Biometric characteristics and some biological features of natural hybrids between Nile tilapia Oreochromis niloticus and blue tilapia Oreochromis aureus in Lake Edku, Egypt
Shnoudy A. Bakhoum
aqua, International Journal of Ichthyology, pp. 191-204, Volume 15, Issue 4 – 15 October 2009
Oreochromis niloticus, O. aureus and specimens with an external appearance intermediate between these putative parents were sampled from Lake Edku and examined to determine the hybrid nature of the intermediate specimens. The results of hybrid index, principal component analysis, discriminant function analysis and the Mann-Whitney U-test indicated the hybrid nature of these specimens and determined the most suitable biometric characters to distinguish different hybrid types from the parent species. Hybrid specimens represented about 28% of the total catch of Lake Edku. Hybrids have a higher percentage of males than females. Hybrids become mature at a smaller size and their reproductive activity is lower than that of the parent species. The natural mortality of hybrids is higher than that of the parent species.
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