Effects of climate change on growth and otolith thermometry of sand whiting (Sillago ciliata) from eastern Australia

This study investigated how a high-emissions scenario of future water temperature and ocean acidification will influence the somatic and otolith growth of an important fisheries species, sand whiting (Sillago ciliata), using an outdoor mesocosm system. The experiment included four treatments with an orthogonal combination of current [~22°C], and future [~25.0°C] predictions of water temperature and current [~8.13] and future [~7.83] pH. Fish length, weight, and otolith weight demonstrated a positive response to warmer water temperatures, but were not significantly influenced by increased ocean acidification. Stable oxygen isotopes within otolith material (δ18Ootolith) deposited during the 3-month experimental period, micro-milled from thin-sections and analysed via IRMS, displayed a negative relationship with water temperature that also varied between acidification treatments. The temperature-dependent fractionation model demonstrated a similar slope to that for inorganic aragonite and other fish species, but a noticeably higher intercept. This relationship has fundamental applications for wild-caught Sillaginidae and can be applied to other fish species to determine thermal preferences and infer dispersal and movement patterns.