Landscape drivers of freshwater mussel assemblages and imperiled species status: implications for optimal allocation of conservation effort within the Delaware River Basin
Dates
Start Date
2020-10-01
End Date
2022-12-31
Summary
Aquatic ecosystems are among the most imperiled systems on the planet (e.g., Vorosmarty et al. 2010), and freshwater mussels represent a particularly threatened taxonomic group that exemplifies the challenges of assessing numerous rare, cryptic taxa. North America contains the greatest diversity of freshwater mussels globally, but nearly two-thirds of 300 currently recognized species are considered imperiled and 29 are likely extinct (Haag and Williams 2014). While national-level efforts have compiled portfolios of research and management actions to support freshwater mussel conservation (FMCS 2016; Ferreira-Rodriguez et al. 2019), managers urgently need robust frameworks for deciding how to allocate funding and capacity across these [...]
Summary
Aquatic ecosystems are among the most imperiled systems on the planet (e.g., Vorosmarty et al. 2010), and freshwater mussels represent a particularly threatened taxonomic group that exemplifies the challenges of assessing numerous rare, cryptic taxa. North America contains the greatest diversity of freshwater mussels globally, but nearly two-thirds of 300 currently recognized species are considered imperiled and 29 are likely extinct (Haag and Williams 2014). While national-level efforts have compiled portfolios of research and management actions to support freshwater mussel conservation (FMCS 2016; Ferreira-Rodriguez et al. 2019), managers urgently need robust frameworks for deciding how to allocate funding and capacity across these potential actions.
Identifying an optimal portfolio of conservation actions depends on the goals of conservation efforts, the feasibility and effectiveness of management practices, and the relative risk to species persistence across management units. Efforts to conserve freshwater mussels may support multiple, competing objectives. For example, while efforts to maintain biodiversity might focus on bolstering rare species, efforts to improve water quality may benefit by propagating functionally dominant mussels with greater probability of persistence. Potential tradeoffs between the protection of imperiled species or maintenance of ecosystem services contribute to uncertainty in which actions to prioritize.
Structured decision making and multi-attribute tradeoff analysis provide an explicit and transparent framework for identifying the sensitivity of management decisions to uncertainty and competing objectives (Runge et al. 2020). Past work by project leaders has developed regional conservation plans using these approaches, including multispecies plans in the upper Tennessee River Basin (Smith et al. 2017) and species-specific efforts for the Brook Floater (Alasmidonta varicosa; Roy, unpublished) and Dwarf Wedgemussel (Alasmidonta heterodon; Smith et al. 2015; Smith and McCrae 2020). In the present study, we seek to build upon the structured decision-making processes developed previously by incorporating an empirical model of the dominant environmental and anthropogenic factors influencing freshwater mussel community structure and resilience. In addition to advancing basic understanding of diversity patterns within mussel assemblages, developed models will aid decision making on which and where actions should be applied to maximize identified objectives for conservation of imperiled freshwater mussels.
The Delaware River provides an ideal case study for developing a basin-wide conservation strategy for imperiled freshwater mussels in the North Atlantic-Appalachian Region. The watershed contains 12 species of Atlantic slope mussels (Blakeslee et al. 2018), including the federally endangered Dwarf Wedgemussel and the at-risk Brook Floater. Nearly 15 million people depend on its water supply, and propagation of freshwater mussels is actively being pursued by conservation groups to aid water quality improvements in the estuary. The variation in dominant stressors throughout the basin, from environmental flow issues in the upper basin to water quality issues and saltwater intrusion in the lower basin, coincide with documented shifts in mussel community composition (Blakeslee et al. 2018). These complexities require a deliberative and transparent process to identify robust and collaborative conservation strategies. Our research activities will help foster a basin-wide perspective on mussel conservation and identify collaborative strategies for implementation by federal, state, and non-governmental groups working in the Delaware. The approach to assessing threats and prioritizing actions will be transferable to other watersheds with similar mussel assemblages.
Objectives:
The overarching goal of this project is to develop a framework to inform decisions on the allocation of conservation effort across potential actions and watersheds to advance freshwater mussel conservation in the Delaware River Basin. This will be achieved through a structured decision-making process to identify robust conservation strategies, combined with predictive modeling of existing data to understand the local and landscape stressors affecting mussel community resilience throughout the basin. Specifically, this project seeks to:
Identify portfolios of freshwater mussel conservation actions based on national recommendations, locally identified objectives, and feasibility
Develop predictive models of the stressors and conservation efforts affecting freshwater mussel resilience and community structure
Integrate multi-attribute tradeoff analysis with empirical models to inform spatial application of freshwater mussel conservation actions
