Porbeagle Shark
Porbeagle sharks (Lamna nasus) are part of the Lamnidae family, along with other sharks such as the salmon shark (Lamna ditropis) and the Great White shark (Carcharadon carcharias). The porbeagle’s name is believed to be a combination of “porpoise,” referring to its rounded shape, and “beagle,” for its hunting methods.
Porbeagle shark anatomy and appearance
Porbeagle sharks have muscular, fusiform bodies, with a larger midsection that tapers off into a narrow snout and tail. They can grow up to approximately three meters long and can weigh around 230 kilograms. They have a dark gray coloration dorsally and laterally, and is white ventrally. Porbeagle sharks have crescent-shaped caudal fins, along with strong keels that run along the caudal peduncle. They have long gill slits. Like other sharks in the Lamnidae family, porbeagles are endothermic and have retia mirabilia – countercurrent heat exchanges that allow sharks to retain heat. This system allows them to maintain body temperatures around 7-10 degrees Celsius higher than their surroundings. Not only does it allow them to tolerate colder temperatures, it also enables them to be faster swimmers.
Certain features help differentiate porbeagle sharks from other related shark species. Unlike other shark species, porbeagles have a white patch on the rear tip of their first dorsal fins. Porbeagles have conical snouts that tend to be more pointed compared to the salmon shark, which shares the same genus as them. Additionally, they have cusps – bumps that look like small teeth – on either side of their teeth. These cusps set them apart from Mako sharks (Isurus oxyrinchus), which are in the same family as porbeagles.
Porbeagle shark habitat
Porbeagle sharks are primarily pelagic species, but they can also be found in coastal waters. They typically inhabit colder, temperate waters with temperatures ranging from 1 to 18 degrees Celsius, and are known to venture down to depths of up to 700 meters. These sharks exhibit migratory behavior, covering distances of 1,000 to 2,000 kilometers during their migrations. While porbeagles can be found in both hemispheres, they are exclusive to the Atlantic Ocean in the Northern Hemisphere, setting them apart from the salmon shark, which is confined to the northern Pacific Ocean. In the Southern Hemisphere, porbeagles have a predominantly circumglobal distribution.
Porbeagles in the Southern Hemisphere are largely isolated from the Northern Hemisphere population, suggesting limited interaction between the two groups according to scientists.
Porbeagle shark diet
Porbeagle sharks are opportunistic hunters. As juveniles, porbeagles prey mainly on squid. However, as adults, porbeagles shift to a diet consisting mostly of bony fish, known as teleosts. Porbeagles feed on pelagic fish in the spring, such as mackerel and herring. This changes in the fall, when porbeagles tend to prey on groundfish such as hake and cod. Even as adults, squid is also a common part of their diet. Unlike other related shark species, porbeagles don’t usually eat marine mammals. Due to their persistence, many people refer to their hunting method as “dogged,” and scientists believe that led to the origin of the “beagle” portion of their name.
Porbeagle shark population
Porbeagle sharks typically live for 30 to 40 years, but some individuals can surpass 50 years. Female porbeagles reach maturity between 12 and 16 years of age, whereas males mature a bit earlier, between 6 and 10 years old. Their pregnancy lasts approximately 8 to 9 months. Porbeagles are ovoviviparous, meaning they give birth to live young without a placental connection to the embryos. The embryos nourish themselves through oophagy, consuming unfertilized eggs. Female porbeagles usually have litters of 1 to 6 pups, with an average of four, as they typically deliver 2 pups per uterus. The newborn pups measure around 60 to 80 centimeters in length.
Porbeagle shark conservation
The International Union for Conservation of Nature (IUCN) considers porbeagle sharks to be vulnerable. Despite not being as highly valued as mako sharks, they are still targeted as game fish by sport fisheries in the United States, Ireland, and the United Kingdom. In Europe, porbeagle sharks have been harvested for their meat by fisheries, while commercial fisheries in Norway and Canada also exploit them, albeit under specific regulations. Porbeagles are frequently caught incidentally, primarily through longline and net fishing methods.
Despite their similarity to well-known shark species such as the Great White shark and the Shortfin Mako shark, porbeagles seldom attack humans. They have been known to move quickly towards divers, but scientists don’t believe this is a sign of aggression. Instead, it could be a display of exploratory behavior, or simply a defensive or agonistic demonstration.
Other interesting Porbeagle shark facts
In addition to their dog-like hunting method, porbeagles are also known to have a playful behavior – much like that of a dog. They have been seen chasing other porbeagles and pushing around kelp and other floating objects, and some people speculate that they do this as a form of either socialization or communication.