Influence of Ice Angler Culling Practices on Bluegill Physiological Stress Responses and Mortality

Abstract

Decreasing bag limits is a management mechanism for enhancing size structure of Bluegill Lepomis macrochirus. However, restrictive bag limits can promote culling, where an angler returns a live fish to the water in exchange for another. Little is known about the effect of culling on ice-angled fishes. Our objective was to compare the effects of Bluegill confinement methods (reference, ice well, and bucket) and holding durations (0, 1, 2, or 5 h) on changes in water quality parameters (dissolved oxygen, pH, carbon dioxide, and water temperature) and Bluegill stress physiology (blood glucose and plasma cortisol), reflex responses (reflex action mortality predictor [RAMP] scores), and mortality while ice angling. In February 2018, 182 Bluegills were angled through the ice and randomly assigned a confinement method and holding duration. Bluegill blood glucose levels were higher in both confinement methods than reference fish at 2-h and 5-h holding durations. Bluegills had higher blood glucose levels in buckets than ice wells at 1 and 2 h, but they had higher blood glucose levels in ice wells at 5 h. Water temperature was warmer in buckets than ice wells at all holding durations, while ice wells were cooler than ambient lake temperature. Bucket pH was higher than the lake at 2 h, and ice well pH was higher than the lake at 1 and 2 h. Bluegill RAMP scores were similar across all holding durations and confinement methods, but they were elevated in individuals held for the 24-h mortality assessment. Two Bluegill mortalities occurred for fish held in ice wells. Our results suggest that confinement method and holding duration while ice angling can result in altered Bluegill blood glucose concentrations, water temperatures, and pH concentrations but that culling while ice angling might not result in mortality. Consequently, culling practices may be compatible with and not negate the intended benefits of reduced Bluegill bag limits.