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Abstract The effects of temperature and growth hormone (GH) implantation on growth of juvenile Atlantic wolffish (Anarhichas lupus) were investigated. The year-long study had three sequential experimental phases (EP) termed EP1, EP2 and EP3, lasting for 6, 9 and 37 weeks, respectively. The experimental fish were divided into four groups and reared at different target temperatures (3, 7, 11 and 15 °C) during EP1 and EP2, but at a constant temperature of 7 °C during EP3. At the beginning of EP2, half of the fish from each group was implanted with formulation of recombinant bovine GH (Posilac®), while the other half was sham-implanted with vehicle. The optimal temperature for growth (T opt.G) of early juveniles (geometric mean weight 7.5 g) was determined as 12.1 °C during EP1, while the upper critical temperature (Tc) was concluded to be very close to 15 °C, as fish at that temperature had stunted growth, increased mortality and showed external signs of skeletal deformities. Thus, the species was found to be relatively stenothermic during the early juvenile stages and therefore vulnerable to relatively modest increases in environmental temperature above T opt.G. At 15 °C, GH implantation had no effects on growth rate. This indicates that the high allostatic load at this temperature leaves no scope for increased growth. In contrast, at lower rearing temperatures, the GH implantation had substantial, long-term effects on growth rate and induced remarkably similar relative growth stimulation at 3, 7 and 11 °C, suggesting a temperature-independent mechanism for the growth-promoting effects of GH. Highlights • The narrow span from optimal temperature for growth to upper thermal tolerance limits is notable and of concern. • GH treatment reveals significant growth potential and a temperature-independent growth-promotion mechanism. • Absence of growth stimulation at the upper thermal tolerance limits indicates a shift of energy use to vital functions. [ABSTRACT FROM AUTHOR]

The Atlantic wolffish ( Anarhichas lupus) is listed by Canada's Species at Risk Act as a species of special concern. Effective conservation strategies rely on accurate knowledge of habitat requirements, distribution, and vulnerabilities; however, current management plans cite lack of wolffish habitat data as a key limitation. For this study, coastal Atlantic wolffish denning habitat was characterized and mapped with high-resolution multibeam data and seafloor video in Conception Bay, Newfoundland. Four Atlantic wolffish dens, used for feeding, spawning, and egg-guarding, were surveyed and mapped. On the basis of the geomorphology and substrate of these dens, a supervised classification was applied to the multibeam bathymetry and backscatter data to identify other potential denning areas. Predicted denning habitat, limited by the occurrence of suitable rocky substrate, is most prevalent in shallow waters (<22 m) distributed over 1.6 km2 (5.9%) of the study area. Shallow denning habitat is exposed to seasonal maximum temperatures that exceed the threshold for normal Atlantic wolffish egg development, a potential vulnerability for nearshore wolffish. As management efforts progress, this information will guide research and prioritization of conservation areas. [ABSTRACT FROM AUTHOR]

Biological data were retrieved from 3694 female Atlantic wolffish Anarhichas lupus collected in Icelandic waters at four locations during the breeding season using a long–term study spanning from 2002 to 2013. The main objective was to investigate reproduction investment and timing. In the main spawning ground, little temporal differences were observed. In contrast, the peak of the spawning season was different among spawning grounds, suggesting spatial differences in the timing of reproduction. The size of females A. lupus was related to the spawning time with the larger fish spawning earlier than smaller ones. In addition, no significant pattern was found between temperature and spawning time. Except at its main spawning area where spawning begins in late September, spawning usually began in late August or beginning of September and was completed in early November. [ABSTRACT FROM AUTHOR]

This study evaluated the sensitivity of the wolfish Anarhichas denticulatus exposed to crude oil, comparing the effects of mechanically dispersed versus chemically dispersed oil using sub-lethal endpoints. To test the toxicity of this controversial technique, two experiments involving exposure of the organisms for 48 h were conducted. The first experiment assessed the effects of oil exposure on biomarker responses. The second experiment monitored the growth of juveniles over 5 weeks after exposure. Overall, this study demonstrated that polycyclic aromatic hydrocarbon (PAH) biliary metabolites, ethoxyresorufin- O-deethylase (EROD), and acetylcholinesterase (AChE) are appropriate biomarkers to assess exposure of A. denticulatus. Growth rate, both in length and weight, was significantly higher in control compared to oil exposure treatments. The lack of differences between chemically and mechanically dispersed oils in biomarker response and growth suggests that dispersant application is no more toxic than the natural oil dispersion. The results indicate the potential for population-level effects resulting from exposure to oil. [ABSTRACT FROM AUTHOR]

Society is moving towards a no-analogue climate that will fundamentally affect ocean ecosystems and the socio-economic activities that depend on them. Warming has led to displacements of various populations, calling for an adaptation of fisheries management plans and Species at Risk recovery strategies. Dissolved oxygen (DO) has declined, but its impacts on habitat are much less studied. Severe hypoxia is lethal, but even sublethal hypoxia can trigger species displacements. We use Atlantic wolffish (Anarhichas lupus) as a case study to investigate the impact of DO on optimal habitat on the Scotian Shelf, Canada, considering that their habitat becomes suboptimal at DO lower than 65% saturation. First, we demonstrate that DO has decreased using two observational climatologies before and after 1980, and that the spatial pattern of the associated expansion of low oxygen waters (DO, 65% saturation) over the shelf is consistent with the observed contraction of Wolffish population. Then, we use a spatially explicit regional ocean model that couples physical and biological processes to simulate a scenario in which a continued decline of DO in the open ocean leads to a further expansion of low oxygen waters over the shelf. The future low DO extends to regions that currently have high Wolffish biomass, and likely other species as well. While fishing pressure likely drives the observed decline in Wolffish, both observations and model scenario suggest that DO can further constrain habitat. We argue that management/recovery plans should consider DO as one of the potential stressors of not just Atlantic wolffish but any oxygen-sensitive species. Finally, we emphasize that biogeochemical ocean models can inform management by elucidating the direction and ranges of future changes in ocean environmental conditions. [ABSTRACT FROM AUTHOR]

Deux spécimens adultes d'Anarhichas denticulatus (Krøyer, 1845) ont été capturés pour la première fois dans la partie méridionale du golfe de Gascogne (Nord-Est Atlantique). Ces nouvelles occurrences permettent d'élargir considérablement vers le sud, l'aire de répartition de cette espèce et de fournir de plus amples informations sur certains aspects de sa biologie. [ABSTRACT FROM AUTHOR]

Biological data from 1125 female Atlantic wolf-fish Anarhichas lupus were collected during 2002-2006 at their main spawning and fishing grounds in Iceland. The results demonstrated substantial annual variation in growth and maturity of female A. lupus. The fast growing females mature earlier than the slow growing ones. In addition, females mature at a larger size and greater age in warmer temperatures than colder ones. There was a strong negative relationship between temperature and growth, which may indicate that the sea temperature west of Iceland has risen above the optimum for growth of female A. lupus and thereby reduced the reproductive potential of the species. [ABSTRACT FROM AUTHOR]

Abstract: The morphology, ontogeny and tissue distribution of mast cells were studied in common wolffish (Anarhichas lupus L.) at the larval, juvenile and adult life stages using light and electron-microscopy and immunohistochemistry. Fish were sampled at 1 day, 1, 2, 3, 4, 8 and 12 weeks post-hatching in addition to 6 and 9 months and 2 years and older. From 8 weeks post-hatching, mast cells in common wolffish mainly appeared as oval or rounded cells 8–15 μm in diameter with an eccentrically placed, ovoid nucleus and filled with cytoplasmic granules up to 1.2 μm in diameter. Granules were refractile and eosinophilic to slightly basophilic in H&E and stained bright red with Martius-scarlet-blue and purple with pinacyanol erythrosinate in formalin-fixed tissues. Mast cells stained positive for piscidin 4 and Fc ɛ RI by immunohistochemistry. From 1 day to 4 weeks post-hatching, immature mast cell containing only a few irregularly sized cytoplasmic granules were observed by light and electron-microscopy in loose connective tissue of cranial areas. From 1 day post-hatching, these cells stained positive for piscidin 4 and Fc ɛ RI by immunohistochemistry. From 12 weeks post-hatching, mast cells showed a primarily perivascular distribution and were particularly closely associated with lymphatic vessels and sinuses. Mast cells were mainly located at the peripheral border of the adventitia of arteries and veins, while they were in intimate contact with the endothelium of the lymphatic vessels. Numerous mast cells were observed in the intestine. A stratum compactum, as described in salmonids, was not observed in wolffish intestine, nor were mast cells confined to a separate layer, a stratum granulosum. Lymphatic vessels consisting of endothelium, intimal connective tissue and a poorly developed basal lamina were observed in the intestine. Scanning electron microscopy was used to compare the structure and localization of intestinal mast cells of common wolffish and rainbow trout. Scanning electron microscopy also revealed endothelial surface features and confirmed the existence of three distinctly different types of vessels in the wolffish intestine. Rainbow trout mast cell granules appeared as intact globular structures while empty vacuoles were observed in common wolffish. Mast cells were closely associated with lymphatic vessels in common wolffish, but not in rainbow trout. [Copyright &y& Elsevier]

The purpose of this study was to determine the cortisol response of spotted wolffish (Anarhichas minor) after exposure to air immersion and netting (acute stress) under a range of increasing densities (chronic stressor). In addition, the presence of a cumulative negative impact from chronic stress was assessed by the application of an additional acute stressor following rearing at various densities, and proxies of behavior were evaluated (feeding and aggression data). The stress response to air immersion and netting led to increasing plasma cortisol values at 0.5, 13, and 37 h post-stress, with the highest value achieved after 13 h. At 168 h, cortisol concentrations returned to similar pre-stress value. Changes in cortisol concentrations were relatively low after acute stress (five to six fold increases) and recovery time long lasting (>37 h). Prolonged rearing at 20, 30, and 40 kg m−2showed a non-significant trend of increasing cortisol values with increasing density, and the cortisol response after the application of an additional acute stressor was significantly altered, i.e., higher cortisol levels were measured in unstressed (chronic stress only) compared to stressed fish (chronic stress + acute stress). Our results suggest that (1) spotted wolffish is a low responder that additionally displays a long-lasting cortisol elevation following an acute stressor; (2) fixed densities did not lead to significant differences of plasma cortisol concentration or aggression levels, although involved marked changes in daily feed intake and food conversion efficiency were observed; and (3) cortisol levels reached acute stress values after prolonged chronic stress. Although this species displays indications of being relatively resistant to handling disturbances during aquaculture practices, it is nevertheless responsive to chronic stress factors that could alter the physiological response to subsequent acute stressor. [ABSTRACT FROM AUTHOR]

Abstract: Growth rate is dependent upon adequate provision of amino acids especially in newly-hatched fish which experience very high growth rate. The replacement of a fraction of protein content by partially hydrolyzed (pre-digested) proteins was carried out and the digestive capacities and performances of larval/juvenile spotted wolffish (Anarhichas minor) were measured. The goal of this study was to verify whether the scope for growth is principally dictated by the proteolytic capacity of the digestive system by examining the effect of protein hydrolysates (PH) and trypsin inhibitor dietary inclusion on protein digestion/assimilation capacities, growth and survival. Four experimental diets were examined: C (control) I (supplemented with 750mg/kg soybean trypsin inhibitor (SBTI)) H (supplemented with 20% PH) and HI (supplemented with 20% PH and 750mg/kg SBTI). Protein hydrolysate supplementation gave significantly higher body mass than control at day 15 post-hatching. Unexpectedly, at day 30 and 60, fish administered diet HI (containing trypsin inhibitor) were heavier than the other groups. Suggested mechanisms are presented and discussed. The main conclusions of this study are that wolffish larval stage lasts roughly 15days and that juvenile growth is linked to proteolytic capacity, but also very likely to absorption capacity of peptides and amino acids. [Copyright &y& Elsevier]

Genetic variation was assessed in Atlantic wolffish, Anarhichas lupus, across the North Atlantic Ocean using microsatellite and amplified fragment length polymorphism (AFLP) markers. Despite unusual life history attributes such as large benthic eggs, large larvae, a limited pelagic stage and relatively sedentary adults, which suggest potential for strong population structure, range-wide FST values were comparable to other marine fishes (≤0.035). Nevertheless, both significant genetic differentiation among regions and isolation by distance were observed, suggesting limited dispersal in this species. AFLP loci, evaluated on a subset of samples, revealed slightly higher FST values, but similar patterns of differentiation and isolation-by-distance estimates, compared to microsatellites. The genetic structure of Atlantic wolffish has likely been shaped by its post-glacial history of recolonization, North Atlantic current patterns and continuity of habitat on continental shelves. [ABSTRACT FROM AUTHOR]

Phylogenetic analyses of all 4 wolffish species (Atlantic, Spotted, Northern, and Bering wolffishes) and the Wolfeel were assessed with both mitochondrial (D-loop and ND1) and nuclear (amplified fragment length polymorphism) DNA to resolve relationships within the family Anarhichadidae. Species-specific mitochondrial DNA (mtDNA) mutation rates were estimated based on 2 possible dates of divergence between the Pacific and Atlantic lineages. Phylogeographic patterns within each of the 3 North Atlantic wolffishes were investigated with Markov chain Monte Carlo simulations based on mtDNA to determine whether population size changes occurred following the last glaciation and where wolffishes likely survived glaciation. All 3 species of North Atlantic wolffishes showed evidence of postglacial expansion but did not show evidence of persistence in multiple refugia in both the eastern and western Atlantic Ocean. Rather, the data supported persistence in a single refuge, with postglacial expansion into the rest of the range. Nucleotide diversity, in particular, was low in wolffishes compared with other marine fishes, possibly related to reductions in population sizes during the last glaciation. [ABSTRACT FROM PUBLISHER]

The goal of this study was to determine the optimal stocking density for rearing juvenile spotted wolffish, Anarhichas minor (Olafsen), at two different sizes and assess the welfare status in relation to density. No major growth impairment was observed, although smaller fish (50–100 g) were significantly affected by density during the 120 days of the experiment, with final mean weights of 119.6 ± 11.6, 118.0 ± 5.8 and 88.7 ± 0.6 g for initial rearing densities of 10, 20 and 40 kg m−2 respectively. No effect of rearing density was seen for larger fish (100–160 g) during the 90 days of the experiment, with final mean weights of 160.2 ± 5.9, 159.7 ± 3.7 and 163.7 ± 11.5 g at fixed rearing densities of 20, 30 and 40 kg m−2 respectively. Our results suggest that the optimal rearing density of juvenile spotted wolffish is below 40 kg m−2 for smaller size fish (∼50–100 g) and probably ≥40 kg m−2 for the larger fish (100–160 g). Furthermore, it appears that the range of rearing density used did not have a significant effect on a selection of stress indicators (Na+ and K+ concentration, haematocrit, hepatosomatic index, total amount of plasma proteins and liver and muscle water content) and immunity response (plasma lysozyme activity) of juvenile spotted wolffish, making it a very tolerant species to crowding. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted to assess shelter use and behaviour of juvenile Spotted Wolffish, Anarhichas minor, using time-lapse video. Information about the behaviour of Spotted Wolffish and its habitat utilization is sparse due to the great depth at which this species lives. Four experiments were conducted using one or two fish per tank, with and without a shelter. The positions and movements of fish in the tanks and interactions between fish were monitored over 24-h periods. In experiments in which no shelter was available, Spotted Wolffish spent very little time exploring the water column. They did not show fidelity to a particular area on the bottom of the tank and exhibited few signs of aggressiveness to each other. When a shelter was made available, fish spent most of their time in the shelter or close to the shelter. The presence of a single shelter did not enhance aggressive behaviours in fish kept in pairs. When day and night observations were compared, no clear diel pattern emerged. The Canadian recovery plan for Spotted Wolffish calls for research aimed at describing their use of demersal habitats. The present study suggests that shelter availability might be an important feature of the habitat requirements of juvenile Spotted Wolffish. [ABSTRACT FROM AUTHOR]

The effect of temperature and mass on specific growth rate ( G) was examined in spotted wolffish Anarhichas minor of different size classes (ranging from 60 to 1500 g) acclimated at different temperatures (4, 8 and 12° C). The relationship between G and 20S proteasome activity in heart ventricle, liver and white muscle tissue was then assessed in fish acclimated at 4 and 12° C to determine if protein degradation via the proteasome pathway could be imposing a limitation on somatic growth. Cardiac 20S proteasome activity was not affected by acclimation temperature nor fish mass and had no correlation with G. Hepatic 20S proteasome activity was higher at 12° C but did not show any relationship with G. Partial correlation analysis showed that white muscle 20S proteasome activity was negatively correlated to G (partial Pearson's r = −0·609) but only at cold acclimation temperature (4° C). It is suggested that acclimation to cold temperature involves compensation of the mitochondrial oxidative capacity which would in turn lead to increased production of oxidatively damaged proteins that are degraded by the proteasome pathway and ultimately negatively affects G at cold temperature. [ABSTRACT FROM AUTHOR]

We compared growth properties of spotted wolffish with initial mean weight (± SE) 3.65 (± 0.15) kg reared in shallow raceways at three different densities (50, 70, and 90 kg/m2, corresponding to approx. 170, 240, and 310 kg/m3) in a 447-day-long growth trial at ambient temperature (mean (± SD), 4.2 C ± 1.9). Growth in all three groups was comparable, but there was a trend toward higher growth at the highest density. Final mean weights (kg ± SE) were 4.90 (± 0.15), 4.80 (± 0.16), and 5.05 (± 0.11), at the 50, 70, and 90 kg/m2 density, respectively. Initially, growth rates were higher at the 90 kg/m2 density group compared to the two other densities, but overall growth rates were similar in all three groups. Feed conversion efficiency differed and was higher at the two highest densities compared to lowest density. The acid–base balance was influenced by the density treatment as there was a general trend toward higher partial pressure of CO2 and HCO in the 90 kg/m2 group. Calculated productivity increased almost linearly with increasing stocking density and was found to be 24, 42, and 66 g/m2/day at 50, 70, and 90 kg/m2, respectively. The results show that the optimum density conditions for farming large spotted wolffish, both with respect to growth rate, feed conversion, and productivity are at densities equal to or higher than 90 kg/m2. [ABSTRACT FROM AUTHOR]

Abstract: The spotted wolffish (Anarhichas minor) is considered a promising species for coldwater aquaculture. It is a sedentary, bottom-dwelling fish which exhibits a calm and “non-stressed” behaviour in captivity. There are, however, no reports on the physiological responses to stressors in this species. In the present study we investigated primary (cortisol secretion) and secondary (glucose mobilization) responses to common aquaculture stressors like disturbance and hypoxia. Pre-stress plasma cortisol levels were within those generally considered representative for unstressed fish (~10ng ml−1), whereas basal glucose levels were unusually low (0.3–0.4mM). After exposure to a short, but severe disturbance challenge (emptying the tank of water for 10min), the increase in plasma cortisol level was slow and relatively weak, reaching a peak level of 25ng ml−1 4 to 8h after disturbance. When the fish were exposed to a gradually decreasing oxygen level in the tank, a significantly elevated plasma cortisol level (35ng ml−1) was seen in the fish that remained in the tank until oxygen saturation had decreased to 20% oxygen saturation after 2.5h. However, a two-fold higher plasma cortisol level (~70ng ml−1) was seen in all fish exposed to reduced oxygen levels (60, 40 and 20% oxygen saturation) after 3.5h recovery in normoxic water. Plasma glucose levels showed only moderate increases (~70%) following disturbance and hypoxia challenges. An in vivo injection of ACTH caused a strong elevation of plasma cortisol (peak level ~170ng ml−1), demonstrating a high capacity for interrenal steroidogenesis in the spotted wolffish. The slow and relatively weak cortisol response to stressors, and low plasma glucose levels, may relate to the sedentary lifestyle of the spotted wolffish. The stress-response is characterised by a passive (reactive) coping style, which is considered adaptive for farming of this species. [Copyright &y& Elsevier]

This is the first report of early-life developmental characteristics (coloration pattern, growth and survival) and genetic identification of the wolffish interspecific hybrid between Anarhichas minor and A. lupus, both endangered species in Canadian coastal water and of interest for cold-water aquaculture diversification. A first growth trial at 8 °C featuring pure strains A. minor and the hybrid A. minor × A. lupus in triplicates was conducted in 2006 during the period from 0 to 140 days post-hatch. A second growth trial was runned in 2007 featuring A. minor, A. lupus and the reciprocal hybrids A. minor × A. lupus and A. lupus × A. minor. Egg development indicators and early-hatching characteristics are reported. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of different salinities and temperatures and their possible interactive effect on growth performance, feeding parameters, and blood physiology in juvenile spotted wolffish, Anarhichas minor, reared at different temperature (7 and 10 C) and salinity (15, 25, and 34‰) combinations. There was a significant interactive effect between temperature and salinity on growth, as a growth-enhancing effect was seen at intermediate and full salinities at higher temperature, whereas the reciprocal trend was seen at lower temperature. Mean total feed consumption, daily feeding rate, and feed conversion efficiency were all highest at the intermediate salinity at 10 C, whereas at 7 C, the feeding parameters were highest at low and intermediate salinities. Blood plasma sodium content was lowest at 15‰, whereas the opposite trend was seen in partial pressure of CO2 and bicarbonate in blood where the highest concentrations were seen at 15‰. This study demonstrates that spotted wolffish has a high osmoregulatory and acclimatory capacity. In an aquaculture context, growth of juvenile spotted wolffish can be improved by rearing the species at high temperature and intermediate salinity combinations at least in a limited period of the juvenile phase. [ABSTRACT FROM AUTHOR]

Fecundity, maturity and growth of spotted wolffish Anarhichas minor were studied in Icelandic waters. A total of 477 female A. minor were sampled. The time from the onset of the cortical alveolus stage until spawning was on average 5 years. The total length ( LT50) and age ( A50) at 50% maturity for spawning fish was 827 mm and 9·1 years. Observed average annual growth was 65 mm for A. minor at the age range 5–10 years. Spawning fish grew faster than fish at the cortical alveolus stage. Growth and maturity of A. minor in Iceland appeared to be similar to growth and maturity of A. minor in the Barents Sea. The fecundity of Barents Sea fish was, however, higher than Icelandic fish. [ABSTRACT FROM AUTHOR]

Three groups of newly hatched spotted wolffish ( Anarhichas minor) were held at three different temperatures in order to determine relationships between metabolic, digestive and growth response in rapidly developing larvae. Growth rates were successfully modulated by temperature (5, 8 and 12 °C). Activity levels of trypsin and lactate dehydrogenase (LDH) were positively linked to specific growth rates at all temperatures. Trypsin showed a positive compensation (higher activity at lower temperature) whereas glycolytic enzymes (pyruvate kinase and Lactate dehydrogenase) and aspartate aminotransferase (AST) showed a negative compensation (lower activity at lower temperature). Citrate synthase was not affected by growth rate, indicating that the level of aerobic capacity was adequate in sustaining the high energetic needs associated with rapid growth early in the life of the spotted wolffish. In light of our results, it is suggested that protein digestion, as demonstrated by the activity profile of trypsin in relation to growth rate and temperature, is likely a key growth-limiting agent during the early-life stages of wolffishes. Our results are discussed in comparison with A. lupus, a closely related species displaying different temperature preferences and growth capacities. [ABSTRACT FROM AUTHOR]

Sixteen tetranucleotide and dinucleotide microsatellite markers were isolated from Atlantic wolffish, Anarhichas lupus, following a microsatellite enrichment procedure using probe-labelled magnetic beads. These microsatellites were intended for use in Atlantic wolffish as well as in two closely related species, spotted wolffish, Anarhichas minor, and northern wolffish, Anarhichas denticulatus. As all three species are of conservation concern in Canadian waters and as forensic wildlife cases may arise for this genus, microsatellite markers were assessed to determine how well they differentiate these species from one another and to estimate probability values that could be expected for identification of individuals to species. [ABSTRACT FROM AUTHOR]

Abstract: Flat-bottom sea cages offer a cost-effective alternative for culture of bottom-dwelling fish. In an experiment lasting 428 days, spotted wolffish (Anarhichas minor Olafsen) grew equally fast when kept in tanks on land and in a flat-bottom sea cage at the same stocking density (increasing from 7.5 to 42 kg m−2 during the experiment) and same water temperature. A lag phase of 1 month with negative growth was observed following transfer from tanks to the sea cage. The results confirm that flat-bottom sea cages may be an option for culture of this species. [Copyright &y& Elsevier]

We compared growth properties of juvenile spotted wolffish with initial mean weight (±SE) 105.9 (±3.1) g reared in shallow raceways and conventional circular tanks in a 202-d-long growth trial at ambient temperature (approximately 4.0 C). From Day 41 onward, the fish in the shallow raceways was significantly larger, and final mean weights were 356.3 (±18.2) and 318.2 (±15.6), in the shallow raceways and the circular tanks, respectively. Overall, growth rates were 14% higher (0.62%/d) in the shallow raceway group compared to the circular tanks (0.52%/d). Feed conversion efficiency differed and was 17% higher in the shallow raceways (1.01) compared to the circular tanks (0.84). Correlation between adjacent growth rates was more profound in the circular tanks (mean Spearmans rank, rSp = 0.38) than in the shallow raceways (mean rSp = 0.15). This could indicate a stronger social hierarchy in conventional tanks leading to suppressed growth, which is in line with the growth data presented in this study. The findings of the present study may have important consequences for optimization of commercial production of spotted wolffish and could be applicable to other bottom-dwelling species. [ABSTRACT FROM AUTHOR]

The activity of glycolytic enzymes and the expression levels of myosin RNA was monitored in the white muscle of juvenile spotted wolffish (Anarhichas minor) reared under different temperature regimes. A group of individually tagged juvenile spotted wolffish was reared for 6 months at 4, 6, 8, and 12 °C. After the rearing trial, biopsy samples were taken from white muscle of each individual and the relationship between individual growth, enzyme activity, and myosin expression was investigated. A positive relationship between the activities of two glycolytic enzymes (pyruvate kinase and lactate dehydrogenase) and individual growth rate was observed. Using real-time polymerase chain reaction (PCR) and specially developed primers for myosin mRNA and 18S rRNA for spotted wolffish, we were able to detect differences in the relative myosin expression between experimental groups, and a positive relationship between myosin expression and specific growth rates was observed. These methods may be useful as an indicator of growth rate in wild fish and a fast and reliable indicator of growth potential under culture conditions. The method also has the potential to measure differences in white muscle synthesis in fish reared under variable environmental parameters and during different life history stages. [ABSTRACT FROM AUTHOR]

The effect of feeding two different diets, containing 38 and 45% protein and 35 and 28% lipid, respectively, on growth as well as performance of the digestive proteases (total protease at pH 1·5, 7·0, 9·0 and 10·0) and carbohydrases (total carbohydrase, α-amylase and α-glucosidase) of a new candidate species for aquaculture, the carnivorous spotted wolffish Anarhichas minor (Teleostei, Anarhichadidae), was investigated. No significant growth differences were observed when feeding high protein (HP) or low protein (LP) levels ( P > 0·05), although the LP group exhibited slightly higher protease activity and capacity ( P > 0·05), mostly at the anterior end of the intestine and at alkaline pH. Carbohydrase levels were generally low, apart from α-glucosidase, which was significantly increased for the HP group ( P < 0·05). Implications concerning the performance of digestive enzymes under varying dietary macronutrient levels and effects of digestive enzyme activity on the formulation of efficient artificial diets for carnivorous fishes are discussed in this study. [ABSTRACT FROM AUTHOR]

The article talks about the Gyrodactylus anarhichatis Mo & Lile (Monogenea: Gyrodactylidae) infection of Iceland's farmed spotted wolffish, Anarhichas minor Olafsen. It aims to investivate the potential pathogenicity of this parasite to farmed spotted wolffish. More information is given in the article.

The article focuses on the electron microscopic study of endocytosis of indigenous bacteria and cell damage caused by Vibrio anguillarum in the foregut and hindgut of spotted wolffish Anarhichas minor. The authors suggested two mechanisms involved in bacterial translocation of indigenous gut bacteria. The difference in bacterial translocation between indigenous gut bacteria and pathogens has not been elucidated. The results reached a hypothesis that paracellular bacteria translocation is a secondary effect of detachment and loss of enterocytes and increased intracellular gap when the fry is exposed to V. anguillarum.

Two egg batches of spotted wolffish, Anarhichas minor Olafsen, were incubated at 4, 6 and 8°C. Embryo samples were fixed and compared on each 100th daydegree until hatching (up to 1000 daydegrees). Embryos, yolk sacs and chorions were dissected and the sizes, wet and dry weights were recorded separately. Comparisons of gross morphologies and measured parameters showed increasing and generally significant differences with time between the incubation temperatures. Lower temperatures produced longer and more differentiated larvae at hatch with a smaller yolk sac. Even though some unexpected deviations were registered among batches and experimental groups, it was clear that temperature affected embryo survival and time of hatching. Overall survival was best at 6°C, in agreement with results from earlier studies. Yolk conversion efficiencies measured around the hatching point were generally high, ranging from 60% to 78%, varied between the two batches and probably reflected the developmental variations between embryos and larvae at the respective ages (daydegrees). The hatching process was apparently an energy-demanding period; yolk conversion efficiencies of unhatched embryos of similar age at each temperature were always higher. Temperature is one environmental factor that can be manipulated in hatcheries to induce hatching of viable larvae at an optimal stage of differentiation with respect to first-feeding success and early survival. [ABSTRACT FROM AUTHOR]

Histomorphological studies on the dynamics of intestinal epithelium in larvae, juveniles and adult stages of common wolffishAnarhichas lupusshowed that the major structural development took place during the first 8 weeks after hatching( c. 320 day degrees). This development preceeded a period of increase in relative growth. The mucosa of the proximal and distal intestine gradually developed from simple primary mucosal folds into a complex structure of primary and secondary folds with regularly distributed crypts. Cell proliferation, based on the observations of the presence of immature cells, mitotic figures and proliferating cell nuclear antigen reacting cells, was limited to the crypts after 8 weeks of age. The observation of bands of epithelial cells showing apoptotic and necrotic changes, suggested the existence of extrusion zones, where effete cells were eliminated by both shedding and phagocytosis. In the proximal intestine of adult common wolffish, increasing amounts of lipids were observed from the upper part of the crypts to the surface epithelium, probably reflecting an increased maturation of epithelial cells. [ABSTRACT FROM AUTHOR]

Tolerance, growth, ionic and osmotic response and gill enzymatic activity adjustments (Na+K+ATPase, COX, CS, PK and LDH) of Atlantic wolffish (Anarhichas lupus) exposed to different salinities (0‰, 7‰, 14‰, 21‰, 28‰ and 35‰) were examined. Direct transfer from seawater (SW) to freshwater (FW) of 0+ juveniles situated the L50 for salinity tolerance between 5‰ and 6‰. The data from prolonged exposure to various salinities indicate efficient homeostatic control in Atlantic wolffish A. lupus and improved growth performance at 14‰ compared to 28‰ after 70 days (calculated growth trajectories in length and in weight). The latter is linked to indications of reduced metabolic costs of ion regulation, i.e. significantly reduced Na+K+ATPase and LDH activity at 14‰ compared to 28‰ (Na+K+ATPase: 5.67±1.41 compared to 7.27±1.23 and 5.44±0.86 compared to 6.86±1.34 U/mg protein at weeks 14 and 19, respectively, p=0.05 and 0.026, respectively; LDH: 10.4±2.14 compared to 12.39±2.02 U/mg protein at week 14 and 12.46±1.34 compared to 17.17±2.67 U/mg protein for LDH, p=0.026 and 0.008, respectively). A strong positive relationship between Na+K+ATPase, LDH and PK activity was also observed [log y=1.107log LDH-0.914, p=0.0000, r2=0.46 (n=33) at weeks 14 and 19 and with PK (n=18) at week 19, log y=1.143 log PK-0.595, p=0.001, r2=0.497]. This indicates that from week 14 onward, the activity of branchial Na+K+ATPase is coupled to adjustments in the level of activity of the glycolytic enzymes. Our results indicate that Atlantic wolffish is a strong osmoregulator that demonstrates haloplasticity which enables cultivation of this species at reduced salinities with expected benefits in productivity. [Copyright &y& Elsevier]