You can Lock the hired candidates, to prevent other users from associating the candidate with other job openings. The locked candidate will not be listed in the candidates list.

To lock the candidates:

1. Click Job Opening tab.
2. Click a particular Job opening.
3. On the right panel, under the "Associated Candidates", select a candidate and click Hire.
4. Now you can check the box "Lock this candidate".
5. Click Yes.