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EVALUATING VISUAL STREAM HABITAT ASSESSMENT TECHNIQUES <br />TO MODEL TROUT BIOMASS <br />ROBERT P. LANKA <br />WAYNE A. HUBERT <br />WYOMING COOPERATIVE FISHERY AND WILDLIFE RESEARCH iJNIT <br />and <br />THOMAS A. WESCHE <br />WYOMING WATER RESEARCH CENTER <br />UNIVERSITY OF tin'OMING <br />LARAMIE, WYOMING 82071 <br />ABSTRACT <br />Traditional methods to estimate trout biomass in streams are time <br />consuming and costly. An alternative to these methods is a model to <br />predict trout biomass. Stream Reach Inventory and Channel Stability <br />Index (SRICSI) is a technique to visually assess channel and streambank <br />stability (Pfankuch 1975). Several investigators have shown that good <br />to fair stability ratings are associated with the highest trout popula- <br />tion. Ninety-four stream reaches in Wyoming and Colorado with SRICSI <br />ratings and concurrent measures of biomass were analyzed. Initial <br />statistical analysis indicated forested and non-forested streams need <br />different models. <br />INTRODUCTION <br />Available methods to estimate trout standing stock in streams are time <br />consuming and costly. Modeling habitat to predict standing stock offers an <br />alternative to direct measurements of community composition and standing <br />stock. The Trout Cover Rating Method (Wesche 1980) quantifies instream and <br />bank cover and predicts brown trout (Salmo trutta) standing stocks. The <br />Habitat Quality Index (Binns 1979) uses nine habitat variables and pr. edicts <br />trout standing stock. These methods, as with the direct measures they are <br />to replace, are field intensive and costly. A logical goal in stream habitat <br />assessment is to develop a method that requires little field work and is an <br />accurate predictor of trout standing stock. <br />The Stream Reach Inventory and Channel Stability Index (SRICSI) is a <br />visual assessment of channel and streambank stability (Pfankuch 1975). Its <br />main application has been on second to fourth order mountain streams to <br />evaluate the resistance of stream channel substrate and bank material to <br />detachment. The SRICSI has been used to assess stream fisheries habitat. <br />Brouha and Renoud (1981) compared SRICSI scores to fish standing stock and <br />found that a SRICSI score between 77-83 (fair) was associated with the <br />21 <br />