porbeagle shark

© S. Campana, Canadian Shark Research Lab

Often confused for the great white shark, the smaller porbeagle shark (Lamna nasus) is also circumglobal in its range. Like other Mackerel sharks, they take vertical migrations, diving down to 600 metres to feed on fish and squid found in the open ocean. 

A robust shark, they are usually a blue-grey-black color that fades into a creamy underbelly below. With a long, pointed snout and blade-like teeth, these animals love chasing after mesopelagic fish and squid. Reaching a maximum length of 3.65 metres and maximum weight of 350 kg, this carnivore can be pretty big! Like other Lamnidae sharks, these active predators have the rete mirable, making them 'warm blooded.' Porbeagles can maintain their body temperatures 3-8ºC above the surrounding water's temperature. The rete mirable is a heat-exchange system that allows for the shark to keep the heat produced by their metabolism. This adaptation allows them to be a fast-swimming predator in cold waters.
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They are aplacental viviparous. Their developing pups are first nourished by a yolk sac, and then break free with their teeth to feed on fertilised  eggs while in the uterus (called oophagy). The gestation period lasts 8-9 months and litters average at about 5 pups. Porbeagle meat and fins are high on demand, putting pressure on fisheries within their range. Thankfully finning bans are in place! They are both taken as a target but also as bycatch, in longline, gillnet, driftnet, pelagic and bottom trawl fisheries. Porbeagle sharks are threatened by overfishing since they grow slowly, take a long time to mature (8-13 years), and produce few very young (1-5 pups per litter) after a long gestation period. Thankfully it is protected in parts of its range. The IUCN has assessed them as Vulnerable (VU).

​WHAT DID YOU LEARN ABOUT THIS ANIMAL?

GLOSSARY

• Bycatch: The part of a fishery’s catch that is made up of non-target species.​
• Gestation: The period in which a fetus develops, beginning with fertilization and ends at birth.
• IUCN: International Union for Conservation of Nature.
• Pup: Give birth to baby sharks, skates, rays or chimaeras (pups).
• Pups: Baby sharks, skates, rays, or chimaeras.
• Trawl fisheries: Fisheries that pull a fishing net through the water behind one or more boats.
• Viviparous with yolk-sac: Also known as aplacental viviparous and previously known as ovoviviparous/ovoviviparity; it is the production of eggs that are fertilised and hatch inside the female shark but the embryos lack a placental connection to the oviduct or uterus and so do not feed off the mother.

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