Distribution of the Ark clam Barbatia decussata (Bivalvia: Arcidae) on rocky intertidal shores in the northern Persian Gulf

The Ark clam, Barbatia decussata (Bivalvia: Arcidae) is a member of intertidal communities occurring at rocky shores in the northern Persian Gulf. B. decussata is a permanent resident at the shaded side of the rocky substrates, attached by byssus threads. Distribution, density, shell length and weight parameters of this clam were explored in four sub area including Kohien, Hosseinabbad, Lengeh and Bostaneh from August 2011 to September 2012 (14 months) by monthly sampling on rocky intertidal shores in the northern Persian Gulf. The results showed that the Ark clam mostly occurred in the middle followed by lower intertidal zones and its random distribution was associated with substrate morphology mostly occurring on shaded sides of boulders and cobbles followed by in crevices. Mean density was estimated 8.4±2.1 (individuals per m2) in the study area. Although Mean density was not different between mid and low shore but it was significantly different among pairwise locations with exception of Bostaneh and Hosseinabbad. The mean shell length was significantly lower in mid shore (24.36mm) than low shore (30.13). Also the mean ash free dry weight (AFDW) in mid shore was significantly lower in mid shore (0.18g) than low shore (0.39g). Ashe free dry weight for this clam increases allometrically with shell length in mid shore (b= 2.79) and low shore (b=3) respectively.