Coho salmon engineered for transgenic expression of growth hormone
were more aggressive predators in simulated natural environments.
Coho salmon (Oncorhynchus kisutch).
Type I salmon growth hormone gene.
"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,
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.
"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).
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.
Fisheries and Oceans Canada, West Vancouver; Goteborg University, Sweden.
Canadian Regulatory System for Biotechnology, Swedish Research
Not on the market as of 2009.
Copyright 2009 The Nature