Exploring the drivers of otolith Sr/Ca during the early life stages of Larimichthys polyactis: insights from cultured and wild populations

Otolith Sr/Ca profiles are widely used to investigate early life migration and habitat use in both diadromous and oceanodromous fishes. This study focuses on Larimichthys polyactis , an oceanodromous species of significant ecological and commercial importance in East Asian waters. This study investigates the influence of environmental factors on the otolith Sr/Ca ratios during its early life stages (ELS). In Experiment A, we analyzed both laboratory-reared specimens—maintained under stable temperature (19–21°C) and salinity (27–28 PSU) conditions—and wild-captured specimens. The results revealed a consistent decline in Sr/Ca ratios throughout the ELS in both groups, suggesting that temperature and salinity may not be the primary drivers of otolith Sr/Ca ratios during early development. In Experiment B, Sr/Ca ratios in the core (incubation stage) and edge (recently spawned stage) zones of otoliths from both wild and laboratory-reared adult fish were compared. Sr/Ca ratios were significantly higher in the core zone than in the edge zone, indicating that maternal influences are may not be the main cause of elevated Sr/Ca ratios in the otolith core. Collectively, these findings suggest that otolith Sr/Ca ratios during ELS in L. polyactis are more affected by the ontogenetic developmental stage than by environmental factors such as temperature, salinity, or maternal effects. This challenges previous assumptions about the dominance of environmental factors in shaping otolith chemistry and highlights the need for more nuanced interpretations of Sr/Ca data, especially in studies of oceanodromous fishes. When utilizing otolith microchemistry to reconstruct life history, it is essential to minimize physiological effects through controlled culture experiments to ensure the accuracy and reliability of the results.