The Application of an Infrared-Based ECG Acquisitor in an Online Healthy Assessment System: The Effect of Temperature on Cardiac Function in Carp (Cyprinus carpio)

Carp (Cyprinus carpio) is one of the major farmed fish species in China. In recent years, the increasing water temperature caused by global warming has caused physiological stress in fish, which in turn affects the heart function and health of the fish. Therefore, we hypothesized that the electrocardiogram (ECG) parameters of carp could reflect the temperature-induced stress. To test this hypothesis, in this study, the real-time online cardiac function assessment system (OCFAS) was used to monitor the electrocardiogram signals (heart rate, P wave, R wave, T wave, P-R interval, QRS complex, Q-T interval) of carp at different temperatures. The results showed that the heart rate of the fish increased with the temperature within a certain range. However, when the temperature exceeded this range, the cardiac function of the fish was significantly impaired. The P-R interval was shortened with the increase in the body temperature, and there was a negative correlation between them. This study emphasizes the importance of using real-time online fish ECG assessments to evaluate cardiac health, and it further improves the evaluation index system for ECG in fish. At the same time, the temperature in aquaculture and water environments requires special attention to avoid its adverse effects on the health of aquatic populations.