Evaluating ecological restoration in urban ecosystems with acoustic telemetry: marine and freshwater case studies

Around the globe, ecological restoration projects are being undertaken to mitigate anthropogenic impacts and recover lost biodiversity; however, evaluations of efficacy can lack robustness or, more often, are not completed at all. In this perspective piece, to demonstrate the utility of acoustic telemetry to assess ecological restoration in aquatic systems, we synthesize two case studies in coastal freshwater and marine urban ecosystems: Toronto, Canada, and Bergen, Norway. In Toronto Harbour, a Before-After-Control-Impact experimental design was instrumental in detecting differences attributed to ecological restoration across multiple species of fish. Additionally, acoustic telemetry data were paired with catch and community traits derived from electrofishing, which provided a more complete understanding of fish responses to restoration. In Bergen Harbour, the acoustic telemetry array was deployed before restoration, providing a Before-After comparison of habitat use by several fish species and European lobster (Homarus gammarus). In addition to acoustic telemetry, blood samples were taken from multiple fishes, to examine the levels of contaminants before and after restoration, adding an ecotoxicological dimension to the assessment. Incorporating these complementary methods contributed to a more holistic understanding of animal response to ecological restoration. Finally, we also identified indicators that could be calculated using acoustic telemetry data, including those derived from addition sensors (e.g., pressure). As we look to the future within the Anthropocene, it will be imperative that ecological restoration achieves intended goals and we contend that acoustic telemetry has a bigger role to play in the evaluation of efficacy as it provides continuous monitoring compared to more traditional, discrete sampling.