Population dynamics of Metapenaeus dobsoni from the western coastal waters of Sri Lanka

The population dynamics of Metapenaeus dobsoni (Miers) from the west coast of Sri Lanka was investigated based on catch/effort and length frequency data, using FiSAT software. Annual yield of M. dobsoni was estimated at 296 t in 1998 and 362 t in 1999. This species formed 54% of the total shrimp catch from the system. The asymptotic length (L (infinity) ) and the growth rate constant (K ) were estimated to be 11.49 cm and 1.02 yr(-1) for males and 12.8 cm and 1.73 yr(-1) for females. The fishing mortality coefficients were 2.42 and 1.85 yr(-1) for males and females, respectively. The natural mortality was estimated at 1.72 yr(-1) for males and 2.51 yr(-1) for females. The recruitment for the estuarine environment and the offshore areas was continuous but peaked twice per year. The maximum sustainable yield (MSY) was estimated at 294.65 t, around the current catch estimates. To obtain maximum sustainable economic yield (MSE = 293.56 t) the present effort should be reduced by 10%.