Wind Turbine Generators

INTRODUCTION
Reproductive Ecology of any fish is essential for assessing commercial potentialities of its stock, life history, culture practice and actual management of its fishery (Lagler, 1956). Reproductive potential of a population is one of the basic exigencies to designate the individuals of that population in respect to their gonadal conditions. In order to make success in fish culture, it is important to assess the yearly breeding cycle of culturable fishes. Spawning of fish occurs during a particular phase of the reproductive cycle. Some of them breed once annually while others at regular intervals throughout the year. Knowledge of gonadal development and the spawning season of a species allow subsequent studies on spawning frequency of its population, which is important for its management. A thorough understanding of the early development of a fish species is also considered an important step for the fish calturists. Very little works has been done in such direction in this country. Few works deserve worth mentioning viz., Afroze and Hossain (1990), Hossain et al. (1991), Nargis and Hossain (1992) and Parween et al. (1993).
Survey of available literature reveal that works on the fecundity of different fishes have been done in this country by many researchers like Miah and Dewan (1984), Afroze end Hossain (1990)., Faruq et al. (1996), Kabir et al. (1998), Wahab et al. 2003, Kohinoor (2000), Kohinoor et al. (2003), Mazid and Kohinoor (2003). In view of economic importance and food value of this fish it is very important to collect the information of Reproductive Ecology of A. mola for better scientific management and conservation of this important fish species. Keeping this in mind the present study has been undertaken

MATERIALS AND METHODS

Durations and study area
The experiment was undertaken in one pond (closed water) and in one beel (open water) at Rajshahi. The pond is located at the Govt. Fish seed Multiplication Farm (FSMF) of Directorate of Fisheries, Matshya Bhaban, Rajshahi. The beel Chandi, a natural depression was situated at Mohonpur upazila of Rajshahi district.

Preparation of pond
Pond was dried out and embankment was repaired. The lime was applied and fertilized with cowdung, urea and T.S.P. Then it was filled-up with water from deep tube well.
Stocking of fish and feeding

The stocking of brood fish of Mola was done in August to September @ 100 per decimal. Agricultural bi-products such as rice-bran or wheet-bran (50%) and mustard oilcake (50%) were used as supplementary feed at the rate of 3% of body weight, twice a day. The pond was also fertilized with cowdung at the rate of 4 kg/decimal at 15 days interval.
Water sample collection and water analysis

On the spot, water quality parameters were recorded between 8.30 and 9.30 am at monthly interval from experimental pond (FSMF pond) and Chandi beel. The water quality parameters (NH4, NH3, CO2, NaCl, Cl, DO and CaCo3) were determined by using Spectrophotometer (HACH DR 2000) and Fish Farming Test Kit Box (HACH, FF-1A, USA).

Fish sample collection
33 specimens of A. mola were randomly undertaken for further investigation at monthly interval both from the pond and the beel. Morphometric study was done of individual fishes. Then the ovary of each fish was taken out very carefully and preserved in 10% buffered formalin in labelled vials for subsequent study.
Morphometric study
All the measurements were taken with the help of mm scale attached against the wooden board. The weight (in grams) of the fishes was taken by fine electric balance. Before weighing, the specimen was washed with water and left exposed to air and the excess of moisture was dried off with the help of a blotting paper for taking accurate weight.
Length of the ovary was taken with the help of a fine point divider by using an mm scale. General feature and structure as well as month wise size shape and color of gonads of the experimental fish were studied during sample collection and preservation.
Methods for determining the reproductive cycle of A. mola
Data were collected for gravid females for calculation of percentage of the gravid females against time following Farmer (1974). The Gonado Somatic Index (GSI), Gonado Length Index (GLI) and fecundity were calculated according to the formula given by Lagler (1956). The weight of a spent gonad were measured with the help of an electric balance Model no. (FX-300) Dissected ovaries were stained with alcoholic eosin solution and after fixation and mounted in Canada balsam following the routine procedures of deparaffinization and dehydration.
A total of 109 matured fish were examined from the pond and 125 from the beel.

Ova diameter (OD)
Ova diameter was measured according to Dan (1977).
RESULTS AND DISCUSSION
Chemical parameters of water
pH
The maximum and minimum pH in pond were 8.0 in May and 7.0 in December, respectively while in beel it was recorded as 8.0 in May and 7.0 in January.
DO
The highest DO (7.5 mg/l) was recorded in December and the lowest DO (3.9 mg/l) was recorded in July in pond. In case of beel the highest (10 mg/l) was recorded in December and the lowest (5 mg/l) was recorded in July.
In the rainy season, particularly from May to July the water temperature was relatively high and rainfall was also high. Physico-chemical parameters of water in pond and beel are shown in Table 1
Table 1. Water quality parameters of the experimental pond and beel for two years

Shariful Islam
oceanwabe@gmail.com
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