Relationships of chemical composition, quantity of milt to fertility and hatchability of Clarias gariepinus (Burchell, 1822).

摘要

The biochemical composition of milt and the effect of its varying quantity on fertility and hatchability of Clarias gariepinus (African catfish) eggs were investigated. The study aimed at determining the right quantity of milt that can be used to fertilize certain quantity of eggs. The study further examined the effect of varying volume of milt on the water quality during the incubation of C. gariepinus eggs in order to provide baseline information on chemical composition, which can be used as a basis for sperm-mediated gene transfer. Result obtained from this study showed that 0,035ml of milt gave the best hatchability 2041±90.9, while 0.175ml of milt gave the least hatchability 1341± 384.2 .There was a positive significant correlation between the quantity of milt used and hatchability (P< 0.05) and there was a significant difference among the treatments and within the hour of the experiment (P< 0.05). The investigation revealed that the quantity of milt used for artificial reproduction in fish significantly affect water quality used for incubation (P <0.05). The higher the quantity of milt, the lower the Dissolved Oxygen (DO) level, there was equally a buildup of pollutants as the quantity of milt increased. Biochemical analysis of milt showed that glucose at a concentration of 8585±6.05mg/l is the major organic substance that supplies the spermatozoa with energy. Sodium and chloride are the major electrolytes with 113:7±0.88 mg/l and 100± 1.73mg/l respectively and the pH of the milt was 6.2±0.17mg/l. The albumin content was low, with a mean value of 1.3±0.9mg/l. The glucose level was high having a mean value of 85.0±6.08mg/l and the cholesterol level was equally high with a mean value of 188.0± 13.67mg/l. The triglyceride content of the milt was high having a value of 202±19.88mg/l. The highdensity lipoprotein cholesterol was low, with a mean value of 13± 6.01 when compared with the low density lipoprotein cholesterol which had a mean value of 134 ± 11.37. There was low motility of sperm in fish milt which may be due to a number of factors ranging from exposure to light, to low pH and aerobic breakdown of glucose to supply energy for the spermatozoan (which is very low).