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Studies on Reproductive Ecology of Khalish Fish (colisa Fasciatus (bloch & Schneider)

M. R. Rahman
Institute of Environmental Science, University of Rajshahi, Rajshahi-6205

Abstract/ Executive Summary:

The regression coefficient of the body length-body weight relationship was n=2.45356, indicating that Colisa fasciatus exhibits allometric growth. Monthly variation in pH shows that maximum and minimum were 8.0 in May and 7.0 in December at pond, respectively while in beel it was recorded 8.0 in May and 7.0 in January. In pond, 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. The highest percentage of ovigenous female in pond was found 85.71% in May and the lowest (36.36%) in March. The highest (78.95%) value was recorded in May and the lowest (36.59%) in August in beel. The highest GLI (32.0%) in pond was observed in May and the lowest (7.41%) in December and the highest GSI (23.24%) was observed in May and the lowest (5.32%) in January. In beel the highest GSI (19.06%) was in May and the lowest (2.44%) in December and highest GLI (35.27%) was recorded in May and lowest (3.83%) in December. The lowest fecundity in pond was found 999±366 and the highest was 3218±521 in size groups of 5.0-5.5cm and 8.1-9.0 cm respectively. In beel the lowest fecundity was found 1001±350 and the highest was 3330 ± 210 in same size groups. Maximum ova diameter was observed 24mm in May and minimum 4mm in December in pond and maximum 65mm in May and minimum 6mm in January in beel. Some ecological and biological parameters were also observed in the pond and beel.

Keywords: Breeding, Biology, Ecology, Colisa fasciatus

Location: The Institute of Environmental Science, Laboratory, Rajshahi University, Bangladesh

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Fish

Objectives:

1. To carryout research on the biology with special reference to reproductive cycle of C. fasciatus in pond aimed at its better management and in beel for comparative study. An up to date account of the information on morphomatric and reproductive cycle of C. fasciatus is important in the study of biology of the fish as well as to compare with the variation in the reproductive cycle of different environment.

Methodology:

Colisa fasciatus sampling was conducted weekly basis in pond (closed water) and beels (open water). The pond area was 0.20 hectare with an average depth of 1.5m. The pond was free from aquatic vegetation. It is completely separate and well exposed to sunlight and had no inlet and outlet facilities but had facilities to get supply of water from a deep-tubewell. The samples were taken during day time, ad brought to the Institute of Environmental Science, Laboratory, Rajshahi University, Bangladesh. The beel chandi, which is a natural depression situated at Mohonpur upazilla of Rajshahi district and its area is about 13 hectare. The beel was partially covered with aquatic vegetation. It is connected with a canal. During rainy season it was inundated then its area was expended to 500 hectare. Ponds: The ponds were newly constructed in clay soil with a pH of 7.0. The ponds were excavated to a depth of 1.5m. One pond at each site was provided with an adjacent elevated area, called a breeding ground. On the breeding growth of vegetation was allowed. All ponds were provided with a 5cm layer of topsoil spread on the newly excavated bottom in order to assist productivity. Each pond was prepared by applying 250kg/ha of quick lime (CaO). Three days after liming organic manure (cow dung) was spread on the bottom at a rate of 1000kg/ha. Then the pond was filled with water from the shallow tubewell. Inorganic fertilizer made up of two parts one part was TSP (Triple Super Phosphate) and another part urea was applied at a rate of 50kg/ha. The water turned greenish in colour one week after filling. Stocking of fish and feeding: Stocking took place at the end of July, seven to ten days after the ponds were filled. The stocking of brood fish of C. fasciatus were done 200/decimal. Feed and fertilizer were applied at the same rate in all ponds. Apart from the enhanced natural food, supplemental food was given in each pond. Fish food was selected from locally available agricultural by-products such as mustard oil cake (40%) and rice barn from automatic mills (60%). The feeding rate was 2-3% /day of estimated body weight of fish stock. The fish stock was reassessed weekly by sampling. Fertilizer was applied at the same rate in all the ponds, with small variations in order to maintain a water transparency of 25-30cm, measured daily with a Secchi disk. The rate of fertilizer applied was 2.0kg/ha/day. The type of fertilizer used was urea and TSP in the ratio of 1:2. Water sample collection and water analysis: On the spot, water quality parameters were recorded between 8.30 and 9.30am at weekly interval from experimental pond and Chandi beel. The water quality parameters (pH, NH4, and DO) were determined by using Spectrophotometer (HACH DR 2000) and Fish Farming Test Kit Box (HACH, FF- 1A, USA). Fish sample collection: Fishing was done during daytime (10:00-17:00 hours) using traditional basket traps fabricated from bamboo and funnel bag nets locally known as Srutijal. These basket traps are rectangular in shape measuring 1.0^0.3^0.5m and fabricated from small narrow bamboo sticks interwoven with iron wire. 100 specimens of C. fasciatus were randomly undertaken for further investigation at weekly interval both from the pond and the beel. Specimen sampled were immediately chilled in ice on board and fixed with 10% formalin in the laboratory. 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 labeled vials for subsequent study. Morphometric study: All specimens were sexed by gonad observation under a binocular microscope; the sex-ratio was statistically tested for deviance from the expected 1:1 ratio by a chi-square test. Body length (from the tip of the snout to the caudal fin) was measured to nearest millimeter and body weight was measured to the nearest gram. Both total length (TL) and fork length (FL) were measured with a slide caliper to the nearest 0.01cm while body weight (BW) was determined using a digital electric balance (Shimadzu, EB-430DW) to the nearest 0.01g. All the measurements were taken with the help of mm scale attached against the wooden board. 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. Body length and body weight relationship was estimated by the least square method. 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: All the specimens collected were sexed. Only female specimens were examined in the present study. The specimens were examined by naked eye or under microscope for the presence or absence of ova. Whole ovaries were removed from each female and were taken weight to 0.001g accuracy. Ova diameter was measured. Data were collected for gravid females for calculation of percentage of the gravid females against time following Farmer, (1974). The Gonado Somatic Index (GSI) and Gonado Length Index (GLI) were calculated which combines visual examination of the ovaries fixed with 10% formalin and measurement of oocyte diameter was used in this study. According to this method, ovarian maturity stages were classified into four categories: stage I (undeveloped), stage II (developing), stage III (developed) and stage IV (ripe). Dissected ovaries were stained with alcoholic eosin solution and after fixation and mounted in Canada balsam following the routine procedures of deparaffinization and dehydration. For the estimation of fecundity: The total number of eggs in each ovary sub-sample was counted to estimate the number of eggs (F) of the ovary using the proportion, F = (Gonad weight ^ number of eggs in the sub-sample)/sub-sample weight. Individual female fecundity (Fe) was calculated from the mean of the three fecundities (F1, F2, F3). The relationships between Fe and morphometric measurements (TL, BW) were determined by the equations Fe = aTL^b and Fe = aBW^b, based on the natural logarithms transformed equations, ln Fe = lna+blnTL and ln Fe = lna+blnBW respectively, where a and b are constant parameters in the linear regression analysis.

Source of Information: J. Environ. Sci. & Natural Resources, 3(1): 31-38, 2009; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Result shows that C. fasciatus (Bloch & Schneider) breeds once a year with one peak in April, May, June the ovaries were matured and ripe in condition. Higher percentage of gravid females, maximum GLI and GSI, OD and fecundity values suggested that the reproductive cycle of C. fasciatus (Bloch & Schneider) in April, May and June i.e., it breeds one in a year in both closed and open water environment. In conclusion, this study has provided basic information on breeding eco-biology that would be useful for fishery biologists, fish farm manager and fish farmer to impose adequate regulations for sustainable fishery management in the ponds and beels areas of Bangladesh.

Knowledge Management: Journal