Showing papers on "Atlantic cod published in 2020"
TL;DR: Assessment of metabolic activity of human fibroblast cells cultured in the presence of collagen extracts with concentrations up to 3 mg/mL revealed the absence of cytotoxic behavior, and collagen extracts obtained from Atlantic cod swim bladders shown attractive properties regarding their use in cosmetic or biomedical applications.
Abstract: Atlantic cod is processed industrially for food purposes, with several by-products being directed to animal feed and other ends. Looking particularly into swim bladders, the extraction of c...
49 citations
TL;DR: Five decades of stomach content data allowed insight into the development of consumption, diet composition, and resulting somatic growth of Gadus morhua (Atlantic cod) in the eastern Baltic Sea.
Abstract: Five decades of stomach content data allowed insight into the development of consumption, diet composition, and resulting somatic growth of Gadus morhua (Atlantic cod) in the eastern Baltic Sea. We ...
49 citations
TL;DR: Combined proteomics and lipidomics analyses indicate that PFAS may disrupt lipid homeostasis in Atlantic cod.
31 citations
TL;DR: Temperature had a much larger impact on polar cod abundance than competitor abundance and predator abundance, especially in the eastern Bering Sea, and Northward range expansions of subarctic Pacific cod and walleye pollock may further restrict polar cod distributions.
Abstract: 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.
26 citations
TL;DR: In this paper, a generalized linear modeling approach was used to investigate spatiotemporal trends of cod vocalizing over 10 consecutive winter spawning seasons (2007−2016), the longest time series of any passive acoustic monitoring of fish species.
Abstract: Atlantic cod Gadus morhua populations in the northeast USA have failed to recover sincemajordeclines in the1970sand1990s.Torebuild thesestocks,managersneedreliable information on spawning dynamics in order to design and implement control measures; discovering costeffective and non-invasive monitoring techniques is also favorable. Atlantic cod form dense, sitefidelic spawning aggregations during which they vocalize, permitting acoustic detection of their presence at such times. The objective of this study was to detect spawning activity of Atlantic cod using multiple fixed-station passive acoustic recorders to sample across Massachusetts Bay during the winter spawning period. A generalized linear modeling approach was used to investigate spatiotemporal trends of cod vocalizing over 10 consecutive winter spawning seasons (2007−2016), the longestsuchtimelineofanypassiveacousticmonitoringofafishspecies.ThevocalactivityofAtlantic cod was associated with diel, lunar, and seasonal cycles, with a higher probability of occurrence at night,duringthefullmoon,andnear theendofNovember.Following2009and2010, therewasageneraldeclineinacousticactivity.Furthermore, thenorthwestcornerofStellwagenBankwasidentified as an important spawning location. This project demonstrated the utility of passive acoustic monitoring in determining the presence of an acoustically active fish species, and provides valuable data for informing the management of this commercially, culturally, and ecologically important species.
21 citations
TL;DR: Large differences in spatial patterns of genetic differentiation across the genome are revealed and a complex biological structure within NCC and NCS is revealed, possibly yielding support to the earlier notion of subspecies rank.
Abstract: Challenging long-held perceptions of fish management units can help to protect vulnerable stocks. When a fishery consisting of multiple genetic stocks is managed as a single unit, overexploitation and depletion of minor genetic units can occur. Atlantic cod (Gadus morhua) is an economically and ecologically important marine species across the North Atlantic. The application of new genomic resources, including SNP arrays, allows us to detect and explore novel structure within specific cod management units. In Norwegian waters, coastal cod (i.e. those not undertaking extensive migrations) are divided into two arbitrary management units defined by ICES: one between 62° and 70°N (Norwegian coastal cod; NCC) and one between 58° and 62°N (Norwegian coastal south; NCS). Together, these capture a fishery area of >25,000 km2 containing many spawning grounds. To assess whether these geographic units correctly represent genetic stocks, we analysed spawning cod of NCC and NCS for more than 8,000 SNPs along with samples of Russian White Sea cod, north-east Arctic cod (NEAC: the largest Atlantic stock), and outgroup samples representing the Irish and Faroe Sea's. Our analyses revealed large differences in spatial patterns of genetic differentiation across the genome and revealed a complex biological structure within NCC and NCS. Haplotype maps from four chromosome sets show regional specific SNP indicating a complex genetic structure. The current management plan dividing the coastal cod into only two management units does not accurately reflect the genetic units and needs to be revised. Coastal cod in Norway, while highly heterogenous, is also genetically distinct from neighbouring stocks in the north (NEAC), west (Faroe Island) and the south. The White Sea cod are highly divergent from other cod, possibly yielding support to the earlier notion of subspecies rank.
20 citations
TL;DR: In this paper, the authors used metagenomic shotgun sequencing of individual specimens to compare the levels of intra-and interspecific variation of intestinal microbiome communities in two ecotypes (NEAC and NCC) of Atlantic cod (Gadus morhua) that have distinct behavior and habitats and three Gadidae species that occupy a range of ecological niches.
Abstract: The relative importance of host-specific selection or environmental factors in determining the composition of the intestinal microbiome in wild vertebrates remains poorly understood. Here, we used metagenomic shotgun sequencing of individual specimens to compare the levels of intra- and interspecific variation of intestinal microbiome communities in two ecotypes (NEAC and NCC) of Atlantic cod (Gadus morhua) that have distinct behavior and habitats and three Gadidae species that occupy a range of ecological niches. Interestingly, we found significantly diverged microbiomes among the two Atlantic cod ecotypes. Interspecific patterns of variation are more variable, with significantly diverged communities for most species' comparisons, apart from the comparison between coastal cod (NCC) and Norway pout (Trisopterus esmarkii), whose community compositions are not significantly diverged. The absence of consistent species-specific microbiomes suggests that external environmental factors, such as temperature, diet, or a combination thereof, comprise major drivers of the intestinal community composition of codfishes.IMPORTANCE The composition of the intestinal microbial community associated with teleost fish is influenced by a diversity of factors, ranging from internal factors (such as host-specific selection) to external factors (such as niche occupation). These factors are often difficult to separate, as differences in niche occupation (e.g., diet, temperature, or salinity) may correlate with distinct evolutionary trajectories. Here, we investigate four gadoid species with contrasting levels of evolutionary separation and niche occupation. Using metagenomic shotgun sequencing, we observed distinct microbiomes among two Atlantic cod (Gadus morhua) ecotypes (NEAC and NCC) with distinct behavior and habitats. In contrast, interspecific patterns of variation were more variable. For instance, we did not observe interspecific differentiation between the microbiomes of coastal cod (NCC) and Norway pout (Trisopterus esmarkii), whose lineages underwent evolutionary separation over 20 million years ago. The observed pattern of microbiome variation in these gadoid species is therefore most parsimoniously explained by differences in niche occupation.
19 citations
TL;DR: The gadMor_Celtic assembly provides a resource representing a ‘southern’ cod population which is complementary to the existing ‘northern’ population based genome assemblies and represents the first step toward developing pan-genomic resources for Atlantic cod.
Abstract: Currently available genome assemblies for Atlantic cod (Gadus morhua) have been constructed from fish belonging to the Northeast Arctic Cod (NEAC) population; a migratory population feeding in the Barents Sea. These assemblies have been crucial for the development of genetic markers which have been used to study population differentiation and adaptive evolution in Atlantic cod, pinpointing four discrete islands of genomic divergence located on linkage groups 1, 2, 7 and 12. In this paper, we present a high-quality reference genome from a male Atlantic cod representing a southern population inhabiting the Celtic sea. The genome assembly (gadMor_Celtic) was produced from long-read nanopore data and has a combined contig length of 686 Mb with an N50 of 10 Mb. Integrating contigs with genetic linkage mapping information enabled us to construct 23 chromosome sequences which mapped with high confidence to the latest NEAC population assembly (gadMor3) and allowed us to characterize, to an extent not previously reported large chromosomal inversions on linkage groups 1, 2, 7 and 12. In most cases, inversion breakpoints could be located within single nanopore contigs. Our results suggest the presence of inversions in Celtic cod on linkage groups 6, 11 and 21, although these remain to be confirmed. Further, we identified a specific repetitive element that is relatively enriched at predicted centromeric regions. Our gadMor_Celtic assembly provides a resource representing a 9southern9 cod population which is complementary to the existing 9northern9 population based genome assemblies and represents the first step towards developing pan-genomic resources for Atlantic cod.
19 citations
TL;DR: In this paper, a multi-model approach was applied to predict recruitment of 20 Atlantic cod (Gadus morhua) stocks as a function of adult biomass and environmental variables, and the performance of each model is contingent on the historical dynamics of individual stocks, and that stocks which experienced abrupt and state-dependent dynamics are best modelled using non-parametric approaches.
Abstract:
The stock–recruitment relationship is the basis of any stock prediction and thus fundamental for fishery management. Traditional parametric stock–recruitment models often poorly fit empirical data, nevertheless they are still the rule in fish stock assessment procedures. We here apply a multi-model approach to predict recruitment of 20 Atlantic cod (Gadus morhua) stocks as a function of adult biomass and environmental variables. We compare the traditional Ricker model with two non-parametric approaches: (i) the stochastic cusp model from catastrophe theory and (ii) multivariate simplex projections, based on attractor state-space reconstruction. We show that the performance of each model is contingent on the historical dynamics of individual stocks, and that stocks which experienced abrupt and state-dependent dynamics are best modelled using non-parametric approaches. These dynamics are pervasive in Western stocks highlighting a geographical distinction between cod stocks, which have implications for their recovery potential. Furthermore, the addition of environmental variables always improved the models’ predictive power indicating that they should be considered in stock assessment and management routines. Using our multi-model approach, we demonstrate that we should be more flexible when modelling recruitment and tailor our approaches to the dynamical properties of each individual stock.
19 citations
TL;DR: The findings demonstrate the frequency of plastic ingestion in this region is low, but fishing-gear related plastics represent a key source of marine plastics in the region that should be addressed.
19 citations
TL;DR: In this article, the authors investigated if an underlying mechanism of the observed productivity is related to reduced metabolic rates (proxy for energy use) of fish in reef habitats, using juvenile Atlantic cod Gadus morhua, tested the hypothesis that fish energy use differs between fish occupying stone reef and sand bottom habitats.
Abstract: Reefs are structurally complex habitats that are degraded in numerous coastal areas. Structural complexity is often associated with elevated fish abundance, and recent studies have indicated that such structural complexity (e.g. reefs) not only acts as a fish aggregator, but also increases fish production. The objective of this study was to advance this knowledge by investigating if an underlying mechanism of the observed productivity is related to reduced metabolic rates (proxy for energy use) of fish in reef habitats. Using juvenile Atlantic cod Gadus morhua, we tested the hypothesis that fish energy use differs between fish occupying stone reef and sand bottom habitats. Metabolic rate (MO2) was estimated using intermittent flow respirometry in simulated stone reef and sand bottom habitats over 24 h. Results revealed that G. morhua in the stone reef habitat exhibited significantly reduced accumulated MO2 compared to G. morhua in the sand bottom habitat. Likewise, there was a tendency for lower mean standard metabolic rates of the fish in stone reefs, although this pattern was not statistically significant. There are many mechanisms that may underpin elevated productivity in structurally complex habitats such as reefs, including better access to shelter and increased food availability. Our study adds to these mechanisms by showing that G. morhua save energy when occupying stone reefs as compared to sandy bottoms, energy which may be allocated to somatic and gonadal growth.
TL;DR: Despite major changes in the last decade in the fish and zooplankton community in western Svalbard, and consumption of a few Atlantic prey types, the ringed seals’ diet in SValbard continues to be dominated by Arctic prey, especially polar cod.
Abstract: Global warming is causing Atlantification of water masses and concomitant changes in food webs in the Barents Sea region. To determine whether changes that have been documented at lower trophic levels are impacting the diet of ringed seals (Pusa hispida) gastrointestinal tracts (GITs) from 99 coastal-feeding ringed seals, collected in western Spitsbergen, Svalbard, were analysed via identification of hard-parts. The study animals were shot in spring (n = 30; April–July) or autumn (n = 69; August–October) during four consecutive years (2014–2017). Thirty different prey types were identified, but most seals (55.6%) had consumed between 2 and 4 different types of prey. Polar cod (Boreogadus saida) dominated the diet of the ringed seals in terms of relative biomass (Bi = 60.0%) and frequency of occurrence (FOi = 86.9%), followed by pricklebacks (Stichaeidae; Bi = 23.4%; FOi = 79.8%). Redundancy analysis (RDA) revealed that year was the only significant predictor explaining variance in autumn diet composition (RDA, F3 = 4.96, AIC = − 76.49, p ≤ 0.0050; blubber content and maturity/sex group were not significant). Blue whiting (Micromesistius poutassou) occurred in the diet in small quantities; this Atlantic fish species has not previously been documented in the ringed seals’ diet. Atlantic cod (Gadus morhua) had the highest Bi (9.2%) among Atlantic prey types. However, despite major changes in the last decade in the fish and zooplankton community in western Svalbard, and consumption of a few Atlantic prey types, the ringed seals’ diet in Svalbard continues to be dominated by Arctic prey, especially polar cod.
TL;DR: The objective of this paper is to review their current status and to identify the factors that are influencing population dynamics in different areas to gain a better understanding of how species may respond to changes that are occurring in their ecosystems.
Abstract: Harp seals are the most abundant marine mammal in the north Atlantic. As an ice obligatory predator, they reflect changes in their environment, particularly during a period of climatic change. As the focus of a commercial hunt, a large historic data set exists that can be used to quantify changes. There are three populations of harp seals: White Sea/Barents Sea, Greenland Sea and Northwest Atlantic. Although important historically, recent catches have been low in the two northeast Atlantic populations and do not appear to be influencing trends in either population. Massive mortalities of White Sea/Barents Sea seals occurred during the mid 1980s due to collapses in their major prey. Between 2004 and 2006, pup production declined by 2/3 and has remained low. Body condition declined during the same period, suggesting that ecosystem changes may have resulted in reduced reproductive rates, possibly due to competition with Atlantic cod. The most recent estimate pf pup production in the Greenland Sea also suggests a possible decline during a period of reduced hunting although the trend in this population is unclear. Pupping concentrations are closer to the Greenland coast due to the reduction in ice in the traditional area and increased drift may result in young being displaced from their traditional feeding grounds leading to increased mortality. Reduced ice extent and thickness has resulted in major mortality of young in the Northwest Atlantic population in some years. After a period of increase, the population remained relatively stable between 1996 and 2013 due to increased hunting, multiple years with increased ice-related mortality of young seals, and lower reproductive rates. With a reduction in harvest and improved survival of young, the population appears to be increasing although extremely large interannual variations in body condition and fecundity have been observed which were found to be influenced by variations in capelin biomass and ice conditions. Each of these populations has been impacted differently by changes in their ecosystems and hunting practices. By identifying the factors influencing these three populations, we can gain a better understanding of how species may respond to changes that are occurring in their ecosystems.
TL;DR: In this article, the salinity appeared to be the most important environmental factor influencing the maintenance of cod population divergence between the western and eastern Baltic Sea, with moderate genetic differences were found between subdivisions in three traditionally delineated cod management stocks.
Abstract: Atlantic cod (Gadus morhua) is one of the most important fish species in northern Europe for several reasons including its predator status in marine ecosystems, its historical role in fisheries, its potential in aquaculture and its strong public profile. However, due to over-exploitation in the North Atlantic and changes in the ecosystem, many cod populations have been reduced in size and genetic diversity. Cod populations in the Baltic Proper, Kattegat and North Sea have been analyzed using a species specific single nucleotide polymorphism (SNP) array. Using a subset of 8,706 SNPs, moderate genetic differences were found between subdivisions in three traditionally delineated cod management stocks: Kattegat, western and eastern Baltic. However, an FST measure of population differentiation based on allele frequencies from 588 outlier loci for 2 population groups, one including 5 western and the other 4 eastern Baltic populations, indicated high genetic differentiation. In this paper, differentiation has been demonstrated not only between, but also within western and eastern Baltic cod stocks for the first time, with salinity appearing to be the most important environmental factor influencing the maintenance of cod population divergence between the western and eastern Baltic Sea.
TL;DR: The results suggest that Ahr2a is the major subtype involved in mediating responses to B[a]P in early developmental stages of Atlantic cod, which involves transcriptional regulation of biotransformation genes, such as cyp1a.
TL;DR: In this article, the shelf-life and potential indices of spoilage of frozen Atlantic cod from Greenland were studied to determine shelf life and potential index for spoilage in modified atmosphere packaging (MAP: 40% CO2 and 60% N2).
Abstract: 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% CO2 and 60% N2) 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.
TL;DR: A significant negative correlation between infection intensity and muscle mass of cod was found, suggesting parasite-induced down-regulation of growth factors in cod.
TL;DR: Specific impacts of somatic growth, sexual maturation, and spawning events on otolith zone formation in Atlantic cod (Gadus morhua) were assessed in a 33-month tank experiment, using Barents Sea data.
Abstract: Specific impacts of somatic growth, sexual maturation, and spawning events on otolith zone formation in Atlantic cod (Gadus morhua) were assessed in a 33-month tank experiment, using Barents Sea co...
TL;DR: The results suggest that environmental experience may contribute to growth differences between Baltic cod stocks, and the relative importance of environmental and genetic factors cannot be fully resolved.
Abstract: The use of growth estimation methods that depend on unreliable age data has previously hindered the quantification of perceived differences in growth rates between the two cod stocks inhabiting the Baltic Sea. Data from cod tagged in different regions of the Baltic Sea during 2007–2019 were combined, and general linear models were fit to investigate inter-regional (defined as area of release) and inter-stock (assigned to a subset of recaptures using genetic and otolith shape analyses) differences in individual growth. An average-sized cod (364 mm) caught in the western Baltic Sea and assigned to the western Baltic cod stock grew at more than double the rate (145mm year-1) on average than a cod of the same size caught in the eastern Baltic Sea and assigned to the eastern Baltic cod stock (58mm year-1), highlighting the current poor conditions for the growth of cod in the eastern Baltic Sea. The regional differences in growth rate were more than twice as large (63mm year-1) as the stock differences (24mm year-1). Although the relative importance of environmental and genetic factors cannot be fully resolved through this study, these results suggest that environmental experience may contribute to growth differences between Baltic cod stocks.
TL;DR: Two bioactive peptide fractions (SWP-I and SWP-II) of swim bladder peptides from Atlantic cod (Gadus morhua) were obtained through enzymatic hydrolysis and isolated by gel filtration chromatography as discussed by the authors.
Abstract: Two bioactive peptide fractions (SWP-I and SWP-II) of swim bladder peptides from Atlantic cod (Gadus morhua) were obtained through enzymatic hydrolysis and isolated by gel filtration chromatography...
TL;DR: The focus is upon what is already known about cod hearing, and what now needs to be known, and on what knowledge of cod hearing tells about hearing in fishes in general.
Abstract: The Atlantic cod (Gadus morhua) is among the commercially most important fish species in the world. Since sound plays such an important role in the lives of Atlantic cod and its related species, understanding of their bioacoustics is of great importance. Moreover, since cod are amenable to studies of hearing, especially in open bodies of water, they have the potential to become a “model species” for investigations of fish hearing. To serve as the basis for future studies, and to bring together what is now known about cod hearing, this paper reviews the literature to date. While there is some discussion of other species in the paper, the focus is upon what is already known about cod hearing, and what now needs to be known. An additional focus is on what knowledge of cod hearing tells about hearing in fishes in general.
TL;DR: Estimation of the spatiotemporal variations in juvenile mortality rates remains challenging, but the trend in mortality rates is beginning to be understood.
Abstract: Juvenile mortality is an important factor affecting the spatiotemporal dynamics of fish recruitment, but estimation of the spatiotemporal variations in juvenile mortality rates remains challenging....
TL;DR: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Fisheries Oceanography published by John Wiley & Sons Ltd Romagnoni and Kvile contributed equally to the article. 1Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway 2Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA 3Norwegian Meteorological Institute, Bergen, Norway 4Norwegian Institute for Water Research (NIVA), Oslo, Norway 5Department of Natural Sciences, Centre for Coastal Research (CCR), University of Agder, Kristiansand, Norway
TL;DR: It is suggested that exhaustive swimming followed by extreme crowding can reduce fillet quality, as measured by fillet redness and muscle pH, and contribute to the variable filletquality seen in trawl-caught Atlantic cod.
Abstract: Trawl-caught Atlantic cod (Gadus morhua) often yield highly variable fillet quality that may be related to capture stress. To investigate mechanisms involved in causing variable quality, commercial-sized (3.5±0.9 kg) Atlantic cod were swum to exhaustion in a large swim tunnel and subsequently exposed to extreme crowding (736±50 kg m-3) for 0, 1 or 3 hours in an experimental cod-end. The fish were then recuperated for 0, 3 or 6 hours in a net pen prior to slaughter to assess the possibility to reverse the reduced fillet quality. We found that exhaustive swimming and crowding were associated with increased metabolic stress, as indicated by increased plasma cortisol, blood lactate and blood haematocrit levels, accompanied by reduced quality of the fillets due to increased visual redness and lower initial muscle pH. The observed negative effects of exhaustive swimming and crowding were only to a small degree reversed within 6 hours of recuperation. The results from this study suggest that exhaustive swimming followed by extreme crowding can reduce fillet quality, as measured by fillet redness and muscle pH, and contribute to the variable fillet quality seen in trawl-caught Atlantic cod. Recuperation for more than six hours may be required to reverse these effects.
TL;DR: Stress-induced alterations in the lipid and fatty acid metabolism and a disrupted lipid homeostasis in larvae are suggested, providing a mechanistic link to the findings of lipid droplet overload in the liver and organ pathologies.
Abstract: Elevated environmental carbon dioxide (pCO2) levels have been found to cause organ damage in the early life stages of different commercial fish species, including Atlantic cod (Gadus morhua). To illuminate the underlying mechanisms causing pathologies in the intestines, the kidney, the pancreas and the liver in response to elevated pCO2, we examined related gene expression patterns in Atlantic cod reared for two months under three different pCO2 regimes: 380 μatm (control), 1800 μatm (medium) and 4200 μatm (high). We extracted RNA from whole fish sampled during the larval (32 dph) and early juvenile stage (46 dph) for relative expression analysis of 18 different genes related to essential metabolic pathways. At 32 dph, larvae subjected to the medium treatment displayed an up-regulation of genes mainly associated with fatty acid and glycogen synthesis (GYS2, 6PGL, ACoA, CPTA1, FAS and PPAR1b). Larvae exposed to the high pCO2 treatment upregulated fewer but similar genes (6PGL, ACoA and PPAR1b,). These data suggest stress-induced alterations in the lipid and fatty acid metabolism and a disrupted lipid homeostasis in larvae, providing a mechanistic link to the findings of lipid droplet overload in the liver and organ pathologies. At 46 dph, no significant differences in gene expression were detected, confirming a higher resilience of juveniles in comparison to larvae when exposed to elevated pCO2 up to 4200 μatm.
TL;DR: Recruitment success of 21 cod (Gadus morhua) is analysed and autocorrelation in recruitment success of fish is reported, but the underlying mechanisms are generally only alluded to.
Abstract: Autocorrelation in recruitment success of fish is frequently reported, but the underlying mechanisms are generally only vaguely alluded to. We analysed recruitment success of 21 cod (Gadus morhua) ...
TL;DR: Variability in infection intensities among 50 cod families suggests that relative resistance to L. morhua exists in cod, that it is heritable, and that broodstock selection could be used to limit the impact of microsporidian infections on growth during finfish aquaculture.
TL;DR: Chemical composition data was used to identify natal sources of cod, their broad-scale migration patterns, and to determine if cod are currently resident in Arctic fjords, and suggests that cod from the Barents Sea might have recently established residency in these two Arctic fJords.
Abstract: The distribution of Atlantic cod (Gadus morhua) in northern Norwegian waters is expanding eastward and northward in the Barents Sea and along western Svalbard. In the Arctic fjords of Svalbard, cod has become abundant, but little is known about the biology, origin, or residence patterns of these populations. To address this issue, we used laser ablation inductively coupled plasma mass spectrometry to quantify the trace elemental composition of cod otoliths at age-0, age-3 and the year of spawning at five distinct locations in northern Norway and western Svalbard. Chemical composition data was used to identify natal sources of cod, their broad-scale migration patterns, and to determine if cod are currently resident in Arctic fjords. Our results suggest that cod collected at Kongsfjord, Isfjord, outside Svalbard, Lofoten, and Porsangerfjord were recruited mainly from the Barents Sea, conforming to the Northeast Arctic cod ecotype. The degree of chemical overlap between Porsangerfjord and Isfjord cod, however, varied with fish age, suggesting individual movements consistent with the Norwegian coastal cod ecotype. Finally, the chemical composition of mature fish at Isfjord, and to a lesser extent Kongsfjord, suggests that cod from the Barents Sea might have recently established residency in these two Arctic fjords.
TL;DR: The stomach fullness in the northern subregions declined rapidly after a few years of high cod abundance, suggesting that the arrival of cod caused a top‐down effect on the prey base, not a certainty.
Abstract: Climate change is commonly associated with many species redistributions and the influence of other factors may be marginalized, especially in the rapidly warming Arctic.The Barents Sea, a high latitude large marine ecosystem in the Northeast Atlantic has experienced above-average temperatures since the mid-2000s with divergent bottom temperature trends at subregional scales.Concurrently, the Barents Sea stock of Atlantic cod Gadus morhua, one of the most important commercial fish stocks in the world, increased following a large reduction in fishing pressure and expanded north of 80°N.We examined the influence of food availability and temperature on cod expansion using a comprehensive data set on cod stomach fullness stratified by subregions characterized by divergent temperature trends. We then tested whether food availability, as indexed by cod stomach fullness, played a role in cod expansion in subregions that were warming, cooling, or showed no trend.The greatest increase in cod occupancy occurred in three northern subregions with contrasting temperature trends. Cod apparently benefited from initial high food availability in these regions that previously had few large-bodied fish predators.The stomach fullness in the northern subregions declined rapidly after a few years of high cod abundance, suggesting that the arrival of cod caused a top-down effect on the prey base. Prolonged cod residency in the northern Barents Sea is, therefore, not a certainty.