Behavioural compensation for long-term thermal change

Summary

We found the main stream so low that the teeter-snipe pattered about in what last year were trout riffles, and so warm that we could duck in its deepest pool without a shout … There were no trout … But … up near the headwaters we had once seen a fork … fed by cold springs that gurgled out under its close-hemmed walls of alder. What would a self-respecting trout do in such weather? Just what we did: go up. I climbed down the dewy bank and stepped into the Alder Fork. A trout was rising just upstream …

(Aldo Leopold, 1949, p. 40)

Introduction and overview

A 1 °C alteration in a heterothermal aquatic environment produces behavioural adjustments in many fishes; a 4 °C shift leads to major changes in fish distribution. This is expected to occur for a majority of species and is likely to be important both ecologically and physiologically. Temperature changes of this magnitude are predicted during the next century, owing to the greenhouse effects of anthropogenically generated gases. These climate warming scenarios differ by region and latitude and would be influenced by other human activities such as logging, use of dams, power generation, and urbanization (Kemp, 1994). In this chapter thermoregulatory behaviour is discussed as a shortterm, local adjustment to the posited increases in global temperature.