Evaluation of Supplemental Pellet Feeding and Threadfin Shad Addition on Stable Isotope Signature and Potential Influence on Fish Growth in Recreational Fishing Ponds

Pond enhancements such as adding pelleted feed or stocking threadfin shad (Dorosoma petenense) are sometimes used in the management of pond fisheries, but their relative impacts on growth and reproduction at multiple levels of the food web are not often fully evaluated. We used stable isotope analysis to indicate the contribution of pelleted feed to bluegill (Lepomis macrochirus) reproduction and growth, and ultimately to largemouth bass (Micropterus salmoides) growth in the presence and absence of threadfin shad via two different approaches: a pond experiment and sampling of established ponds. Bluegill growth and reproductive metrics increased with increased rates of pelleted feed provided. Bluegill nitrogen signature decreased with pelleted feed in the small pond experiment, suggesting feeding at a lower trophic level with increased feed. Largemouth bass nitrogen signature results showed similar trends to that of bluegill, although not statistically significant. In established ponds, pelleted feed appeared to alter the carbon isotopic signatures of both bluegill and largemouth bass independent of threadfin shad presence. These results suggest that adding pelleted feed to recreational largemouth bass-bluegill ponds can contribute to carbon flow, possibly through multiple trophic levels. The apparent lack of effect of pelleted feed on largemouth bass growth in established ponds is likely due to low and variable feeding rates and other management limitations found in more typical non-controlled field settings.

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