Distribution and Biology of the New Zealand Endemic Catshark, Halaelurus dawsoni

Abstract

Halaelurus dawsoni has a restricted geographic range, occurring only in south-eastern New Zealand. It is primarily a demersal inhabitant of the upper continental slope, plateaus, and ridges at 250–800 m depth. Halaelurus dawsoni is a voracious carnivore that feeds on a wide variety of crustaceans and fishes. Maximum recorded length is 418 mm total length, and males and females grow to similar maximum lengths. Length at 50% maturity is about 340–350 mm for males and 330–360 mm for females. The reproductive mode of H. dawsoni is single oviparity, with one leathery egg case being carried per uterus. It appears that most embryonic development occurs after egg cases are deposited on the seabed. The reproductive mode of species of Halaelurus in the subgenus Halaelurus is multiple oviparity, whereas for those in the subgenus Bythaelurus it is single oviparity or aplacental viviparity. It has been suggested that single oviparity is a primitive reproductive mode, and that aplacental viviparity evolved from it via the intermediate stage of multiple oviparity. However, the relationship between reproductive mode and Halaelurus subgenus suggests that aplacental viviparity may have evolved directly from single oviparity in the subgenus Bythaelurus without passing through a multiple oviparous stage.