[Thanks to Professor Muir for this clear and highly relevant message about the release of genetically modified (GM) fish. He summarises some of the main results from his paper, published in PNAS in November last year. This work was also featured in a recent article in the scientific journal Nature on 6 July this year (volume 406, pages 10-12).......Moderator]
In the fish sector, biotechnology has mainly been directed toward transgenics. While I generally support biotechnology, I think there are some major concerns with transgenics that need to be addressed when working with a species that is an integral part of an ecosystem. For example, if one is working with pigs, cattle, sheep, goats, or poultry in countries where such animals are all domesticated and have no counterparts in the wild, escape of such transgenic animals presents little risk because of the great difficulty they would have in establishing themselves in the wild because there would be no wild animals to interbreed with. This is, of course, assuming the transgene does not impart some major fitness advantages to the transgenic animals that would overcome this disadvantage.
On the other hand, if feral animals exist in the wild for the transgenic species, then there are two major concerns. The first is that the feral animals are most likely an integral part of the ecosystem, disruption of that species can result in cascading effects on the entire ecosystem. Second, because feral animals exist, it is much easier for escaped animals to become established through interbreeding.
In all aquatic species, there are feral counterparts, so transgenic fish need special attention. The question then comes down to: will escape of transgenic fish cause disruption of the ecosystem. In a recent paper (Muir, W.M. and R.D. Howard. 1999. Possible ecological risks of transgenic organism release when transgenes affect mating success: sexual selection and the Trojan gene hypothesis. Proceedings of National Academy of Science 24:13853-13856) we show that if a transgene increases mating success while at the same time has a viability disadvantage, it is possible for an escaped transgenic fish to take the entire natural local population to extinction. Further, we show with our model species (medaka), and in the literature, that larger fish (including salmon) have a significant mating advantage. Secondly, we show in our transgenic line of medaka for growth hormone, that a reduction in viability occurs. Thus the main criteria for such a result to occur are present in fish transgenic for growth hormone.
However, it is not enough to look simply at mating success and viability to determine if transgenic fish are a risk to the ecosystem. We conclude that there are six net fitness parameters that need to be measured in order to assess risk, these are: survival to sexual maturity, age at sexual maturity, fecundity, fertility, mating success, and longevity. All impacts of a transgene will manifest themselves in one or more of these components. We then have a mathematical model that combines these net fitness parameters to assess if there is the potential for an escaped transgenic fish to either increase in frequency or go to extinction.
Of course, we can never duplicate the exact conditions of nature in a secure laboratory environment, the only thing we can conclude is if such fish show the potential for disruption. However, if a fish does not show indications of risk in a relatively benign laboratory setting, we are comfortable they will not be a risk in nature's more harsh conditions. Thus, we can never really say, even with measuring all six net fitness parameters, if a transgenic fish will really cause ecological harm, we can only tell those cases where we are fairly confident that it will not.
Thus we have the means to assess "lack of" ecological risk in a secure laboratory setting. In some cases (perhaps even most) transgenic fish may show no indication that they would be an environmental risk. In such cases, the issues would have been addressed and commercialization should proceed. However, to date, none of these net fitness parameters have been measured on any transgenic fish of commercial interest. Until industry presents us with the data, use of this technology should be restricted to secure facilities and/or sterile fish. Even then, the problem is to determine if all transgenic fish in commercial production would be sterile. I have not seen convincing evidence that the failure rate of sterilization is less than 1:1,000,000, i.e. the escape rate of salmon from net pens.
Professor of Genetics
Department of Animal Sciences
W. Lafayette, IN 47907-1151
E-mail [email protected]
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