Examining diet variability and the ecological role of green sunfish (Lepomis cyanellus) in Great Plains streams

Green Sunfish (Lepomis cyanellus) are opportunistic predators, that readily consume a variety of invertebrates, with insects comprising a significant part of their diet. The consumption of insects by Green Sunfish has ecological implications, as they play a role in influencing insect populations in their habitats. Additionally, their ability to consume a variety of prey items contributes to their success as a species in a wide range of aquatic environments. Diet variability in fish is thought to be influenced by consumer body size due to gape limitations and indeterminate growth. However, prey availability and energetic benefits should also play a role, as suggested by optimal-foraging theory. In this study, our objective was to investigate the effects of body size of Green Sunfish on the number of unique prey items, variation in prey selection, and mean body size of prey. We hypothesized that as Green Sunfish increased in body size, there would be an increase in the number of unique prey items, variation in prey selection, and mean body size of prey. To test this hypothesis, we analyzed stomach contents from over 300 Green Sunfish in streams across the Kansas River Basin in the Flint Hills ecoregion of Kansas. Additionally, we conducted a mesocosm experiment to examine changes in diet variability with fish body size. This research is significant as green sunfish populations are growing due to habitat alterations and they likely serve as important meso-predators in streams.