Electrocardiograms in five bipolar leads recorded from the body surface of three fish species (Cyprinus carpio, Oreochromis niloticus and Pagrus major) in fresh or sea-water.

Abstract 1. 1. ECGs were recorded using five bipolar leads from the body surface of porgy Pagrus major and tilapia Oreochromis niloticus in fresh or sea-water, or held on a dry towel. 2. 2. The maximum QRS amplitude was detected in lead V in both species, being 54 ± 25 μ V in porgy and 241 ± 78 μ V in tilapia, respectively, when the fish were held on the dry towel. 3. 3. Clear ECG waves could not be obtained from porgy in sea-water because of the porgy's small cardiac potential and leakage of the potential. However, clear ECG waves could be obtained in sea-water from the body surface of tilapia, with the average QRS amplitude being 35 ± 8 μ V. 4. 4. The mean electrical P and QRS axes in tilapia were directed toward almost the same direction (frontal downward), whereas both P and QRS axes in most carp were in opposite directions. In porgy, the relationship between the P and QRS axes not be identified due to the smaller amplitude of the P wave.