Study location and pond facilities The experiment was conducted in the experimental ponds situated on the north side of the department of Fisheries, University of Rajshahi for a period of 60days. The ponds were similar in shape, depth, basin configuration including water supply facilities. The average area of the ponds was 0.8 decimal (0.0032 hector). Pond preparation All unwanted fishes and other predatory species were completely removed through repeated netting from the ponds and finally applying rotenone at the rate 20mg/deci/feet water depth. After soaking overnight lime was applied at the rate of 1 kg/decimal. One week after liming, the pond was manured with cow dung minimum 0.5 kg/deci and maximum 11 kg/deci with a mean valve of 5.37 - 4.74 kg/deci.
Collection and Stocking of fry The hatchling of Catla catlamixed with some other species were collected from Padma river near the Rajshahi area and nursing 3 weeks in nursery pond. The rearing ponds were stocked with the separated fries of Catla catla after three weeks nursing for research purposes. The sizes of the stocked fires were 2.4±0.38 cm length and 0.60±0.04 g weight. Use of supplementary feeds Fries were fed three same type of supplemental feed for different treatment (T1, T2, and T3), such as Fish meal, rice bran, wheat bran and Mustard oil cake at the rate of 4-8% body weight daily. The proximate composition of each the feed were carried out in accordance with A.O.A.C method (1990) in table 3.
Design of the experiment Evaluation of fingerling production of catla in ponds, three treatments were used each with three replications.
Water Quality parameters Physico-chemical paremeters like water temperature (ºC), transparency (cm), dissolved oxygen (mg/l), Carbon dioxide (mg/l), NH3-N (mg/l), pH, alkalinity (mg/l) of each experiment pond were measured at 15 days interval and data were recorded on sampling dates. Temperature was recorded using a Celsius thermometer, transparency by secchi disc and other chemical parameters were using Hack kit box (FF2, USA). Recording of water quality data were taken between 8:00 am and 9:00 am.
Growth parameters The length gain (cm), weight gain (gm) and Survival rate was measured into the following formula used- ? Length gain (cm) = Average final length – Average initial length ? Weight gain (gm) = Average final weight – Average initial weight ? Survival rate = After completion of the experiment at 60th day the number of total live fingerlings in rearing pond was counted separately for calculation of survival rate-
Survival rate (%) = Number of fish at harvest / Total number of fish stocked x 100
? Yield (kg/deci): Yield was calculated by deducting biomass at stock from biomass at harvest and it was expressed as kg/deci.
? Specific growth rate (SGR, % bwd-1) Specific growth rate (SGR, % bwd-1) was calculated as-[Ln (final weight) – (initial weight)] / culture period (day) x 100 (Brown, 1957).
Statistical Analysis The length gain (cm), weight gain (g), Final length gain (cm), Final weight gain (g) and survival rate of fry during experimental period with same feeding & fertilization in different treatments were all tested using one way analysis of variance (ANOVA). Significant results (P<0.05) were further tested using Duncan’s New Multiple Range Test (DMRT) to identify significant differences among means. This statistical analysis was performed with the support of the computer software SPSS (Statistical package for social sciences) program.