Growth-enhanced transgenic salmon can be inferior swimmers

We examined the consequence of remarkably fast growth rates in transgenic fish, using swimming performance as a physiological fitness variable. Substantially faster growth rates were achieved by the insertion of an ''all-salmon'' growth hormone gene construct in transgenic coho salmon (Oncorhynchus kisutch). On an absolute speed basis, transgenic fish swam no faster at their critical swimming speed than smaller non-transgenic controls, and much slower than older non-transgenic controls of the same size. Thus, we find a marked trade-off between growth rate and swimming performance, and these results suggest that transgenic fish may be an excellent model to evaluate existing ideas regarding physiological design.