DNA Barcoding for Species Identification in Aquatic Systems

DNA barcoding has emerged as a robust molecular approach for rapid and accurate identification of aquatic species. By targeting a standardised fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene, researchers can compare unknown sequences against validated reference libraries to discriminate among closely related taxa. This method exploits the principle that interspecific genetic divergence greatly exceeds intraspecific variation, creating a “barcode gap” that facilitates unambiguous species assignment. Applications span from the verification of commercial fish products and the detection of invasive organisms to biodiversity assessments in understudied habitats. Advances in environmental DNA (eDNA) sampling and high-throughput metabarcoding now enable non-invasive surveys of community composition in freshwater and marine systems, while portable sequencing platforms extend field-based diagnostics. Complementary efforts to curate voucher specimens and expand global databases have strengthened taxonomic coverage and minimised misidentifications. As threats to aquatic biodiversity intensify, DNA barcoding offers a scalable tool for conservation planning, fisheries management and the monitoring of ecosystem health on a planetary scale.

Research from Nature Portfolio

Recent studies have applied comprehensive COI barcoding to assess ichthyofaunal diversity in the Indus River system. Sequencing of over 200 specimens from the Beas River yielded barcodes for 43 species across 16 families. Analyses of genetic divergence at species, genus and family levels revealed clear delimitation of most taxa, while uncovering six lineages with unusually high intraspecific variation indicative of cryptic or sibling species. Phylogenetic inference using neighbour-joining and Bayesian methods corroborated species boundaries and exposed misidentified entries in public repositories. This work established the first DNA-based inventory for the river, highlighting economically important and vulnerable taxa, and underscoring the need for targeted conservation measures to safeguard freshwater genetic resources.

DNA Barcoding for Species Identification in Aquatic Systems publication trend

The graph below shows the total number of articles in dna barcoding for species identification in aquatic systems across all publications each year (not limited to Nature Index journals).

Technical terms

Cytochrome c oxidase subunit I (COI): A mitochondrial gene region commonly used as the standard barcode marker for animal species identification.

Barcode gap: The difference between maximum intraspecific and minimum interspecific genetic distances that allows clear species delimitation.

Kimura two-parameter (K2P) distance: A model of nucleotide substitution used to estimate genetic divergence between DNA sequences.

Environmental DNA (eDNA): Genetic material shed by organisms into the environment, which can be sampled from water to detect species presence.

Voucher specimen: A physically preserved organism linked to its DNA sequence, serving as a reference for taxonomic verification.

References

1. Biodiversity of Philippine marine fishes: A DNA barcode reference library based on voucher specimens. Scientific Data (2023).
2. A comprehensive DNA barcoding of Indian freshwater fishes of the Indus River system, Beas. Scientific Reports (2024).
3. DNA barcoding and misidentification of some marine fish species in Nigerian industrial trawl fishery. Scientific African (2023).
4. CoSFISH: a comprehensive reference database of COI and 18S rRNA barcodes for fish. Database (2024).