Using indirect methods to estimate population parameters of the Atlantic ghost crab from beaches in Northeastern Cuba

Abstract

Sandy beaches are dynamic systems that harbor diverse macrofauna species, such as the ghost crab Ocypode quadrata, which has a wide distribution and it is considered useful in ecological evaluations. Population parameters of O. quadrata based on indirect methods were assessed at four tourist sandy beaches at northeastern Cuba from September 2010 to August 2011. Monthly samplings were carried out early in the morning. At each beach, five cross-shore transects were set at 50–60 m intervals, and consecutively 2x2 m quadrats were set from the upper swash level to the landward edge. Active burrows were counted and measured to the nearest millimeter using a caliper. Burrow density showed differences among beaches and a negative relation to the number of visitors. Burrow size showed differences among beaches as well as a positive relation to temperature, and non-significant relations to salinity and number of visitors. Burrow size frequency distribution showed a unimodal pattern skewed toward smaller sizes at the four beaches. Growth rates ranged from 0.57–1.4 year−1 and the growth performance was high (Φ′>3) at the four beaches. Growth performance was compared with other ocypodid populations (Uca spp., O. quadrata and Ucides spp.) inhabiting tropical coastal ecosystems using an auximetric plot. All ocypodid populations clustered forming one single ellipsoid in the auximetric plot supporting the use of borrows count and size as a reliable, non-invasive method to estimate population dynamics of this indicator species.