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Reproductive Ecology of Mola (amblypharyngodon Mola)

A. S. M. M. HOQUE
Institute of Environmental Science, University of Rajshahi, Rajshahi 6205, Bangladesh

M. R. RAHMAN
Institute of Environmental Science, University of Rajshahi, Rajshahi 6205, Bangladesh

Abstract/ Executive Summary:

Reproductive cycle of mola (Amblypharyngodon mola) in a pond and in a beel along with some aspects of their physico-chemical parameters, morphometry etc. were carried out at Rajshahi. The highest (81.08%) average monthly percentage of ovigenous female Mola in pond was in September and lowest (20%) in November, whereas the highest (87.30%) and the lowest (28.57%) values in beel were found in May and in November respectively. Both the Gonado Somatic Index (GSI) and Gonadal Langth Index (GLI) of Mola showed two distinct peaks, one in May and another in September where GSI values were 19.51% and 22.48% and GLI values were 36.31% and 36.19% respectively. Similar peaks were found in the beel where GSI values were 20.98% and 18.72% and GLI values were 41.77% and 40.58% respectively. The lowest mean fecundity of Mola in pond was 1023+625 and the highest was 6806±125 in size groups of 5.0-5.5cm and 8.1-8.5cm respectively. Ova diameter of Mola in pond showed two distinct peaks one in May and another in September where ova diameter values were 30μm and 29μm respectively. Similar peaks were found in beel where OD values were 28μm and 27 μm respectively. Above result shows that Mola (A. mola) breeds twice a year with one peak in May and another in September in both pond and beel. Some ecological parameters were also observed in the study areas.

Keywords: Reproductive, Ecology, Fish, Amblypharyngodon mola

Location: Rajshahi

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Fish

Objectives:

To collect the information of Reproductive Ecology of a mola for better scientific management and conservation of this important fish species.

Methodology:

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 is situated at Mohonpur upazila of Rajshahi district. 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. The stocking of brood fish of Mola was done in August to September @ 100 per decimal. Agricultural bi-products such as rice-bran or wheat-bran (50%) and mustard oil cake (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. 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). 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. 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 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 of a diameter was measured according to Dan (1977).

Source of Information: J Agric Rural Dev 6(1&2), 165-174, June 2008 ISSN 1810-1860

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The above results showed that during the month from April to October the ovaries were matured and ripe in condition. Higher percentage of gravid females, maximum GLI & GSI, OD and fecundity values suggested that the reproductive cycle of Mola is from April to October with two peaks, one in May and other in September i.e., it breeds twice in a year in both closed and open water environment.

Knowledge Management: Journal