THE LIMITATIONS OF HEART-RATE ASA PREDICTOR OF METABOLIC-RATE IN FISH

Although telemetered heart rate (f(H)) has been used as a physiologica l correlate to predict the metabolic rate (as oxygen consumption. VO2) of fish in the held, it is our contention that the method has not bee n validated adequately for fish. If f(H) in fish is to be used to esti mate VO2 a single linear (or log-linear) relationship must be establis hed for each species between the two variables which allows VO2 to be predicted accurately under ail environmentally relevant conditions. Ou r analyses of existing data indicate that while a good linear (or log- linear) relationship can be established between f(H) and VO2, the cond itions under which the relationship applies may be quite restricted. P hysiological states and environmental factors affect the relationship between f(H) and VO2 significantly such that several curves can exist for a single species. In addition, there are situations in which f(H) and VO2 do not covary in a significant manner. Ln some situations f(H) can vary over much of its physiological range while VO2 remains const ant: in others VO2 may vary while f(H) is invariate. The theoretical b asis for this variability is examined to explain why the use of teleme tered f(H) in predicting VO2 of fish may be limited to certain specifi ed applications. (C) 1996 The Fisheries Society of the British Isles