Diet, Glycogen Reserves and Resistance to Fatigue in Hatchery Rainbow Trout. Part II.

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Abstract
Violent or prolonged exercise increased blood lactate content of hatchery–reared rainbow trout, confirming earlier findings. In stream tests, two groups of hatchery–raised rainbow trout were planted in a mountain stream containing a resident population of cutthroat trout. One group had been raised on a fortified pelleted ration, the other on the standard raw liver diet. In 5 weeks 7.1% of the pellet–fed fish were recovered dead or moribund, and 20% of the liver–fed fish. Adverse environmental conditions (high water) did not prolong the usual two–week acclimatization period for the pellet–fed trout, as shown by cessation of mortality at the end of that time. The liver–fed trout continued to die in appreciable numbers until three weeks had elapsed. After the 2–week acclimatization period the pellet–fed trout accommodated to high–water conditions as well as or better than the resident trout in respect to blood lactate level, whereas liver–fed trout maintained a higher than normal lactate level. Ten hatchery–raised trout, 2 from the pellet–fed group and 8 from the liver–fed group, were recovered from the stream in a moribund state. These had blood lactate levels four or more times as high as the non–moribund trout on the same date. An Appendix table gives a summary of the Gorge Creek trout plantings in 1952–57.

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