The respiration rate of Sagitta elegans in Bedford Basin, Nova Scotia, was found to be significantly different at different times of the year. Respiration rates were lower in summer and fall than during spring because the animals acclimated to warmer temperatures as the year progressed. The annual energy expenditure by respiration of the S. elegans population in St. Margaret's Bay, Nova Scotia, was equal to the net yearly production of the population; the calculated minimum ingested energy for this population was estimated to be between 13.2 and 20.0 kcal 100−3 year−1, or about 0.7–1.1% of the estimated total energy produced annually by copepods in the Bay. S. elegans probably has its greatest impact on the zooplankton community in St. Margaret's Bay during winter and early spring, when its biomass is greatest and its energy of respiration per unit volume of water is highest.