To glue or not to glue? Reassembling broken otoliths for population discrimination

Area of Science:

• Ichthyology
• Fish biology
• Otolith morphometrics

Background:

• Otoliths (ear stones) are crucial for fish identification and population studies.
• Otolith shape analysis is a common technique in fisheries science.
• The integrity of otoliths can be compromised during collection and preparation.

Purpose of the Study:

• To assess the impact of breaking and gluing Atlantic cod (Gadus morhua) otoliths on shape analysis.
• To determine if preparation artifacts affect otolith shape discrimination using morphometric and Fourier analyses.

Main Methods:

• Eight shape measurements were taken from 25 Atlantic cod otoliths.
• Fourier analysis was applied to the outlines of intact and repaired otoliths.
• Cluster analysis was used to evaluate the impact of morphological differences on discriminant analysis.

Main Results:

• Seven of eight shape measurements showed minor differences between intact and glued otoliths.
• No significant differences were observed in Fourier descriptors between intact and glued otoliths.
• Cluster analyses confirmed that preparation artifacts did not impact discriminant analysis outcomes.

Conclusions:

• Breaking and gluing Atlantic cod otoliths has a negligible effect on shape analysis.
• Otolith shape discrimination using discriminant analysis remains reliable even with repaired otoliths.
• This finding supports the use of prepared otoliths in fisheries research.