Benefits to being fishless: Macroinvertebrate communities differ in recently flooded artificial ponds with and without fish

Constructed ponds, the dominant aquatic ecosystem in the Great Plains, are commonly stocked with bluegill, Lepomis macrochirus, and largemouth bass, Micropterus salmoides . However, fishless ponds are increasingly being recognized as important for promoting macroinvertebrate diversity. We compared the macroinvertebrate community assemblages of fishless ponds to those stocked with bluegill and largemouth bass in an experimentally replicated environment. Six artificial ponds of equal size (0.1 hectares) and depth (109 cm) near Stillwater, OK were flooded. Three were stocked with fish fry while the other three remained fishless. Each pond was sampled once per month from August 2022 through June 2023 using D-frame net sweeps. A total of 6,945 invertebrates representing 33 families were collected, with nine families accounting for 81.6% of the individuals. Fishless ponds held 56.5% of the individuals while ponds with fish contained 43.5%. Shannon diversity and Simpson's index values did not significantly differ between ponds with fish and those without. Bray-Curtis dissimilarity values and NMDS analysis indicated that ponds with fish foster community similarity, resulting in a similar taxa composition across individual ponds, while taxa in fishless ponds exhibit greater variability in taxa composition across ponds. The abundance of one of the nine most common families (Notonectidae) were significantly reduced by fish presence. Results indicate that fish alter communities for sensitive taxa, but do not alter overall abundance and numbers for other less sensitive taxa. These results contribute to the knowledge of conserving invertebrate diversity and the importance of maintaining fishless water bodies.