Pelagic thresher
Alopias pelagicus
Pelagic threshers are shy, graceful sharks with a remarkably long tail. An early-morning glimpse at a cleaning station is a lovely reward for patience.
Endangered (IUCN, 2018) means it is at very high risk of extinction in the wild.
Photos show the species, not always the places on this page.
Length
Usually about 3 m (10 ft), most under 3.3 m (10.8 ft); largest recorded 4.28 m (14 ft)
Weight
Usually about 70 kg (153 lb), most under 88 kg (195 lb); maximum weight not reliably measured
Next to a person
About one-and-three-quarter times as long as an adult person, yet about the same weight as one adult
What it eats
Small schooling fish such as herring, flying fish and mackerel, plus squid.
Around people
Calm, give space
How it lives
The pelagic thresher is mainly an open-ocean shark that sometimes comes close inshore. It uses the very long, strap-like upper part of its tail to stun prey with sharp blows, sometimes circling a school of fish first to tighten it. Females usually give birth to two large pups at a time.
Where it goes
Mainly an open-ocean shark, but it comes up to shallow cleaning stations near Malapascua all year, most often in the morning. Ten sharks with acoustic tags were detected at the shoals on about a third of their days. Since around 2022 most sightings are at Kimud Shoal, next to Monad Shoal. No long journeys from these sharks are published yet.
We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.
Populations
The pelagic thresher lives in the Indo-Pacific and is the thresher species seen at Malapascua. Its behaviour at cleaning stations, and the chance of seeing it on a dive, depend on the site.
Meet it respectfully
At Malapascua, local rules ask for scuba only, at least 5 m from the sharks, and no flash or strobes. Stay behind the marked line near the cleaning stations. Stay low and still, and let the shark choose how close it comes. Never chase, block or touch it, do not position yourself behind its tail, and do not touch the reef.
Fun fact
Tap the bulb to light it up.
A thresher's tail can make up around half of its total body length.
The pelagic thresher is the smallest of the three thresher species.
Its most extraordinary weapon, the tail, is aimed at prey, not at divers.
At Monad Shoal, Malapascua, scientists watched pelagic threshers for 1,230 hours between 2005 and 2009 and recorded 97 cleaning visits. Visits happened at all times of day but became less frequent from morning to evening.
Source: Oliver et al., 2011, PLOS ONE, oceanic sharks clean at a coastal seamount
Off Pescador Island, Cebu, pelagic threshers were filmed hunting sardines with overhead tail slaps. The fastest tail slap measured was 21.82 m per second.
Source: Oliver et al., 2013, PLOS ONE, thresher sharks use tail-slaps as a hunting strategy
In 2014 scientists reported a pelagic thresher giving birth at a cleaning station in the Philippines.
Source: Oliver et al., 2014, Coral Reefs, a pelagic thresher gives birth at a cleaning station
Its cousin the bigeye thresher moves up and down every day. Two tagged sharks spent most daytime hours between about 300 and 500 m deep, and came up to the top 100 m at night.
Source: Weng and Block, 2004, Fishery Bulletin, diel vertical migration of the bigeye thresher
Another cousin, the common thresher, was tracked off southern California. Young ones stay all year, while larger sharks often leave in spring and winter, travelling between Baja California and California, and some adults go as far north as British Columbia.
Source: Kinney et al., 2020, Marine Ecology Progress Series, common thresher movements
Pelagic thresher in the Ocean Atlas
Places we have researched where this animal is recorded. It is never guaranteed, and some places are for watching from the boat only.
Travel with usComing soonTrusted referralExploringOn pause, story onlyEthics pass
Country colour: pink where we travel, blue where we are exploring or refer, grey for story only.
Canada
Colombia
Costa Rica
Faroe Islands
India
Indonesia
Japan
Malaysia
Maldives
Mexico
Oman
Peru
Philippines
TaiwanRead more about the pelagic thresher
Sources for this page
- Florida Museum of Natural History, 2026
- FishBase, 2018
- IOTC, 2025
- Oliver et al., 2011, PLOS ONE
- Oliver et al., 2013, PLOS ONE
- ISRA factsheet, Monad and Kimud Shoals
- DAN Alert Diver, Malapascua, 2025
Facts checked 26 September 2026. Photos: Unsplash licence, or Creative Commons as shown on each photo.
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