ISSN:
1365-2109
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
In order to obtain an appropriate and reliable method for the mass production of Clarias gariepinus (Burchell) fingerlings. experiments on artificial reproduction and pond rearing were carried out in the Republic of Congo in 1987-1991. Reproduction could be induced throughout the year using common carp pituitaries (3 mg kg−1 female). The average relative fecundity of females varied between 1.3%± 0.3 (SEM) and 14.3%±1.3 (SEM). The average hatching percentage of the eggs varied between 28.4%± 4.5 (SEM) and 59.1%± 3.7 (SEM) respectively, in the dry and rainy season. The fluctuation of the relative fecundity as well as the fluctuation of the hatching percentage follows the seasonal fluctuation in rainfall and temperature. The use of a net cage made of mosquito netting (1 m3, 0.5 mm mesh size) and the roots of water hyacinth (E. crassipes) as an egg incubator proved to be reliable. In ponds not protected against frogs an average of 5.0 ± 2.9 (SEM) fingerlings m−2 per 40 days cycle were obtained, whereas in ponds completely surrounded by a wall of aluminium roof plates (0.8 m high) the average production was 32.3 ± 3.3 (SEM) fingerlings nr- per 40 days cycle, when they are stocked with approximately 100 larvae m−2. Increasing the larval stocking density or extending the rearing period did not improve the final production. The main causes of low production in unprotected ponds are competition for food resources due to the presence of phytophagous frog larvae and cannibalism among the fingerlings of Clarias gariepinus. An analysis showed that the system is labour orientated, technically reliable and economically feasible when the fingerlings can be sold for USS 0.07 apiece.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2109.1995.tb00908.x
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