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Zoology Publications from Victoria University of Wellington—Nos. 54 to 57

Distribution and Habitat

Distribution and Habitat

Bigelow and Schroeder (1948) record H. perlo from the eastern and western North Atlantic, the Mediterranean, the Cape of Good Hope and Japan. The present paper extends its known range to Australia and New Zealand. It is undoubtedly more widely distributed than has been recorded.

Little is known of its mode of life. Bigelow and Schroeder (1948) note that "It seems to be a bottom dweller chiefly, of coastal waters", and give it an extended depth range from about 400 m off Portugal and deep water off Cuba, to very shallow water and lagoons on the coast of Africa. The latter record is based on Rochebrune's (1882) account of Notidanus cinereus, but this possibly is referable to the Broadsnouted Sevengill Notorynchus, which is regularly taken in very shallow water in several parts of the world. There is considerable confusion between Heptranchias and Notorynchus in early accounts.

Australian accounts (of dakini) indicate a range of 100 to 400 m, with some captures in more shallow water. Most recorded New Zealand captures have been in moderately deep water, with some shallow-water captures (50 m) in areas where other deep-water fish are also sometimes taken.

We believe that H. perlo is a shelf-edge species, and that it may be rather more common than its reported captures indicate, its slenderness and agility allowing it to escape from trawl nets. When caught it is very active and aggressive, its flexible vertebral column allowing almost snake-like movements. Scott (1962) reports it as being frequently taken on long-lines in South Australia, and one of us (J.A.F.G.) took four fish on one long-line set in 330 m in Hawke Bay, New Zealand, in 1955. The lightly calcified skeleton of H. perlo, mentioned in passing by Springer and Garrick (1964), and shown here in Plate 2, may be an adaptation to a bathypelagic, or at least "above-bottom" mode of life, similar to that of the lightly-calcified "pelagic" shark Euprotomicrus bispinatus (see Hubbs et al., 1967). Bone and Roberts (1969) have tentatively classified H. perlo as pelagic, apparently on the basis of an earlier liver-oil density determination (Tsujimoto, 1932). Further work on fish density, liver-oil analysis (such as that of Shimma and Shimma, 1969) and studies on eye structure (Denton and Nicol, 1964) may provide some answers on the mode of life of this species.