Biological Inputs to the Management of Tabagwang (Jagora asperata) in Buradan River Viga, Catanduanes, Philippines

Publisher: Bicol University PDF

Abstract

Jagora asperata (Lamarck, 1822) known to Bicolanos as tabagwang is an edible mollusc species thriving in rivers of the Bicol region. It is being harvested and cooked in coconut milk mixed with edible fern. There is a dearth of information regarding its biology and fishery in the Bicol region. This absence of information necessitated this study. The study was conducted in Buradan River, Viga, Catanduanes, from January 2013 to May 2014. Spatial distribution of the species was observed to be a clumped distribution (mean index of aggregation is 0.03). There were 28,921 individuals gathered: the average length is 40.14 mm and average weight is 4.57 g. The length-weight relationship was obtained as W = 0.00025 × L=2.624. The estimated length-at-first maturity was 32.04 mm for females and 33.64 mm for males. This species exhibits ovoviviparity as the mode of development. The distribution of the sexes is 1:1. Gonado-somatic index is highest in the months of October and December. The estimated population param were: L ∞ = 71.26 mm, K= 0.39 year−1,Z= 1.85 year−1; M= 0.69 year−1; and F= 1.16 year−1. Exploitation rate is 0.63. The estimated MSY/R is 6.53 g per recruit, corresponding to a length of 48.29 mm, and the F(MSY) is 3.5 per year. The results showed that the population of J. asperata is overexploited and overfished, and management policy must be implemented for the stock to recover.