Geographically widespread swordfish barcode stock identification: a case study of its application

Area of Science:

• Marine Biology
• Genetics
• Fisheries Science

Background:

• Swordfish (Xiphias gladius) are globally important pelagic fish targeted by fisheries worldwide.
• Reliable identification of swordfish stocks is crucial for effective fisheries management and trade.

Purpose of the Study:

• To evaluate the effectiveness of DNA barcoding using the Cytochrome Oxidase I (COI) gene for identifying swordfish species.
• To determine if COI barcoding can distinguish between different geographical swordfish stocks.
• To validate COI's utility by comparing it with the 5'dloop region.

Main Methods:

• DNA barcoding was performed on a 682 bp segment of the COI gene from swordfish of Atlantic, Indian Ocean, and Mediterranean origins.
• Sequences from the 5' hyper-variable fragment of the control region (5'dloop) were used for comparative analysis.
• Phylogenetic analysis (NJ distance-based phenogram with K2P model) was employed to assess genetic variation and stock differentiation.

Main Results:

• The COI gene sequences successfully differentiated swordfish into distinct geographical stocks.
• Phylogenetic analysis of COI sequences correlated haplotypes with specific geographical origins.
• The 5'dloop sequences yielded similar results, confirming the efficacy of COI.

Conclusions:

• Cytochrome Oxidase I (COI) serves as an effective species-specific marker for swordfish.
• COI barcoding has the potential to accurately assign the geographical provenance of swordfish samples.
• This technique can expedite sample analysis in commercial applications, aiding in the detection of mislabeled seafood.