The most distinctive features of this species are its three-cusped teeth, the white blotch at the aft base of its first dorsal fin, and the two pairs of lateral keels on its tail.

Most commonly found over food-rich banks on the outer continental shelf, it makes occasional forays both close to shore and into the open ocean to a depth of 1,360 m (4,460 ft).

[3][6] In 1816, French naturalist Georges Cuvier placed the porbeagle into its own subgenus, Lamna, which later authors elevated to the rank of full genus.

[7] Several phylogenetic studies, based on morphological characters and mitochondrial DNA sequences, have established the sister species relationship between the porbeagle and the salmon shark (L. ditropis),[8][9] which occurs in place of it in the North Pacific.

[13][14][15] However, Lamna teeth that closely resemble those of the porbeagle have been found in the La Meseta Formation on Seymour Island off the Antarctic Peninsula, which date to the middle to late Eocene epoch (50–34 Mya).

Much taxonomic confusion remains regarding Lamna in the fossil record due to the high degree of variability in adult tooth morphology within species.

[18] The porbeagle is thought to have colonized the Southern Hemisphere during the Quaternary glaciation (beginning around 2.6 Mya), when the tropical climate zone was much narrower than it is today.

In deeper, stratified waters, the sharks performed a regular diel migration, spending the day below the thermocline and rising towards the surface at night.

[25] Each tooth has a strongly arched base and a nearly straight, awl-like central cusp, which is flanked by a pair of smaller cusplets in all but the smallest individuals.

Southern Hemisphere sharks are smaller and the two sexes are similar in size, with males and females attaining fork lengths of 2.0 and 2.1 m (6.6 and 6.9 ft) respectively.

[7] Its fusiform body, narrow caudal peduncle with lateral keels, and crescent-shaped tail are adaptations for efficiently sustaining speed, which have also been independently evolved by tunas, billfishes, and several other groups of active fishes.

The salmon shark and it are the thickest-bodied members of their family (length-depth ratio approaching 4.5), and consequently have the stiffest swimming style; they oscillate their tails while holding their bodies mostly rigid, which confers propulsive power with high energy efficiency, but at the cost of maneuverability.

[21][28][29] Great white sharks (Carcharodon carcharias) and killer whales (Orcinus orca) are plausible, albeit undocumented, predators of the porbeagle.

In one record, a small individual caught off Argentina bore bite marks from a copper shark (Carcharhinus brachyurus) or similar species, but whether the porbeagle was the target of attempted predation or if the two were simply involved in interspecific aggression is uncertain.

[7] Known parasites of this species include the tapeworms Dinobothrium septaria and Hepatoxylon trichiuri,[30][31] and the copepods Dinemoura producta,[32] Laminifera doello-juradoi,[33] and Pandarus floridanus.

[3][21][24] In the western North Atlantic, porbeagles feed mainly on pelagic fishes and squid in spring, and on groundfishes in the fall; this pattern corresponds to the spring-fall migration of these sharks from deeper to shallower waters, and the most available prey types in those respective habitats.

[24] During spring and summer in the Celtic Sea and on the outer Nova Scotian Shelf, porbeagles congregate at tidally induced thermal fronts to feed on fish that have been drawn by high concentrations of zooplankton.

[22][23] Hunting porbeagles regularly dive from the surface all the way to the bottom, cycling back every few hours; this vertical movement may aid in the detection of olfactory cues.

It begins to feed voraciously on yolk, acquiring an enormously distended stomach; to accommodate this, the muscles on the belly split down the middle and the skin on the abdomen stretches greatly.

From then on, the embryo relies mainly on the yolk stored in its stomach, though it may continue to feed on remaining eggs by squishing the capsules between its jaws or swallowing them whole.

[39] In the first four years of life, the annual growth rate is 16–20 cm (6.3–7.9 in) and similar in both hemispheres; thereafter, sharks from the western South Pacific begin to grow slower than those from the North Atlantic.

Its red muscles are located deep within the body, adjacent to the spine, and its lateral rete is composed of over 4,000 small arteries arranged in bands.

[1] Intensive fishing for the porbeagle dates back the 1930s, when Norway and to a lesser extent Denmark began operating longline vessels in the Northeast Atlantic.

Catches by Spanish fishers were highly variable, ranging from negligible to over 4,000 tons per year, which may reflect shifts of fishing effort into historically less-exploited waters.

Substantial numbers are caught incidentally by pelagic longline fisheries targeting more valuable species such as southern bluefin tuna (Thunnus maccoyii), swordfish (Xiphias gladius), and Patagonian toothfish (Dissostichus eleginoides), including vessels operated by Japan, Uruguay, Argentina, South Africa, and New Zealand.

[1] The rapid collapse of porbeagle stocks on both sides of the North Atlantic is often cited as archetypal of the "boom and bust" pattern of most shark fisheries.

Factors including a small litter size, long maturation time, and the capture of multiple age classes all contribute to this shark's susceptibility to overfishing.

This species benefits from bans on shark finning instituted by several nations and supranational entities, including Canada, the United States, Brazil, Australia, the European Union, and the International Commission for the Conservation of Atlantic Tunas.

[58][63] In 1995, it was included in Annex III ("species whose exploitation is regulated") of the Barcelona Convention Protocol on protected areas and biodiversity in the Mediterranean, which has not been ratified.

[58] The European Union prohibits EU vessels from fishing for, retaining, boarding, transhipping, or landing porbeagle sharks in all waters since January 2011.