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 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%).
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