Comparative study of piscine and non-piscine pituitary extract and ovulin for inducing spawning in catfish ( Clarias gariepinus )

摘要

The study examined the effect of synthetic hormone (Ovulin), piscine hormone (Clarias gariepinus), pituitary extract and non-piscine; frog (Haplobutrachus occipitalis) pituitary extracts. The study was carried out in the Department of Marine Sciences, University of Lagos, Lagos state Nigeria. The broodstocks (Clarias gariepinus) were purchased from a private fish farm at Bariga in Lagos state and were transported in plastic can containing water. The temperature of the water was reducing by addition of ice block which helped to minimize stress on the fish. Hatchery raised 12 months gravid broodstocks were selected. All broodstocks were selected by external morphological characteristics. Female fish were selected on the basis of ovarian biopsy. The study lasted 65 days. Twelve gravid female and twelve mature male of C. gariepinus with body weight range of 500g to 1100g were used. The spawn weight was determined by estimating the mean weight of eggs used to achieve percent (%) fertilization. The ovulation rate was estimated from the weight of eggs released as a percentage of the total weight of the ovary. The percent fertilization was estimated from the surviving embryos 10 hours after fertilization. The percent (%) hatching was the number of hatched fry relative to the fertilized eggs, while the percent (%) survival was the number of surviving fry after 14 days of feeding with mixed artemia and artificial diets. The result showed that ovulin performed significantly better (p< 0.05) in all the parameters investigated. The randomized analysis of Variance (ANOVA) for the parameters investigated in the three hormonal materials shows percentage fertilization of 67.00±3.61%, 60.70±4.49% and 56.25±5.44%, percentage hatchability of 90.61±6.43%, 60.70±4.50%, and 56.26±5.46% and 69.33±5.13%, 61.67±10.41% and47.67±2.52% of survival rate were recorded for ovulin, fish pituitary and frog pituitary, respectively. Comparative cost benefit analysis shows that ovulin, which recorded better results was higher in terms of cost effectiveness compare to fish pituitary and especially that of frog which is both cheaper and available in our environment. Although for ease of handling and better result in terms of hatchability, fertilization and survival rate ovulin is highly recommended to hatchery users.