Mohamad N. Azra

A review of maturation diets for mud crab genus Scylla broodstock: Present research, problems and future perspective

Study of broodstock maturation diets is important in order to increase the quality of berried females, which indirectly improve the larval quantity in the hatchery production of cultured species. This paper reviewed the studies on the maturation diets for mud crab broodstock, genus Scylla and compared independently to identify their effect on reproductive performance and larval quality. The broodstock is usually caught from the wild and held in the spawning or maturation tank for further use of hatchery seed production. Mud crab broodstock was fed either natural diet, artificial diet or mixed diet. Trash fishes were commonly used as a natural feed for mud crab broodstock; meanwhile artificial diets are from formulated fish meal and various kinds of feed. The results indicated that mud crab broodstock has a high dietary requirement for lipids, fatty acids and protein which are to be used during the maturation and breeding processes. However, the natural diet produce better larval quality compared to the artificial diet. The mixed diet is the better diet which resulted in better reproductive performances such as growth, survival, fecundity and maturation processes. This review also discusses the problems in the previous studies for the potential future research to develop very high quality and cost-effective formulated diet for the enhancement of broodstock and seed production technology. Information from this review can be useful in developing a better quality of crustacean broodstock’s diet for commercial hatchery production.

Thermal tolerance and locomotor activity of blue swimmer crab Portunus pelagicus instar reared at different temperatures

Owing to its potential market value, the blue swimmer crab Portunus pelagicus is of great economic importance. The temperature of water significantly affects the physiological function and production efficiency of these crabs. The aim of the present study was therefore to examine the critical thermal minimum (CTMin), critical thermal maximum (CTMax), acclimation response ratio (ARR), escaping temperature (Tesc), and locomotor behavior of P. pelagicus instars at 20 °C, 24 °C, 28 °C, 32 °C, and 36 °C. The CTMax ranged from 39.05 °C to 44.38 °C, while the CTMin ranged from 13.05 °C to 19.30 °C, and both increased directly with temperature. The ARR ranged from 0.25 to 0.51. The movement of crabs (walking before molting) correlated positively with the acclimation temperature. These results indicate that the parameters evaluated varied with temperature. Furthermore, the high CTMax indicates the potential of this species to adapt to a wide range of temperatures. In addition, the implications of these findings for portunid crabs behavior and distribution in their natural habitat are also discussed.

Digestive enzyme profiles from foregut contents of blue swimming crab, Portunus pelagicus from Straits of Johor, Malaysia

Abstract This study describes the digestive enzyme profiles from foregut contents of the blue swimming crab, Portunus pelagicus (L.), from Straits of Johor, Malaysia. Adult male (mature and immature) and female (ovarian maturation stages 1–4) blue swimming crabs were assayed for the presence of digestive enzymes (protease, trypsin, amylase and lipase) in the foregut. The results show that in some instances, significant differences in enzyme activities were observed between the sexes of P. pelagicus. Protease, trypsin, and amylase were detected in all gonad maturation stages, suggesting that crabs including immature males can readily digest dietary protein and carbohydrates, but not lipids. Trypsin (except for ovarian maturation Stage 4) and lipase (ovarian maturation Stage 4 and mature male only) activities were considerably higher than amylase, indicating that dietary proteins and lipids are more important than carbohydrates and, thus, suggests a carnivorous diet. In conclusion, the changes in enzyme activities between the different maturation stages and sexes reflect natural changes in diet and feeding abilities of P. pelagicus.