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Diet of the Orangebelly Darter, Etheostoma radiosum, among Tributaries of the Lower Mountain Fork River

Reed, Melissa Lynn

Previous studies, in the Blue and Glover Rivers of Oklahoma, revealed that the endemic orangebelly darters, Etheostoma radiosum, are selective feeders with diets consisting primarily of aquatic insect larvae and dominated by fly larvae. In this study, orangebelly darters were collected from tributaries of the Lower Mountain Fork River, below Broken Bow Dam, with backpack electrofishing equipment in February and April 2015. One hundred and forty-one darters were captured from five tributaries and stomach contents were examined to determine benthic macroinvertebrate prey use. Standard length of darters was compared to determine if size differed among tributaries. Non-insect food items were grouped by order, while insect food items were identified to family. Prey composition was compared among tributaries. A total of 11 food types were found, with isopods being the most frequently consumed organism. Other common food items included aquatic insects in the families Heptageniidae, Chironomidae, Perlidae and Simuliidae (in order of abundance). Although no significant difference was found for darter lengths, a significant difference for consumed isopods was found among the tributaries. Darters appeared to be generalist feeders on aquatic macroinvertebrates in most tributaries and utilized different prey than previously reported. Additionally, for the first time, Acanthocephalan (Spiny-head worm) parasites were found in the stomachs of 17 of the orangebelly darters (Bee branch = 12, Beaver = 3, Rough Branch = 2). Studies such as this improve knowledge of freshwater biodiversity, ecology, and conservation and highlight differences in diet among populations of small fish inhabiting headwater tributaries and main channels in southeastern Oklahoma.