The rate of energy metabolism required to maintain a non-growing, non-active, ectothermic animal. It is measured at a specified temperature, because the SMR of ectotherms varies according to the environmental temperature. The SMR of aquatic animals such as fishes and shrimps can be calculated from their oxygen consumption, e.g. by monitoring changes in the oxygen concentration of the water in a specially designed aquarium. Compare basal metabolic rate.