Happens all the time. Below is one of many examples:
During ice fishing season fish tend to bite mainly during the morning or evening. The reason for this rests solely on the zooplankton in the water. In the morning, the zooplankton go towards the bottom. The fish move towards the bottom and become less active. During the evening, the zooplankton rise towards the top thus the fish move up to feed on the zooplankton. This is the main reason why, when the morning bite tapers off, you fish lower in the water column. It is the reverse in the evening.
Obviously this is one example of many as to why fish will "shut off". Other factors are sunlight, water tempurature, etc... The spot you are fishing might get a certain portion of sunlight at 11:15, or tempurature change. Like I said, one example of many.
When they shut off, I go looking for other fish that are still biting. I also look for a different area where the sunlight/wind, temp might not affect the water the same as the previous spot.