Istock

Basking Shark

About the Basking Shark

The basking shark (Cetorhinus maximus) is the second-largest fish in the world, reaching lengths of up to 40 feet (12 metres). Known for its massive size and slow, gentle nature, this shark feeds exclusively on plankton and is commonly seen swimming near the ocean surface with its large mouth open, "basking" in the sun.

Basking sharks can reach lengths of up to 40 feet (12 metres) and weigh as much as 5 tons, making them the second-largest shark after the whale shark.

They have a conical snout, large gill slits that almost encircle the head, and distinctive grey or brownish skin, often with a rough texture and occasional white patches.

Like whale sharks, basking sharks are filter feeders and feed exclusively on plankton, small fish, and invertebrates. They swim with their mouths open to take in water, then use specialised gill rakers to trap food and filter out excess water.

These sharks often swim slowly near the surface with their mouths wide open, appearing to "bask" in the sun. This behaviour is part of their feeding strategy, allowing them to take in large amounts of plankton-filled water.

They are generally solitary but are sometimes seen in groups, especially in feeding areas during plankton blooms. Group sightings of up to 100 individuals have been reported in places like the United Kingdom.

Basking sharks have a slow reproductive rate. They reach sexual maturity between the ages of 12 and 20 years and give birth to live young after a long gestation period (potentially around 2–3 years).

Very little is known about their mating behaviour, and their low reproductive rate makes population recovery challenging.

Commonality of Basking Sharks

Basking sharks are rare and have a patchy distribution across their range, even though they inhabit temperate waters worldwide. Their numbers are difficult to estimate due to their wide-ranging and migratory behaviour, and their populations have been heavily impacted by past overfishing.

Protection & Threats

The IUCN lists the basking shark as Endangered, primarily due to overfishing, bycatch, and habitat disturbance. Historically, they were hunted for their liver oil, fins, and cartilage. Today, they are protected in some countries, but accidental capture in fishing gear remains a significant threat.

Climate Change

Basking sharks prefer cooler waters; rising ocean temperatures could push their suitable habitat further north. This could lead to changes in their distribution, potentially making them more common in colder areas while diminishing their presence in historically populated regions.

As the oceans warm, basking sharks may alter their migratory patterns to follow cooler waters and abundant plankton blooms. This could result in increased sightings in new areas, while they may become less common in traditional habitats.

As ocean temperatures rise and acidification occurs, phytoplankton communities may shift, potentially leading to a decline in the types of plankton available to basking sharks. Changes in plankton diversity could affect the entire marine food web.