Factors Influencing Otolith Elemental Incorporation: Implications for Field Applications

Studies based on variation in otolith elemental composition have become common although the regulatory mechanisms of incorporation have yet to be fully elucidated. Laboratory studies on two marine (black rockfish Sebastes melanops and Pacific cod Gadus macrocephalus) and an anadromous (Chinook salmon Oncorhynchus tshawytscha) fish species were completed to examine the effects of temperature, salinity, and water concentration on otolith elemental incorporation. Observed patterns highlight the importance of species-, and potentially stage-, specific effects. The one consistent observation was a positive relationship between otolith and water composition for Sr and Ba. Temperature effects were highly variable. For juvenile black rockfish, there were significant positive effects of temperature on the incorporation of Sr and Ba and negative effects for Mn. For larval Pacific cod, there were negative effects of temperature on the incorporation of Sr and Ba and no effect detected for Mg. For juvenile Chinook salmon, there were significant interactions between temperature and salinity that influenced Sr and Ba incorporation and need to be considered when reconstructing migratory histories. When examined, the effects of somatic and otolith precipitation rate were generally non-significant although a negative effect of somatic growth rate on Ba incorporation was observed in Chinook salmon. In general, the results are contrary to expectations based on models of abiotic mineral growth and highlight the importance of metabolic effects. Given the clear presence of vital effects on elemental incorporation, it may be necessary to develop species-specific models of incorporation to provide the appropriate framework for field applications.