The Devils Hole pupfish has daily and seasonal movement within the Hole. Around midday, when incoming sunlight is at its maximum intensity on the shallow shelf, the number of fish on the shelf decreases. This tendency to leave the shelf at midday is most pronounced April through September. From December to March, when the shallow shelf receives little if any direct sunlight at midday, the number of fish on the shelf increases as the day advances. In the summer months when the shelf receives the most sunlight, fish are overall less likely to use the shallow shelf.