The bigeye thresher shark is a species of thresher shark found in temperate and tropical waters worldwide. Its elongated, sickle-shaped upper tail fin and large eyes distinguish it.
However, so many other facts are there about this shark regarding its diet, habitat, anatomy, and so on. And in this article, I will discuss all of them in detail.
Bigeye Thresher Shark: At a Glance
| Category | Information |
| Common Name | Bigeye Thresher Shark |
| Scientific Name | Alopias superciliosus |
| Size | Up to 13 feet long (Maximum recorded 16 feet |
| Weight | Up to 350 lbs |
| Habitat | temperate and tropical oceans around world |
| Distribution | Atlantic and Indo-Pacific Oceans |
| Diet | Small fish, squid, and octopus |
| Lifespan | Estimated up to 20 years |
| Reproduction | oophagy viviparity |
| Conservation Status | Vulnerable (IUCN) |
The Bigeye Thresher Shark, scientifically known as Alopias superciliosus, is a unique and fascinating species of Pelagic Thresher Shark characterized by its distinctive, large eyes and long, whip-like tail.
A part of the family Alopiidae, it is typically found in the deep waters of tropical and subtropical oceans, traversing various depths from the surface down to 500 meters (1,640 feet).
10 Fun Facts: Bigeye Thresher Shark
- The bigeye thresher shark’s large eyes are its most striking feature, but they have poor vision.
- The shark’s elongated upper caudal fin accounts for almost half its entire body length and is an innovative hunting tool, stunning or killing prey with underwater shock waves.
- The shark has a complex immune system that helps protect it from pathogens and environmental toxins.
- Bigeye thresher sharks have a diverse diet consisting of small pelagic fishes, cephalopods, and crustaceans.
- The shark’s skeletal system predominantly comprises cartilage, which allows for greater flexibility and maneuverability than bony fish.
- The shark’s open circulatory system allows it to remain active at depths where temperatures would be too low for most other fish species.
- Bigeye thresher sharks can swim continuously for long periods because their muscles are mainly composed of red muscle fibers with a high capacity for sustained aerobic activity.
- The shark’s gill slits act as filters to trap particles present in the water before they enter its main respiratory tract.
- The biggest recorded bigeye thresher shark weighed as much as 350 pounds.
- The conservation status of the bigeye thresher is “Vulnerable.”
Anatomy of Bigeye Thresher Shark
Here’s an overview of the anatomy of the bigeye thresher shark:
Physical Attributes and Adaptations
The Bigeye Thresher Shark is a large species, boasting a length ranging from 11 to 13 feet (with the largest recorded at 16 feet) and typically weighing around 160 kilograms or 350 pounds. However, the biggest on record was as heavy as 759.8 pounds.
Also Read: Pelagic Thresher Shark: Habitat, Diet, Anatomy & Fun Facts
Its most striking feature is its large eyes, proportionally much bigger than other shark species. These eyes are positioned on the sides of its head and are upraised, allowing the shark to scan its environment for potential prey. But, unfortunately, it has poor eye vision.
Skeletal System
The bigeye thresher shark has a skeleton predominantly of cartilage, allowing for greater flexibility and maneuverability than bony fish. The skeletal system consists of several vertebrae along its spinal column and specialized fins that provide stability and propulsion.
Its pectoral fins are particularly large, extending significantly beyond its head when fully extended.
The Bigeye Thresher Shark is known for its elongated upper caudal fin, accounting for almost half of its entire body length. This whip-like tail is an innovative hunting tool, enabling the shark to stun or kill its prey by moving it at high speeds, creating underwater shock waves.
Muscular System
The bigeye thresher shark has two sets of muscles; one set is used for swimming forward, while the other provides lateral thrust during turns. These muscles are mainly composed of red muscle fibers, which have a high capacity for sustained aerobic activity and allow the shark to swim continuously for long periods.
Digestive System
The digestive system includes several organs that work together to process food. These include the mouth, esophagus, stomach, liver, gallbladder, pancreas, small intestine, and rectum.
Rows of sharp teeth chew food before being swallowed whole or partially digested in the stomach before passing into the intestines for further digestion. Bile produced in the liver aids in digestion by breaking down fats into fatty acids that can be absorbed by cells in the intestines.
Circulatory System
The bigeye thresher shark possesses an open circulatory system consisting primarily of two pumps; one to supply oxygen-rich blood to tissues throughout its body and another to remove carbon dioxide-rich blood from those same tissues back to its gills for oxygenation again.
This unique arrangement allows it to remain active at depths where temperatures would be too low for most other fish species due to reduced oxygen levels in their bloodstream.
Respiratory System
Like all other sharks, the bigeye thresher has five pairs of gill slits on either side of its head, allowing it to take up dissolved oxygen from seawater as it passes through them on inhalation (breathing).
Its internal “branchial basket” structures act as filters trapping any particles present in the water before they enter its main respiratory tract, preventing them from damaging delicate tissue structures within its gills or lungs.
Nervous System
The bigeye thresher shark has electrical-sensing organs (ampullae de lorenzini) all over its body. It can also use traditional senses like sight, smell, and hearing to find its way or find nearby prey.
However, because it has poor eyesight, it often relies on these electroreceptors when hunting at night or in murky water.
Also Read: Sicklefin Lemon Shark: Habitat, Diet, Anatomy & Fun Facts
Immune System
The bigeye thresher shark has a complex immune system that helps protect it from pathogens and environmental toxins. This system includes particular proteins called antibodies that target and neutralize harmful agents like bacteria, viruses, or fungi that are trying to get into its body by recognizing their unique properties and then binding to them so they can’t do any harm.
In addition, the shark also has a very efficient system for removing waste and toxins from its body, which helps to maintain optimal health and performance.
What do Bigeye Thresher Sharks eat?
Bigeye Thresher Sharks possess a diverse and fascinating diet, primarily consisting of small pelagic fishes, cephalopods, and crustaceans. Being an opportunistic predator, this shark species thrives on multiple food sources to survive and maintain their energy levels in the deep oceanic and continental shelf regions where they often reside.
Fish make up a significant portion of the Bigeye Thresher Shark’s diet. These sharks commonly hunt species such as mackerel, bluefish, herring, anchovies, sardines, and lanternfish.
These small, schooling fish are abundant in the range of habitats that the Bigeye Thresher Shark inhabits, providing a readily available and energy-rich food source. Moreover, their diet also comprises moderately larger fish species like bonitos and tunas, depending on the geographical location and availability.
Cephalopods are another vital constituent of their diet, including squids and octopuses. From oceanic squids to smaller coastal species like the market squid, the Bigeye Thresher Shark preys upon numerous cephalopod varieties.
The sharks are known to dive as deep as 500 meters into the mesopelagic zone to hunt for larger, deep-sea squids, demonstrating their adaptability in pursuing prey at varying depths.
Crustaceans play a lesser but still important role in the Bigeye Thresher Shark’s diet. They often consume shrimp, krill, and small crabs, exploiting these rich nutrient sources whenever they are available.
The Bigeye Thresher Shark employs a unique hunting strategy to capture their prey, utilizing their elongated caudal fin, which can measure up to half its body length. They use their tail fin in a whip-like motion to stun or injure surrounding schools of fish, making the prey easier to catch and consume.
This specialized hunting behavior allows them to effectively target fast-swimming prey, giving them an edge over other predatory species in sustaining their varied diet of pelagic fishes, cephalopods, and crustaceans.
Where Do Bigeye Thresher Sharks Live?
Primarily, Bigeye Thresher Sharks inhabit the open ocean (pelagic environment) and are frequently found in coastal waters off the shelves of continental and insular regions. However, they also occupy the deep waters of oceanic islands and seamounts.
Their vast distribution stretches across the Atlantic, Indian, and Pacific Oceans, with established populations in the Eastern and Western Pacific, the Western Indian Ocean, and the Eastern Atlantic Ocean.
Some of their known locations include the western and eastern coasts of the United States, the Gulf of Mexico, the Mediterranean Sea, Taiwan, Japan, Australia, New Zealand, South Africa, and the surrounding areas of the Indian Ocean islands.
Bigeye Thresher Sharks can be found anywhere between the surface of the ocean and 500 meters (1650 feet) down, but their preferred depths are usually somewhere between 50 to 350 meters (160-1150 feet).
Also Read: Kitefin Shark: Anatomy, Diet, Habitat & Facts
Their flexibility in terms of depth selection is mostly thanks to their prey-hunting tactics as well as their sensitivity toward temperature fluctuations. Despite this, one particular specimen was reported at a staggering 723-meter depth – a record-breaking dive.
They tend to favor water temperatures of around 16°C to 20°C (61°F to 68°F), which indicates both a certain level of tolerance to temperature fluctuations, as well as their adaptability to changing environments.
The selection of habitats by the Bigeye Thresher Shark is also influenced by factors such as food availability, reproduction, and predator avoidance.
For example, these sharks prefer to inhabit environments abundant in prey, including small to medium-sized pelagic fish like mackerel, herring, and squid. They are also known for their selective migrations, as they move to specific nursery grounds for giving birth, with potential mating in areas suitable for both temperature and prey accessibility.
How Long Does a Bigeye Thresher Shark Live?
A Bigeye Thresher Shark can live up to 20 years, although some have been recorded as living up to 25 years in the wild. They are relatively slow to mature, with males not reaching maturity until they are 10 years old and females not maturing until 12 years old.
On average lifespan, Bigeye Thresher Sharks are among the longest-living sharks, with many outlasting their littermates by several decades. This is due to their low fecundity rate; they produce fewer offspring than other shark species and rely heavily on their long lifespans for population stability.
There have also been reports of Bigeye Thresher Sharks returning to the same area year after year when migrating, indicating that they may have a degree of fidelity to certain areas.
How Do Bigeye Thresher Sharks Reproduce?
Bigeye thresher sharks reproduce through a unique and fascinating method called oophagy viviparity. This reproduction method is remarkable, as it involves the developing embryos feeding on a steady supply of tiny, unfertilized eggs as their primary source of nutrition while still inside the uterus of the mother shark.
Mating among bigeye threshers occurs via internal fertilization, where the male shark inserts one of its claspers, modified pelvic fins, into the female’s cloaca to transfer sperm. Once the eggs have been fertilized, they become encased in a thin membrane, allowing embryonic development to commence inside the female’s uterus.
As the embryos grow and develop, the mother shark provides a consistent supply of non-fertilized eggs, known as trophic eggs or nutritive eggs, for the embryos to consume. This process of oophagy, or egg eating, enables the developing sharks to gain essential nutrients required for growth, making them substantially larger and stronger before entering the outside world.
This reproduction method is advantageous for bigeye thresher sharks, as it ensures the offspring have a higher chance of survival as they are born life and relatively large compared to other sharks, which increases their ability to protect themselves and forage for food independently.
Moreover, bigeye threshers exhibit reproductive seasonality, with mating occurring during the year’s warmer months. This seasonal pattern ensures that the birth of their pups aligns with an abundance of food sources, providing the newborn sharks with maximum nourishment opportunities to support their survival and growth.
Are Bigeye Thresher Sharks Dangerous to Humans?
Contrary to some assumptions and the inherent fear of sharks, the bigeye thresher shark poses little to no threat to humans. As it turns out, most fear surrounding sharks stems from sensationalized portrayals in movies and popular media rather than the animals’ reality.
The following discussion delves into more detail, exploring the bigeye thresher shark’s behavior, a rarity in human encounters, and the scarcity of attacks linked to this species.
To begin with, a key factor lessening the bigeye thresher shark’s danger to humans is its habitat depth, as these sharks predominantly dwell in deep waters, far from popular swimming or diving spots.
They typically inhabit depths up to 500 meters. Due to these vast depths, interactions between humans and bigeye thresher sharks are exceedingly rare, making the likelihood of any conflict minimal.
Their diet also contributes to their lack of danger to humans. Bigeye thresher sharks primarily consume smaller fish, such as sardines, anchovies, mackerel, and squid. Using their long, whip-like tail as a tool, they stun and capture their prey by creating shockwaves.
This unique hunting technique not only displays this species’ fascinating capabilities but also highlights their focus on consuming smaller marine life rather than looking for more substantial sources of food, such as humans.
Furthermore, there have been no recorded instances of bigeye thresher sharks attacking humans. This fact alone should alleviate much of the fear surrounding these majestic creatures.
In the case of thresher sharks in general, there has only been one documented attack on a person, which resulted from the individual provoking the shark by grabbing its tail. Notably, that particular incident involved a common thresher shark (Alopias vulpinus), not the bigeye species.
Consequently, it clearly indicates that humans interacting with bigeye thresher sharks have little to fear if they maintain a respectful distance and do not provoke the animals.
What Is the Conservation Status of Bigeye Thresher Sharks?
The bigeye thresher shark (Alopias superciliosus) is a species of thresher shark that is listed as “Vulnerable” on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. This classification indicates that the species is likely to become endangered unless conservation efforts are implemented.
The primary reason behind the vulnerable status of bigeye thresher sharks is overfishing. Thresher sharks, including the bigeye thresher, are popular targets for commercial and recreational fisheries worldwide.
They are caught for their meat, liver oil, and fins, which are highly valued in Asian markets for shark fin soup. Bigeye thresher sharks are also often caught as bycatch in longline and purse seine fisheries targeting other species like tuna and swordfish.
Habitat degradation, marine pollution, and the impacts of climate change further exacerbate the threats faced by bigeye thresher sharks. With a low reproductive rate, these sharks are highly susceptible to population decline, making it difficult for them to recover from the pressure imposed by overfishing and environmental changes.
To ensure the survival and conservation of bigeye thresher sharks, several measures need to be taken:
1. Strengthening Fishery Regulations: Implementing strict catch limits, size limits, and gear restrictions can help reduce the pressure on thresher shark populations. This can be achieved through both national legislation and international cooperation, such as regional fisheries management organizations (RFMOs).
2. Bycatch Reduction: Encouraging the adoption of bycatch mitigation measures in fisheries that incidentally catch bigeye thresher sharks will help reduce their mortality rates. Methods like using circle hooks, which are less likely to catch sharks, and implementing exclusion devices in fishing gear can help minimize bycatch.
3. Species Monitoring: Consistent monitoring of bigeye thresher shark populations is critical in evaluating the effectiveness of conservation efforts and adjusting them as necessary. Data collected through surveys, tagging programs, and citizen science projects can help inform management decisions and strategies.
4. Habitat Protection: Conserving and restoring the habitats that bigeye thresher sharks rely on for breeding, feeding, and migration is essential for their long-term survival. This can be achieved by designating marine protected areas (MPAs) and implementing policies to reduce pollution and preserve critical habitats from destruction.
5. Public Education and Awareness: Raising public awareness about the vulnerable status of bigeye thresher sharks can help garner support for conservation efforts. Campaigns and educational programs that emphasize the ecological importance of these sharks and the threats they face can encourage responsible consumption practices and support conservation policies.
Conclusion
You know everything about the bigeye thresher sharks. I have discussed in this article the characteristics, habitat, diet, and conservation status of the bigeye thresher shark.
Moreover, I have also discussed the measures that need to be taken to conserve this species. Public education and awareness play a significant role in increasing support for conservation efforts.
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