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Quantifying trophic relationships within and between species in terms of trophic position, ontogeny and trophic diversity provides information on community-level structure and function. Little attention has been focused on examining the trophic structure and temporal changes of communities in freshwater-marine coupled systems in the subarctic and associated impacts of anthropogenic activity on trophic interactions. Therefore, the objective of this study was to quantify the trophic position of mobile consumers (15 species in total) within the lower Churchill River area (Churchill, Manitoba, Canada), examine trophic position variation in relation to ontogeny, and measure the trophic diversity of a fish assemblage before (1993–1995) and after (2019–2020) the installation of the Churchill River weir in the late 1990s. We used stable isotopes (δ13C and δ15N) to quantify individual and group-level variation in trophic position of thirteen fish species and two seal species and also assessed six community-level metrics of a three fish species assemblage between time periods. Overall, species that mainly foraged on freshwater resources occupied lower trophic positions than species that mainly consumed marine resources. Trophic position increased with fish age only in cisco, fourhorn sculpin, Greenland cod and northern pike. A temporal shift from a trophically diverse to a more trophically redundant fish assemblage occurred between 1993–1995 and 2019–2020. As a result, these predator species now play similar trophic roles. Information on the long-term change in trophic structure of this sub-Arctic estuarine system may help with understanding how anthropogenic activity and climate change have influenced the trophic diversity of a fish assemblage inhabiting this system. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada conducts an annual multidisciplinary survey in the Estuary and northern Gulf of St. Lawrence. The objectives of this survey are varied; assess the biodiversity of species found near the bottom; estimate the abundance of groundfish and invertebrates; assess physical and biological (phytoplankton and zooplankton) oceanographic conditions; monitor the pelagic ecosystem; and collect samples for various research projects. In 2022, the survey was conducted between August 7 and September 15 on board the CCGS Teleost and the CCGS John Cabot. During this mission, 181 and 176 trawl tows were completed, respectively on the Teleost and the John Cabot. In addition, 92 vertical profiles of the water column were carried out in order to characterize the oceanographic conditions and 63 zooplankton samples were also collected. This report presents the results of catches of 194 tows. In total, 78 fish taxa and 208 invertebrate taxa were identified during the mission. Historical perspectives (catch rates, spatial distribution and length frequency) are presented for 25 taxa. These commercial fisheryindependent data will be used in several stock assessments including cod (Gadus morhua), redfish (Sebastes spp.), Greenland halibut (Reinhardtius hippoglossoides), Atlantic halibut (Hippoglossus hippoglossus), witch flounder (Glyptocephalus cynoglossus), and northern shrimp (Pandalus borealis). A preliminary analysis of water temperature data collected in 2022 shows that conditions have warmed at depths greater than 150 m, establishing new records since 1915 at 150 m, 200 m and 300 m. The August cold intermediate layer minimum temperature was only slightly cooler in 2022 than in 2021 when it attained the highest recorded values observed in contemporary CTD era. Surface water temperatures were above normal in July-August. [ABSTRACT FROM AUTHOR]

Mixed-stock fisheries pose a challenge for fisheries management recommendations and management, as mixed stocks can lead to unintentional over- or under-exploitation of stocks, with both short- and long-term biological and economic consequences. This study demonstrates practical application and implementation of year-round high-resolution genetic stock monitoring in management of mixed Atlantic cod (Gadus morhua) stocks in western Greenland. Using a panel of 96 high resolution gene-associated SNPs, we identified the stock of origin for four cod stocks in the two major inshore mixed-stock fisheries. Contribution of individual stocks was quantified to identify if fjord sections, times of year, and fish size, would allow a "clean fishery" with a minimal contribution of the depleted West Greenland Offshore (WGO) population. High level of mixing was identified with 50% of inshore catches originating from the inshore stock, 20% from the East Greenland/Iceland offshore stock, and 30% from the WGO stock. Although some spatiotemporal variation of stock proportions was identified, a practice allowing exclusively fishing a specific stock was not possible. Accordingly, we demonstrate the need to allocate catches at the biological stock level and show that application of high-resolution genetics is a reliable and necessary tool. [ABSTRACT FROM AUTHOR]

In order to obtain a fishery-independent index covering a significant portion of the Gulf of St. Lawrence (GSL, NAFO Divisions 4RST) capelin (Mallotus spp.) stock area, the stomach contents of Atlantic cod (Gadus morhua) and Greenland halibut (Reinhardtius hippoglossoides) collected during the summer nGSL multispecies survey were examined. Using a bioenergetics approach, it was estimated that annual capelin consumption by the two predators continued to be higher than the commercial landings recorded for the GSL. These results support those obtained from previously published ecosystem models. All length classes combined, the percentage of capelin in the mean stomach contents of Atlantic cod shows greater interannual variation compared to the stomach contents of Greenland halibut. The use of capelin by Greenland halibut more closely reflected changes in the average number of capelin caught per tow in the nGSL multispecies surveys in years for which fish stomachs were available. However, several sources of uncertainty were raised regarding the stomach content data used and some of the assumptions in the methodology, and the need to collect samples at other times of the year was pointed out. Since capelin is one of the major forage species in the GSL, considering the population patterns of its predators and assessing their consumption of capelin would be additional aspects of interest to include in the assessment of this species. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada conducts an annual multidisciplinary survey in the Estuary and northern Gulf of St. Lawrence. The objectives of this survey are varied; assess the biodiversity of species found near the bottom; estimate the abundance of groundfish and invertebrates; assess physical and biological (phytoplankton and zooplankton) oceanographic conditions; monitor the pelagic ecosystem; and collect samples for various research projects. In 2021, the survey was conducted between July 25 and August 26 on board the CCGS Teleost. The survey successfully carried out 149 trawl tows as well as 74 CTD water column casts, and 57 zooplankton samples. This report presents the results of the 149 tows. In total, 82 fish taxa and 214 invertebrate taxa were identified during the mission. Historical perspectives (catch rates, spatial distribution and length frequency) are presented for 25 taxa. These commercial fishery-independent data will be used in several stock assessments including cod (Gadus morhua), redfish (Sebastes spp.), Greenland halibut (Reinhardtius hippoglossoides), Atlantic halibut (Hippoglossus hippoglossus), witch flounder (Glyptocephalus cynoglossus) and northern shrimp (Pandalus borealis). A preliminary analysis of water temperature data collected in 2021 shows that conditions have warmed at 150 m and deeper, reaching new records since 1915 at 150, 200 and 300 m. The August cold intermediate layer (CIL) minimum temperature was much warmer in 2021 than in 2020, reaching the highest values of the modern CTD era. Surface waters temperatures were near normal in July-August. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada conducts an annual multidisciplinary survey in the Estuary and northern Gulf of St. Lawrence. The objectives of this survey are varied; assess the biodiversity of species found near the bottom; estimate the abundance of groundfish and invertebrates; assess physical and biological (phytoplankton and zooplankton) oceanographic conditions; monitor the pelagic ecosystem; and collect samples for various research projects. In 2020, the survey was conducted between August 12 and September 5 on board the CCGS Teleost. Due to the context of the Covid-19 pandemic, the number of days at sea and the number of scientists on board the ship had to be reduced. The survey successfully carried out 147 trawl tows as well as 66 CTD water column casts, and 34 zooplankton samples. This report presents the results of the 147 tows. In total, 78 fish taxa and 206 invertebrate taxa were identified during the mission. Historical perspectives (catch rates, spatial distribution and length frequency) are presented for 25 taxa. These commercial fishery-independent data will be used in several stock assessments including cod (Gadus morhua), redfish (Sebastes spp.), Greenland halibut (Reinhardtius hippoglossoides), Atlantic halibut (Hippoglossus hippoglossus), witch flounder (Glyptocephalus cynoglossus) and northern shrimp (Pandalus borealis). A preliminary analysis of water temperature data collected in 2020 shows that conditions have warmed at 150 m and deeper, reaching new records since 1915 at 200 and 300 m. The cold intermediate layer was warmer in 2020 than in 2019 except in the Estuary where it remained stable. Surface waters were also warmer than normal, by 1.5°C, in July-August. [ABSTRACT FROM AUTHOR]

Seasonal prey bursts are important for the life cycles and energy budgets of many predators. This study documents the diet and, especially, the importance of the ephemeral occurrence of capelin as prey for Atlantic cod (Gadus morhua) in Godthaabsfjord, west Greenland, over an annual cycle. The cod showed clear differences in diet composition on the 11 sampling dates resulting in a spring–summer, late summer–autumn and winter cluster. Moreover, a single sampling date, 12 May, was defined by cod gorge feeding on spawning capelin, which led to average stomach contents 4.3 times higher than the average for the remaining sampling dates. Changes in nitrogen stable isotope values from 22 April to 7 July in cod liver and muscle tissue were used to calculate the consumption of capelin. Based on this, the consumption of capelin varied between 538 and 658 g wet weight for a 1.3 kg cod. Using published consumption/biomass estimates and observed growth rates, the capelin intake corresponds to 10.1%–33.3% of the annual food consumption and accounts for 28.1%–34.5% of the annual growth of the cod. The present study documents the omnivorous feeding mode of Atlantic cod but highlights the utilization and importance of ephemeral prey bursts for the annual energy budget of the cod. It is hypothesized that access to capelin is critical for the postspawning recovery of Godthaabsfjord cod. [ABSTRACT FROM AUTHOR]

The status of the marine species caught in the Saguenay Fjord recreational fishery was assessed annually from 1995 to 2010 and every two years from 2012 to 2018. This assessment is based on various indicators from a monitoring program for the winter recreational fishery (also known as ice fishing) (1995-2018), a Fisheries and Oceans Canada (DFO) research survey (2000-2018) and a recent individual logbook initiative (2015-2018). This report presents the data and methods used to derive the indicators from the monitoring program for the winter recreational groundfish fishery in the Saguenay Fjord. Estimates of the number of fish per unit of effort (NUE) for more than 20 years of recreational fishery sampling (1996-2018) are presented for the following species: redfish (Sebastes spp.), Atlantic cod (Gadus morhua), Greenland cod (Gadus ogac) and Greenland halibut (Reinhardtius hippoglossoides). In addition, biological parameters of the sampled populations are indicated. Groundfish catches in the Saguenay winter recreational fishery are composed on average of 88% redfish, 10% cod (Atlantic and Greenland cod) and 2% Greenland halibut for the 1996-2018 time series. For the Saguenay as a whole, the redfish index of abundance decreased from 1996 to 2006 and remains low since with values clearly below those at the beginning of the series. Indices of abundance for Atlantic cod, Greenland cod, and Greenland halibut are at low level. However, since 2013 there has been an increase in NUE for the Atlantic cod and Greenland halibut with values above their respective series average. Studies published in the late 2000s (Sévigny et al. 2009, Sirois et al. 2009) suggest that groundfish populations in the Saguenay appear to be sink populations whose recruitment depends on the arrival of juveniles from the St. Lawrence Estuary (Bui et al. 2012). Although groundfish reproduction does occur in the Saguenay, larval survival of these species would be compromised by conditions in the warm, brackish surface water layer, preventing a significant local contribution to recruitment, particularly for redfish and cod (Sirois et al. 2009). Strong cohorts of redfish (Sebastes mentella) (2011, 2012 and 2013) were noted in the Estuary, and their abundance was at the highest level seen in the last 30 years (Bourdages et al. 2019). The presence of these new cohorts in the Saguenay Fjord has been observed since 2013, namely in the stomach contents of large redfish, during a major stranding at Saint-Fulgence in December 2014, in the smelt fishery and during research surveys (Gauthier et al. 2019). The recent high-abundance cohorts are beginning to recruit to the recreational fishery, but the fish are small in size. These redfish had a modal size of 16 cm in 2017 and of 20 cm in 2018 and made up nearly 10% of redfish catches. The medium-term outlook is encouraging for the winter recreational redfish fishery in the Saguenay Fjord. [ABSTRACT FROM AUTHOR]

Anisakid nematode larvae occur frequently in the liver of Atlantic cod, but merely few infection data from cod in waters around Greenland exist. The present study reports the occurrence of third-stage anisakid larvae in the livers of 200 Atlantic cod caught on fishing grounds along the West coast of Greenland (fjord systems of Maniitsoq) in May, June, August and September 2017. Classical and molecular helminthological techniques were used to identify the nematodes. A total of 200 cod livers were examined, and 194 were infected with third-stage nematode larvae (overall prevalence of infection 97%) with a mean intensity of 10.3 (range between 1 and 44 parasites per fish). Prevalences recorded were 96% for Anisakis simplex (s.l.), 55% for Pseudoterranova decipiens (s.l.) and 8% for Contracaecum osculatum (s.l.). Sequencing the mtDNA cox2 from 8 out of 23 these latter larvae conferred these to C. osculatum sp. B. A clear seasonal variation was observed, with a rise in A. simplex (s.l.) and P. decipiens (s.l.) occurrence in June and August and a decline in September. The study may serve as a baseline for future investigations using the three anisakids as biological indicators in Greenland waters. [ABSTRACT FROM AUTHOR]

Polar cod (Boreogadus saida) is the most abundant and ubiquitous fish species throughout the Arctic Ocean. As such, they serve an important ecosystem role linking upper and lower trophic levels and transferring energy between the benthic and pelagic realms. Our objective is to explore what limits the southern distribution of polar cod in Pacific and Atlantic sectors by examining time series of survey and oceanographic data. We quantify the variability in the southern extent of the polar cod distribution in the Bering and Labrador Seas, and determine mechanisms (bottom temperature and potential predators: Pacific cod Gadus macrocephalus, Atlantic cod Gadus morhua, and Greenland halibut Reinhardtius hippoglossoides and competitors: capelin Mallotus villosus and walleye pollock Gadus chalcogrammus) driving the variability. When temperatures were lower, polar cod occupied larger areas and had higher abundances in both regions, suggesting that as temperatures increase with climate warming the range of polar cod is likely to contract. Temperature had a much larger impact on polar cod abundance than competitor abundance and predator abundance, especially in the eastern Bering Sea. However, when we included data from northern and eastern Bering Sea in 2010 and 2017, polar cod were less likely to occur in warmer waters when either Pacific cod or walleye pollock were present. Northward range expansions of subarctic Pacific cod and walleye pollock may further restrict polar cod distributions. [ABSTRACT FROM AUTHOR]

The codfish family includes more than 500 species that vary greatly in their abundance in areas like the North Sea and are widely fished. Gadoids (codfish) gather at particular locations to spawn, where they exhibit complex reproductive behavior with visual and acoustic displays. Calls have been described from seven species, including the Atlantic cod and haddock. They vocalize by means of a specialized apparatus, consisting of rapidly contracting striated muscles (the drumming muscles) attached to the gas-filled swim bladder. Several gadoids, such as the ling and the Greenland cod, possess drumming muscles and are likely to make sounds. Non-vocal gadoids, such as the poor cod, lack these muscles. It is suggested that the sonic apparatus was present in the early species of the gadoids, with some species having lost their sonic ability. Interestingly, silent gadoids are mainly small schooling fishes. Gadoid species are most sensitive to sounds from 30 to 500 Hz. Gadoid hearing can be masked by ambient sound but also by anthropogenic sounds, which may therefore adversely affect their reproduction, with potential effects upon discrete local stocks. Listening for gadoid sounds provides a reliable, non-invasive way of locating spawning sites, which can enhance the protection of reproducing fish from human impacts. [ABSTRACT FROM AUTHOR]

The status of exploited marine species in the Saguenay Fjord is assessed every two years and is based on various indicators from the recreational winter fishery (1995-2018), a research survey conducted by Fisheries and Oceans Canada (2000-2018) and logbook (2015-2018) data. This document presents the data and methods used to derive indicators from the research survey. Estimates of the number of fish per gillnet (NUE) are presented for each of the four species primarily targeted by the winter groundfish recreational fishery in the Saguenay Fjord: Atlantic redfish (Sebastes mentella), Atlantic cod (Gadus morhua), Greenland cod (Gadus ogac), and Greenland halibut (Reinhardtius hippoglossoides) also called turbot. Biological data including size structures and condition indices are presented for the different species. Information on the diet of Greenland halibut is also presented. Oceanographic data collected during scientific surveys are provided for temperature, salinity and oxygen saturation at some stations in the study area. [ABSTRACT FROM AUTHOR]

A comparative analysis of the variability of morphobiological and genetic characteristics in samples from the largest stocks of Atlantic cod in waters of the Northeast and Northwest Atlantic was conducted. Using the results of pairwise assessment of genetic differentiation for the studied microsatellite loci, it was established that the dataset from waters of the New England shelf differed significantly from Iceland–Greenland and Lofoten–Barents Sea cod stocks. It was noted that samples of cod from the waters of East and West Greenland and cod from the waters of the Norwegian and Barents seas, despite significant geographical separation, showed a high level of identity. Special features of application of the model for isolation by distance to studying the formation mechanisms of the population structure were reviewed. [ABSTRACT FROM AUTHOR]

• Demersal trawl surveys at Yermak Plateau and northern Svalbard waters in the period 2012–2020 caught 69 fish taxons. • The fish community sampled by bottom trawl in weight and abundance was dominated by Atlantic cod and polar cod, respectively. • Three clusters of species were identified characterized by environmental factors. • The slope region north of Svalbard is a transition region between boreal and Arctic species which is likely to shift eastwards with further warming. • Arctic Mainly Arctic, and Arcto-boreal species were dominating at the Yermak Plateau, but Mainly Boreal species were also represented. During several surveys covering the north-western and northern Svalbard waters, and the deeper Yermak Plateau north of Svalbard during the period 2012–2020, 291 standardized hauls with a demersal trawl were made. All fishes in the catches were identified to the lowest possible taxonomic level, mostly to species. In addition to the data generated from the trawl catches, bottom temperature, salinity, and depth were recorded at each trawl station. The eelpouts were the most species rich family, with 15 species, followed by codfishes and sculpins with six species each. The other 13 families were represented with one to four species each. Atlantic cod (Gadus morhua) dominated by weight in the catches, while polar cod (Boreogadus saida) dominated by numbers. In the deeper areas including the Yermak Plateau, Greenland halibut (Reinhardtius hippoglossoides) dominated by weight. Zoogeographically, 23 species were Arctic, 5 were Mainly Arctic, 4 Arctoboreal, 25 Mainly Boreal, 9 Boreal, and 2 Widely Distributed. The Arctic species dominated in the deeper areas (Yermak Plateau and slope > 500 m) and on the shallow eastern shelf, whereas the Mainly Boreal species dominated along the slope and on the western and northern shelves < 500 m. A hierarchical cluster analysis revealed three prominent station clusters consistent with the zoogeographical classifications which reflected the oceanographic conditions, water masses and sea ice. The hierarchical cluster analysis additionally separated the cold-water species into two groups consistent with the bathymetry of the region. Diet studies of Atlantic cod revealed that it mainly fed on hyperiids, and that its preferred food further south, capelin, was not prominent in the diet. Regional index terms: Northeast Atlantic, Fram Strait, Svalbard, Yermak Plateau. [ABSTRACT FROM AUTHOR]

Traditional tagging techniques are simple and cost-effective, but inferences require recaptures and data on movement/migration are limited to a start and end position at unpredictable intervals. Pop-up satellite archival tags (PSATs) offer other opportunities, as they provide positions at pre-programmed times and collect on-route data, which can be used to describe position, behavior, and habitat preferences. Species suitability should, however, be documented prior to large-scale studies using PSATs. We deployed PSATs on six relatively large (total length 84–125 cm) Atlantic cod (Gadus morhua) in inshore West Greenland waters. Three tags were physically recovered, providing high-resolution data on depth and temperature (readings every 3 s), while three tags did not report (recovery rate = 50 %). To evaluate the tag's applicability on Atlantic cod, we made a detailed behavioral analysis by defining swimming behavior, occupied water types and depth phases, which were cross-evaluated in relation to depth, temperature and water stratification to identify behavioral patterns. Distinct and shared patterns in swimming behavior were evident and we found no signs of impaired swimming behavior except for an adaptation period lasting up to 39 h after release. Generally, the three cod were pelagic and preferred waters ranging 2–5 °C. When encountering colder water masses these were avoided. During late summer/early autumn, increased vertical activity could in some cases be linked to darkness and a high-activity event could be linked to possible predator avoidance. All combined, we conclude that PSATs are suitable to monitor natural behavior on large specimens of Atlantic cod for periods of at least four months. [ABSTRACT FROM AUTHOR]

In this study, we propose a computer vision-based few-shot learning method for otolith age determination in European plaice, Atlantic cod, Greenland halibut, and haddock. Our method outperforms prior state-of-the-art approaches, and is based on a vision encoder from CLIP as a feature extractor, which is used to train shallow models. The method is computationally efficient, as it does not require fine-tuning of deep networks, and is also data efficient, as it performs better than fine-tuning on the same data. Our results suggest that in some cases, our method can achieve the same performance as state-of-the-art finetuning approaches with up to three times less training data. • Proposing a few-shot learning method for otolith age determination. • The method outperforms prior state-of-the-art approaches for automatic otolith age determination. • The method is computationally efficient since it requires no fine-tuning of deep networks. • The method can reach the same performance as fine-tuning approaches with up to three times less training data. • The method is general and can easily be transferred to otoliths of other fish species. [ABSTRACT FROM AUTHOR]

In this study, we investigate the type and quantity of selenium compounds in fish and marine organisms, using ion-pair reversed phase LC–ICP-MS, developed and applied for the analysis of Atlantic cod, Atlantic salmon, Greenland halibut, Atlantic herring, blue mussel, common crab, scallop, calanus, and Euphasia super . Of the samples examined, the lowest level of selenium was found in farmed Atlantic salmon (0.17 mg Se kg −1 dm). The total selenium extraction efficiency by phosphate buffer was 2.5 times higher in sea plankton and shellfish samples than in fish samples. Analysis of Se species in each hydrolysate obtained by proteolysis showed the presence of selenomethionine, which constituted 41.5% of the selenium compounds detected in hydrolysates of Atlantic herring and 98.4% of those in extracts of Atlantic salmon. Inorganic compounds, such as selenates and selenites, were detected mainly in sea plankton and shellfish samples (<0.13 mg Se kg −1 wm), although no correlation was found between the presence of inorganic compounds and total selenium concentration. The accuracy of the total selenium determination was validated using a certified reference material (oyster tissue (NIST 1566b)). A lyophilised powder of cod ( Gadus morhua ) was used to validate speciation analysis, enzymatic hydrolysis of lyophilised powder of cod recovered 54 ± 6% of total selenium, and SeMet constituted 83.5 ± 5.28% of selenium detected in hydrolysates. The chromatographic detection limits were, respectively, 0.30 ng mL −1 , 0.43 ng mL −1 , 0.54 ng mL −1 , 0.55 ng mL −1 , 0.57 ng mL −1 and 0.72 ng mL −1 for selenate, selenomethionine, selenite, Se-methyl-selenocysteine, selenocystine and selenomethionine selenoxide. The data on selenium concentrations and speciation presented here could be useful in estimating levels of selenium intake by seafood consumption. [ABSTRACT FROM AUTHOR]

[Display omitted] • Protein biomarkers can be applied for cod species authentication. • An accurate fish species identification platform is established using SWATH-MS. • Ten biomarkers are discovered for cod species authentication. • Fish species of processed products can be distinguished by using the 10 biomarkers. Seafood substitutions is a global problem and come under the spotlight in recent years. In Taiwan, Greenland halibut is usually substituted for the cod because of its lower price. Nowadays, DNA technology is widely used for fish species identifications; however, it still has concern about the DNA of processed fishery products might be destroyed. This study was designed to develop a proteomic-based method for fish and fishery product authentication by using ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) with Sequential window acquisition of all theoretical fragment ion spectra (SWATH). The protein biomarkers from the meat of Alaska pollock, Atlantic cod, and Greenland halibut were identified and validated for species authentication of cod and corresponding fishery products, which might prevent consumer substitutions and fish product mislabeling. Besides, the E. coli proteins can be measured from existing SWATH-MS data though retrospective analysis successfully, it might present the quality of fish meat. [ABSTRACT FROM AUTHOR]

The spawning stock of Atlantic cod Gadus morhua in West Greenland waters was characterized by a drastic decline in the late 1960s and has since exhibited considerable variation. It has been suggested that the cod stock in West Greenland waters is composed of several stock components that include (1) a number of distinct local inshore populations spawning in separate fjord systems, (2) an offshore spawning component located on the fishing banks, and (3) a periodic Icelandic-East Greenland cod influx that mixes with the offshore and inshore West Greenland stock components. In an attempt to clarify the status of Atlantic cod in Greenland waters, we investigated the genetic structure at different inshore and offshore feeding grounds east and west of Greenland. A total of 1,581 genetic samples were collected within North Atlantic Fisheries Organization areas at inshore and offshore locations as well as within the International Council for the Exploration of the Sea area XIVb. Those samples were genotyped for 18 microsatellite loci and the pantophysin (Pan I) locus. Both types of genetic markers gave congruent results and suggest the presence of two distinct genetic components with limited connectivity in Greenland waters, namely, an inshore component and an offshore component. [ABSTRACT FROM AUTHOR]

Abstract: Concern about future anthropogenic warming has lead to demands for information on what might happen to fish and fisheries under various climate-change scenarios. One suggestion has been to use past events as a proxy for what will happen in the future. In this paper a comparison between the responses of Atlantic cod (Gadus morhua) to two major warm periods in the North Atlantic during the 20th century is carried out to determine how reliable the past might be as a predictor of the future. The first warm period began during the 1920s, remained relatively warm through the 1960s, and was limited primarily to the northern regions (>60°N). The second warm period, which again covered the northern regions but also extended farther south (30°N), began in the 1990s and has continued into the present century. During the earlier warm period, the most northern of the cod stocks (West Greenland, Icelandic, and Northeast Arctic cod in the Barents Sea) increased in abundance, individual growth was high, recruitment was strong, and their distribution spread northward. Available plankton data suggest that these cod responses were driven by bottom-up processes. Fishing pressure increased during this period of high cod abundance and the northern cod stocks began to decline, as early as the 1950s in the Barents Sea but during the 1960s elsewhere. Individual growth declined as temperatures cooled and the cod distributions retracted southward. During the warming in the 1990s, the spawning stock biomass of cod in the Barents Sea again increased, recruitment rose, and the stock spread northward, but the individual growth did not improve significantly. Cod off West Greenland also have shown signs of improving recruitment and increasing biomass, albeit they are still very low in comparison to the earlier warming period. The abundance of Icelandic cod, on the other hand, has remained low through the recent warm period and spawning stock biomass and total biomass are at levels near the lowest on record. The different responses of cod to the two warm events, in particular the reduced cod production during the recent warm period, are attributed to the effects of intense fishing pressure and possibly related ecosystem changes. The implications of the results of the comparisons on the development of cod scenarios under future climate change are addressed. [Copyright &y& Elsevier]

Growth variation was estimated from mean lengths-at-ages 4 and 5 for Atlantic cod off Greenland based on 52,973 fish taken from commercial and scientific catches from 1955 to 2002. Mean length-at-age values were corrected for area and seasonal effects, and significant growth reductions occurred during the 1960s and from the mid-1970s until the mid-1980s. Annual growth rates of cod in Greenland waters during the most recent decade (1993–2002) were consistently among the highest recorded. Statistical growth models accounting for temperature, fishing mortality, and stock abundance effects were constructed. Multiple linear regressions revealed significant positive temperature effects on growth of both age groups and a significant negative stock density effect on length-at-age 4. Correlations between exploitation intensity and length-at-age were statistically insignificant. During the period 1955–2002, the number of recruits at age 3 was significantly correlated with the Greenland cod spawning-stock biomass, June water temperature on top of Fyllas Bank (West Greenland), and Iceland cod recruitment. All factors had a positive effect on the number of Greenland recruits and, combined, accounted for 60% of the observed variation. Spawning stock size was, by far, the most important factor contributing to recruitment variability, while June water temperature below 1°C and Iceland recruits below 150 million never coincided with high year-class strength in Greenland during the past 50 years. Thus, previous conclusions regarding a close relation between the Greenland and Icelandic cod stocks might need to be reconsidered in the light of a continued recruitment failure in Greenland waters over the two most recent decades, despite the improved environmental conditions and near-average recruitment of the Icelandic stock. The low precision of the recruitment model, however, prevents reliable predictions in the short or medium term, but a substantial short-term recovery of the Greenland cod stock remains unlikely. [Copyright &y& Elsevier]

Escape performance was examined in three similarly sized teleosts caught in Arctic waters: the Atlantic cod,Gadus morhua, the Greenland cod,Gadus ogac, and the short-horned sculpin,Myoxocephalus scorpius. Escape responses were elicited by a mechanical stimulus and followed by recordings of velocity and acceleration over the first 320 ms. A significant difference in escape performance was confirmed between the three species.G. morhuaalways exhibited the fastest andM. scorpiusthe slowest responses. Maximal measures of acceleration and velocity revealed no difference betweenG. morhua(12.6 m s-2 and 1.27 m s-1) andG. ogac(11.9 m s-2 and 1.16 m s-1) but an overall reduced performance inM. scorpius(6.5 m s-2 and 0.71 m s-1). The escape performance of the gadid and cottid species generally correlate well with their behavioural lifestyle, but it is surprisingly similar to Antarctic notothenioid fishes at lower temperatures. [ABSTRACT FROM AUTHOR]

The interrelated effects of body size and choroidretedevelopment on the ocular partial pressure of oxygen (PO2) of the mainly temperate Atlantic cod,Gadus morhua, and the exclusively polar Greenland cod,G. ogac, were investigated using micro-optode O2 sensors. Due to a difference in geographical distribution, it is hypothesized thatG. ogacwill possess features favouring visual-metabolic processes in a cold, dark environment. The relative size of the eye was identical between species and exhibited negative body-size scaling. The oxygen-secretingretiaof both gadid species are extremely well developed and, although variable, recordings of ocular PO2 were consistently and often greatly in excess of atmospheric pressures (27.7-138.3 kPa). The choroidretewas slightly more developed inG. ogac, but ocular PO2 was not significantly different between the two species. Choroidretedevelopment scaled isometrically with body size in both species and may explain why differences in body size did not account for any of the variation in ocular PO2 measures. The hypothesis that polar-fish species exhibit marked visual-metabolic adaptations as a result of their cold, dark environment is not wholly supported by the current data. [ABSTRACT FROM AUTHOR]

Body condition and energy reserves are important indicators of organism health, habitat suitability and predictors for the reproductive success in fish. In Greenland waters, Atlantic cod (Gadus morhua) inhabits different habitats in shallow and deep parts on top of the shelf and along slopes, where diet composition differs. We investigated the influence of habitat heterogeneity and trophic niche on body condition using organosomatic indicators, e.g. the morphometric index K, hepatosomatic and gonadosomatic indices, and biochemical indicators, e.g. lipid content and fatty acid compositions, of mature female cod. Body condition differed between sites and peaked in north-eastern regions in depths below 300 m towards the slope of the northern Irminger Sea. Trophic niches as indicated by stable isotope values and stomach composition data varied between sites, which was likely related to depth and differences between benthic and pelagic feeding regimes. Total lipid content and fatty acid profiles important for reproduction were associated with a pelagic diet comprised of mesopelagic fish and crustaceans. Interestingly, consumption of capelin was not linked to highest energy reserves as indicated by traditional body condition indices, such as K and the hepatosomatic index, but lowest ratios of eicosapentaenoic acid to arachidonic acid in gonads, which are known to be beneficial for high egg production. This shows that body condition on biochemical level can differ from conventionally used indices, which emphasizes the need to take fatty acid composition into account, when investigating condition and reproductive potential in cod. Our results emphasize that the factor habitat cannot be ignored for population replenishment of the cod stocks in Greenland waters and indicate that capelin as part of an Arcto-boreal diet benefits reproductive success in cod. [ABSTRACT FROM AUTHOR]

The annual global catch of Atlantic cod (Gadus morhua L.) is above 1,000,000 tons, and a large proportion is preserved and sold as frozen products. In Greenland, a new innovative fishing method centred on capture-based aquaculture has been developed. To compare the new fishing and processing method with the conventional method, the texture, colour, water holding capacity, salt soluble proteins and sensory properties of fillets were evaluated during 12 months of frozen storage. High quality life (HQL) and practical storage life (PSL) were determined for each fishing and processing method based on sensory evaluation, and by using water holding capacity and the salt soluble protein fraction as indices of quality. Capture-based aquaculture fishing and related processing increased frozen storage durability regarding texture attributes, blood content and sensory properties compared to the conventional method. Lowering the storage temperature to −40 °C increase the HQL to >12 months compared to a HQL of 4–6 months at −20 °C. • Capture-based aquaculture (CBA) production of cod improves fillet texture. • Blood content in cod fillets was reduced by changing to CBA production. • Indices of spoilage for high quality frozen sensory shelf-life was suggested. [ABSTRACT FROM AUTHOR]

Frozen Atlantic cod can have a long shelf-life, but some markets demand convenience products and thawed and chilled (refreshed) fish may fulfil this demand. Sensory, chemical and microbiological changes for refreshed cod from Greenland were studied to determine shelf-life and potential indices of spoilage. Aerobic sensory shelf-life was 13 days at 2.9 °C and 19 days at 0.4 °C, with modified atmosphere packaging (MAP: 40% CO 2 and 60% N 2) extending shelf-life to >32 days. Low drip loss during chilled storage of 2.3–2.5% for refreshed cod in air and 3.4–3.6% in MAP suggested the studied fish material was suitable for a combination of frozen and chilled distribution. Pseudomonas spp. and Psychrobacter spp. dominated the spoilage microbiota of chilled cod in air, while Carnobacterium maltaromaticum and Rahnella aquatilis dominated the microbiota of chilled MAP cod. A specific spoilage organism, that limited sensory shelf-life and caused the observed chemical product changes, including the formation of total volatile basic nitrogen (TVBN), was not identified. • Shelf-life of refresh MAP Atlantic cod was more than 32 days. • Spoilage of refresh cod correlates with the formation of TVN. • Low drip loss, 3.4–0.3.6%, during storage of refresh cod in MAP. • Pseudomonas and Psycrobacter dominated the microbiota of refresh cod in air. [ABSTRACT FROM AUTHOR]

Sensory, chemical and microbial changes for Atlantic cod (Gadus morhua L.) filets from capture-based-aquaculture in Greenland were studied. The objective was to determine shelf-life and indices of spoilage for iced or superchilled fillets when stored in air, or modified atmosphere packed (MAP; 40% CO 2 and 60% N 2). MAP iced storage extended the sensory shelf-life from 15 days to 21 days compared to storage in air. With superchilling at −1.7 °C sensory shelf-life was above 32 days, and no formation of total volatile nitrogen (TVN) was observed irrespective of storage in air or MAP. pH of ≥7.0, TVN (≥35 mg-N/100 g) and trimethylamine (≥20 mg-N TMA/100 g) were promising indices of spoilage. Aerobic viable counts were less valuable indices of spoilage as the dominating microbiota of cod in air (Pseudomonas spp., Photobacterium spp., Shewanella spp., Acinetobacter spp.) changed to Photobacterium spp. in MAP cod. Spoilage activity determined as the yield factor for TVN formation was 6–200 folds higher for Photobacterium spp. compared to Shewanella spp. and Pseudomonas spp. Photobacterium carnosum was responsible for TVN formation in iced cod irrespective of storage in air or MAP, and it was identified at the specific spoilage organism that limited iced product shelf-life. • Shelf-life of superchilled Atlantic cod was more than 32 days. • Superchilling in combination with MAP limited microbial growth. • Photobacterium carnosum was the SSO responsible for spoilage of iced cod. • TVN, TMA and pH were promising indices of spoilage for Atlantic cod. [ABSTRACT FROM AUTHOR]

Simple Summary: As high-value fishery products, cod species are frequently faked by non-cod ones. Genetic fingerprinting is important for both certifying authenticity and traceability of fish species. In this study, we developed a method that combines DNA barcoding and restriction-site associated DNA sequencing (RAD-Seq) approach for the identification of cod products. Two sequences that contain single nucleotide polymorphism (SNP)s were identified and these SNPs can be used to distinguish three different cod species, which are Atlantic cod (Gadus morhua), Greenland turbot (Reinhardtius hippoglossoides), and Patagonian toothfish (Dissostichus eleginoides). This SNP-based method will help us to identify the products, which are sold under the name of "Xue Yu" (Cod) in China, and works in parallel with existing fish identification techniques to establish an efficient framework to detect and prevent fraud at all points of the cod commercialization. The increase in the rate of seafood fraud, particularly in the expensive fishes, forces us to verify the identity of marine products. Meanwhile, the definition of cod lacks consistency at the international level, as few standards and effective application methods are capable of accurately detecting cod species. Genetic fingerprinting is important for both certifying authenticity and traceability of fish species. In this study, we developed a method that combines DNA barcoding and the restriction-site associated DNA sequencing (RAD-Seq) approach for the identification of cod products. We first obtained 6941 high-quality single nucleotide polymorphism (SNP)s from 65.6 gigabases (Gb) of RAD-Seq raw data, and two sequences that contain SNPs were finally used to successfully identify three different cod product species, which are Atlantic cod (Gadus morhua), Greenland turbot (Reinhardtius hippoglossoides), and Patagonian toothfish (Dissostichus eleginoides). This SNP-based method will help us to identify the products, which are sold under the name of "Xue Yu" (Cod) in China, and works in parallel with existing fish identification techniques to establish an efficient framework to detect and prevent fraud at all points of the seafood supply chain. [ABSTRACT FROM AUTHOR]

• An in situ REIMS method was developed for discriminating cod from oilfish. • A statistical model was built and the most influencial markers were found. • The fish tissue can be authenticated real-time with accuracy 96–100%. • The samples were analyzed directly without any preparation process. Oilfish is banned in some countries because of the unpleasant side-effects of eating oilfish. However, oilfish was easily mislabeled and sold as cod due to their closed appearance. In this study, an in situ and real-time method was developed to distinguish cod from oilfish by coupling intelligent surgical knife (iKnife) and rapid evaporative ionization mass spectrometry (REIMS). The fillets collected from the same position of adult fishes were analyzed directly without sample preparation. The iKnife-REIMS conditions were optimized as cutting speed ca. 5 mm·s−1 and stripe length 2 cm, power output 30 W, and flow rate of auxiliary solvent (propan-2-ol) 100 μL·min–1. 200 spectral data from oilfish and cod was acquired in negative ionization mode and the data was processed by background subtraction, peak detection, and absolute counts calculation, which were further statistically analyzed by multivariate statistical analyses, including principal component analysis (PCA) and orthogonal partial least-square analysis (OPLS-DA). The major contributors of cluster separation were verified by permutation test and receiver operating characteristic (ROC) analysis. The identities of oilfish and cod (Greenland cod, Pacific cod, and Atlantic cod) were successfully recognized with accuracy 96–100%. This study filled the application niche of REIMS in cod authenticity and paved the way for the administration of food security and quality for related functional departments and bureaus. [ABSTRACT FROM AUTHOR]

Seasonal prey bursts are important for the life cycles and energy budgets of many predators. This study documents the diet and, especially, the importance of the ephemeral occurrence of capelin as prey for Atlantic cod (Gadus morhua) in Godthaabsfjord, west Greenland, over an annual cycle. The cod showed clear differences in diet composition on the 11 sampling dates resulting in a spring-summer, late summer-autumn and winter cluster. Moreover, a single sampling date, 12 May, was defined by cod gorge feeding on spawning capelin, which led to average stomach contents 4.3 times higher than the average for the remaining sampling dates. Changes in nitrogen stable isotope values from 22 April to 7 July in cod liver and muscle tissue were used to calculate the consumption of capelin. Based on this, the consumption of capelin varied between 538 and 658 g wet weight for a 1.3 kg cod. Using published consumption/biomass estimates and observed growth rates, the capelin intake corresponds to 10.1%-33.3% of the annual food consumption and accounts for 28.1%-34.5% of the annual growth of the cod. The present study documents the omnivorous feeding mode of Atlantic cod but highlights the utilization and importance of ephemeral prey bursts for the annual energy budget of the cod. It is hypothesized that access to capelin is critical for the postspawning recovery of Godthaabsfjord cod., (© 2020 Fisheries Society of the British Isles.)