Reproductive biology of the commercial sea cucumber Holothuria atra (Holothuroidea: Aspidochirotida) in the northwestern coastal waters of Sri Lanka

Sea cucumbers are a conspicuous component of the macrobenthos in the tropical marine environment and support numerous artisanal fishing activities throughout the Indo-Pacific. Although sea cucumbers have been subjected to various investigations by many authors, little attention has been given to species in the coastal waters of Sri Lanka. The reproductive biology of Holothuria atra, the most abundant and widely distributed commercial species was investigated in the northwestern coastal waters of Sri Lanka from July 2008 to 2009. When the reproductive biology of H atra was evaluated using gonadal indices and histology of gonads, it was found that synchronous seasonal gametogenesis with some asynchrony among individuals during the prolonged spawning season and individuals with mature gonads were dominant throughout the year, reaching a peak in March and September. In addition, population structure was assessed based on sex ratio, minimum reproductive size and the relationship between the reproductive pattern and environmental parameters. The sex ratio of H atra was found to be close to 1:1. Spawning began in April and October when temperature was at a maximum. Length at first sexual maturity was 16.0 cm (total length). Fecundity of H atra was in the range of 430 x 10(3) to 5,993 x 10(3) oocytes per individual.