Search

There is an urgent need to find alternative feed resources that can further substitute fishmeal in Atlantic salmon diets without compromising health and food quality, in particular during the finishing feeding period when the feed demand is highest and flesh quality effects are most significant. This study investigates efficacy of substituting a isoprotein (35 %) and isolipid (35 %) low fishmeal diet (FM, 15 %) with Antarctic krill meal (KM, 12 %) during 3 months with growing finishing 2·3 kg salmon (quadruplicate sea cages/diet). Final body weight (3·9 (se 0·04) kg) was similar in the dietary groups, but the KM group had more voluminous body shape, leaner hearts and improved fillet integrity, firmness and colour. Ectopic epithelial cells and focal Ca deposits in intestine were only detected in the FM group. Transcriptome profiling by microarray of livers showed dietary effects on several immune genes, and a panel of structural genes were up-regulated in the KM group, including cadherin and connexin. Up-regulation of genes encoding myosin heavy chain proteins was the main finding in skeletal muscle. Morphology examination by scanning electron microscopy and secondary structure by Fourier transform IR spectroscopy revealed more ordered and stable collagen architecture of the KM group. NEFA composition of skeletal muscle indicated altered metabolism of n-3, n-6 and SFA of the KM group. The results demonstrated that improved health and meat quality in Atlantic salmon fed krill meal were associated with up-regulation of immune genes, proteins defining muscle properties and genes involved in cell contacts and adhesion, altered fatty acid metabolism and fat deposition, and improved gut health and collagen structure., This work was funded by Aker Biomarine Antarctic AS, Oslo, Norway

Donnan Dialysis (DD) is developed in this study for continuous removal of fluoride from Antarctic krill by using seawater or concentrated seawater as the receiving solution. Results show that RO concentrate (1.0 mol L−1 NaCl) got the highest fluoride removal efficiency (93.66% ± 0.81%) with three stages at 0.01 cm s−1 flow velocity. Afterwards, fluoride removal experiment with a real krill solution showed 89.34% ± 0.55% under the optimized conditions. The product has fulfilled the fluoride content of US FDA standard and Canadian Food Inspection Agency in fish and fish products. Results also showed a lower loss of amino acids and proteins in comparison of conventional methods. Finally, a techno-economic evaluation showed that 4.0 USD per ton of Krill solution can be expected by this DD process. This study proves that Donnan Dialysis may be a sustainable defluorination process in removing high fluoride content of seafood by seawater or concentrated seawater.

International audience; The Antarctic krill, Euphausia superba, is a Southern Ocean endemic species of proven ecological importance to the region. In the context of predicted global warming, it is particularly important to understand how classic biomarkers of heat stress function in this species. In this respect, Hsp70s are acknowledged as good candidates. However, previous studies of expression kinetics have not been able to demonstrate significant upregulation of these genes in response to heat shocks at 3 °C and 6 °C for 3 and 6 h. The current work complements these previous results and broadens the prospects for the use of Hsp70s as a relevant marker of thermal shock in this krill species. New experiments demonstrate that induction of Hsp70 isoforms was not detected during exposure to heat shock, but increased expression was observed after several hours of recovery. To complete the analysis of the expression kinetics of the different isoforms, experiments were carried out over short time scales (1 and 2 h at 3 °C and 6 °C) as well as at higher temperatures (9 °C, 12 °C, and 15 °C for 3 h), without any significant response. A 6-week monitoring of animals at 3 °C showed that the time factor is decisive in the establishment of the response. CTmax experiments with incremental times of 1 °C per day or 1 °C every 3 days have shown a particularly high resilience of the animals. The demonstration of the abundance of Hsp70s present before thermal stress in various species of krill, as well as in specimens of E. superba of various origins, showed that the delay in the response in expression could be related to the high constitutive levels of Hsp70 available before the stress experiments. The alternative labelling of the two main isoforms of Hsp70 according to the origin of the animals allowed hypotheses to be put forward on the functioning of thermoregulation in Antarctic krill as well as ice krill.

Cleaner production in the textile industry may be realized by replacing certain synthetic substances with natural materials, especially those that are industrial by-products, which offer the added benefit of increasing the value of the textiles. Since natural materials generally pose a low risk to both the human health and the environment owing to their biodegradability, the wastewater released from their manufacturing processes is less polluting, and therefore, it requires less resources and energy for treatment compared to wastewater loaded with synthetic substances. Herein, we report the use of a protein by-product recovered from the oil extraction process of Antarctic krill (Euphausia superba) to replace traditional mordanting agents in the dyeing of cotton with tannin-rich natural dye extracted from the bark of Xylocarpus granatum. Antarctic krill protein pretreatment successfully improved the dyeability of the fabrics through the formation of insoluble complexes between the protein and tannin. The color parameters of the dyed samples were measured based on the CIE L*a*b* system. The obtained reddish-brown fabrics exhibited mostly good to excellent color fastness ratings in response to washing and other wet treatments. They also displayed durable UV protection properties, with the UPF rating reaching the maximum (50+) level, despite being washed for 50 cycles. Both the Antarctic krill protein and tannin contributed to improved UV protection efficiency due to the presence of UV-absorbing moieties and slight changes in the resulting fabric thickness and cover factor.

Summary 1.Understanding interspecific interactions, and the influences of anthropogenic disturbance and environmental change on communities, are key challenges in ecology. Despite the pressing need to understand these fundamental drivers of community structure and dynamics, only 17% of ecological studies conducted over the past three decades have been at the community level. 2.Here, we assess the trophic structure of the procellariiform community breeding at South Georgia, to identify the factors that determine foraging niches and possible temporal changes. We collected conventional diet data from 13 sympatric species between 1974 and 2002, and quantified intra- and inter-guild, and annual variation in diet between and within foraging habits. In addition, we tested the reliability of stable isotope analysis (SIA) of seabird feathers collected over a 13-year period, in relation to those of their potential prey, as a tool to assess community structure when diets are diverse and there is high spatial heterogeneity in environmental baselines. 3.Our results using conventional diet data identified a four-guild community structure, distinguishing species that mainly feed on crustaceans; large fish and squid; a mixture of crustaceans, small fish and squid; or carrion. In total, Antarctic krill Euphausia superba represented 32%, and 14 other species a further 46% of the combined diet of all 13 predators, underlining the reliance of this community on relatively few types of prey. Annual variation in trophic segregation depended on relative prey availability; however, our data did not provide evidence of changes in guild structure associated with a suggested decline in Antarctic krill abundance over the past 40 years. 4.Reflecting the differences in δ15N of potential prey (crustaceans vs. squid vs. fish and carrion), analysis of δ15N in chick feathers identified a three-guild community structure that was constant over a 13-year period, but lacked the trophic cluster representing giant petrels which was identified using conventional diet data. 5.Our study is the first in recent decades to examine dietary changes in seabird communities over time. Conventional dietary analysis provided better resolution of community structure than SIA. However, δ15N in chick feathers, which reflected trophic (level) specialization, was nevertheless an effective and less time-consuming means of monitoring temporal changes.

The extent to which marine species avoid survey vessels is the subject of considerable debate, with stimuli such as noise and pressure waves receiving particular attention. By some estimates, avoidance behaviour is a major bias in the assessment of pelagic species distribution and density. Surveyors of the marine environment are increasingly using autonomous platforms; thus the question of avoidance of these novel platforms must be considered. A long-duration, underwater glider with an integrated echo-sounder was deployed to measure the density and distribution of Antarctic krill. We show that krill reacted to the glider, despite the low-noise profile of the platform. The weighted-mean depth of krill swarms was observed to deepen when a glider came within 30 m. In addition, we observed a near-range decrease in depth-integrated acoustic backscatter and we demonstrate that this effect is not explained by the instrument's acoustic footprint. The potential triggers for these behaviours are discussed. The list of sensors available for use on a glider is increasing, with some producing sound, light or other potential stimuli for behavioural response. Our paper demonstrates that caution should be used when designing mission payloads and in the interpretation of acoustic data for animal density from gliders. A key consideration for surveyors may be the factoring in of an exclusion zone from their analyses.

The net position and the spreading performance are crucial for hydrodynamic performances of Antarctic krill trawl, which determine its fishing efficiency. In this paper, the hydrodynamic performance of an Antarctic krill trawl system (including trawler, cable, otter board and trawl) was studied by means of numerical simulation combined with full-scale measurement at sea. The numerical model was established based on finite element method and the principle of minimum potential energy was employed to determine the equilibrium configuration of the trawl system in uniform current. The Newton–Raphson method was applied to solve the equilibrium equation. A multi-wing vertical cambered otter board was designed and a series of wind tunnel model tests were carried on in order to explore the hydrodynamic performance (drag coefficient, lift coefficient and lift-drag ratio) of the otter board. By comparing the simulated results and the simulated results after correction with the experimental results at sea, the modified Tauti's law and the accuracy of the numerical method were verified. The results showed that the fishing vessel, the trawl and the otter board matched well on hydrodynamics. The effects of the warp length, the leg length, the towing speed and the angle of attack of the otter board on the net position, the spread of otter board and the spreading performance of net opening were analyzed. Scientific suggestions on the setting of each component of the trawl system were given based on the numerical simulation study. This paper could be regarded as a scientific reference for Antarctic krill trawl fishing operation.

The beauty and vital nature of krill obviously captured the imagination of the early krill scientists working in the 1920s and ’30s. Despite the vibrant descriptions of schooling krill that bring their writings to life, their science was almost entirely focused on routine measurements of preserved animals. There was one exception. A paper published in 1967 described an experiment on live krill carried out in the 1920s. The author seemed almost apologetic for wasting the reader’s time: “The observations described in this paper were made only as a casual experiment to occupy a little spare time.” Obviously, understanding the biology of living krill was not deemed that important back then. It wasn’t until the 1960s, when that paper finally saw the light of day, that scientists felt the need to devote a little more time to the study of living krill. In the 1970s and ’80s the spotlight slowly turned to Antarctic krill, largely because of the growing fishery (see chapters six and seven). The largest ever international marine biological research program, Biological Investigations of Marine Antarctic Systems and Stocks (BIOMASS) commenced. This program focused on the role of krill in the Southern Ocean ecosystem. BIOMASS invigorated studies on living krill, and the modern era of krill biology began.

Cellulose (C) and Antarctic krill protein (AKP) were dissolved at low temperature, and then C/AKP composite fibers were prepared by wet spinning. In this paper, the effect of coagulation bath temperature on the properties of C/AKP composite fibers were studied by FT-IR, XRD, DSC, and other tests. The results showed that, when the temperature of the coagulation bath increased from 5 to 25 °C, the intermolecular hydrogen bond content of the C/AKP composite fibers increased from 28.20% to 31.33%. When the coagulation bath temperature is 15 °C, the breaking strength of the composite fibers is 1.64cN/dtex, which is 12% higher than that of the composite fibers at room temperature. At this temperature, the crystallinity of the composite fibers is improved, the thermal stability is slightly improved, and the surface morphology is smoother. Inspiringly, when zinc sulfate is added to the coagulation bath, the formation process of the fibers is milder. Moreover, the C/AKP composite fibers have excellent antibacterial activity against

This paper presents the data on distribution and size composition of the Antarctic krill (Euphausia superba) population in the northwestern Weddell Sea (Powell Basin) and adjacent areas in summer 2020. Juvenile krill dominated in the western Powell basin and the eastern Bransfield Strait as a result of transport with the advected Weddell Sea water and drifting sea ice. Using a distribution mixture analysis made possible to identify up to 9–10 size groups of krill. Groups 1–4 corresponds to juveniles (average size about 22, 25, 27–28 and 32 mm respectively). They may reflect the transport of different “waves” of recruitment of the Atlantic sector krill population with the waters of the western branch of Weddell Gyre as well as the presence of juvenile krill of local origin. Groups 5–7 are intermediate in size (average length within 38–43 mm) and include mostly immature specimens. Larger groups 8–10 comprise of mostly mature females and mature and immature males. The maximum average size of the largest group reaches about 53 mm. the Wedell Front zone in the north of Powell Basin plays an in important role for retention and growth of krill, originating from different sources: western Weddell Sea, Bransfield Strait and the zone of the southern branch of Antarctic Circumpolar Current.

Antarctic krill (Euphausia superba) is one of the most abundant commercial species in the world and still has great potential for further development and utilization. It is, however, very important that the resource is utilized in a sustainable manner in terms of efficiency and selectivity, which can be enhanced through proper design of pelagic trawls that are used for harvesting the species. Pelagic trawls rely heavily on hydrodynamic forces acting on the netting to form desirable shapes. It is thus crucial to understand hydrodynamic forces acting on the trawl to predict its performance. A large Antarctic krill trawl with a net opening circumference of 200 m was designed for a fishing vessel (2855 kW) and analyzed by numerical simulation and physical model tests. A numerical model of Antarctic krill trawl was established based on the finite element method. The principle of minimum potential energy was employed to determine the equilibrium configuration and the tension distribution of the trawl in a uniform current. The Newton–Raphson method was applied to solve the equilibrium equation. A series of physical model tests were conducted in a flume tank to verify the result from numerical simulation. The results showed that the trawl with a net opening circumference of 200 m had superior hydrodynamic performance and could be well matched with fishing vessels of the class for the efficient production of Antarctic krill. This paper demonstrates the use of scientific methods for the design of large Antarctic krill trawls and the application of numerical simulation to study the hydrodynamic performance.

Antarctic krill is a vital part of the food web and supports a significant fishery in the Southern Ocean. Shifts in historical fishing grounds and spatial distribution of catches have occurred as a result of recent changes in fishery practices. To understand these shifts, fishery spatial dynamics and fishing fleet behavior evaluated on different spatial and temporal scales are critical. We examine the catch distribution on three spatial-temporal scales. At the Western Antarctic Peninsula (WAP) scale, we assessed the fleet’s southward expansion, identifying the Bransfield Strait (BS) as the main current fishing ground, replacing the historical Drake sector. At the BS scale, we identified fishing hotspots (FHs) that concentrated 48%–57% of the total catch over a period of 2–6 months and had high catch densities (2.2–30.3 ton km−2). At the FH scale, we tracked the spatial distribution of the fleet within FHs, demonstrating a shift of fishing vessels to contiguous zones as a result of a decrease in daily catch rates (CPUE). Such shifts (allowing the fleet to increase CPUE) occurred every 4–17 days. Previously exploited fishing grounds were revisited based on FH persistence and sea ice conditions. This paper concludes with a discussion of the potential impact of fishing fleet behavior and catch concentration, considering the recent spatial shift towards less-exploited areas, the overlap with critical zones for predator feeding, and several implications for fisheries management.

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22037-y

This paper proposes a mathematical model describing the dynamics of both Antarctic krill and Blue whale population where Antarctic krill species (prey) has group defense when they aggregate in herds in order to provide a self-defense from Blue whale species (predator). Firstly, a sufficient condition for the global asymptotical stability of the positive equilibrium is given using Poincaré–Bendixson theorem excluding periodic solution. Furthermore, we discuss the existence of Hopf-bifurcation and give criteria for stability switches through the study of a first-order exponential polynomial characteristic equation. Finally, some numerical simulations are given to illustrate our results.

This study conducted a bibliometric analysis of 1251 articles related to Antarctic krill from 1960 to 2015, based on the Core Collection in Thomson Reuters’ Web of Science. We analyzed the results from four aspects: annual distribution, Web of Science categories and the major journals, international collaboration and author keywords. The Antarctic krill research has developed rapidly since 1978, with an increasing article output. The studies mostly focused on the fields of marine and freshwater biology, oceanography, and ecology. Polar Biology, Marine Ecology-Progress Series and Deep-Sea Research Part II-Topical Studies in Oceanography, were the top three journals to publish the Antarctic krill-related papers. Although Russia is the earliest state to report Antarctic krill, U.S.A. and England were leaders with the largest output quantity and the highest cooperation frequencies. The researches in PR China have taken a blooming since 2009 and will play a more and more important role in the world. Th...

Antarctic krill, Euphausia superba , is a highly abundant and ecologically important zooplankton species in the Southern Ocean. Regions of elevated Antarctic krill biomass exist around Antarctica, often as a result of the concentrating effect of bathymetry and ocean currents. Such areas are considered biological hotspots and are key foraging grounds for numerous top predators in the region. A hotspot of Antarctic krill biomass exists off the southern extent of Anvers Island, Western Antarctic Peninsula, and supports a population of Adelie penguins that feed almost exclusively on it, as well as numerous other top predators. We investigated the spatio-temporal variability in Antarctic krill biomass and aggregation structure over four consecutive summer seasons, identifying environmental factors that were responsible. We identified three distinct krill aggregation types (Large-dense, Small-close and Small-sparse), and found that the relative proportion of each type to total aggregation numbers varied significantly between survey days. Large-dense aggregations occurred more frequently when westerly winds predominated and when the local mixed tide was in the diurnal regime. Small-close aggregations were also more frequent during diurnal tides and were negatively correlated with phytoplankton biomass. Small-sparse aggregations, on the other hand, were more prevalent when the mixed tide was in the semi-diurnal phase. We suggest that, under certain conditions (i.e. diurnal tides and westerly winds), the biological hotspot in the nearshore waters off Palmer Station, Anvers Island, functions as a zone of accumulation, concentrating krill biomass. Our findings provide important information on the dynamics of Antarctic krill at the local scale.

In this paper, a new algorithm based on krill herd actions, named as Antarctic krill Herd Algorithm (AKHA) is proposed for solving optimal reactive power dispatch problem. The AKHA algorithm is based on behavior of krill individuals. The minimum distance of each individual krill from food and from uppermost density of the herd are deliberated as the foremost mission for the krill movement. Projected AKHA algorithm has been tested in standard IEEE 30 bus test system and simulation results shows clearly about the good performance of the proposed algorithm in reducing the real power loss and voltage stability also improved.

This paper (1) reviews the history of sealing and whaling in the Southern Ocean to illustrate how market demands combined with no or ineffective regulation of catches led to the overexploitation and near extinction of southern fur seals, southern elephant seals and all but one of the Southern Ocean populations of large whales; (2) indicates how the overexploitation and depletion of krill-eating whales led to the Krill Surplus Hypothesis, and the development of the Antarctic krill fishery and the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR); (3) points out how misinterpretation of the reference to ‘rational use’ in CCAMLR Article II(2), combined with consensus decision-making and the potential growth of markets for Antarctic krill, could lead to ineffective regulation of the krill fishery and adverse effects on the krill resource, on recovery of depleted populations of krill-dependent whales, and on other ecologically related species and populations; and (4) identifies reasonable actions that could be taken cooperatively by the International Whaling Commission and the CCAMLR Commission to minimise the risk that the krill fishery will prevent or impede recovery of depleted populations of krill-dependent whales.

In the Southern Ocean, it is still not certain that overall krill biomass may decline because of drastic increase in pCO2, and consequent decline in pH. However, there is evidence that ecological vacuums created by krill population collapses caused by ecosystem shifts in Western Antarctic Peninsula (WAP) region led to replacement of Antarctic krill Euphausia superba by soft-bodied salps Salpa thomsoni. There is yet another questionable hypothesis that by the end of 21st century, ocean acidification stress, coupled with thermal increase, may synergistically induce physiologically critical stress to Antarctic krill in some areas of the Southern Ocean, egg development of krill may drastically decrease and in the 23rd century krill may even become extinct. I have earlier reported on normal krill egg development in relation to thermal change and high pressure (George and Stromberg, 1985). Recent experiments on krill development under different pCO2 conditions by Kawaguchi et al. (2011, 2013) suggest that we may witness 20 to 70 % reduction in Antarctic Krill by 2100 as direct consequence of pH decline. Such a scenario may lead to demise of krill-eating top-predators like baleen whales, seals and different species of Antarctic penguin populations. We now know that Adelaide penguins are decreasing in Bransfield Strait region off of the Western Antarctic Peninsula but increasing in Ross Sea region. Such a shift in breeding colonies moving from northern to southern WAP region and Ross Sea areas is not attributed to any decline in krill biomass but recent decadal melting of sea-ice as documented by remote sensing (George and Hayden, 2017). In this paper the main focus revolves around implications of changing chemistry of the Southern Ocean caused by absorption of anthropogenic carbon dioxide.