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

Abstract

Climate 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 fully evaluated. We 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) compared with paired natural fringing marshes in the southern Chesapeake Bay. Both created and natural fringing marshes are being used by blue crabs as primary nursery habitats. Despite 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. The age of the living shoreline was not related to blue crab density, indicating that even the youngest living shorelines (2 years) were providing nursery habitat. Young juvenile blue crabs were more abundant in more isolated marshes and in marshes inundated for longer periods of time each tidal cycle, which may be evidence for habitat-limitation. Our results 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 incentive to implement these climate adaptation strategies