Crawshaw, Larry, Alec Maule, and Sally Sauter. “ Behavioral Thermoregulation by Juvenile Spring and Fall Chinook Salmon, Oncorhynchus Tshawytscha, During Smoltification.” Environmental Biology of Fishes 61 ( 2001): 295–304. (reviewed by May Dargan)
Summary:
This article examines both fall and spring chinook salmon and how they react to changes in water temperature. The authors believe that the change in temperature in the Columbia River and its tributaries, as a result of hydropower regulation, may be affecting young chinook salmon and that they may not be protected by “ temperature adaptations and responses to thermal stress.”
In order to test their hypothesis, the authors collected 270 spring chinook salmon and 250 fall chinook salmon close to their smoltification cycles. The differences between these two races of chinook salmon are their smoltification time and their spawning grounds. Spring chinook salmon spawn in tributaries and emigrate in their second year during the spring. Fall chinook salmon, on the other hand, spawn in the main part of the river and emigrate in their first year at the end of the summer. To test the two races of salmon, scientists held them in different tanks, slowly raising the temperature over time and recorded the fishes' preferences.
What the authors found was that the fall chinook salmon preferred a temperature change during smoltification, where as the spring chinook salmon did not. The conclusion was that “water temperature would serve as a strong directional cue for fall chinook salmon as fish enter the estuary during the summer months when freshwater temperatures are warmer than ocean temperatures and river flows are lowest.” Thus, they chose an environment with a lower temperature because it replicated their journey to marine waters. Spring chinook salmon did not prefer a temperature change because they “enter the estuary early in the year, during the spring runoff period when the water temperature of the Columbia River and seawater are both near 13 degrees C.”
Critique:
This article was very straight-forward and easy to follow. Even the methods and results, which are often difficult to read, were understandable. However, it seems as though this experiment was done for the purpose of proving something that is common sense. It seemed very obvious to me that, because spring and fall chinook salmon travel to the ocean at different times, that they would prefer different temperature changes (or none at all). But, it is better to test one's hypothesis, so this article was helpful in providing proof for a more obvious assumption.
Robert D. Clark Honors College, University of Oregon
HC 441: Science Colloquium, Columbia River Ecology
Fall term, 2005
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