The limitations of heart rate as a predictor of metabolic rate in fish

Abstract

Although telemetered heart rate ( f H ) has been used as a physiological correlate to predict the metabolic rate (as oxygen consumption, V̇O 2 ) of fish in the field, it is our contention that the method has not been validated adequately for fish. If f H in fish is to be used to estimate V̇O 2 , a single linear (or log‐linear) relationship must be established for each species between the two variables which allows V̇O 2 to be predicted accurately under all environmentally relevant conditions. Our analyses of existing data indicate that while a good linear (or log‐linear) relationship can be established between f H and V̇O 2 , the conditions under which the relationship applies may be quite restricted. Physiological states and environmental factors affect the relationship between f H and V̇O 2 significantly such that several curves can exist for a single species. In addition, there are situations in which f H and V̇O 2 do not covary in a significant manner. In some situations f H can vary over much of its physiological range while V̇O 2 remains constant; in others V̇O 2 may vary while f H is invariate. The theoretical basis for this variability is examined to explain why the use of telemetered f H in predicting V̇O 2 of fish may be limited to certain specified applications.