Population biology and larval morphology of the edible crab (Scylla serrata) from Karachi backwaters [Pakistan]
2001
Mustaquim, J. (Karachi Univ. (Pakistan). Centre of Excellence in Marine Biology) | Imtiaz, R. | Sultana, R.
This paper deals with population biology and morphology of zoea larvae of the edible crab (Scylla serrata). The crabs were collected from the Sandspit backwaters for a period of two years. The size at sexual maturity, sex ratios, growth and moulting, size frequency distribution, stomach content, fecundity, egg size and morphology of prezoea and first zoea were studied. All the male crabs having carapace width greater than 69 mm were found mature and their testis and vasa deferentia were ripe and contained numerous spermatophores. Female crabs having carapace width greater than 72 mm were found mature, having ripe ovaries with developing eggs. Sex ratios in smaller size-classes were 1:1 but in larger size-classes males outnumbered females. Size frequency analysis revealed bimodal pattern. Immature crabs were abundant in winter while adult crabs dominated the population in summer. Small crustaceans and fish were found as major food items eaten by S. serrata. Not a single ovigerous female was found in the backwaters. However, four ovigerous females, having carapace width from 99 to 113 mm, were collected from offshore waters. The average number of egg was found to be 1,489,268 plus minus 294,462 (SE).
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