Biological control of invasive fish and aquatic invertebrates: a brief review with case studies

We review various applications of biocontrol for invasive fish and aquatic invertebrates. We adopt a broader definition of biocontrol that includes traditional methods like predation and physical removal (biocontrol by humans), and modern approaches like genetic engineering and use of microbes (including pathogens). While physical removal and predation (by native predators) are used relatively commonly, use of genetic technologies and microbes is in developmental stages. The two latter strategies are most advanced in case of the common carp (Cyprinus carpio), one of the world’s most invasive fish; virus release to control carp might soon occur in Australia. Drawing from empirical examples in North America, we emphasize that biocontrol strategies are most likely to be successful if they include multiple approaches that target specific behaviors or weaknesses in pests’ life histories. This is illustrated by reviewing case studies on the common carp and rusty crayfish (Orconectes rusticus) in Midwestern North America. In case of the common carp, basic research on movement patterns and recruitment bottlenecks identified a strategy where winter aggregations of adults were targeted for removal with nets, while native predators of carp eggs and larvae were instrumental in controlling carp’s reproductive success. In the case of the rusty crayfish, basic research on interactions between crayfish, habitat, and native predators identified a successful strategy of stocking selected native predators to control juvenile crayfish in conjunction with physical removal of adult crayfish using traps. We are also reviewing the case of the round goby (Neogobius melanostomus) in the Great Lakes. In this example, multiple pieces of evidence (diet, bioenergetics) illustrate how initially abundant pest was brought under control (in some areas) by several species of native predators in a large, natural ecosystem. Overall, examples of successful biocontrol of aquatic pests have been rare and have relied on physical removal and predation. We expect that new technologies (e.g. genetic technologies) will occur in the next decade but will have to clear regulatory and ethical concerns before they are applied. While developing more sophisticated control techniques, we advocate for more basic research on the life history of the pests to identify behavioral or developmental weaknesses that could be targeted with specific tools to increase chances of success while minimizing impacts on native ecosystems.