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Unintended Effects of Genetic Manipulation
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Coho salmon engineered for transgenic expression of growth hormone were more aggressive predators in simulated natural environments.

Manipulated Organism: Coho salmon (Oncorhynchus kisutch).

Inserted Transgenes: Type I salmon growth hormone gene.

Background: "The possibility to enhance the growth of fish by transgenesis of growth factor genes may allow for the production of marketable products in shorter periods of time, and with lower production costs. Not surprisingly, companies within the aquaculture industry are seeking permission to farm growth hormone (GH)-transgenic salmon. However, millions of farmed salmon escape every year from aquaculture seapens, indicating that transgenic salmon grown in conventional facilities would probably escape into the wild.... It is therefore important to evaluate the potential impacts that GH-transgenic fish may have on the ecosystem before any farming of these strains is allowed" (Sundstrom et al., 2004, p. S350).

Goal of This Study: Compare the survival and predatory behavior of transgenic salmon with their non-GM half-siblings in simulated natural environments.

Results of This Study:
  • In one experiment, salmon just completing their larval development (called fry) were forced to forage for food in the same tank as a predator fish. These flow-through tanks simulated natural streams, with coarse gravel in which the salmon fry could hide from the predator. When the fry were given ample live food, the mortality rate of the transgenic fish was 45% vs. 15% for the non-GM fish. When the fry were kept in tanks with low food abundance, the difference in mortality was even greater: 67% of the transgenic fish died compared with 12% of the non-GM fish. Since fish mortality was not correlated with body length, the authors concluded that the higher mortality rate for the transgenic fish was the result of more aggressive foraging behavior that increased their exposure to the predator fish.

  • In a second experiment, the predatory behavior of older salmon was quantified. When reared in the simulated natural environment, the transgenic fish grew to be twice as heavy as the non-GM fish by their first birthday. These one-year-old GM fish ate 74% of the live feed in their enviroment vs. 62% for the non-GM fish.

  • When reared in the hatchery and given unrestricted access to commercial feed, the transgenic salmon grew to be 23 times the weight and 2.7 times the length of the non-GM fish by their first birthday. When subsequently placed in the simulated natural environment, these GM fish ate 78% of the live feed versus 58% for the non-GM fish.

Additional Comments: "Because transgenic organisms show evidence of phenotypic plasticity that in turn influences their predation ability, it is clear that forecasting ecological consequences in nature of transgenic organisms reared and assessed in simple laboratory facilities could be inaccurate" (Sundstrom et al. 2007, p. 3891).

Source: Sundstrom, L. F., M. Lohmus, J. I. Johnsson and R. H. Devlin (2004). "Growth Hormone Transgenic Salmon Pay for Growth Potential with Increased Predation Mortality," Proceedings of the Royal Society of London B, vol. 271, pp. S350-2.

Sundstrom, L. F., M. Lohmus, W. E. Tymchuk and R. H. Devlin (2007). "Gene-Environment Interactions Influence Ecological Consequences of Transgenic Animals," Proceedings of the National Academy of Sciences vol. 104, pp. 3889-94.

Author Affiliations: Fisheries and Oceans Canada, West Vancouver; Goteborg University, Sweden.

Funding: Canadian Regulatory System for Biotechnology, Swedish Research Council.

Product Status: Not on the market as of 2009.

Copyright 2009 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/coho_salmon_003.php

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