Use of minimum legal size in managing black clam (Villorita cyprinoides) fishery in India
Using size at first maturity (SFM) as a biological reference point, the minimum legal size (MLS) for the black clam, Villorita cyprinoides was fixed at 20 mm. Corresponding minimum legal weight was calculated as 3.4 g. The reproductive load and mean generation time were determined as 0.35 and 0.72, respectively. Of the total quantity of clams exploited during 1996-97, 50% were juveniles. The percentage was reduced to 7.9% during 2009-10. The loss in harvest weights due to exploitation of juvenile clam was 50%, 23% and 37% and the economic loss caused was US$ 4.6 million, US$ 1.5 million and US$ 1.1 million for the periods 1996-97, 2000-01 and 2002-03, respectively. If the undersized clams were permitted to grow up to MLS, the harvest weights could have improved by up to 24% and hence the economic gain is to the tune of US$ 1.40 million during 2009-10. The difference between the present Lmean in the fishery and the Lopt is 4 mm.