Phenotypic Plasticity of Thermal Tolerance and Swimming Performance of an Invasive Fish Species, the Northern Snakehead (<i>Channa argus</i>)

Northern snakeheads are an invasive piscivorous fish from east Asia. First reported from the Chesapeake Bay in 2004, they have now expanded their range throughout most of the watershed. Little is known about the physiology of Channa argus despite concerns over its dispersal ability and fitness in different environments. To evaluate the null hypothesis that dispersal capacity of Channa argus is unrelated to environmental conditions, we raised wild caught Channa argus juveniles under 3 different levels of salinity (0, 5 and 10‰) and temperature (15, 20 and 25°C). After at least 2 weeks of acclimation, thermal tolerance was tested both with critical thermal maxima (CT max ) and critical thermal minima (CT min ) tests. Locomotor performance and growth rate were used as proxies for fitness. Locomotor ability was assessed by sprinting the fish through a laser-detection array before and after the thermal tolerance testing. Northern snakeheads tolerated extremes of temperature from 1.1 to 42.3°C, and they displayed robust phenotypic plasticity of thermal tolerance. The ΔCT max of 0.47°C/°C of acclimation temperature and ΔCT min of 0.41°C/°C of acclimation temperature exceeded values reported for most other fishes. Growth rate was also temperature dependent, increasing ~3 fold from the 15°C to the 25°C treatment. Neither thermal tolerance or growth rate were significantly affected by the acclimation salinity however sprinting performance was determined by a complex interaction between temperature and salinity. Individual sprinting ability varied substantially, ranging from size corrected velocities of 68.1 to 138.1 cm*s -1 , but was highly repeatable within a day and across the entire experiment. Sprint performance was temperature dependent, but only at the two higher salinities. Sprinting ability in freshwater was unaffected by temperature as found for most other fishes. Conversely, sprinting ability was salinity dependent, but only at 15°C. At the two higher temperatures, sprinting ability was unaffected by salinity. There was no significant relationship between individual locomotor performance and thermal tolerance. Our conclusion is that the eurythermal and euryhaline Channa argus should have little trouble exploiting most estuarine and freshwater habitats on the east coast of the United States apart from more saline habitats in the winter when their ability to escape predators or capture prey may be somewhat compromised. Funded by the Towson University Graduate School This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.