A number of sharks live hundreds or even thousands of metres deep, and never come near the surface. Among these bizarre species is the rare goblin shark (Mitsukurina owstoni), which has an outlandish overhanging snout, and jaws which protrude when feeding, then retract. Another odd creature is the frill shark (Chlamydoselachus anguineus), an eel-like animal living down to 1,300 metres. It has around 300 three-pronged teeth.
The cookie-cutter shark (Isistius brasiliensis) is a small, luminescent animal with a glowing belly that attracts fish from below. They usually inhabit depths to 3,500 metres, although they have been seen at the surface at night, and are believed to make daily vertical migrations of up to 3,000 metres. Their name comes from the cookie-shaped wounds they leave on whales, dolphins, tuna and other fish. Forming a suction cup with their mouths, cookie-cutter sharks latch onto their prey and rotate, carving out a chunk of flesh.
The world’s largest fish is the harmless whale shark (Rhincodon typus), reaching 12–15 metres in length. They can be recognised by their great size and distinctive blue-grey or red-brown colouring, with grid-like patterns of white spots and stripes.
They swim in tropical and subtropical coastal waters and the open ocean, and some venture into New Zealand waters on their annual migrations during summer. Between 1980 and 2001, 36 whale sharks were reported between the Three Kings Islands and south to the Bay of Plenty. Following the East Auckland Current, which flows past the east coast of Northland south to East Cape, whale sharks feed on anchovies and other small fish. They swim slowly near the surface, occasionally opening their cavernous mouths to consume the prey in their path.
The 10-metre-long basking shark (reremai, Cetorhinus maximus) is the second-largest fish in the world. Gentle giants, they can sometimes be seen from the coast swimming slowly near the surface of the ocean. Basking sharks open their mouths wide to catch plankton.
A craze for monsters
On 25 April 1977, Japanese fishermen 500 kilometres east of Christchurch hauled aboard a rotten and stinking carcass. After taking photos and keeping some of the decayed animal, they returned it to the depths. Speculation that it might have been a plesiosaur – a long-necked marine reptile known only from fossils – sparked monster fever in Japan. Stamps and toys were produced to commemorate the find. Finally, it was decided that the remains were those of a basking shark.
Between 1986 and 1999, 203 basking sharks were accidentally caught in trawl nets off New Zealand; 93 were caught off the east coast of the South Island in the spring–summer period.
Basking sharks are found around the world in temperate and sub-polar seas, excluding the Indian Ocean. Although considered a coastal species, they have been caught at depths of 900 metres during winter, where they could be feeding on the vast bonanza of hoki eggs available at that time.