Bigger is not always better for overwintering young-of-year steelhead

Transactions of the American Fisheries Society
By:  and 



Many fishes occur across broad ranges of latitude and elevation, where winter temperatures can vary from mild to harsh. We conducted a laboratory experiment with three sizes of age-0 steelhead Oncorhynchus mykiss to examine growth, condition, and energy reserves under low rations at three levels of water temperature typical of this species' distribution during winter. At the end of the 111-d experiment, all three starting sizes of age-0 steelhead (small, 2-3 g; medium, 3-4 g; large, 4-5 g) held in 3??C water had lower total lipid weight than those held in 6??C and 9??C water. Large fish had higher total lipid weight than small fish at the onset of the experiment and retained higher amounts at the end. However, large fish had either the lowest percentage increases or the highest percentage decreases in fork length, biomass, condition factor, total lipid weight, and percent lipids within all thermal treatments. The magnitude of the differences between small and large fish was highest in the warmest (9??C) water. We used bioenergetics simulations of juvenile steelhead growth to examine fish response to initial size, winter temperature, and food availability. Relatively warm water temperatures in winter, coupled with limited food availability, may present more of a physiological challenge to larger age-0 steelhead than to smaller fish. Our results suggest that achievement of large size before the start of a steelhead's first winter can have a cost under episodic conditions found across the wide ranges of latitude and elevation within this species' distribution.

Publication type Article
Publication Subtype Journal Article
Title Bigger is not always better for overwintering young-of-year steelhead
Series title Transactions of the American Fisheries Society
DOI 10.1577/1548-8659(2003)132<0262:BINABF>2.0.CO;2
Volume 132
Issue 2
Year Published 2003
Language English
Publisher Taylor & Francis
Contributing office(s) Western Fisheries Research Center
Description 13 p.
First page 262
Last page 274
Online Only (Y/N) N
Additional Online Files (Y/N) N
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