Food limitation in salt marsh fiddler crabs Uca rapax (Smith) (Decapoda : Ocypodidae)

Abstract

Abstract Two Uca rapax (Smith) populations were tested for food limitation in a Spartina salt marsh in Florida. Food supply was artificially increased by adding thin-cut Spartina . After a lag corresponding to the decomposition time of the grass, this resulted in a relative increase in fiddler crab population density, recruitment, and organic content. These results support the hypothesis that salt marsh fiddler crabs are food limited in biomass, and possibly in production, in spite of the abundance of detritus resulting from the large primary production in their habitat. Possible causes for food limitation are (a) lag in detritus availability from dead Spartina , (b) high density of consumers, (c) constraints on feeding time or space, (d) low assimilation efficiency, and (e) quality of the food resource. Fiddler crab burrows are known to enhance Spartina growth. Thus, one function of burrows may be to reduce food limitation.