World Aquaculture September 2018

WWW.WA S.ORG • WORLD AQUACULTURE • SEP TEMBER 2018 45 ( C O N T I N U E D O N P A G E 4 6 ) Female employees are generally from impoverished households, and a majority are divorced, widowed or separated from their families. The mud crab fishery is considered the second highest employment generation sector in the region after black tiger shrimp farming (Salam et al. 2003, Jahan and Islam 2016). Soft-shell crab farming is viewed as one of the best and most resilient income opportunities for people in natural disaster-susceptible coastal Bangladesh. Hatchery development and scaling up. Sustainability of the crab seed supply is the most critically important limiting factor for industrial development of soft-shell crabs. Globally, the large majority of soft-shell crab farm operations are based on supplies of wild stock (Hungria et al. 2017). The soft-shell crab farms in Bangladesh require a daunting number of crab juveniles for continuous production. Presently, depending on farm size, 1-5 t of small seed crabs are needed daily for stocking. The supply of natural mud crab seeds is not sufficient to meet the steady demand by soft-shell crab farms, causing some loss of production and limiting industry development. Therefore, mud crab hatchery establishment (Fig. 7) and technological development for hatchery raised crablet production are urgently needed (Islam et al. 2015). Successful hatchery production can support a regular supply of seed crabs for grow-out culture systems to produce adequate numbers of properly-sized juveniles after the nursery phase. A sustainable and reliable supply of stockable crabs for soft-shell farms would thus reduce pressure on wild stocks (Perry et al. 2010). In this way, soft-shell crab production offers considerable potential for expansion and development in the scaling up of grow-out crab farming. Expansion of crab culture consequently has the potential to benefit marginalized coastal farmers by building farm capacity, thereby generating economic improvement (Huq et al. 2015). Ancillary operational facilities including communication systems, electricity, processing plants, stocking materials such plastic boxes, PVC pipes, feeds, commercial hatchery seed production, packaging materials, and shipments or transportation services are also need and will contribute to regional employment and economic benefits of continued industry development. Feasible use ofwasted crab shell. A large quantity of hard-shell crabs are generated in soft-shell crab production, and at present these are discarded in landfills, without any economic use (Fig. 8). An es- timated 6-8 million t of waste shells of crab, shrimp and lobster are generated globally each year (Yan and Chen 2015). Crustacean shells contain 20-50 percent calcium carbonate, 20-40 percent protein, and 15-40 percent chitin that could potentially be used for pharmaceuticals, paper industries, cosmetics, textiles, water treatment as well as fertiliz- ers and animal feed production. The development of new uses for this byproduct could have added economic and environmental value. Potential for co-culturewithfish. Because soft-shell crab produc- tion is practiced in boxes occupying the surface level of ponds, there is a potential for integration with fish culture under the caged crabs in the same pond. For co-culture farming, bottom-dwelling species can be stocked to enhance farm production and income. Also, fish can serve as aerators that improve water quality and can graze phytoplankton, filamentous algae, and macrophytes in ponds as well as attached pe- FIGURE 5. Women mince fish for feed in a soft-shell crab farm in Shyamnagor, Satkhira, Bangladesh (Photo: Md. Mojibar Rahman). FIGURE 6. Percentage of men and women employed by soft-shell crab farms of various sizes in coastal Bangladesh. FIGURE 7. Mud crab hatchery and technology development in Shyamnagor, Satkhira (Photo: Md. Mojibar Rahman). FIGURE 8. Plenty of wasted crab shells produced in soft-shell crab farms in Shyamnagor, Satkhira (Photo: Md. Mojibar Rahman).