Development Of Nursery Technology Of Freshwater Prawn (Macrobrachium Rosenbergii) PL

Abstract

Reports on nursery technology of freshwater prawn are scanty. Prawn culture is an important production venture in the southwest of the country. The rate of prawn production is low and the causes of which is mainly attributed to the lack of timely available good quality seed. There are reports on drastic reduction of natural sources of seed supply and now hatchery-produced PL are meeting the greater part of the demand. The hatchery produced seed are not as strong as the natural ones and suffer from heavy mortality in the stocking ponds. There is no proven nursery technology in Bangladesh. The present study was conducted during June to December, 2006 with a view to developing a nursery technology with respect to optimization of stocking density and survivability of prawn PL in earthen ponds. Hatchery obtained PL were reared with commercial nursery feed and monitoring of water quality for 14 weeks in 12 ponds (l.25dec each) at Khulna University. Four densities viz., 500, 800, 1000 and 958 PL/dec. were used with three replicates in each. The range of temperature, DO, pH, alkalinity, hardness, ammonia and phosphate during the study were within the acceptable limit. The mean initial weight of prawn PL was 0.005g. Net gains in weight were 2.069, 4.042, 2.680, and 1.707g from the four treatments, respectively. The mean values of specific growth rate of the PL were 3.192,3.550,3.332 and 3.090% per day from the four densities, respectively. Highest values of growth rate and survival rate were found in 500PLldec density. Second highest values of growth rate and survivability were found in 800PL/dec. However, a density of 500-800 PL/dec may be used for better growth and survivability in the prawn nurseries, though there are scopes for further improvement of the process through feeding trial and/or other aspects.