The Use of a Pattern Judgement Model to Assess Fish Habitat Suitability in Two Colorado Reservoirs

ABSTRACT

The suitability of two Colorado reservoirs to support an array of common fish species was assessed using a pattern judgement model. The model employs an expert panel to predict habitat suitability based on easily measured structural characteristics of the reservoir basin, local site climate, operational regime, and inflow characteristics. Model predictions, made before Kenney Reservoir was filled, indicated mat common carp (Cyprinus carpio) and black crappie (Pomoxis nigromaculatus) would dominate the fish community in this reservoir. Sampling in the decade following completion of the dam substantiated this prediction. When additional species were added to the model and their likely performance in Kenney Reservoir evaluated, predictions offish community composition closely followed trends observed in reservoir species composition. A proposed enlargement of an existing reservoir was evaluated with the model to predict what species might prosper as a result of the new configuration of the reservoir basin and inundation of new land areas. None of the 10 species evaluated were predicted to flourish in the new habitat provided by the enlargement. Predictions were consistent with the low abundance of these species in the existing reservoir and the probable lack of suitable habitat in the enlargement area. The pattern judgement model can be used to explore management options dealing with probable species performance as a function of the quality of available habitat using relatively static data garnered at low cost. The model's flexibility allows modification of input variable values to reflect local conditions or specific needs without altering model logic. Guidance is provided for adding more species to the model to broaden its applicability to other waters.

Key Words:

• reservoir fish habitat
• pattern judgement model