3.3.2 Order Perciformes
Perciformes is the most dominant order among the marine fishes of Bangladesh and contributes to over 50% of total exploited species. A total of 195 samples were sequenced belonging to 35 families, 79 genera and 100 species. Among the 35 families, Gobiidae was the most dominant one followed by Carangidae, Sciaenidae and Polynemidae. The overall mean nucleotide base frequencies observed for these sequences were- T: 29.90%, C: 28.10%, A: 23.80% and G: 18.20%. The AT content (53.70%) was higher than the GC content (46.30%) (Fig. 3). The GC contents at the first, second and third codon positions were 56.70%, 42.70% and 39.50% respectively. The K2P distances of the COI sequence within species, genus and family were 0.58, 6.26, and 15.62, respectively. In the NJ tree, most of the specimens belonging to the same species were clustered together bolstering the prior taxonomic assignment based on morphology (Supplementary Fig. 2).