Alopias superciliosus
Alopias superciliosus·Large·Ovoviviparous·Vulnerable
The bigeye thresher (Alopias superciliosus) is a species of thresher shark found in temperate and tropical oceans worldwide, distinguished by its enormous, upward-rotating eyes and a tail fin with an elongated upper lobe. It is known for its diel vertical migration, hunting in low light conditions by stunning prey with its tail. This ovoviviparous shark is assessed as Vulnerable by the IUCN due to over-exploitation.
Key Facts
- ›Possesses exceptionally large eyes, up to 10 CM (3.9 in) across, adapted for low-light hunting.
- ›Undertakes a diel vertical migration, moving from deep waters during the day to surface waters at night.
- ›Uses its long upper tail fin lobe to stun prey before capture.
- ›Reproductively, it is ovoviviparous, with developing fetuses feeding on infertile eggs produced by the mother.
- ›Males mature around 9-10 years old, and females around 12-14 years old.
- ›Assessed as Vulnerable by the IUCN due to susceptibility to over-exploitation.
Bigeye Thresher
Western Atlantic Ocean, Eastern Atlantic Ocean, Western Indian Ocean, Pacific Ocean
Oceanic, Continental Shelf, Coastal
- Enormous Eyes, Up To 10 Cm Across, Taller Than Wide, With A Bulbous Upper Portion.
- Keyhole-Shaped Eye Sockets That Allow Upward Rotation.
- Two Distinctive Lateral Grooves Extending From Above the Eyes To Over the Gill Slits.
- Moderately Long and Bulbous Snout.
- Teeth Are Moderately Large With A Single, Narrow Cusp.
- Upper Lobe of Caudal Fin Is Nearly Half the Body Length.
- Large Pectoral Fins With A Curved Anterior Margin and Broad Tips.
- First Dorsal Fin Placed Further Back Than In Other Threshers.
- Coloration Is Deep, Metallic Violet To Purplish-Brown Above and Creamy White Below.
- Most Adults Are 3.3–4.0 M Long and Weigh 160 Kg .
- Largest Known Specimen Measured 4.9 M and Weighed 364 Kg .
Carnivore, Piscivore, Cephalopodivore
- Conducts Diel Vertical Migrations, Moving From Deep To Surface Waters Daily.
- Daytime Swimming Patterns Are Usually Steady, While Nighttime Patterns Involve Slow Ascents and Rapid Descents.
- Likely Competes Ecologically With the Blue Shark.
Larger Sharks, Marine Mammals
- Enormous, Vertically Oriented Eyes.
- Deep Lateral Grooves On the Head Above the Eyes.
- Upper Lobe of the Caudal Fin Is Exceptionally Long, Making Up Nearly Half the Total Length.
About Alopias superciliosus
Bigeye Thresher Shark (Alopias superciliosus)
The bigeye thresher, scientifically known as Alopias superciliosus, is a distinctive species of thresher shark found in temperate and tropical oceans worldwide. It is immediately recognizable by its exceptionally large eyes, which are adapted for hunting in low-light conditions and can be rotated upward. These sharks also possess a pair of unique deep grooves on the top of their heads and a remarkably elongated upper lobe of the tail fin, which can constitute nearly half of their total body length.
Biology and Behavior
This species is notable for undertaking a diel vertical migration, descending to deep waters during the day and ascending to shallower surface waters at night to feed. To cope with temperature fluctuations during these migrations, it has a specialized vascular system (rete mirabile) around its sensitive brain and eyes. The bigeye thresher's diet consists primarily of fish and squid, which it stuns with powerful, whip-like strikes of its tail before capture. Its large eyes provide binocular vision, aiding in aiming these strikes.
Reproduction and Life Cycle
Bigeye threshers are ovoviviparous, giving birth to live young, typically litters of two pups. The developing embryos are oophagous, feeding on infertile eggs produced by the mother within the uterus. Males generally mature around 9-10 years of age, while females mature later, between 12-14 years. The maximum lifespan is estimated to be around 19-20 years.
Distribution and Habitat
The bigeye thresher has a broad, circumtropical distribution, inhabiting areas over continental shelves and in the open sea, though they can occasionally be found in shallower coastal waters. They are typically found in water temperatures ranging from 16–25 °C but can tolerate depths down to 723 meters where temperatures are much colder.
Conservation and Human Interaction
This shark is caught by commercial fisheries for its meat, skin, fins, and liver oil, although its meat is not highly regarded. Due to its susceptibility to over-exploitation, the bigeye thresher shark has been assessed as Vulnerable by the International Union for Conservation of Nature (IUCN). It is rarely encountered by divers and poses no danger to humans. Recreational anglers also pursue this species.
Source: Wikipedia ↗
Frequently Asked Questions
What are the most distinctive features of the bigeye thresher shark?
The bigeye thresher is most recognizable by its enormous eyes, which are significantly larger than those of other thresher sharks and can be rotated upwards. It also has a pair of distinctive grooves on the top of its head and a tail fin with a greatly elongated upper lobe.
Where does the bigeye thresher shark live?
This species has a virtually circumtropical distribution, meaning it can be found in temperate and tropical oceans around the globe. Its range includes areas in the western and eastern Atlantic, the western Indian Ocean, and the Pacific Ocean.
How does the bigeye thresher hunt?
The bigeye thresher hunts by using its long upper tail fin lobe to stun prey with whip-like strikes. Its large, upward-oriented eyes help it to better aim these strikes, especially in dim light conditions.
What is the reproductive strategy of the bigeye thresher?
Bigeye threshers are ovoviviparous, meaning they give birth to live young. The developing embryos are nourished by a yolk sac initially and then by consuming infertile eggs produced by the mother within the uterus.
What is the conservation status of the bigeye thresher?
The bigeye thresher shark is assessed as Vulnerable by the International Union for Conservation of Nature (IUCN). This status reflects its high susceptibility to over-exploitation by fisheries.
Does the bigeye thresher migrate?
Yes, the bigeye thresher conducts a diel vertical migration, moving from deep waters during the day to shallower surface waters at night to feed. There is also evidence of longer-distance movements, with one individual tracked moving over 2,700 km.
Related Cartilaginous fish species
Alopias vulpinus
The common thresher (Alopias vulpinus) is the largest species of thresher shark, characterized by its exceptionally long, whip-like upper caudal fin lobe used for hunting. Found in tropical and temperate waters worldwide, it inhabits both coastal areas and the open ocean, preferring cooler temperatures. Despite its size, it is generally timid and poses minimal danger to humans, though it is highly valued by commercial and recreational fisheries.
Alopias pelagicus
The pelagic thresher (Alopias pelagicus) is a species of thresher shark found in tropical and subtropical Indian and Pacific Oceans, known for the elongated upper lobe of its caudal fin. It is distinguished from its relatives by the dark coloration over the bases of its pectoral fins, unlike the white found in the common thresher. This species typically inhabits open ocean waters but can occasionally be found near coastal areas.
Aetobatus narinari
The spotted eagle ray (Aetobatus narinari) is a species of cartilaginous fish found in tropical waters globally, though recent authorities have restricted its range to the Atlantic Ocean. Distinguished by its dark dorsal surface adorned with white spots or rings and a long tail with venomous stingers, this ray primarily inhabits shallow coastal areas near coral reefs and bays. They are ovoviviparous, with females retaining eggs internally and giving birth to live young.