Because of their long tail (upper lobe of the caudal fin) that can be as long as the body of the shark they are also known as fox sharks. Out of the three described species of thresher shark (1) the pelagic thresher shark is the one mainly seen by scuba divers.

 

Hunting

The thresher shark uses its scythe-like tail to hunt by slap small fish like sardines stunning them. The dazed prey can then easily be eaten (2).

The video below by Animal Wire shows the tail-slapping of prey.

Distribution

Thresher sharks can be found in temperate and tropical open oceans. While these pelagic sharks stay mostly deep 100 to 500 m they can be seen in shallower waters as well as close to shore at cleaning stations or hunting.

 

Dive with the threshers

Due to the large eyes these sharks are very sensitive to light and are mainly seen early morning or late afternoon. Thresher sharks can be encountered in many different areas. However, the most reliable way of seeing them is to visit the cleaning stations at Monad Shoal close to Malapascua in the Philippines.

 

Conservation

The IUCN lists all members of the genus Alopias, so all thresher sharks, as vulnerable globally because the populations are declining. The main causes for this are a combination of slow life history characteristics “and high levels of largely unmanaged and unreported mortality in target and bycatch fisheries” (3). An additional threat are sport fishers who target large and special sharks like the threshers.

 

References:
1 World Register of Marine Species
2 Oliver SP, Turner JR, Gann K, Silvosa M, D’Urban Jackson T (2013) Thresher Sharks Use Tail-Slaps as a Hunting Strategy. PLoS ONE 8(7): e67380. doi:10.1371/journal.pone.0067380
3 The IUCN Red List of Threatened Species