AUTHORS: Jacob L Bentley, The Ohio State University; Stuart A Ludsin, The Ohio State University
ABSTRACT: The intentional introduction of nonnative predators to generate novel fisheries, while common, has the potential to threaten existing fisheries through numerous mechanisms such as competition and predation. Similarly, stocking success could be hampered by these same mechanisms, highlighting the need to understand habitat use and niche overlap among biota. In Ohio reservoirs, Blue Catfish (Ictalurus furcatus) has been stocked since 2010 to create novel trophy fisheries. However, the potential exists that the success of Blue Catfish will either threaten the success of existing fisheries or threaten the success of the stocking program if niche overlap among species is high. To assess niche overlap and the potential for competition among stocked Blue Catfish, native predators (e.g., Channel Catfish, Ictalurus punctatus; Largemouth Bass, Micropterus salmoides), and stocked saugeye (Sander canadensis x S. vitreus), we analyzed the diets and stable isotope ratios (nitrogen, carbon, and sulphur) of muscle tissue from fish collected during spring, summer, and fall of 2021-2023 in two Ohio reservoirs: one stocked with Blue Catfish (Hoover Reservoir) and one not stocked with Blue Catfish (Alum Creek Lake). We hypothesized that niche overlap would be highest between catfish species, with Largemouth Bass and saugeye also overlapping. Our hypothesis was only partially supported. Results show niche partitioning between Blue Catfish and all other species. Blue Catfish consumed more and larger fish prey (e.g., large-bodied Gizzard Shad) relative to all other species, with Channel Catfish feeding mostly on aquatic insect larvae (e.g., chironomids). By contrast, Largemouth Bass and saugeye primarily fed on smaller-bodied Gizzard Shad than Blue Catfish, with their diets being similar as expected. In addition to quantifying niche envelopes for these species, we discuss how our findings, and stable isotopes in general, can be used to help inform stocking decision-making in reservoir ecosystems.
