- 1 Defining Features
- 2 Habitat and Range
- 3 Fisheries Conservation and Concern
- 4 Closest Relatives
- 5 Example Species in Squaliformes
- 6 Example Species in the Gulf of Maine
- 7 References
Defining Features[edit | edit source]
Squaliformes have two dorsal fins and a spine may or may not be present. Species in the order lack an anal fin and nictitating lower eyelids. They have five to seven gill slits and spiracles. Squaliformes' pectoral and dorsal fins are short relative to their body size. With the exception of the Somniosidae family (a family within the order Squaliformes known as sleeper sharks), Squaliformes tend to be small. Squaliformes are also relatively slow swimmers when compared with sharks of similar size and shape, allowing them to conserve energy that is much-needed to survive and thrive in the deep, where prey is scarce and do not move quickly due to the cold and darkness.
Habitat and Range[edit | edit source]
With a few exceptions, Squaliformes are found in deep waters, but not too far from the coasts. They can be found in both the Atlantic and Pacific Oceans. They are found in cold waters, either far north or south, and rarely spotted near the equator. Squaliformes like cold water, though there are some Squaliformes that will swim in temperate and tropical areas of the World. Squaliformes also like to live in muddy or rocky areas, and the Greenland shark can even enter brackish water. In these environments, Squaliformes feed on bottom fishes and squid. Squaliformes are a widespread order that can be found in deeper waters around the globe.
Fisheries Conservation and Concern[edit | edit source]
Concern: Because Squaliformes live in deep water, scientists do not have a lot of data on them. For many of the species of this order, we do not have enough information to determine how threatened they are. We do know that some species, like the Greenland Shark, which are killed for their meat, are near threatened, while other species of dogfish are listed as least concern. One of the most threatened species is the spiny dogfish, which is listed as vulnerable. There are also endangered members of this orderdue to fishing pressure (directed and bycatch).
Closest Relatives[edit | edit source]
Squatiniformes + [Echinoriniformes + Pristiophoriformes]
Example Species in Squaliformes[edit | edit source]
Velvet Belly Lanternshark[edit | edit source]
Etmopterus spinax[edit | edit source]
Defining Features: The Velvet Belly Lanternshark is a small reddish shark. Because it is a Squaliforme, the shark lacks an anal fin. However, it does have two dorsal spines and small pectoral fins. This shark has big eyes to help it see in its dark environment, and it has five gill slits.
Range & Habitat: Lanternsharks live in either sandy or rocky areas. They live in dark waters above the seafloor. Juveniles often head to shallow waters where there is little to no sunlight because of runoff from the surface. The Lanternshark can be found in the Atlantic Ocean by northwest Europe, off the coast of Norway and Iceland, or down along the west coast of Africa.
IUCN Concern: On the IUCN redlist, the Velvet Belly Lanternshark is listed as least concern, despite overharvesting of individuals and aquatic resources, as well as the effects of climate change on the species' habitat.
Spiny Dogfish[edit | edit source]
Squalus acanthias[edit | edit source]
Defining Features: The Spiny Dogfish is recognizable for having two dorsal fins and no anal fin, similar to all Squaliformes. They also have spines protruding directly in front of each dorsal fin in order to inject venom into predators, thus giving them their name. Spiny Dogfish also have white spots on their flanks which help scientists distinguish them from other dogfish species.
Range & Habitat: Spiny Dogfish can be found in subarctic or temperate waters, in the North and South Atlantic as well as around Oceania. They can be found in depths between the surface and 3,000 feet.
IUCN Concern: The Spiny Dogfish is listed as vulnerable according to the IUCN. This is due to overfishing which causes strain on the population.
Example Species in the Gulf of Maine[edit | edit source]
Greenland Shark[edit | edit source]
Somniosus microcephalus[edit | edit source]
Defining Features: The Greenland Shark, like all Squaliformes, has two dorsal fins and an absent anal fin. Greenland Sharks also have a grey and brown exterior, and their skin almost looks scratched all over. Their eyes are a bleak blue and grey color which is unique to them due to them going blind. This happens because a type of copepod attaches itself to the cornea. This parasite is bio-luminescent which could help the Greenland Shark attract it's prey. One Greenland Shark has lived to be 272 years old, and some scientists believe some can live to be 400-500 years old.
Range & Habitat: The Greenland Shark lives in the extreme North Atlantic and the Arctic Ocean near Scandinavia, northern Canada and Greenland. They prefer cold, deep water and can reach depths of about 7,200 feet.
IUCN Concern: The Greenland Shark is considered near threatened. This is because fisheries in the Northern Atlantic and Arctic Oceans capture these sharks for their liver oil.
References[edit | edit source]
Aqua Maps: aquamaps.org
Chondrichthyan Tree of Life: sharksrays.org
Florida Museum of Natural History: floridamuseum.ufl.edu
National Geographic: nationalgeographic.com
NOAA Fisheries: fisheries.noaa.gov