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Pollock Pollachius virens (also known as Saithe) modify their feeding habits when including in their diet uneaten feed pellets from salmon aquaculture sea cages. To determine the influence of salmon farms on Pollock, multivariate and univariate analyses were conducted on the trace element signatures from muscle and liver tissues. Sample fish were caught in the vicinity of salmon farms and in control areas (>3-km distance from the farms) on the coast of Hitra Island (western Norway) over two consecutive years (2012 and 2013). The hepatosomatic index was calculated as a proxy of fish body condition and was higher in Pollock captured near the salmon farms in both years. Variations in specific trace element profiles revealed the influence of farming on the Pollock assemblages (i.e., arsenic, manganese, and copper in muscle; vanadium and manganese in liver). Differences in element composition between sampling years were notable and may, in addition to influence from salmon feed, reflect temporal variation in Pollock migrations or natural food availability. Multivariate analyses of each sampling year showed significant differences in trace element composition of both tissue types among the Pollock groups. Therefore, trace element assessment is a potential tool for determining the influence of aquaculture on Pollock populations, although other natural sources of variation must be taken into account when considering future aquaculture and fishery management strategies., his study was part of a project entitled “Evaluation of actions to promote sustainable coexistence between salmon culture and coastal fisheries (ProCoEx),” which was funded by the Norwegian Seafood Research Fund. The study was also supported by the Norwegian Research Council through the EcoCoast project.

This is a pre-print of an article published in Polar Biology. The final authenticated version is available online at: https://doi.org/10.1007/s00300-019-02530-3. The snow crab (Chionoecetes opilio) is an invasive species new to the Barents Sea that expands its geographic range by larval drift and adult migration. To evaluate the potential spreading of the species in the Barents Sea, we investigated temperature selection and the final thermal preferendum (FTP) of nine adult males in a free choice horizontal temperature gradient (~ 1.0–5.5 °C) for 24 h. The crabs displayed clear behavioural thermoregulation – at test start they explored the entire temperature range but eventually gravitated towards a FTP zone of 1.0–1.6 °C (mean 1.4 °C) after 6 h in the gradient. Our tests show that adult male snow crab is limited to cold waters, and suggest a spreading further into the Euro-Arctic shelf seas.

Capture-based aquaculture (CBA) combines aquaculture practices with capture fisheries to keep the catch alive for either short or long periods of time, for feeding or for live storage. CBA enables us to market numerous species ranging from molluscs, scallops and crustaceans to fish such as tuna, cod, eel and groupers. In CBA, handling and adaptation to new environments have an additional influence upon the stressors to which fish are exposed during capture, and the duration of this impact increases dramatically from minutes and hours in traditional fishing to days and months in CBA. We show how a strong focus on welfare is already present in cod CBA fisheries and the rationale behind this focus. We present a case study on CBA of Atlantic cod (Gadus morhua) as a robust example and model species for detecting welfare risks and mitigating against them. We discuss the main welfare issues in relation to the three broad phases of capture, transport and live storage, and identify common current fish welfare challenges in CBA. We highlight the advantages of pursuing this approach using lessons learnt from an industry in which fisheries and aquaculture meet and where an existing and successful knowledge transfer process between fisheries and aquaculture is already under way.

Salmon farms attract large amounts of wild fish, which prey on uneaten feed pellets. The modified diet of the wild fish aggregating at salmon farms may reduce the flesh quality of the fish, influencing the local fisheries. We compared the quality of saithe (Pollachius virens) captured near (farm associated—FA) or more than 5 km away (un‐associated—UA) from salmon farms in Norway. The fish were captured during summer, autumn and spring using two commercial fishing methods (jigging and bottom nets). Overall, the fillet quality of FA saithe was good, although it was clearly reduced for almost 10% of the catch. Moreover, the quality of the FA saithe was significantly reduced compared with UA saithe, but the differences were small. Our results also showed that fish caught with jigging had better quality than fish caught with nets, and that fish that died in the nets were of lower quality than fish that were alive after hauling. There was no clear variation among seasons in fillet quality. Although no major and overall differences in quality were found between FA and UA saithe, reduced quality for even a modest proportion of the fish may influence the value of the total catch. The study was funded by the Norwegian Seafood Research Fund through the ProCoEx project (Project number: 900772) and the Norwegian Research Council through the project ‘ECOCOAST’. Kilian Toledo‐Guedes was supported by a grant from Iceland, Liechtenstein and Norway through the EEA Financial Mechanism (ES07‐EEA Grants, 013‐ABEL‐IM‐2013), operated by Universidad Complutense de Madrid, and Juan de la Cierva Program FJCI‐2014‐20100 and IJCI‐2017‐34174 from Ministerio de Ciencia, Innovación y Universidades.

When fish are reared for food production in aquaculture, they can be held in different types of rearing systems and subjected to various husbandry routines and operations. Each of these systems or operations can present different welfare risks to the fish, which in turn are dependent upon both the species and its life stage. In this chapter, we address and outline potential welfare hazards the fish may encounter in a wide range of existing and emerging rearing systems used for on-growing. These systems include: (1) pond-based aquaculture, (2) flow-through systems, (3) semi-closed containment systems, (4) RAS, (5) net cages and (6) farming offshore using sea cages in exposed conditions. We also outline potential welfare hazards for two key farming operations: transport and slaughter. We present the tools the farmer can use to assess fish welfare during on-growing and also outline relevant welfare actions that can be taken to militate against welfare hazards.

Summary In a study between October and November 2015 in northern Norway, bait prepared from the by-product of the shrimp and snow crab industry was employed in the pot fishery to capture cod and saithe. Frozen natural herring was used as control bait. Pots with the three bait types were placed 1,000 m apart in order to eliminate the risk of interaction between the different baits. In total 11 sampling periods were conducted. There were no significant differences in catch rates between the different baits tested on cod and saithe. The manufactured bait tested in this study showed a continuous release of odours over a 14-day period. Results show that the water content of the bait increases rapidly in the first phase of the immersion (until day 7), and the corresponding loss of bait mass (dry weight) suggest some physical disintegration (erosion) of the bait until the water content stabilizes. This study illustrates that it is possible to replace natural herring with hydrolysates from by-products from shrimp or snow crab industry in the Norwegian pot fishery of cod and saithe.

This study investigates the effects of temperature on the survival, food intake, oxygen consumption and growth during long-term live holding of captive male snow crab (Chionoecetes opilio) (average...

In this study, we investigated the behaviour of Atlantic cod (Gadus morhua) toward three commercially available protein hydrolysates made from shrimp (Pandalus borealis), blue mussels (Mytilus edulis) and capelin (Mallotus villosus), and used blank (seawater) as control. The shrimp and blue mussel attractants were based on industrial waste products, whereas the capelin attractant was produced from industrial quality of capelin. The attraction behaviour study took place during two experimental periods in a 6-m diameter, 28-m3 volume circular tank set up for behavioural studies: Experiment 1 during April 2013, and Experiment 2 during May 2013. In Experiment 1, there were highly significant differences in frequencies of inspections between attractants and controls for shrimps and blue mussel attractants, whereas the inspection of capelin attractants did not occur more frequently than the control. The comparison between the different attractants in experiment 2 enabled a ranking between them, which showed significant higher frequency of interaction with shrimp hydrolysate. The capelin produced lowest frequency of interactions, similar to the first trial, but there were no significant difference between blue mussels and capelin. Results from this study show that hydrolysate from shrimps and blue mussel have the potential to replace natural bait for cod.

The Arctic charr (Salvelinus alpinus) is a relatively stenothermal fish that displays a high degree of biological plasticity. Although primarily a freshwater fish, there are anadromous populations at the northernmost limits of the distributional range. Developmental plasticity has both advantages and disadvantages for establishment in culture, with variable growth rates and early onset of sexual maturation at small size being distinctly disadvantageous. In addition, a requirement for water of low temperature for egg production (4–7°C) and early development limits the possibilities of farming Arctic charr outside of its natural distributional range. On the other hand, a tolerance of high stocking density (60–150 kg m−3) makes it a candidate for rearing in recirculation systems where effective use of both water and rearing unit volume are at a premium. It is possible to farm some strains of charr in either fresh water or brackish water (20 ‰) throughout the year, but year-round farming in full-strength seawater (33–35 ‰) does not seem to be feasible. Photo-thermal manipulation can be used to influence feeding, growth, salinity tolerance and the reproductive cycle. Water quality requirements seem to be similar to those of other salmonids.

As increasing amounts of novel raw materials are used in aquafeed production, it is important to measure their quality against existing ingredients and their effects upon production strategies. A first step to achieving this goal begins with an improved understanding of the underlying growth potential of each farmed species across a range of dietary ingredients and farming practices. Species-specific physiological limitations and metabolic effects of both single chemicals and complex chemical matrixes are factors to be considered in producing robust fish and a healthy aquaculture sector. The industry must also consider ethical, environmental and economic issues and optimize feed management practices. This review summarizes current knowledge on European sea bass (Dicentrarchus labrax) nutritional requirements, presents current feed management practices for this species, gives insights on a secure framework for using plant ingredients in exchange for traditional marine raw materials and outlines its growth potential through a meta-analysis of the best-performance results available in peer-reviewed scientific publications for this species. As the best-performing fish were mostly those fed high fish meal fish oil control diets, the summarized results have the potential to be used as a quality control for benchmarking future scientific research in this fish species.

Seasonal growth patterns have been investigated in juveniles of two reproductively isolated Arctic charr [Salvelinus alpinus (L.)] morphs, which coexist in distinct ecological niches (upper-water and deep-water environments) in a subarctic lake. Offspring (F1-generation) of each of the littoral spawning charr (LO) and the profundal spawning charr (PB) were reared individually over a period of 12 months under simulated natural photoperiod (at 69°N) and two different temperature regimes to mimic the profundal zone conditions with constantly low temperature (~4 °C) and the littoral zone conditions with seasonally cycling temperatures. All charr increased in weight during the experimental period. The LO-morph performed generally best at naturally fluctuating temperature, whereas the PB-morph grew best at a constantly low temperature (4 °C). The LO-morph showed a typical seasonal growth pattern found earlier for anadromous Arctic charr, with elevated specific growth rates (SGR) during June–October and profoundly reduced or negative SGR-values during November–February suggesting that the fish ceased feeding during this period. In contrast, the PB-morph maintained a steady growth rate, regardless of temperature regime, and showed less signs of reduced appetite during the polar night period and exhibited significantly higher SGR-values during late autumn and early winter compared to the LO-morph. This study suggests different heritable adaptations in somatic growth trajectories where the deep-water PB-morph do not show a down-regulation of appetite and voluntary fasting during winter conditions with typically low light intensity and low temperatures, and up-regulation of appetite with hyperphagia during summer, as characteristically found for the upper-water LO-morph and anadromous Arctic charr.

Juvenile green sea urchins, Strongylocentrotus droebachiensis, with an initial mean test diameter of 9.5 mm (±1.2 SD) were held in the laboratory, in individual compartments and at constant temperatures (8.5 C) (n = 90) for a period of 99 wk. The animals were supplied with flow-through sea water, and fed the Nofima sea urchin manufactured feed ad libitum. Growth, survival, feed intake, feed conversion ratio (FCR), and gonad index (GI) of the sea urchins were monitored during this period. The mortality was 11% throughout the experimental period. The test diameter (TD) increased significantly with time, best described by a polynomial equation (TD = 0.8756 + 0.584Time − 0.002Time2, R2 = 0.995). Sex was included as dummy variable, but did not contribute significantly; hence, there were no differences in growth trajectories between males and females. The study showed there were no significant differences in body wet weight or FCR between males and females. However at the end of the experiment the female urchins had a significantly higher GI of 31.1% (±4.4), compared with the male urchins which had an average GI of 26.8% (±5.4). In conclusion, the present study showed that male and female green sea urchins have the same growth capacity and feed convention ratio but by the end of the experiment the gonad index was significantly higher in female than male urchins.

Temperature preference of juvenile (age 1+) Arctic charr (Salvelinus alpinus L.) originating from four arctic and sub-arctic populations (Svalbard and mainland northern Norway), representing a range of habitats with different temperature conditions, was studied by use of a shuttle-box system which allowed individual fish to control their environmental temperature. Based on the assumption that adaptations to long-lasting differences in thermal environments would affect temperature preference, we expected that Arctic charr from the high arctic Svalbard would prefer a lower temperature than the charr from two well-studied sub-arctic mainland lakes (i.e. one anadromous charr population from Storvatn, Hammerfest and two sympatric resident charr morphs from Fjellfrosvatn, Malselv). There were, however, no significant differences in temperature preference among the four populations after 24 h exposure to the shuttle-box system, although the charr from the omnivore upper-water sympatric morph of Fjellfrosvatn used significantly longer time to reach a stable thermal preferendum than the fish of the other populations. The average temperature preference at the end of the trials ranged between 10.9 and 11.6 °C among the populations. The lack of population differences suggests that temperature preference is not a polymorphic trait under strong selection in Arctic charr.

This article describes the status of the Arctic charr (Salvelinus alpinus L.) aquaculture industry in Iceland, Norway and Sweden. The purpose of the work was to give an update on the status of Arctic charr farming in these countries based on information obtained from the industry itself. The data were collected using questionnaires designed for the purpose with key personnel in each country interviewing the farmers or farm managers. The questions were divided on topics focusing on different sides of the production, including farm characteristics, biological challenges and markets. The aim was to identify strengths and weaknesses in the production related to country and production technologies. The information may prove useful for decisions and prioritising future research and development work on removing bottlenecks and improving sustainable production of Arctic charr.

Juvenile green sea urchins, Strongylocentrotus droebachiensis ranging in size from 0.1 to 30 g were held in individual compartments at four constant temperatures (6, 10, 12 and 14 °C) ( n = 54 per temperature treatment) for a period of 100 days. Growth, survival, feed intake and feed conversion ratio (FCR) of the urchins were monitored during this period. There was no mortality throughout the experimental period. The growth of the urchins was significantly affected by seawater temperature with the group held at 6 °C having a significantly lower specific growth rate (SGR) (% body growth per day) than the urchins held in any other temperature treatment. There were no significant differences in specific growth rate (SGR) between the urchins held in the other three temperature groups (10, 12 and 14 °C). Feed conversion ratio (FCR) (grams of feed used to increase the body wet weight by one gram) was also significantly affected by temperature with urchins held at 10 °C having significantly lower FCR values (2.2 ± 0.7) than those held in the 6 °C temperature group (3.39 ± 1.6). These in turn were significantly lower than those in the 12 °C temperature groups (7.02 ± 1.5) and these were significantly lower than those in the 14 °C temperature group (8.8 ± 2.2). Within the temperature groups, FCR was size dependent and decreased with increasing urchin size. In conclusion, the present study shows that a rearing temperature of 10 °C appears to be optimal for juvenile green sea urchins in the size range of 0.1 to 30 g when both feed conversion and growth rate are taken into account.

During rapid decompression in the course of fish capture, cod (Gadus morhua L.) is unable to reabsorb excess gas in the swimbladder sufficiently rapidly, and the bladder ruptures as the gas expands. In capture-based aquaculture (CBA), knowledge of the severity of the rupture stress is required. The objective of this study was to describe the swimbladder rupture and healing processes. Cod captured by Danish seine at depths of between 130 and 200 m were stored in a netpen. At 0, 24, 72 and 384 h post-capture, randomly selected fish (n = 20) were dissected. All fish had ruptured the swimbladder, most close to the dorsal point of pinbones; these holes were sealed and the bladders were inflated. On testing, all the bladders withstood a minimum of 20 mmHg above atmospheric pressure, a strength that increased with time and inversely with the size of holes. As the overinflated bladder deflates after rupture, the two layers of the bladder wall slide relative to each other, closing the open gas passage in ...

The effects of three different temperatures on the growth and maturation of the offspring of cultured versus wild populations of juvenile arctic charr (Salvelinus alpinus L.) were investigated. The fish (start weight 17 g) were reared for 5 months at constant temperatures of 12, 14 and 16°C under a continuous light regime (LD24:0). Growth performance was significantly influenced by both temperature and source population. The offspring from the farmed fish displayed significantly higher mean weights at all temperatures compared with the offspring from the wild fish. The results indicate that the optimal temperature for growth (Topt) decreases with increasing fish size in the offspring of both cultivated and wild fish. Significant differences in length–weight relationship were found, with the offspring of wild fish displaying higher condition factor throughout the experiment. The results demonstrate that the offspring from multiple generation farmed population of arctic charr are better adapted to high temperatures compared with the offspring (F1 generation) from a wild population of arctic charr, and the former are also able to maintain growth at higher temperatures. There was a significant difference in maturation between the two populations, as the offspring from cultured fish displayed significantly lower level of maturation: 0%, 4% and 2% mature compared with 24%, 40% and 42% in the offspring from wild fish at temperatures of 12, 14 and 16°C respectively. The offspring from farmed strains of arctic charr thus appear to be the most suitable population for aquaculture.

The ACE inhibitory activity of a desalted protein hydrolysate from Northern shrimp ( Pandalus borealis ) was studied. Measurements by two independent methods both revealed higher in vitro ACE inhibitory activity, IC 50 = 0.075 and 0.035 mg/ml, respectively, than earlier reported in comparable hydrolysates. Two novel ACE inhibitory tri-peptides, Phe-Thr-Tyr (IC 50 = 275 and 59 μM) and Phe-Ser-Tyr (IC 50 = 7.7 and 2.2 μM), were detected in the hydrolysate. An introductory feeding trial with spontaneously hypertensive rats indicated positive in vivo results when the rats were given 60 mg hydrolysate/kg body weight per day. Although further in vivo studies are necessary to verify the antihypertensive potential, the very high in vitro ACE inhibitory activity reveals that the shrimp protein hydrolysate is a promising candidate for nutraceutical application.

The effect of three different temperatures on growth in a first progeny generation, hatchery reared, subarctic population of European whitefish (Coregonus lavaretus L.) were investigated. The whitefish (start weight 444 g, ±SD 125 g) were reared for 60 days at three constant temperatures; 15, 18 and 21°C and under ambient light regimes for 70°N latitude. The results showed that temperature had a significant influence on the growth of the fish with the highest increase in weight increment occurring at 18°C (mean final weight 656 g ± SD 151 g) compared with the growth of fish held at 15°C (mean final weight 591 g ± SD 143 g) and 21°C (mean final weight 505 g ± SD 121 g). The cumulative per cent mortality of the fish during the experimental period increased with increasing temperature, from 10% at 15°C to 30% at 21°C. The present study indicates that the optimal temperature for farming of European whitefish is somewhere between 15 and 18°C rather than between 18 and 21°C.

Growth, feed intake and maturation were monitored in a fast-growing benthivore morph of European whitefish [Coregonus lavaretus (L.)] held under constant light (LD 24:0) and temperature conditions (10°C) for 415 days. Their growth was best described by polynomial regression model and no indication of seasonal patterns (e.g. winter depression) in growth rates was found. There was no significant difference in food conversion ratio (FCR) between periods during the experiment and the FCR was favourable (0.84). Furthermore, there were no differences in growth between males and females. None of the fish became sexually mature by the time the experiment was terminated, although they had reached a mean size of about 444 g. The European whitefish seems to be a promising aquaculture species as the growth rate was relatively high with a remarkable homogenous growth performance between individual fish within each experimental unit, a relatively favourable FCR, a low degree of agonistic behaviour and negligible growth depression due to internal biological rhythms or gonad maturation. These results were obtained at relatively low temperatures that should be beneficial for sustainable cost-effective farming conditions in cold climate condition in northern Scandinavia.

The growth performance of Arctic charr of wild (W) and hatchery (H) origin was compared in a commercial coldwater recirculation system (Villmarksfisk, Bardu, 68°N, 19°E, Norway). The initial individual body mass was 115 g and similar between groups. The rearing temperature was 9.2 °C and the fish were held under continuous light (24:0 L:D). At the end of the experiment (day 240), the average body mass of the H fish was 451 g compared to 231 g in the W fish. The accumulated mortality of wild Arctic charr was about 40%; 10 times higher than the mortality of hatchery-produced Arctic charr (4%). The difference in growth performance and survival rate impose a great disadvantage of using this wild caught fish as compared to commercially available hatchery-produced Arctic charr in coldwater recirculation system. However, further improvements in the production chain (catching, live transport, quarantine, size grading, etc.) may still make production of wild caught Arctic charr profitable, especially as it demands a higher price in niche markets.

Use of coldwater recirculating aquaculture systems (RAS) are still very rare in Norway, and only two farms are producing Arctic charr. This project took place in one of these commercial Arctic charr farms; Villmarksfisk AS in Bardu, Northern Norway. The farm gets its make-up water from ground water that holds 5 °C year around. Temperature in the rearing water varies between 7.5 °C (“low”) to 12 °C (“high”) through the year. The biological filter in the RAS seems to work stable at both “low” and “high” temperatures, including after incidents when feeding has been stopped for a day and started on top again the day after. Such an extreme change in loading was measured as a 70% increase in TAN concentration, with only minor changes in nitrite levels recorded. The biofilter also kept the nitrite stable and low in spite of diurnal variation in TAN excretion at normal feeding regimes (every day in three periods at day-time). The farming concept is to stock the farm with wild caught juvenile fish for on-growing to market size fish (0.75–1.00 kg). A drop in growth rate during early autumn has been a main concern for the farm. This may reflect a seasonal shift in growth potential, sometimes referred to as “autumn depression”. Interestingly, there is little sign of seasonal changes in the growth of hatchery-produced fish tested in the farm. Sampling of water quality through the seasons in tanks holding fish undergoing such growth depressions indicate that TAN excretion is much higher per kg feed used in the wintertime than in the springtime. This observation corresponds with the lack of weight gain during wintertime despite that the fish is feeding. Thus, feed conversion calculations indicate that feed utilization also varies with season reaching its nadir during this period. Both challenges concerning RAS in cold water and strongly reduced growth in autumn and winter time, have been investigated from 2005 to 2007 in a project financed by the Norwegian research council and the partners in the agricultural framework agreement.

This study investigates how simulation of condensed winter light conditions effects the growth of wild caught Arctic charr (Salvelinus alpinus L.) held in culture. After capturing from Altevatn, Northern Norway, juvenile Arctic charr were cultivated and subsequently individually divided into two groups. The fish were held under identical conditions from May to October including continuous light. Starting from week 41 after capture (October) one group was subjected to a winter light regime of 6 h light and 18 h dark per day (Winter Light group—WL), while light regimes in the second group remained continuous (Light group). After an eight weeks treatment period the WL-group was reverted to the continuous light regime until the experiment ended in May 2007. Results revealed no pre-treatment differences in growth between the two groups. However, starting from two months after the short day treatment, fishes from the WL group had significant higher growth rates compared to L group fish. At the end of the experiment, e.g. five months after the light treatment, fishes from WL group had increased their average body weight by 353 g as compared to 252 g in the L group. Consequently, results show that simulation of winter light conditions can increase the productivity of land-based Arctic charr (Salvelinus alpinus L.) cultivation by 25 to 30%. Thus, management of wild caught charr farming, great care should be taken as to what light regimes the fish are exposed to.

In several areas along the Norwegian coast local fishermen claim that wild migrating Atlantic cod ( Gadus morhua L.) have changed their spawning migratory behaviour following establishment of salmon farms, and no longer enter their natural spawning grounds in the fjords. This has created a heated debate in Norway and, in some areas, passed down a moratorium on establishing new salmon farms. Research has so far not been able to show a causal connection, but it has been suggested that water-soluble odorants from high density salmon stocks in commercial fish farms might be responsible for the avoidance of areas with fish farming and abandonment of nearby traditional spawning grounds. The aim of this study was to test this hypothesis by studying the spatiotemporal distribution of wild migrating cod tagged with acoustic transmitters using an array of automatic listening stations in Oksfjord, a Norwegian fjord with intensive fish farming and traditional spawning grounds for cod. The tagged cod were released either in the outer parts of Oksfjord, i.e. in the area they were caught, or in the inner part of the fjord close to their traditional spawning areas. The olfactory sense was physically blocked for 50% of the fish. Only one cod released in the outer part of the fjord visited the traditional spawning grounds. The majority of the cod that were released in the inner part of the fjord remained in this area for approximately three weeks before they left the fjord. There were no differences in spatiotemporal distribution between cod with intact and cod with blocked olfactory sense. Thus, the results provided no evidence that migrating wild cod avoid areas with fish farming as a response to odorants, but the results do not per se contradict the fishermen's observation that coastal cod have changed their migratory pattern in this fjord.

The influence of dietary fish and plant oils on fatty acid compositions of Atlantic cod tissues was examined to test whether modulation of fatty acid profile following a dietary change differs between lipid-poor (fillet) and lipid-rich (liver) tissues. A dilution model [Robin, J.H., Regost, C., Arzel, J., Kaushik, S.J., 2003. Fatty acid profile of fish following a change in dietary fatty acid source: model of fatty acid composition with a dilution hypothesis. Aquaculture 225, 283–293.] was used for the test. The experiment was divided into a build-up and a restoration phase. Fish weight increased from an initial 30 g to 100 g at the end of build-up and to 300 g at termination. During build-up, triplicate tanks of fish were fed one of four feeds; LF (fish oil, 13% lipid), HF (fish oil, 18% lipid), PO (40 palm oil:20 linseed oil:40 fish oil, 13% lipid) or RO (40 rapeseed oil:20 linseed oil:40 fish oil, 13% lipid). During restoration the cod were fed either LF or HF; four groups experienced a feed change (ROLF, ROHF, POLF, and POHF), and two groups were fed either LF or HF during both build-up and restoration. There were triplicate tanks of fish for each restoration phase treatment. Samples were taken at the start, at the end of build-up, mid-way through restoration and at termination, with four fish being taken from each tank each time; tissue indices were calculated, and analyses of lipid and fatty acids were undertaken, with a focus on 18C fatty acids (18:1 isomers, 18:2n-6 and 18:3n-3) and two n-3 HUFAs 20:5n-3 and 22:6n-3. During build-up, the cod fed HF and LF accumulated relatively more liver lipid than those fed PO and RO, implying that there were differences in the ways in which the lipids in the fish oil and plant oils were digested, absorbed and metabolised. At the end of build-up the cod fed PO and RO had tissues with higher 18C fatty acid, and lower n-3 HUFA, concentrations than the cod fed LF and HF; tissue fatty acid compositions reflected those of the feed oils. The fatty acid profiles of ROLF, ROHF, POLF, and POHF cod were modified during restoration. The changes in concentrations of 18C fatty acids were more rapid than predicted by the dilution model, implying preferential metabolism of 18:1 isomers, 18:2n-6 and 18:3n-3. Concomitant with the decrease in 18C fatty acid percentages there were increases in both 20:5n-3 and 22:6n-3. At termination, fillet percentages of n-3 HUFAs were statistically indistinguishable across treatments, but feed effects on liver lipids 20:5n-3 and 22:6n-3 were still discernible; cod fed PO and RO during build-up had liver lipids with lower percentages of n-3 HUFAs than those of cod fed LF and HF throughout the experiment. The fatty acid compositions of cod tissues are modified following a change in feed oils, but there are some tissue-specific differences in the responses shown. The results indicate that it should be possible to manipulate the fatty acid compositions of cod tissues in desired directions by introducing mixtures of different feed oils at various points in the production cycle.

Feed intake, body growth, and gonad growth of adult green sea urchin Strongylocentrotus droebachiensis were investigated at a constant temperature (10 °C) and a simulated natural photoperiod (70 °N) for 848 days. Three size groups of sea urchins with an initial test diameter of 30–40 mm (small, S, N = 32), 40–50 mm (medium, M, N = 36), and 50–60 mm (large, L, N = 32) were cultured individually and fed a formulated moist feed in excess. During the first period of the trial, the test diameter (days 0–560), the feed conversion ratio (days 0–560), and the gonad index (GI, days 0 and 560) were recorded. The feed intake (FI) was registered during the entire period (848 days) and varied strongly with season for all size groups. Hence, the FI was significantly higher in summer (0.5–0.6 g per animal per day) than in winter (0.2–0.3 g per animal per day). The test diameter, on the other hand, increased in a linear manner with no apparent seasonality. The S group displayed the fastest increase in test diameter and the highest ingestion rare followed by size groups M and L. By day 560, the GI had reached 33–35% irrespective of size group, which is the highest GI-value reported for this species. Overall, our findings demonstrate that the feed intake of the adult green sea urchins is strongly linked to season at a constant temperature, and that the seasonality in feed intake is maintained for years in captivity.

Local fishermen in several areas of Norway assert that salmon farms have caused the wild migrating cod to change their migratory behaviour, so that they no longer enter their natural spawning grounds in the fjords. If the asserted changes in behaviour of wild cod populations can be linked to establishment of salmon farms, water-soluble odorants are then possible candidates to explain such a connection. Chemical stimulants are important to the individual fish's conception of the surrounding environment. High density stocks of fish in a farm are expected to release large amounts of waterborne information. The present laboratory experiments were conducted to test behavioural responses in Atlantic cod exposed to water containing metabolites and waste from farmed salmon. The trials were conducted on single fish in a multiple chamber preference system. The results show that migrating wild Atlantic cod chose to spend more time in chambers without addition of water from the salmon tank, regardless of their maturation status, and even at very low concentrations (0.2%). The avoidance is probably due to presence of chemical compounds with olfactory properties from salmon, since anosmic cod did not elicit such response. Farmed cod, on the other hand, does not avoid water from the salmon tank, and stationary wild cod caught nearby a fish farm had a less pronounced response as compared to wild migrating cod. The response seen is not species specific, as wild migrating cod responded similar to water from a tank holding farmed cod as to water from salmon. These results do not preclude fishermen's observations that cod change their behaviour in areas with fish farming activity. Such a change in behaviour could be a response to water-soluble odorants, but needs to be validated and detailed in further laboratory experiments as well as in nature before any conclusions can be made.

A metabolomics approach was used to analyze effects of salmon farming on wild saithe (Pollachius virens) populations. Saithe fish were captured at two salmon farms and at two control locations around the island of Hitra, Norway. Changes in diet seem to drive changes in metabolic status of fishes. The liver and muscle tissues, from the fishes captured around the farm, showed higher levels of lactate and certain amino acids (glutamine, glutamate, and alanine) and lower levels of glucose and choline than the fishes captured in the control locations, far from the farm locations. The higher levels of lactate and amino acids could be related to the facility of obtaining food around the farm and the deficit in choline to the deficit of this nutrient in the salmon feed. At each location the fish were captured with either benthic gill nets and automatic jigging machines, and this feature showed also variations in different metabolites. This research was funded by the Norwegian Seafood Research Fund through the project “Evaluation of actions to promote sustainable coexistence between salmon culture and coastal fisheries, ProCoEx” (Project 900772). K.T.-G. was supported by a grant from Iceland, Liechtenstein, and Norway through the EEA Financial Mechanism.

Aim A focal task for invasion biology is to identify the environmental variables and biological traits that set and underpin realised and potential habitats of invasive species. Ecophysiology provides powerful empirical knowledge that connects theory with natural phenomena and may improve the accuracy of species distribution modelling. We used the introduced Kamchatka red king crab Paralithodes camtschaticus of the Barents Sea as a prime case to show how thermal behaviour may drive the spreading of a marine invader in context of ocean warming. Finally, we discuss the conceivable consequences for a poleward spread of invasive top predators on native marine biota, conservation and management policies. Location Barents Sea, Euro-Arctic shelves, Northeast Atlantic. Methods We used novel and non-manipulative tests which allowed adult red king crab to freely select and monitor ambient temperature in situ across a < 1–14 °C gradient by means of a temperature data storage tag attached to the carapace. Results Adult red king crab, irrespective of body size, maturation stage and nutritional state, (1) displays clear behavioural thermoregulation in a heterothermal environment and, (2) conclusively selects temperatures in the coldest end of a gradient and avoids temperatures > 4 °C. The final thermal preferendum matches completely present day Arctic shelf temperatures north and east in the Barents Sea. Main conclusions This is the first published study on the thermal behaviour of a marine invasive top predator. Our tests and the concurrent realised habitat north-east of Kola Peninsula suggest that the introduced red king crab is capable of invading the Euro-Arctic shelves in less than three decades. We argue that current management practices of the introduced red king crab compromise Arctic biodiversity and conservation and, to counteract further spreading, we recommend free fisheries on this species across its entire distributional area in the Northeast Atlantic.

The effects of nitrite concentration on growth and feed intake in juvenile cod, Gadus morhua, were examined. In the experiment, juvenile cod with a mean (S.D.) live weight of 7.0 (1.9) g were exposed to four concentrations of nitrite [0, (control), 1.0 (low), 2.5 (medium) and 5 mg NO2–N l− 1 (high)] for 96 days at 8.0 °C, salinity 33 ppt and pH 8.0. No mortality occurred in any of the experimental groups throughout the study. Growth was significantly reduced in fish exposed to all treatment levels, with reduced growth in the high concentration group in the first period of the experiment (day 1–31) and in all experimental concentrations during later periods. No significant difference in feed intake or food conversion efficiency was observed between treatment groups. The fish from the exposed groups displayed an acclimatory response to nitrite. These results indicate that management of intensive aquaculture systems of G. morhua, should avoid levels of nitrite even at 1.0 mg NO2–N l− 1 not to impair growth.

The effects of chronic un-ionised ammonia (UIA-N) exposure on growth and food conversion efficiency in juvenile Atlantic cod, Gadus morhua , were examined. Fish with a mean (SD) initial weight 16.7 (3.4) g were exposed to four concentrations of UIA-N, ranging from 0.0005 mg l −1 (control) to 0.17 mg l −1 , for 96 days at 13 °C. Compared to the control, growth was significantly reduced at UIA-N concentrations above 0.06 mg l −1 , but the fish experiencing the most severe UIA-N concentrations still maintained high growth rates (>1% day −1 ). The growth reduction is attributed to a decrease in food intake. Fish from the exposed groups displayed an acclimatory response to UIA-N, as growth rate reduction in these groups, compared to the control, diminished as the experiment progressed, and in the last period, growth rates in the UIA-N exposed groups were not significantly different from that of the control. Concurrently, a reduction in plasma urea-N content was seen in these groups at the end of the experiment, indicating an increased efflux of urea in response to high ambient UIA-N.

Salmonid farming affects both the environment and other industries, with impacts of wild fish attracted to fish farms being a major concern. Here, we summarized existing knowledge on the impacts of such aggregations around open-cage salmonid farms in Norway on the environment and human activities and on the interactions of these impacts. Waste fish feed is considered the major cause for the attraction of wild fish to the cages. The aggregations of wild fish are relatively persistent and can affect the spatiotemporal distribution of several wild marine species. A change in diet by ingesting the high-energy waste feed available close to the cages may increase the energy stores of some of the attracted fish species, and perhaps also their fecundity, but whether this influences offspring viability is unknown. Changes in the distribution and physiology of the attracted fish can influence local fisheries in terms of resource availability and are probably also associated with the softer, lower-quality meat texture of wild fish caught close to salmonid farms. For fish farmers, the attraction of wild fish to the cages is advantageous because attracted fish eat a substantial amount of the waste feed before it can impact the benthos, and because large attracted fish prey on escaped farmed fish. However, movements of wild fish may play a role in the transfer of diseases, and wild fish may cause farmed fish to escape by damaging the net pens. Due to the complexity of interactions, a combined focus on the impacts of attracted wild fishes on the environment and human activities is warranted when developing future management and governance strategies for salmonid aquaculture. The work was funded by the Norwegian Seafood Research Fund through the project ‘Evaluation of actions to promote sustainable coexistence between salmon culture and coastal fisheries, ProCoEx’ (Project number: 900772) and the Norwegian Research Council through the strategic project ‘ECOCOAST: Kystøkosystemer i endring’.

Effects of photoperiod manipulation on the development of seawater tolerance were studied in Arctic charr. Three groups of fish, previously reared under natural photoperiod and ambient water temperature conditions, were subjected to a constant short daylength, 4L:20D, from 21 December to 30 January, followed by exposure to either 4L:20D, continuous light (24L:0D) or simulated natural photoperiod (nLD). Temperature of the fresh water was held constant at 4°C until mid-May, after which it increased gradually to reach 8.5°C at the termination of the experiment on 2 July. All groups displayed improved seawater tolerance during the course of the study, assessed as changes in plasma chloride and osmolality concentrations following 72-h exposure to seawater (33–34‰). The tolerance to seawater was positively related to fork length within some sampling dates in all groups. Exposure to 24L:0D advanced the development of seawater tolerance by approximately 6 weeks, compared to the nLD group. Both groups displayed increases in gill Na + /K + -ATPase activity that coincided with the period of improved seawater tolerance. Seawater tolerance of the 4L:20D group was delayed by 6 weeks in comparison with that of the nLD group, but without any concomitant increase in gill Na + /K + -ATPase activity. The results corroborate previous findings, and suggest that the seasonal changes in seawater tolerance of Arctic charr are controlled by an endogenous, circannual timing mechanism that is entrainable by artificially extended daylengths in spring. Our data further suggest that development of seawater tolerance in Arctic charr may occur independently of changes in gill Na + /K + -ATPase activity.

Feed intake and growth were studied in groups of turbot fed daily rations of 0.25%, 0.38% and 1% of body weight day–1 for 41 days. Then, all groups were fed 1% of body weight day–1 for the next 34 days. The two restricted rations resulted in reduced growth rates (30% and 60% of fully fed controls), and there was a tendency for increased growth heterogeneity (coefficient of variation increased from about 100% to about 150%) compared with controls on full rations. Nevertheless, restricted rations did not result in any increase in size heterogeneity with the passage of time: the coefficient of variation for weight changed little irrespective of feeding treatment. The turbot became hyperphagic and displayed compensatory growth after the change from restricted to excess feeding, with compensatory growth being most marked among the fish that had been subject to the most severe feed restriction. The results provided some evidence of increased variability in feeding and growth within groups of turbot fed restricted rations, possibly as a result of the establishment of weak feeding hierarchies. When feeding restrictions were lifted, the turbot that had reduced growth under feed restriction were able to completely compensate for lost growth.

Gastrointestinal evacuation of inert particles was monitored in the polar cod Boreogadus saida (Lepechin), held at a temperature of 0.5°C. Fish (31.8 g ± 0.8 SD) were fed a moist diet, based on natural prey items, containing a particulate marker. Evacuation of marker from the gastrointestinal tract started 48 h after ingestion of a meal. The average time needed to evacuate 50% of the marker was estimated to be 132 h, whereas the total evacuation time was approximately 400 h. This may indicate that the polar cod does not feed on a daily basis at temperatures close to zero because of the prolonged time needed to evacuate meals. This work provides a methodological basis for studies of feeding and growth in polar cod using X-radiography.

This study aimed to investigate the effect of different feeding regime in relation to constant light regime on growth and feed intake among juvenile Atlantic cod. Three experimental groups (duplicated) were held under LD12:12 photo period and constant water temperature (12 °C) for six months. All groups were fed daily in excess using three different regimes: fed continuously (control group, DL), fed during light hours (L) or fed during dark hours (D). From an initial weight of 5 g, average body wet weight at the end of the trial in the D group (95 g) compared to L fish (88 g), whereas DL group took an intermediate position (91 g). No significant differences were observed between the groups at either time. The D group appeared to have higher feed conversion efficiency compared to the other groups, although there were no significant differences between the groups.

L'evacuation gastrointestinale de marqueurs inertes, denses aux rayons X par le turbot, Psetta maxima, a ete suivie par radiographie. Des groupes de turbots marques individuellement et âges d'un an (1 +; 136,5 g) ont ete maintenus a 16 °C et acclimates a une duree d'alimentation de 4 heures par jour. Les poissons ont ete nourris de granules distribues en exces. Le protocole experimental permettait un test des effets du stress du a la manipulation des poissons et a l'alimentation sur les dechets gastrointestinaux. Les manipulations repetees des poissons affectent l'absorption de nourriture mais il n'y a pas d'effets significatifs du traitement sur le taux d'evacuation gastrointestinal. Les poissons qui ingerent de plus grandes quantites d'aliments presentent des taux plus eleves d'evacuation de marqueurs, mais le temps total d'evacuation est plus long pour les poissons qui consomment de plus grandes quantites. Les particules marquees commencent a quitter le tractus digestif environ 10 heures apres le debut de l'absorption d'un repas, et l'evacuation des marqueurs est achevee en 52 heures dans les conditions experimentales de cette etude.

Fish can be the recipients of numerous injuries that are potentially deleterious to aquacultural production performance and welfare. This review will employ a systematic approach that classifies injuries in relation to specific anatomical areas of the fish and will evaluate the effects of injury upon production and welfare. The selected areas include the (1) mouth, (2) eye, (3) epidermis and (4) fins. These areas cover a large number of external anatomical features that can be injured during aquacultural procedures and husbandry practices. In particular, these injuries can be diagnosed on live fish, in a farm environment. For each anatomical feature, this review addresses (a) its structure and function and (b) defines key injuries that can affect the fish from a production and a welfare perspective. Particular attention is then given to (c) defining known and potential aquacultural risk factors before (d) identifying and outlining potential short- and long-term farming practices and mitigation strategies to reduce the incidence and prevalence of these injuries. The review then concludes with an analysis of potential synergies between risk factors the type of injury, in addition to identifying potential synergies in mitigation strategies. The paper covers both aquaculture and capture-based aquaculture.