A method for studying microcirculatory and cardio-respiratory parameters in the fish ( Hypostomus cf. punctatus)

1. A method is presented for measuring respiratory and cardiac rate, as well as microvascular parameters (red blood cell velocity, vessel diameter) in the freshwater catfish Hypostomus cf. punctatus. 2. Unanesthetized animals were kept in a box with flowing water. Microcirculation of the pectoral fin was studied using a closed-circuit television system coupled to a microscope. 3. ECG was recorded with implanted electrodes and respiratory rate was continuously recorded with a cannula close to the mouth. 4. Average values obtained for cardiac, respiratory and cough frequency were 122.8 ± 30.4 min −1 ( n = 4), 105.3 ± 39.4 min −1 ( n = 10) and 90.6 ± 81.1 hour −1 ( n = 6), respectively. 5. The fish usually remained quiet for several hours inside the box while microscopic observations were made.