Notes: Abstract Little is known about the biology and feeding ecology of Arctogadus glacialis (Peters, 1874), an endemic gadid fish 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 Polynya off Greenland in August 1990. Size composition and sex ratios were assessed for 585 fish with standard lengths ranging from 7.8 to 34.5 cm. Median fish sizes at the stations ranged between 8.6 and 18.8 cm. Quantitative stomach content analyses of a subsample of 175 specimens 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 fish size groups. In terms of prey biomass, copepods dominated the diet of small fish (〈12 cm), primarily occurring at shallow stations (115–250 m), whereas amphipods and mysids were relatively more important for larger fish (〉16 cm), which dominated the catches at deep stations (360–480 m). The broad variety of diet composition indicated an opportunistic pelagic feeding pattern.

Notes: Abstract The trachymedusa Ptychogastria polaris Allman, 1878 has been identified in seabed photographs from high-Arctic shelves and upper continental slopes off Northeast Greenland and in the northern Barents Sea. It was found to be a common epifaunal element, being present at 34 of 57 stations in 40- to 495-m depth and at 7 of 11 stations in 70- to 330-m depth, respectively. All specimens recorded in the photographs either sat directly at, or hovered very closely (≤ about 1 cm) over, the sea bed, indicating a primarily epibenthic life style of this hydrozoan species. The small-scale (i.e. within-station) distribution of medusae was rather patchy, with frequencies along photographic transects – consisting of 35–73 pictures distributed over seabed strips of 150- to 300-m length – varying from 1 to 58% off Northeast Greenland and from 1 to 34% in the Barents Sea. Absolute maximum density was 6 ind m−2, and station mean abundances ranged from 0.01 to 0.91 ind m−2 and from 0.01 to 0.52 ind m−2, respectively. Values tended to decrease with water depth, albeit significantly only off Northeast Greenland. Otherwise, no clear relationships to environmental conditions, such as geomorphology or near-bottom water hydrography, were detected. Circumstantial evidence suggests that seabed granulometry and potential food supply are important distribution determinants. However, further investigations are required to identify more stringently the key factors controlling the distribution of P. polaris.

Notes: Abstract Composition and distribution of asteroid and ophiuroid assemblages were investigated by means of Agassiz trawl catches at 34 stations in 220- to 1,200-m depth in the Weddell Sea and at 17 stations in 90- and 830-m depth off Northeast Greenland. A total of 86 species (48 sea stars, 38 brittle stars) were identified in the Weddell Sea whereas off Northeast Greenland a total of 26 species (16 sea stars, 10 brittle stars) were recorded. In both study areas, brittle stars were numerically more important than sea stars, and abundances generally decreased with water depths. Multivariate analyses revealed a conspicuous depth zonation of sea and brittle stars off Greenland. Very high abundances of Ophiocten sericeum and Ophiura robusta characterized the assemblages on shallow shelf banks whereas in greater depths Ophiopleura borealis, Ophioscolex glacialis and Ophiacantha bidentata became dominant, albeit at significantly lower densities. Mass occurrences of brittle stars, such as those recorded on Greenlandic shelf banks, have not been discovered in the Weddell Sea, where distinct assemblages were discriminated in deep shelf trenches as well as on the eastern and southern shelf. Ophioplocus incipiens, Ophiurolepis martensi and Ophiurolepis brevirima were the most prominent species on the eastern shelf. Ophiacantha antarctica, Ophiurolepis gelida and Ophionotus victoriae on the southern shelf, and Ophiosparte gigas as well as the asteriod Hymenaster sp., in the shelf trenches. Overall, the Weddell Sea housed conspicuously more asterozoan species than the waters off Greenland. Higher species diversity was also evident at both a regional and local scale, especially for the eastern Weddell Sea shelf. However, because many species from the Weddell Sea are closely related, the Weddell Sea assemblages were not significantly different from the Greenland ones in terms of taxonomic diversity and distinctness.

Notes: Abstract The regular sea urchin, Strongylocentrotus pallidus (G.O. Sars, 1871), is a widespread epibenthic species in high-Arctic waters. However, little is known about its distribution, standing stock, population dynamics and production. In the northern Barents Sea, S. pallidus was recorded on seabed still photographs at 10 out of 11 stations in water depths of 80–360 m. Mean abundances along photographic transects of 150–300 m length ranged between 〈0.1 and 14.7 ind. m−2 yielding a grand average of 3.6 ind. m−2. The small-scale distribution along the transects was patchy, with densities varying from nil to an overall maximum of 25.5 ind. m−2, and exhibited a significant relation to the number of stones present. Sea urchin test diameters, measured on scaled photographs, extended from 7 to 90 mm. Median values at single stations varied from 14 to 46 mm, showing a significant inverse relationship to water depth. Biomass, estimated by combining photographic abundances, size frequencies and a size-mass function established with trawled specimens, ranged between 〈0.1 and 3.0 g ash-free dry mass m−2, averaging about 1.0 g ash free dry mass m−2. An analysis of skeletal growth bands in genital plates was carried out with 143 trawled individuals ranging in test diameter (D) from 4 to 48 mm. Assuming these bands to represent annual growth marks, the ages of the specimens analysed ranged between 3 and 42 years. A von Bertalanffy function was fitted to size-at-age data to model individual growth pattern (D∞ = 102.3 mm, k = 0.011 year−1, t0 = 0.633 year). The annual mortality rate Z of the population in the northern Barents Sea was estimated from a size-converted catch curve to be 0.08 year−1. Applying the weight-specific growth rate method, the average P/B ratio and the mean annual production of this population were estimated as 0.07 year−1 and 0.076 g AFDM m−2 year−1, respectively. In conclusion, S. pallidus is characterized by slow growth, low mortality, high longevity and low productivity. Because of its relatively high biomass, it is considered to contribute significantly to total benthic standing stock and carbon flux in the study area.

Notes: Abstract Species composition, abundance, biomass and spatial distribution pattern of brittle star assemblages of the Kolbeinsey Ridge, north of Iceland, were investigated by analysing seafloor photographs and epibenthic sled catches. Sampling was conducted in July 1992 along a 34 km long cross-ridge transect at 67°55′N in depths ranging from 830 to 1100 m. Five brittle star species were found. Only one species, Ophiocten gracilis, occurred with densities of more than 1 ind m−2. Both ridge slopes were characterized by soft bottom habitats, the ophiuroid distribution, however, revealed differences between slopes. Generally, brittle star densities were significantly higher on the eastern slope. There, the highest mean abundance per station of O. gracilis was 497 ind m−2. Except for one station, a distinct patchiness on the 100 m-scale was obvious in the spatial distribution of O. gracilis. Small settling stages with disc diameters 〈1 mm accounted for up to 98% of the population of O. gracilis near the ridge top, but their abundance share decreased with depth to only 6% on the eastern slope foot. Biomasses of O. gracilis were extrapolated by combining abundances estimated from photographic counts with a size-weight relationship and size frequencies established from sled catches. The highest value (120 mg AFDW m−2) was found on the deep eastern slope where large O. gracilis with disc diameters 〉4 mm were most abundant. Our findings reflect a cross-ridge gradient in terms of hydrographic regime and, hence, probably pattern of food supply for the benthos.