Comparison of Foraging Performance of Diploid and Triploid Saugeyes (Sauger × Walleye)

Abstract

Abstract To evaluate the performance and quality of triploid saugeyes (female walleye Stizostedion vitreum × male sauger S. canadense), we compared their foraging behavior with that of diploid conspecifics. Triploidy was induced by heat-shocking fertilized eggs for 15 min at 31°C 5 min after fertilization, and ploidy was evaluated by flow cytometry. In three experiments using both ploidy groups we evaluated (1) prey selection with respect to fathead minnow Pimephales promelas and the daphnia Daphnia pulex; (2) aggression and food consumption by individual saugeye predators during a single feeding session; and (3) handling time of a single large (50-60% of predator body length) minnow. Juvenile diploid saugeyes foraged more successfully than triploid conspecifics. Diploids caught fathead minnow significantly more frequently than did triploid fish (59% and 39% of available minnow, respectively) while consuming significantly fewer daphnids. Triploids fed on zooplankton to a larger extent. Experiment 2 reveal...