The papers presented within the section on streamflows and fisheries requirements reflect the increasing use of physical habitat simulation models to assess the effects of stream and river regulation on fish. Scott and Shirvell provide a critical review of the IFIM method and pose serious questions about eight of the basic assumptions underlying the method. In support of their cautionary tone they provide a summary of other studies, conducted worldwide, which show highly variable results when weighted usable area calculations are compared to the standing crop of fish. The submission by Geer describes a stepwise method of analysing the output from IFIM modelling and comparing recommended, optimal and historical flows and habitat conditions. Irvine experimented with a replicated series of five artificial streams in New Zealand. Compared to control streams, cyclic discharges were found to have very little effect on rainbow trout (Salmo gairdneri) fry biomass. In addition he found that a five-fold change in discharge did not produce any changes in the trout populations.
KeywordsTrout Population Regulate Stream Lotic System Cyclic Discharge Artificial Stream
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