Species Profile: Basking Shark

Basking Shark

The Basking Shark

The basking shark is a large, slow-moving fish. It’s known to swim slowly near

the surface of the water in good weather conditions, hence its name. This shark is so large that it comes second in size only to the whale shark.

1. Scientific Name

Cetorhinus maximus

2. Scientific Classification

Basking sharks are the only members of the family Cetorhinidae, which is part of the order Lamniformes, an order of mackerel sharks.

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Chondrichthyes
  • Order: Lamniformes
  • Family: Cetorhinidae
  • Genus: Cetorhinus
  • Species: Maximus

3. Life Expectancy

Basking sharks have a life expectancy of about 50 years.

4. Average/Maximum Length

Adult basking sharks typically reach lengths of 20-26 feet (6-8 metres).The maximum length recorded is 40 feet. Only the whale shark surpasses it in weight and length.

5. Average/Maximum Weight

They weigh approximately 5.2 tons (5, 200 kg) with the maximum weight recorded so far being 21 tons (21, 000 kg). The basking shark has an enormous liver that accounts for nearly 25% of its body weight. This liver has a high squalene content, which helps the fish maintain almost neutral buoyancy.

6. Maximum Swimming Speed

Maximum speed is just three miles per hour (4.8 km/h).

7. Danger To Humans

Basking sharks are generally harmless to humans and tolerant to boats and divers. However, contact with their skin should be avoided as there have been reports of their dermal denticles inflicting damage on scientists and divers.

8. Reproduction Details

Basking sharks engage in a range of courtship behavior such as parallel swimming, nudging and biting. Males attain sexual maturity between the ages of 12-16 years whereas females are thought to reach maturity at around 20 years. Only one pregnant female basking shark has ever been studied. She gave birth to five live pups and one stillborn. The pups ranged from 4.5 – 6 feet (1.5 – 2 metres) in length.

This shark is believed to be ovoviviparous, with a gestation period of three or more years. The pups develop in the eggs and feed off other embryos or unfertilized eggs. Juvenile sharks have long, hook-like snouts that are believed to help them feed in the womb and after birth by increasing the flow of water through their mouths.

9. Diet

Basking sharks are easily recognizable because of their massive size, bulbous conical snouts, tremendously large mouths that open up to 3.3 feet wide (1 m), large gill slits that almost encircle their heads, and crescent shaped caudal fins. Inside their mouths, they have several rows of small hook-shaped teeth.

The basking shark mainly feeds on zooplankton. It keeps its mouth open while it swims to take in a large flow of water. The gill rakers located in its gill slits strain the plankton – including small fish and crustaceans, fish eggs and larvae, and invertebrate larvae – from the vast quantity of water flowing into its open mouth. They can filter up to 2,000 tons of water every hour. Every few minutes, it swallows the food that has piled up in its gills.

Basking sharks cover large distances to look for food at their slow, leisurely speed.

10. Alternative Names Of The Basking Shark

  • Elephant shark
  • Bone shark
  • Big mouth shark
  • Hoe-mother
  • Sunfish
  • Sailfish

11. Population And Conservation Status

The population of basking sharks is declining worldwide. They have been fished for several centuries for their meat, hide, and oil. Their slow growth rate, long maturation time and gestation period have made them vulnerable to overfishing. The IUCN Red List has categorized them as “Vulnerable” species, implying they could become extinct in the near future.

The threats to their survival have put some countries on high alert. The species has been placed under protection in the territorial waters of countries like the United States, New Zealand, and the United Kingdom. Commercial fishing of these sharks is also banned in many regions.

12. Ancestry And History

Based on DNA evidence and physical similarities, basking sharks are classified as Lamniformes or mackerel sharks. Therefore, they share a common ancestor with the great white sharks, megamouths, makos, threshers and goblin sharks. Fossil records suggest mackerel sharks first appeared on the planet 100 million years ago. However, fossil evidence traces basking sharks back to around 30 million years.

13. Distribution And Habitat

The basking shark inhabits all of the world’s oceans but prefers arctic and temperate waters. It can be found in the western Pacific, around the Koreas, Japan, China, New Zealand, and western and southern Australia. In the eastern Pacific, the shark is found from Ecuador down to Chile and between the Gulfs of Alaska and California. Other frequent sightings have been in the eastern Atlantic, from Norway and Iceland to Senegal as well as parts of the Mediterranean. It is found in the coastlines of Brazil to Argentina and Newfoundland to Florida in the western Atlantic.

The habitat of basking sharks is determined by food availability. Whale sharks keep close to the ocean surface during the warmer months. They are known to enter bays, estuaries as well as venture offshore. In the winter, they shed and regrow their gill rakers and at the same time they’ll move into the deeper waters to follow the seasonal plankton migration.

Shark scientists are still working hard to get more information about the biology, ecology, and life history of these giant fish.

References

http://sharkopedia.discovery.com/types-of-sharks/basking-shark/#introduction

https://www.flmnh.ufl.edu/fish/discover/species-profiles/cetorhinus-maximus

http://www.sharksider.com/basking-shark/

http://www.sharks-world.com/basking_shark/

http://www.iucnredlist.org/details/4292/0

https://owlcation.com/stem/Basking-Sharks

http://dinoanimals.com/animals/basking-shark-the-second-largest-fish/

Photo Credit

https://commons.wikimedia.org/wiki/File:Cetorhinus_maximus_by_greg_skomal.JPG


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