Relationship Between Water Quality and Relative Weight of Four Sportfish Species in Oklahoma Impoundments

This project sought to classify 108 Oklahoma impoundments based on water quality as well as determine if water-quality parameters in these impoundments influenced the relative weight (Wr) of largemouth bass (Micropterus salmoides), white crappie (Pomoxis annularis) and black crappie (Pomoxis nigromaculatus), and channel catfish (Ictalurus punctatus). Agglomerative hierarchical clustering and subsequent discriminant analysis of seven water-quality parameters resulted in the grouping of impoundments into three classes. Chlorophyll-a, salinity, pH, and dissolved oxygen were the most important explanatory variables (83%) in impoundment classification. Class-1 impoundments (primarily located in east central and southeastern Oklahoma) had low salinity and pH values. Class-2 impoundments (spread statewide with a high concentration in the central part of the state) had mid-range pH and mid to low-range salinity values. Class-3 impoundments exhibited higher salinity and pH values. Mean Wr was relatively consistent among impoundment classes (largemouth bass=92?98, crappie=91?96, channel catfish=86?92), but individual impoundment Wr ranged widely among classes (largemouth bass=78?129, crappie=66?139, channel catfish=66?147), suggesting differences in fish condition among some impoundments. Multiple regression models found only a weak relationship among water-quality parameters and Wr , explaining no more than 11% of the variation among species, suggesting that additional research is needed before a solid model of lake classification can be suggested. Despite the lack of relation between Wr and water quality found in this study, other standard population metrics (e.g., size structure, age structure, and growth and mortality rates) may better characterize population health and therefore show a better correlation to limnological characters. Given the differences in water-quality parameters among impoundment classes noted in this study, a class-level goal for a particular metric might serve a better purpose and prove more beneficial to a manager than a statewide goal.

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