Squalidae

Squalus acanthias

Squalus acanthias2

Mandarin dogfish2

Squalidae, commonly known as dogfish sharks, is a family of sharks belonging to the order Squaliformes. This family is characterized by its two dorsal fins, each with smooth spines, lack of an anal fin, and the presence of a nictitating membrane over the eyes, although it is often small or absent in some species. The Squalidae family is diverse, with species found in temperate and tropical oceans worldwide, ranging from shallow coastal waters to deep-sea environments.

Description

Dogfish sharks are generally small to medium in size, although some species can reach lengths of up to 4 meters (13 feet). They have slender, elongated bodies, and their skin is covered in dermal denticles, which provide protection and aid in swimming. The coloration of these sharks can vary significantly among species, from solid colors to complex patterns, which serve as camouflage in their respective habitats.

Habitat and Distribution

Members of the Squalidae family are found in a wide range of aquatic environments. While some species prefer cold, deep waters, others inhabit warmer, shallower regions. They are known to occur in both coastal and oceanic zones, from the surface to depths of over 2,000 meters (6,600 feet). Their distribution is global, with species found in the Atlantic, Pacific, and Indian Oceans, as well as in the Mediterranean and Black Seas.

Diet

The diet of dogfish sharks primarily consists of fish, cephalopods, and crustaceans. They are opportunistic feeders, often hunting in packs to take down prey larger than themselves. Some species have specialized feeding habits; for example, the Spiny Dogfish (Squalus acanthias) is known to feed extensively on squid and other mollusks.

Reproduction

Squalidae exhibit a variety of reproductive strategies, including oviparity (egg-laying) and viviparity (live birth). Many species are ovoviviparous, where the eggs hatch inside the female's body, and the young are born fully developed. Reproductive cycles can be long, with gestation periods lasting up to two years in some species, such as the Spiny Dogfish.

Conservation

Several species within the Squalidae family are of conservation concern due to overfishing, habitat loss, and pollution. The Spiny Dogfish, for example, has been heavily targeted by commercial fisheries for its meat, liver oil, and fins. As a result, its population has declined significantly in some areas, leading to it being listed as Vulnerable by the International Union for Conservation of Nature (IUCN). Conservation efforts are underway to protect these sharks, including fishing regulations and the establishment of marine protected areas.

Notable Species

• Spiny Dogfish (Squalus acanthias)
• Greenland Shark (Somniosus microcephalus)
• Longnose Velvet Dogfish (Centroscymnus crepidater)

See Also

• Shark
• Squaliformes
• Conservation status

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