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Anarhichas lupus is a boreo-Arctic species with biological characteristics often associated with vulnerability to over-exploitation. Although not commercially targeted in the North Sea, A. lupus is a bycatch species in mixed demersal fisheries. Here we provide an overview of the status of A. lupus in the North Sea, as observed from commercial landings and fishery-independent trawl survey data. A. lupus was once common across much of the central and northern North Sea but, since the 1980s, have declined in abundance, demographic characteristics (reduced size) and geographical range, with the shallower and more southerly parts of its range most impacted. A. lupus is still relatively frequent in the northern North Sea, where fishing intensity, though decreasing, is high. Bycatch through fishing remains a potential threat and, considering the likely impacts of predicted climate change on cold-water species, risks of further regional depletion and/or range contraction remain. Whether or not A. lupus is able to re-establish viable populations in former habitat in UK coastal waters is unknown. Given the lack of data, the precautionary principle would suggest that manageable pressures be minimised where the species and its habitat are at risk of further impacts, and more regular assessments of population status be undertaken. This article is protected by copyright. All rights reserved.

Simple Summary Spotted wolffish, a cold-water fish species, is a high potential candidate marine fish species for the diversification of the aquaculture sector in Norway, Canada, and Iceland. A review of the state of advancement of all aspects of its reproduction is proposed. Species-specific life-history and reproduction traits are discussed in parallel with relevant information originating from past R&D activities and the current state of knowledge regarding rearing environmental conditions and practices possibly affecting broodstock performances. Abstract The first artificially fertilized spotted wolffish (Anarhichas minor) eggs hatched in Norway in the mid-1990s as this species was considered by Norwegian authorities to be a top candidate species for cold-water aquaculture in the North Atlantic regions. Previous research conducted in Norway (since 1992) and Canada (since 2000), focused on identifying key biological parameters for spotted wolffish cultivation which led, respectively, to the rapid establishment of a full commercial production line in northern Norway, while Québec (Canada) is witnessing its first privately driven initiative to establish commercial production of spotted wolffish on its territory. The control of reproduction can be viewed as a major requirement to achieve the development of performant strains using genetic selection tools and/or all-year-round production to bring about maximal productivity and synchronization among a given captive population. Although the basic reproduction aspects are more understood and controlled there are still some challenges remaining involving broodstock and upscaling of operations that limit the achievement of a standardized production at the commercial level. Quality of gametes is still considered a major constraint and it can be affected by multiple factors including nutrition, environmental conditions, handling practices, and welfare status. Internal insemination/fertilization and the protracted incubation period are challenging as well as the establishment of a health monitoring program to secure large-scale operations. The profound progress achieved in the control of reproduction, sperm handling, and cryopreservation methods for this species is presented and discussed. In this review, we also go into detail over the full range of up-to-date cultivation practices involving broodstock and identify areas that could benefit from additional research efforts (i.e., broodstock nutrition, health and welfare, scaling-up egg and larval production, genetics, and development of selective breeding programs).

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 (2 (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.

The first record of the juvenile northern wolffish Anarhichas denticulatus was reported 570 km away from the nearest border of the species natural habitat near the island of Jan Mayen, on the continental slope of Northeast Greenland. Also original and published data on the occurrence of juvenile northern wolffish in the European Arctic and North Atlantic are presented.

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

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.

Stomach contents of major commercial fish species in the Barents Sea (cod Gadus mohrua, had-dock Melanogrammus aeglefinus, and striped catfish Anarhichas minor) include the soft parts of large bivalvians—serripes Serripes groenlandicus and Iceland scallop Chlamys islandica. The remains of serripes in the stomachs of fish are represented by muscular legs, while those of scallop by muscle and gonads. It is assumed that fish are likely to tear the soft parts of serripes during movement of a mollusk on the ground. Fish can consume the body of scallops only as scallop processing wastes or after shell crushing by fishing gear at bottom trawling and dredging.

According to long-term materials (1978–2012) of bottom and pelagic trawl surveys, the distribution and some features of biology of pelagic juveniles and adult individuals of Bering wolffish Anarhichas orientalis off the coasts of Sakhalin and the Kuril Islands are considered. Maximum sizes and age of wolffish are 113 cm, 10.8 kg, and 14 years. It is shown that the seasonal dynamics of distribution and numbers of pelagic juveniles off the Sea of Okhotsk coasts of southern Sakhalin is closely related to the regime of water warming. It is suggested that considerable variability of size-weight indices of juveniles at the beginning of summer is determined by extension of the dates of spawning of wolffish off the coasts of Sakhalin and the presence of fish from other areas of reproduction. Data on feeding of different size groups of wolffish fingerlings are presented.

In 2003, the Atlantic wolffish ( Anarhichas lupus ), spotted wolffish ( A. minor ), and northern wolffish ( A. denticulatus ) were placed on Schedule 1 of Canada's Species at Risk Act which afforded them protection against harm. Consequently, it is mandatory to release both northern and spotted wolffish and it has been recommended that live-release protocols also apply to Atlantic wolffish. Catches in trawls comprise a significant threat to recovery of all three wolffish species and the Grand Bank yellowtail flounder ( Limanda ferruginea ) otter trawl fishery overlaps the most persistent high concentrations of Atlantic wolffish in the western North Atlantic. As a result, the trawl fishery initiated a voluntary live-release program. The current study investigated the post-capture survival of Atlantic wolffish captured incidentally in the Grand Bank yellowtail flounder otter trawl fishery. Short-term survival was monitored for wolffish placed in holding tanks onboard commercial vessels as well as wolffish returned to the ocean floor in cages. High (92–100%) post-capture survival was demonstrated in Atlantic wolffish following net entrainment in commercial tows up to 2.5 h, haul back through a thermocline (range, 5.8 °C), and exposure to 5–13 °C air temperatures for up to 2 h. High post-capture survival and similarities among all three species of wolffish with regard to morphology, physiology, post-capture activity levels, and tag returns in previous studies suggest live-release programs will help to rebuild populations of all three wolffish species. From a conservation perspective, release of wolffish can only be effective if it does not interfere with reproduction. Uncertainties with regard to the reproductive success of egg guarding male wolffish when returned to the ocean are discussed.

This study examines the spatial distribution of three species of wolffish in the Gulf of St. Lawrence on the basis of trawl surveys. A standardized method is proposed to assess species–habitat associations for the purpose of management and recovery of endangered marine species. Catch data (presence/absence in trawl sets) and landscape and environmental characteristics of the sea floor were aggregated using a common grid (100 km2 cells), and species–habitat relationships were explored using geospatial tools. Relative occurrence was lower and area of occupancy and concentration were much smaller for the northern wolffish (Anarhichas denticulatus) than for the spotted wolffish (Anarhichas minor), with the striped wolffish (Anarhichas lupus) being most widespread. Significant relationships were observed between values of the local spatial autocorrelation Gi* statistic and habitat descriptors for each of the three species. Hot spots for spotted and striped wolffish occurred in areas where a greater diversity of relief and habitats was found. They were associated with intermediate depths, coarse sediments and rock outcrops, and lower salinities and temperatures than for northern wolffish. Northern wolffish appeared to be associated mainly with the deep water sloped habitat bordering deep channels, whereas spotted and striped wolffish both concentrated most intensively into neighbouring deep water shelf habitats and relatively cold shallow to mid-depth shelf habitats of the northern Gulf. The RDA analysis indicated a significant relationship between Gi* scores of the three species and environmental variables. The model explained 52% of the variability in the data; northern wolffish showed a distinct relationship compared with the two other species. The conservation of marine species and protection of their habitats pose a major challenge given the limited amount of information typically available on rare species and the scale and complexity of marine processes that affect those species. The broad-scale approach presented here allows the provision of advice on important habitats on the basis of the best available knowledge. Copyright © 2013 Her Majesty the Queen in Right of Canada

Pampoulie, C., Skirnisdóttir, S., Daníelsdóttir, A. K., and Gunnarsson, Á. 2012. Genetic structure of the Atlantic wolffish (Anarhichas lupus L.) at Icelandic fishing grounds: another evidence of panmixia in Iceland? – ICES Journal of Marine Science, 69: 508–515. The stock structure of the Atlantic wolffish was investigated at Icelandic fishing grounds, using 16 microsatellite loci. Despite the potential of the Atlantic wolffish to exhibit genetic structure (lack of eggs/larval dispersal and adults are sedentary), none of the genetic tests applied in this study detected significant genetic differentiation among the contemporary samples as well as among the contemporary and archived samples. The results of this study therefore suggested a lack of genetic structure among the populations of Atlantic wolffish in Icelandic waters and temporal stability over a period of ∼10 years. These results are discussed in terms of biological characteristics of Atlantic wolffish, recent isolation of populations, and their application to sustainable fisheries management issues.

The gut contents of 1000 common wolffish (Anarhichas lupus L.) from north-Norwegian coastal areas and two open sea localities in the Barents Sea, sampled between March 1989 and September 1993, were quantified and categorized. The material from the two areas with seasonally most abundant fish samples (west-Finnmark and Troms) were further analysed. More than 96 different prey species were found in the wolffish gut content, 31 of which had a frequency of occurrence higher than 2%, and only 12 species had a relative biomass importance higher than 2%. In terms of total weight, the most important prey categories were, in decreasing order: sea urchins, bivalves, crustaceans and gastropods. The diet varied with time and area, and was more pronounced with size of the fish. At the west-Finnmark stations, wolffish ate relatively more echinoderms, whereas at the Troms stations relatively more gastropods and bivalves were found in the guts. Medium-sized individuals mainly fed on echinoderms, crustaceans and ...

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.

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.

The first articially fertilized spotted wolffish eggs hatched only 10 years ago, and today the species is considered a very promising candidate species for cold water aquaculture in the North Atlantic. Recent research has focused on identifying key biological parameters in spotted wolffish aquaculture in order to establish a full production line for the species, and basic aspects of reproduction and larval development are now understood, controlled, and no longer limiting production.

The gelatinolytic activity in muscle from Atlantic cod (Gadus morhua), spotted wolffish (Anarhichas minor) and Atlantic salmon (Salmo salar) was studied using gelatin SDS-PAGE, gelatin affinity chromatography and enzyme inhibitors. These fish species are known to differ markedly in fillet softening and gaping post mortem. Atlantic cod, which is a promising species for cold water marine aquaculture, often shows such negative properties, particularly after being well fed. Gelatinolytic activity bands were present in all three species. Using gelatin chromatography and enzyme inhibitors, both serine proteinases and metalloproteinases were detected in wolffish and cod muscle, while only the latter were found in salmon muscle. Activation of the metalloproteinases by p-aminophenylmercuric acetate (APMA) resulted in a shift in activity from higher to lower molecular weight, as is known for mammalian matrix metalloproteinases. In all three species the molecular weight of the metalloproteinases was lowered from approximately 80 to about 70 kDa by activating with APMA. Copyright © 2003 Society of Chemical Industry

The ecological role of grey seals ( Halichoerus grypus ) as predators in Faroese waters was evaluated, based on reconstruction of the diet composition from stomach contents obtained from animals taken for scientific purposes in three main sampling areas during the summer in 1993-1995. Gadoids, sandeels ( Ammodytes sp.) and catfish ( Anarhichas lupus ) dominated the seal diet. Some regional variations were found in the grey seal diet, where gadoids and sandeels were most important in the Svinoy area, catfish and gadoids were most important in the Sandoy area, and sandeels and gadoids were most important in the Northwest area. Regional variations in diet may reflect variations in the abundance and availability of potential prey. Grey seals of different ages were found to have somewhat different feeding habits. Juveniles fed most frequently on sandeels, pre-adults fed on sandeels and saithe ( Pollachius virens ) and adults fed on cod ( Gadus morhua ) and catfish. Adults also fed on larger prey than the young...

The predatory behaviour of two species of juvenile wolffish (Anarhichas lupus and Anarhichas minor) was studied during a field campaign across a frontal area off western Greenland. The study focused on ontogenetic changes in prey-type and -size preference of the wolffish and their predatory impact on a cohabiting population of larval sand lance (Ammodytes sp.). Sampling took place along a cross-shelf transect at latitude 66°20' N, and the analysis is based on stomach contents of assembled wolffish (2–5 cm in length) and abundance estimates of plankton and fish. An ontogenetic change in wolffish prey preference was evident as a dietary shift from copepods and smaller amphipods to larger amphipods and fish larvae. The inclusion of fish larvae in the wolffish diet led to a marked increase in prey biomass, and fish larvae constituted up to 77% of diet biomass in the largest juveniles caught. Wolffish selectively targeted the smaller-sized part of the larval sand lance population; hence, larval vulnerability increased with decreasing size. Comparison between estimated predation rates and abundances of predator and prey indicated larval predation mortalities of up to 5% per day, with mortality peaking in the vicinity of a hydrographic front. Hence, findings suggest substantial predation pressure on larvae, primarily related to larval size and distribution.

To develop a compact farming system, a shallow raceway has been tested on five flatfish, three bottom-dwelling species and three open-water species. The main effort has been on turbot Scophthalmus maximus L., Atlantic halibut Hippoglossus hippoglossus L. and spotted wolffish Anarhichas minor (Olafsen). The system is almost a standard raceway, but with a very low water level (7 mm for fish at about 100 mg; 25 cm for fish above 2 kg). The system is a package with some crucial preconditions. These include high fish density (often 100–500 kg m− 3), no countercurrent in the levelled raceways (no jet currents), adjustment of water intake with the most remote fish in mind and feeding with floating pellets. Self-cleaning is easily obtained in the system. The system has been tested for a wide size range of raceways (0.07–80 m2) and fish sizes (2 mg to 10 kg), normally with growth and survival rates as good as with traditional rearing systems. There seems to be a ‘learning window’; the earlier the fish are introduced to shallow raceways, the better they perform. The results indicate that a variety of fish species can be produced in shallow raceways; these can be stacked in racks, which facilitate re-use of water from level to level. A very compact and cost-effective farming system will be the outcome.

The spotted wolffish Anarhichas minor (Olafsen), with its rich and tasty fillets, popular skin and high growth rates in captivity, is a promising candidate for cold-water aquaculture. We have established a production line for the wolffish during 5 years of active research on the biology of the species. Our broodstock, sampled from the Barents Sea, has mainly spawned during autumn. The females must be stripped as soon as possible after ovulation. The best egg batches have shown c. 100% fertilization and survival rates between 60% and 80% during the 800- to 960-daydegrees-long incubation period. Rearing temperatures of 6 °C, 8 °C, ambient and decreasing temperatures have turned out to be satisfactory for survival. Treatment with 150 p.p.m. glutardialdehyde twice a month is recommended to control microorganism growth on eggs. Premature hatching has been a problem in individual egg batches; the reasons are not fully understood. Normally hatched individuals are ≈ 22 mm long and well developed, with a small yolk sac, which is completely resorbed after about 4 weeks at 6–8 °C. The fry have been successfully start fed on formulated feed as well as Artemia. Highest early growth rates have been noted at 8 °C, but overall survival was best at 6 °C. On-growth of spotted wolffish juveniles fed formulated dry floating feed at low temperatures in shallow raceways has been promising. After 2, 3 and 4 years, the mean weights of the first generation produced in aquaculture were 0.7, 2.7 and 5.1 kg respectively. These individuals now make up the broodstock at a recently established commercial production facility.

The gyrodactylid monogeneans Gyrodactylus anarhichatis n. sp. and G. microanchoratus n. sp. are reported from the skin and fins of wild Atlantic wolf-fish Anarhichas lupus L. caught off the coast of northern Norway. G. anarhichatis n. sp. is also reported from farmed Atlantic wolf-fish and spotted wolf-fish A. minor Olafsen. G. anarhichatis n. sp. most closely resembles G. corti Mizelle & Kritsky, 1967, but is also similar to G. perlucidus Bychowsky & Poljansky, 1953 and G. errabundus Malmberg, 1970, while G. microanchoratus n. sp. differs from most other Gyrodactylus spp. by having marginal hooks longer than anchors and a peculiar lump on the marginal hook sickle toe pointing towards the sickle point.

The use of behavioural observations on marine fish larvae has a long history and has added considerable depth to our understanding of the ecological adaptations of larval fish. In marine fish larviculture we are trying to domesticate wild animals. Behavioural observation, in conjunction with growth and survival information, is a powerful tool for understanding the behavioural adaptations of larvae. This paper reports on the results of experiments conducted on the first-feeding of two species of marine larvae. Results of experiments carried out on lumpfish ( Cyclopterus lumpus ) fed the same density of live prey in pulses (twice or three times/day) or continuously, demonstrated that growth and feeding behaviour was significantly higher in the pulse treatments. A second set of experiments was performed on weaning of Atlantic wolffish ( Anarhichas lupus ) larvae. Live prey and pelleted food were offered to larvae from the onset of first-feeding. Observations on larvae indicated that over the first few weeks, larvae fed mostly on live prey with some pellet feeding. This pattern changed as larvae grew and by eight weeks larvae fed mostly on pelleted feed. In this example, the behaviour of the larvae provided a schedule which could be used to wean wolffish from live prey to pellet food. Using this information, improvements of the rearing protocols of these species may now be made.

Interest in the cultivation of wolffish arose in recent years due to their high-quality meat and fast growth in captivity. In wolffish, an almost juvenile organism, more than 20 mm long, hatches from the egg and can be fed dry pellets just after that. This makes the technology for wolffish breeding much simpler than for other marine fishes, even salmonids. This paper is devoted to common wolffish. Anarhichas lupus L., as the captive breeding of this species has been studied most completely. Experience with broodstock management, insemination, incubation of eggs, start feeding, and growth of rearing juveniles until maturation is described, based mainly on investigations made in Norway and in the Russian Federation. The conditions for obtaining maximum production in the shortest time are assessed. Prospects for using wolffish in aquaculture are briefly discussed.

Female maturation and egg quality of common wolffish, Anarhichas lupus L., from a broodstock were followed during the breeding season of 1993–1994. The results are compared with the data obtained for the 1992–1993 breeding season. The water temperature was lower in 1993–1994 than in 1992–1993; it reached 10–12 °C and 12–14 °C respectively before the beginning of the breeding seasons. Thirty-five females, 76% of those that spawned in 1992–1993, matured and released ovulated eggs again in 1993–1994. The time of final maturation and ovulation of eggs in 1993–1994 was similar to that in 1992–1993. Egg fertility increased in 1993–1994: 69% of first and repeat spawners had high proportions (90–100%) of normally cleaved eggs. Only 6.4% of females had such proportions in 1992–1993. Increased egg fertility was accompanied by fewer ovulated but resorbed eggs and larger egg diameter. The results suggest that for normal egg maturation females must be kept at a temperature below 10 °C for at least 4 months before ovulation.

The objective of the present study was to evaluate the effect of fish meal quality on growth, feed conversion and protein utilization in common wolffish. Anarhichas lupus L. The study involved comparison between low-temperature-processed (Norse-LT) and regular fish meal (NorSeaMink) included in dry pellets. Results obtained for these dry feeds were compared with those obtained using moist feed containing squid mantle. The results show better growth rate, feed conversion factor, protein efficiency rate, (PER) and productive protein values (PPVs), when using low-temperature-processed meals compared with regular fish meals in feed to wolffish. No specific differences were found in growth rate and feed conversion factor between fish fed diets containing low-temperature-processed meal or squid mantle. Whole body lipid content was highly influenced by dietary content. No effect of dietary moisture content was demonstrated in this study.

A stock of mature common wolffish, Anarhichas lupus L., were kept in tanks at the surface temperature in the sea and at a lowered temperature. At temperatures of 5–8dC in August and September all females matured. The fertilization rate of the eggs was studied in relation to various aspects of the fertilization procedure including sperm concentration, the duration of the contact of eggs with the sperm and the time of exposure of the gametes outside of the body of spawners. The maximum fertilization rate was attained at sperm concentrations not less than 1.0 times 106 per ml and when eggs were exposed to sperm for 1–2h. Fertilization of eggs in a narrow cylindrical vessel improved the efficiency of fertilization, with rates of up to 80–95%. Features of the fertilization of eggs of the wolffish are discussed in relation to the reproductive biology of the species.

The spatial and temporal distribution patterns of the Atlantic wolffish (Anarhichas lupus) from the Gulf of Maine-Georges Bank region were examined based on bottom trawl survey data from 1963 to 1989. Age composition, growth and food habits were also evaluated from 1983 to 1989. Catches of wolffish were distributed throughout the region, but highest concentrations occurred along the 100 m depth contour of the Gulf of Maine-Georges Bank. Statistical analyses of the depth occurrences revealed a seasonal shift in depth distribution from shallow water ( 50 cm) wolffish migrate to these shallow waters in spring and return to deeper waters in autumn. The oldest wolffish aged was 22 years. Mean length-at-age ranged from 4.7 cm total length for age 0 to 98.0 cm total length for age 22 in spring. Growth was modelled best by the Gompertz function. Bivalve molluscs (primarily Placopecten magellanicus) dominated the diet, followed by echinoderms, gastropods and decapods. Introduction The Atlantic wolffish (Anarhichas lupus) is a commercially important, cold water species found on both sides of the North Atlantic. In the Northwest Atlantic, its distribution extends from off Greenland to the Nantucket Shoals off the eastern United States (Jonsson, 1982). It is typically captured incidental to fishing operations directed toward other benthic species in this region. Commercial landings in USA territorial waters are from the Gulf of Maine and Georges Bank (NAFO Subarea 5), where the total USA nominal catch increased from 200 tons in 1970 to 1 200 tons in 1983 and have since declined to 500 tons (NMFS/NEFC, 1991). Additionally, National Marine Fisheries Service (NMFS), Northeast Fisheries Center, Woods Hole, Massachusetts, bottom trawl surveys indicate a long-term decline in relative abundance since the 1970s (NMFS/NEFC, 1991). Such information suggests that the Atlantic wolffish population of the Gulf of Maine-Georges Bank may be overexploited. However, currently there is no fishery management plan implemented to control fishing mortality on this species. Data on population biology and dynamics of exploited species are essential for proper management strategies. Past research concerning the biology of the Atlantic wolffish has included studies on food habits (Jonsson, 1982; Albikovskaya, 1983; Templeman, 1985; Hawkins and Angus, 1986), distribution and migratory patterns (Albikovskaya, 1982; Jonsson, 1982; Templeman, 1984), reproductive behaviour (Keats et al., 1985), age and growth (Jonsson, 1982) and sexual maturity and fecundity (Templeman, 1986) from Icelandic to Nova Scotian waters. Only descriptive data on depth distribution, food habits and breeding habits (Bigelow and Schroeder, 1953) are available for fishes in United States territorial waters. This study was undertaken to document trends in spatial and temporal distribution patterns based on bottom trawl survey data, and to evaluate quantitatively age, growth and food habits of Atlantic wolffish from the Gulf of MaineGeorges Bank region. Materials and Methods Data used for the spatial and temporal distribution analyses were collected from 1963 to 1989 in the Gulf of Maine-Georges Bank region by NMFS in a synoptic bottom trawl survey. The survey was based on a stratified-random sampling design for continental shelf waters >27 m in depth, partitioned into strata of unequal area based on depth and geographic location (Grosslein, 1969; Azarovitz, 1981). Prior to 1968, sampling was conducted only in autumn. A spring survey was added to the annual schedule in 1968. Sampling effort was expanded in 1972 to include the nearshore waters between 5 and 27 m depth. Sampling during spring and autumn J. Northw. Atl. Fish. Sci., Vol. 13: 53–61 54 J. Northw. Atl. Fish. Sci., Vol. 13, 1992 occurred generally in March to May and September to November, respectively. Sampling stations were randomly selected within each stratum and effort (number of stations) allocated in rough proportion to stratum area. At each station, a # 36 or # 41 Yankee otter trawl with a 1.25 cm stretched mesh codend liner was towed at approximately 3.5 knots for 30 min; bottom depth and near-bottom temperature data were also recorded (Azarovitz, 1981). Changes in spatial distribution between spring and autumn were examined for the 1963–89 survey period. Depth of occurrences, weighted by the number of wolffish captured in each tow, were compared between seasons using Kruskal-Wallis nonparametric ANOVA (Gibbons, 1976). Further, length frequencies were examined by depth ranges for evidence of a seasonal reproductive migration noted by Keats et al. (1986). Due to the low numbers of wolffish captured annually, data from all survey years were combined for these analyses. Age and growth Wolffish were collected opportunistically for the age, growth and food habits analyses from autumn 1983 to spring 1989. Individuals captured in the otter trawl were weighed collectively to the nearest 0.1 kg, measured individually (total length; TL) to the nearest cm, and sexed. The head and entire digestive tract from the esophagus to rectal sphincter were then removed, stored in plastic bags, and frozen. Occasionally, small wolffish (

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.

The most promising new species for fish farming in Norwegian waters are the marine species Atlantic halibut ( Hippoglossus hippoglossus ), Atlantic cod ( Gadus morhua ), ocean wolf fish ( Anarhichas lupus ), and spotted wold fish ( A. minor ). The main constraints in the commercialization of these species are primarily related to mass rearing of fry. This paper gives a short review of the restrictions on mass rearing of cold-water marine fish fry and the main results from recent research on these four species in broodstock handling, egg and larval rearing.

The diet of common wolffish Anarhichas lupus from the North Sea is described, from a total of 143 wolffish stomachs, of which 112 contained food. The main prey were crustaceans and molluscs, together representing almost 70% of diet by relative frequency of occurrence in stomachs. Wolffish >55 cm preferred polychaetes and gastropods while wolffish

Three groups of newly hatched wolffish larvae (one group in the Faeroe Islands and two groups in Norway) were start-fed on commercial dry pellets. Survival rates were between 10.5 and 53.7% during the first 108 days after hatching. The specific growth rate varied between 2.00 and 3.34%/day in the same period. A high mortality was observed between 20 and 40 days after hatching. A maximum specific growth rate (3.0–3.6) was observed 100–150 days after hatching, followed by a decrease to 0.4 and 0.8 at the end of the experiment. High mortality was observed in one of the groups during the juvenile stage, caused by heavy infection by the ectoparasite Trichodina sp. The behaviour of both larvae and juveniles was studied. The larvae spent most time in midwater while juveniles were most active around feeding time and spend most of the day lying on the bottom of the tanks. Cannibalism was observed occasionally and only among larval fishes. No cannibalism was observed in the Faeroe Island fish which were continually fed at 10 min intervals throughout 24 h.

Lead concentrations in spotted wolffish (Anarhichas minor) collected from the vicinity of a sphalerite–galena mine and an ore concentration plant in West Greenland have been measured through a period of 2 yr before and 4 yr after mining operations started. Lead levels increased significantly since mining started, and accumulation takes place in liver and kidney, not in muscle tissue. The increased lead levels are not a risk to public health. Small fish have higher lead concentrations than larger ones. Key words: wolffish, arctic, liver, muscle, kidney, lead, zinc–lead mining

The time trend in the DDT contamination of the marine environment in a Norwegian fjord where DDT has been used extensively in local fruitgrowing, has been studied for 10 years following the DDT ban. Residues of ∑-DDT (p,p′-DDT + 1.11p,p′-DDE + 1.11p,p′-TDE (DDD). The factor 1.11 is added to correct for the lower molecular weight) in 225 liver samples of seven sedentary fish species showed a downward trend during the period 1972 to 1982. The decrease in ∑-DDT illustrates the effectiveness of the 1970 ban on its use in Norway. The highest 1982 mean level of ∑-DDT was found in the liver of cod (Gadus morhua) (1237 μg/kg, wet weight, range 191–3845 μg/kg) and was about 1/3 of the corresponding 1972 residue level. The decrease of ∑-DDT was less rapid in the liver of the cod and the haddock (Melanogrammus aeglefinus) (half-life time 5.0 years with a 95% confidence limit of 2.3 years) than in the fish species sea scorpion (Myoxocephalus scorpius), cat fish (Anarhichas lupus), ballan wrasse (Labrus berggylta) and lemon sole (Microstomus kitt) (half-life time 2.6 years with a 95% confidence limit of 0.8 years). Cod and haddock have a substantially higher fat content in the liver compared to the other fish species. A half-life time of 3–5 years for biologically available DDT residues is suggested to apply generally to Nordic marine environments. Unmetabolized DDT constitute a smaller proportion of ∑-DDT in 1982 than in the previous years. However, a great variation between species and individuals was found. PCB contamination in the fish was low, and reflect a Norwegian baseline contamination. The highest 1982 mean level of PCB residues was found in cod liver (454 μg/kg, wet weight, range 175–1073 μg/kg) which was about 1/3 of the 1972 value. The levels of ∑-DDT and PCBs were correlated to fish weight in the cod. These two types of residues were mutually correlated over all weights. No correlation was found between the fat content of the liver and the residue level of organochlorine chemicals within the species. Only low levels of contamination by hexachlorobenzene (HCB), α-, γ-HCH and ∑-chlordane were found in 1982. The highest levels were found in cod liver (HCB 6–26; γ-HCH 6–16; α-HCH 4–140;∑-chlordane = oxychlordane + transnonachlor 38–220 μg/kg, wet weight). The levels of organochlorines in fish from a Norwegian fjord were generally low and not believed to have any toxicological implications.

From collections of Atlantic wolffish in the Northwest Atlantic (West Greenland to the Scotian Shelf) during 1950-67, mean vertebral counts increased gradually from the colder northern to the warmer southern areas (74.19 off Labrador to 75.29 on the southern Scotian Shelf). This is the reverse of the usual pattern in other fishes of the region with pelagic eggs. The pattern for mean dorsal fin-ray counts was similar, but the area coverage and sample sizes were less extensive and the differences were less significant than in the vertebral data. The overall ranges in counts were 72-78 for vertebrae and 71-77 for dorsal fin-rays. Dorsal fin-ray and vertebral numbers were moderately well correlated in a limited number of specimens.

The reproductive season, the sex that provides parental care, and the relationship of feeding with reproduction are reported for Atlantic wolffish and ocean pout in eastern Newfoundland. Both species move into shallow water in the spring, pair during the summer, and spawn in holes under and between boulders during the autumn. Apparently, male Atlantic wolffish provide solitary parental care of the eggs, while in ocean pout females provide this function. Feeding is reduced for females and probably males of both species as the gonads approach maximum size. After pair formation, male ocean pout reduce feeding; male Atlantic wolffish do so to a lesser degree. Male Atlantic wolffish and female ocean pout feed little or not at all while guarding egg masses.

Tagging of 398 Atlantic wolffish, Anarhichas lupus, 81 spotted wolffish, A. minor, and 101 northern wolffish, A. denticulatus, with Petersen disc tags in the Newfoundland area during 1962-66 yielded 5.0, 7.4 and 3.0% returns respectively. Recapture information indicates that migrations are generally short but some rather long migrations were noted. The rate of recapture of Atlantic wolfish declined rapidly from 15.4% for coastal taggings to 6.7% for offshore taggings except Flemish Cap and to 1.1% for Flemish Cap tagging. Depths of recapture of Atlantic wolffish ranged from 20 to 476 m. Fig. 1. Map of the study area with place names mentioned in the text. Materials and Methods Because of the lack of information on movements of wolffishes in eastern Canadian waters, some tagging of the three species off Newfoundland (Fig. 1) was carried out during 1962:66.

The diet of the Atlantic wolffish was studied by examining the contents of the gastrointestinal tracts of 90 individuals collected from the sea urchin dominated rocky subtidal in eastern Newfoundland. Green sea urchins comprised 75% of the overall diet by weight. Horse mussels ranked second but comprised only 9.5% of the diet. The remainder of the diet consisted of several species of invertebrates and fish. The average (over the whole season) wolffish contained 120 g of urchins, equivalent to the biomass of urchins on 0.23 m2 in the middle of the urchin-dominated zone. During April–September, prior to breeding, the average male wolffish contained 174 g of urchins, and the average female contained 85 g of urchins, biomass values representing, respectively, 0.33 and 0.16 m2. Assuming that the contents of the gastrointestinal tract turn over every 3 days, it was calculated that during May through August each wolffish consumes on average 5.29 kg of urchins (males, 7.09 kg; females, 3.50 kg). Based on these figures, a density of 1 wolffish pair per 20 m2 would be required to consume the mean biomass (532 g m−2) of urchins present in the urchin-dominated zone in 1 year.

Highlights • A novel myxosporean species, Kudoa islandica, is described. • It is prevalent in lumpfish and Atlantic and spotted wolffish. • It causes extensive post mortem myoliquefaction. • It was a major factor in the closure of spotted wolffish farming in Iceland. • It infects fish from different taxonomic orders and could be a concern in aquaculture., In the early 2000s, experimental rearing of spotted wolffish, Anarhichas minor, was started in Iceland. Health surveillance, carried out at regular intervals during the rearing period, revealed persistent and highly prevalent Kudoa infections of fish muscles which caused great financial losses due to post mortem myoliquefaction. In addition, during the traditional process of drying and smoking wild Atlantic lumpfish, Cyclopterus lumpus, the muscles from some fish almost completely disappear and the fish have to be discarded. To describe the etiological agent responsible for these conditions, spotted wolffish, Atlantic wolffish Anarhichas lupus, northern wolffish Anarhichas denticulatus and Atlantic lumpfish were caught off the Icelandic coast and examined for the presence of Kudoa. We describe a novel myxosporean, Kudoa islandica n. sp., using morphological and molecular data, and show with histopathology that it causes extensive myoliquefaction in three different wild fish hosts, which all are commercially valuable species in Iceland. Although some spore dimensions varied significantly between fish species, the molecular analyses showed that the same parasite was responsible for infection in all fish. The northern wolffish was not found to be infected. Although robustly placed in the Kudoa clade in phylogenetic analyses, K. islandica was phylogenetically distinct from other kudoids. A single myxosporean, K. islandica, is responsible for the infections in the somatic muscles of lumpfish and wolffish, causing extensive post mortem myoliquefaction. This myxosporean is likely to infect other fish species and it is important to study its life cycle in order to evaluate any threat to salmonid culture via the use of lumpfish as a biocontrol for sea lice.

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