Background/Aims
Understanding the preferred temperature of aquatic ectotherms is valuable for disciplines ranging from conservation ecology to aquaculture science. For mobile animals like fish, two-chamber “shuttlebox” systems are often used to enable behavioural thermoregulation and the selection of a preferred temperature, as well as providing insight into upper and lower avoidance temperatures. While studies using shuttleboxes have provided valuable data, they have overlooked potential issues that could bias the quantification of the animal’s preferred temperature. Here, we investigated the preferred temperature of the ecologically important common jollytail (Galaxias maculatus) and addressed several of the biases that may impact shuttlebox experiments.
Methods/Results
First, we individually introduced fish to the shuttlebox system with the starting temperatures set to 19°C and 21°C in each chamber. We found little variation between individuals, and most stabilized between 14 and 18°C after 48 hours in the shuttlebox. Noting that active fish may continuously shuttle between warm and cool chambers and prevent the system from significantly warming or cooling away from the starting temperature, we investigated whether our calculated preferred temperature was robust if we introduced fish into the shuttlebox at cooler starting temperatures of 10°C and 12°C. Fish introduced at cooler temperatures showed similar preferred temperatures as the previous group (14-18°C), giving us confidence that our results were not biased by experimental artifacts. We additionally observed that cooling rates are typically slower than heating rates, which could cause a bias towards higher preferred temperatures in active species that regularly cross between chambers.
Conclusion
Our findings highlight that the common jollytail exhibits strong behavioural thermoregulation across starting temperatures, though potential biases from dynamic systems like the shuttlebox should be carefully considered. We propose methodological refinements to shuttlebox experiments to ensure future estimates of preferred temperatures are robust.