Geometric morphometrics as a tool for identifying emperor fish (Lethrinidae) larvae and juveniles

Area of Science:

• Ichthyology
• Morphometrics
• Molecular Biology

Background:

• Accurate identification of fish larvae and juveniles is crucial for ecological and fisheries studies.
• The genus Lethrinus (emperor fishes) presents identification challenges in its early life stages.
• Traditional linear measurements have limitations in distinguishing morphologically similar species.

Purpose of the Study:

• To compare the efficiency of geometric morphometrics versus linear measurements for fish larvae and juvenile identification.
• To assess the utility of geometric morphometrics in distinguishing species within the genus Lethrinus.
• To evaluate the potential of geometric morphometrics as a tool for species identification in early fish life stages.

Main Methods:

• Collected 45 Lethrinus individuals from New Caledonia.
• Identified species using partial cytochrome-b gene sequencing.
• Characterized morphology using 23 landmarks (geometric morphometrics) and 8 linear measurements from digital photographs.

Main Results:

• Geometric morphometrics significantly improved species discrimination compared to linear measurements.
• A 'leave one out' approach showed high discrimination rates for Lethrinus genivittatus and Lethrinus nebulosus using geometric morphometrics.
• Traditional keys failed to distinguish between these two closely related species.

Conclusions:

• Geometric morphometrics is a powerful and promising tool for identifying fish larvae and juveniles to species.
• Integrating image databases with DNA barcodes can enhance the application of geometric morphometrics.
• This method offers a more accurate alternative to traditional identification keys for challenging early life stages.