Relationships between heart rate and metabolic rate of pike: integration of existing data

The percentage contribution of heart rate ( f _H) to change in oxygen consumption ( V o₂) was examined in relation to body weight and across the metabolic scope of pike. Also the consequences of variability around the regression relating V o₂ and f _H for estimating V o₂ were considered. The percentage contribution of f _H was calculated using two equations, one that ignored and one that included an estimate for oxygen consumed by the gills and absorbed across the skin ( V o_2s). Using both equations the percentage contribution of f _H calculated using maximum and resting values for f _H and V o₂ decreased with weight of pike. The omission of V o_2s, resulted in erroneously high estimates of the percentage contribution of f _H for pike of any given weight. The omission of V o_2s resulted in erroneously high estimates of the percentage contribution of f _H over the region of the metabolic scope where f _H is related linearly to V o₂, whereas the equation that included V o_2s resulted in the expected value of 100%. Assuming zero experimental error and under normoxic conditions, the 95% confidence limits for single estimates of V o₂ from 30–60-min readings of heart rate are ±39% at a heart rate of 30 beats min ⁻¹. Averaged over longer periods the error decreases, and used over several days to estimate meal size the error is of the order of 1%.