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Allometric relationships between body properties of animals are useful for a wide variety of purposes, such as estimation of biomass, growth, population structure, bioenergetic modelling and carbon flux studies. This study summarizes allometric relationships of zooplankton and nekton species that play major roles in polar marine food webs. Measurements were performed on 639 individuals of 15 species sampled during three expeditions in the Southern Ocean (winter and summer) and 2374 individuals of 14 species sampled during three expeditions in the Arctic Ocean (spring and summer). The information provided by this study fills current knowledge gaps on relationships between length and wet/dry mass of understudied animals, such as various gelatinous zooplankton, and of animals from understudied seasons and maturity stages, for example, for the krill Thysanoessa macrura and larval Euphausia superba caught in winter. Comparisons show that there is intra-specific variation in length–mass relationships of several species depending on season, e.g. for the amphipod Themisto libellula. To investigate the potential use of generalized regression models, comparisons between sexes, maturity stages or age classes were performed and are discussed, such as for the several krill species and T. libellula. Regression model comparisons on age classes of the fish E. antarctica were inconclusive about their general use. Other allometric measurements performed on carapaces, eyes, heads, telsons, tails and otoliths provided models that proved to be useful for estimating length or mass in, e.g. diet studies. In some cases, the suitability of these models may depend on species or developmental stages.

This dataset summarizes allometric measurements on zooplankton and nekton species performed in the framework of the Dutch and German ICEFLUX projects. Measurements were performed on 639 individuals of 15 species from the Southern Ocean and 2374 individuals of 14 species from the Arctic Ocean, including euphausiids, fish, pelagic and ice-associated amphipods, cnidarians, salps, siphonophores, chaetognaths and a copepod. Animals were collected during three expeditions in the Southern Ocean (winter and summer) and three expeditions in the Arctic Ocean (spring and summer). In addition to measurements on length and mass, the sizes of body parts were measured, such as carapaces, eyes, heads, telsons, tails and otoliths., This dataset summarizes allometric measurements on zooplankton and nekton species performed in the framework of the Dutch and German ICEFLUX projects. Measurements were performed on 639 individuals of 15 species from the Southern Ocean and 2374 individuals of 14 species from the Arctic Ocean, including euphausiids, fish, pelagic and ice-associated amphipods, cnidarians, salps, siphonophores, chaetognaths and a copepod. Animals were collected during three expeditions in the Southern Ocean (winter and summer) and three expeditions in the Arctic Ocean (spring and summer). In addition to measurements on length and mass, the sizes of body parts were measured, such as carapaces, eyes, heads, telsons, tails and otoliths.

Polar cod (Boreogadus saida), a key fish species in Arctic marine ecosystems, may be particularly susceptible to changing sea-ice habitats. It has been proposed that parts of the population get entrained with the growing sea ice in autumn, but how this happens and what proportion of the population becomes ice-associated is not known. The overall goal of the Go-West expedition was to test the hypothesis that entrainment of young Polar cod into the sea-ice habitat in the Chukchi and Beaufort seas during autumn is significant, and hence sea-ice association is an important survival strategy for Polar cod. During expedition SKQ201923S with RV Sikuliaq (06 November – 02 December 2019), we sampled Polar cod and its prey in the ice-water interface layer along with high resolution profiles of sea-ice and surface water properties with a Surface and Under-Ice Trawl (SUIT). We recorded backscatter of fish and zooplankton in the water column with the Sikuliaq’s EK80 echosounder, and sampled pelagic communities with two midwater trawls (Methot trawl and IKMT) and vertical zooplankton nets (CalVET and ring net). A conductivity-temperature—depth probe equipped with a rosette water sampler (CTD) sampled vertical profiles of temperature, salinity and fluorescence and was used to collect water samples for the analysis for chlorophyll a concentration, nutrient concentrations, trophic biomarkers and harmful algae (HAB). During four ice stations, we sampled the sea ice for the same parameters (except nutrients), and performed hyperspectral light measurements needed to derive ice algae biomass from hyperspectral profiles obtained from a sensor mounted on the SUIT. In addition, we performed respiration measurements on abundant zooplankton prey species of Polar cod. Altogether, we completed 11 SUIT stations (1 in open water, 10 under ice), 4 ice stations and 3 midwater trawls. All SUIT deployments were succesful, expanding Sikuliaq’s capability of advanced scientific operations in ice-cover