If you do not remove idle fixtures, at least disconnect the wiring to them. Disconnecting power at a circuit breaker panel makes it too easy to restore power. Similarly, removing the lamps is ineffective by itself because the lamps will be replaced sooner or later. Furthermore, this practice involves some safety hazard because the electrodes are left exposed.
All fluorescent and HID fixtures have ballasts. A ballast continues to draw current even if the lamp is removed. Therefore, disconnect the wiring ahead of the ballasts, rather than just removing the lamps. With fluorescent fixtures, you have the choice of leaving some of the lamps in operation. See Measures 9.2.1 ff for the details of delamping fluorescent fixtures.