Gender-specific Morphological Growth Patterns of the Estuarine Mud Crab Scylla olivacea in North-eastern Sundarbans, Bangladesh

Abstract

The economic expansion of estuarine mud crab Scylla olivacea necessitated for the inclusive research on its biological characteristics, especially morphological features. This study explored the gender- specific growth pattern and condition factors of S. olivacea from the coastal waters of Sundarbans, Bangladesh. A total of 360 S. olivacea were collected using a nonmechanized trap from the landing center of Rampal Upazila at Bagerhat District in Bangladesh, and their body weight (BW), carapace width (CW), carapace length (CL), abdominal length (AL), and propodus length (PL) were measured. The male-to-female ratio was 1:0.87, and females (BW: 107.02 ± 24.99 g, CW: 7.98 ± 0.74 cm) were significantly heavier than males (BW: 98.03 ± 24.00 g, CW: 7.48 ± 1.02 cm). The inter-relationship of CW with BW, CL, AL, and PL was significant. Body weight showed a negative allometric growth pattern with CW (b < 3) for both sexes. Carapace length showed a positive allometric growth pattern with CW (b > 3) in male crabs but an isometric growth pattern (b = 3) in female crabs. The calculated mean condition factors (Fulton’s condition factors, allometric condition factors, and relative condition factors), for male and female crabs were higher than or close to one, indicating crabs were in a healthy state and the average relative weight was 100 g and above for both male and female samples were in healthy physiological condition in the study area. This study provides knowledge on the current condition and distinguishing morphometric features of local S. olivacea which will assist fisheries resource managers and conservation biologists for the better management of this commercially important crab species in Bangladesh waters.