Response of juvenile rainbow trout to turbulence produced by prismatoidal shapes

Publication Date



juvenile, rainbow trout, trout, turbulence, water velocity, habitat, salmonids, high velocity, swimming, flume, turbulent

Journal or Book Title

Transactions of the American Fisheries Society


Water velocity is a common measure of habitat suitability for salmonids. It is oftennoted that salmonid focal positions occur in low-velocity areas adjacent to high-velocity ones.Such locations are associated with increased turbulence. Turbulence in the stream regionstypically occupied by salmonids is produced by flow separation around large objects such asrocks or on the riverbed. Turbulence has also been shown to increase the energetic cost ofswimming for salmonids. Despite the link between cover and turbulence, no measurements ofturbulence at the focal positions of juvenile salmonids have been reported in the literature. Wemeasured turbulence at the focal positions of juvenile rainbow trout (Oncorhynchus mykiss) in alaboratory flume and found that those focal positions were characterized by low turbulence levelsacross a range of average velocities. Fish occupied highly turbulent locations if excessiveaverage velocities were present. Eddy size, measured as the autocorrelation function of thevelocity time series at a point, did not result in obvious correlations with focal positionestablishment, but it was correlated with turbulence levels. Turbulence provided some additionaldiscriminatory resolution, allowing differentiation of potential focal positions of equal averagevelocities but different turbulence levels. Thus, accounting for turbulence levels may allow moreaccurate prediction of focal positions.





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