Length-weight relationship and condition factor revealed possibility of mix strains in Clarias gariepinus population of Oueme Valley, Benin Republic (West Africa)

Abstract

Growth behaviour (Length-Weight Relationship-LWR), condition factor (K) and phylogenetic linkage of sourced Clarias gariepinus from Oueme valley (main catfish brooder source in Benin) was investigated to understand possible sources of diversity in growth pattern in spawned C. gariepinus . 30 random C. gariepinus ‘labelled’ brooders from sellers in each of Adjohoun(wild-habitat); Dangbo(culture-habitat) and Porto-Novo(culture-habitat) were characterized for differences(p<0.05) in Mean Length-ML (cm), Mean Weight-MW (kg), condition factor (K) and growth behavior (LWR intercept-a; slope-b) in sexes and unsexed populations. 16S barcode gene sequences of 10 random tissue subsamples from each group (n=30) were analyzed for genetic linkages using Maximum Likelihood Method. ML was similar across populations; MW and K similar across Dangbo and Porto-novo; MW similar across sexes of populations; ML and K similar across sexes in Adjohoun, but differ across sexes in Dangbo and Porto-Novo. In unsexed populations, Iintercept-a ranged 0.46(Porto-novo)-0.82(Dangbo), Slope-b -1.37(Porto-novo), 2.14(Dangbo), 2.60(Adjohoun); intercepts were 0.94; 0.63, 0.87; 0.78, and 0.36; 0.61 in respective male and female Adjohoun, Dangbo and Porto-novo; Slope ‘b’ 2.97; 2.05(Adjohoun); 2.87; 2.34(Dangbo), -1.23;-1.78(Porto-novo). Irrespective of sexes, growth was negative allometry in Adjohoun and Dangbo; positive allometry in Porto-novo. 80%Porto-novo were closest to Clarias batrachus ; 20% closest to C. gariepinus x C. batrachus- crossbred; 70%Dangbo closest to C. gariepinus x C. batrachus- crossbred , 10% closest to Clarias batrachus . 20% closest to C. gariepinus. 90%Adjohoun was closest to C. gariepinus x C. batrachus -crossbred, 10% closest to C. gariepinus . Growth behaviour and condition factor diverged irrespective of sexes in populations. Each populations contained mixed strains of Catfish species mistaken as C. gariepinus whose growth pattern could be influenced by growth behaviour of the dominant strain . Dominance of C. batrachus x C. gariepinus- crossbreds’ in culture-Dangbo and Wild-Adjohoun signals possible introgression of the invasive C. batrachus gene, indicating dire need for stricter management and conservation of local catfish gene pool for posterity.