Reproduction Aspects Of The “Sepetang” Clam (pharella acutidens) In Dumai Mangrove Ecosystem, Riau

Abstract

The Pharella acutidens population in Dumai mangrove ecosystem was decreasing due to increase in exploitation and mangrove degradation. This research aims to study the reproduction aspects and spawning season of the “sepetang” clam (Pharella acutidens). This study was carried out for 12 months, from November 2010 to October 2011 at Dumai mangrove. The “sepetang” clam samples were collected monthly from the Dumai mangrove ecosystem, from three stations. The clam were collected through sampling plots, 1 m x 1 m quadratic transects. Reproductive aspects such as sex ratio, gonadal development, gonadosomatic index (GSI), fecundity and oocytes diameter were studied. Results shown that sex of the “sepetang” clam can be determined at the size of more than 35 mm. Male and female ratio was 1 : 1.12 and no hermaphroditism observed. Histological analysis indicated that P. acutidens had four distinguishable gonad development in male and female clam, namely early active, late active, ripe and partially spawned. The fecundity increase as shell length increase and it correlated significantly with shell length. Mean oocytes diameter does not show any monthly pattern, except on May to June, the mean of oocyte diameter was relatively small. Based on gonadal development, GSI and mean oocyte diameter, the “sepetang” clam probably spawn continuously throughout the year with a peak spawning season between May-June