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

Abstract

Growth pattern (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.

Mean length-ML cohorts(1:1 sex ratio) of 30 randomly selected 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 Weight-MW(g), 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 the populations were analyzed for genetic linkages using Maximum Likelihood Method. ML ranged 34.26 ± 2.17 cm-35.54 ± 2.07 cm. MW was similar across Dangbo(326.18 ± 51.64) and Adjohoun(364.57 ± 64.48), significantly highest in Porto-novo(410.42 ± 54.67). K (0.72 ± 0.03-Dangbo − 1.02 ± 0.09-Porto-novo) differ across populations; ML and MW similar across Adjohoun sexes; different (male > female) across Dangbo and Porto-Novo. Sexes similar in K in Portonovo and Adjohoun but differ in Dangbo. At p = 0.00, r2 ranged 0.81–0.94, ‘a’ 0.45(Porto-Novo) to 1.09(Adjohoun), ‘b’ 0.18(Adjohoun) to 0.42(Porto-Novo) in unsexed population. Male and females ‘a’ were 1.01:1.16(Adjohoun), 0.77:0.85(Dangbo), −0.41:0.86(Porto-Novo); ‘b’ 0.21:0.15(Adjohoun), 0.31:0.28(Dangbo) and 0.75:0.26(Porto-Novo) at p = 0.00, r2 range 0.72–0.90. 80 %Porto-novo were closest to Clarias batrachus; 20 % closest to C. gariepinus × C. batrachus-crossbred; 70 %Dangbo closest to C. gariepinus × C. batrachus-crossbred, 10 % closest to Clarias batrachus. 20 % closest to C. gariepinus. 90 %Adjohoun was closest to C. gariepinus × C. batrachus-crossbred, 10 % closest to C. gariepinus.

The populations diverged in weight, condition factor and sexual dimorphism, and demonstrated negative allometry irrespective of sexes to implicate sub-optimum robustness. Each contained mixed strains of Catfish species mistaken as C. gariepinus whose growth could be influenced by growth attributes of dominant strain. Dominance of C. batrachus × C. gariepinus-crossbreds’ in culture-Dangbo and Wild-Adjohoun signals possible introgression of invasive C. batrachus gene, indicating dire need for stricter management and conservation of local catfish gene pool for posterity.