RICE-FISH CULTURE - FEEDING, GROWTH AND YIELD OF 2 SIZE CLASSES OF PUNTIUS-GONIONOTUS BLEEKER AND OREOCHROMIS SPP. IN BANGLADESH

Concurrent rice-fish culture experiments were conducted in Bangladesh to compare and evaluate the feeding, growth, condition factor, surviva l and yields of two sizes of silver barb (Puntius gonionotus) and tila pia (Oreochromis spp.) in 1994 and 1995, respectively, and to compare paddy yield and ecological conditions between rice-fish and rice-alone situations. Survival, specific growth rate, condition factor and yiel ds were better with the small-sized (5.6-6.1 cm) P. gonionotus than th e larger-sized (8.8-9.6 cm) P. gonionotus and either sizes (4.0-7.5 an d 9.5-14.7 cm) of Oreochromis spp. P. gonionotus was found to be a mac rophy-tophagous column feeder with benthic foraging habit on tiny moll uscs. There was clear evidence of its foraging on paddy grains. Conver sely, Oreochromis spp. was found to be a detritivorous browser or surf ace grazer. Ontogenetic shifts in diet were pronounced in P. gonionotu s while absent in Oreochromis spp. Best mean net fish yield was 271.03 kg ha(-1) crop(-1) with small P. gonionotus in 78 days culture, signi ficantly higher than with Oreochromis spp. (P < 0.05). Paddy yields we re 1.5-3.7 t ha(-1) crop(-1) in rice-fish and 1.5-1.8 t ha(-1) crop(-1 ) in rice-alone culture with insignificant differences between the yea rs (P > 0.05). Water quality parameters were, in general, within the a cceptable range for aquaculture. Small sizes of P. gonionotus should b e preferred over the Oreochromis spp. for the integration of rice-fish nursery systems but further work should be done on the dietary import ance of rice grains to P. gonionotus. (C) 1997 Elsevier Science B.V.