Title: Salmonid behavior and water temperature
Author: Sauter, Sally T.; McMillan, John; Dunham, Jason B.
Source: Seattle, WA: United States, Environmental Protection Agency, Region 10 Office of Water. Final Report to the Policy workgroup of the EPA Region 10 Water Temperature Criteria Guidance Project. EPA 910-D-01-001. 36 p
Description: Animals react not only to immediate changes in their environment but also to cues that signal long-term changes to which they must adapt to survive. A proximate factor stimulates an animals immediate behavioral response, whereas what is known as an ultimate factor causes an animal to adjust its behavior to evolving conditions, thereby increasing its fitness and chances of long-term survival. The Salmonid family are cold-blooded organisms that can respond to an uncomfortable water temperature by moving from one spot to another to maintain thermal comfort. If the reason they move is because of a discrepancy between the temperature of the surrounding water and a set point in their brains that registers thermal comfort, their response is known as behavioral thermoregulation. In this paper we discuss two kinds of behavioral thermoregulation: reactive and predictive. The reactive kind is in response to discomfort that is temporary and short term, and so it is a response to a proximate factor, as described above. Predictive thermoregulation occurs when the temperature of the water in which salmonids choose to swim reflects their adaptation over time to a changing environment and thus is a response to an ultimate factor, as described above. Sometimes water temperature stimulates behavior that has nothing to do with thermal comfort. What is known as orientation behavior occurs when water temperature cues fish to locate prey or, say, reduce competition with other fish.
In natural environments, the proximate and ultimate ecological factors driving thermal behavior are frequently complex and not easily separated. Understanding the underlying mechanisms and adaptive value of a behavioral response nonetheless is helpful when considering the influence of anthropogenic or human-caused changes in water temperature on salmonid populations.
Keywords: animal behavior, water temperature, water quality, aquatic environments, streams, thermoregulation, salmonids
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Sauter, Sally T.; McMillan, John; Dunham, Jason B. 2001. Salmonid behavior and water temperature. Seattle, WA: United States, Environmental Protection Agency, Region 10 Office of Water. Final Report to the Policy workgroup of the EPA Region 10 Water Temperature Criteria Guidance Project. EPA 910-D-01-001. 36 p.