Spatial occurrence and abundance of marine zooplankton in Northeast Greenland

We present a large-scale survey of mesozooplankton (size range 0.2–20 mm) across coastal, shelf, and slope locations in Northeast Greenland (latitudes 74–79° N, August 2015 and September 2017). Our study is centred on the Video Plankton Recorder (VPR) for non-invasive in situ observations of taxa distribution and abundance while simultaneously recording oceanographic profiles. A modified WP-2 plankton net (85-μm mesh size) was used primarily not only to verify taxa detected by the VPR but also to make a preliminary comparison of abundance estimates by the two gears. A total of 35 zooplankton taxa were identified with 10 genera alone among copepods (Hexanauplia). Selected taxa from the VPR (N=16) were associated with the temperature-salinity spaces and the chlorophyll a-depth profiles in the study area. From surface to > 900 m depth, the overall temperature and salinity ranged between −1.9 and 6.8 °C and 26.6 and 35.3, respectively. Two copepod genera dominated, i.e. Pseudocalanus prevailed in the upper sub-zero layers in coastal waters whereas Calanus was omnipresent, but mainly abundant in the warmer Atlantic waters at the shelf break. Chlorophyll a levels were in general very low (< 2 mg m-3) and peaked at 30–50 m depth, suggesting post-bloom conditions. Overall, zooplankton abundances tended to increase from the coast towards the slope (9–344×103 individuals m-2). Biodiversity in terms of taxon richness, on the other hand, showed the opposite trend and decreased from 16 taxa at the coast to 5 taxa further offshore

Ice Cod Arctogadus glacialis (Peters, 1874) in Northeast Greenland—A First Sketch of Spatial Occurrence and Abundance

Based on bottom trawl catches during the years 2002–2017, we present the first large-scale baseline on the spatial distribution and abundance of ice cod Arctogadus glacialis (Peters, 1874) in the fjords and on the shelf in Northeast Greenland (latitudes 70 °N–78 °N). Ice cod abundance peaked in the secluded sill fjords such as Bessel Fjord, Brede Fjord, Clavering Ø fjord system and Kong Oscar Fjord as compared to the offshore shelf. The mean biomass was estimated as 3.9 kg/km2 on the shelf and 49.3 kg/km2 in the fjords. Nearly 45% of the biomass was restricted to temperatures < −1.0 °C and almost 90 % of the biomass occurred within 200–600 m depth. This corresponds well with the deep, subzero fjords along the Northeast Greenland coast which, thus, appear the most suitable habitat for ice cod. Moreover, there was a gradual decrease in ice cod biomass on the shelf over the years 2002–2017. This apparent relocation of ice cod matches the ongoing warming of the Northeast Greenland shelf waters. Given that the overall temperature space of ice cod spans less than 4 ºC in Northeast Greenland, it is likely that the species is particularly vulnerable to climate change as warmer waters before long enter the fjords, i.e., the main habitat for ice cod

Farming of Atlantic cod Gadus morhua in the vicinity of major spawning sites for Norwegian coastal cod populations - is it hazardous?

Waters along and adjacent to the coast of northern Norway are unique in housing two major populations of Atlantic cod with very di erent life histories. The Northeast Arctic cod (NEAC) has its nursery and feeding grounds in the Barents Sea but migrates to the coast of northern Norway to spawn. Norwegian coastal cod (NCC) is more stationary, spawns mainly at local sites in individual ords but to some degree also overlap with the spawning sites of NEAC (Fig.1). These distinctive patterns in life history are re ected in a clear-cut genetic divergence between the two populations. Various molecular genetic markers (scnDNA, microsatellites and SNPs) have displayed genetic di erences between NEAC and NCC which are remarkable for marine sh with a comparable gene ow potential (cf. Sarvas and Fevolden 2005, Wennevik et al. 2008, and Westgaard and Fevolden 2008 for recent updates)

A mitogenomic approach to the taxonomy of pollocks: Theragra chalcogramma and T. finnmarchica represent one single species

<p>Abstract</p> <p>Background</p> <p>The walleye pollock (<it>Theragra chalcogramma</it>) and Norwegian pollock (<it>T. finnmarchica</it>) are confined to the North Pacific and North Atlantic Oceans, respectively, and considered as distinct species within the family Gadidae. We have determined the complete mtDNA nucleotide sequence of two specimens of Norwegian pollock and compared the sequences to that of 10 specimens of walleye pollock representing stocks from the Sea of Japan and the Bering Sea, 2 specimens of Atlantic cod (<it>Gadus morhua</it>), and 2 specimens of haddock (<it>Melanogrammus aeglefinus</it>).</p> <p>Results</p> <p>A total number of 204 variable positions were identified among the 12 pollock specimens, but no specific substitution pattern could be identified between the walleye and Norwegian pollocks. Phylogenetic analysis using 16.500 homologous mtDNA nucleotide positions clearly identify the Norwegian pollock within the walleye pollock species cluster. Furthermore, the Norwegian pollock sequences were most similar to mitochondrial genotypes present in walleye pollock specimens from the Sea of Japan, an observation supported both by neighbor-joining, maximum parsimony, and maximum likelihood analyses.</p> <p>Conclusion</p> <p>We infer that walleye pollock and Norwegian pollock represent one single species and that Norwegian pollock has been recently introduced from the Pacific to the Atlantic Oceans.</p

Greenland Shark (Somniosus microcephalus) Stomach Contents and Stable Isotope Values Reveal an Ontogenetic Dietary Shift

Current knowledge on the feeding ecology of the Greenland shark (Somniosus microcephalus), a potential top predator in arctic marine ecosystems, is based on small sample sizes as well as narrow size ranges of sharks. Therefore, potential size-related feeding patterns remain poorly documented. Using stomach content data (N = 88) and stable isotope values of white muscle tissue (N = 40), this study evaluates the diet of sharks ranging in size from 81 to 474 cm (total length). The importance of prey categories (“Fish,” “Mammal,” “Squid,” “Crustacean,” and “Other”) was evaluated based on the reconstructed prey biomass of the stomach contents. Stable isotope values of δ13C and δ15N ranged between -14.4 to -19.9‰ and 11.8 to 17.2‰, respectively. The importance of each prey category was estimated by the Index of Relative Importance (IRI). Our findings suggest that the smallest Greenland sharks (&lt;200 cm) feed on lower trophic level prey, predominantly squids. Larger sharks (&gt;200 cm) mainly feed on higher trophic level prey such as seals, epibenthic and benthic fishes including gadoids (Gadidae), skates (Rajidae), righteye flounders (Pleuronectidae), lumpfish (Cyclopteridae), wolffish (Anarhichadidae), and redfish (Sebastidae). Redfish were, however, only found to be important in the largest sharks sampled (&gt;400 cm). In addition to demonstrating ontogenetic shifts in their feeding preferences, this study supports that Greenland sharks are capable of active predation on fast swimming seals and large fishes

Assessing the reproductive biology of the Greenland shark (Somniosus microcephalus)

The Greenland shark (Somniosus microcephalus, Squaliformes: Somniosidae) is a long-lived Arctic top predator, which in combination with the high historical and modern fishing pressures, has made it subject to increased scientific focus in recent years. Key aspects of reproduction are not well known as exemplified by sparse and contradictory information e.g. on birth size and number of pups per pregnancy. This study represents the first comprehensive work on Greenland shark reproductive biology based on data from 312 specimens collected over the past 60 years. We provide guidelines quantifying reproductive parameters to assess specific maturation stages, as well as calculate body length-at-maturity (TL50) which was 2.84±0.06 m for males and 4.19±0.04 m for females. From the available information on the ovarian fecundity of Greenland sharks as well as a meta-analysis of Squaliform reproductive parameters, we estimate up to 200–324 pups per pregnancy (depending on maternal size) with a body length-at-birth of 35–45 cm. These estimates remain to be verified by future observations from gravid Greenland sharks

Greenland Shark (<i>Somniosus microcephalus</i>) Stomach Contents and Stable Isotope Values Reveal an Ontogenetic Dietary Shift

Current knowledge on the feeding ecology of the Greenland shark (Somniosus microcephalus), a potential top predator in arctic marine ecosystems, is based on small sample sizes as well as narrow size ranges of sharks. Therefore, potential size-related feeding patterns remain poorly documented. Using stomach content data (N = 88) and stable isotope values of white muscle tissue (N = 40), this study evaluates the diet of sharks ranging in size from 81 to 474 cm (total length). The importance of prey categories (“Fish,” “Mammal,” “Squid,” “Crustacean,” and “Other”) was evaluated based on the reconstructed prey biomass of the stomach contents. Stable isotope values of δ13C and δ15N ranged between -14.4 to -19.9‰ and 11.8 to 17.2‰, respectively. The importance of each prey category was estimated by the Index of Relative Importance (IRI). Our findings suggest that the smallest Greenland sharks (200 cm) mainly feed on higher trophic level prey such as seals, epibenthic and benthic fishes including gadoids (Gadidae), skates (Rajidae), righteye flounders (Pleuronectidae), lumpfish (Cyclopteridae), wolffish (Anarhichadidae), and redfish (Sebastidae). Redfish were, however, only found to be important in the largest sharks sampled (>400 cm). In addition to demonstrating ontogenetic shifts in their feeding preferences, this study supports that Greenland sharks are capable of active predation on fast swimming seals and large fishes

Pan-Arctic suitable habitat model for Greenland halibut

Deep-sea marine fishes support important fisheries but estimates of their distributions are often incomplete as the data behind them may reflect fishing practices, access rights, or political boundaries, rather than actual geographic distributions. We use a simple suitable habitat model based on bottom depth, temperature, and salinity to estimate the potential distribution of Greenland halibut (Reinhardtius hippoglossoides). A large presence-only dataset is examined using multivariate kernel densities to define environmental envelopes, which we link to spatial distribution using a pan-Arctic oceanographic model. Occurrences generally fit the model well, although there were gaps in the predicted circum-Arctic distribution likely due to limited survey activity in many of the ice-covered seas around the Arctic Ocean. Bottom temperature and depth were major factors defining model fit to observations, but other factors, such as ecosystem interactions and larval drift could also influence distribution. Model predictions can be tested by increasing sampling effort in poorly explored regions and by studying the connectivity of putative populations. While abundances of Greenland halibut in the High Arctic are currently low, some areas are predicted to be suitable habitat for this species, suggesting that on-going sea-ice melt may lead to fisheries expansion into new areas

Vertical redistribution of principle water masses on the Northeast Greenland Shelf

The Northeast Greenland shelf (NEGS) is a recipient of Polar Water (PW) from the Arctic Ocean, Greenland Ice Sheet melt, and Atlantic Water (AW). Here, we compile hydrographical measurements to quantify long-term changes in fjords and coastal waters. We find a profound change in the vertical distribution of water masses, with AW shoaling >60 m and PW thinning >50 m since early 2000’s. The properties of these waters have also changed. AW is now 1 °C warmer and the salinity of surface waters and PW are 1.8 and 0.68 lower, respectively. The AW changes have substantially weakened stratification south of ~74°N, indicating increased accessibility of heat and potentially nutrients associated with AW. The Atlantification earlier reported for the eastern Fram Strait and Barents Sea region has also propagated to the NEGS. The increased presence of AW, is an important driver for regional change leading to a likely shift in ecosystem structure and function

Detecting changes in the Arctic Ecosystem – Long-Term Benthos Monitoring network for detecting changes in the Arctic benthic ecosystem (LTM-Benthos) 2017-2020

publishedVersio