VARIABILITY IN FLOW-HABITAT RELATIONSHIPS AS A FUNCTION OF TRANSECT NUMBER FOR PHABSIM MODELLING

摘要

A bootstrap analysis was used to assess the variability in flow-habitat relationships for juvenile and adult rainbow trout (Oncor-hynchus mykiss) in the Cache La Poudre River as a function of the number of Physical Habitat Simulation System (PHABSIM) transects. The bootstrap analysis was conducted by selecting without replacement different numbers of transects, ranging from six to 40, from a pool of 107 transects. The variability in flow-habitat relationships, as quantified by the 95% confidence interval for the flow with the peak habitat, decreased with increasing numbers of transects, and was greater for juveniles than for adults. The 95% confidence limits ranged from 9% for adult trout with 40 transects to 73% for juvenile trout with six transects. The results of this study can be used in negotiations for the number of transects selected during scoping of instream flow studies, as well as in assessing the relative confidence that should be placed in flow-habitat relationships for different species and life stages.