Nursery habitat use by juvenile blue crabs in created and natural marshes

O_LIClimate change and coastal development pressures have intensified the need for shoreline protection. Nature-first approaches that use natural habitats, particularly marshes, are being promoted globally as ecologically-beneficial alternatives to grey infrastructure. The ability of these novel shorelines to provide nursery habitat to blue crab, an ecologically and economically important species along the Atlantic and Gulf coasts of the United States, has not been quantified. C_LIO_LIWe quantified the abundance and size distribution of juvenile blue crabs from a chronosequence of living shorelines (created fringing marshes) spanning 2 to 16 years in age (since construction) and compared with paired natural fringing marshes in the southern Chesapeake Bay. C_LIO_LIBoth created and natural fringing marshes are being used by blue crabs as primary nursery habitats. While there were interannual differences in abundance, young blue crabs ([≤] 2.5 cm carapace width) were observed in similar densities and sizes at living shoreline and natural marshes. There was no relationship between the age of the living shoreline and blue crab density, indicating that even the youngest living shorelines (2 years) were providing primary nursery habitat. Young blue crabs were more abundant in more isolated marshes and those that were inundated for longer periods of time each tidal cycle, which may be evidence for habitat-limitation. C_LIO_LISynthesis and applications: We provide evidence that juvenile blue crabs are comparably using natural and created fringing salt marshes as primary nursery habitat. Although the relative importance of salt marshes as young crab nursery habitat is not fully understood and likely varies by system, the value of marshes within a suite of available structural nursery habitats may increase under a changing climate. The potential for living shorelines to serve as nursery habitat for an economically important species may provide additional incentives to implement these climate adaptation strategies. C_LI