The stock assessment of the blue swimmer crab, Portunus pelagicus was made based on monthly length frequency data collected from four landing sites along the Oman coasts on both Arabian and Oman Seas from January, 2011 to May, 2012. Age and growth have been estimated from the length-frequency distribution of up to 1000 specimens. Age composition was determined using Bhattacharya's method and the results showed that the maximum life span of P. pelagicus was about 15 months. Bertalanffy (1938) growth parameters didn’t differ significantly between sexes and the obtained values of K were K = 1.85, 1.68 and 1.68 y-1 and CL values were 102.83, 109.57 and 108.46 mm for male, female and sexes combined, respectively. The values of total mortality coefficient (Z), natural mortality coefficient (M) and fishing mortality coefficient (F) were 7.85, 3.15 and 4.7 y-1. The yield per recruit and SSB analysis showed that the crab stock is being exploited beyond its maximum biological limit, but the increasing of fishing mortality to the level which gives the maximum Y/R (83% of its current value) will accompanied with a negligible increase in Y/R (2.7%) and a considerable decrease in both biomass per recruit (21.1%) and spawning stock biomass (37.6%).

The stock assessment of the blue swimmer crab, Portunus pelagicus was made based on monthly length frequency data collected from four landing sites along the Oman coasts on both Arabian and Oman Seas from January, 2011 to May, 2012. Age and growth have been estimated from the length-frequency dist...