Prickly shark

The prickly shark (*Echinorhinus cookei*) is one of the two species in the genus Echinorhinus, the sole genus in the family Echinorhinidae. The prickly shark is mostly found in cooler waters of 5.5-11°C (41.9–51.8 °F). Because of this, the species is mostly found in deeper water over continental and insular shelves or slopes, or in trenches. It is generally a bottom-dweller, however it is known to frequent shallow waters in areas such as Monterey Bay.

## Description

The prickly shark's dermal denticles are non-overlapping and thorn-shaped, giving it its name. They are known to measure up to 0.4 cm (0.16 in).

The prickly shark has a flabby and stocky body which is especially bulky in adults. Its head is moderately flattened and relatively short and stout. The lateral line is forms a fairly conspicuous furrow. Like the bramble shark, the prickly shark lacks an anal fin.

The teeth of the prickly shark are very distinctive, with strongly angled main cusps flanked by two smaller cusps. This gives them a jagged, knife-like appearance. The two smaller cusps are absent in juveniles. The prickly shark has five gill slits, with the fifth pair being the longest.

Growing to 4 m (13.1 ft), the prickly shark is the largest member of the family Echinorhinus. The maximum recorded weight was 266 kg (586 lb) in a 3.1 m (10 ft) long female, however, specimens measuring 4 m (13.1 ft) would likely weigh considerably more.

## Distribution and habitat

The prickly shark is found in tropical and temperate waters across the Pacific Ocean, in Japan, Taiwan, Victoria and Queensland Australia, and New Zealand, as well as multiple regions of Oceania and Polynesia. They are also found in the Eastern Pacific as far north as Oregon, and have been recorded off the coast of Peru and the Galapagos Islands.

It is typically found in temperatures of 5.5–11 °C (41.9–51.8 °F) at depths below 100–200 m (330–660 ft). It has been recorded from at least 650 m (2,130 feet), however they may be found as deep as 1,500 m (4,900 feet). It occurs most frequently in the tropics, although sometimes in temperate water. In Monterey Bay, it has been known to frequent shallower waters of 15–35 m (49–115 ft), and off Moss Landing, one was even recorded at a depth of 4 m (13.1 feet).

## Ecology

The size and structure of the prickly shark's mouth and pharynx suggests that it would most likely capture prey primarily by 'suction', a technique used by some predators use where the predator opens its mouth creating a 'vacuum' which causes water to flow in 'sucking' in any nearby prey item that can fit through. The prickly shark is generally a slow swimmer, however, it is known to primarily prey on bony fishes including hake, flounders, rockfishes, lingcod, topsmelt, mackerel, and herring, as well as some other species of Chondrichthyes including young bluntnose sixgill sharks. They seem to feed largely on cephalopods such as octopuses and squid, including the Humboldt squid (*Dosidicus gigas*).

## Interaction with humans

The prickly shark appears to be harmless to humans, and it is of little to no economic value, however, the species is sometimes pulled up as bycatch of commercial deep-water fishermen. Because of the increase in global fishing, the prickly shark is listed as Near Threatened by the IUCN.