Fish As Biocontrol Agents: An Integrated Pest Management Tactic Worth Considering for Quagga Mussels?

The quagga mussel, Dreissena bugensis, is a devastating aquatic pest that recently invaded the western United States. Many existing mussel control methods are problematic for infested systems in the west because these systems serve as primary water sources for humans. To address this problem, we investigated the efficacy of using resident fishes as biocontrol agents for managing quagga mussels. We conducted field experiments to test whether planktivorous bluegill sunfish, Lepomis macrochirus, reduced mussel infestations on substrates of varying orientations and water depths through predation on larval mussels. We also conducted an experiment to evaluate whether the carnivorous redear sunfish, Lepomis microlophus, reduced mussel infestations on substrates of varying orientations with and without established mussel populations through the predation of juvenile and adult mussels. Bluegills significantly reduced mussel populations on all substrates and at all depths through predation on larvae and small, juvenil mussels. Redear sunfish reduced juvenile and adult mussel populations, but consumption varied among individuals and with substrate orientation. Our results indicate that fishes may represent effective site-specific biocontrol agents for quagga mussels. As such, biological control should be considered when developing an integrated pest management strategy for quagga, and potentially zebra, mussels.