of fish.
The experiments carried out at Auburn University in Alabama, in a closed system, were required by the USDA to observe the performance of the transgenic fish in relation to the wild population.
They showed that these 'super fish' were actually no more adaptive than their wild counterparts, and could be even less adaptive.
The claim that genetically-modified animals could interbreed with their natural cousins - in ways that would destroy the species entirely - originates from a model described by Dr W. Muir of Purdue University in the US.
This 'Trojan gene' effect lacks experimental data or evidence - it is strictly hypothetical.
The assumption that the bigger transgenic fish enjoy a mating advantage is certainly not true for all species.
The salmon, in particular, is one such example.
Many of the wild males are sexually mature in two years instead of three in the females. These smaller 'precocious' males are usually the successful ones that fertilise the females.
To commercialise the transgenic fish, scientists agree that they must be made sterile - these fish will be unable to produce any offspring and will not have any impact on the wild-fish population.
This serves to maintain the ecological balance and protect the environment in the event of any accidental escape of these fish.
There are several methods for making fish sterile.
One general practice is to manipulate the number of chromosomes in these organisms.
For example, by heat or pressure treatments, fertilised salmon eggs can be made to contain three copies of chromosomes and, will, therefore, be sterile.
These methods are already norms in the marine-food industry and are also being used to produce new varieties of oysters and other similar animals.
Copyright @ 2001 Singapore Press Holdings. All rights reserved.
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