Mud crab fishery in climate vulnerable coastal Bangladesh: an analysis towards sustainable development

Developing countries are far more vulnerable to climate change impacts than industrialised countries. Most of the world’s poor live in South Asia where they have limited livelihood options that have become even narrower in recent years, indicating a need for alternative income-generating options. Mud crabs (Scylla spp.) are considered to have promising prospects in different parts of the world including Bangladesh, a well-known region for its vulnerability to climate change. At present, this fishery has become a growing venture in coastal Bangladesh, primarily due to the potential of the export market and availability of seed locally. This study included a calculation of the Human Development Index linked to mud crab fishery (HDIMCF) and a strengths, weaknesses, opportunities and threats (SWOT) analysis to clarify the present status of and strategic directions for the mud crab fishery, for the first time. Results revealed an intermediate level of development of mud crab aquaculture, indicating potential alternative livelihood opportunities for vulnerable coastal communities. The SWOT analysis revealed that positive factors, both internal (strengths) and external (opportunities), predominate over negative factors (weaknesses and threats) and that the fishery can be an alternative livelihood option for vulnerable coastal communities. Despite noticeable diversification of the mud crab fishery, dependence on wild seedstock and possible over-exploitation in the wild appear to constrain sustainable development of the fishery. This study’s findings suggest undertaking immediate wild crab stock assessment for determining current status of wild populations. Moreover, modification of the Government of Bangladesh’s existing mud crab policy is needed to better meet growing demand and sustainability of the fishery. Recommendations of this study may be of help in guiding responsible integrated coastal fisheries management and policy

Evaluation of production performance and profitability of hybrid red tilapia and genetically improved farmed tilapia (GIFT) strains in the carbon/nitrogen controlled periphyton-based (C/N- CP) on-farm prawn culture system in Bangladesh

Performance of hybrid red tilapia (Mutant, Oreochromis niloticus × Oreochromis mossambicus) and GIFT tilapia strain (Oreochromis niloticus) in C/N-CP prawn (Macrobrachium rosenbergii) farming system was evaluated at the farmers' pond at Bailor union under Trishal upazilla of Mymensingh district, Bangladesh. The on-farm trial had two treatments: TR and TG (named according to the tilapia strains) with three replications. Six rectangular ponds of varying sizes (400–880 m2) were used for this experiment. Hybrid red and GIFT tilapia stains were stocked with prawn at the stocking densities of 1 tilapia fingerlings (either red or GIFT strain) and 3 prawn juveniles m-2 in both treatments. Bamboo side shoot were posted vertically as periphyton substrate. This resulted in an additional substrate surface area of 1067 m2 for periphyton development equaling 147% of the pond surface area. Considering the body weight of freshwater prawn only, feeding rates were 10% of body weight at the beginning of the study (up to 30 days), and feeding application was gradually reduced to 3% in the last month assuming 80% survival. The abundance of total benthos and periphyton as well as total periphytic biomass were significantly higher (P < 0.05) in TR than TG treatment and they were also differed significantly (P < 0.05) among different months with a decreasing trends (exception to some extent) over the experimental period. The individual harvesting weight, individual weight gain, specific growth rate, Food Conversion Ratio (FCR), survival (%), gross and net yields of prawn were similar in two treatments. In contrast, the GIFT tilapia strain showed a higher (P < 0.05) individual harvesting weight, individual weight gain, specific growth rate ((SGR, % bw d-1), survival, gross and net yields (1935 and 1825 kg ha-1, respectively) combined gross and net yields (2952 and 2784 kg ha-1, respectively), and economic return (3755 US$ with BCR 0.82) than the hybrid Red tilapia