Fitness-related effects of growth investment in brown trout under field and hatchery conditions

The mortality of brown trout Salmo trutta over winter in a near-natural str eam was not significantly increased by growth hormone (GH) treatment, but l ipid reserves were lower in GN-treated fish. As GH-treated trout grew Faste r than controls. GH appears to promote growth at the expense of investment in maintenance. However, the growth promoting effect of GH was much more pr onounced in the hatchery than in the stream, suggesting that the pay-off as sociated with increased growth investment is higher under hatchery conditio ns with unrestricted food supply than in the wild, where food availability is limited. (C) 2000 The Fisheries Society of the British Isles.