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Photographer's Note

Here is a Risso Dolphin skimming below the surface of Monterey Bay. Water was so still, we were able to see them play under our boat. There were 500 of them all around us.

Risso's Dolphin was first described by Cuvier in 1812. The species' common name is for Mr. Risso who described a specimen to Cuvier on which Cuvier made his first description. Another common name for Risso's Dolphin is the Grampus (also the species genus) - although as a common name was historically used to describe the Orca. The etymology of the word grampus is unclear. It may be an aglomeration of the Latin grandis piscis or French grand poisson both meaning big fish. The specific name griseus refers to the mottled (almost scarred) grey colour of the dolphin's body.

Length is typically 10 feet (3 m), although animals have been recorded up to 12.5 feet (3.8 m). Like most dolphins, males are typically slightly larger than females. Weight averages about 650 pounds (300 kg), and large individuals may weigh up to 1100 pounds (500 kg).[1]

It is found worldwide in temperate and tropical waters, usually in deep waters rather than close to land. As well as the tropical parts of the Indian, Pacific and Atlantic Oceans, Rissos are also found in the Mediterranean and Red Seas, though are absent from the Black Sea. Their preferred environment is just off the continental shelf on steep banks (with water depths varying from 400-1000m) with water temperature at least 10 C and preferably in excess of 15 C.
The population around the continental shelf of the United States has been recorded to be in excess of 60,000. In the Pacific a census recorded 175,000 individuals in eastern tropical waters and 85,000 in the west. No global estimate of population exists.
Risso's Dolphins generally do not approach boats. A notable exception was an individual named Pelorus Jack who accompanied boats in Admiralty Bay in New Zealand's Marlborough Sound for more than 20 years. Whaling of this species has never been particularly widespread though operations off Sri Lanka may be significantly damaging the local population.[citation needed] Globally the species is recognised as abundant and safe.

Risso's have been taken into capitivity successfully in the United States and Japan, though with nowhere near the regularity of Bottlenose Dolphins or Orca. Hybrid Risso's-Bottlenose Dolphins have been bred in captivity.

Pelorus Jack was the name given to a dolphin that was famous for meeting and escorting ships over a certain stretch of water in Cook Strait, New Zealand, between 1888 and 1912. The dolphin's habits were so regular that on 26 September 1904, it was protected by Order in Council under the Sea Fisheries Act and remained so until its disappearance in 1912. It is thought to be the first individual sea creature protected in this way by any country.[1]

Pelorus Jack was 4 metres (1214 ft) long and was of a white colour with grey lines or shadings, and a round, white head.[2] Although its sex was never determined, it was identified from photographs as a Risso's Dolphin, Grampus griseus. This is an uncommon species in New Zealand waters, and only 12 Risso's Dolphins have been reported in that area.[3]

Pelorus Jack was usually spotted in Admiralty Bay between Cape Francis and Collinet Point, near French Pass, a treacherous channel used by ships travelling between Wellington and Nelson. In spite of his name, he did not frequent nearby Pelorus Sound, and local residents familiar with his habits assert that he never went through French Pass itself.[1]

The legend

Pelorus Jack was first seen around 1888 when it appeared in front of the schooner Brindle when the ship approached French Pass, a channel located between D'Urville Island and the New Zealand mainland. The area is dangerous to ships with rocks and strong currents but no shipwrecks occurred when Jack was present.
According to contemporary accounts, Pelorus Jack seemed to guide the ships, preferably steamers, through dangerous passages of the French Pass. It might swim alongside a watercraft for twenty minutes at a time. Sometimes if the crew could not see Jack at first, they waited for him to appear.
Thousands of sailors and travellers saw Pelorus Jack and he was mentioned in local newspapers and depicted in postcards. A law was passed in 1904, after someone tried to shoot him from a passing steamer.
Jack was last seen in April 1912. There were various rumours connected to his disappearance, including fears that foreign whalers might have harpooned him. However, research suggests that Pelorus Jack was an old animal; his head was white and his body pale, both indications of age, so it is likely that he died of natural causes.[3]

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Photo Information
  • Copyright: Bob DeMay (BOBDEMAY2) (83)
  • Genre: 地方
  • Medium: 彩色
  • Date Taken: 2007-09-14
  • Categories: 自然
  • Exposure:f/7.1, 1/125 seconds
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  • Photo Version:Original Version
  • Date Submitted: 2007-10-09 4:00
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