The effects of temperature and salinity on otolith chemistry of King George whiting

Otolith chemistry is used widely to reconstruct the environmental histories of fish. Examining the relationships between environmental conditions and otolith chemistry is an essential first step towards accurately reconstructing environmental histories, with lack of information potentially resulting in the erroneous interpretation of fish movement and the environments they have inhabited. We evaluated the influence of seawater temperature and salinity on the otolith chemistry of juvenile King George whiting (Sillaginodes punctatus) (Cuvier 1829), a commercially and recreationally important fish species in southern Australia. Juveniles were reared under controlled laboratory conditions at four temperatures (16, 19, 22 and 25 °C) and two levels of salinity (30 and 40) for 90 days. Otoliths were analysed for barium (138Ba), strontium (88Sr), magnesium (24Mg) and manganese (55Mn) using laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS), and ratioed to calcium (43Ca). Otolith chemistry data were analysed using generalized linear mixed models (GLMM). Analyses showed that Mg:Ca and Mn:Ca in the otolith of the fish increased with increasing salinity, whereas Sr:Ca and Ba:Ca decreased with increasing salinity. Temperature only had a minor influence on elemental concentration. The influence of salinity on otolith chemistry suggests that otolith chemistry could be used as a potential tool for reconstructing the salinity and movement history of King George whiting from estuaries to open coast regions.