Culture of Soft Shell Mangrove Crab, Scylla Spp. Production in the Southwest Region of Bangladesh

Abstract

The experiment was conducted for a rearing for a period of 150 days from mid-September to mid-February 2017 in three earthen ponds with an installing of 9880 cages per hectare with an average depth of 1.0 meter. The experiment was designed at the ponds of Kaligonj Chingri Farm as a treatment T1, Allarchar chingri farm as a treatment T2 and Shamnagar private crab farm as a treatment T3. Before stocking crabs were categorized at five size groups. At stocking, all crabs were with an initial mean carapace width and weight of individual was recorded in three treatments. The average final weight of crab was recorded to be 180.56±4.08, 175.80±7.11 and 178.62±6.42 g in treatment T1, T2 and T3, respectively. The increase in weight of mud crab was the highest in T1 followed by T3 and T2. About five group of different crab weight was stocked in the cages of three treatments. Best SGR (1.67±0.01) and FCR (2.00±0.08) were recorded in treatment T1. The highest survival rate was also observed in T1 and the lowest survival rate was in T2. There was a significant variation (P<0.05) in the survival rate of crabs among three treatments. The net production of crab was at 5082.51, 4689.63 and 4923.48 kg/ha in treatment T1, T2 and T3, respectively. Highest production of soft shell crab was recorded in treatment T1. But no significant (P<0.05) different was recorded in treatment T1 and T3. But a significant (P>0.05) different was found between treatment T2 and treatment T1 and T3. Majority of the crabs about 60-70% molted during night than day time. As the crabs were increased in size, molt duration became longer from 17.0 to 26 days. Overall, highest growth, survival, production and net benefit of soft shell crab recorded at treatment T1. Therefore, treatment T1 and treatment T3 appeared to be most suitable for soft shell crab culture for availability of saline water and trash fish in this area.

Effects of Water Quality on the Growth, Molting and Mortality Of Mud Crab, Scylla Serrata Forskal (Decapoda: Portunidae) From Cox’s Bazar

“…In this study, the range of alkalinity in the culture pond of Scylla serrata was found in between 50 and 133 mg/l with a mean of 104.67±6.83mg/l. Chakraborty (2019) recorded water alkalinity ranging from 127.48±7.14 to 136.08±8.44mg/l in the three crab culture earthen ponds in the South west region of Bangladesh which is a little bit higher than the present study. However, Hossain (2007) recorded the soil alkalinity values of 41.10 ppm and 69.70 ppm in the two experimental stations of the mangrove swamp forest of Chakaria, Sundarban, Bangladesh, while Zafar and Hasan (2005) recorded the values of soil alkalinity from 49.0 to 52.5 ppm at Poshur River mangrove fringe, Sundarban.…”

“…Crab farmers collect the mud crab during this time as soft shell crab (Oesterling and Moore 1995). Soft shell crabs are in high demand in international markets due to their easy edibility in comparison to hard shell crabs and their high nutritional value (Chakraborty 2019). The commonly cultivated soft shell crabs are blue swimmer crab (Portunus pelagicus) and mud crab (Scylla serrata) (Niswar et al 2018), while Scylla sp.…”

Tidal periodicity of molting in giant mud crab, Scylla serrata (forskål, 1775)

“…As a result, when there is a shelter nearby, the frequency of molting increases [6]. According to research, the time of molting was higher at night, particularly during night high tides [4], [15]. Because the molting itself causes mud crabs vulnerable to cannibalism or predation [8].…”

Effects of Temperature and Diurnal Cycle in the Molting Schedule of Mangrove Crab, Scylla serrata (Forskål, 1775)

“…Furthermore, results supported the statement of Hosamani et al (2016) that molting is affected by temperature and photoperiod. A related study by Chakraborty (2019) also found that the time of molting (Scylla spp.) was during nighttime at 60-70% more than day time.…”