Chionodraco hamatus shows a circumantarctic distribution, although it is mainly recorded on the continental shelf of East Antarctica down to 600 m depth (Iwami & Kock 1990). The lack of haemoglobin in the blood, which characterises these fishes, has probably played a key role in determining their distribution within the cold and highly oxygenated waters of the Antarctic, where metabolic requirements dependent on temperature are low (Eastman 1993). Consequently, several studies on these species have focussed on their blood physiology, as well as on the structure and function of antifreeze components (Kunzmann 1989, 1991; Wells et al. 1990; Egginton 1996; Wöhrmann 1996, 1997).
The channichthyid Chionodraco hamatus is a common icefish within the cold waters of the high-Antarctic zone. It is an endemic species to the Antarctic region. Off Terra Nova Bay, as well as in the Ross Sea, Chionodraco hamatus is by far the most abundant and eurybathic icefish, both in terms of biomass and frequency of occurrence (Eastman & Hubold 1999; Vacchi et al., 1999).
Chionodraco hamatus spawns in spring (September-October) in the Mawson Sea and throughout summer (December-March) in the Ross Sea, Davis Sea and Weddell Sea (Shandikov & Faleeva 1992; Duhamel et al., 1993; Vacchi et al., 1996). As in other high-Antarctic channichthyids, C. hamatus females are characterised by having low fecundity and they produce only a few thousand but large (3.5-5 mm) eggs (Vacchi et al. 1996). C. hamatus probably spawns a single batch of oocytes once a year (La Mesa et al., 2003).
