A study of the biology of Indian mackerel,Rastrelliger kanagurta(Cuvier, 1817) in the Western Waters of Aceh, Indonesia was carried out from January to December 2014 and a total of 1343 Indian mackerels were collected randomly twice a month. The allometric coefficients (b) in the present study were between 2.625 and 3.449 with coefficient of determination (R2) values that range between 0.612 and 0.984. The condition factor (K) ranged from 0.9176 - 1.4509. Asymptotic length (L∞) and growth coefficient (K) and t0 were estimated at 27.3 cm (TL) 0.56 y-1 and - 0.526 y, respectively. The sex ratio of male to female was 1: 1.02. Overall, the sex ratios were not different significantly (χ2= 26.757; df= 11;p<0.05). The data suggest that there are two spawning seasons, the first is from January to March and the second is from August to October. The monthly mean GSI values ranged from 0.32 to 3.37. The observation of length at first maturity of female was estimated as 19.58 cm (TL). The fecundity ofR. kanagurtavaried from 28,542 to 123,760 with an average of 56,635 eggs.

Keywords: Biology,Rastrelliger kanagurta, Aceh