Changes in blood pressure in the rainbow trout during hypoxia.

The influence of hypoxia upon the heart rate and the rate and amplitude of breathing in the tench has been reported by Randall & Shelton (1963). Satchell (1961) demonstrated that dogfish respond to anoxia by decreasing heart rate, temporarily increasing dorsal aortic blood pressure and increasing the mean and pulse pressure in the ventral aorta. These fish were restrained and anaesthetized. In this investigation the effects of hypoxia on certain parameters of the breathing and circulatory system were measured. Methods of sampling water and blood afferent and efferent to the gills are described. These methods permit an investigation of these factors in the intact, unanaesthetized, unrestrained but confined rainbow trout.