An Integrated Pest Management Tactic for Quagga Mussels: Site-Specific Application of Fish Biological Control Agents

The quagga mussel Dreissena bugensis is a harmful aquatic pest that invaded the southwestern USA in 2007. Challenges with managing this pest have been encountered because the invaded systems are primarily open-water sources used for human consumption and/or are connected to freshwater habitats containing threatened and endangered species. Existing chemical and physical control methods are undesirable, and the use of some methods is restricted or prohibited because they pose risks to humans and ecosystems more broadly. To address this problem, we investigated the efficacy of using resident fishes as biocontrol agents for managing different life stages of quagga mussels on different spatial scales in a site-specific manner. We conducted field experiments to test whether planktivorous Bluegill Lepomis macrochirus reduced mussel infestations on substrates of varying orientations in small and large pens through predation on larval mussels. We also performed an experiment to evaluate whether carnivorous Redear Sunfish L. microlophus reduced mussel infestations established on substrates of varying orientations in small pens through predation on juvenile and adult mussels. Bluegill significantly reduced mussel infestations on all substrates in the pens through predation on larvae and small juvenile mussels. Redear Sunfish reduced existing juvenile and adult mussel populations in some cases, with consumption varying among individuals and substrate orientations. Our results indicate that fishes, specifically Bluegill, may represent effective site-specific biocontrol agents for quagga mussels, reducing impacts on targeted infrastructure (e.g., water towers, docks, and pipes) and habitats having different surface orientations by controlling more than one life stage of the pest. Development of an integrated pest management strategy that considers application of this tactic in combination with others would undoubtedly improve the management of quagga mussels-and potentially that of congeneric zebra mussels D. polymorpha-within lake and reservoir ecosystems.