MEPS 385:237-244 (2009)  -  DOI: https://doi.org/10.3354/meps08054

ABSTRACT: Otolith microstructure has been shown to record valuable information about fishes including age, growth, and the timing of life history transitions, while microchemical analysis can reveal information about environmental history, dispersal, and migration. For the bluehead wrasse Thalassoma bifasciatum, a common coral reef fish on an oceanic island, we examined whether otolith chemistry could be used to identify the timing of settlement from the pelagic larval phase to the reef-based juvenile phase. This species has a distinct settlement mark visible in its otolith microstructure. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), we found that Ba:Ca ratios increased abruptly at the time of settlement. On average, Ba:Ca ratios were 6.5× greater in the juvenile than the larval phase. Other elements (Mg, Mn, and Sr) also displayed ontogenetic changes in concentration; however, those changes were not associated with the settlement mark. We demonstrate the potential utility of otolith chemistry as a method to identify the timing of settlement (and thereby the larval duration) in other marine fishes with similar early life histories, whose otoliths may not produce distinct settlement checks or those whose settlement stage larvae may not be captured by other means.

KEY WORDS: Larval–juvenile transition · Laser ablation inductively coupled plasma mass spectrometry · LA-ICPMS · Otolith chemistry · Otolith microstructure · Pelagic larval duration