You are here:
Fish Assemblage Models for Alternative Futures
Citation:
Ebersole, Joe, B. Beebe, A. Brookes, AND B. Rashleigh. Fish Assemblage Models for Alternative Futures. Joint Aquatic Sciences Meeting, Grand Rapids, MI, May 14 - 20, 2022.
Impact/Purpose:
Fish communities in river networks provide significant ecosystem services that will likely decline under future land use, human water demand, and climate variability. We developed a model that simulates the consequences to multiple populations of one or more fish species from multiple stressors across a river network. The model is spatially-explicit and age-structured, with three components: habitat suitability; population dynamics, including species interactions; and movement across a spatial network. We apply the model to a fish assemblage in the Willamette River basin of Oregon, a region where human population and water demand are expected to grow substantially over the next 50 years. Although this model is simple, it can form the basis of fisheries assessments and may be incorporated into an integrated modeling system for watershed management and prediction.
Description:
The ability to forecast future distributions of freshwater fish species is a pressing management need, but is complicated by climate change, invasive aquatic species, and on-going human demands for water and other natural resources. Paired climate-hydrological models suggest a warmer and more hydrologically variable environment for many streams and rivers. Shifts in distributions of native species are already detectable. At the same time, efforts are underway in many watersheds to slow or mitigate adverse changes to aquatic ecosystems, even as human pressures on water and land resources increase. We discuss a spatially-structured fish assemblage modeling framework that we are using to explore linkages between environmental change and fish population responses and to generate hypotheses that can be tested via additional research and monitoring of restoration efforts. In our case study river network in Oregon, model results under future warming scenarios indicate high probability of extinction for a cold-water salmonid, with substantial expansion by some, but not all, cool-water fish species. Larger, lower-gradient stream reaches may experience substantial shifts in fish species assemblages with strong species interaction effects on assemblage structure. Smaller headwater streams are more strongly influenced by colonization/extinction events associated with physical habitat dynamics. Opportunities for managing and influencing future trajectories through habitat restoration, water quality improvements, or mitigation of disturbances such as wildfire also differ across the watershed. These results and highlight the importance of considering the joint effects of physical, ecological, and social (human) dynamics on future fish populations.