Seasonal variations in the distribution of pedunculate barnacle Octolasmis spp. on <em>Scylla </em>serrata (Forskal, 1775) from the Ayiramthengu mangroves, Kerala

Abstract

Present study is to understand the seasonal distribution and infestation rate of pedunculate barnacles <em>Octolasmis</em> spp., in <em>S. serrata</em>. Altogether 103 crabs were analysed and a total of 2070 barnacles were obtained from 87 infested crabs. Barnacle infestation was more prevalent on the gills and was found to differ significantly by season, size and sex. They are more abundant during the premonsoon months when salinity is higher in the estuarine waters. The mean intensity of infestation was less in monsoon compared to pre-monsoon and post-monsoon, which registered a very high incidence of 18.33 and 40.21 respectively. Larger crabs host more barnacles than younger ones. The less active, bottom seeking females are more vulnerable to the infestation and the barnacle load was higher in them. Barnacles cause respiratory obstruction in the host and heavy infestation leads to high mortality.