Yes, you can stop new bids from coming in by pausing your opportunity. This will keep all information in place, but will prevent new publishers from bidding. You'll find the "Pause" button at the top right of the opportunity panel:

Please note that once a pause is requested, there is a 24-hour pending period before it goes into effect. Because we actively recruit publishers specifically for your campaign, this will prevent them from being recruited for paused opportunities. You can restart the opportunity at any time before the application deadline.