Abstract:The occurrence and abundance of cyanobacterial population was monitored monthly in two urban fish ponds in Rajshahi City Corporation area from January to December, 2006. The bloom was observed in March, August and September. Some environmental parameters such as water temperature, transparency, pH, Dissolved Oxygen(DO), free Carbon dioxide(CO 2 ), Biological Oxygen Demand (BOD), NO 2 -N, NH 3-N, NH 4 + , toxic ammonia, Oxidation reduction Index (rH 2 ) were recorded and their relationship with the bloom formation by cyanobacteria are discussed. During the study period 23 species of cyanobacteria were identified. Among which Microcystis, Anabaena, Planktothrix were found to be the dominant genera. Microcystis aeruginosa was the most dominant species during the bloom period. At the peak bloom period, Microcystis aeruginosa comprised 81.64% and 83.24% of total cyanophyceae in pond-1 and pond-2, respectively. The initiation and persistence of natural bloom of cyanobacteria, especially Microcystis was found to be triggered by relatively high temperature (33.21-33.53 o C), alkaline pH (8.8), and nutrient enrichment especially high NO 2 -N, NH 3 -N, and NH 4 + concentration.

The present study reports the first complete and inclusive description of some biological parameters including lengthfrequency distribution (LFD), sex ratio (SR), length-weight relationship (LWR), condition factors (allometric,K

Rice-fish-vegetable culture is vital for the proper utilization of limited land resources as sustainable production of the fish protein with additional income and employment generation (Jamu and Costa-Pierce, 1995). The introduction of fish into the rice fields in a ARTICLE INFO

(Pond-4) respectively. This study indicated that the Pond-2 covered by garbage, polythene and other wastes, Pond-3 and Pond-4 received industrial wastes were moderately polluted whereas the Pond-1 received City corporation wastes was less polluted.

An experiment was carried out to evaluate the growth performance of carp polyculture system supplemented with different levels of supplementary feed. To undertake this investigation, two earthen ponds were stocked with 25% Labeo rohita, 25% Catla catla, 20% Labeo calbasu, 20% Ctenopharyngodon idella and 10% Hypopthalmichthys molitrix with a total stocking density of 10000/ha. The net fish production was found to be 2,166 and 3,874 kg/ha/yr in pond-01 and pond-02, respectively. The total cost of fish farming of pond-01 and pond-02 were 64,268 BDT and 88,568 BDT per ha. The total return of pond-01and pond-02 were BDT 1,04,280 BDT and 1,69,250 BDT per ha. Net benefit from pond-01 and pond-02 was 40,312 BDT and 80,682 BDT respectively. Net profit margin of pond-01 and pond-02 was 62.73% and 91.10%. And finally the benefit cost ratios (CBR) were found to be 0.62:1 and 0.91:1 in pond-01 and pond-02, respectively. Asiat. Soc. Bangladesh, Sci. 42(2): 229-234, December 2016