부산대학교 도서관

Redband trout (Oncorhynchus mykiss ssp.) in southeastern Oregon inhabit high-elevation streams that exhibit extreme variability in seasonal flow and diel water temperature. Given the strong influence and potential limitations exerted by temperature on fish physiology, we were interested in how acute temperature change and thermal history influenced the physiological capabilities and biochemical characteristics of these trout. To this end, we studied wild redband trout inhabiting two streams with different thermal profiles by measuring (1) critical swimming speed (U[subcrit]) and oxygen consumption in the field at 12° and 24°lC; (2) biochemical indices of energy metabolism in the heart, axial white skeletal muscle, and blood; and (3) temperature preference in a laboratory thermal gradient. Further, we also examined genetic and morphological characteristics of fish from these two streams. At 12°, maximum metabolic rate (Mo[sub2 max]) and metabolic power were greater in Little Blitzen redband trout as compared with those from Bridge Creek (by 37% and 32%, respectively). Conversely, Bridge Creek and Little Blitzen trout had similar values for Mo[sub2 max] and metabolic power at 24°C. The U[subcrit] of Little Blitzen trout was similar at the two temperatures (61 ± 3 vs. 57 ± 4 cm s[sup-1]). However, the U[subcrit] for Bridge Creek trout increased from 62 ± 3 cm s[sub-1] to 75 ± 3 cm s[sub-1] when water temperature was raised from 12° to 24°C, and the U[subcrit] value at 24°C was significantly greater than for Little Blitzen fish. Cost of transport was lower for Bridge Creek trout at both 12° and 24°C, indicating that these trout swim more efficiently than those from the Little Blitzen. Possible explanations for the greater metabolic power of Little Blitzen redband trout at 12°C include increased relative ventricular mass (27%) and an elevation in epaxial white muscle citrate synthase activity (by 72%). B [ABSTRACT FROM AUTHOR]