Prickly Shark

The prickly shark is a bottom-dwelling fish in the family Echinohinidae found in the Pacific Ocean. There is the presence of thorn-like dermal denticles, earning the shark its name.

Viktor Pietschmann-an Austrian ichthyologist was the first person to describe the species in separate publications in 1928 and 1930. A conchologist at the Bishop Museum, C. Montague Cooke Jr., is the person in whose honor, Pietschmann named the fish.

Some other alternative names by which they are known as Cook’s bramble shark and spinous shark.

Description

Mature male prickly sharks are about 5.9 – 7.5 feet long, whereas females measure around 8.3 feet on average. The largest shark of this species ever captured had a length of 13.1 feet.

They have a bulky body that is cylindrically shaped. Juveniles are not as bulkier as adults, although they appear flabby. A 10 ft long female at 586 lbs was the heaviest ever recorded specimen of the prickly shark..

Their body color is mainly plain brownish or gray, with a purple tint in specific individuals. The undersides appear of a paler coloration, especially on the snout and the region surrounding their mouth. There is the presence of a black trailing margin on the fins.

These sharks have a short, flattened head consisting of a pair of nostrils placed far apart and covered with small skin flaps. Their eyes do not contain nictitating membranes, but have tiny spiracles positioned behind.

They have wide mouths with short furrows at the corners. The upper and the lower jaws have 21-25 and 20-27 tooth rows, respectively, consisting of sharp teeth. Each tooth has three cusplets on either side, flanking a solid and angular central cusp.

Of the five gill slits present, the fifth one is the longest.

Their skin is uniformly covered with a dense layer of dermal denticles, which do not overlap each other. In adults, a layer of fine denticles is located just beneath their snout. These denticles are very sharp, with rugged ridges about the central spine and base.

Compared to the pectoral fins, the pelvic fins have a more extended base and are relatively larger. The first and the second dorsal fins are small and originate behind the point of origin of the pelvic fins. While the anal fin is absent in prickly sharks, a stout caudal peduncle is present near the source of the caudal fin. There is the presence of a long upper lobe and an unclear lower lobe in the caudal fin.

Where do they live

Map Of The Prickly Shark’s Habitat

Distributed across the Pacific Ocean, this species can be found in the nations of Western and Central Pacific, such as Japan; Taiwan; Victoria, and Queensland in Australia; New Zealand; and also in islands of Palau, New Caledonia, and Tonga. In the eastern Pacific, its numbers are spread across the island nation of Hawaii; the USA; Oregon; the Gulf of California, El Salvador; the Cocos and Galapagos islands, and from Costa Rica to Peru and Chile.

Although these sharks aren’t frequently spotted, both sexes of this species are found in the Monterey Canyon off California, where they can be seen throughout the year.

They are generally found in depths of 330–660 ft and favor cool tropical temperatures of 41.9–51.8 °F. Records show that this shark has been seen in depths of 2130 ft and can swim to depths of 4900ft. They inhabit continental and insular shelves, slopes, and submarine canyons, where they swim at the bottom, surrounded by muddy or sandy areas. These sharks have also been known to swim very close to the surface when they waddle into coastal waters of 49–115 ft in Monterey Canyon.

Behavior

Social and Migratory

Prickly sharks are active during the hours of dusk and dawn. Studies have shown that they follow diel vertical migration patterns. They mostly remain inactive throughout the day, resting in segregated locations near the sea floor. Their activity levels are primarily seen during dusk when they swim towards the coat and rise above the water column. Their upward motion is majorly associated with their feeding on the schooling fishes they spot in the water. Most sharks have a limited home range and live in seclusion within their domain. However, the prickly sharks dwelling along the Monterey Canyon region form aggregations of over thirty.

Dietary

The diet of prickly sharks consists of a variety of bottom and open-sea bony fishes such as hakes, rockfishes, herrings, mackerels, and flounders; cartilaginous fishes such as elephant fishes, spiny dogfishes, young bluntnose sixgill sharks and ghost catsharks. They also consume mollusks such as octopuses and squids.

Reproductory

They follow a viviparous mode of reproduction where young individuals hatch from eggs and are sustained by the yolk inside. Average litter size is unknown in these sharks, with the only record available of a gestating female who was pregnant with 114 embryos. During birth, young prickly sharks measure 16 inches. Research suggests that males attain sexual maturity when they are 6.6 ft, whereas females reach it at a length of 8.2-9.8 ft.

Adaptations

Due to their capability to breathe in depths where oxygen levels are low, these sharks can access ocean basins that are inaccessible to other sharks. The morphology of the prickly shark’s mouth and pharynx points towards its capability to use suction to capture prey.

Interactions with humans

The prickly shark is harmless to humans. They interact calmly with deep sea divers, either tolerating if mistakenly captured or attempting to flee upon sensing that they are being approached from close quarters. These sharks are never caught for commercial purposes since their soft meat isn’t of a high value. Yet, they may be susceptible to incidental capture by gillnets or bottom trawls, posing a threat to their population in the near future.

However, the IUCN has listed these sharks as a ‘Data Deficient’ species due to their unclear distribution. There are no conservation methods currently underway for the conservation of this species.