Changes in blood pressure, heart rate and breathing rate during moderate swimming activity in rainbow trout.

There is a paucity of data concerning the changes in circulation occurring during swimming in fish. Data reported in the literature have been obtained from either restrained, anaesthetized or operated fish (Greene, 1904; Hart, 1945; Johansen, 1962; Robertson et al. 1966). Such procedures can have marked effects on fish (Fry, 1957). It is therefore surprising that little attention has been directed towards measuring parameters of circulation and respiration in unrestrained, unanaesthetized, intact fish (Randall, Smith & Brett, 1965). Recently, methods have been developed for measuring blood pressures using indwelling cannulae (Smith & Bell, 1964; Holeton & Randall, 1967). These techniques, combined with those of Brett (1964) which use varying water velocities to produce variations in swimming speeds in fish, permit measurement of various parameters of circulatory and respiratory systems in swimming fish. The present study was undertaken to examine the effects of swimming on circulation and respiration using free swimming, unanaesthetized rainbow trout.