Heart rate as an indicator of activity, metabolic rate, food intake and digestion in pike, Esox lucius

For pike in the laboratory, the relationship between heart rate (fH) and oxygen consumption (VO2, mg h−1 standardized to a 500‐g fish weight) can be described by a significant linear regression valid for heart rates below 55 beats min−1. Heart rate increases during activity and feeding, accurately reflecting fluctuations in metabolic rate; so it can be used as a measure of metabolic rate in the field, using heart beat telemetry techniques. Post‐prandial heart rates are elevated, and closely correlated with the calorific value of the food taken in the preceding meal. Meal size can be estimated from the heart rate record with an error of less than 10%.