Bangladesh]. Fish. Res., 12 (2), 2008: 129-134 Growth performance evaluation of genetically improved silver barb (Barbonymus gonionotus Bleeker) in different agro-ecological zones in Bangladesh A.H.M. Kohinoor*, M.S. Islam, M. Begum and M.G. Hussain Bangladesh Fisheries Research Institute Mymensingh 2201, Bangladesh *Corresponding au th or Abstract On farm trials of silver barb with other carps were carried out in 40 ponds during May to October 2005 in four agro-ecological zones viz., Trisha!, Muktagacha, Parbotipur and Paikgacha in Bangladesh. In Trisha! and Muktagacha zones, ponds were stocked with silver barb, silver carp and common carp at the stocking density of 11,500 fish/ha, whereas in Parbotipur and Paikgacha zones, ponds were stocked with silver barb, rohu, catla and mrigal at the stocking density of 10,000/ha. Among the ponds, 50% (20 ponds) were stocked with BFRI improved stock of silver barb (Treatment-I) and rest of the 20 ponds stocked with local silver barb stock (Treatment-2). The harvest weight of BFRI improved silver barb were 149±16.01, 168±18.06, 198±14 and 230±9.25g in Trisha!, Muktagacha, Paikgacha and Parbotipur, whereas the data obtained at 113±15.52, 136±20.66, 170±17.0 and 205±12.lOg for local stock of silver barb, respectively. In all trials, the harvest weight of BFRI improved stock showed significantly higher growth performance (P<0.05) over the local stocks. Key words: Genetically improved silver barb, agro-ecological zones Introduction Silver barb (B. gonionolus) is a popular species among fish farmers of Bangladesh because it grows faster and well on low protein diets, whether feeding on certain aquatic plants or given supplementary feeds and can tolerate a wide range of environmental conditions. In Bangladesh, breeding is mainly carried out by hypophysation. For aquaculture, the farmers mainly depend on hatcheries for fingerlings of silver barb. There is a possibility of inbreeding in most of the small hatcheries where female and male are chosen from closed populations of very limited size (Hussain and Islam 1999). Genetic deterioration of existing stocks of silver barb has been reported (Hussain and Mazid 2001). Genetic stock improvement through genetic selection is one of the most useful ways of enhancing desirable traits in a founder stock with high genetic variability to reduce inbreeding in a hatchery population (Eknath et al. 1998).