Performances of Bottom Dwelling Carpsin Polyculture Ponds under Drought Prone Barind Area of Bangladesh

Importance of pond based carp polyculture as a popular technique for fish production in Bangladesh is well documented [1]. It has further potentials to improve the livelihood of the poor and marginal peoples [2]. Potentials of pond based fish production towards livelihood improvement are also explored well by Hossain et al. [3] for Barind area having characteristic soil-water qualities like lower pH and organic matter content in soil along with lower alkalinity and higher turbidity level in pond water [4]. Apart from these potentials of pond polyculture and constraints for fish production associated with soil-water qualities, promotion of aquaculture is found to be affected by climate change aspects. Studies indicate that climate change may result in decline of groundwater level [5] and thus remodelling of carp polyculture is felt necessary in terms of insufficient water level in ponds under drought prone area. Fish production in polyculture is largely affected by species combination, stocking density, pond fertilization, supplementary feeds as well as ecological conditions. Stocking of comparatively larger size of carps can solve the problem of fish production for lower water column in polyculture ponds under drought prone area [2]. However all species do not play equal role in terms of water quality and fish production. The knowledge of fish-fish and fish-environment relationships enables choosing adequate combinations of fish species, stocking rates, input types and rates, and other management decisions according to the specific local conditions; climate, quality of water supply and pond fertility, availability of fish fry and fingerlings, availability of feeds and fertilizers, and market requirements [6]. Polyculture is the system in which fast growing compatible species of different feeding habits are stocked in different proportions in the same ponds Chakraborty et al., 2005. The bottom dwelling carps help re-suspension of bottom nutrients to water while stirring the bottom mud in search of food. Such an exercise of bottom dwellers also aerates the bottom sediment. Techniques to mitigate the low alkalinity and high turbidity problems are found to be addressed well but guidelines are not found for selecting appropriate bottom dwelling species for profitable carp polyculture in ponds under drought prone area. This study evaluated the performances of bottom dwelling species in carp polyculture ponds under Barind area of northern Bangladesh. The specific objectives of this study were to monitor the water quality and fish growth; to evaluate the yield and economics of carp polyculture; and thereby to recommend best performing species combination for profitable carp polyculture in ponds under drought prone Barind area.