A. Daily activity cycle:
Recordings of the movements of tagged sharks suggests that most sharks undergo daily activity rhythms. The greatest activity occurs during the twilight and dark hours.
B. Social Behaviour:
Sharks show various degrees of social behaviour but most are basically asocial. A good exmple is the schooling of hammerhead sharks at the Galapogos islands each year.
C. Symbiotic Relationships:
There are several symbionts attached to sharks: (a)Pilotfish, who usually swim with sharks for unknown reasons. This may be to eat all the scraps the shark misses.(b)Small species of fish, like the cleaner wrasse , which picks the shark clear of debris and parasites, (c)Remora fish which attatch themselves to the shark or batoid to ride their bow-wake. They may also eat parasites on the sharks.(d)Parasites of sharks and batoids are usally flatworms and small crustaceans.
D. Shark Attack:
All the attacks on humans and boats have been associated with only 32 species of shark which have the following features in common: They prey on fish or marine mammals, grow to a large size and frequent warmer waters where swimmers are apt to be. Most humans only becomes prey by accident and the shark usually lets go after the first bite. Sharks also may attack due to a territorial drive.