Morphological and Genetic Characterisation of Mango Tilapia, Sarotherodon galilaeus (LINNAEUS, 1758) from Bafing and Bakoye Rivers in Mali

Abstract

The study aimed to compare the Morphological and Genetic characterisation of Mango tilapia, Sarotherodon galilaeus (Linnaeus, 1758) from Bafing and Bakoye rivers in Mali. One hundred twenty nine specimen were collected form Bafing and Bakoye rivers. From each specimen 18-morphometric measurements, 5-meristic counts were recorded. For molecular genetics, tissue samples from gills and muscles were from each specimens and preserved in absolute alcohol for molecular studies. The ratio indices, morphometric, meristic, length at the first maturity stage, length weight relationship and D-loop mtDNA indices were used to study and compare similarities and differences between Sarotherodon galilaeus collected from the Bafing and Bakoye. Further, the Wilcoxon rank sum test and the T-test were used to perform whether there were significant morphological and meristic differences. The different stages of the gonads were determined by visual inspection of the appearance adapted by Marcano et al. (2007) to resolute the Lm50. The result of the length-weight relationship indicated a slight variation in the weights at a particular size, referred to as residuals. Further, the R-squared values were 0.90 for Bafing and 0.88 for Bakoye. The model is significant for both rivers with allometric values < 3. The Lm50 was 16.99 cm for females and 15.09 cm for males for Bafing and 11.37 cm for females and 16.33 cm for males for Bakoye. The observations on the frequency distribution of the total number of S. galilaeus showed higher frequencies of fish between 11 and 17 cm TL for both rivers. The morphometric measures of three parts of the body (BD, CPD, CPL) shape the three parts of the head (HL, CHD, LAD) showed a significant difference, and the meristic counts show a considerable difference between DF and LONG. Genetic analysis of 311 samples from the location of Bafing, Bakoye, four from Israel, and three from Ghana revealed variations in the D-loop of the mtDNA. The Ghanaian and Israeli populations showed the lowest number of haplotypes and the lowest values of nucleotide differences and haplotype diversity, and the highest haplotype diversity and nucleotide were found in Mali. This study shows that significant differences between the rivers exist on a genetic and a morphological level, indicating population differentiation.