Use of streambed substrate as refuge by steelhead or rainbow trout Oncorhynchus mykiss during simulated freshets |
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| Authors: | F K Ligon R J Nakamoto B C Harvey P F Baker |
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| Institution: | 1. Stillwater Sciences, Arcata, CA, U.S.A.;2. USDA Forest Service, Pacific Southwest Research Station, Arcata, CA, U.S.A.;3. Stillwater Sciences, Berkeley, CA, U.S.A. |
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| Abstract: | A flume was used to estimate the carrying capacity of streambed substrates for juvenile steelhead or rainbow trout Oncorhynchus mykiss seeking refuge from simulated freshets. The simulated freshets had mean water column velocities of c. 1·1 m s?1. The number of O. mykiss finding cover within the interstices of the substrate was documented for different substrate sizes and levels of embeddedness. The availability of suitable refuges determined the carrying capacity of the substrate for O. mykiss. For the size of the O. mykiss tested mean ± s.d. fork length (LF) = 122 ± 12·6 mm], the number of interstices with depths ≥200 mm measured with a 14·0 mm diameter flexible plastic tube was the best predictor of the number of O. mykiss able to find cover (r2 = 0·75). Oncorhynchus mykiss seeking refuge from freshets may need deeper interstices than those seeking concealment at autumn or winter base flows. The availability of interstices suitable as refuge from high flows may determine autumn and winter carrying capacity. |
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| Keywords: | displacement embeddedness flood high flows interstitial velocity |
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