The Bigeye Thresher shark is known for its unique appearance. Like all Thresher species, it has an extremely large caudal fin which is roughly half the length of its entire body, although the Bigeye Thresher’s caudal fin is slightly smaller than that of other Thresher species. The Bigeye Thresher is also distinguishable by its very large eyes which have a vertical diameter of around 4in/10cm. They are typically found in deeper water than other Thresher species. They don’t interact much with humans but are occasionally caught as bycatch by commercial fishers which has resulted in them being placed into the “vulnerable” category by the IUCN.
At-A-Glance
Scientific Name – Alopias superciliosus
Size – On average, about 9-13 ft/3-4 m but can grow up to a maximum of 16 ft/5m.
Habitat – Found in all temperate and tropical oceans, in both pelagic and coastal waters, and in both deep and shallow waters.
Diet – Schooling forage fish, squid, pelagic fishes, octopus, and crabs.
Reproduction – Ovoviviparous (pups are nourished in utero via yolk sac and birthed live).
IUCN Listing – Vulnerable.
Protection – Listed under Appendix II of CITES.
Bet You Didn’t Know…
- Bigeye Threshers undergo a daily vertical migration in which they spend the day at depths of 980–1,640 ft/300-500m and surface at night for feeding.
- Their large caudal fin is used as a whip to stun prey. They often target schools of fish to stun multiple prey at a time.
- The eyes of the Bigeye are roughly the shape of an upside-down pear, and their pupils are permanently upturned so they can scan the water above it for prey or predators.
Images: Jeff Rotman
Ready To Dive In?
There are no dive sites that advertise Bigeye Threshers but several which advertise other thresher species, primarily the Pelagic Thresher:
- Malapascua Island, Philippines
- Pescador Island, Philippines
- Alor, Indonesia
- Osprey Reef, Great Barrier Reef
- Bali, Indonesia
Science In The Spotlight
The Bigeye Thresher goes through a vertical migration every day, but why? How is this behavior beneficial and how far do they travel everyday? Discover the physiological and behavioral motives behind this strange behavior.
Photos: Jamie Pollack, Douglas Seifert, Jeff Rotman, Alex Tyrrell, Thresher Shark Divers
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