Multifaceted management of commercially harvested fish in Lost Island Lake, Iowa
Andrew K Carlson, Michael J Hawkins, Jonathan R MeerbeekAbstract
Objective
Invasive Common Carp Cyprinus carpio cause lake management challenges in the Midwestern United States including increased turbidity and decreased macrophyte abundance and growth. Although they are native and long-lived in this region, overabundant, zooplanktivorous Bigmouth Buffalo Ictiobus cyprinellus may indirectly contribute to eutrophication by releasing algae from grazing pressure and are targeted by commercial fishers due to high market prices. Individual tools for managing these species (e.g., fish barriers, toxicants, harvest) have had limited utility for improving water quality and sport fisheries in Iowa, but there may be promise in integrating these methods. Our study tested whether integrating lake restoration techniques affected water quality, sport fisheries, and macrophytes in Lost Island Lake, Iowa.
Methods
We present a case study of multifaceted management in which Common Carp and Bigmouth Buffalo were simultaneously subjected to spawning-access restrictions, commercial harvest, rotenone, and increased piscivore densities. We used a treatment–reference lake design along with generalized linear models and generalized linear mixed models to compare water quality parameters, fish relative abundance, and macrophyte species richness and coverage before and after lake restoration efforts.
Results
From pre- to postrestoration, there was a significant increase in Secchi depth and significant decreases in chlorophyll-a, nitrate nitrogen, pH, total suspended solids, and turbidity. We observed significant, sustained increases in the relative abundance of socioeconomically valuable sport fish (i.e., Black Crappie Pomoxis nigromaculatus, Bluegill Lepomis macrochirus, Largemouth Bass Micropterus nigricans, White Bass Morone chrysops, Yellow Bass M. mississippiensis, and Yellow Perch Perca flavescens) when Common Carp and Bigmouth Buffalo were less abundant. The macrophyte community—defined solely by cattails Typha spp. before restoration—became more diverse, with native species such as sago pondweed Stuckenia pectinata expanding considerably after restoration.
Conclusions
Our results underscore the importance of integrating fisheries management techniques—including fish barriers and water-level control structures, incentivized (subsidized) commercial harvest, targeted rotenone application, and piscivore stocking—to improve water quality and sport fisheries. The longevity of this multifaceted approach to management was notable, with benefits to Lost Island Lake lasting more than 10 years. Our study provides a foundation on which to expand the scope of multifaceted fisheries management by testing these methods in lakes along gradients of productivity, morphometry, and geography.