Fishery Characteristics and Population Dynamics of Indian White Shrimp, Fenneropenaeus indicus from Arabian Sea, Sultanate of Oman

Monthly carapace length frequency data of Indian white shrimp Fenneropenaeus indicus were collected from commercial cast net catch from the Omani waters of the Arabian Sea at Al-Mahout fishing area. Sampling covered the first three months of the shrimp fishing season from September to November during two years 2010 and 2011, where more than 95% of shrimp catch was landed. FiSAT software program was used to analyze its length frequency distribution. The size structure of F. indicus is characterized by sexual dimorphism, where females are significantly larger than males. Allover sex ratio was slightly in favor of females with an overall sex ratio 1:1.1 in 2010 and 1:1.28 in 2011. Growth parameters (K and L sub([infinity])) were estimated based on age-length data obtained from Bhattacharya method (1967). Also, the instantaneous rate of total mortality (Z), natural mortality (M) and fishing mortality (F) were estimated and accordingly the exploitation ratio was determined as F/Z. Per-recruit analysis showed an overfishing situation for F. indicus in Oman and the present level of exploitation rate should be reduced by about 12% to achieve the maximum yield per recruit and by about 50% to maintain a sufficient spawning biomass. To overcome any bias in our estimations, we suggest a gradual decrease in fishing effort starting by 10% and make year-to-year analysis to adjust computations of fishing mortality and age at first capture.