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Catch-and-release (CR N = 11) were caught on angling gear using commonly used fishing lures, and tagged with both pop-up satellite archival tags (PSATs) and acoustic transmitters. Survival was determined by the vertical migration patterns of individuals measured by the tags during individual monitoring periods ranging from 3 to 248 days (median 80 days) after the C&R event. No short-term mortality was observed post release. In terms of long-term survival, eight halibut were confirmed to have survived the monitoring periods while one halibut had insufficient data. For the other two individuals, the acoustic transmitters showed a cessation of vertical movement after 38 and 44 days, which could neither be verified nor disproven by the PSAT recordings (due to earlier detachment and tag malfunction of the PSATs). Since premature tag shedding was frequent in this study, it cannot be concluded if the cessation of vertical movement was because of tag shedding or delayed mortality. The results of this study indicate that Atlantic halibut is resilient to C&R angling, and that C&R of Atlantic halibut may be an effective management strategy to reduce fishing-induced mortality. However, the effects of severe hooking injuries, impacts on smaller individuals, and potential sublethal consequences of C&R were not covered in this study, and are still poorly understood. To minimize negative impacts of C&R and to promote fish welfare, fisheries managers are encouraged to implement best practice C&R angling guidelines for Atlantic halibut.

The fishery for Atlantic Halibut Hippoglossus hippoglossus in the Gulf of St. Lawrence (Gulf) is currently experiencing its highest landings since the 1950s. However, the absence of information on adult habitat use has limited the development of new survey methodologies. The aim of this study was to use pop-up satellite archival tags on large (≥108-cm) halibut in the Gulf to provide data on seasonal temperature associations, depth distributions, and migrations. Twenty Atlantic Halibut were tagged in 2013 and 15 were tagged in 2015 at two different locations in the northern Gulf. Atlantic Halibut overwintered in the central and northern Gulf based on six tag pop-offs. In the winter in both studies, halibut were distributed at 160–440 m depth with a narrow temperature association of 5.5–6.5°C, which corresponded with the bathymetry and hydrography of the Gulf rather than the deeper and colder waters of the continental shelf where the southern stock occurs. Spawning rises were identified from the dep...

Ocean acidification and rising seawater temperature are environmental stressors resulting from the continuous increase of the atmospheric CO2 concentration due to anthropogenic activities. As a consequence, marine fish are expected to undergo conditions outside of their tolerance range, leading to physiological challenges with possible detrimental implications. Our research group has previously shown that exposure to elevated CO2 modulated the immune system of the Atlantic halibut. To further investigate this finding, we analysed non-specific immune components in blood plasma of Atlantic halibut (Hippoglossus hippoglossus) juveniles acclimated to six different temperatures (5, 10, 12, 14, 16 and 18 °C), and to water pH of 8.0 (control) or 7.6 (predicted for year 2100) for three months. Plasma ions (K+, Na+, Ca++, Cl-) and lactate concentrations were also measured. The analysis of plasma ions did not show any trends related to temperature or CO2 exposure, and the majority of the experimental fish were able to maintain ionic balance. The results show that both innate immune components (lysozyme and alternative complement system) had increased activities in response to elevated CO2, representing a CO2-related impact on the halibut's immune system. The increased activity of lysozyme and complement system is possibly part of the acclimatization process, and might be protective.

Amoebic gill disease (AGD) is one of the most significant infectious diseases affecting marine farmed Atlantic salmon and is caused by the marine amoeba Neoparamoeba perurans. Atlantic halibut are also farmed in Norway, Canada, Chile and Scotland; however, the total production is approximately 0.1 per cent that of salmon. Halibut reared in a net pen sea site in Scotland presented with low-level mortalities and pale, raised patches on the gills. Fresh microscopy of the gills demonstrated amoeboid organisms and histology of the gills confirmed typical AGD pathology. Gill samples tested by PCR confirmed the presence of N perurans. Freshwater baths of three hours duration are the preferred treatment for AGD in salmon; however, hydrogen peroxide has also been used and as halibut do not tolerate freshwater low-level hydrogen peroxide baths (1000 mg/l) were administered as a 15-minute bath. Net changes were also undertaken, and mortalities subsequently reduced.

Oceans are warming and pH levels are decreasing as a consequence of increasing levels of dissolved CO2concentrations. The CO2emissions are predicted to be produce in greater and faster changes in the ocean than any other event in geological and historical records over the past 300 million years. Marine organisms will need to respond to multiple stressors but the potential consequences of global change-related effects in fish are not fully understood. Since fish are affected by many biotic and abiotic environmental variables, including temperature and CO2fluctuations, it is critical to investigate how these variables may affect physiological and biochemical processes. We investigated the effects of elevated CO2levels (pH of 8.0, which served as a control, or 7.6, which is predicted for the year 2100) combined with exposure to different temperatures (5, 10, 12, 14, 16, and 18 °C) in the Atlantic halibut (Hippoglossus hippoglossus) during a three month experiment. We assessed effects on antioxidant and cholinesterase enzymes (AChE and BChE), and CYP1A enzyme activities (EROD). The treatments resulted in oxidative stress, and damage was evident in the form of protein carbonyls which were consistently higher in the elevated CO2-treated fish at all temperatures. Analyses of antioxidant enzymes did not show the same results, suggesting that the exposure to elevated CO2increased ROS formation but not defences. The antioxidant defence system was insufficient, and the resulting oxidative damage could impact physiological function of the halibut on a cellular level.

With growing world trends in the consumption of raw and undercooked aquatic products, anisakiasis, resulting from infection by anisakid nematodes, currently affects over 2000 people per annum worldwide. In response to new EC regulatory requirements regarding the processing of farmed fish to reduce the risk of nematode infections, the aim of this study was to provide evidence of the prevalence and intensity of anisakids in relevant Scottish mariculture species and to identify potential probability of nematode infection by analysing the current farming practices for these species. A sample of 225 marine rainbow trout, Oncorhynchus mykiss , and 150 Atlantic halibut, Hippoglossus hippoglossus , was obtained from three and two farms, respectively, on the West Coast of Scotland. A further 12 Atlantic halibut were obtained from wild fisheries. Fish flesh examined for nematode larvae using standard techniques provided no evidence for the presence of anisakid nematodes in any of the farmed fish sampled. In addition, no food items other than pelleted feed were found in the stomach and intestines of any farmed fish. Sampled wild halibut showed a prevalence of 75% and intensity of 12.75 ± 25.81 of Anisakis simplex although no Pseudoterranova decipiens were found. An analysis of current farm practices for the culture of halibut, rainbow trout and sea trout, Salmo trutta , in Scotland suggests that the probability of infection with anisakids is extremely low. To acquire an infection, a fish must consume infected prey, and as commercial aquaculture in Scotland relies on processed, pelleted feed, the probability of wild infected prey being consumed is very low, particularly since fish are generally fed to satiation. Given the results of this study and evidence from previous studies, it must be concluded that under current farming practices, the risk of contracting anisakiasis from Scottish farmed halibut and rainbow trout is extremely low to negligible. Consequently, they do not pose a significant risk to consumers in terms of the ingestion of these parasites.

Summary The ontogenic development of neurosensory structures in larval Atlantic halibut, Hippoglossus hippoglossus (L.) was examined using microscopy imaging techniques and analysis. Larval samples were preserved at developmental stages of 444, 486, 528, 570, 612, and 666 degree-days, respectively. Larvae were measured and photographed macroscopically. The fish were then embedded in paraffin for histological processing. 5 μm sequential sections of the anterior of the larvae were cut and stained using hematoxylin and eosin dyes. The resulting sections were examined using an Olympus BX60 compound microscope. The development of neurosensory structures such as neuromasts and sensory papillae were observed throughout all developmental stages of larvae and early development of the lateral line was observed at 666 degree-days. Neuromast frequency increased as larvae matured, suggesting that larvae were approaching their first feeding event towards the end of the sampling period. Possible implications of development on larval first feeding are discussed.

Halibut (Hippoglossus hippoglossus) and shrimps (Pandalus borealis) are regular foodstuffs for communities in northern Norway and important species for the coastal fishing industry. This is the first study to present a comprehensive overview of the contaminant status of these species, with emphasis on unregulated perfluoroalkylated substances (PFAS). The contaminant concentrations were low and within tolerable levels for human dietary exposure. Median Σpolychlorinated biphenyls (PCB) were 4.9 and 2.5 ng/g ww for halibut and unpeeled shrimps, respectively. Concentrations of perfluorooctane sulfonate (PFOS) – the most abundant PFASs – were 0.9 and 2.7 ng/g ww in halibut and shrimp, respectively. The halibut fillets were dominated by PCBs, which contributed to 50% of the total POPs load, followed by ΣDDTs; 26% and PFASs (18%), whereas shrimps were dominated by PFASs (74%). ΣPBDEs (polybrominated diphenyl ethers) contributed to 1–4% of the total POP load. Local sources are not contributing significantly to the contaminant burden in these species.

CO2 emissions from human activities are increasing, resulting in greater rates of change in the oceans, exceeding any other event in geological and historical records over the past 300 million years. Oceans are warming and pH levels are decreasing. Marine organisms will need to respond to multiple stressors and the potential consequences of global change-related effects in fish needs to be investigated. Fish are affected by many biotic and abiotic environmental variables, including temperature and CO2 fluctuations, and it is therefore critical to investigate how these variables may affect physiological and biochemical processes. We investigated the effects of elevated CO2 levels (pH of 8.0, which served as a control, or 7.6, which is predicted for the year 2100) combined with exposure to different temperatures (5, 10, 12, 14, 16, and 18 °C) in the Atlantic halibut (Hippoglossus hippoglossus) during a three month experiment. Since regulation of reactive oxygen species (ROS) is crucial for physiological processes the focus was on the antioxidant defense system and we assessed the effects on catalytic activities of antioxidant enzymes (SOD, CAT, GR, GST, GPx). In addition we also analyzed effects on cholinesterase enzymes (AChE and BChE), and CYP1A enzyme activities (EROD). The treatments resulted in oxidative stress, and damage was evident in the form of protein carbonyls which were consistently higher in the elevated CO2-treated fish at all temperatures. Analyses of antioxidant enzymes did not show the same results, suggesting that the exposure to elevated CO2 increased ROS formation but not defences. The antioxidant defense system was insufficient, and the resulting oxidative damage could impact physiological function of the halibut on a cellular level.

Hormones and neuropeptides play a crucial role in the appetite control system of vertebrates, yet few studies have focused on their importance during early teleost development. In this study, we analysed the expression patterns of the appetite-controlling factors ghrelin, neuropeptide Y (NPY), peptide YY (PYY), pro-opiomelanocortin (POMC-C), and cocaine-amphetamine-related transcript (CART) by quantitative PCR. Transcript expression was investigated in response to feeding in developing Atlantic halibut larvae: before (premetamorphic stage 5) and during metamorphosis (stages 8 and 9B), and also in response to a fast–refeed challenge. We show that ghrelin transcript expression increased in synchrony with stomach development, while CART was significantly reduced during larval development. PYY was up-regulated 1 and 3 h after feeding in stage 5. Transcript abundance of other appetite-controlling factors did not change in response to feeding. Fasting–refeeding trials (majority of larvae in metamorphosing stage 7) revealed a down-regulation of POMC-C 30 min after refeeding, while ghrelin, PYY and NPY transcript expression increased 2, 4 and 5 h after refeeding, respectively. In summary, transcripts for key appetite-controlling factors were detected early during development in Atlantic halibut and their emergence was not correlated with metamorphosis, with the exception of ghrelin. Our results suggest that PYY may mediate satiety early in larval development. The differing response times of POMC-C, ghrelin, PYY and NPY to a meal are intriguing and require further exploration to understand the role of each player in appetite control.

To investigate the illuminance requirements for the culture of red algae in finfish effluent, both Chondrus crispus and Palmaria palmata were assessed simultaneously at three irradiances. Apical tips, 3.5 cm length, were stocked at 2 g L−1 in 1-L glass flasks with enriched seawater in two 24-day experiments, at 10 and 14 °C, respectively. Palmaria grew up to 70 % better and up took more nutrients than Chondrus under five of the six experimental conditions, except at 14 °C and low irradiance (daily photon dose of 3.4 mol photon m−2 day−1). Specific growth rate of both species at high irradiance, 13.1 and 17.2 mol photon m−2 day−1, at each trial, 10 and 14 °C, respectively, was 40 and 20 % better than at medium irradiance, but nutrient uptake was similar at both medium and high irradiance. Chondrus growth rate was higher during Experiment 2 (14 °C and 17.2 mol photon m−2 day−1) than during Experiment 1 (10 °C and 13.1 mol photon m−2 day−1), while Palmaria growth rate was similar in both trials, but always significantly higher than Chondrus. In the range 10–14 °C, Palmaria is the best candidate for integration with Atlantic halibut juveniles (Hippoglossus hippoglossus).

Filamentous black yeasts from the genus Exophiala are ubiquitous, opportunistic pathogens causing both superficial and systemic mycoses in warm- and cold-blooded animals. Infections by black yeasts have been reported relatively frequently in a variety of captive and farmed freshwater and marine fishes. In November 2012, moribund and recently dead, farm-raised Atlantic Halibut Hippoglossus hippoglossus were necropsied to determine the cause of death. Histopathology revealed that three of seven fish were affected by a combination of an ascending trans-ductual granulomatous mycotic nephritis, necrotizing histiocytic encephalitis, and in one fish the addition of a fibrogranulomatous submucosal branchitis. Microbial cultures of kidney using selective mycotic media revealed pure growth of a black-pigmenting septated agent. Application of molecular and phenotypic taxonomy methodologies determined that all three isolates were genetically consistent with Exophiala angulospora. This is the first report of E. angulospora as the causal agent of systemic mycosis in Atlantic Halibut.

Wild goldsinny wrasse Ctenolabrus rupestris, corkwing wrasse Symphodus melops and ballan wrasse Labrus bergylta were collected at 8 sampling sites in Sweden and Norway during summer 2014. Brain tissue from 466 wrasses were analyzed for nervous necrosis virus (NNV) infections by real-time RT-PCR, and positive samples were subjected to sequencing and phylogenetic analysis of partial segments of the RNA2 and RNA1 genes. This study shows that NNV is present in wild ballan, corkwing and goldsinny wrasse along the coastline of Sweden and Norway. The overall prevalence in the sampled labrids was 6.7%. Prevalence was 6.4% in goldsinny, 6.3% in corkwing and 18% in ballan wrasse. The wrasse RNA2 NNV sequences revealed high genetic variability and were divided into 3 clusters within the cold water barfin flounder NNV (BFNNV) and warm water cluster red-spotted grouper NNV (RGNNV) genogroups. Within the BFNNV genogroup, wrasse NNVs clustered in 2 sub-genogroups, with grey mullet NNV (GMNNV) and with Atlantic halibut NNV (AHNNV). These groups were previously dominated by virus originating from Atlantic cod Gadus morhua and Atlantic halibut Hippoglossus hippoglossus from the northeast Atlantic. The presence of NNV in wild wrasse and the surprising high genetic variability observed in this study should be considered before moving wild-caught wrasse between geographically distant sites. The results show that use of wild-caught wrasse as brood fish in wrasse farming represents a risk of introducing NNV into aquaculture.

To establish if the developmental changes in the primary barrier and osmoregulatory capacity of Atlantic halibut skin are modified during metamorphosis, histological, histochemical, gene expression and electrophysiological measurements were made. The morphology of the ocular and abocular skin started to diverge during the metamorphic climax and ocular skin appeared thicker and more stratified. Neutral mucins were the main glycoproteins produced by the goblet cells in skin during metamorphosis. Moreover, the number of goblet cells producing neutral mucins increased during metamorphosis and asymmetry in their abundance was observed between ocular and abocular skin. The increase in goblet cell number and their asymmetric abundance in skin was concomitant with the period that thyroid hormones (THs) increase and suggests that they may be under the control of these hormones. Several mucin transcripts were identified in metamorphosing halibut transcriptomes and Muc18 and Muc5AC were characteristic of the body skin. Na+, K+-ATPase positive (NKA) cells were observed in skin of all metamorphic stages but their number significantly decreased with the onset of metamorphosis. No asymmetry was observed between ocular and abocular skin in NKA cells. The morphological changes observed were linked to modified skin barrier function as revealed by modifications in its electrophysiological properties. However, the maturation of the skin functional characteristics preceded structural maturation and occurred at stage 8 prior to the metamorphic climax. Treatment of Atlantic halibut with the THs disrupter methimazole (MMI) affected the number of goblet cells producing neutral mucins and the NKA cells. The present study reveals that the asymmetric development of the skin in Atlantic halibut is TH sensitive and is associated with metamorphosis and that this barrier’s functional properties mature earlier and are independent of metamorphosis.

In annual surveys conducted during the period 2012–2015, concentrations of the toxic or essential elements B, Se, Cd, Sn, Cs, Hg, Pb, Al, Cr, Mn, Fe, Ni, Cu, Zn, and As were analyzed in brown meat of edible crab (Cancer pagurus), and filets of cod (Gadus morhua) and halibut (Hippoglossus hippoglossus) in one of the most important commercial crab fishing areas in Norway, at Mausund in Frøya municipality in Sør-Trøndelag, Norway. Concentrations of the elements were analyzed in sediments in 2015. Several salmon farms are located in this area. Samples were extracted by HNO3 and analyzed using Inductively coupled plasma mass spectroscopy (ICP-MS). Crab, cod, and halibut were caught in a total of five locations. One of these locations was in the proximity of a salmon farm. In edible crabs, the mean ranks were significantly different between two locations only for Sn (p= 0.034). When all data were pooled, the mean ranks statistics showed significant difference between all years for the elements Se (p=

As the worldwide exploitation rate of capture fisheries continues, the development of sustainable aquaculture practices is increasing to meet the seafood needs of the growing world population. The demand for aquatic products was historically satisfied firstly by an effort to expand wild catch and secondly by increasing land-based and near-shore aquaculture. However, stagnation in wild catch as well as environmental and societal challenges of land-based and near-shore aquaculture have greatly promoted efforts to development farming offshore technologies for harsh, high energetic environments. This contribution thus highlights recent technological approaches based on three sample sites which reach out from sheltered near-shore aquaculture sites to sites with harsh wave/current conditions. It compares and evaluates existing technological approaches based on a broad literature review; on this basis, we then strongly advocate for presently available aquaculture technologies to merge with future offshore structures and platforms and to unveil its added value through synergetic multi-use concepts. The first example describes the recent development of longline farming in offshore waters of New Zealand. New Zealand has designated over 10,000 ha of permitted open ocean water space for shellfish farming. The farms range from 8 to 20 km out to sea and a depth of 35-80 m of water. Research has been ongoing for the last 10 years and the first commercial efforts are now developing in the Bay of Plenty. New methods are being developed which should increase efficiency and reduce maintenance with a particular focus on Greenshell mussel (Perna canaliculus) and the Pacific Oyster (Crassostrea gigas), Flat Oyster (Tiostrea chilensis) and various seaweeds. The second case study involves a long-term, open ocean aquaculture (OOA) research project conducted by the University of New Hampshire. During the course of approximately 10 years, the technological aspects of OOA farming were conducted with submersible cages and longlines, surface feeding systems and real time environmental telemetry. The grow-out potential of multiple marine species such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), halibut (Hippoglossus hippoglossus), blue mussel (Mytilus edulis), sea scallop (Placopecten magellanicus) and steelhead trout (Oncorhynchus mykiss) were investigated at a site 12 km from shore. The last study presents a multi-use aspect of aquaculture for an open ocean site with fish cages attached to existing offshore wind energy foundations. Technological components such as mounting forces and scour tendencies of two different cage structures (cylindrical and spherical) were investigated by means of hydraulic scale modeling. The cages were pre-designed on the basis of linear theory and existing standards and subsequently exposed to some realistic offshore wave conditions. The wind farm "Veja Mate" in German waters with 80 planned 5 MW turbines anchored to the ground by tripiles is taken as the basis for the tested wave conditions. Based on findings stemming from the three example approaches conclusions are drawn and future research demand is reported.

The complexity of the nonvisual photoreception systems in teleosts has just started to be appreciated, with colocalization of multiple photoreceptor types with unresolved functions. Here we describe an intricate expression pattern of melanopsins in early life stages of the marine flat fish Atlantic halibut (Hippoglossus hippoglossus), a period when the unpigmented brain is directly exposed to environmental photons. We show a refined and extensive expression of melanopsins in the halibut brain already at the time of hatching, long before the eyes are functional. We detect melanopsin in the habenula, suprachiasmatic nucleus, dorsal thalamus, and lateral tubular nucleus of first feeding larvae, suggesting conserved functions of the melanopsins in marine teleosts. The complex expression of melanopsins already at larval stages indicates the importance of nonvisual photoreception early in development. Most strikingly, we detect expression of both exorhodopsin and melanopsin in the pineal complex of halibut larvae. Double-fluorescence labeling showed that two clusters of melanopsin-positive cells are located lateral to the central rosette of exorhodopsin-positive cells. The localization of different photopigments in the pineal complex suggests that two parallel photoreceptor systems may be active. Furthermore, the dispersed melanopsin-positive cells in the spinal cord of halibut larvae at the time of hatching may be primary sensory cells or interneurons representing the first example of dispersed high-order photoreceptor cells. The appearance of nonvisual opsins early in the development of halibut provides an alternative model for studying the evolution and functional significance of nonvisual opsins. J. Comp. Neurol. 522:4003–4022, 2014. © 2014 Wiley Periodicals, Inc.

One of the main problems facing Atlantic halibut hatcheries is the high mortality in the early stages of larval development. Several factors could be involved, for example: water quality, diseases or abnormalities, such as deformities occurring in the yolk sac larvae prior to exogenous feeding. The aim of this study was to identify differences in bacterial flora associated with yolk sac larvae with oral deformity. We also aimed to establish whether there is any relationship between bacterial strains and the "gaping jaws" syndrome. During our study, 74 bacterial isolates were obtained using three different nutrient media: Marine Agar, R2A and TCBS. Some of these bacteria were characterized using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) and 16S rRNA sequencing. The immune response in larvae exhibiting the "gaping jaws" condition was measured by real time PCR. Our results showed significant differences in bacterial flora between normal and gaping larvae. The gaping yolk sac larvae were predominantly colonized by members of the families Vibrionaceae and Flavobacteriaceae. Bacteria belonging to the Bacillus and Pseudoalteromonas genera were also present but less frequent. It was not possible to associate a type or group of bacteria directly related to "gaping". Strikingly, larvae with gaping jaws had an increase in the expression of two immune related genes, like hepcidin and chemokine (MIP-1s). These results indicate activation of the immune response in larvae with "gaping jaws" syndrome and this response could be related to bacteria isolated from gaping condition.

As a consequence of increasing atmospheric CO2, the world's oceans are becoming warmer and more acidic. Whilst the ecological effects of these changes are poorly understood, it has been suggested that fish performance including growth will be reduced mainly as a result of limitations in oxygen transport capacity. Contrary to the predictions given by the oxygen- and capacity-limited thermal tolerance hypothesis, we show that aerobic scope and cardiac performance of Atlantic halibut (Hippoglossus hippoglossus) increase following 14–16 weeks exposure to elevated temperatures and even more so in combination with CO2-acidified seawater. However, the increase does not translate into improved growth, demonstrating that oxygen uptake is not the limiting factor for growth performance at high temperatures. Instead, long-term exposure to CO2-acidified seawater reduces growth at temperatures that are frequently encountered by this species in nature, indicating that elevated atmospheric CO2 levels may have serious implications on fish populations in the future.

GRIM-19 (gene associated with retinoid-interferon-induced mortality 19), a novel cell death regulatory gene, plays important roles in cell apoptosis, embryogenesis, mitochondrial respiratory chain and immune response. To date, little information is known about fish GRIM-19 characteristics except orange-spotted grouper (Epinephelus coioides). Here a new GRIM-19 gene is identified and characterized from turbot (Scophthalmus maximus), an economic marine fish in China and Europe. Briefly, turbot GRIM-19 is a 595-bp gene encoding a 144 amino acids protein, which shares the closest relationship with Atlantic halibut (Hippoglossus hippoglossus). The expression of turbot grim-19 in liver, spleen and kidney is up-regulated by the infection of Vibrio anguillarum and LCDV (lymphocystis disease virus). Subsequently, a recombinant protein of turbot GRIM-19 is acquired and the anti-bacterial function is proved by liquid culture inhibition experiment. The subcellular location indicates that turbot GRIM-19 is co-localized with STAT3 in the cytoplasm, which is mainly determined by GRIM-19 41-84 amino acids and STAT3 1-321 amino acids. Finally, the involvements of turbot GRIM-19 in cell apoptosis and NF-κB pathway are investigated. All these data help to understand GRIM-19 function in fish, as well as provide the application possibility of GRIM-19 in fish disease resistance breeding.

Large Atlantic halibut (Hippoglossus hippoglossus) off the eastern coast of Canada were tagged with pop-up satellite archival transmission tags (N = 17) to track movements, determine ambient depth and temperature, and infer spawning activity. Many halibut showed seasonal movements from deepwater slope areas in fall and winter to shallower feeding grounds on the Scotian Shelf and Grand Banks in summer. Halibut depths ranged between 0 and 1,640 m. Mean temperature of occupation was 4.7 °C. Multiple short-term vertical ascents from a consistent baseline depth, characterized as spawning rises, were identified in seven of the tagged halibut south of the Grand Banks. All presumed spawning rises occurred in multiples of 2–6 events at 2- to 9-day intervals between October and January, spanning an average vertical extent of 50–100 m at depths of about 800–1,000 m. Given the direction and velocity of the slope water currents and the duration of the pelagic stage, the calculated 300–500 km drift of the eggs and larvae would take them onto the Scotian Shelf, as well as into the Gulf of St. Lawrence. Therefore, the location of the presumed spawning grounds is consistent with expectations based on migration compensation theory, the northeasterly migratory patterns of the juveniles, the relatively static distribution of the adults off southern Newfoundland, and the prevailing currents at depth.

Atlantic halibut (Hippoglossus hippoglossus) in a Norwegian fjord were tagged with pop-up archival transmitting (PAT) tags to investigate whether they join offshore spawning events with halibut from other regions. All fish (n = 4) remained in the fjord throughout the spawning season, suggesting that they may be reproductively segregated from other stocks.

Although the Atlantic halibut (Hippoglossus hippoglossus) is an important commercial species, there is still a deficit with regard to the number of transcripts in the databases, which can be accessed and exploited for targeted candidate gene and pathway studies. In this study, the RNAs from head, skin and GI tract from different developmental stages were sequenced to generate 22,272 contigs of 500 base pairs or greater as a molecular resource for this species.

This study examines the crystal-liquid crystal phase transitions of the major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), from muscle tissue of marine fish living at temperatures of 0–4.1°C (the Pacific cod Gadus macrocephalus, banded Irish lord Hemilepidotus gilberti, Pacific halibut Hippoglossus hippoglossus, black edged sculpin Gymnocanthus herzensteini, dark colored flounder Pleuronectes obscurus, and plain sculpin Myoxocephalus jaok), as well as of fish living at 14 and 18°C (Pacific redfin Tribolodon brandti). The PC and PE phase-transition thermograms of all the investigated species displayed specific profiles. The largest share of the thermogram area at temperatures higher than those of the habitat was found for the PC (28–40%) and PE (47–82%) of the black-edged sculpin, dark-colored flounder, and the plain sculpin, which have reduced physiological activity at low temperatures. In the Pacific cod, banded Irish lord, and the Pacific redfin, this parameter was much lower, 0–18% (PC) and 0–39% (PE). The thermotropic behavior PC and PE was symbate in all fish, except for the cod and the plain sculpin. The transition enthalpy of PC in all the investigated species was 2.8 times higher than that of PE. To interpret the varied PC and PE thermogram profiles of fish with similar fatty-acid compositions, the data on the composition of the molecular species of these phospholipids appeared to be the most informative. This study suggests that each fish species has its own strategy for thermal adaptation, which is realized through a certain set of phospholipid molecular species.

Fishing mortality and natural mortality rates for Atlantic Halibut Hippoglossus hippoglossus on the Scotian Shelf and southern Grand Banks were estimated from a multiyear tagging study. Models that were used to estimate mortality rates incorporated tag loss. Between 2006 and 2008, 1,913 Atlantic Halibut were double-tagged with t-bar anchor tags; as of 26 August 2010, 368 of these fish had been recaptured. We estimated instantaneous fishing mortality (F) separately for each cohort in the first year (on average, 6 months) after release to allow newly tagged animals to mix with the population. A two-parameter model was used to describe tag loss. Tag loss was estimated at 13% per year in the first year and 10% per year in the second and subsequent years. Using the multiyear model with incomplete mixing and assuming 90% tag reporting and 80% survival from tagging, average instantaneous natural mortality (M) of Atlantic Halibut was estimated to be 0.22 and F was estimated to be 0.15 in 2007, 0.24 in 20...

Variation in oocyte quality affects sustainability of finfish aquaculture products including Atlantic halibut (Hippoglossus hippoglossus L.). To have an insight into role of major egg yolk constituents in the oocyte quality, egg fatty acid (FA), amino acid (AA) and folate contents were related to normal blastomere symmetry, and fertilization and hatching success. Significant correlations were found between dihomo-c-linolenic acid (DGLA, 20:3n6), palmitic acid (PA, 16:00) and docosapentaenoic acid (DPA, 22:5n3), and normal blastomere symmetry and survival success. Egg concentrations of myristic acid (MA, 14:0), oleic acid (OA, 18:1n9), stearidonic acid (SA, 18:4n3) and eicosadienoic acid (EDA, 20:2n6) explained 56 % variation in fertilization success. OA and EDA explained 70 % of variation in blastomere symmetry. Palmitoleic acid (POA, 16:1n7) and linolenic acid (LNA, 18:3n3) concentrations explained 57% of variation in hatching success. Egg valine concentrations correlated with fertilization rates, and aspartic acid and leucine correlated with normal blastomere symmetry. Alanine and valine concentrations explained together 45% of variation in fertilization. Glutamic acid and tyrosine concentrations explained 68% of variation in normal blastomere symmetry while serine, arginine and valine explained 36% of variation in hatching. These FAs and AAa may be potential indicators of oocyte quality in Atlantic halibut.

In the early 1990s, the Northwest Atlantic Ocean underwent a fisheries‐driven ecosystem shift. Today, the iconic cod (Gadus morhua) remains at low levels, while Atlantic halibut (Hippoglossus hippoglossus) has been increasing since the mid‐2000s, concomitant with increasing interest from the fishing industry. Currently, our knowledge about halibut ecology is limited, and the lack of recovery in other collapsed groundfish populations has highlighted the danger of overfishing local concentrations. Here, we apply a Bayesian hierarchical spatiotemporal approach to model the spatial structure of juvenile Atlantic halibut over 36 years and three fisheries management regimes using three model parameters to characterize the resulting spatiotemporal abundance structure: persistence (similarity of spatial structure over time), connectivity (coherence of temporal pattern over space), and spatial variance (variation across the seascape). Two areas of high juvenile abundance persisted through three decades whereas two in the northeast are now diminished, despite the increased abundance and landings throughout the management units. The persistent areas overlap with full and seasonal area closures, which may act as refuges from fishing. Connectivity was estimated to be 250 km, an order of magnitude less than the distance assumed by the definition of the Canadian management units (~2,000 km). The underlying question of whether there are distinct populations within the southern stock unit cannot be answered with this model, but the smaller ~250 km scale of coherent temporal patterns suggests more complex population structure than previously thought, which should be taken into consideration by fishery management.

Background Flatfish metamorphosis denotes the extraordinary transformation of a symmetric pelagic larva into an asymmetric benthic juvenile. Metamorphosis in vertebrates is driven by thyroid hormones (THs), but how they orchestrate the cellular, morphological and functional modifications associated with maturation to juvenile/adult states in flatfish is an enigma. Since THs act via thyroid receptors that are ligand activated transcription factors, we hypothesized that the maturation of tissues during metamorphosis should be preceded by significant modifications in the transcriptome. Targeting the unique metamorphosis of flatfish and taking advantage of the large size of Atlantic halibut (Hippoglossus hippoglossus) larvae, we determined the molecular basis of TH action using RNA sequencing. Results De novo assembly of sequences for larval head, skin and gastrointestinal tract (GI-tract) yielded 90,676, 65,530 and 38,426 contigs, respectively. More than 57 % of the assembled sequences were successfully annotated using a multi-step Blast approach. A unique set of biological processes and candidate genes were identified specifically associated with changes in morphology and function of the head, skin and GI-tract. Transcriptome dynamics during metamorphosis were mapped with SOLiD sequencing of whole larvae and revealed greater than 8,000 differentially expressed (DE) genes significantly (p

Two new centromeric satellite DNAs in flatfish (Order Pleuronectiformes) have been characterized. The SacI-family from Hippoglossus hippoglossus, restricted to this species, had a monomeric size of 334 base pair (bp) and was located in most of the centromeres of its karyotype. The PvuII-family, with a monomeric size of 177 bp, was initially isolated from the genome of Solea senegalensis, and fluorescent in situ hybridization (FISH) localized the repeat to centromeres of most of the chromosomes. This family could only be amplified in 2 other species of the genus Solea (Solea solea and Solea lascaris). Molecular features and chromosomal location indicated a possible structural and/or functional role of these sequence repeats. The presence of species-specific satellite-DNA families in the centromeres and their possible role in the speciation processes in this group of fishes is discussed.

Ocean acidification and global warming are largely caused by increased levels of atmospheric CO2, and marine fish are exposed to both these stressors simultaneously. Although the effects of temperature on fish have been investigated over the last century, the effects of moderate CO2 exposure and the combination of both stressors are not well-understood, especially long-term effects. In Papers I, II and III we investigated the protein expression and biochemical parameters in gills, blood plasma, and liver of Atlantic halibut (Hippoglossus hippoglossus) exposed to temperatures of 5, 10, 12 (control), 14, 16, and 18 °C (impaired growth) in combination with control (400 µatm) or elevated CO2 (1000 µatm) levels for 3 months. Paper I shows the protein expression in gills and blood plasma of halibuts exposed to elevated CO2 at 12 °C and 18 °C. Elevated CO2 induced the regulation of immune system-related proteins in plasma of fish from both temperature treatments. Gills from fish exposed to elevated CO2 at control temperature show modulation of energy metabolism proteins, as well as indications of increased cellular turnover and apoptosis signalling; while gills from fish exposed to both elevated CO2 and elevated temperature indicate increased expression of energy metabolism proteins. In conclusion, moderate CO2-driven acidification, alone and combined with increased temperature, can elicit biochemical changes that may affect fish health. To further investigate the findings in Paper I we analysed non-specific immune components in blood plasma (Paper II), and examined the occurrence of oxidative stress in liver (Paper III) of Atlantic halibut exposed to elevated CO2 at 5, 10, 12, 14, 16, and 18 ºC. Paper II reveals that both measured immune components (lysozyme and complement system) had increased activities in response to elevated CO2, which is consistent with the findings of Paper I. These changes represent an additional energetic cost for fish. Paper III indicates the occurrence of oxidative stress, which can damage macromolecules such as DNA, membranes, and enzymes. Protein carbonyls were consistently higher in the elevated CO2-treated fish at all studied temperatures, while the antioxidant enzymes did not show the same results, suggesting that the exposure to elevated CO2 increased reactive oxygen species (ROS) formation, with consequent oxidative damage that bypasses the antioxidant defence system of the cells. The consequent oxidative stress might be connected to the increased expression of energy metabolism proteins seen in Paper I. Paper IV provided an overview of elevated CO2 effects at whole organism-level through behavioural studies. Elevated CO2 exposure for 20 and 40 days, caused several behavioural disturbances, including the reduction of boldness, exploratory behaviour, lateralization, and learning in the three-spined stickleback (Gasterosteus aculeatus). The effects were present throughout the exposure period and increased in effect size with exposure time. Given the severity of disturbances, our findings suggest that elevated CO2 could pose a serious problem for sticklebacks. This thesis provides significant insights into how marine fish can be affected by near-future elevated CO2 and temperature. The CO2 levels estimated to occur at the end of this century can pose physiological challenges to marine fish, and have the potential to negatively impact fish populations if acclimation fails to occur.

Sushi is a traditional Japanese food, mostly consisting of raw seafood in combination with rice. However, eating sushi has become popular among consumers in many countries outside Japan. Sushi is not free from health risks and foodborne illness linked to this product has been caused by Listeria monocytogenes . The aim of our work was to study viability of L. monocytogenes in emulated nigiri sushi comprised of halibut and salmon. Raw samples of halibut and salmon were inoculated with the pathogen and subsequently put on top of vinegar marinated sushi rice followed by storage for 7 days at 4 and 8 °C. As controls, inoculated seafood without rice was used. The experiments demonstrated that the level of L. monocytogenes in nigiri sushi was significant lower during storage over 7 days at 4 and 8 °C compared to controls, in case of inoculated seafood only. The pH drop in the fish muscle, caused by the sushi rice, is believed to be the reason for the decrease in viability of L. monocytogenes in nigiri sushi.

The growth, survival and tag retention of double-tagged [external FT4 lock-on (FT4) and internal passive integrated transponder (PIT)-tagged] Atlantic halibut Hippoglossus hippoglossus were compared to internal PIT-tagged controls in a randomized trial. The objective was to assess the suitability of these tags for monitoring the performance of individual fish in longitudinal trials under commercial cage-culture conditions in the lower Bay of Fundy, New Brunswick, Canada. The FT4 tags were chosen due to their similarity to tags used by investigators to track H. hippoglossus in the wild. A subset of the population randomly received an external FT4 tag inserted through the operculum and were monitored over a 1105 day period. The specific growth rate of FT4-tagged fish was significantly reduced in the first sea summer with no significant difference observed for the remainder of the trial. The differential growth in the first sea summer created a relative size advantage, permitting controls to increase in size significantly faster than FT4 fish in all subsequent periods. The FT4 tags did not significantly influence survival under normal commercial cage-culture conditions. Results, however, suggest that the survival of FT4-tagged H. hippoglossus may be compromised during stressful handling events. Tag retention of FT4 tags was acceptable with 76% of tags remaining at the end of the 1105 day trial. FT4 tags proved to be an effective method to identify individual H. hippoglossus, with the caveat that they seriously bias productivity measures in commercial research trials.