Propagated Fish in Resource Management

A Modified Suitability Index to Guide Selection of Stocking Waters for Juvenile Tiger Muskies

Keith Koupal


Abstract.—The Colorado Division of Wildlife and Colorado State University teamed up to develop a modified suitability index to guide stocking decisions of tiger muskellunge (northern pike Esox lucius × muskellunge E. masquinongy). A categorical-based index stemming from historical stocking success, literature references, and logic was deemed the most appropriate approach because staff wanted a functional index that was easy to use and required little additional data collection. The modified suitability index is composed of five primary attributes and a community predator rating. Primary attributes selected for this index were temperature regime, water clarity, seasonal cover, escapement potential, and availability of prey. Each primary attribute receives a score of 1, 2, or 3, and an overall suitability rating of low, low-medium, high-medium, or high is assigned. A separate assessment of fish and bird predators is conducted to determine a community predator rating. The community predator rating is used to adjust the suitability rating and determine a final water description. A high water description has the best chance of recruiting stocked tiger muskellunge to the second fall, and a low water description has the worst chance of recruiting success. The modified suitability index shows promise as a useful tool for apportioning limited numbers of juvenile tiger muskellunge as validation efforts have predicted stocking success. Consequently, the professional community should find this categorical-based index useful when management demand exceeds hatchery supply and funds are lacking to pursue full-fledged investigations.