INTERANNUAL CONSISTENCY IN THE FLUCTUATING ENERGY-REQUIREMENTS OF CAPTIVE HARP SEALS PHOCA-GROENLANDICA

To examine seasonal and inter-annual shifts in the energy requirements of captive harp seals (Phoca groenlandica), metabolic rate and body t emperature were repeatedly measured over the annual cycle. Seasonal sh ifts were evident in both parameters, with spring and summer (April to September) peaks decreasing throughout fall and winter (October to Ma rch). Seasonal changes in oxygen consumption concur with earlier publi shed reports and data presented here validate these trends inter-annua lly. The standard metabolic rates (SMRs) of all seals were lower than predicted during fall/winter, but were indistinguishable from expected rates during spring/summer. Although individual variation in metaboli c rate was largely independent of changes in both total body mass and predicted total body fat over the year, such variation was more closel y related to changes in predicted lean body mass. Both deep rectal and core body temperatures co-varied with metabolic rate, perhaps indicat ing a metabolic defense of fat for thermoregulation. The implications of these shifting basal requirements are considered in the light of ca lculating the impact of the harp seal herd on fisheries resources in t he Northwest Atlantic.