Cooperative Fish and Wildlife Research Units Program: Pennsylvania
Education, Research and Technical Assistance for Managing Our Natural Resources

Vidal, T. E., B. J. Irwin, T. Wagner, L. G. Rudstam, J. R. Jackson, and J. R. Bence. 2017. Using Variance Structure to Quantify Responses to Perturbation in Fish Catches. Transactions of the American Fisheries Society 146:584-593. [Featured Article]


Unexpected shifts in the state-space conditions of an ecosystem can result in unintended and undesirable conditions, jeopardizing conservation efforts and efficacy of natural resource management. Previous research has identified general statistical behaviors associated with major ecological shifts, yet reliable prediction of these events remains limited. Development of statistical indicators to detect and forecast large-scale change (i.e., regime shifts) in ecological systems could prove valuable for better understanding population dynamics, continuing effective monitoring of fisheries resources, and allowing for timely management actions. Changes in mean and variance have been previously associated with large-scale shifts in ecosystems; here we provide evidence that source components contributing to total variability may also be responsive to large-scale shifts and therefore have potential as new statistical indicators of ecological response to a changing environment. We present a case study from Oneida Lake in NY that evaluates walleye catch rates over time in response to changes to tropho-dynamics and an exotic species invasion. Our results indicate that variance structure provides insight into how an ecosystem changes across space and through time, and also may serve as an indicator of instability and transition into an alternate stable state.