Mud Crab (Scylla serrata) Culture: Understanding the Technology in a Silvofisheries Perspective

Abstract

Abstract-A study was conducted in Mtwapa creek on the north coast Kenya, during 2005Kenya, during -2007 to evaluate the viability of pens and drive-in cages for mud crab (S. serrata) culture as a mangrove management strategy and alternative source of income for local communities. Other objectives were to assess the effectiveness of drive-in cage construction materials (fito and bamboo) in improving mud crab culture and influences return on investment. The applicability of morphomentric equations in estimating growth was also tested. Four replicate pens (6 m x 2 m) were stocked with 2 crabs/m 2 while individual drive-in cages (30 cm x 30 cm x 30 cm) were joined to form ten in one group (1 replicate) and a total of four replicates used. Uniform feeding was applied for all crabs in pens and drive-in cages using a mixture of fish offal and gastropod meat once a day at 10% body weight. Specific growth rate and survival of mud crabs were evaluated together with the cost of investment for the three months culture period. Drive-in cages recorded a significantly better survival and growth rate (53.2 ± 12.78%; 1.25 ± 0.42 g/day) compared to pens (31.25 ± 2.95%; 0.68 ± 0.24 g/day) p < 0.05 while no significant difference was observed between drive-in cages made of different materials (fito and bamboo). A link between growth rate and size of crab was observed, where growth rate decreased with increasing weight. Moulting associated factors contributed highly (45%) to the total mud crab mortality recorded (p < 0.05); mortality also had a strong positive relationship with moulting (R 2 = 0.79, p > 0.05). Strong relationships existed in morphomentric equations between carapace length and weight (W = 0.0006L 2.9941; R 2 = 0.86, p > 0.05). The construction costs for pens were three times more than those for a similar number of drive-in cages. Cost-return analysis on a per year basis/50 crabs showed that the use of either bamboo or fito as cage construction material was economically viable with a return on capital investment of 122.3 -181.7%. Therefore the integration of mud crab culture in mangrove forest is feasible in Kenya.

Growth, survival and intactness of green mud crab (Scylla Paramamosain) broodstock under different captive grow out protocols

“…SGR value of 1.25g/day for the drive-in cage culture condition and 0.68 g/day for pen culture system for mixed sex culture of adult S. serratawas previously reported in Kenya (David, 2009). In another reporton S. serrate mentined the SGR of 10 g/month in tanks, 19 g/month in cages, and 29 g/month in ponds (Srinivasagam and Kathirvel, 1992).On the other hand, SGR value of 70 g/month (2.33 g/day) for S. serrata monoculture by starting with juveniles of 7 g size (Marichamy et al, 1986)seemed quite consistent with this study.…”

“…Similarfaster growth in pond culture than cages and indoor tanks was previously reported for S. serrata (Srinivasagam and Kathirvel, 1992). On the contrary, a higher growth of mud crab under drive-in cages set into mangrove than the pen culture was reported (David, 2009). Meanwhile, a 40% less growth of S. serrata in cage system than pond culture or natural growth was stated (Moksnes et al, 2014).…”

“…Cannibalism in coupled with natural death (moulting death) lowered the survival in the tank culture system. Moulting death is the main fact of mortality in crustaceans (Cholik and Hanafi, 1992) and coupled with post moulting cannibalism reportedly reduce the survival and pointed as the main problem in mud crab aquaculture (David, 2009). In a study on S. serrata, the survial rate was 53.2% under drive-in cages and 31.25% under pen culture (David, 2009).…”

“…Moulting death is the main fact of mortality in crustaceans (Cholik and Hanafi, 1992) and coupled with post moulting cannibalism reportedly reduce the survival and pointed as the main problem in mud crab aquaculture (David, 2009). In a study on S. serrata, the survial rate was 53.2% under drive-in cages and 31.25% under pen culture (David, 2009). Whereas, survival rate of S. serrata was 45-57% under the drive-in cage culture system (Mirera, 2011), and that for pond culture was 40.2-51.6% (Trino et al, 2001).…”

Characterization of Major Allergens of Local Mud Crab (Scylla serrata)

“…Scylla serrata, commonly known as mangrove crab, mud crab or 'ketam nipah' belongs to the genus Scylla of family Portunidae. There is high consumer demand for Scylla serrata, particularly in countries comprising large Chinese communities such as Malaysia, Singapore, Taiwan and Hong Kong, where it is regarded as a delicacy, large chelae and high meat content [15]. Studies on identification of local crab allergens are very limited.…”