Reproductive Biology and Biochemical Composition of Cyprinus Carpio Var. Specularis (Lacepede, 1803) in Atrai River of Northwestern Bangladesh

Abstract

The study focused on physico-chemical conditions, reproductive biology and biochemical composition of Cyprinus carpio var. specularis (Mirror carp) for a period of 24 months (July, 2013 to June, 2015) in the Atrai river of northwestern (Naogaon district) Bangladesh. The physico-chemical conditions of the river Atrai exhibited more or less variations according to the change of months and seasons. In the study area four physical and three chemical parameters have been considered. The two years mean values of these parameters were recorded as air temperature 28.24C, water temperature 26.81C, water transparency 0.45 m, rainfall 122.24 mm, pH 7.91, dissolved oxygen 6.21 mg/l and free carbon dioxide 7.00 mg/l. So, the water body was suitable condition for fishes in the study area. The male and female reproductive systems were also observed. The ovaries were classified in ten stages as Immature, maturing-I (early developing), maturing-II (late developing), mature, ripe, pre-spawning, spawning, post spawning, spent and resting stages. The ova were also divided into four stages on the basis of ova diameter and coloration as immature stage (0.22 to 0.32 mm, whitish), maturing stage (0.28 to 0.69 mm, light yellow), mature stage (0.64 to 1.15 mm, yellow) and ripe stage (0.99 to 1.98 mm, Deep yellow). The mean ova diameter ranged from 0.260.03 to 1.260.15 mm. The minimum and maximum GLI and GSI were obtained from 20.893.83 to 38.325.62 and 0.360.14 to 8.346.18 respectively. The spawning time extended from November to April with the peak in February. The fecundity ranged from 5928.91 to 209120.18 with the mean of 87377.9879544.17 which revealed that the species was high fecund. A comparison of correlation co-efficient relation between fecundity with total length (r = 0.9129), standard length (r = 0.9319), total weight (r = 0.9519) gonadal length (r = 0.9121) and gonadal weight (r = 0.9948) were established. All the relationships were highly significant. The sex ratio of 1084 specimens collected during 24 months of study has been determined. The total male (512) and female (572) ratio was 1:1.12. Females were prominent in natural population of the fish. In the present investigation of biochemical composition was carried out for 12 months (January, 2014 to December, 2014). The percentage of moisture (M 72.540.551 to 74.531.078 and F 73.320.778 to 75.420.538%), ash (M 3.020.637 to 3.440.536 and F 2.640.393 to 3.770.766%), lipid (M 3.360.400 to 4.190.231 and F 2.950.349 to 4.080.400%), protein (M 18.251.189 to 20.070.190 and F 17.030.925 to 19.560.538%) and carbohydrate (M 0.0350.002 to 0.0420.005 and F 0.0370.004 to 0.0420.003%) respectively. An increasing trend of moisture, ash and carbohydrate were found in both males and females in winter season. Whereas lipid and protein content showed a decreasing trend in both sexes in winter season (winter season was spawning period of this fish). In case of male protein and lipid content was higher than female fishes in all seasons. The results indicate variation in biochemical composition on the basis of sex and season.