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The ability of enriched live food, such as Artemia, to improve the growth performance of Pacific cod (Gadus macrocephalus) larvae during larviculture has yet to be fully established. Thus, the effects of feeding differentially enriched Artemia to Pacific cod larvae were investigated here, specifically the effects on the survival, growth, fatty acid composition, and air exposure stress response of the larvae. Three different commercial Artemia enrichment emulsion oils were used: commercially available enrichment 1, 2, and 3, referred to as ER1, ER2, and ER3, respectively. Although ER2-treated Artemia contained the most eicosapentaenoic acid (EPA) and ER3-treated Artemia contained the most docosahexaenoic acid (DHA) and highly unsaturated fatty acid (HUFA), the ER1 enrichment improved overall survival, growth, and survival after air stress test to the greatest extent in larval Pacific cod. Furthermore, the levels of DHA and HUFA observed in larvae fed the ER1 diet were higher than the respective concentrations of these nutrients observed in larvae fed the other diets. Thus, under the experimental conditions applied in the present study, ER1 provided Artemia with DHA and EPA ratio of 4.1 for early feeding of Pacific cod larvae.

During the early development of the Pacific cod, high mortality due to viral infection is observed. To demonstrate the immune responses activated in Pacific cod during this critical period, two cytokines, the proinflammatory cytokine interleukin-8 (IL-8) and the anti-inflammatory cytokine interleukin-10 (IL-10), were identified and characterized in this study. The cDNA of IL-8 was 1047 bp in length, containing an ORF of 297 bp that encoded a 98 aa protein, whereas the IL-10 cDNA sequence consisted of 856 bp that harbored a 537 bp ORF encoding a 178 aa protein. Pairwise comparison and phylogenetic analysis of the two genes clearly demonstrated their close relationships with their counterparts in the Atlantic cod. Constitutive expression was detected in eight tested tissues; the transcription of both genes was observed during the critical period of the early developmental stage in Pacific cod, and their expression levels dramatically increased following poly I:C stimulation of larvae at 12 days post-hatching (dph). Taken together, these results suggested that IL-8 and IL-10 may be involved in the inflammatory responses of Pacific cod.

The presence of Anisakidae at retail level, after the routine screening via candling, was investigated in cod, the most commonly consumed fish species in Belgium. A total of 780 pre-packed belly flap samples destined for one branch of retail shops were collected from a Belgian wholesale company. To recover all larvae, each sample was first candled and thereafter enzymatically digested. Larvae were morphologically identified to the genus level and a subset was additionally molecularly confirmed by amplification of the ITS fragment and HinfI/HhaI enzyme restriction. The PCR/RFLP profiles of Contracaecum spp. were determined and confirmed with sequencing by the European Reference Laboratory for Parasites (Istituto Superiore di Sanità). The positivity rate of Anisakidae in the individual cod samples was 18% [95%-CI: 15–21%], with a mean intensity of one larva [range: 1–6]. Belly flaps were sold packed primarily by two, with a one-in-three chance of buying an infected package. Pseudoterranova spp. infections (single infections) were most frequently detected (positivity rate 9% [95%-CI: 7–11]), closely followed by Anisakis spp. (7% [95%-CI: 6–9]). Co-infections of Pseudoterranova spp. and Anisakis spp. comprised 8% of the infections, with a positivity rate of 1% [95%-CI: 1–3%]. All belly flaps reportedly were candled prior to our sampling, nonetheless our results indicated that an additional candling screening before packaging would identify an extra third of the infections and larvae. In 19 of the 139 infected samples, all larvae were recovered by the additional candling, thereby removing the infection risk for consumers. In conclusion, this study shows that cod belly flaps infected with zoonotic parasites reach the Belgian consumer. Although a second candling step at retail level could be helpful in reducing the consumer risk, additional measures are needed since 66% of infections would still remain undetected.

Due to the heavy fuel oil (HFO) ban in Arctic maritime transport and new legislations restricting the sulphur content of fuel oils, new fuel oil types are continuously developed. However, the potential impacts of these new fuel oil types on marine ecosystems during accidental spills are largely unknown. In this study, we studied the toxicity of three marine fuel oils (two marine gas oils with low sulphur contents and a heavy fuel oil) in early life stages of cod (Gadus morhua). Embryos were exposed for 4 days to water-soluble fractions of fuel oils at concentrations ranging from 4.1 - 128.3 µg TPAH/L, followed by recovery in clean seawater until 17 days post fertilization. Exposure to all three fuel oils resulted in developmental toxicity, including severe morphological changes, deformations and cardiotoxicity. To assess underlying molecular mechanisms, we studied fuel oil-mediated activation of aryl hydrocarbon receptor (Ahr) gene battery and genes related to cardiovascular, angiogenesis and osteogenesis pathways. Overall, our results suggest comparable mechanisms of toxicity for the three fuel oils. All fuel oils caused concentration-dependant increases of cyp1a mRNA which paralleled ahrr, but not ahr1b transcript expression. On the angiogenesis and osteogenesis pathways, fuel oils produced concentration-specific transcriptional effects that were either increasing or decreasing, compared to control embryos. Based on the observed toxic responses, toxicity threshold values were estimated for individual endpoints to assess the most sensitive molecular and physiological effects, suggesting that unresolved petrogenic components may be significant contributors to the observed toxicity.

In this study we investigated potential impacts of Cu exposure at low, environmentally relevant, concentrations on early live stages of Atlantic cod (Gadus morhua). Cod embryos and larvae were exposed to 0.5 µg/L (low), 2 µg/L (medium), and 6 µg/L (high) Cu from 4 to 17 days post fertilisation (dpf). Hatching success, mortality, oxygen consumption, biometric traits, and malformations were determined. A dynamic energy budget (DEB) model was applied to identify potential impacts on bioenergetics. A positive correlation was found between Cu exposure concentrations and Cu body burden in eggs, but not in larvae. The tested concentrations did not increase mortality in neither embryos nor larvae, or larvae deformations. Further, the DEB model did not indicate effects of the tested Cu concentrations.

8 pages, 7 tables, 3 figures, The fishing industry is often targeted as a producer of organic streams with low economic value. Biotechnological approaches can play a crucial role in transforming and adding value to these streams for their further use and upcycle. In this study, Atlantic codfish (Gadus morhua) frames, were subjected to Alcalase hydrolysis, whose optimal conditions were first fine-tuned and established as follows: 56.8 °C, pH 8.35, [Alcalase] = 0.25% (v/w) and 3 h of hydrolysis. Subsequently, under these conditions, a set of 5 L-pH-stat reactor validated the optimization tests. Our results showed that fish protein hydrolysates (FPH) exhibited a high yield of digestion (>80%) and a remarkable high degree of hydrolysis (37%). A high content of soluble protein (66 g/L), with an amino acid profile with viability for food and nutraceutical applications and a near total in vitro digestibility (>92%) were revealed. Moreover, antioxidant and antihypertensive activities were also detected. The hydrolysates presented an average molecular weight of 1709 Da and a peptide size distribution of 49% below 1 kDa and 41% in the range of 1–3 kDa. These findings suggest that Alcalase hydrolysis has the potential to recover functional bio compounds from codfish frames, boosting the economy through green technology, This research was funded by the project Xunta de Galicia (Grupos de Potential Crecimiento, IN607B 2018/19), CESAM and FCT, MCTES (UIDP/50017/2020+UIDB/50017/2020), through national funds and the project SUShI (CENTRO-01-0145-FEDER-030818) co-funded by Centro 2020 program, Portugal 2020, through the European Regional Development Fund, through the National Science Foundation (FCT, MCTES). D.P.R. is funded by a PhD grant attributed by FCT, MCTES (PD/BD/143093/2018). O.M.C.C.A. is funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19

The field of ancient DNA is taxonomically dominated by studies focusing on mammals. This taxonomic bias limits our understanding of endogenous DNA preservation for vertebrate taxa with different bone physiology, such as teleost fish. In contrast to most mammalian bone, teleost bone is typically brittle, porous, lightweight and is characterized by a lack of bone remodeling during growth. Using high-throughput shotgun sequencing, we here investigate the preservation of DNA in a range of different bone elements from over 200 archaeological Atlantic cod (Gadus morhua) specimens from 38 sites in northern Europe, dating up to 8000 years before present. We observe that the majority of archaeological sites (79%) yield endogenous DNA, with 40% of sites providing samples that contain high levels (> 20%). Library preparation success and levels of endogenous DNA depend mainly on excavation site and pre-extraction laboratory treatment. The use of pre-extraction treatments lowers the rate of library success, although — if successful — the fraction of endogenous DNA can be improved by several orders of magnitude. This trade-off between library preparation success and levels of endogenous DNA allows for alternative extraction strategies depending on the requirements of down-stream analyses and research questions. Finally, we find that — in contrast to mammalian bones — different fish bone elements yield similar levels of endogenous DNA. Our results highlight the overall suitability of archaeological fish bone as a source for ancient DNA and provide novel evidence for a possible role of bone remodeling in the preservation of endogenous DNA across different classes of vertebrates.

Mining and processing of minerals produce large quantities of tailings as waste. Some countries, including Norway, allow disposal of mine tailings in the sea. In this study we investigated the impacts of tailings from a calcium carbonate (CaCO3) processing plant on early live stages of haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua). Fish eggs (3 days post fertilisation; dpf) were exposed for 48 h to three concentrations of tailings, nominally 1 mg L−1 (low, L); 10 mg L−1 (medium, M) and 100 mg L−1 (high, H); with L and M representing concentrations occurring at tailing release points. Results show that tailings rapidly adhered to eggs of both species, causing negative buoyancy (sinking of eggs) in M and H exposures. While tailings remained on egg surfaces in both species also after exposure termination, adhesion seemed more pronounced in cod, leading to larger impacts on buoyancy even after exposure. Tailing exposure further induced early hatching and significantly reduced survival in M and H exposed embryos in both fish species, and in cod from the L exposure group. Moreover, tailing exposure caused reduced survival and malformations in larvae, potentially related to premature hatching. This study shows that mineral particles adhere to haddock and cod eggs, affecting egg buoyancy, survival and development. This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Fish communities in the shallow waters (9–20 m depth) of outer Malangen (69o N), Northern Norway was studied to investigate effects of season, bottom substrate associations and population dynamic parameters on the fish assemblages. In four fieldtrips during one year at four locations, fish were sampled by trammel nets and bottom substrate composition was monitored by underwater video. A total of 16 species of fish were caught, including four species from Pleuronectidae and six from the Gadidae family. Cod (Gadus morhua Linnaeus, 1758) was the most numerous species followed by plaice (Pleuronectes platessa Linnaeus, 1758), lemon sole (Microstomus kitt Walbaum, 1792) and halibut (Hippoglossus hippoglossus Linnaeus, 1758). Cod dominated the catches in all months except March, in which plaice and other flatfishes were most dominant. On a community scale, fish species richness was highest in October and lowest in March. Furthermore, the species richness and diversity were generally higher at locations with greater bottom substrate evenness. Cod showed a positive association with large macroalgae coverage and were less numerous at locations dominated by sand and pebble. Plaice and common dab (Limanda limanda Linnaeus, 1758) showed positive associations with sand and pebble coverage, while lemon sole was more associated with maerl beds, cobble and low algae coverage. Only halibut younger than 8 years of age were observed, and the sampling areas are suggested to be nursery area for this species. Von Bertalanffy growth functions were estimated for cod, plaice and lemon sole, and the growth coefficient K of cod and plaice were higher than for populations from adjacent fjords or the North Sea populations. Total mortality rates of cod and plaice were lower than for areas further south, and this may contribute to high and relative stable biomasses in the shallow Malangen area.

Because of their global consumption and persistence, per- and polyfluoroalkyl substances (PFASs), are ubiquitously distributed in the environment, as well as in wildlife and humans. In the present study, we have employed an ex vivo organ culture technique, based on the floating agarose method, of Atlantic cod ovarian tissue to investigate the effects of three different concentrations of PFOS, PFOA (1, 5 and 25 μM) and PFNA (0.5, 5 and 50 μM), used singly and in also in combination (1×, 20× and 100×). In the 1× exposure mixture, concentrations were decided based on their proportional levels (in molar equivalents) relative to PFOS, which is the most abundant PFAS in cod liver from a 2013 screening project. To investigate the detailed underlying mechanisms and biological processes, transcriptome sequencing was performed on exposed ovarian tissue. The number of differentially expressed genes (DEGs) having at least 0.75 log2-fold change was elevated in high, compared to low and medium concentration exposures. The highest PFNA, PFOA and PFOS concentrations, and the highest (100×) mixture exposure, showed 40, 68, 1295, and 802 DEGs, respectively. The latter two exposure groups shared a maximum of 438 DEGs. In addition, they both shared the majority of functionally enriched pathways belonging to biological processes such as cellular signaling, cell adhesion, lipid metabolism, immunological responses, cancer, reproduction and metabolism. Shortlisted DEGs that were specifically annotated to reproduction associated gene ontology (GO) terms were observed only in the highest PFOS and mixture exposure groups. These transcripts contributed to ovarian key events such as steroidogenesis (star, cyp19a1a), oocyte growth (amh), maturation (igfbp5b, tgfβ2, tgfβ3), and ovulation (pgr, mmp2). Contrary to other PFAS congeners, the highest PFOS concentration showed almost similar transcript expression patterns compared to the highest mixture exposure group. This indicates that PFOS is the active component of the mixture that significantly altered the normal functioning of female gonads, and possibly leading to serious reproductive consequences in teleosts. publishedVersion

Damage incurred during the catch process is an indicator of the overall quality of fish and fish welfare. Because catch quality is difficult to improve once it has deteriorated, it is important to preserve quality during the catch process. Atlantic cod (Gadus morhua) is the most important species in the Barents Sea bottom trawl fishery. Bottom trawling is a non-benign fishing method, and it is therefore considered important to reduce damage imparted to fish during capture, and subsequently improve catch quality and fish welfare. In the present study, the levels of damage on cod captured with a new gear design were assessed in the Barents Sea bottom trawl fishery. Furthermore, this study investigated to what extent the compulsory sorting grid and diamond mesh codend configuration employed in the fishery is responsible for the damage incurred by cod during the capture process. In total, 750 cod captured over 25 hauls were evaluated for catch damage (marks, ecchymosis, exsanguination, and scale loss). The results showed that substituting the grid and codend configuration with a four-panel selective knotless section followed by a gentle codend increased the probability of cod having no catch damage by 6.00% (CI: 0.6%–11.41%). Moreover, the gentle codend led to a significant reduction in the severity of all catch damage categories.

Acoustic scattering layers (SL) at various depths are common phenomena in most oceans, but the organisms that make up these layers vary and so does their density, and hence the backscattered energy. During two crossings of the deep Fram Strait between the shelves at Svalbard and Northeast Greenland at latitudes 77°N and 79°N, we registered epipelagic and mesopelagic SL across the entire Fram Strait and quantified their acoustic backscattered energy. In addition, one pelagic trawl haul was made at each crossing together with a CTD cast at the northern crossing. The epipelagic SL was present at 0–200 m depth, whereas the mesopelagic SL was located at 300–500 m depth during day and at shallower depths during night indicating diel vertical migrations. The epipelagic SL consisted of young-of-the-year fishes, mostly redfish Sebastes sp. No trawl hauls were made in the mesopelagic SL, and the identity of organisms is unknown. Few strong echoes from single targets at mesopelagic depths stood out from the rest of the targets and were interpreted as adult Atlantic cod Gadus morhua. This is the first report of scattering layers covering the whole distance of the deep parts of the Fram Strait, and strengthen the assumption about an east–west connection of organisms and young-of-the-year fishes originating from the spawning grounds along the Norwegian coast and the western Barents Sea towards Northeast Greenland.

Publisher's version (útgefin grein), Extracellular vesicles (EVs) are released from cells and carry protein and genetic cargo involved in cell communication. EVs isolated from bodyfluids, including plasma and serum, can also be used as markers of pathophysiological changes. Peptidylarginine deiminases (PADs) are phylogenetically conserved enzymes with physiological and pathophysiological roles and cause post-translational protein deimination. This can affect function of target proteins and deimination is also linked to EV release. Atlantic cod (Gadus morhua L.) reared at 4 °C and 9 °C respectively for 18 months, were here assessed for changes in serum derived EVs, including analysis of deiminated protein and micro-RNA cargo markers related to stress and growth. We found that cod reared at 9 °C showed significantly reduced numbers of EVs in serum, compared to cod reared at 4 °C. Some deiminated protein targets, including complement component C3, were found to be considerably higher in EVs of cod reared at 4 °C. Proteomic analysis revealed further differences in deiminated protein targets in EVs isolated from sera of the two temperature groups. Whole cod sera from the two temperature groups furthermore showed differences in deiminated protein targets, including C3, CRP and histone H3, which is a marker of neutrophil extracellular trap formation. MicroRNAs related to inflammation (miRNA-21) and stress (miRNA-155) were elevated in both total cod serum and serum-derived EVs from the 9 °C group, while the growth-related miRNA-206 was higher in the 4 °C group. Our findings highlight EVs as novel biomarkers to assess fish health in response to environmental rearing temperature., The authors would like to thank the staff at the Marine Institute’s experimental station Staður, Grindavík, Iceland for providing the fish and sampling facilities and Yagnesh Umrania and Michael Deery at the Cambridge Centre for Proteomics for the LC-MS/MS analysis. This study was funded in part by the Icelandic Research Council (RANNIS) , the EC grant Fishaid QLK2-CT-2000-01076 and a University of Westminster start-up grant to SL. Thanks are also due to The Guy Foundation for funding the purchase of equipment utilised in this work. The authors declare no competing interest.

Shorthorn sculpin (Myoxocephalus scorpius) and large cod (300–400 g body weight) are important predators on newly settled 0-group cod (Gadus morhua) and saithe (Pollachius virens) in Porsangerfjorden in northern Norway. The Atlantic wolffish (Anarhichas lupus) used to be abundant but is now very rare in the fjord. Video recorded experiments showed that interactions between shorthorn sculpins, wolffish and large cod affected predation rates on small 0-group cod and saithe in tanks with a gravel, cobble and seaweed (Fucus serratus) substrate. We found that sculpins were unable to catch 0-group specimens when they were the only predatory species in the experimental tank and the lights were left on 24 h a day (to simulate the midnight sun), and that they did not even attempt to catch them. The addition of a large cod to the tank increased sculpin attack rates and predation success significantly. The “cod effect” was due to 0-group specimens avoiding attacks by escaping into the cobbles or vegetation, were they could be more easily reached by the sculpins. When tanks were supplemented with a wolffish in addition to the cod, both sculpin and cod predation success was lowered by approximately 50% in the 24-h light regime. When the experimental setup was changed to a day/night light cycle, however, the wolffish presence had no effect. Also, sculpins in tanks without cod and wolffish went from consuming zero to 29% of the 0-group specimens in the tank when the light regime went from 24-h light to day/night. Sculpins and cod were most effective predators on 0-group cod and saithe at dusk/night/dawn, and the presence of a cruising predator like cod increased sculpin predation success and probably vice versa. The experimental data indicate that rebuilding wolffish stocks in the fjord system may make the bottom substrate more protective for 0-group specimens of cod and saithe, by limiting the foraging volume of an effective bottom-dwelling 0-group predator like the sculpin. Further field and lab studies must be conducted before the reported findings optionally can be turned into a management advice.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. To prevent unwanted fish bycatch from entering the trawl, we modified a counter-herding device, FLEXSELECT, developed for a Northeast Atlantic Nephrops (Nephrops norvegicus) trawl fishery. FLEXSELECT, which was designed to direct fish away from the trawl by means of sweeping ropes in the herding area, has been shown to be highly effective on both roundfish and flatfish species. However, by adding sweeping elements we could be increasing the benthic impact of trawling. Therefore, in this study we investigated if the effect of FLEXSELECT can be maintained when raising the ropes off the seabed. A reduction in fish bycatch could still be achieved, but the effect of FLEXSELECTraised with respect to the previous design was significantly different for four of the seven species analysed. While for some species the effect was lower, it substantially increased for cod (Gadus morhua), making it highly relevant for the Nephrops fisheries, as well as for other fisheries in needs of avoiding cod catches. The results offer insights regarding species behavioural responses to FLEXSELECTraised, to be used for future developments of counter-herding devices in commercial fisheries without the addition of seabed impact to the baseline gears.

Gillnets are among the most widely used fishing gear in global fisheries because of their simplicity, high operability, catch efficiency and low entrance cost for fishermen. In Norway, the Northeast Atlantic (NEA) cod (Gadus morhua) fishing industry represents the most important economic single species fishery and the gillnet fishery accounts for 24% of the national total allowable catch (TAC) of NEA cod. Despite the importance of the gillnet fishery in Norway, significant amounts of gillnets are lost at sea each year. As gillnets are made of synthetic materials (i.e. nylon) with high breaking strength and durability, lost, abandoned and/or discarded fishing gear (LADFG) continues catching target and non-target species for years. This phenomenon, known as "ghost fishing", cause negative impact on the benthic marine environment and to the fisheries management. Over the last years, the development of biodegradable gillnets to replace traditional nylon gillnets has become particularly sought after in fisheries worldwide. However, biodegradable gillnets are less efficient and more expensive than traditional nylon gillnets. As the urgency to eliminate the negative environmental impacts of LADFG increases, a crucial question remains how to successfully implement biodegradable gillnets to replace the more efficient nylon gillnets currently used in commercial fisheries. In this article we investigate how central elements of fisheries management may be used to implement biodegradable gillnets and how this may challenge the current resource allocation policy among different gear- and vessel groups.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Stable isotope and elemental analyses of the Atlantic cod (Gadus morhua) and harp seal (Phoca groenlandica) bone component of the marine food that dominated the Younger Stone Age (c. 6.1–3.5 ka BP) diet in Varanger, Arctic northern Norway, indicate, at times, climate change induced highly elevated levels of the heavy metals cadmium (Cd) and lead (Pb), and elevated levels of mercury (Hg). On average, the levels of cadmium and lead contamination in cod were up to 22 and 3–4 times, respectively, higher than today's recommended limits in soft tissue. The corresponding figures for seal were 15 and 3–4 times, respectively. The levels of Hg were generally below today's recommended limit in soft tissue, but still of considerable magnitude, almost similar to the measured values in modern fish in the Arctic. This shows that marine food in the Younger Stone Age was unhealthy, if not unsafe. We discuss this unexpected knock-on effect in terms of sea surface temperatures and sea level change. The elevated values may have been detrimental for humans, if not for society; a balancing factor may have been a larger component of terrestrial resources than previously assumed. Concomitantly, this contribution to the paleo base-line record of toxicity may lead to predictions for seafood contamination in the future.

A multitude of recent studies have documented the detrimental effects of crude oil exposure on early life stages of fish, including larvae and embryos. While polycyclic aromatic hydrocarbons (PAHs), particularly alkyl PAHs, are often considered the main cause of observed toxic effects, other crude oil derived organic compounds are usually overlooked. In the current study, comprehensive two-dimensional gas chromatography coupled to mass spectrometry was applied to investigate the body burden of a wide range of petrogenic compounds in Atlantic haddock (Melanogrammus aeglefinus) and cod (Gadus morhua) embryos that had been exposed to sublethal doses of dispersed crude oil. Several groups of alkylated monoaromatic compounds (e.g. alkyl tetralins, indanes and alkyl benzenes), as well as highly alkylated PAHs, were found to accumulate in the fish embryos upon crude oil exposure. To investigate the toxicity of the monoaromatic compounds, two models (1-isopropyl-4-methyltetralin and 1-isopropyl-4-methylindane) were synthesized and shown to bioaccumulate and cause delayed hatching in developing embryos. Minor developmental effects, including craniofacial and jaw deformations and pericardial edemas, were also observed at the highest studied concentrations of the alkylindane.

peer-reviewed The application of natural preservatives on fresh fish has potential to extend shelf-life. In the present study, 8 essential oils (EOs) (lemon, lemongrass, lime, garlic, onion, oregano, thyme and rosemary) and 3 organic acids (OAs) (ascorbic, citric and lactic) were evaluated. The antimicrobial activity of these compounds was tested in-vitro against four confirmed Listeria spp. isolated from retail skin-packed salmon and cod. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were established for each compound. Then, a sensory evaluation was performed by a panel of ‘expert assessors’ on cooked fish treated with all of the OAs and any 4 EOs with a MIC

Regular discharges of produced water from the oil and gas industry represents the largest direct discharge of effluent into the marine environment worldwide. Organic compound classes typically reported in produced water include saturated hydrocarbons, monoaromatic and polyaromatic hydrocarbons (MAHs, PAHs) as well as oxygenated compounds, such as phenols, acids and ketones. This forms a cocktail of known and suspect toxicants, but limited knowledge is yet available on the sub-lethal toxicity of produced water to cold-water marine fish species. In the present work, we conducted a 4-day exposure of embryos of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) to produced water extracts equivalent to 1:50, 1:500 and 1:5000 times dilutions of raw effluent. No significant reduction in survival or hatching success was observed, however, for cod, hatching was initiated earlier for exposed embryos in a concentration-dependent manner. During recovery, significantly reduced embryonic heart rate was observed for both species. After hatch, larvae subjected to embryonic exposure to produced water extracts were smaller, and displayed signs of cardiotoxicity, jaw and craniofacial deformations. In order to improve risk assessment and regulation of produced water discharges, it is important to identify which produced water components contribute to these effects.

Atlantic cod (Gadus morhua) is an important recreational and commercial fisheries target species in the Northern hemisphere. Release rates are high in the recreational fishery due to regulatory and voluntary catch-and-release practice. Although post-release mortality of cod is relatively low, there is potential for further reductions. The most effective way to reduce post-release mortality is to minimize the catch of sublegal fish or non-target species and to reduce hooking injuries by using more selective fishing methods. This study investigated the influence of the lure/bait type on: (1) size of fish, (2) catch and harvest, (3) proportion of bycatch, (4) hooking location, and (5) injury (bleeding) in the western Baltic Sea recreational cod fishery. Data were collected via random onboard sampling of 35 charter vessel angling trips (778 anglers) and during two supplementary studies in the western Baltic Sea. Overall, the median total length was significantly higher for cod caught on artificial lures (39 cm) than for cod caught on natural bait (28 cm), leading to a 43% higher proportion of sublegal (

Source at https://doi.org/10.1016/j.fishres.2019.105337. Shrimp trawlers often use a Nordmøre sorting grid ahead of a small mesh codend to avoid bycatch of juvenile fish while allowing shrimps to be efficiently caught. However, small fish can pass through the grid to enter the codend and risk being retained. The risk of retention for fish of different sizes depends the size selection in the Nordmøre grid and the size selection in the subsequent codend, which makes the process complex and often results in a bell-shaped size selection curve. In the Barents Sea shrimp fishery, cod (Gadus morhua) is one of the species of concern because of its great commercial value. We studied the size selection of juvenile cod when the trawl was equipped with the compulsory gear in the fishery: a 19 mm Nordmøre grid followed by a 35 mm diamond mesh codend. As expected, the size selection curve showed a bell-shaped signature, with a certain size range of juveniles having high retention risk, while the risk for smaller and bigger cod was smaller. The retention risk was highest for cod between 12 and 20 cm in length. We also tested two alternative designs in the aft section of the gear: a codend with 35 mm square mesh panels and a square mesh sorting cone section. Neither of these designs affected the size selection in the trawl significantly.

During accidental crude oil spills and permitted discharges of produced water into the marine environment, a large fraction of naturally occurring oil components will be contained in micron-sized oil droplets. Toxicity is assumed to be associated with the dissolved fraction of oil components, however the potential contribution of oil droplets to toxicity is currently not well known. In the present work we wanted to evaluate the contribution of oil droplets to effects on normal development of Atlantic cod (Gadus morhua) through exposing embryos for 96 h to un-filtered (dispersions containing droplets) and filtered (water soluble fractions) dispersions in a flow-through system at dispersion concentrations ranging from 0.14 to 4.34 mg oil/L. After exposure, the embryos were kept in clean seawater until hatch when survival, development and morphology were assessed. The experiment was performed at two different stages of embryonic development to cover two potentially sensitive stages (gastrulation and organogenesis). Exposure of cod embryos to crude oil dispersions caused acute and delayed toxicity, including manifestation of morphological deformations in hatched larvae. Oil droplets appear to contribute to some of the observed effects including mortality, larvae condition (standard length, body surface, and yolk sac size), spinal deformations as well as alterations in craniofacial and jaw development. The timing of exposure may be essential for the development of effects as higher acute mortality was observed when embryos were exposed from the start of gastrulation (Experiment 1) than when exposed during organogenesis (Experiment 2). Even though low mortality was observed when exposed during organogenesis, concentration-dependent mortality was observed during recovery. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.fishres.2019.02.009. The purpose of this study was to investigate the extent of external damage (gear marks, pressure injuries, ecchymosis and skin abrasion) present on trawl-caught cod (Gadus morhua) and to examine whether the extent of damage could be reduced by introducing changes in the gear. We tested whether changing the 2-panel knotted codend used by the Norwegian trawler fleet operating in the Barents Sea today to a 2-panel knotless codend or a 4-panel knotless codend could decrease the extent of external damage to the fish in the catch. We evaluated 720 fish over 12 hauls carried out with a twin trawl setup and found that the probability for cod to be without any external damage was 9.4% (4.7%–15.8%) with the codend used in the fishery today. Thus, most fish in these catches are likely to have slight or moderate damage. Gear marks were the most frequent type of damage, with only 11.5% (6.0%–18.9%) of the cod being free of this type of injury. When gear marks were not considered in the analysis, 68.4% (58.8%–78.3%) of the fish was estimated to be flawless. Replacing the knotted netting in the codend increased the probability of obtaining fish without gear marks to 15.5% (6.2%–28.0%). However, the confidence intervals were wide, and this effect was not statistically significant. For the other three damage types, the estimated effects of changing the design of the codend were small and not statistically significant. Changing from a 2- to 4-panel codend was estimated to reduce the probability for gear marks by a further 1.7% (−13.4%–16.8%). However, this increase was not significant. Overall, the two codend design changes tested in this study did not significantly decrease the external damage present on trawl-caught cod.

The nitrogen isotopic composition (δ^(15)N) of otolith-bound organic matter (OM) is a potential source of information on dietary history of bony fishes. In contrast to the δ^(15)N of white muscle tissue, the most commonly used tissue for ecological studies, the δ^(15)N of otolith-bound OM (δ^(15)N_(oto)) provides a record of whole life history. More importantly, δ^(15)N_(oto) can be measured in contexts where tissue is not available, for example, in otolith archives and sedimentary deposits. The utility and robustness of otolith δ^(15)N analysis was heretofore limited by the low N content of otoliths, which precluded the routine measurement of individual otoliths as well as the thorough cleaning of otolith material prior to analysis. Here, we introduce a new method based on oxidation to nitrate followed by bacterial conversion to N_2O. The method requires 200-fold less N compared to traditional combustion approaches, allowing for thorough pre-cleaning and replicated analysis of individual otoliths of nearly any size. Long term precision of δ^(15)N_(oto) is 0.3‰. Using an internal standard of Atlantic cod (Gadus morhua) otoliths, we examine the parameters of the oxidative cleaning step with regard to oxidant (potassium persulfate and sodium hypochlorite), temperature, and time. We also report initial results that verify the usefulness of δ^(15)N_(oto) for ecological studies. For three salmonid species, left and right otoliths from the same fish are indistinguishable. We find that the δ^(15)N_(oto) of pink salmon (Oncorhynchus gorbuscha) is related to the size of the fish for this species. We find that intra-cohort δ^(15)N_(oto) standard deviation for wild pink salmon, farmed brown trout (Salmo trutta), and farmed rainbow trout (Oncorhynchus mykiss) are all 0.4‰ or less, suggesting that δ^(15)N_(oto) will be valuable for population-level studies. Lastly, our protocol yields reproducible data for both δ^(15)N_(oto) and otolith N content in 17th century Atlantic cod otoliths. We find that 17th century cod are approximately 2 ‰ higher than modern cod, arguably consistent with either the larger size of the otoliths (and thus inferred for the fish) or with changes in baseline (primary producer) δ^(15)N in the modern coastal ocean compared to the past. All told, the results of this study bode well for the utility of otolith-bound δ15N for investigating the environment and ecology of modern and past fish.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.fishres.2018.01.021. In recent years, Norwegian fishermen have reported problems with fish accumulation in front of the mandatory sorting grids (Sort-X, Sort-V, and Flexigrid). These problems are associated with high fish entry rates and low water flow through the grid sections. In this study, we replaced the lifting panel in the original design of a sorting grid section (Sort-V) by another steel grid (“lower grid”) in order to improve water flow and increase sorting area. Two different inclination angles of this new additional “lower grid” were tested. The results demonstrated that both the lower grid and the main grid contributed to the release of cod and haddock. However, the release efficiency of the lower grid was low compared to that of the main grid. A larger proportion of fish contacted at least one of the grids with the lower grid set at 40° compared to at 35°. The new double grid was found to release significantly more haddock between 38 and 50 cm long than the mandatory Flexigrid. For cod, the sorting system was at least as good as the Flexigrid at releasing undersized fish. Thus, the new double grid system represents a potential alternative to the Flexigrid. Although the Sort-V single grid releases significantly more undersized cod and haddock than the new double grid system, it also releases a significantly higher proportion of the targeted commercial sizes.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.fishres.2018.05.021. The dense aggregations of Northeast Atlantic cod (Gadus morhua) in the Barents Sea have led to a new fishing practice termed “buffer towing.” In this fishery, many trawlers redeploy the trawl directly after taking the catch onboard in an attempt to secure a continuous supply of fish and avoid any unnecessary stops during processing. If the approximate desired amount of fish is caught or exceeded before the catch from the previous haul is processed, the trawl is lifted off the seabed and towed at a given depth at low speed, usually ∼1–2 knots, until the production capacity of the onboard factory is restored. Both researchers and fishermen onboard trawlers believe that buffer towing has a negative impact on fish quality, as indicated by increased frequency of gear marks and dead fish, poorer exsanguination, ecchymosis, skin abrasion, fillet gaping, and fillet redness. However, the effect that buffer towing has on fish quality has not been scientifically evaluated. The aim of this study was to document the effects of buffer towing on fish quality. The quality was assessed using two different indexes, one for whole cod and one for cod fillets. The results proved that buffer towing has a negative impact on fish quality. Specifically, cod subjected to buffer towing, in contrast to direct haul-back, had an increased relative probability of 371% for poor exsanguination and an increased relative probability of 209% for fillet redness. Furthermore, combining scores of the different quality categories within the indexes (e.g., gear marks, ecchymosis, poor exsanguination, and skin abrasion) proved a significant reduction in the quality of cod subjected to buffer towing.

MicroRNAs (miRNAs) are known to play important immunoregulatory roles in teleosts, although miRNAs involved in the antiviral immune response of Atlantic cod (Gadus morhua) were previously uncharacterised. Using deep sequencing and qPCR, the present study was conducted to identify miRNAs responsive to the viral mimic, polyriboinosinic polyribocytidylic acid (pIC) in Atlantic cod macrophages. Macrophage samples isolated from Atlantic cod (n = 3) and treated with pIC or phosphate buffered saline (PBS control) for 24 and 72 h were used for miRNA profiling. Following deep sequencing, DESeq2 analyses identified four (miR-731-3p, miR-125b-3-3p, miR-150-3p and miR-462-3p) and two (miR-2188-3p and miR-462-3p) significantly differentially expressed miRNAs at 24 and 72 h post-stimulation (HPS), respectively. Sequencing-identified miRNAs were subjected to qPCR validation using a larger number of biological replicates (n = 6) exposed to pIC or PBS over time (i.e. 12, 24, 48 and 72 HPS). As in sequencing, miR-731-3p, miR-462-3p and miR-2188-3p showed significant up-regulation by pIC. The sequencing results were not qPCR-validated for miR-125b-3-3p and miR-150-3p as up- and down-regulated miRNAs at 24 HPS, respectively; however, qPCR results showed significant up-regulation in response to pIC stimulation at later time points (i.e. 48 and/or 72 HPS). We also used qPCR to assess the expression of other miRNAs that were previously shown as immune responsive in other vertebrates. qPCR results at 48 and/or 72 HPS revealed that miR-128-3-5p, miR-214-1-5p and miR-451-3p were induced by pIC, whereas miR-30b-3p and miR-199-1-3p expression were repressed in response to pIC. The present study identified ten pIC-stimulated miRNAs, suggesting them as important in antiviral immune responses of Atlantic cod macrophages. Some pIC-responsive miRNAs identified in this study were predicted to target putative immune-related genes of Atlantic cod (e.g. miR-30b-3p targeting herc4), although the regulatory functions of these miRNAs need to be validated by future studies.

A promising design to improve selectivity in the Nephrops-directed trawl fishery is the horizontally divided trawl codend. Previous studies have succeeded in separating the majority of fish from Nephrops; however, cod (Gadus morhua), juvenile roundfish and flatfish still enter the lower compartment in relative high proportions. In this study we investigated if and to which extent it is possible to improve the vertical separation of fish from Nephrops by adding active behaviour stimulators. These stimulators are designed to exploit fish avoidance behaviour and lead them into the upper compartment while Nephrops move into the lower compartment. We tested two types of behaviour stimulators: a chain curtain at the entrance of the lower compartment at the point of separation and a set of rising float-lines inserted ahead of the point of separation. The length-dependent vertical separation of five important commercial fish species and Nephrops was analysed in comparison to the horizontally divided trawl codend with no stimulator, towed in parallel to the test trawl. The results showed that fish’s vertical separation can be partially improved by the addition of stimulators, without complicating fishing operations or increasing the proportion of Nephrops that enters the upper compartment. However, the improvement was limited and none of the two active stimulators tested managed to simultaneously improve the separation of cod, juvenile roundfish and flatfish.

The Atlantic cod (Gadus morhua) is a species of significant economic and historic importance but infamous for its decline. Apart from overfishing, the causes of this decline and its subsequent lack of recovery remain largely unresolved. Indeed, the degree to which specific habitats are important for this species remains unquantified at the scale of North Atlantic. Here, the literature on the role of eelgrass meadows (Zostera marina) as valuable nursery habitat for the Atlantic cod is reviewed and synthesized. Evidence is presented on relative densities of Atlantic cod in shallow water environments and in eelgrass meadows in comparison to alternative habitats. In addition, evidence pertaining to the ’viability gains’ attributed to the use of eelgrass meadows as nursery habitat (growth and survival) by juvenile Atlantic cod is analyzed. Although juvenile Atlantic cod use of Z. marina is found to be facultative, when possible, available literatures indicates that they may select Z. marina as a nursery habitat where they are found in high density (average of at least 246 ha−1). From their use of Z. marina habitat the juvenile Atlantic cod receives viability benefits from it, improving their chances of reaching maturation. This paper provides strong evidence that eelgrass meadows are of significant importance to contributing to Atlantic cod stocks. Keywords: Zostera marina, Eelgrass, Gadus morhua, Fisheries, Juveniles, Nursery habitat

Fresh by-products of whitefish such as cod and saithe is processed to fishmeal (FM) on-board seagoing Norwegian trawlers. The aim of this study was to document the properties of whitefish FM (WFM) protein with respect to, physicochemical and bioactive properties. Analysis of the proximate composition of representative seasonal WFM batches show that the production is robust without much variance. The mean protein (61.9 ± 1.2), fat (8.9 ± 1.1%), moisture (5 ± 1.2%) and ash content (22.4 ± 0.8%), reflect the use of lean and bony raw-material. The WFM has a low content of free amino acids (0.7%) and biogenic amines (< 1000 mg/kg) that confirm the high quality and freshness of the raw material. Amino-acid analysis identified the presence of all nutritionally essential amino acids. The WFM physicochemical properties was comparable to soy-bean meal (SBM) by analysis of solubility, water-holding capacity (WHC), the emulsion stability (ES). Proteolytic degradation of the WFM was used to demonstrate the presence of bioactive peptides with inhibiting activity against angiotensin-converting enzyme (ACE) activity, in vitro. Taken together, WFM produced from fresh by-products is an excellent protein source with attributes of interest beyond the aquafeed-market. /© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

8 pages, 3 figures, 3 tables, Species-specific lateral flow dipstick (LFD) assays for the identification of Atlantic cod (Gadus morhua), Pacific cod (Gadus macrocephalus), Alaska pollock (Gadus chalcogrammus) and ling (Molva molva) in food products were developed. The method comprises a PCR system with four sets of specific primers, for each target species. This step was also devised to dual-labeling of PCR products with biotin and 6-FAM, which are then easily read on a lateral flow dipstick, upon which these products are immobilized by a fixed biotin-ligand and visualized with anti-FAM antibody-coated gold nanoparticles. Sensitivity and selectivity were determined for each of the developed assays. Validation of the assays was performed with DNA extracted from commercial fish products, the identification of all samples by PCR-LFD was coherent with the results found with DNA sequencing. Target species were successfully detected in analyzed commercial samples, demonstrating the applicability of this method to the rapid analysis of food products, The work was supported by the projects “GENTRASEA: Genetic traceability of fish products. Rapid methods with DNA hybridization probes” funded by Spanish Ministry of Science and Innovation and “LABELFISH: Atlantic network on genetic control of fish and seafood labelling and traceability.” Funded by Atlantic Area Programe (UE). The Spanish Ministry of Science and Innovation is gratefully acknowledged for the doctoral fellowship to Ledicia Taboada, who is a PhD student at the University of Santiago de Compostela

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available in Fisheries Research (2017), 193, 158-163. Wild Atlantic cod of commercial size (1.9 ± 0.5 kg) were swum to exhaustion in a large swim tunnel in an attempt to mimic the initial stage of trawling, when fish swim at the trawl mouth until they fatigue or lose interest and subsequently drop into the trawl. The objective of the study was to investigate if exhaustive swimming in unstressed cod had any negative effects on fillet quality, and if post-exercise recuperation for 2, 4, 6, or 10 h could reverse such potential effects. Exhaustive swimming increased muscle stiffness during rigor mortis, but did not change time to maximum stiffness or cause any marked increase in fillet redness. Plasma lactate and cortisol were elevated after exercise, but recovered steadily during the recuperation period. Swimming to exhaustion also caused a drop in muscle pH, which returned to pre-exercise level within four hours of recuperation. We conclude that exhaustive swimming in unstressed Atlantic cod only has a moderate and reversible short lasting negative effect on flesh quality, which is less severe than the poor quality frequently observed in commercially caught cod.

The genome of Atlantic cod (Gadus morhua L.) published in 2011 was the first example of a teleost genome obtained using a pure high-throughput sequencing (HTS) technology strategy, and the first large vertebrate genome generated by exclusively using Roche/454 sequencing technology. At the start of the sequencing project in 2009, two HTS technologies were available, the Roche/454 and Illumina technologies. Because of the longer read length of the Roche/454 technology and a wider range of suitable software utilizing those data at the time, we chose to use this technology for the first version of the Atlantic cod genome. In this chapter, we describe the process leading to the assembly and annotation of the first Atlantic cod genome. Since the release in 2011, spectacular developments in sequencing technologies and assembly software have allowed for a second, improved version of the Atlantic cod genome—which will be further described in the Atlantic cod genome chapter ( Chapter 3 ). Although rather fragmented according to current standards, our first genome assembly has proven to be an important resource for the community—as illustrated by its extensive use in a wide range of studies and it catalyzing new projects and research funding.

Technological solutions regarding automated sorting of food according to their quality parameters are of great interest to food industry. In this regard, automated sorting of fish rest raw materials remains as one of the key challenges for the whitefish industry. Currently, the sorting of roe, milt, and liver in whitefish fisheries is done manually. Automated sorting could enable higher profitability, flexibility in production and increase the potential for high value products from roe, milt and liver that can be used for human consumption. In this study, we investigate and present a solution for classification of Atlantic cod (Gadus morhua) roe, milt and liver using visible and near-infrared hyperspectral imaging. Recognition and classification of roe, milt and liver from fractions is a prerequisite to enabling automated sorting. Hyperspectral images of cod roe, milt and liver samples were acquired in the 400–2500 nm range and specific absorption peaks were characterized. Inter- and intra-variation of the materials were calculated using spectral similarity measure. Classification models operating on one and two optimal spectral bands were developed and compared to the classification model operating on the full VIS/NIR (400–1000 nm) range. Classification sensitivity of 70% and specificity of 94% for one-band model, and 96% and 98% for two-band model (sensitivity and specificity respectively) were achieved. Generated classification maps showed that sufficient discrimination between cod liver, roe and milt can be achieved using two optimal wavelengths. Classification between roe, milt and liver is the first step towards automated sorting. © 2015 Elsevier Ltd. All rights reserved. This is the authors’ accepted and refereed manuscript to the article. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

The Baltic is a semi-enclosed sea characterised by decreasing salinity in the eastern and northern direction with only the deeper parts of the southern Baltic suitable as spawning grounds for marine species like cod. Baltic cod exhibits various adaptations to brackish water conditions, yet the inflow of salty North Sea water near the bottom remains an influence on the spawning success of the Baltic cod. The eastern Baltic population has been very weakly studied in comparison with the western population. The aim of this study is to demonstrate for the first time genetic differentiation by the use of a large number of SNPs between eastern and western Baltic populations existing in differentiated salinity conditions. Two cod samples were collected from the Bay of Gdansk, Poland and one from the Kiel Bight, Germany. Samples were genotyped using a cod derived SNP-array (Illumina) with 10 913 SNPs. A selection of diagnostic SNPs was performed. A set of 7944 validated SNPs were analysed to assess the differentiation of three samples of cod. Results indicated a clear distinctness of the Kiel Bight from the populations of the eastern Baltic. FST comparison between both eastern samples was non-significant. Clustering analysis, principal coordinates analysis and assignment test clearly indicated that the eastern samples should be considered as one subpopulation, well differentiated from the western subpopulation. With the SNP approach, no differentiation between groups containing ‘healthy’ and ‘non-healthy’ cod individuals was observed.

[EN] Low-temperature convective drying could be considered an affordable alternative to conventional freeze-drying for foodstuffs. The process intensification should be based on non-thermal technologies, such as power ultrasound. Thereby, the aim of this work was to evaluate the air-borne application of power ultrasound on the low-temperature drying of salted cod. For that purpose, drying experiments were carried out at −10, 0, 10 and 20 °C on salted cod slices at 2 m/s with (AIR + US, 20.5 kW/m3) and without ultrasonic application (AIR). In the dried-salted cod, its rehydration capacity was analyzed, as were the microstructural, textural and color changes. At every temperature tested, ultrasound application increased the drying rate; thus, an average increase of 74%was observed in the effective diffusivity. AIR+US dried samples were softer and exhibited a higher rehydration capacity than AIR ones, which was linked to the microstructural changes produced by ultrasound. In addition, color changes were induced by ultrasound application. Industrial relevance: Nowadays, low-temperature convective drying represents a promising alternative for the production of high-quality dried products. However, this technology is mostly limited by the low drying rate, which retards the dehydration process and directly increases the processing costs. Power ultrasound, a nonthermal technology, represents an interesting alternative means of improving low-temperature convective drying due to the fact that acoustic (mechanical)waves may affectwater removal during dryingwith a low heating capacity. Thereby, the ultrasonically enhanced low-temperature convective drying could constitute an affordable alternative to lyophilization (or freeze-drying), which is mainly restricted to high-quality food commodities., The authors acknowledge the financial support both from the Ministerio de Economia y Competitividad (Ref. DPI2012-37466-C03-03) and Carmen Cambra S.L. for their technical support with the selection of the raw material. Cesar Ozuna was the recipient of a fellowship from the Universitat Politecnica de Valencia for his research stay in Aalesund University College.

A hypothesis suggesting that variability in recruitment of Atlantic cod (Gadus morhua) is caused by variable energy flow patterns in the community during the post-settlement 0-group phase was tested. Studies of diets, growth, and survival patterns in contrasting locations on the Norwegian Skagerrak coast show that for the 0 to 3 months after attaining a benthic mode of life, cod juveniles continue to depend on planktonic prey with high energy content. Early shifts to hyperbenthic prey such as fish and prawns result in poor condition and low survival. It is suggested that gradual eutrophication may induce abrupt shifts in the energy flow pattern in the plankton community that are propagated to higher trophic levels. This may explain repeated incidents of abrupt and persistent recruitment collapses in fishes along the Norwegian Skagerrak.

The search for an alternative means of reconstituting dried and salted products prior to consumption is of relevance for the food industry. New techniques should speed up the process while causing minimum impact on product quality. Thereby, the aim of this work was to evaluate both the effect of high-intensity ultrasound application on the desalting kinetics of cod, as well as the changes in its textural and microstructural properties. Moisture and NaCl transport was studied separately by taking the diffusion theory into account. The evolution in the swelling and hardness of cod during desalting was determined and modeled by assuming first-order kinetics. A microstructural analysis of raw salted and desalted cod was also carried out by means of light microscopy and SEM techniques. Ultrasound application significantly (p < 0.05) affected both moisture and NaCl transport and the increase in both effective diffusivities (from 24% to 103%) was linked to the acoustic pressure applied. The desalting process induced the swelling and the softening of the cod tissue, both of which are phenomena that are intensified by ultrasound application. From the microstructural observations, it was shown that the application of highintensity ultrasound modified the cod structure, e.g. the increase in the fiber width., The authors acknowledge the economic support of the project ref. DPI2013-37466-C03-03 co-funded by the Spanish Ministerio de Economia y Competitividad and the European Regional Development Found (ERDF). Cesar Ozuna thanks Universitat Politecnica de Valencia for an FPI grant (Ref. 2009-02). The author also wishes to thank Carmen Cambra S.L. for selecting the raw material.

A time series of annual beach seine surveys run since 1919 on the Norwegian Skagerrak coast revealed repeated incidents of abrupt and persistent recruitment collapses in young-of-the-year gadoids in relation to increasing nutrient loads. To explore potential underlying causes of the recruitment patterns, a three-year study of processes associated with settlement and the postsettlement period in gadoids was conducted. With Atlantic cod (Gadus morhua) as a model species, the following hypothesis underlying the recruitment collapses is proposed: The survival of 0-group cod is limited by food availability after settlement (3–5 months old), and recruitment variability results from differences in food supply due to inter-annual variability in the energy flow pattern at low trophic levels of the pelagic food web. By postulating that food availability shows high inter-annual variation and that gradually increasing nutrient loads results in abrupt and persistent food deprivation of the 0-group gadoids, this hypothesis potentially explains both natural recruitment variability and eutrophication-induced recruitment collapses of cod and the other gadoids.

In the aquatic environments, the predicted changes in water temperature, pO2 and pCO2 could result in hypercapnic and hypoxic conditions for aquatic animals. These conditions are thought to affect several basic cellular and physiological mechanisms. Yet, possible adverse effects of elevated CO2 (hypercapnia) on teleost fish, as well as combined effects with emerging and legacy environmental contaminants are poorly investigated. In this study, juvenile Atlantic cod (Gadus morhua) were divided into groups and exposed to three different water bath PFOS exposure regimes (0 (control), 100 and 200 μg L−1) for 5 days at 1 h/day, followed by three different CO2-levels (normocapnia, moderate (0.3%) and high (0.9%)). The moderate CO2 level is the predicted near future (within year 2300) level, while 0.9% represent severe hypercapnia. Tissue samples were collected at 3, 6 and 9 days after initiated CO2 exposure. Effects on the endocrine and biotransformation systems were examined by analyzing levels of sex steroid hormones (E2, T, 11-KT) and transcript expression of estrogen responsive genes (ERα, Vtg-α, Vtg-β, ZP2 and ZP3). In addition, transcripts for genes encoding xenobiotic metabolizing enzymes (cyp1a and cyp3a) and hypoxia-inducible factor (HIF-1α) were analyzed. Hypercapnia alone produced increased levels of sex steroid hormones (E2, T, 11-KT) with concomitant mRNA level increase of estrogen responsive genes, while PFOS produced weak and time-dependent effects on E2-inducible gene transcription. Combined PFOS and hypercapnia exposure produced increased effects on sex steroid levels as compared to hypercapnia alone, with transcript expression patterns that are indicative of time-dependent interactive effects. Exposure to hypercapnia singly or in combination with PFOS produced modulations of the biotransformation and hypoxic responses that were apparently concentration- and time-dependent. Loading plots of principal component analysis (PCA) produced a significant grouping of individual scores according to the exposure scenarios at day 6 and 9. Overall, the PCA analysis produced a unique clustering of variables that signifies a positive correlation between exposure to high PFOS concentration and mRNA expression of E2 responsive genes. Notably, this pattern was not evident for individuals exposed to PFOS concentrations in combination with elevated CO2 scenarios. To our knowledge, the present study is the first of its kind, to evaluate such effects using combined exposure to a perfluoroalkyl sulfonate and elevated levels of CO2 saturation, representative of future oceanic climate change, in any fish species or lower vertebrate. © 2014. This is the authors’ accepted and refereed manuscript to the article. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Two studies were performed to study the effect of different light intensities on melatonin secretory profiles in Atlantic cod ( Gadus morhua L.). In an indoor tank study, plasma melatonin profiles were measured over a 24-hour cycle in juvenile Atlantic cod reared under a 12 h light:12 h dark photoperiod, having either a high or low daytime light intensity (15.5 or 0.16 μE·cm − 2 ·s − 1 ). In a second study, plasma melatonin levels were measured in Atlantic cod kept in traps at three depths (4, 9 and 14 m) in a large sea cage following exposure to the following five experimental light regimes: (1) natural light (NL), (2) NL + artificial constant light (LL) at 2, 7 and 12 m depth, (3) NL + LL at 2 or 12 m, (4) NL + LL at 2 m and (5) NL + LL at 2 m together with additional surface shading. The vertical distribution of free swimming Atlantic cod in the same sea cage was monitored using hydroacoustics. In the tank experiment, diurnal plasma melatonin profiles were similar under low and high light intensity, remaining low during the light period, then increasing rapidly within 15–30 min of lights off, before peaking around midnight. In the sea cage experiment, fish under NL showed a similar diurnal rhythm in plasma melatonin levels, with high melatonin levels during the dark period, although at sunrise melatonin levels started to fall earlier in fish kept at 4 m depth compared to fish kept at 9 and 14 m. Overall, melatonin profiles were most effectively reduced, in terms of relative (day/night) plasma levels, in those fish sampled at the deepest depth (14 m). Relative plasma melatonin levels were correlated to the distance from the artificial light source and the intensity of the ambient light. Dispersed light (lamps at 2, 7 and 12 m) was the most effective light regime for inhibiting the nocturnal rise in plasma melatonin ratios in fish sampled at all three depths. Finally, exposure to the different light regimes did not influence the vertical distribution of Atlantic cod within the sea cage, which consistently remained close to the bottom of the cage.

Salted cod is a product highly appreciated by consumers, especially in Southern Europe and Latin America. In recent years there has been increasing consumer demand for products with low sodium content, and this has led the salting industry to seek new salt mixtures to help to reduce Na+ levels without producing alterations in the properties of the final product. In this study, Atlantic cod (Gadus morhua) was initially brined with various mixtures of salts based on NaCl, at various pH levels and including KCl, MgCl2 and/or CaCl2. After subsequent dry salting with NaCl, the Na+, K+, Ca2+ and Mg2+ cation contents were evaluated, and also their effect on water loss, salt uptake, entry of chloride, water holding capacity (WHC), water extractable protein (WEP) and hardness of the end product. A greater presence of K+ in muscle was associated with greater water loss, salt uptake and hardness of the dry salted product. Moreover, incorporation of Ca2+ and Mg2+ negatively affected water holding capacity. These changes were not dependent on brine pH and might significantly alter the acceptability of the final product. © 2013 Elsevier Ltd., This research was supported by the European Union under project FAIR-CRAFT CT 98-9109.

Biologically treated wastewater (WW) from the Hammerfest LNG (liquefied natural gas) plant is discharged to the sea. A study using biomarkers in mussels and Atlantic cod was performed to examine whether this discharge meets a zero harmful emission requirement. Caging of mussels close to the outfall and exposure of mussels and fish to WW in the laboratory were conducted, and a suite of contaminant responsive markers was assessed in exposed animals. In mussels the markers included chemical contaminant levels, haemocyte lysosomal instability and nucleus integrity, cellular energy allocation, digestive gland and gonad histopathology and shell-opening behaviour. In fish, biliary PAH metabolites and gill histopathology biomarkers were measured. A consistent cause-effect relationship between WW treatments and markers measured in test animals was not found. The results therefore indicate that the WW emission is unlikely to represent a significant stress factor for the local marine environment under the conditions studied.

In the Barents Sea, the limited data on biological relevant indicators and their responses to various anthropogenic stressors have hindered the development of a consistent scientific basis for selecting indicator species and developing practical procedures for environmental monitoring. Accordingly, the main aim of the present study was to develop a common set of baseline values for contaminants and biomarkers in three species, and to identify their strengths and limitations in monitoring of the Barents Sea. Blue mussel (Mytilus edulis), Icelandic scallop (Chlamys islandica) and Atlantic cod (Gadus morhua) were sampled from a north Norwegian fjord in March, June, September and December 2010. Digestive glands from the bivalve species and liver from Atlantic cod were analysed for biomarkers of oxidative stress (catalase [CAT], glutathione peroxidase [GPX], glutathione-S-transferase activities [GST], lipid peroxidation as thiobarbituric reactive substances [TBARS] and total oxyradical scavenging capacity [TOSC]), biotransformation (ethoxyresorufine-O-deethylase activity [EROD]) and general stress (lysosomal membrane stability [LMS]). Concentrations of polycyclic aromatic hydrocarbons (PAHs) and metals in the bivalves and PAH metabolites in fish bile were quantified. Finally, energy reserves (total lipids, proteins and carbohydrates) and electron transport system (ETS) activity in the digestive gland of the bivalves and liver of Atlantic cod provided background information for reproductive cycle and general physiological status of the organisms. Blue mussel and Icelandic scallop showed very similar trends in biological cycle, biomarker expression and seasonality. Biomarker baselines in Atlantic cod showed weaker seasonal variability. However, important biological events may have been undetected due to the large time intervals between sampling occasions. Physiological biomarkers such as energy reserves and ETS activity were recommended as complementary parameters to the commonly used stress biomarkers, as they provided valuable information on the physiological status of the studied organisms. Interpretation of the seasonality in oxidative stress biomarkers was in general difficult but TOSC and lipid peroxidation were preferred over the antioxidant enzyme activities. This study is the first reporting seasonal baseline in these three species in a sub-Arctic location. Overall, the Icelandic scallop was considered the most adequate organism for environmental monitoring in the Barents Sea due to the interpretability of the biomarker data as well as its abundance, ease to handle and wide distribution from the southern Barents Sea to Svalbard. Fil: Nahrgang, J.. FRAM Centre. Akvaplan-niva; Noruega Fil: Brooks, S. J.. Norwegian Institute for Water Research; Noruega Fil: Evenset, A.. FRAM Centre. Akvaplan-niva; Noruega Fil: Camus, L.. FRAM Centre. Akvaplan-niva; Noruega. University Centre In Svalbard; Noruega Fil: Jonsson, M.. FRAM Centre. Akvaplan-niva; Noruega Fil: Smith, T. J.. FRAM Centre. Akvaplan-niva; Noruega Fil: Lukina, J.. FRAM Centre. Akvaplan-niva; Noruega. University of Tromsø. Faculty of Biosciences, Fisheries and Economics. Department of Arctic and Marine Biosciences; Noruega Fil: Frantzen, M.. FRAM Centre. Akvaplan-niva; Noruega Fil: Giarratano, Erica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Renaud, P. E.. FRAM Centre. Akvaplan-niva; Noruega. University Centre In Svalbard; Noruega

Sexual maturation of Atlantic cod, Gadus morhua, is a major problem during commercial on growing as fish divert energy away from growth into gonadal development. While the photoperiod regimes that inhibit maturation are well described, when manipulations are applied in a commercial cage setting, using standard lighting technology, maturation is not completely inhibited. This has led to the hypothesis that the enhanced light sensitivity of cod allows it to perceive ambient illumination over the artificial lighting. A 13 month trial was conducted to determine the effectiveness of net shading ambient photoperiod in addition to constant lighting to suppress maturation of cod in outdoor conditions. By reducing the relative difference between day and night light intensities, it was hypothesised that maturation in cod could be inhibited as fish could not perceive, and thus use the ‘ambient daylength' signal to entrain their reproductive cycle. Two outdoor tanks were covered in either a low density (70% reduction in ambient illumination) or a high density (90% reduction in ambient illumination) shade netting and then illuminated continuously by cathode lighting. These were compared to two indoor tanks in which ambient light was excluded and instead they were illuminated by similar lighting running either under a simulated natural photoperiod or continuous illumination. The work demonstrated that the shade netting could improve the relative performance of the artificial lighting outdoors fromless than2% in a non-shaded system to 6.6% (low shade treatment) and 31.3% (high shade treatment) of the day light intensity. Importantly, both shading treatments were effective at suppressing sexual development as confirmed through histology and reduced GSI (female mean ≤ 2.18%, male mean ≤ 1.39%), oocyte diameter (meanless than400 μm) and sex steroid profiles (female 17β-estradiol mean ≤ 0.24 ng.ml- 1, male 11-ketotestosterone mean ≤ 3.35 ng.ml- 1) as well as enhanced growth. These results are a promising demonstration of the potential value of shading systems to enhance the efficacy of photoperiod control.

Journal homepage: http://www.elsevier.com/wps/find/journaldescription.cws_home/503309/description#description The (physical) ‘disector method’, a frequently cited stereological technique, has so far received little attention within fish fecundity studies, although it can be used to provide unbiased, assumption-free data on levels of atresia (resorption of vitellogenic oocytes). In comparison, traditional simple counting to estimate the numerical ratio of normal to atretic cells is biased because the smaller atretic cells have a lower chance of being transected in histological sections. These problems are circumvented by the disector method as it operates in three dimensions, i.e., uses consecutive pairs of slides. However, the high labour costs involved prevent regular usage of this method in population studies where large numbers of ovarian samples are processed. In the present paper we assess the corresponding bias of the traditional profile method, analysing developing ovaries of Atlantic cod (Gadus morhua) and herring (Clupea harengus), i.e., in a relatively broad and narrow oocyte frequency situation, respectively. A highly significant but non-linear relationship (r2 = 0.975, P < 0.001, df = 154) was found between the relative intensity of atretic vitellogenic oocytes (ARI) estimated by the disector and profile method. Both species fitted well to this polynomial model. The degree of underestimation of atretic oocytes still containing yolk (i.e., the alpha stage) was at maximum (11.6%) at intermediate levels (ARI = 50% (disector)) but, logically, no such bias existed at the extreme ends (ARI: 0% and 100% (disector)). The practical use of this simple, fast approach designated the stereo-profile method, including the additional use of image analysis for further refinements, is successfully demonstrated on field samples.

Journal homepage: http://www.elsevier.com/wps/find/journaldescription.cws_home/503309/description#description In this paper we report on the fate of vitellogenic follicles (VF) as either alpha atretic follicles (αF) or post-ovulatory follicles (POFs) using histology and captive Atlantic cod (Gadus morhua) in three experiments. In Experiment 1 the production and persistence of αF was determined by taking repeated biopsy samples from tagged females held in temperature regimes (mean ± SD) controlled at 4.5 (0.3) and 8.1 (0.3) °C. The αF lasted (mean ± 2 SE, n) 5.3 days (2.5, 8) and 9.7 days (4.9, 8) in the warmer and cooler water respectively and the combined average was 7.5 days (2.9, 16). In Experiment 2 we took biopsy samples at intervals and monitored egg production from individual females accompanied by a male and used the stage of egg development to age POFs found in the biopsy samples. The females, some immature, were killed at intervals, up to 45 days post-spawning, and then the biopsy and ovary samples were stained by periodic acid Schiffs’ reagent to prepare descriptions of POFs aged from 11 h to 45 days old. Spent female ovaries contained POFs, and a thicker ovarian wall (tunica) exceeding 0.34 mm whilst immature fish lacked POFs and their ovary tunica was thinner (less than 0.15 mm). In Experiment 3 the persistence of POFs was monitored in a simulated North Sea (10–16.1 °C) and Barents Sea (7.5–11.2 °C) regime using ovary sections stained by periodic acid Schiffs’ reagent. In both regimes the POFs regressed at a temperature sensitive rate during the experiment lasting 104 days. Some αF from large VF persisted longer than expected (more than 4 months after spawning) and were called cysts based on their appearance and greater expected lifetime. These histological characteristics were successfully applied to assess maturity of wild cod caught on surveys in the North and Barents Seas after an assumed 150 and 310 days, respectively, after the spawning season. Taken together this article presents reliable figures on the lifetime of atretic and post-ovulatory follicles as well as variation in ovarian thickness with spawning experience, which will be most useful input in the further work to assess reproductive potential.