| INTRODUCTION | | | | Chandi beel. The water quality parameters (NH4, |
| Reproductive Ecology of any fish is essential for | | | | NH3, CO2, NaCl, Cl, DO and CaCo3) were |
| assessing commercial potentialities of its stock, life | | | | determined by using Spectrophotometer (HACH |
| history, culture practice and actual management | | | | DR 2000) and Fish Farming Test Kit Box (HACH, |
| of its fishery (Lagler, 1956). Reproductive potential | | | | FF-1A, USA). |
| of a population is one of the basic exigencies to | | | | Fish sample collection |
| designate the individuals of that population in | | | | 33 specimens of A. mola were randomly |
| respect to their gonadal conditions. In order to | | | | undertaken for further investigation at monthly |
| make success in fish culture, it is important to | | | | interval both from the pond and the beel. |
| assess the yearly breeding cycle of culturable | | | | Morphometric study was done of individual fishes. |
| fishes. Spawning of fish occurs during a particular | | | | Then the ovary of each fish was taken out very |
| phase of the reproductive cycle. Some of them | | | | carefully and preserved in 10% buffered formalin |
| breed once annually while others at regular | | | | in labelled vials for subsequent study. |
| intervals throughout the year. Knowledge of | | | | Morphometric study |
| gonadal development and the spawning season of | | | | All the measurements were taken with the help |
| a species allow subsequent studies on spawning | | | | of mm scale attached against the wooden board. |
| frequency of its population, which is important for | | | | The weight (in grams) of the fishes was taken by |
| its management. A thorough understanding of the | | | | fine electric balance. Before weighing, the |
| early development of a fish species is also | | | | specimen was washed with water and left |
| considered an important step for the fish | | | | exposed to air and the excess of moisture was |
| calturists. Very little works has been done in such | | | | dried off with the help of a blotting paper for |
| direction in this country. Few works deserve | | | | taking accurate weight. |
| worth mentioning viz., Afroze and Hossain (1990), | | | | Length of the ovary was taken with the help of a |
| Hossain et al. (1991), Nargis and Hossain (1992) | | | | fine point divider by using an mm scale. General |
| and Parween et al. (1993). | | | | feature and structure as well as month wise size |
| Survey of available literature reveal that works on | | | | shape and color of gonads of the experimental |
| the fecundity of different fishes have been done | | | | fish were studied during sample collection and |
| in this country by many researchers like Miah and | | | | preservation. |
| Dewan (1984), Afroze end Hossain (1990)., Faruq | | | | Methods for determining the reproductive cycle of |
| et al. (1996), Kabir et al. (1998), Wahab et al. | | | | A. mola |
| 2003, Kohinoor (2000), Kohinoor et al. (2003), | | | | Data were collected for gravid females for |
| Mazid and Kohinoor (2003). In view of economic | | | | calculation of percentage of the gravid females |
| importance and food value of this fish it is very | | | | against time following Farmer (1974). The Gonado |
| important to collect the information of | | | | Somatic Index (GSI), Gonado Length Index (GLI) |
| Reproductive Ecology of A. mola for better | | | | and fecundity were calculated according to the |
| scientific management and conservation of this | | | | formula given by Lagler (1956). The weight of a |
| important fish species. Keeping this in mind the | | | | spent gonad were measured with the help of an |
| present study has been undertaken | | | | electric balance Model no. (FX-300) Dissected |
| MATERIALS AND METHODS | | | | ovaries were stained with alcoholic eosin solution |
| Durations and study area | | | | and after fixation and mounted in Canada balsam |
| The experiment was undertaken in one pond | | | | following the routine procedures of |
| (closed water) and in one beel (open water) at | | | | deparaffinization and dehydration. |
| Rajshahi. The pond is located at the Govt. Fish | | | | A total of 109 matured fish were examined from |
| seed Multiplication Farm (FSMF) of Directorate of | | | | the pond and 125 from the beel. |
| Fisheries, Matshya Bhaban, Rajshahi. The beel | | | | Ova diameter (OD) |
| Chandi, a natural depression was situated at | | | | Ova diameter was measured according to Dan |
| Mohonpur upazila of Rajshahi district. | | | | (1977). |
| Preparation of pond | | | | RESULTS AND DISCUSSION |
| Pond was dried out and embankment was | | | | Chemical parameters of waterpH |
| repaired. The lime was applied and fertilized with | | | | The maximum and minimum pH in pond were 8.0 |
| cowdung, urea and T.S.P. Then it was filled-up with | | | | in May and 7.0 in December, respectively while in |
| water from deep tube well. | | | | beel it was recorded as 8.0 in May and 7.0 in |
| Stocking of fish and feeding | | | | January. |
| The stocking of brood fish of Mola was done in | | | | DO |
| August to September @ 100 per decimal. | | | | The highest DO (7.5 mg/l) was recorded in |
| Agricultural bi-products such as rice-bran or | | | | December and the lowest DO (3.9 mg/l) was |
| wheet-bran (50%) and mustard oilcake (50%) | | | | recorded in July in pond. In case of beel the |
| were used as supplementary feed at the rate of | | | | highest (10 mg/l) was recorded in December and |
| 3% of body weight, twice a day. The pond was | | | | the lowest (5 mg/l) was recorded in July. |
| also fertilized with cowdung at the rate of 4 kg | | | | In the rainy season, particularly from May to July |
| decimal at 15 days interval. | | | | the water temperature was relatively high and |
| Water sample collection and water analysis | | | | rainfall was also high. Physico-chemical parameters |
| On the spot, water quality parameters were | | | | of water in pond and beel are shown in Table 1 |
| recorded between 8.30 and 9.30 am at monthly | | | | Table 1. |
| interval from experimental pond (FSMF pond) and | | | | |