Invasive goldfish (Carassius auratus) maintain aerobic scope across acute warm water temperatures.

Goldfish (Carassius auratus) were first introduced to the Laurentian Great Lakes when it was first introduced into Lake Ontario in the 1800s. In the past 15 years, there have been dramatic increases in both goldfish abundance and geographic spread across North America, including the Great Lakes, raising concerns about its potential for negative impacts on aquatic ecosystems. Climate studies suggest that habitat ranges suitable for goldfish will continue to expand in the future as water temperatures rise towards its thermal optima. We explore whether warmer temperatures are physiologically suitable for a population of wild, invasive goldfish (Hamilton, ON, Canada) by testing aerobic scope (AS) at current (26°C) and predicted (30°C) peak summer water temperatures. Goldfish were first acclimated to a common-garden average summer pond temperature (22°C), then their AS was estimated by calculating the difference between routine and maximum metabolic rates (RMR and MMR) at the two test temperatures. Our results demonstrate that wild goldfish sustain their AS through increases in both RMR and MMR from 26°C to 30°C (mass-standardized means of 1.07 versus 1.17 mgO2h-1 at 26°C versus 30°C, respectively). This ability to sustain aerobic energy budget at high peak water temperatures could offer physiological benefits to this invasive population in a warming climate.