Crab population monitoring: Spring 2001 mid-marsh and creekbank crab abundances based on hole counts at GCE marsh, monitoring sites 1-10

There are a number of crab species that inhabit the vegetated intertidal marshes of the GCE-LTER permanent monitoring sites. The most frequently encountered species are Uca pugnax, U. pugilator, U. minax, Sesarma reticulatum, Armases cinereum, and Eurytium limosum. These species are highly mobile at various tide stages and seek the safety of burrows when not foraging. Their behavior patterns make it difficult to accurately assess their abundance within the constraints of our current monitoring activities. To do so would require a sampling program dedicated solely to that unique end. This study was designed to use counts of crab holes as a relatively quick and easy way to estimate total crab densities at the GCE-LTER sites. Such a method does not differentiate which species made a particular hole and therefore only estimates total crab abundance. Plugged holes were excluded from the counts. Our initial data yielded an average across all sites of 239 crabs (all species) m^-2. Our initial conclusion is that crab hole counts allow the estimation of crab densities and yields estimates comparable to those methods requiring extensive time and effort. This method will be used to estimate crab densities in the Spring and Fall (yearly) within the GCE-LTER domain.