A Comparative Ecological Approach of the Length–Weight Relationships and Condition Factor of Sarotherodon Melanotheron Rüppell, 1852 and Tilapia Guineensis (Bleeker 1862) in Lakes Nokoué and Ahémé (Bénin, West Africa)
Charles NIYONKURU, Philippe LALEYE

Abstract
This study aimed to estimate the length weight relationships and to characterize the condition factor of Sarotherodon melanotheron and Tilapia guineensis, the most abundant and economically important species in lakes Nokoué and Ahémé (the most important brackish water bodies in South of Benin). Specimens were sampled from September 2004 to August 2005. Results of length-weight analyses did not show any differences between juveniles of S. melanotheron in Lake Nokoué and Ahémé (b = 2.85 and b= 2.87 respectively) and between adults the same species from both lakes (b = 2.88 and b = 2.87 respectively). In T. guineensis juveniles of Lake Nokoué showed allometric growth with b-value of 2.42 whereas adult stage, growth became isometric (b = 2.97). The mean condition factors are 4.66 and 4.45 for S. melanotheron and 4.65 and 4.59 for T. guineensis in Lakes Nokoué and Ahémé respectively. Condition factors values were higher in both lakes during the dry and flooding seasons. Both the abundance of acadjas fisheries (brush-park fisheries) in Lake Nokoué and euryphagic habit of S. melanotheron and T. guineensis could explain the differences in the condition factors recorded in Lakes Nokoué and Ahémé for the two species.

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