Sharks do not prey on bottlenose dolphins as they will attack the sharks. Dolphins eat a wide variety of fish, and their hunting behavior varies according to the avalability of food . When large schools of fish are present, as many as several hundred dolphins will cooperate in catching the fish by communicating with one another. They drive the fish into a dense mass and force them to the surface of the water, making it impossible for the fish to escape. The also emit loud sounds to further confuse the prey.
Dolphins usually hunt during the day.
However, when fish begin migrating or are scarce, dolphins become nocturnal hunters. They search for squid and bottom-dwelling fish which are active at night. Dolphins are very sociable animals that generally live in groups. Their friendly, cooperative behavior is vital to their survival. When a dolphin is sick or injured, it cries of distress summon immediate aid from other dolphins, who try to suppoert it to the surface so that it can breathe.