Effects of Hydrogeographical Origin on Zootechnical Parameters of Wild Populations of Oreochromis niloticus (Linnaeus, 1758)

Abstract

Abstract:The effect of geographical origin on the zootechnical parameters of tilapias is very poorly documented, unlike production systems and farming methods. In this study, the growth and survival characteristics of Oreochromis niloticus individuals were analyzed in relation with their waterway of origin, sex and age at experimental fishing. Durung the rearing, the duplicate groups were constituted keeping the 2 sexes (male vs female) separately. Fingerlings were fed using a granulated commercial fish feed (35% of proteins; 3 mm in diameter). Apart from chlorophyll «a», 3 phytoplankton and 5 zooplankton species were also available in the rearing tank. The body weight, total length, standard length, average weight gain, nutritive quotient and survival rate were similar (p>0.05) between lake Toho and Couffo river but weaker at these two waterways than Ouémé river (p<0.05). The ponderal and linear specific growth rates were significantly identical between lake Toho and Couffo river but more important (p<0.001) in these two waterways than Ouémé river. The majority of the individuals indicated an allometric growth (b<3), which is less desirable in fish farming. In short, 2 populations were identified: the group constituted by Ouémé river and the one including lake Toho and Couffo river. It appears important to lead actions (selective breeding, crossbreeding) to improve the zootechnical performances of these local populations in order to promote their aquaculture.

Comparative analysis of Oreochromis niloticus and a putative hybrid (Wesafu): A Search for morphometric identity

“…This is because of high level of similarity due perhaps to the production of fertile hybrids from inter-specific spawning [15]. However, samples analyzed in this study present a range of metric and meristic characters which fits into some specific range reported for Oreochromis niloticus and Copton guineensis (16,17,18,19,20]. The present morphometric analysis of an 'ecotype' tilapia hybrid called 'Wesafu' and O. niloticus from Epe Lagoon and New Calabr Rivers, respctvely revealed high variability between the two and the morphometric measurements in Wesafu were not intermediate contrary to expectations.…”

“…The range, mean, standard error, median and mode of the meristic characteristics for the putative hybrid, Weasfu and O. niloticus are presented in Table2. In case of dorsal fin spines(14)(15)(16)(17), dorsal fin soft rays(12)(13)(14)(15)(16), pectoral fin soft rays(12)(13)(14)(15)(16), pelvic fin spines (1), and caudal fin rays(14)(15)(16)(17)(18)(19)(20)(21) in O. niloticus. The same measurements were recorded respectively as 16-18, 11-15, 12-15, 1 and 11-19 in the putative hybrid.…”