Playing to Stay in the Game: A Sportfish's Adaptive Response to Change

Large river systems are among the most anthropogenically influenced aquatic habitats, often degraded by multiple factors. Environmental variability caused by anthropogenic factors can increase the vulnerability of fish to habitat instability. Life-history traits can be used to manage species in response to these changes by providing an understanding of their population dynamics. The differential expression of life-history traits within a system due to environmental variability can be used to determine habitat improvements needed to manage productive fisheries. Our study used two years of targeted electrofishing data to describe differences in life-history expression of bluegill Lepomis macrochirus resulting from differences in habitat quality and availability. In total, 526 bluegill were processed from three distinct habitats within the Illinois River system: upper Illinois River, lower Illinois River, and Emiquon Preserve, a disconnected restored backwater adjacent to the lower Illinois River. Analyses indicated that bluegill size distribution, growth coefficient, gonadosomatic index, and fecundity differed among habitats. This could potently lead to lower lifetime fecundity and offspring of lesser quality in poor habitat. These results highlight the differences in habitat availability throughout the Illinois River system, how it affects bluegill life-history expression, and emphasis the need for habitat improvements within the lower Illinois River.