Nematopalaemon tenuipes (Aramang) forms almost 100 % of catch by drift filter nets in the Cagayan River Estuary. It is caught throughout the year. The fishery shows varied annual fluctuations for the last five years with an average annual production of 3,314.596 metric tonnes; the resource does not appear to be under threat of over fishing at present due to increasing production of catch from 1996 to 2013. The maturity, fecundity and GSI of aramang were determined from collected samples from the gatherers during the observance of management intervention known as Gentlemen’s Agreement (May 2012 to March 2013). Five maturity stages of non-berried and berried aramang occurred throughout the observation period where nearly ripe and ripe seemed to be dominant comprising more than 70 % in occurrence. The size at maturity was found to be 45 mm in total length with an estimated mean fecundity of 974.92 eggs. Pearson correlation showed a significant relationship between fecundity and size at (p < 0.01). However, no significant correlation (p > 0.01) was found between GSI and size. The seasonal variation in the GSI showed continuous spawning of N. tenuipes throughout the year. Using mesh size 1.60 cm was efficient to exclude small size of aramang in the catch, thereby attaining an ideal catch size resulting in better price and higher profit.