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Content archived on 2024-05-29

Ecological risk-assessment of transgenic salmon

Final Activity Report Summary - ERATS (Ecological risk-assessment of transgenic salmon)

At present, studies of transgenic fish cannot be performed in nature due to the difficulty in extirpating the transgene should negative consequences arise. Therefore, assessments of transgenic fish in contained facilities need to be conducted under as wide a range of conditions as possible. The ecological consequences of biological differences between transgenic and wild-type fish determined in the laboratory may be uncertain due to different responses to varying environmental conditions as well as because of our limited ability to extrapolate simple phenotypes from complex ecological interactions like the ones occurring in nature. As such, efficient physical and biological containment strategies remain critical to ensure the safe application of transgenic fish technology in the future.

Our results showed how rearing conditions prior to escape to nature could greatly influence subsequent ecological consequences, how these effects might depend on seasonal conditions, food availability, predator presence, oxygen conditions, temperature and water connectivity, to mention a few factors found to influence the relative performance of wild-type and transgenic salmon. For example, increasing temperature elevated growth in transgenic fish more than in wild-type so that experiments carried out at a given temperature may provide a different outcome if carried out at another temperature. During development at the eggs stage, however, transgenic fish appeared to cope with oxygen deficiencies less well, even though this was only examined at a single temperature and we observed that relative developmental rate between transgenic and wild-type fish changed with temperature.

Due to the multitude of factors influencing the development of transgenic fish, uncertainty was likely to increase with fish age, and we only recently started looking at reproductive success of adults, which, because of their old age, were highly influenced by prior rearing conditions. Therefore, most other experiments utilised newly emerged fry which had minimal environmental experience. At the same time, other traits, such as migratory timing and starvation tolerance, were usually considered to be influenced by growth rate and body size was not found to be greatly altered by growth hormone transgenesis. We also found how responses by other ecosystem members might affect the impact of transgenic specimens.

To get a better feel on how fast-growing transgenic fish might function in nature, we complemented the contained laboratory studies of transgenic fish with work on non-transgenic wild-type salmonids under fully natural conditions. We used natural variations in individual growth history and manipulations of population conditions to assess how changes in growth potential influenced subsequent performance in nature. These data were preliminary but suggested that there was scope for individuals with greater growth potential, such as growth-enhanced fish, to survive under fully natural conditions, even though the large size was not invariably advantageous. Once again, outcomes of experimental treatments proved difficult to predict with several factors affecting performance of the fish in the stream. In addition, it would be desirable to use actual transgenic fish, necessarily sterile, to remove the uncertainty of normal rapid growth, i.e. large wild fish, and artificially induced growth, like for example large individuals because of the transgene. This had yet to be approved for actual field trials.

Overall, this project clearly showed that predicting the ecological risk of growth enhanced transgenic salmon was a very complicated task and would require further studies and novel experimental approaches before a scientific recommendation could be made. We would recommend science policy regulators and decision makers to carefully consider our data when deciding whether to allow commercial application of transgenic species in aquaculture. At this stage, the use of transgenic fish for commercial applications would need to consider strict physical and biological containment strategies to prevent the transgene from entering natural genomes.