LOCOMOTOR, ESCAPING ACTIVITIES AND FATTY ACID COMPOSITION OF MUD CRAB, SCYLLA OLIVACEA AT DIFFERENT WATER VELOCITIES

Abstract

This study was designed to determine the locomotor, escaping capability and fatty acids (FAs) composition of muscle Scylla olivacea mud crabs at different water velocities. Male and female immature S. olivacea were cultured at 0, 20, 40 and 60 cm/sin a recirculating marine aquaculture system. Increase in flow velocity increased the mean locomotor activity and escaping capability of the crabs. Significant differences were observed between sexes for both activities in all velocities tested (p < 0.05). Male and female crabs reared at the lowest flow velocity (0 cm/s) exhibited a mean of 13 and 55 locomotion per 15 minutes tested, respectively. Meanwhile, in the highest flow velocity (60 cm/s), male and female crabs exhibited 61 and 70 locomotion’s per 15 minutes. A total of 3111 locomotion were recorded during the entire experiment. An increase in the water velocities increased the mean escaping capability of the crabs. A total of 32 crabs attempted to escape during the flow velocity tests (0 cm/s; n = 3, 20 cm/s; n = 9, 40 cm/s; n = 11, and 60 cm/s; n = 9). The locomotor of crabs increased gradually and peaked at 40 cm/s (seeking for shelter). By contrast ≥ 40 cm/s the locomotor of crab decreased (defensive mode). For FAs analysis, total fatty acids (TFAs) content was found highest at 20 cm/s compared to other velocities. This study clearly show that the locomotor activities, escaping capabilities and FAs composition of S. olivacea were affected by water velocities under laboratory conditions.