Studies on Fin-Fish assemblage and diversity assessment of upper Bonny River, using morphology and molecular methods of identification

Abstract

This research focuses on the critical issue of biodiversity loss, primarily caused by the misidentification of economically important fish species. Fish samples were obtained at three stations twice in a month from November 2022 to September 2023 with the aid of local fishers using gill nets and cast nets for ecological studies of important fish species of Bonny River, Okrika LGA, Rivers State, Nigeria. The sampling results showed a total composition of 23,102 individuals belonging to six (6) orders, twelve (12) families, fourteen (14) genera and nineteen (19) species which were identified using a combination of DNA barcoding using mitochondrion cytochrome oxidase subunit I (COI) gene marker and morphological method. The tissue samples for 8 species (Pseudotolithus senegallus, Pseudotolithus typhus, Pseudotolithus elongatus, Pangasius polyuranodon, Chrysichthys nigrodigitatus, Neochelon falcipinnus, Coptodon guineensis and Lutjanus aratus) were excised, DNA isolated, amplified and sequenced. Cichlidae showed the highest diversity of 31.41% with three (3) species, Sciaenidae had a diversity value of 24.42% with three species and the remaining 10 families below 10%. Fish diversity was observed to be higher in January 2023 with 19 fish species and lowest in September 2023 with 9 fish species. The Berger-Parker's dominance (d) ranged from 0.01 to 0.31 depicting the dominance of a few species. Simpson's diversity index ranged from 0.90 to 0.99. The study highlights that the high fish diversity in specific species and families within the Bonny River may be attributed to inadequate managerial practices in Bonny fisheries.