Deep-Water Eels from Cook Strait, New Zealand
The recorded apodal fauna of New Zealand waters is not large. Griffin (1937, pp. 12–26) revised the eels of this region recognising 15 species. Whitley (1956, pp. 401–402) has listed 20 species from this area, including two fresh-water species, a bathypelagic species, Nemichthys scolopaceus Richardson, 1848, and a deep, benthic species Diastobranchus danae (Bruun, 1937) described originally from a pelagic larval specimen. The others were all shallow-water, coastal eels. One other deep-water eel has been recorded from New Zealand, Serrivomer bertini Bauchot, 1959, collected by the Dana 1928-30 Expeditions.
The extensive feeding grounds on the continental slope around New Zealand and the wide areas of temperate seas with their rich plankton would be expected to support an abundant and diverse benthic and bathypelagic deep-sea eel fauna. The known deep-water eel fauna as indicated above is yet small and is the result of the limited collections to date. This is demonstrated by the results reported here from sporadic collections made in the one area of Cook Strait over a short period of time.
During two of the years, 1956-1957, in which trawling and longlining were undertaken by the Department of Zoology, Victoria University of Wellington, in the Cook Strait area, six species new to the New Zealand region were collected in depths of more than 400 fathoms, thus increasing the known apodal fauna of this region by about 30 per cent. Only one of these species is as yet known from a restricted area, the remainder are in general known from widely spaced locations in the Indo-Pacific and Atlantic oceans. In the following account these six species are described and their systematic relationships discussed.
The Apodes represent perhaps one of the most specialised orders of teleost fishes, a specialisation of external morphology, osteology and life history. Other groups of teleosts have developed the eel-like form of the body, but few have the simplified page 2osteology and the unique larval development that are peculiar to the true eels. The specialisation and simplification of the external characters in the Apodes have produced many difficulties for the systematist. The families constituting the Order Apodes are well defined, but generic and specific characterisations are often less clear. Early, and even some recent workers in this group have relied to a large extent on differences in major body proportions in the separation of species, proportions which in many cases are of less positive value than originally supposed. While two of the most widely used characters in the classification of teleosts, scale and fin-ray counts, are generally regarded as of less systematic significance in eels, the value of fin-ray counts has been commonly underestimated in the past, but they should not be ignored in specific descriptions. The rather inaccessible osteology is also a valuable basis for classification, and wherever possible in the following account osteological characters are given.