Multiply charged ions are studied in the Constance B quadrupole mirror experiment [Phys. Rev. Lett. 59, 1821 (1987)] in order to better understand the ion physics of electron cyclotron resonance (ECR) high charge-state ion sources. By measuring the ion densities and end loss fluxes, the parallel confinement times for the first five charge states of oxygen plasmas are determined. The parallel ion confinement times increase with charge state and peak on axis, both indications of an ion-confining potential dip created by the hot electrons. The radial profile of ion end loss is normally hollow, with the peak fluxes occurring at the edge of the ECR zone. An attempt is made to increase the end loss flux of a selected ion species by decreasing its parallel confinement time using minority ion cyclotron resonance heating (ICRH). In addition, an ion model is developed to predict the ion densities, end loss fluxes, and confinement times using the ion particle balance equations, the quasineutrality condition, and theoretical confinement time formulas. The model generally agrees with the experimental data to within experimental error.