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

Abstract

Jagora asperata (Lamarck, 1822) known to Bicolanos as tabagwang is an edible mollusc species thrivingin rivers of the Bicol region. It is being harvested and cooked in coconut milk mixed with edible fern. Thereis a dearth of information regarding its biology and fishery in the Bicol region. This absence of informationnecessitated this study. The study was conducted in Buradan River, Viga, Catanduanes, from January 2013to May 2014. Spatial distribution of the species was observed to be a clumped distribution (mean index ofaggregation is 0.03). There were 28,921 individuals gathered: the average length is 40.14 mm and averageweight is 4.57 g. The length-weight relationship was obtained as W = 0.00025 × L=2.624. The estimatedlength-at-first maturity was 32.04 mm for females and 33.64 mm for males. This species exhibits ovoviviparityas the mode of development. The distribution of the sexes is 1:1. Gonado-somatic index is highest in themonths 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 perrecruit, corresponding to a length of 48.29 mm, and the F(MSY) is 3.5 per year. The results showed that thepopulation of J. asperata is overexploited and overfished, and management policy must be implemented forthe stock to recover