As many as 440 species of sharks - and the sub-species of these 440 odd species, are found in various oceans of the world. This diversity in shark species makes it a tough task to recollect the geographical range and habitat of every single species. While thresher sharks are easily recognized with their characteristic long tail which resembles a thresher, not many people are actually familiar with the geographical range or natural habitat of this species.
Thresher sharks, at times referred to as 'threshers', are species of sharks belonging to the lamniform order. The members of the lamniform order of sharks are typically characterized by two dorsal fins that they possess along with an anal fin, five gill slits and their mouth extending behind the eyes. Other than the thresher sharks, the Great white sharks, the Goblin sharks, also happen to be the members of this order of sharks. There exist three extant sub-species of the thresher sharks - the Pelagic thresher Alopias pelagicus, Bigeye thresher Alopias superciliosus and the Common thresher Alopias vulpinus. The habitat of all these three sub-species spans across the temperate and tropical waters of the world, and that's what we will be emphasizing on from here on.
In terms of geographical extent, the thresher shark is found in all the temperate and tropical oceans of the world - i.e. the Pacific Ocean, Atlantic Ocean and the Indian Ocean. The pelagic thresher is found in the tropical and subtropical waters of the Pacific Ocean and the Indian Ocean. On the other hand, the Bigeye thresher and the Common thresher are found in the Pacific Ocean, Indian Ocean as well as the Atlantic Ocean. Even though these species are not migratory in nature, it isn't really surprising to see them thousands of miles away from what is considered to be their normal geographic range.
Thresher sharks are basically pelagic in nature i.e. they prefer living in the open sea rather than in coastal or inland waters. However, their sighting in shallow, inshore waters is not a rare occurrence as such. Rarely though, will you get to see a thresher is depths exceeding 500 meters. It is the young ones of this species which are most often found in the shallow waters, and as they start growing they start venturing in the open oceans. The sub-species of thresher sharks tend to prefer the areas of high biological productivity wherein food - in form of schooling fish species, is found in abundance. That explains why threshers are also found around the coral reefs and seamounts - underwater mountain rising above the ocean floor, quite often.
At the same time, it also depends on which sub-species is being taken into consideration with the Common threshers more often venturing into shallow coastal waters of the continental shelves, while the pelagic thresher - as its name suggests, mostly preferring open oceans. Even though the pelagic thresher prefers open oceans, it does venture towards the shore as well as coral reefs and sea mounts in search of food. The Bigeye thresher - on the other hand, is known to frequent between the continental shelf and open sea. The Bigeye thresher prefers those regions of the world wherein the temperature ranges between 61°F to 77°F. As opposed to the other two sub-species, the Common threshers are found close to the land.
The 'gamefish' tag bestowed upon the thresher sharks - along with the low fecundity which happens to be a characteristic attribute of almost all types of sharks, has made this species vulnerable to overfishing. The fact that these sharks become easy targets when they come to the shallow waters makes them all the more vulnerable to hunting. The International Union for Conservation of Nature (IUCN) has enlisted all the three sub-species of the thresher sharks as vulnerable to extinction. If we take into consideration the fact that they are of great importance for the overall marine ecosystem, it wouldn't be surprising to see an ecological collapse in these regions if this species becomes extinct.