Assessing the Relative Importance of Estuarine Nursery Habitats – a Dungeness Crab (Cancer magister) Case Study
Estuaries serve as important nurseries for many recreationally and commercially important fisheries species. The value of these estuaries to fisheries species has long been assessed at an estuary-scale or between generalized habitat types. More recently, conceptual approaches (i.e., seascape) have advocated for complex habitat-scale assessments that integrate multiple response metrics and ecological processes across heterogeneous habitats. Although this approach is ecologically representative, implementing such an extensive framework may not be feasible for resource-limited organizations. In such cases, we posit that resource managers can improve their understanding of the relative values that estuarine habitats provide to fisheries by integrating attainable aspects of the seascape approach into a more traditional single response model. Using Dungeness crab (Cancer magister) as a case study, we applied a spatially explicit hybrid approach to assess the relative values of estuarine habitat to an important fishery species within three Oregon estuaries (Tillamook, Yaquina, and Alsea bays). We analyzed the abundance of juvenile C. magister and the mosaic of estuarine habitat (data from intertidal habitat surveys and the National Wetlands Inventory) within defined home-ranges, which allowed for movement of crabs among heterogeneous habitats. Results showed that side channels of intertidal flats in ocean-dominated reaches of estuaries supported the highest abundance of juvenile crabs; further analyses suggested that variation in crab abundance was driven by higher salinity in the lower estuary and the density of a burrowing shrimp (Upogebia pugettensis) on adjacent unvegetated tide flats. This hybrid method produced a habitat-specific model that better predicted juvenile C. magister abundance than a model based on generalized habitat categories.