Sharks of the Suborder Squaloidea in New Zealand Waters

Abstract

Echinorhinus cookei Pietschmann, 1928 is recorded from a 1980 mm male here designated as neotype. E. cookei is uniformly covered with numerous small, buckler-like dermal denticles, up to 4 mm diam., with strongly indented, angular bases and coarsely ridged spines; in contrast the denticles of E. brucus are sparse, irregularly distributed, up to 15 mm diam. if solitary but 35 mm if compound, and have entire-margined bases and finely ridged spines. Three New Zealand juveniles of E. cookei are markedly slender, with one-cusped teeth as in Squalus. The lateral line of E. cookei is an open furrow supported by incomplete, transverse skeletal rings with their free ends projecting as spines; the adult furrow is bridged at irregular intervals by skin. A Californian record of E. brucus is shown to be E. cookei. Previous New Zealand records of E. brucus cannot be confirmed, but E. brucus is known for New Zealand by a mounted skin of a Dunedin specimen in the Otago Museum. The genus Echinorhinus been known from New Zealand waters since 1884, with five specimens recorded in the literature as E. spinosus Blainville, 1825, E. mccoyi Whitley, 1931 or E. brucus (Bonnaterre, 1788). Of these E. spinosus and E. mccoyi are currently recognised as synonyms of E. brucus, the cosmopolitan Bramble Shark. Despite these records, only fragmentary Echinorhinus material was held in New Zealand museums, the most complete exhibit being a mounted skin of a specimen about 1420 mm long in the Otago Museum and labelled “Dunedin April 1887”. This specimen is not in the literature and there is no further information on it. In view of the above it was of considerable interest when two Cook Strait fishermen, Messrs. A. Dellabarca and W. Hickman of the line-boat “Calabria”, brought in a Bramble Shark taken in 40-50 fathoms in palliser Bay on 20th April, 1959. This shark, a male 1980 mm long, was obviously referable to Echinorhinus but lacked the larger, spine-bearing bucklers, up to 15 mm diameter or more on a specimen of equal size, which, irregularly and rather sparsely distributed over the body, are characteristic of E. brucus. Instead the Palliser Bay shark had a uniform covering of small bucklers, not larger than 4 mm diam. and mostly less, and much more numerous than those of E. brucus. Examination of the literature shows that this shark is identifiable as E. cookei Pietschmann, 1928, a species recorded only from the type taken off Hawaii. The status of E. cookei has not been clear-cut, apparently because Pietschmann (1928, 1930) did not give his reasons for separating it from E. brucus. Also, Fowler (1941, p.287) who examined the type of E. cookei reports that he "cannot find that Echinorhinus cookei is other than a variant of this species" (E. brucus). Bigelow and Schroeder (1948, p. 527) leave the question open, stating that "Final conclusions must await critical comparison of adequate series of specimens". The distinction of E. cookei from E. brucus is definite and striking, at least between sub-adult or adult specimens, but so far can be based only on the buckler-like dermal denticles (Plate 1, Figs. A-D). There appear to be no significant differences in proportional dimensions, in external morphology or in details of the teeth. However, the differences in the denticles lie not only in their relative size as mentioned above, though this alone is sufficient, but also in the shape and sculpture of the denticle bases (entire-margined or nearly so, and with rather fine radial ridging in E. brucus, but with strongly indented margins and coarse ridges (Text-fig.2, E-H) in E. cookei); the presence in E. brucus of compound denticles up to 35 mm long, as a result of fusion of adjacent denticle bases, while such fused denticles are not a feature of E. cookei; and there is the tendency in E. brucus