Population dynamics and reproduction ofHolothuria arenicola(Holothuroidea: Echinodermata) in coastal waters of Pakistan, North Arabian Sea

Abstract

In Pakistan, although the sea cucumber fishery has not yet been developed,Holothuria arenicolais abundant on its coast. Nineteen months of sampling was carried out to study the population structure, allometric relationships and reproductive status ofH. arenicolastocks in Manora and Buleji rocky shores. All measured biometric characters showed significant temporal variations and width/length, weight/length, gutted weight/length and gutted weight/weight relationships followed negative allometry, indicating a change in body shape as the animal grows. Length-frequency distribution analysis was bimodal in both summer and autumn consisting of small-sized and medium-sized individuals while in winter and spring three modes were found at Manora. At Buleji, the population was unimodal in all seasons consisting of small-sized individuals. Sex inH. arenicolacannot be determined externally but can be identified on examination of gonad colour which is orange-like in females and creamy yellow in males. The sex was further confirmed on histological examination and maturation was divided into five stages, i.e. undetermined, early developing, late developing, mature and partially spawned. The sex ratio inH. arenicolawas approximately 1:1 and increase in gonad index was observed during spring and early summer, followed by a decrease in GI in autumn and winter, which showed the spawning followed by resting phase. The GI showed a significant negative correlation with salinity and non-significant correlation with temperature. There is a need to undertake more biological/ecological studies onH. arenicolain order to take effective measures for its management.