The Size Structure, Growth, Mortality, and Exploitation Rate of Freshwater Clam (Batissa violacea var. Celebensis) from Southeast Sulawesi, Indonesia

Abstract

ABSTRACT Freshwater clams, better known as pokea clams in Indonesia, are among the important economy-generating resources whose population continues to decline in line with the increase in fishing activities. The present study aims to determine the age group, growth, mortality, and exploitation rate of pokea clams. This research was conducted in the estuary segment of Laeya River, Southeast Sulawesi, Indonesia, from March 2016 to February 2017. Pokea samples were taken using a traditional fishing tool called Tangge. Data on age groups, growth, mortality (natural, fishing, and total) and exploitation rate were processed using the Bhattacharya method, the von Bertalanffy inverse function, the width converted catch curve, and Pauly's empirical formula, respectively, accommodated in the FiSAT II program version 3.0. The results showed that the male and female pokea were spread out in 1 and 2 size groups. Male pokea was dominated by 2 size groups, whereas the female pokea was dominated by 1 size group. The growth of the male and female clams followed the equations Lt = 83.89 – (83.89–0.025)e–0.54t and Lt = 77.38 – (77.38–0.025)e–0.52t. The male natural mortality (M), fishing mortality (F), and total mortality (Z) were 2.04 y–1, 0.91 y–1, and 2.94 y–1, respectively, whereas the natural mortality, fishing mortality, and total mortality of the female clams were 1.51 y–1, 0.90 y–1, and 2.41 y–1, respectively. In general, the male and female pokea clams in the Laeya River are overexploited, with the exploitation rates of 0.69 and 0.63, respectively.