ORIGINAL PAPER Lis SuÈfke á Dieter Piepenburg á Christian F. von Dorrien Body size, sex ratio and diet composition of Arctogadus glacialis (Peters, 1874) (Pisces: Gadidae) in the Northeast Water Polynya (Greenland) Received: 6 November 1997 / Accepted: 11 May 1998 Abstract Little is known about the biology and feeding ecology of Arctogadus glacialis (Peters, 1874), an en- demic gadid ®sh species occurring circumpolarly in both ice-free and ice-covered Arctic seas. In this study we analysed specimens sampled from bottom trawl and Agassiz trawl catches conducted at eight stations in water depths from 115 to 490 m in the Northeast Water Poly- nya o Greenland in August 1990. Size composition and sex ratios were assessed for 585 ®sh with standard lengths ranging from 7.8 to 34.5 cm. Median ®sh sizes at the stations ranged between 8.6 and 18.8 cm. Quantitative stomach content analyses of a subsample of 175 speci- mens revealed that in the Northeast Water A. glacialis fed almost exclusively on pelagic prey. Truly benthic organisms were not found in the stomachs, and sympagic species were rarely recorded. Overall, calanoid copepods were the major prey in terms of numbers. However, stomach contents varied considerably between ®sh size groups. In terms of prey biomass, copepods dominated the diet of small ®sh (<12 cm), primarily occurring at shallow stations (115±250 m), whereas amphipods and mysids were relatively more important for larger ®sh (>16 cm), which dominated the catches at deep stations (360±480 m). The broad variety of diet composition in- dicated an opportunistic pelagic feeding pattern. Introduction Arctogadus glacialis (Peters, 1874) belongs to one of the few ®sh species that are endemic to the Arctic (Andriyashev 1964). It has been reported from both ice- free and ice-covered waters in the western Arctic (Sve- tovidov 1948; Nielsen and Jensen 1967; Frost 1981; Borkin and Mel'yantsev 1984; Dorrien et al. 1991). Like the other endemic-arctic gadid, the circumpolar Bore- ogadus saida (Lepechin, 1774), A. glacialis is assumed to be cryopelagic, i.e. to be basically a pelagic species that is associated with sea-ice biota for at least part of its life- cycle (Andriyashev 1970). In the literature, there is some confusion about the English trivial names of A. glacialis and B. saida. Both species were called either ``polar cod'' or ``Arctic cod''. Therefore, only the scienti®c names are used henceforth. While there is quite a wealth of information about the abundant B. saida (e.g. Rass 1968; Andriyashev 1970; Lowry and Frost 1981; Lùnne and Gulliksen 1989), far less is known about A. glacialis because only a few specimens had been caught for scienti®c analyses (Boulva 1972). During a ®eld study in the area of the Northeast Water (NEW) Polynya o Greenland, A. glacialis was found to be the most abundant ®sh species in trawl catches, and considerable numbers of them were collected (Dorrien et al. 1991). This rendered the opportunity to study in more detail the biology of this high-arctic species. The purpose of the present paper is to report our ®ndings about size and feeding of A. glacialis in the ice-free waters of the Northeast Water Polynya. Its diet composition was investigated to test whether this gadid species shows a preference for ben- thic, pelagic or sympagic food. Materials and methods A. glacialis was sampled from Agassiz trawl and bottom trawl catches carried out on the shelf o Northeast Greenland during the ``Polarstern'' cruise ARK VII/2 (Fig. 1). For a comprehensive cruise report see Krause (1991); for a description of catch methods and a detailed station list see Dorrien et al. (1991). The study area is characterized by a complex seabed morphology (Fig. 1). Very shallow banks with water depths of <40 m are separated by troughs with water depths of up to >500 m. The hydrography is Polar Biol (1998) 20: 357±363 Ó Springer-Verlag 1998 L. SuÈfke (&) á D. Piepenburg á C.F. von Dorrien 1 Institut fuÈr PolaroÈkologie der UniversitaÈt Kiel, Wischhofstr. 1-3, Geb. 12, 24148 Kiel, Germany e-mail: lsuefke@ipoe.uni-kiel.de, fax: (+49) (431) 600-1210 Present address: 1 World Wildlife Fund for Nature, WWF ± Marine & Coastal Division, Am GuÈthpol 11, 27757 Bremen, Germany