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The Antarctic krill Euphausia superba is a key species in Antarctic waters, mainly because it is a major component of the diet of dominant predators, including penguins. It is also a marine living resource that is commercially harvested. Since 2000, krill fishing has become more concentrated. On the basis of several years of data, it has been reported that up to 57% of the krill fishery harvests occur in the Bransfield Strait area. The distribution of krill in the Southern Ocean is not well described. Studies that compare the size of krill caught by commercial vessels with that recorded in the diet of predators are even rarer. The main objectives of this study were to assess the spatial diversity in the size and putative age of krill in the CCAMLR subarea 48.1, to investigate the spatial availability of krill and its size and age structure, and to assess whether the diet of Pygoscelis penguins reflects the size structure of krill present in the environment. The results implied that the size and age structure of the krill population were similar throughout the Bransfield Strait during the study period, although those in the eastern and southern parts of the strait and the Brabant Island region were the most similar. The Livingston Island and Drake Passage areas were clearly distinguishable from the above regions, where larger and therefore older krill were recorded. All Pygoscelis penguin species showed size preferences for consumed krill; therefore, their diet is likely not a reliable indicator of the size of krill in the environment. Krill that had not yet reached sexual maturity, and thus not yet started reproducing were commercially caught in the Bransfield Strait during the investigated years. [ABSTRACT FROM AUTHOR]

Krillscan software was developed to automatically process echosounder data and achieve an accelerated and transparent analysis of backscatter data that allows calculation of target biomass. Herein, the fishery for Antarctic krill (Euphausia superba, Henceforth Krill) was used as a case study to develop the approach. Implementation of a sustainable management strategy for the krill fishery is complicated by a lack of regularly updated krill abundance data on spatiotemporal scales of the fishery. To increase krill biomass data availability, automatic echosounder data processing and swarm detection software was tested against traditional manual scrutinization with LSSS software and agreed with only minor offsets in estimated nautical area scattering coefficients. In addition to automatic processing and data transfer, Krillscan also has a graphical user interface to supervise automatic krill swarm detection. Echogram size can be compressed up to 100 times and raw data are processed faster than generated, thereby enabling near‐real time analysis and data transfer. Compressed data can be transmitted online to allow fishing vessels to conduct surveys without having scientific personnel with special expertise on board. [ABSTRACT FROM AUTHOR]

Summary: Boiling, centrifuging and various drying techniques (vacuum freeze‐drying (VFD), vacuum drying (VD), hot‐air drying (HAD) and microwave drying (MWD)) were assessed for their impact on bioactive compounds in Antarctic krill meal. A comparison between the raw and boiling groups revealed a significant degradation and isomerisation of astaxanthin, accompanied by a 1.25‐fold and 1.32‐fold increase in saturated (SFAs) and monounsaturated fatty acids (MUFAs), respectively. Drying was the primary factor responsible for the reduction in phospholipids, α‐tocopherol and polyunsaturated fatty acid (PUFAs), in combination with the increase in thiobarbituric acid‐reactive substances. For different drying methods, it was found that HAD induced severe lipid oxidation. In contrast, the VFD, VD and MWD improved lipid quality, reducing thiobarbituric acid‐reactive substances (TBARS) by 13–22% and increasing phospholipids by 1.08–1.11 times compared to HAD. VD preserved higher levels of bioactive compounds. PLS‐DA analysis identified 13‐cis‐astaxanthin, α‐tocopherol and eleven fatty acids as key indicators for Antarctic krill meal. [ABSTRACT FROM AUTHOR]

Antarctic krill Euphausia superba is a key species in the Southern Ocean ecosystem and has important ecological value. It is also one of the main fishery resources in the Southern Ocean with high economic value. In recent years, with the development of krill fishery and rapid climate change, the conservation and management of krill resources have faced unprecedented challenges. The krill resource is different from the general fishery resources. Due to the krill schooling characteristics, fishery data has some advantages over scientific survey data. Reviewing and analyzing the krill fishery data is necessary. Therefore, in this study, four fishery resource indices (FRIs) were calculated based on Antarctic krill fishery data, and based on the environmental dependence of Antarctic krill, the FRI with the strongest environmental dependence was screened by using the Gradient Forest Model, and the step changes of the FRI with strongest environmental dependence was examined by using the sequential t‐test analyses of regime shifts (STARS). The generalized additive model (GAM) to analyze the correlation between the FRI with the strongest environmental dependence and the main environmental factors, and then explore the resource status of Antarctic krill in the study area. The model results showed that the "FRI_hual" had the strongest environmental dependence and was a better indicator of the status of the Antarctic krill in the study area than the others. In the 2009–2010 year, "FRI_hual" had an obvious regime shift. The interaction of environmental factors "ice_area_2" and "SSH_1" has a great impact on "FRI_hual". Methods used and results obtained in the study can provide new ideas and a scientific reference for future work, including integrated stock assessment of krill and krill resource monitoring, conservation, and management based on the ecosystem. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Heat treatment is widely applied in food processing, but its significant effects on flavor are often overlooked. This study explored how heat treatment impacts the flavor compounds of Antarctic krill. The volatile substances and flavor profiles of Antarctic krill post steaming or hot air drying were analyzed using headspace solid-phase microextraction, gas chromatography-mass spectrometry (HS-SPME-GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), and electronic tongue detection techniques. Free amino acids (FAAs) content, the main flavor precursors, were quantified and compared. The results showed that the FAAs content of SK was the lowest at 48.44 ± 2.10 mg/g db, while the FAAs content of HD_105 was the highest at 67.42 ± 1.77 mg/g db. Drying amplified the flavor intensity of umami and bitter amino acids, while steaming significantly increased the content of the sweet amino acid proline (p < 0.05). The electronic tongue discerned that drying had more pronounced effects than steaming on saltiness, umami, bitterness, and astringency. By combining the volatile organic compounds (VOCs) fingerprints with the results of the GC-MS analysis of five samples, it was observed that the richness in fat and aromatic taste of shrimp powder after hot air drying at 60℃ (HD_60) and 80℃ (HD_80) was enhanced. Krill dried at 105℃ (HD_105) predominantly exhibited a roasted flavor profile, while steamed krill (SK) displayed minimal alterations in volatile flavors. In summary, steaming increased the sweet amino acid content in krill, while drying enhanced krill's aroma characteristics. This study furnishes valuable insights for the subsequent processing and utilization of Antarctic krill to augment its flavor quality. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba, hereafter krill) is a pelagic living crustacean and a key species in the Southern Ocean ecosystem. Krill builds up a huge biomass and its synchronized behavioral patterns, such as diel vertical migration (DVM), substantially impact ecosystem structure and carbon sequestration. However, the mechanistic basis of krill DVM is unknown and previous studies of krill behavior in the laboratory were challenged by complex behavior and large variability. Using a new experimental set-up, we recorded the swimming activity of individual wild-caught krill under light–dark cycles. Krill individuals exhibited differential phototactic responses to the light regime provided. However, using a new activity metric, we showed for the first time a consistent nocturnal increase in krill swimming activity in a controlled environment. Krill swimming activity in the new set-up was strongly synchronized with the light–dark cycle, similar to the diel vertical migration pattern of krill in the field when the krill were sampled for the experiment, demonstrated by hydroacoustic recordings. The new set-up presents a promising tool for investigating the mechanisms underlying krill behavioral patterns, which will increase our understanding of ecological interactions, the spatial distribution of populations, and their effects on biogeochemical cycles in the future. [ABSTRACT FROM AUTHOR]

The northwestern Antarctic Peninsula is an important spawning, recruitment, and overwintering ground for Antarctic krill. The region is warming rapidly, and the current impacts of climate and environmental variability on the reproductive cycle of krill remain unclear. Here, we examine the reproductive stage of female krill in the austral winter from 2012 to 2016 in relation to climate and environmental data to assess what factors influence the timing of reproductive development. We observed significant interannual variability in the degree of maturation in female krill, ranging from 48% of female krill measured at a station in 2016 to a maximum of 94% of female krill measured at a station in 2014. On average, across all five years, three-quarters of the female krill sampled were in the stage known as previtellogenesis, the point at which the onset of sexual maturity begins. The preceding spring, summer, and autumn Southern Annular Mode and the Multivariate El Niño Index explained most of the variance in the data and indicated a strong, preconditioning storm-related effect on environmental conditions leading up to winter, affecting krill maturation status at the end of the winter season. Results from our study can be used to improve krill population models that are necessary for the management of the krill fishery and for conservation at the northwestern Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

Summary: In this study, the effect of short‐term storage at different temperatures (0, 4 and −8 °C) on the quality of Antarctic krill was investigated using the main quality indicators as a reference, combined with electronic nose and untargeted metabolomics. Antarctic krill stored at lower temperatures (−8 °C) were of better quality and had a flavour similar to that of the original Antarctic krill. Metabolomics analyses showed that differential metabolites (DMS) were more abundant in Antarctic krill at higher temperatures (4 °C), with sixty‐five metabolites having reduced expression and forty‐five metabolites having increased expression; Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that amino acid metabolism and nucleotide metabolism pathways were the Five DMS, including α‐ketoglutarate, glutamate, succinate, sucrose and glutarate, can be used as potential biomarkers to monitor quality changes during short‐term storage of Antarctic krill. In addition, the association between quality indicators and differential metabolites remains to be explored. [ABSTRACT FROM AUTHOR]

Phosphatidylcholine (PC), phosphatidyl ethanolamine (PE), phosphatidylserine (PS), and phosphatidylinositol (PI) are the four major phospholipids in Antarctic krill. In this study, the composition of these phospholipids was analyzed by hydrophilic interaction ultra-high performance liquid chromatography-tandem mass spectrometry (HILIC-UPLC-MS/MS) after purification by solid-phase extraction (SPE) using titania-coated fibrous silica (TiO2/KCC-1) nanoparticles, which had been prepared in our laboratory. The results showed that under the optimal conditions, 291 phospholipids including 75 PCs, 120 PEs, 54 PIs and 42 PSs were detected, which were nearly twice as many as those detected by a previously reported method. Phospholipids containing monounsaturated and polyunsaturated fatty acid chains accounted for 54.73% and 26.17% of the total phospholipids, respectively. PC (40:6) (41.63%), PE (36:0) (39.77%), PI (38:3) (80.05%), and PS (36:1) (81.62%) were found to be the most abundant in the four phospholipids. Multivariate statistical analysis showed significant differences in the types of phospholipids before and after SPE treatment. TiO2/KCC-1 nanoparticles exhibited a significant enrichment capacity for phospholipids, especially PC (18:0/18:0), PE (16:0/18:1), and PI (16:0/18:2). The detection limit was 0.05 μg/g for PC, PE and PS, and 0.01 μg/g for PI. The relative standard deviations (RSDs) for the four major phospholipids were in the range of 0.89% to 5.05%, and the recoveries were 87%–112%. This method demonstrated high specificity, extraction efficiency, sensitivity, precision and accuracy. Therefore, it has broad application prospects for the extraction, purification, and analysis of phospholipids in biological samples.

Abstract Antarctic krill (Euphausia superba, hereafter krill) is a pelagic living crustacean and a key species in the Southern Ocean ecosystem. Krill builds up a huge biomass and its synchronized behavioral patterns, such as diel vertical migration (DVM), substantially impact ecosystem structure and carbon sequestration. However, the mechanistic basis of krill DVM is unknown and previous studies of krill behavior in the laboratory were challenged by complex behavior and large variability. Using a new experimental set-up, we recorded the swimming activity of individual wild-caught krill under light–dark cycles. Krill individuals exhibited differential phototactic responses to the light regime provided. However, using a new activity metric, we showed for the first time a consistent nocturnal increase in krill swimming activity in a controlled environment. Krill swimming activity in the new set-up was strongly synchronized with the light–dark cycle, similar to the diel vertical migration pattern of krill in the field when the krill were sampled for the experiment, demonstrated by hydroacoustic recordings. The new set-up presents a promising tool for investigating the mechanisms underlying krill behavioral patterns, which will increase our understanding of ecological interactions, the spatial distribution of populations, and their effects on biogeochemical cycles in the future.

We examined the dB difference in target strength at multiple frequencies (ΔTS) for the identification of Antarctic krill (Euphausia superba) and ice krill (Euphausia crystallorophias) using a stochastic distorted-wave Born approximation model. Our investigation focused on ΔTS patterns at multiple frequencies in relation to size, along with key acoustic properties influencing TS, including density and sound speed contrast, fatness, and orientation. The findings revealed that the orientation and fatness significantly affect the ΔTS patterns. The results provide insight into the importance of the multi-frequency technique for estimating krill biomass and their ecological interactions with environmental features in the Southern Ocean.

Summary: The impact of κ‐carrageenan on the physicochemical structural characteristics of ready‐to‐eat (RTE) Antarctic krill surimi gel (AKSG) was investigated. The modifications in chemical bonding, protein secondary structure, protein composition and microscopic morphology were compared in both gels with and without κ‐carrageenan. According to the findings, adding 4% (w/w) κ‐carrageenan could reduce the cooking loss of AKSG significantly (P < 0.05), enhance the WHC and textural quality of AKSG and RTE AKSG and increase the amount of hydrophobic and disulfide bonds so that the secondary structure of Antarctic krill proteins could be shifted to the β‐sheet. However, there was little impact on the composition of the protein molecules according to the SDS‐PAGE. In addition, the usage of κ‐carrageenan significantly alleviated the disruption of the protein gel network caused by high‐temperature and high‐pressure treatments (P < 0.05). Therefore, applying κ‐carrageenan could effectively enhance the gel quality of RTE AKSG. [ABSTRACT FROM AUTHOR]

During postmortem storage, fluoride in Antarctic krill can be enriched in the muscle. Trypsin, as the most important digestive enzyme in Antarctic krill with a high activity in low temperature, plays a potential role in this process. In this study, endogenous trypsin was purified and its properties were investigated. The involvement of trypsin in the generation of free fluoride from Antarctic krill cuticle was explored. Cuticle microstructure before and after hydrolysis was compared with scanning electron microscopy, and the ash samples of the hydrolyzed Antarctic krill cuticle were analyzed with X-ray diffraction, Fourier transform infrared spectroscopy, and electron dispersive spectroscopy, respectively. Mass spectrometry analysis and inhibition tests confirmed that the purified enzyme was endogenous trypsin. Results of the present study indicated that trypsin digestion caused the increases of the concentrations of both fluoride ions and free amino N simultaneously, while the protein coated on the cuticle surface was dissolved too. However, no compositional change was detected in the cuticle inorganic salts. These findings suggest that trypsin triggered free fluoride release from Antarctic krill cuticle. In addition, the kinetics of free fluoride release could be described by the equation CW = (1−0.97−0006t −0.03e0.0558t)×337.53+10.50. The present study improved the understanding of the role of trypsin in free fluoride release from Antarctic krill cuticle, facilitating future studies aimed at reducing the fluoride content in krill protein during Antarctic krill processing. [ABSTRACT FROM AUTHOR]

To grasp the drying characteristics of Antarctic krill ( Euphausia superba ) under the heating conditions of the spiral bushing heating, a drying model was established to simulate the moisture migration pattern during the drying process accurately. The trends of moisture content, drying rate, the effective diffusion coefficient of moisture and activation energy of drying of Antarctic krill were investigated at different drying temperatures (90 ℃, 110 ℃, 130 ℃), stack thicknesses (10 cm, 20 cm, 30 cm) and stirring speeds (4 r/ min, 6 r/ min, 8 r/ min). The drying curves were analyzed, and the experimental data were fitted by eight classical drying models chosen to simulate the moisture migration accurately during the drying process. Eight classical drying models were selected to fit the experimental data. The coefficient of determination R², the chisquare test value X², and the root mean square error RMSE were used as the evaluation indexes of the model fitting effect to determine the optimal drying model, and regression analysis was carried out on the model parameters to obtain the most suitable drying model fitting equations. The results showed that:the drying process of Antarctic krill spiral bushing heated drying belongs to the descending speed drying; the drying rate reaches the maximum value within 10min from the beginning of drying; the descending drying stage is the main stage of drying, and the constant - speed drying stage is less; the relationship of effective moisture diffusion coefficient of the Antarctic krill is drying temperature >stack thickness>stirring speeds; and the effective diffusion coefficient of moisture within the range of test conditions is 1. 920 9×10-9 -3. 971 7×10-9, and the activation energy of drying is 15. 64 kJ/mol, which is easy to dry; the Logarithmic model is the best model for the heating and drying of Antarctic krill spiral bushing heated drying, and the fitted equation of this model can predict the change of moisture ratio in the drying process of Antarctic krill better. The study results can provide a new drying mode for the processing of Antarctic krill powder, and provide theoretical basis and technical support for the research and development of spiral bushing heating and drying process and equipment development. [ABSTRACT FROM AUTHOR]

The northwestern Antarctic Peninsula is an important spawning, recruitment, and overwintering ground for Antarctic krill. The region is warming rapidly, and the current impacts of climate and environmental variability on the reproductive cycle of krill remain unclear. Here, we examine the reproductive stage of female krill in the austral winter from 2012 to 2016 in relation to climate and environmental data to assess what factors influence the timing of reproductive development. We observed significant interannual variability in the degree of maturation in female krill, ranging from 48% of female krill measured at a station in 2016 to a maximum of 94% of female krill measured at a station in 2014. On average, across all five years, three-quarters of the female krill sampled were in the stage known as previtellogenesis, the point at which the onset of sexual maturity begins. The preceding spring, summer, and autumn Southern Annular Mode and the Multivariate El Niño Index explained most of the variance in the data and indicated a strong, preconditioning storm-related effect on environmental conditions leading up to winter, affecting krill maturation status at the end of the winter season. Results from our study can be used to improve krill population models that are necessary for the management of the krill fishery and for conservation at the northwestern Antarctic Peninsula.

The response to climate change in highly dimorphic species can be hindered by differences between sexes in habitat preferences and movement patterns. The Antarctic fur seal, Arctocephalus gazella, is the most abundant pinniped in the Southern Hemisphere, and one of the main consumers of Antarctic krill, Euphausia superba, in the Southern Ocean. However, the populations breeding in the Atlantic Southern Ocean are decreasing, partly due to global warming. Male and female Antarctic fur seals differ greatly in body size and foraging ecology, and little is known about their sex‐specific responses to climate change. We used satellite tracking data and Earth System Models to predict changes in habitat suitability for male and female Antarctic fur seals from the Western Antarctic Peninsula under different climate change scenarios. Under the most extreme scenario (SSP5‐8.5; global average temperature +4.4°C projected by 2100), suitable habitat patches will shift southward during the non‐breeding season, leading to a minor overall habitat loss. The impact will be more pronounced for females than for males. The reduction of winter foraging grounds might decrease the survival of post‐weaned females, reducing recruitment and jeopardizing population viability. During the breeding season, when males fast on land, suitable foraging grounds for females off the South Shetland Islands will remain largely unmodified, and new ones will emerge in the Bellingshausen Sea. As Antarctic fur seals are income breeders, the foraging grounds of females should be reasonably close to the breeding colony. As a result, the new suitable foraging grounds will be useful for females only if nearby beaches currently covered by sea ice emerge by the end of the century. Furthermore, the colonization of these new, ice‐free breeding locations might be limited by strong female philopatry. These results should be considered when managing the fisheries of Antarctic krill in the Southern Ocean. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Antarctic krill (Euphausia superba) is a source for compounds of high nutritive value. Within that process of extraction, exocuticles (shells) accumulate which are currently disposed. A valorization of the compounds of the exocuticle such as chitosan would be beneficial to avoid waste and to obtain a versatile polymer at the same time. In contrast to previous investigations focusing on chitosan production from whole krill, we applied and optimized process stages of the chitosan production from the exocuticles, performing a comprehensive analytical evaluation of the whole process, the side streams and the products for the first time. Degreasing was the first step resulting in a krill oil yield of 6.2% using ethanol. The fatty acid profile exhibited high contents of phospholipids (21.2%). Citric acid offered a demineralization efficiency of 93%. Deproteinization investigation revealed 2 M NaOH and 90°C for 2.5 h to be the best parameters, resulting in a deproteinization efficiency of 99.9% and a chitin content of 92.8%. The spectroscopic investigation indicated that the chitin has a crystallinity index of 76% and an acetylation degree of 88%. The deacetylation degrees of the resulting chitosans is determined to be 74%–88%, the molecular weight ranges from 102 to 126 kDa. [ABSTRACT FROM AUTHOR]

ABSTRACTWith almost a quadrillion individuals, the Antarctic krill processes five million tons of organic carbon every day during austral summer. This high carbon flux requires a broad range of hydrolytic enzymes to decompose the diverse food-derived biopolymers. While krill itself possesses numerous such enzymes, it is unclear, to what extent the endogenous microbiota contribute to the hydrolytic potential of the gut environment. Here we applied amplicon sequencing, shotgun metagenomics, cultivation, and physiological assays to characterize the krill gut microbiota. The broad bacterial diversity (273 families, 919 genera, and 2,309 species) also included a complex potentially anaerobic sub-community. Plate-based assays with 198 isolated pure cultures revealed widespread capacities to utilize lipids (e.g., tributyrin), followed by proteins (casein) and to a lesser extent by polysaccharides (e.g., alginate and chitin). While most isolates affiliated with the genera Pseudoalteromonas and Psychrobacter, also Rubritalea spp. (Verrucomicrobia) were observed. The krill gut microbiota growing on marine broth agar plates possess 13,012 predicted hydrolyses; 15-fold more than previously predicted from a transcriptome-proteome compendium of krill. Cultivation-independent and -dependent approaches indicated members of the families Flavobacteriaceae and Pseudoalteromonadaceae to dominate the capacities for lipid/protein hydrolysis and to provide a plethora of carbohydrate-active enzymes, sulfatases, and laminarin- or porphyrin-depolymerizing hydrolases. Notably, also the potential to hydrolyze plastics such as polyethylene terephthalate and polylactatide was observed, affiliating mostly with Moraxellaceae. Overall, this study shows extensive microbial diversity in the krill gut, and suggests that the microbiota likely play a significant role in the nutrient acquisition of the krill by enriching its hydrolytic enzyme repertoire.IMPORTANCEThe Antarctic krill (Euphausia superba) is a keystone species of the Antarctic marine food web, connecting the productivity of phyto- and zooplankton with the nutrition of the higher trophic levels. Accordingly, krill significantly contributes to biomass turnover, requiring the decomposition of seasonally varying plankton-derived biopolymers. This study highlights the likely role of the krill gut microbiota in this ecosystem function by revealing the great number of diverse hydrolases that microbes contribute to the krill gut environment. The here resolved repertoire of hydrolytic enzymes could contribute to the overall nutritional resilience of krill and to the general organic matter cycling under changing environmental conditions in the Antarctic sea water. Furthermore, the krill gut microbiome could serve as a valuable resource of cold-adapted hydrolytic enzymes for diverse biotechnological applications.

Objective: The purpose of this study was to investigate the drying characteristics and establish the kinetic model of Antarctic krill during spin-flash drying. The drying experiments were carried out at 120 ℃ to 180 ℃. Methods: Six common thin-layer drying models were selected to fit the experimental data. Further, the equations of drying model constant and temperature were established to obtain the model expression and validate the optimal drying model. The effective moisture diffusion coefficients were calculated by Fick's second law. Results: The results showed the drying temperature had a significant effect on drying thermal efficiency and drying rate. The spin-flash drying of Antarctic krill was a falling rate drying process at 130 ℃ to 180 ℃. The Page model was suitable for describing and predicting the spin-flash drying process of Antarctic krill. The constant term equations of the model were established by regression analysis, which were k=exp（-27.532 1+0.301 8T-8.538 2×10-4T2）and n=14.010 6-0.157 67T+4.750 9×10-4T2. As the drying temperature increasing, the effective moisture diffusion coefficient increased from 2.539 35×10-7 m2/s to 13.889 64×10-7 m2/s. Conclusion: The spin-flash drying method had the advantages of higher effective moisture diffusion coefficient and higher drying efficiency, which can effectively protect the thermal sensitive composition in Antarctic krill from being damaged and improve the product quality.

Objective: To promote the intensive processing of Antarctic Krill and enrich the types of minced shrimp products. Methods: Using Krill meat and prawn meat as main raw materials, waxy corn acetylated distarch adipate, egg white powder, soy protein isolate, glutamine transaminase and other adjuvants were added, and the optimal preparation ratio of shrimp balls was obtained through single factor test and response surface test. Results: The optimal preparation ratio of shrimp balls was 6.00% waxy corn acetylated distarch adipate, 5.00% egg white powder, 5.00% soy protein isolate, 0.50% glutamine transaminase and 0.20% konjac gum. Conclusion: The two-stage heating method is used to prepare compound shrimp gel. By adding exogenous additives, the texture properties of compound shrimp gel can be improved and the nutritional value can be guaranteed.

With environmental change, understanding how species recover from overharvesting and maintain viable populations is central to ecosystem restoration. Here, we reconstruct 90 years of recovery trajectory of the Antarctic fur seal at South Georgia (S.W. Atlantic), a key indicator species in the krill‐based food webs of the Southern Ocean. After being harvested to commercial extinction by 1907, this population rebounded and now constitutes the most abundant otariid in the World. However, its status remains uncertain due to insufficient and conflicting data, and anthropogenic pressures affecting Antarctic krill, an essential staple for millions of fur seals and other predators. Using integrated population models, we estimated simultaneously the long‐term abundance for Bird Island, northwest South Georgia, epicentre of recovery of the species after sealing, and population adjustments for survey counts with spatiotemporal applicability. Applied to the latest comprehensive survey data, we estimated the population at South Georgia in 2007–2009 as 3,510,283 fur seals [95% CI: 3,140,548–3,919,604] (ca. 98% of global population), after 40 years of maximum growth and range expansion owing to an abundant krill supply. At Bird Island, after 50 years of exponential growth followed by 25 years of slow stable growth, the population collapsed in 2009 and has thereafter declined by −7.2% [−5.2, −9.1] per annum, to levels of the 1970s. For the instrumental record, this trajectory correlates with a time‐varying relationship between coupled climate and sea surface temperature cycles associated with low regional krill availability, although the effects of increasing krill extraction by commercial fishing and natural competitors remain uncertain. Since 2015, fur seal longevity and recruitment have dropped, sexual maturation has retarded, and population growth is expected to remain mostly negative and highly variable. Our analysis documents the rise and fall of a key Southern Ocean predator over a century of profound environmental and ecosystem change. [ABSTRACT FROM AUTHOR]

The present study is the attempt to combine oceanologic measurements and biochemical analysis, which is as possible to implement on board as in a laboratory with chosen certain statistics to reveal trophic conditions and the environment state in which Antarctic krill live in season in real time on site. The fatty acid constituents of total lipids in juvenile and mature Antarctic krill sampled from the Bransfield Strait (BS), the Antarctic Sound (AS), and waters at the eastern tip of the Antarctic Peninsula (AP) collected during the 87th cruise of the R/V Akademik Mstislav Keldysh in January–February 2022 were analyzed. The fatty acid (FA) profile in juvenile and mature Antarctic krill was studied by gas chromatography with a mass selective detector to identify the qualitative composition and a flame ionization detector to quantify the studied FAs. Using NMDS analysis (quantitative panel), great difference was found between krill from the BS compared to krill collected in the AS and the AP. The differences are reliable owing to the following 16 FAs, most of them trophic biomarkers of microphytoplankton, and suggest regional differences, mainly in abundance and ability of forage objects. CTD measurements discuss the abiotic factors (potential temperature, salinity, and chlorophyll "a"). Compensatory modifications of the composition of FA components in Antarctic krill inhabiting different water areas are a way of maintaining the species' viability under certain and variable habitat conditions. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Antarctic krill (Euphausia superba) is a keystone species in the Southern Ocean ecosystem, and monitoring its distribution and abundance is crucial for the sustainable management of expanding fisheries targeting the species. Environmental DNA (eDNA)‐based monitoring could complement conventional krill surveys, but its applicability is limited by a lack of knowledge on eDNA persistence and decay in the Southern Ocean. We aimed to develop a method that can not only quantify Antarctic krill eDNA, but also estimate a relative time since this eDNA was shed (“recent” vs “older”). Three species‐specific qPCR markers targeting the mitochondrial 16S region were developed, and the eDNA decay characteristics of these markers were determined through tank experiments. Krill eDNA was partially degraded in all samples, even when krill were present. Marker concentrations decreased exponentially at similar rates after krill removal, with initial relative abundances maintained across the three markers. Over time, the concentration of the longest marker decreased faster, changing the relative abundances of the markers, and allowing discrimination of more recent samples from more degraded older samples. We employed this new method to quantify Antarctic krill eDNA collected across a 4800 km Southern Ocean transect, and estimated the age of the eDNA in these samples based on the relative abundance of markers, adding a temporal aspect to a quantitative eDNA survey. We also compared a Euphausiid‐specific metabarcoding marker to the qPCR method to assess sensitivity in detecting Antarctic krill eDNA. While these new eDNA methods should be evaluated against existing non‐molecular survey methods, they could add an important novel, dynamic layer of information to future krill surveys. Our method could not only determine where Antarctic krill eDNA is present but shed light on how they may be using certain habitats, expanding our understanding of this important species’ life cycle and contributing to more accurate abundance and distribution estimates.

In order to explore a kind of hot-air drying of Antarctic krill under variable temperature process, the drying time, protein, fat and astaxanthin content were taken as indicators, the effects of first phase of the drying temperature, second phase of the drying temperature and moisture content point on the drying effect of Antarctic krill were studied, the drying effect was evaluated by multi-index comprehensive scoring method, the drying technology of dried Antarctic krill was optimized by orthogonal optimization test based on single factor experiments. The results showed that the optimum hot-air drying of Antarctic krill under variable temperature process were first phase of the drying temperature 55 ℃, second phase of the drying temperature 85 ℃, moisture content point 50%. The dried Antarctic krill obtained by this optimized process were the content of protein, fat, astaxanthin and drying time 69.24%, 19.79%, 232.72 μg/g, 300 min, respectively, and the comprehensive score of drying effect was 99.05.

To reduce costs associated with the detection and population assessment of Antarctic krill and diversify the single detection approach, our team designed and deployed a drifting sonar buoy for krill detection in the waters surrounding Antarctica. The experimental results indicate that the drifting sonar buoy fulfills its primary functions and meets the requirements for krill detection in designated marine areas. The initial experiment lasted seven days, during which the buoy collected 157 records of speed and location data as well as 82 records of sea surface temperature and acoustic data, demonstrating its potential for krill detection. The experiment also revealed shortcomings in the initial design of the drifting sonar buoy, leading to proposed improvements. The paper further compares the advantages and disadvantages of the drifting sonar buoy and traditional fishing vessels in krill detection with the buoy offering unique benefits in low-cost deployment, labor savings, broad monitoring range, and continuous real-time data monitoring. The drifting sonar buoy serves as an excellent complement to fishing vessels in krill detection.

The waters near the Antarctic Peninsula are characterized with unique oceanographic conditions and rich krill resources. Based on samples collected around the South Shetland Islands (SSI) in austral summer of 2019/2020, the net- phytoplankton community structure and relevant major biotic and abiotic influencing factors were investigated. Eighty-one taxa were identified by light microscope, and diatoms were the most abundant group. The most abundant species were Chaetoceros atlanticus, C. criophilus, C. dichaeta, Fragilariopsis kerguelensis and Pseudo−nitzschia lineola. The abundance and Shannon-Weaver index of net-phytoplankton ranged from 100 to 2.64×107 cells/m3 and 0.0747 to 4.0176 respectively, with significantly low values detected in the Bransfield Strait (BS) and high values in the west of the SSI. The dissimilarity was mainly caused by the differences in abundance of diatoms (including Thalassiothrix antarctica and the species in genus Rhizosolenia, Chaetoceros, Fragilariophsis). These diatoms and Dictyocha speculum were found in higher abundance in the west of the SSI, while Corethron pennatum and cryptophytes were found in higher abundance in the BS. Combined with acoustic density of krill and environmental data (Sea Surface Temperature and Sea Ice Concentration). The multivariate analysis suggested that phytoplankton community was positively affected by the SST, and the acoustic- derived krill density would be associated with the spatial distribution of pennate diatoms. This study enhances the knowledge about the selective feeding for krill and provides ecological implications for the Antarctic marine ecosystem.

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Antarctic krill (Euphausia superba) is a key species of the Antarctic ecosystem whose unique ecological status and great development potential have attracted extensive attention. However, the genomic characteristics and potential biological functions of the symbiotic microorganisms of Antarctic krill remain unknown. In this study, we cultured and identified a strain of Brucella sp. WY7 from Antarctic krill using whole-genome sequencing and assembly, functional annotation, and comparative genomics analysis. First, based on 16S rDNA sequence alignment and phylogenetic tree analysis, we identified strain WY7 as Brucella. The assembled genome of strain WY7 revealed that it has two chromosomes and a plasmid, with a total genome length of 4,698,850 bp and an average G + C content of 57.18%. The DNA—DNA hybridization value and average nucleotide identity value of strain WY7 and Brucella anthropi ATCC® 49188TM, a type strain isolated from human clinical specimens, were 94.8% and 99.07%, respectively, indicating that strain WY7 is closely related to Brucella anthropi. Genomic island prediction showed that the strain has 60 genomic islands, which may produce HigB and VapC toxins. AntiSMASH analysis results showed that strain WY7 might produce many secondary metabolites, such as terpenes, siderophores and ectoine. Moreover, the genome contains genes involved in the degradation of aromatic compounds, suggesting that strain WY7 can use aromatic compounds in its metabolism. Our work will help to understand the genomic characteristics and metabolic potential of bacterial strains isolated from Antarctic krill, thereby revealing their roles in Antarctic krill and marine ecosystems. [ABSTRACT FROM AUTHOR]

In order to study the effect of ultrasound-assisted thawing on the quality of Antarctic krill (Euphausia superba) and its changes during cold storage, frozen Antarctic krill was placed into net bags or polyethylene (PE) bags and thawed by water immersion with or without ultrasound treatment. The quality changes of thawed samples during cold storage were evaluated in terms of sensory scores, microbial growth, hardness, total volatile basic nitrogen (TVB-N) content, polyphenol oxidase (PPO) activity and trypsin activity as well as the signal intensity of hydrogen protons in low field nuclear magnetic resonance. The thawing time was 105 and 145 min for net bag and plastic bag packaging combined with water immersion thawing, respectively, while it took only 65 and 75 min for net bag and plastic bag packaging combined with ultrasound-assisted immersion thawing. After thawing, the sensory score of Antarctic krill continued to decline during storage at 4 ℃ and reached an unacceptable level after 24 h of storage. However, the total viable count remained less than 2.5 (lg (CFU/g)) before and after thawing and during subsequent cold storage for 28 h, but the activity of PPO and trypsin increased firstly and decreased at the end of storage, while TVB-N content increased during storage. The quality of thawed Antarctic krill contained in net bags deteriorated more slowly than in plastic bags. Collectively, net bag packaging combined with ultrasound-assisted thawing can not only accelerate the thawing rate, but also improve the storability of Antarctic krill.

Understanding the vertical migration behaviour of Antarctic krill is important for understanding spatial distribution, ecophysiology, trophic interactions and carbon fluxes of this Southern Ocean key species. In this study, we analysed an eight-month continuous dataset recorded with an ES80 echosounder on board a commercial krill fishing vessel in the southwest Atlantic sector of the Southern Ocean. Our analysis supports the existing hypothesis that krill swarms migrate into deeper waters during winter but also reveals a high degree of variability in vertical migration behaviour within seasons, even at small spatial scales. During summer, we found that behaviour associated with prolonged surface presence primarily occurred at low surface chlorophyll a concentrations whereas multiple ascent–descent cycles per day occurred when surface chlorophyll a concentrations were elevated. The high plasticity, with some krill swarms behaving differently in the same location at the same time, suggests that krill behaviour is not a purely environmentally driven process. Differences in life stage, physiology and type of predator are likely other important drivers. Finally, our study demonstrates new ways of using data from krill fishing vessels, and with the routine collection of additional information in potential future projects, they have great potential to significantly advance our understanding of krill ecology.

At present, the primary fishing method of Antarctic krill is beam trawl, in which the fishing vessel drags the beam equipped with nets through the trawl warp for midwater trawling. Due to the behavioral characteristic of collective activities, the shoal of Antarctic krill often appears in some specific depths of the sea. The existing fishing method needs to adjust the trawling depth by modifying the length of the trawl warp and the navigation speed of the vessel, which cannot adjust the trawling depth independently. To solve this problem, we proposed a depth variable device installed on the beam to adjust the trawling depth independently, aiming to track the depth where the shoal of Antarctic krill is located for accurate fishing. Investigate the hydrodynamic feature of the proposed beam trawl device by numerical analysis and water channel experiment to design the wing's profile and determine the effective range of angle of attack. It was found that when the angle of attack of the wing is 0°–17.7°, the regulation effect of depth adjusting is better. The analysis results can be used as the parameter basis for compiling the control program for the depth variable beam. [ABSTRACT FROM AUTHOR]

Chitin was prepared from Antarctic krill shells, and then it was prepared into chitin nano-whiskers by TEMPO oxidation method, and chitosan/fish glue/chitin nano-whisker composite film materials were prepared by adding different additions of chitin nano-whiskers into chitosan/fish glue matrix. The chitin nano-whiskers were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier infrared spectroscopy (FTIR). The composite membrane materials were examined by SEM, optical transmittance, XRD and thermogravimetric analysis (TG), and the degradability of the composite membrane materials was tested by subcutaneous embedding experiments in mice. The results showed that the chitin nano-whiskers prepared from Antarctic krill shells were needle-like or fibrous with an average diameter of 17 nm. The chitin nano-whiskers were uniformly dispersed in the composite membrane material, and the tensile strength of the composite membrane reached a maximum of 18.37 MPa when the addition amount of chitin nano-whiskers was 7%, which was 160% higher than that of chitosan/fish glue membrane. This indicates that the addition of nano-whiskers into the composite film can significantly improve its mechanical strength. The subcutaneous degradation experiments in mice showed that the degradation rate of the composite membrane with nano-whisker addition became slower, and the degradation rate of the membrane with 7% nano-whisker addition was 66.3% at the ninth week. [ABSTRACT FROM AUTHOR]

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Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly. Studies of the feeding strategies of these two krill species will help us better understand the coexistence mechanisms and estimate the roles that krill played in the food web of the Southern Ocean. The trophodynamics of E. superba and T. macrura at different ontogenetic stages (furcilia, juvenile, adult) were studied using fatty acid and stable isotope biomarkers in the samples collected in Amundsen Sea during austral summer of 2017/2018 and 2018/2019. Diatoms like Fragilariopsis spp. was the most abundant phytoplankton species in the summer of 2017/2018, while the abundance of phytoplankton in the summer of 2018/2019 was dominated by Phaeocystis sp. The gradual increase of the carnivorous index 18:1n–9/18:1n–7 with ontogeny of both species in 2018/2019 indicated more carnivorous feeding of adults compared with juveniles and larvae. Meanwhile, greater δ15N values of T. macrura than that of E. superba were more significant in the juvenile and adult stages during the summer of 2018/2019. Our results indicate that the trophic niche differentiation between the two krill species appeared in postlarval stage and can be influenced by food availability. Compared with E. superba, T. macrura was more prone to feed omnivorously or carnivorously responding to food availability. [ABSTRACT FROM AUTHOR]

There is an emerging consumption of the Antarctic krill (AK) muscle‐based food due to its excellent nutritional value and enormous biomass storage capacity. However, the coarse texture of the muscle and the weak gelling properties of AK protein impede its expansion in surimi‐based products. This investigation successfully prepared heat‐induced gels of AK surimi with desirable textural properties by including Litopenaeus vannamei in varying proportions. Higher concentrations of L. vannamei resulted in improved three‐dimensional printability, greater water‐holding capacity (WHC), larger viscoelastic modulus, and a well‐formed microstructural matrix of AK surimi, due to an increased level of myofibrillar protein. Compared with AK, L. vannamei muscle had double the salt‐soluble protein content, which was corroborated by increased intensity of bands of actin, paramyosin, tropomyosin, and myosin light chains on reducing SDS‐PAGE. DSC results indicated that a high ratio of L. vannamei elevated the denaturation temperature and enthalpy of myosin, sarcoplasmic protein, and actin, suggesting a high degree of cross‐linking. It was also found that when hydroxypropyl cassava starch was added at 0.5% (w/w), WHC and gel strength were further improved with a more compact gel matrix. The successful preparation of unwashed mixed surimi with AK meat fully exploited in this study provides an option for AK surimi‐based product industrialization. [ABSTRACT FROM AUTHOR]

To investigate the potential of high-protein krill meal (HPK) to improve growth in low-cost diets for Pacific white shrimp (Litopenaeus vannamei), a commercial control and a 3% HPK diet were compared. To simulate a semi-intensive culture system, a total of 4,500 shrimp with a body weight (BW) of 3.07 ± 0.01 g were stocked with 25 animals/m2 in 20 cages in a 2.16-ha pond. After 60 days of rearing, the 3% HPK diet achieved a significantly higher yield (22,094.0 ± 130.35 g/cage) in comparison to the control diet (19,301.6 ± 272.28 g/cage) (P < 0.05). When the feed cost per kg shrimp produced was compared, it was significantly lower in the 3% HPK group (US$1.01/kg shrimp) when compared to the control group (US$1.11/kg shrimp). The results indicate that low feeding cost diets can profit from the partial replacement of fish meal by HPK to optimize shrimp growth performance without increasing formula cost. [ABSTRACT FROM AUTHOR]

In order to optimize the decolorization process of Antarctic krill peptides and improve the product quality, activated carbon adsorption method was used to remove the pigment from the Antarctic krill peptides solution. Taking the decolorization rate and protein retention rate as the evaluation indexes, the influence of four independent variables including dosage of activated carbon, pH, decolorization temperature and decolorization time on the decolorization effect were investigated respectively. On the basis of single factor experiment, three independent variables including dosage of activated carbon, pH and decolorization time were optimized by the response surface methodology under the decolorization temperature of 50 ℃. Results showed that powdered activated carbon was more suitable for the removal of pigment from Antarctic krill peptides when compared with granular activated carbon, and the optimal conditions determined by response surface methodology were as follows: dosage of activated carbon 4.0%, pH1.5 and decolorization time 1.0 h. Under the optimal conditions, the decolorization rate was 82.19%±0.20% and the protein retention rate was 90.93%±2.28%. The decolorization treatment had no obvious effects on the proportion of essential amino acids and nonessential amino acids in the amino acid compositions as well as the molecular weight distribution of Antarctic krill peptides. This research would provide scientific support for the development of high-quality Antarctic krill peptides products.

Antarctic krill is widely distributed in Antarctic waters, with rich resource reserves. It is the largest single catching biological resource in the world′s oceans. This paper combed the operation of global Antarctic krill fishing and processing ships, analyzed the development and utilization of Antarctic krill and the development status of fishing and processing ships in major countries, selected "Furong Sea" and "Antarctic Endurance", made a comparative analysis between China′s Antarctic krill fishing and processing ships and Norwegian fishing boats, and pointed out that there were still some problems in the development of Chinese Antarctic krill fishing and processing ships. There were problems in the production mode, the traditional fishing methods of fishing vessels needed to be improved and the on-board processing technology needed to be further improved. Based on this, it was considered that China should promote transformation and upgrading and form a new Antarctic krill fishing and processing fishing vessel system in the future; strengthen the industrial quality and constantly improve the fishing gear and equipment level of fishing vessels; improve the processing links and break through the bottleneck of on-board processing technology, to provide help to the development of China′s Antarctic krill fishing industry.

Krill and salps play a pivotal role in marine food webs and ocean biogeochemistry, yet little is known about their stoichiometry, which is crucial for our understanding of the consequences of key grazer population shifts for ecosystem functioning. To assess differences in stoichiometric requirements, we compared the elemental composition of carbon (C), nitrogen (N) and phosphorus (P) in body tissue and gut content of Euphausia superba and Salpa thompsoni collected along the Northern Antarctic Peninsula and conducted a systematic literature review on the stoichiometry of 33 euphausiid and 19 salp species. Our data revealed significantly lower body C:P and N:P ratios but higher gut content N:P in S. thompsoni compared with E. superba , suggesting higher P uptake. In contrast, literature data showed higher C:N, C:P and N:P ratios in salps, potentially indicating lower nutrient demand compared with krill. However, literature data exhibited high intra- and interspecific variability potentially driven by organism size, seasonal or latitudinal variations, emphasizing that nutritional requirements are not only related to the target species, but also to its habitat. Our study provides valuable stoichiometric information for future experimental and modeling studies, fostering our ability to predict the future role of krill and salps for ocean biogeochemistry. [ABSTRACT FROM AUTHOR]

Antarctic krill (Euphausia superba) of the Euphausiidae family comprise one of the largest biomasses in the world and play a key role in the Antarctic marine ecosystem. However, the study of E. superba-derived microbes and their secondary metabolites has been limited. Chemical investigation of the secondary metabolites of the actinomycetes Nocardiopsis sp. LX-1 (in the family of Nocardiopsaceae), isolated from E. superba, combined with molecular networking, led to the identification of 16 compounds a–p (purple nodes in the molecular network) and the isolation of one new pyrroline, nocarpyrroline A (1), along with 11 known compounds 2–12. The structure of the new compound 1 was elucidated by extensive spectroscopic investigation. Compound 2 exhibited broad-spectrum antibacterial activities against A. hydrophila, D. chrysanthemi, C. terrigena, X. citri pv. malvacearum and antifungal activity against C. albicans in a conventional broth dilution assay. The positive control was ciprofloxacin with the MIC values of <0.024 µM, 0.39 µM, 0.39 µM, 0.39 µM, and 0.20 µM, respectively. Compound 1 and compounds 7, 10, and 11 displayed antifungal activities against F. fujikuroi and D. citri, respectively, in modified agar diffusion test. Prochloraz was used as positive control and showed the inhibition zone radius of 17 mm and 15 mm against F. fujikuroi and D. citri, respectively. All the annotated compounds a–p by molecular networking were first discovered from the genus Nocardiopsis. Nocarpyrroline A (1) features an unprecedented 4,5-dihydro-pyrrole-2-carbonitrile substructure, and it is the first pyrroline isolated from the genus Nocardiopsis. This study further demonstrated the guiding significance of molecular networking in the research of microbial secondary metabolites. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the quality changes and shelf life of ready-to-eat roasted Antarctic krill, either untreated (CT) or treated with sodium diacetate (SD) or sodium diacetate and a deoxidizer (SDD), during storage at room temperature (25°C) by using sensory, physiochemical, and microbial assessment. Additionally, fluoride accumulation in this food product was used to evaluate its safety. Analysis showed that the addition of SD and SDD resulted in better sensory scores compared of that of CT samples (P <0.05). Accordingly, microorganism growth and total basic nitrogen (TVB-N) were maintained at a low level for the duration of storage with SD and SDD treatments. The total viable counts of SD and SDD reached (4.58 ± 0.08) log (CFU g−1) and (4.20 ± 0.11) log (CFU g−1), respectively. The mold was found after 6 and 18 days for SD and SDD treatment, and the numbers reached 5.2 × 106 and 8.5 × 104 respectively at the end of shelf life. The TVB-N values from CT continuously increased during the whole storage. While TVB-N values from SD and SDD remained significantly less change (P <0.05) during the early 20 days of the storage, and the values reached (12.11 ± 0.07) mg (100 g)−1 and (10.88 ± 0.15) mg (100 g)−1 on day 33 and day 70, respectively. Importantly, SDD treatment effectively minimized the oxidation values and retained the color of ready-to-eat roasted Antarctic krill. Our results showed that the shelf life of ready-to-eat roasted Antarctic krill treated with SDD was extended by up to 52 days. Additionally, rats fed ready-to-eat roasted Antarctic krill showed accumulation of fluoride exclusively in the thighbone. The accumulation of fluoride residues in the thighbone showed concentration-dependent. The concentrations of fluoride residues in rats were (1760.03 ± 38.21), (2371.52 ± 42.15) mg kg−1 and (3615.44 ± 30.53) mg kg−1, which were less than sodium fluoride feeding group (4621.01 ± 28.67) mg kg−1. The results suggested that the SD and SDD treatments led to better quality and shelf life extension of ready-to-eat roasted Antarctic krill during storage at room temperature (25°C). Therefore, the ready-to-eat roasted Antarctic krill can be of great interest to the seafood industry. [ABSTRACT FROM AUTHOR]

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The present study is the attempt to combine oceanologic measurements and biochemical analysis, which is as possible to implement on board as in a laboratory with chosen certain statistics to reveal trophic conditions and the environment state in which Antarctic krill live in season in real time on site. The fatty acid constituents of total lipids in juvenile and mature Antarctic krill sampled from the Bransfield Strait (BS), the Antarctic Sound (AS), and waters at the eastern tip of the Antarctic Peninsula (AP) collected during the 87th cruise of the R/V Akademik Mstislav Keldysh in January–February 2022 were analyzed. The fatty acid (FA) profile in juvenile and mature Antarctic krill was studied by gas chromatography with a mass selective detector to identify the qualitative composition and a flame ionization detector to quantify the studied FAs. Using NMDS analysis (quantitative panel), great difference was found between krill from the BS compared to krill collected in the AS and the AP. The differences are reliable owing to the following 16 FAs, most of them trophic biomarkers of microphytoplankton, and suggest regional differences, mainly in abundance and ability of forage objects. CTD measurements discuss the abiotic factors (potential temperature, salinity, and chlorophyll “a”). Compensatory modifications of the composition of FA components in Antarctic krill inhabiting different water areas are a way of maintaining the species’ viability under certain and variable habitat conditions.

Antarctic krill (Euphausia superba) are a keystone species in the Southern Ocean and if their populations decline there could be detrimental impacts to many other species in the Antarctic ecosystem. In order to study krill, the National Oceanic and Atmospheric Administration (NOAA) regularly monitors the Antarctic ecosystem, including outfitting predators with cameras to record prey encounters during feeding events. NOAA also recently sponsored the development of an open-source underwater imagery analysis system called Video and Image Analytics for a Marine Environment (VIAME) in order to make automated methods to process mass amounts of underwater visual data accessible to analysts and non-computer scientists. The proposed work of this study will use the VIAME software to determine the volumetric densities of krill observed in a video recording during a chinstrap penguin foraging event from the 2018 field season. The methods developed by this study resulted in imaged volume based on the maximum resolvable range, counts of krill per volume, and subsequently densities of krill. These methods provide a basis for automatically processing and estimating densities of krill pursued and encountered by predators. Densities from the perspective of a predator have not been documented previously for the Antarctic ecosystem.