Upper thermal limits for feeding and growth of 0+ Arctic charr


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When Arctic charr Salvelinus alpinus from two diVerent stocks were fed live Neomysis integer, the upper thermal limits for feeding and growth were established in the range 21·5–21·8° C. These critical temperatures might have been underestimates, because fish tend to show increased sensitivity to handling at high experimental temperatures. In the second experiment, the proportion of feeding undisturbed charr from four stocks decreased initially as temperature was raised in steps from 18 to 22° C. At the lower temperatures, 18 and 20) C, almost all fish resumed feeding, but the recovery time was longer and more fish ceased to feed at 20) C than at 18° C. When the temperature was increased to 21° C, 50% of the fish ceased feeding permanently, and all fish ceased feeding within 2 days at 22° C. It is concluded that 0+ charr cease to feed and grow at c.21·5) C and that the critical temperatures for feeding and growth coincide.