The thresher shark isn't the most famous shark, partly because it's a rare one to spot, and therefore isn't often filmed.
Easily recognized by its very long tail fin, the shark is a shy and elusive creature that primarily lives in deep waters. It is a pelagic hunter, and is therefore most often seen on offshore reefs.
Actually, the thresher shark isn’t a single shark species, but rather three shark species under the same family, or genus, known as the pelagic thresher, the bigeye thresher, and the common thresher.
This article will focus on the latter, though most of the facts are similar for all three.
The pelagic thresher and the common thresher are often mistaken, as the only significant differences between the two being a white patch on the pelagic threshers’ on the base of its dorsal fins, and the fact that the pelagic is quite a bit smaller than the common thresher.
However, even professionals often mistake the two.
The shark is easily recognized by the very large tail fin, which can be as long as the shark’s body in some cases, and account about a third of the shark’s weight.
It is from this physical trait that the shark derives its name, both the common English one and the Greek one.
Its Greek name stems from the word for “fox”, and the English name “thresher” refers to the shark’s unique hunting technique, where the sharks drive schools of fish together and then strike, or “thresh”, at them with their tail to stun them.
Where to see it
Threshers can be seen in the Atlantic, North America, Asia, the Red Sea, and the North Pacific.
It is pelagic, so it is rarely seen at reefs near the shore, but can be seen at off-shore reefs near deep water, especially near cleaning stations.
It is a highly shy animal, and is typically only seen individually, most often hovering the blue water, off the reefs.
Best times to see it
Threshers are rarely seen by divers, so designating a specific season to them is difficult. Sightings seem to be more a matter of luck than times of the year or day.
Malapascua in the Philippines is the only known place where threshers can be seen regularly, and year-round.
Interaction with humans
Thresher sharks are notoriously shy, so precious little is known about them. Therefore, caution is advised, as we don't know much about how they react when coming in contact with humans.
However, no actual attacks on humans have been reported, so it is likely that the shark is quite benign. Some divers have reported being hit by the tail fin, probably by mistake.
Like most sharks, the thresher reproduces infrequently and matures quite late, making it vulnerable to overfishing.
It is a game fish in certain parts of the world. Because of this, all three species of thresher shark are considered endangered.
Read more about sharks here.