M.A. Kabir Chowdhury

Changes in mangrove forest soils: a comparison between cultured and naturally inundated conditions

A study was carried out in three shrimp farms in a natural mangrove area at the southeastern part of Bangladesh that dealt mainly with the changes in mangrove soil characteristics in both cultured and naturally inundated conditions. Some noticeable changes were observed in case of soil pH, sulfate sulfur(SO4-S) and extractable aluminium (Al) where, soil pH has shown a negative correlation with the other two parameters. Al concentration reached its minimum 145 days after pond preparation (DAP) proving that flooding for longer periods reduced the possibility of acid and Al toxicity. Extractable sodium (Na) and potassium (K) gradually increased in the cultured ponds while in the inundated ponds, Na concentration remained stable but K increased significantly at the end of the study period. Results of the present study indicate that shrimp farming in an already depleted mangrove forest helps to improve soil quality but still, other management and environmental concerns related to intensive shrimp culture are unavoidable and should be taken into account before promoting such activities in mangrove areas. It is recommended that shrimp culture zone be established beyond the mangrove fringe where possible, to enable mangroves to buffer aquaculture effluent.A study was carried out in three shrimp farms in a natural mangrove area at the southeastern part of Bangladesh that dealt mainly with the changes in mangrove soil characteristics in both cultured and naturally inundated conditions. Some noticeable changes were observed in case of soil pH, sulfate sulfur(SO4-S) and extractable aluminium (Al) where, soil pH has shown a negative correlation with the other two parameters. Al concentration reached its minimum 145 days after pond preparation (DAP) proving that flooding for longer periods reduced the possibility of acid and Al toxicity. Extractable sodium (Na) and potassium (K) gradually increased in the cultured ponds while in the inundated ponds, Na concentration remained stable but K increased significantly at the end of the study period. Results of the present study indicate that shrimp farming in an already depleted mangrove forest helps to improve soil quality but still, other management and environmental concerns related to intensive shrimp culture are unavoidable and should be taken into account before promoting such activities in mangrove areas. It is recommended that shrimp culture zone be established beyond the mangrove fringe where possible, to enable mangroves to buffer aquaculture effluent.

RELEVANCE OF A RAPID APPRAISAL APPROACH TO IDENTIFY LOCALLY AVAILABLE FEED INGREDIENTS TO SMALL-SCALE NILE TILAPIA (Oreochromis niloticus L.) AQUACULTURE

Applications of a rapid appraisal approach to identify locally available feed ingredients in feed formulation, production, and socio-economics of Nile tilapia aquaculture in Bangladesh are discussed. Three diets of 35%, 30%, and 25% crude protein were formulated using locally available ingredients, and their essential amino acid profiles were assessed for Nile tilapia. Six production scenarios were constructed using these diets and two culture periods of 100 and 150 days were considered. The production scenarios with 35% protein yielded the highest productivity and profitability over the 150-day culture period followed by the 30% protein scenario. Identification of locally available ingredients and their application in small-scale Nile tilapia aquaculture may lead to: (1) increased availability of inexpensive sources of fish production for poor people; (2) increased fish consumption; (3) increased self employment and involvement of women in productive activities; and (4) increased household income to reduce poverty.