Diverging phenological responses of Arctic seabirds to an earlier spring

The timing of annual events such as reproduction is a critical component of how free‐living organisms respond to ongoing climate change. This may be especially true in the Arctic, which is disproportionally impacted by climate warming. Here, we show that Arctic seabirds responded to climate change by moving the start of their reproduction earlier, coincident with an advancing onset of spring and that their response is phylogenetically and spatially structured. The phylogenetic signal is likely driven by seabird foraging behavior. Surface‐feeding species advanced their reproduction in the last 35 years while diving species showed remarkably stable breeding timing. The earlier reproduction for Arctic surface‐feeding birds was significant in the Pacific only, where spring advancement was most pronounced. In both the Atlantic and Pacific, seabirds with a long breeding season showed a greater response to the advancement of spring than seabirds with a short breeding season. Our results emphasize that spatial variation, phylogeny, and life history are important considerations in seabird phenological response to climate change and highlight the key role played by the species' foraging behavior

Six pelagic seabird species of the North Atlantic engage in a fly-and-forage strategy during their migratory movements

Bird migration is commonly defined as a seasonal movement between breeding and non-breeding grounds. It generally involves relatively straight and directed large-scale movements, with a latitudinal change, and specific daily activity patterns comprising less or no foraging and more traveling time. Our main objective was to describe how this general definition applies to seabirds. We investigated migration characteristics of 6 pelagic seabird species (little auk Alle alle, Atlantic puffin Fratercula arctica, common guillemot Uria aalge, Brünnich’s guillemot U. lomvia, black-legged kittiwake Rissa tridactyla and northern fulmars Fulmarus glacialis). We analysed an extensive geolocator positional and saltwater immersion dataset from 29 colonies in the North-East Atlantic and across several years (2008-2019). We used a novel method to identify active migration periods based on segmentation of time series of track characteristics (latitude, longitude, net-squared displacement). Additionally, we used the saltwater immersion data of geolocators to infer bird activity. We found that the 6 species had, on average, 3 to 4 migration periods and 2 to 3 distinct stationary areas during the non-breeding season. On average, seabirds spent the winter at lower latitudes than their breeding colonies and followed specific migration routes rather than non-directionally dispersing from their colonies. Differences in daily activity patterns were small between migratory and stationary periods, suggesting that all species continued to forage and rest while migrating, engaging in a ‘fly-and-forage’ migratory strategy. We thereby demonstrate the importance of habitats visited during seabird migrations as those that are not just flown over, but which may be important for re-fuelling.publishedVersio

Identification of fish communities in the Barents Sea: Is there a faunal discontinuity across the Polar Front?

Fish species inhabiting the Barents Sea display great seasonal and between-year variation in abundance and distribution. This study describes the assemblages and distributions of fish species in the south-western part of the Barents Sea which includes the Polar front. The area has an unpredictable environment due to variable inflow of Atlantic water and assemblages and distributions of fish species differ between Arctic and Atlantic water masses. These assemblages can be identified as distinct groups corresponding to the different environments. In the period 1997 – 1999, 57 fish species and shrimp were identified and 32 species/species groups were used in the statistical analyses. Cluster and Correspondence analyses (CA) showed that the fish community consists of four different assemblages: A Northern, a Southern, a Deep and a Central group. In the Northern assemblage, species composition and spatial distribution varied least. The Central assemblage was the most variable. The Northern group included Polar cod, Atlantic poacher, spotted snake blenny and two species from the sculpin family. The Southern group included haddock and Norway pout. The Deep group included northern wolffish and long rough dab. Temperature explained 22% of the variation in the species data, and depth 12% of the variation. The assemblages are coherent with previous zoogeographic studies from the Barents Sea

Catch statistics and life history of shrimp, Pandalus borealis, in the Jan Mayen area

The Norwegian shrimp (Pandalus borealis) fisheries in the Jan Mayen area in the North East Atlantic started in 1974. The catches reached 2000 tons in 1985. Since 1986 the catches decreased, but lately they have increased again to 500 tons in 1994 and 1400 tons in 1995. Larger vessels ( > 2000 HP) were introduced in 1984. They caught more than 50% of the landings in the period from 1993 to 1995. The annual catch depends on stock biomass, availability according to ice coverage and circumstances in the shrimp fisheries off Greenland. The results of Norwegian shrimp surveys conducted in 1980, 1981, 1994 and 1995 are presented and discussed in relation to earlier studies, especially data from 1976 and 1979. The squared study area is defined by the coordinates 70°20' N, 7°30' W and 71 °15' N, 9°40' W. It covers the Jan Mayen Bank, south of the Jan Mayen island, and the Marøy Bank in the Northwest corner. Shrimp biomass is calculated for each 100 m depth interval for the six years, and show without exception the highest densities at the depth 200-299 m. The biomass index for the six years varies between 3000 and 6600 tons. The size of the shrimp increase with depth, thereby females dominate at depths greater than 300 m. The Jan Mayen shrimp is large compared to Barents Sea shrimp and can reach a carapace length of 38 mm. The large size at sex transformation (> 23 mm) and analysis of length frequency distributions indicate that the shrimp may be five to eight years when changing sex. The fish community composition is described and discussed for the years studied. Fish community composition is described for the years studied. Polar cod and capelin are the most abundant fish species in the study area. A high number of blue whiting was registered in 1979 but the number declined in 1980 and 1981. During the surveys in 1994 and 1995 no blue whiting was registered. The number of Greenland halibut has declined from the beginning of the 80-ties to the mid 90-ties

Ultrasonic tags reveal seasonal movements in red king crab (Paralithodescamtschaticus)

The red king crab was introduced to the Barents Sea in the 1960s and has spread widely both in Norwegian and in Russian waters, entailing a need to acquire knowledge of the biology and behaviour of the crab in these areas. Twenty crabs of both sexes were tagged with ultrasonic coded acoustic transmitters and released at three sites in Porsangerfjord, Finnmark, Norway. Ten acoustic receivers were placed in a non-uniform grid in the experimental area, allowing us to track individual crabs for ca. 12 months. Results on seasonal movements according to depth and sex throughout the year are presented as well as long‐term observations on individual crab behaviour. Daily movement speed of individual crabs is also calculated. Being a small introductory experiment, this study provides valuable information on the behaviour of a successful introduced species, essential knowledge for the understanding of the species and for pinpointing further investigations on the crab’s impact on the native ecosystem

Recent variations in recruitment of Northeast Atlantic greenland halibut (Reinhardtius hippoglossoides) in relation to physical factors

Based on annual bottom trawl surveys in the Barents Sea and Svalbard area in 1983-96, the paper describes variations in abundance and composition of 1-group Greenland halibut (Reinhardtius hippoglossoides). The main pattern of variation in abundance during the period was a change from high abundance in the first half of the period, to low abundance in the second half. The reduced abundance was associated with a northerly shift in distribution. In the last two years the recruits reappeared, first in northern parts of the study area and then also further south. These periodical changes in juvenile distribution, may be driven by physical oceanographical processes. Distribution changes probably extend beyond the area covered by the annual surveys. Thus, the results add uncertainty to the resent assessment of the state of the stock

Biometry, stable isotopes and stomach contents of A. glacialis and B. saida from Northeast Greenland

Two gadoid fishes, Arctogadus glacialis and Boreogadus saida, often coexist (i.e. sympatric) in the fjords and shelf areas of the Arctic seas, where they likely share the same food resources. Diet composition from stomach contents, i.e. frequency of occurrence (FO) and Schoener's index (SI), and stable isotope signatures (d13C and d15N) in muscle of these sympatric gadoids were examined from two fjords in NE Greenland-Tyrolerfjord (TF, ~74°N, sill present) and Dove Bugt (DB, ~76°N, open). Twenty-three prey taxa and categories were identified and both gadoids ate mostly crustaceans. The SI values of 0.64-0.70 indicated possible resource competition, whereas FO differed significantly. A. glacialis fed mainly on the mysid Mysis oculata and other benthic-associated prey, whereas B. saida ate the copepod Metridia longa and other pelagic prey. Both diet and stable isotopes strongly suggest a spatial segregation in feeding habitat, with A. glacialis being associated with the benthic food web (mean d13C = -20.81 per mil, d15N = 14.92 per mil) and B. saida with the pelagic food web (mean d13C = -21.25 per mil, d15N = 13.64 per mil). The dietary differences and isotopic signals were highly significant in the secluded TF and less clear in the open DB, where prey and predators may be readily advected from adjacent areas with other trophic conditions. This is the first study on the trophic position of A. glacialis inferred from analyses of stable isotopes. The subtle interaction between the Arctic gadoids should be carefully monitored in the light of ocean warming and ongoing invasions of boreal fishes into the Arctic seas