LB 9-70 - Fish alter macroinvertebrate communities in recently flooded artificial ponds

Constructed ponds, the dominant lentic ecosystem in the Great Plains, are commonly stocked with bluegill and largemouth bass. 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 hectare) and depth (109 cm) near Stillwater, OK were flooded, and three were stocked with fish while the other three remained fishless. Each pond was sampled once per month for six months (August 2022 – February 2023) using a D-frame net. A total of 4,610 invertebrates representing 29 families were collected. Eight families made up 85% of the total collected individuals. Ponds with fish held 61.3% of the total collected Ceratopogonidae and 51.7% of Chironomidae. Fishless ponds held 74.4% of Baetidae, 64.3% of Notonectidae, and 53% of Stratiomyidae. Contrastingly, fishless ponds contained only 39.4% of the total collected Aeshnidae, 36.2% of Coenagrionidae, and 39.9% of Libellulidae. Fish presence is known to reduce the biomass of large, mobile invertebrates and increase the abundance of smaller invertebrates, thus, results with Odonata were unexpected. Likely, larger odonates in fishless ponds are consuming other odonates, reducing overall densities, whereas in ponds with fish, large odonates may feed on fish, along with other invertebrates. These results contribute to knowledge of conserving invertebrate diversity and the importance of maintaining some fishless pond environments. There are currently no other similar studies that have been conducted in Oklahoma.