Does loss of salt marsh vegetation caused by a native grapsid crab improve habitat suitability for the Atlantic mud fiddler ( Uca pugnax)?

Abstract

The abundance of Uca pugnax(Smith, 1870), the Atlantic marsh fiddler crab, has been shown to be both positively and negatively related to vegetation cover in a number of previous studies. In Cape Cod National Seashore marsh (Massachusetts, USA), it appears that the abundance of U. pugnaxis high in areas where salt marsh vegetation has died back as a result of Sesarma reticulatum(Say, 1817), the purple marsh crab, activity compared with healthy, vegetated areas. However, this relationship has not been experimentally tested. In this study U. pugnaxburrows were enumerated in treatments consisting of 1) vegetation and sediment removal, 2) naturally occurring dieback areas where vegetation is absent, 3) vegetation removal by cutting, and 4) intact vegetation. The results indicate that U. pugnaxmay prefer open, unvegetated habitats with softer substrates. The proliferation of U. pugnaxin open areas could therefore be facilitated by S. reticulatum, which has consequences for a number of other ecosystem processes.