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Blue shark

life science Maturity 5-7 Next article →

The blue shark, scientifically known as Prionace glauca, is a species of requiem shark. It belongs to the family Carcharhinidae. These sharks are common in the deep, temperate, and tropical oceans of the world. They are considered one of the most abundant pelagic sharks, which means they live in the open ocean.

Blauhai (128648419) (cropped)
Blauhai (128648419) (cropped)

Because they are frequently caught as bycatch in nets and longlines, the IUCN lists them as Near Threatened. Understanding these sharks helps us learn how large predators move through the global ocean.

Physically, the blue shark has a slender, elongated body. They use a method called countershading to hide from prey and predators. Their upper bodies are a deep blue color, while their sides are lighter. Their undersides are white. This coloring helps them blend into the light from above and the darkness below.

Tiburón azul (Prionace glauca), canal Fayal-Pico, islas Azores, Portugal, 2020-07-27, DD 24
Tiburón azul (Prionace glauca), canal Fayal-Pico, islas Azores, Portugal, 2020-07-27, DD 24

Males typically grow to about 2 meters in length. Females are usually larger, often reaching 3 meters. Some reports claim much larger sizes, but scientists have not documented them. Large females can weigh over 200 kilograms.

Blue sharks possess a sophisticated sensory system to navigate the deep sea. They use vision, hearing, chemoreception, and electroreception to perceive their environment. Their eyes are positioned on the sides of their heads. This provides a wide visual field of up to 360 degrees vertically.

A Blue shark at the Uminomori Aquarium in Sendai
A Blue shark at the Uminomori Aquarium in Sendai

They also use a lateral line, which is a mechanosensory structure. This allows them to detect particle motion and water vibrations. This helps them sense the speed of currents and the movement of nearby animals.

One of their most unique tools is the ampullae of Lorenzini. These are specialized electroreceptors that develop from the lateral line. Each ampulla consists of a tiny pore on the skin connected to a small bulb. These sensors allow the shark to detect weak electrical fields. They use this to locate prey and avoid predators.

Prionace glauca in an aquarium
Prionace glauca in an aquarium

They can even sense the Earth's magnetic field. This helps them maintain a straight course while migrating for hundreds of kilometers.

Reproduction in blue sharks involves a process called viviparity. This means the females give birth to live pups rather than laying eggs. They use a yolk-sac placenta to nourish the developing young. A single litter can be very large, ranging from 25 to over 100 pups.

Juvenile blue shark (cropped)
Juvenile blue shark (cropped)

The gestation period lasts between 9 and 12 months. After birth, the pups are moved to specific nursery areas. These areas are located outside of adult regions to keep the young safe while they grow.

Blue sharks are highly migratory animals that travel vast distances. They move through both temperate and tropical waters. Their movements are often influenced by seasonal changes and the availability of food.

Blue shark, capture production, thousand tonnes, 1950-2022
Blue shark, capture production, thousand tonnes, 1950-2022

They prefer water temperatures between 14 and 16 degrees Celsius. However, they can survive in water ranging from 8.5 to 17.5 degrees Celsius. Their activity levels change depending on the time of day. During the day, they swim at a mean rate of 1.2 kilometers per hour. At night, they become more active, swimming at a mean rate of 1.8 kilometers per hour.

Fossil evidence shows that blue sharks have existed for a very long time. The earliest fossil teeth were found in Sri Lanka from the Miocene epoch. Other fossils have been discovered in Chile, Italy, and possibly Belgium. These findings help scientists understand how the species has changed over millions of years. Today, we believe these sharks can live for up to 20 years. They play a vital role in the ocean ecosystem by feeding on small fish and squid.

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🖼️ Images & Media (7)
File:Blauhai (128648419) (cropped).jpeg
Blauhai (128648419) (cropped).jpeg
File:Juvenile blue shark (cropped).jpg
Juvenile blue shark (cropped).jpg
File:Tiburón azul (Prionace glauca), canal Fayal-Pico, islas Azores, Portugal, 2020-07-27, DD 24.jpg
Tiburón azul (Prionace glauca), canal...
File:Pamtu - blue shark meat on sale in Malta (cropped).jpg
Pamtu - blue shark meat on sale in Malta...
File:Blue shark, capture production, thousand tonnes, 1950-2022.svg
Blue shark, capture production, thousand...
File:A Blue shark at the Uminomori Aquarium in Sendai.jpg
A Blue shark at the Uminomori Aquarium in...
File:Prionace glauca in an aquarium.jpg
Prionace glauca in an aquarium.jpg
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