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Mature common wolffish, Anarhichas lupus L., previously held at 8°C for several months, were exposed to 4, 8 or 12°C throughout the breeding season (November-January). Regardless of temperature, some females ovulated in early-November, but thereafter ovulation was delayed in the 8 and 12°C groups compared with the 4°C group. Temperature experienced by the adult fish also affected egg development and survival even though eggs were incubated at a common temperature of 6°C. The percentages of normally cleaved eggs (at the 32-cell stage) and egg survival to the eyed stage were significantly lower in the 12°C group (8%) than in the 4°C (73%) and 8°C (48%) groups. The differences in egg survival were also significant between the 4 and 8°C groups. Egg survival was also influenced by the length of time the broodfish had been exposed to the different temperatures: at 4 and 12°C there were significant positive and negative relationships, respectively, between egg survival and the number of days for which the female had been exposed to the given temperature prior to ovulation. Temperature experienced by the female did not affect egg size, relative egg weight, fertilization rate, relative fecundity or the number of ovulating individuals. The results indicate that both the timing of ovulation and egg quality of common wolffish are affected by the temperature experienced during the breeding season.

Eggs of spotted wolffish (Anarhichas minor Olafsen)were incubated at constant 4, 6 and 8 °C, and disinfected withglutaric dialdehyde (150 p.p.m. for 5 min) once ortwice a month during two thirds of the incubation period, to prevent growth ofmicroorganisms. Hatching of apparently normal larvae started earlier when eggswere disinfected twice a month compared to once a month at all incubationtemperature regimes. The time to 50% hatch was 900 and 920 day-degrees (16 and16,5 weeks) at 8 °C, 835 and 880 day-degrees (20 and 21 weeks)at 6 °C and 725 and 800 day-degrees (26 and 28,5 weeks) at 4°C, in the egg groups disinfected twice or once a month,respectively. The best survival until hatching was noted when eggs weredisinfected twice a month and incubated at 6 and 8 °C.Survivalwas very low at 4 °C. Prematurely hatched larvae wereregistered in all egg groups disinfected twice a month and the highestfrequencywas noted in the 8 °C groups. The larval weight at normalhatching in the 6 and 8 °C groups was negatively correlatedwith incubation temperature and intervals of disinfection during the incubationperiod, but after 42 days feeding with live feed (unenrichedArtemia) the weights of the larvae were not significantlydifferent. The specific growth rates of the larvae from the eggs incubated at 6°C and 8 °C were 3.0% and 3.2%, respectively.The mean survival of larvae was between 88% and 96% at 42 days post-hatching.Young wolffish originating from the 6 °C incubation groupsshowed lowest mortality.

Summary Eleven bacterial strains were isolated from the gastrointestinal tract of four fish species, Atlantic salmon ( Salmo salar L.), Arctic charr ( Salvelinus alpinus L.), Atlantic cod ( Gadus morhua L.) and wolffish ( Anarhichas lupus L.). All the strains were Gram-positive rods, non-sporing, catalase and oxidase-negative, able to grow at pH 9.0 but not on acetate containing media (pH ≤ 5.4), and were fermentative. They had a high content of oleic acid (18:1 n-9) in cellular lipid, and were found to belong to the genus Carnobacterium by phenotypic criteria. The eleven carnobacteria strains were further identified on the basis of 16S rDNA sequence analysis and AFLP TM fingerprinting.

The alimentary canal of laboratory-reared common wolffish (Anarhichas lupus L.) was studied using light and electron microscopy. In the oesophagus, a simple columnar microvillous epithelium with transport characteristics was observed in addition to the main striated squamous epithelium. An osmoregulatory function is proposed for the simple columnar epithelium, which was supported by wide, thin-walled vessels. In the stomach, a separate type of neck cells was observed leading into the acinar gastric glands, which morphologically consist of one cell type: chief cells. The intestine was divided into a proximal and distal segment by an intestinal valve. Pyloric caeca were not present. We propose that shallow, crypt-like structures in the intestinal mucosa are the sites of epithelial-cell proliferation in juveniles and adults. The length of microvilli decreased from approximately 4 microns in the cranial part of the proximal intestine, to 1.5 microns in the distal intestine. In the distal intestine, rod-shaped bacteria were observed between microvilli. An extensive system of thin-walled vessels was observed in the submucosa of juvenile and adult wolffish stomach and intestine. Eosinophilic granular cells were numerous in the perivascular connective tissue in the gastric and intestinal submucosa of adults and juveniles, but were not observed in larvae.

The von Bertalanffy growth parameters for common wolf-fish Anarhichas lupus in the North Sea were: male: L∞ = 111.2 cm, t 0 = -0.43 and K=0.12; and female: L∞=115.1 cm, t 0 = -0.39 and K=0.11, making this the fastest growing stock reported. Resting metabolic rates (RMR ± S.E.) and maximum metabolic rates (MMR S.E.) for six adult common wolf-fish (mean weight, 1.39 kg) at 5° C were 12.18 ± 1.6 mg O 2 kg -1 h -1 and 70.65 ± 7.63 mg O 2 kg -1 h -1 respectively, and at 10° C were 25.43 ± 1.31 mg O 2 kg -1 h -1 and 113.84 ± 16.26 mg O 2 kg -1 h -1 Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.

Atypical furunculosis caused by atypical Aeromonas salmonicida is an increasing problem in commercial halibut farming, and a potential problem in farming of spotted wolffish in Norway. Halibut, Hippoglossus hippoglossus L., and spotted wolffish, Anarhichas minor L., vaccinated with oil-emulsified vaccines against atypical furunculosis, demonstrated a relative percent survival (RPS) of approximately 90 when challenged with homologous isolates. Bath and aqueous injection vaccines failed to protect against disease when challenged 10 weeks post-vaccination. High antibody titres were produced in both species after vaccination with oil-emulsified vaccines, and the major antibody response were against A-layer, LPS and some minor outer membrane (OM) proteins.

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.

Temperature treatment of common wolffish Anarhichas lupus during vitellogenesis affected the time of final maturation; ovulation in fish held at 8 and 12° C from mid-April to October was about four and five weeks delayed, compared with a 4° C group. Fish in the 8° C group had significantly larger eggs than those in the 4° C and the 12° C groups, and a significantly higher egg production than fish in the 12° C group. Temperature treatment did not affect either fertilization rate or relative fecundity, but absolute fecundity was significantly lower in the 12° C group than the other groups due to poor growth of the fish at high temperature. This did not affect the numbers of spawning individuals. There was a trend towards lower egg survival to the eyed stage in the 12° C group compared to the 4 and 8° C groups, although the effect was not statistically significant. The results indicate that both the timing of final maturation and investment in ovarian growth in common wolffish are affected by temperature experienced during vitellogenesis.

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.

To assess the significance of metals in biota of the Barents Sea, preliminary information is presented for the concentrations of Cd, Pb, Hg, Ni, Cu and Zn in liver and muscle tissues of 15 marine fish species collected in the summer of 1994. Lead and Ni concentrations are below limits of detection (< 0.3 and 1.0 mg kg-1 dry wt.) in all tissues, as is Cd in muscle (< 0.10 mg kg-1). Generally, most of our results are within the reported literature range for various Arctic marine systems, especially regarding some commercially important species like cod and redfish, indicating that metal levels are not elevated. However, the interspecific variability is substantial and some remarkably high Cd levels (2.4 and 8.1 mg kg-1 dry wt.) in livers of Anarhichas species (catfish) and Raja fyllae (round skate) point to the problem of a general 'cadmium-anomaly' in polar marine waters, previously inferred from reported results for various pelagic and benthic invertebrates.

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 effects of temperature on the survival, growth rate and growth efficiency of larval and juvenile common wolffish, Anarhichas lupus L. were studied at 0–31 days and 9–12 months post-hatching, respectively. The influence of temperature regime during egg incubation on subsequent survival and growth was also examined. The fish were reared at constant water temperatures of 5, 8, 11 and 14°C, and all groups were fed dry pellets. At age 1 month, maximum growth rates were observed at 11 and 14°C. Growth rates and survival of early juveniles were dependent upon incubation history, high growth being obtained only if rearing temperature exceeded the temperature of egg incubation. In juveniles at age 9–12 months, the relationships between temperature and growth, and temperature and growth efficiency were parabolic: the optimum water temperatures for growth (Topt.G) and growth efficiency (Topt.GE) were 11°C and 9.7°C respectively. The growth rate and growth efficiency at these water temperatures were 0.9% day–1 and 0.45 g weight gain per g food offered, respectively. © Rapid Science Ltd. 1998

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.

The ontogeny of the axial skeleton, in particular the caudal skeleton, is described from embryos to adult specimens in common wolffish, Anarhichas lupus. The eggs were incubated at constant temperatures of 7.0, 11.0 and 13.0 °C. High egg mortality and structural changes in skeletal development (fusion of parts, absence of distal radials and most of dorsal and anal fin rays, abnormal neural arches and dorsal fin rays) were observed at 13 °C. The frequencies of some anomalies were lower at 11 °C than at 13 °C. The main reason of structural changes of the skeleton at high temperature is the breaking of normal correlations between developmental rates of some cartilaginous structures and other tissues and organs of the embryo. These data suggest an epigenetic mechanism of skeletal evolution.

L'ultrastructure du spermatozoide et la production de sperme ont ete observees chez le poisson-loup (Anarhichas lupus), une espece a fecondation interne, a partir d'un elevage. Le spermatozoide, arrive a maturite, a une tete allongee et un flagelle excentre, et un corps intermedaire comparativement bien developpe. La longueur moyenne de la tete du spermatozoide et du flagelle sont 3,3 et 21,2 μm respectivement. La taille des cellules du sperme est tres variable, due a la presence de spermatides et de spermatozoides degeneres. Chez la plupart des mâles, la production de sperme a ete observee tout au long de l'annee avec un pic d'abondance en decembre et en janvier. La production de sperme diminue a la fin de la saison de reproduction. La difference de volumes de l'ejaculat et du sperme entre mâles gardes sous deux cycles differents d'eclairement (18 h nuit: 6 h jour et inversement) n'etait pas significative. Les caracteristiques du sperme du poisson-loup sont comparees aux donnees bibliographiques d'autres poissons a fecondation interne et externe.

Vitellogenin (VTG) from spotted wolffish, Anarhichas minor, a candidate species for cold-water marine aquaculture, was purified by MgCl2/EDTA precipitation followed by a two-step chromatographic procedure. VTG had an apparent molecular mass of 470 kDa, as determined by gel filtration, and an amino acid composition similar to those of other teleosts. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of the purified VTG revealed a major band with a relative molecular weight of 166 kDa and some minor bands. Spotted wolffish VTG (sw-VTG) is relatively robust to in vitro degradation, as shown when samples of purified VTG and plasma from mature females subjected to various storage conditions or multiple freeze/thaw cycles were analyzed by Western blot. We developed an indirect competitive enzyme-linked immunosorbent assay (ELISA) using an antibody against Atlantic wolffish (Anarhichas lupus) VTG and purified sw-VTG. The ELISA had a detection limit of 6.7 ng/ml and a working range of 16.2–787.5 ng/ml, with intra- and inter-assay coefficients of variation ranging from 1.5 to 7.3 % and 7.1 to 14.3 %, respectively. The assay could distinguish males from immature females and discriminate maturing females at different stage of oocyte development. These results suggest that the sw-VTG ELISA would be useful in spotted wolffish aquaculture to determine sex and monitor female maturation.

The oxygen consumption (02) and ammonia excretion (N) of juvenile and adult common wolffish was measured in culture tanks in the laboratory. The oxygen consumption and ammonia excretion were affected by temperature (C), fish size and feeding rate. For juveniles (0.5 kg; 7C) the diel oxygen consumption rate varied between 37 and 62 mg O2 kg-1 h-1 and ammonia excretion between 2.3 and 5.7 mg N kg-1 h-1. The corresponding rates for adult fish (6.9 kg; 7C) were 29-44 mg O2 kg-1 h-1 and 1.2–3.1 mg N kg-1 h-1. The weight-specific oxygen consumption (mg O2 kg-1 h-1) was described by the following formulae: O2 (7C) = 0.17* W0.83 and O2 (12C) = 0.39 * W0.73 and the corresponding ammonia excretion (mg N kg-1 h-1) by: N(7C) = 0.024 W0.75 and N(12C) = 0.073 W0.60, where W is fish weight in g.

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.

Larvae of common wolYsh (Anarhichas lupus L.) obtained from eggs incubated at a constant temperature of 7.0)C had mean numbers of rays in the dorsal, anal, and caudal fins of 74.5, 46.4, and 23.8 respectively; those incubated at 11.0)C had 53.8, 25.7, and 25.2 rays, respectively. Several skeletal abnormalities, including fusion of parts and abnormal structure of neural arches in the pre-urostyle area, accompanied the reduction in numbers of dorsal and anal fin rays at 11)C. To test which period of embryonic development was critical for determining the final numbers of unpaired fin rays and skeletal abnormalities, the eggs were transferred from 7) Ct o 11 )C and back at diVerent stages. Determination of the final numbers of rays in the dorsal and anal fins and most of skeletal abnormalities occurred mainly between 50% vascularization of the yolk sac and the beginning of formation of rays in the caudal and pectoral fins. The final number of caudal fin rays was determined between the latter stage and formation of rays in the dorsal and anal fins. To reduce the egg incubation period and still obtain larvae without skeletal abnormalities, a temperature regime during embryonic development is suggested. ? 1996 International Council for the Exploration of the Sea

Wolffish, Anarhichas lupus L. has internal fertilization. The eggs are released into water before the beginning of cleavage and stick together in clutches. To develop methods for separating eggs for subsequent incubation, changes during egg swelling and egg shell hardening were observed. Uninseminated eggs did not swell in ovarian fluid, but a perivitelline space formed in sea water because of a partial cortical reaction. In inseminated eggs kept in ovarian fluid, a cortical reaction took place and swelling was caused by elevation of the yolk membrane. Shrinkage of the yolk and absorption of water were observed after inseminated eggs were placed in sea water. Eggs swelled in ovarian fluid diluted by less than 30% sea water showed abnormal cleavage during subsequent development. An effective method for preventing egg stickiness after fertilization was to distribute them in trays with stagnant sea water for at least 5-6 h. Milk was effective for loss of egg adhesiveness at 50% concentration, but some eggs cleaved abnormally and subsequent mortality was high. The influences of ovarian fluid and milk on initial egg development with respect to peculiarities of egg swelling are 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.

Larvae of the common wolffish. Anarhichas lupus L., hatched from artificially inseminated eggs incubated in the laboratory, were reared on live foods at temperatures ranging from 2 to 10oC. Temperatures over 8oC were too high for newly hatched larvae, but after rearing for 17 days at an average temperature of 6.5oC, the young could tolerate 11oC. The maximum growth rate was observed in the process of keeping of fish during the first 5 months of growing at a temperature gradually increasing up to 14oC. At an age of 577days the average weight of the young in two size groups was 160 and 248 g. A stocking density or five fish 1−1 is satisfactory for young at weight less than 0.2 g. Subsequent growth during 2 months at density of 3-4 fish 1−1 was delayed, compared with that at density of one fish1−1, and all fish reared at high density were infected by Trichodina sp. The growth rate in captivity is compared with that in nature.

The fatty acid compositions of vitellogenin and liver from cod (Gadus morhua), rainbow trout (Oncorhynchus mykiss), turbot (Scophthalmus maximus) and wolffish (Anarhichas lupus) were determined. Vitellogenin was isolated from plasma of estradiol-17β-treated fish by precipitation with EDTA-Mg2+ and distilled water or by high-performance ion-exchange chromatography. In all investigated species, vitellogenin contained 16–18% (w/w) lipid, in which polyunsaturated fatty acids, predominantly 20:5 (n-3) and 22:6 (n-3), comprised about 50% of the total fatty acids. The proportions of saturated, monounsaturated, polyunsaturated and (n-3) fatty acids in vitellogenin of the different species were generally similar, although the relative content of specific fatty acids was distinctive for each species. The distribution of fatty acids in total lipids of vitellogenin was highly consistent among individual females of each species. In contrast, liver fatty acid composition varied considerably, both within and between species. Altogether, the differences in the fatty acid composition of vitellogenin and liver from each species indicate that a specific selection of fatty acids occurs during the lipidation of vitellogenin.

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.

Field-caught fry of the common wolfish, Anarhichas lupus L., and the spotted wolffish, A. minor Olafsen, were reared on a commercial dry pellet. Both species experienced the same environmental conditions, including an annual fluctuation in temperature from 5·8 to 13·7°C. The spotted wolffish reached 1·58 kg in 2 years from hatching, more than four times the weight of common wolffish (0·37kg). Analysis showed that for both species the specific growth rate decreased with increasing fish size and increasing temperature. Estimates, based upon optimum conditions, indicate that the spotted wolffish would reach a total wet weight of 5 kg (

Maturation of females and ovulation of eggs of common wolffish, Anarhichas lupus L., were followed during the spawning season from 10 October 1992 to 28 July 1993. The broodstock was reared from larvae in the laboratory. Most females matured from the middle of December to the middle of March at water temperatures of 5.0–8.0°C. A total of 153 577 eggs from 47 females were stripped and artificially inseminated. Of these eggs, 70.6% were fertilized, but only 41.0% showed normal cleavage. Nine females had high proportions (more than 80%) of normally cleaved eggs. Fertilized but abnormally cleaved eggs were observed in almost all females, with an average proportion of 30%. There was no difference in quality of eggs obtained by internal and external artificial insemination or from females that demonstrated spawning behaviour and females without it. Survival of eggs from different females correlated to the proportion of normally cleaved eggs. The causes of poor egg quality are discussed as well as related morphology and size-frequency distribution of eggs.

Vitellogenin was purified from plasma of estradiol-17β-treated cod (Gadus morhua) rainbow trout (Oncorhynchus mykiss), turbot (Scophthalmus maximus), and wolffish (Anarhichas lupus) by precipitation with EDTA:Mg2+, distilled water, and high-performance ion-exchange chromatography. Vitellogenin of high purity was obtained by precipitation followed by chromatography, as evaluated by an homologous antiserum developed for each species. The instability of vitellogenin demanded consistent low temperature and the use of protease inhibitor before blood sampling. When the necessary precautions were taken, vitellogenin from rainbow trout, turbot, and wolffish eluted as one regular peak during chromatography. Cod vitellogenin eluted as two peaks and these demonstrated identical migration patterns on SDS-PAGE. The observed differences in stability between the four species suggest that isolation procedures should be modified according to the requirements for each species. Electrophoresis of plasma from treated fish revealed the presence of several smaller proteins, with a molecular mass around 50 kDa, that were considered to be vitelline envelope proteins. Other minor plasma proteins were immunoreactive to antisera, directed against vitellogenin and therefore judged to be fragments of degraded vitellogenin. © 1993 Wiley-Liss, Inc.

Mortality of artificially fertilized, laboratory incubated eggs of common wolffish,Anarhichas lupus L., was 100% within 2–3 weeks, at the gastrulation step. The eggs from batches with a high proportion of normally cleavaged eggs died later than the eggs from batches with a low proportion of such eggs. Light micrographs of egg shells showed ulceration of the outer layer and subsequent destruction of the inner layer of zona radiata, caused byFlexibacter sp. The bacterial infection provoked premature hatching at later stages of embryonal development. Treating eggs with glutaraldehyde at a concentration of 600 mg l−1 every third to fifth day during incubation prevented the mortality caused by bacteria.

The reproductive biology and spawning behaviour of the common wolffish ( Anarhichas lupus ) was studied in the laboratory, and various facilities were tested in order to make common wolffish spawn in captivity. Fish caught on the south and west coast of Norway spawned between the middle of October and the middle of February, with a peak around the turn of the year. There is no sexual dimorphism in common wolffish prior to maturation. Towards spawning the ripening female adopts a pronounced pot-bellied shape. The testis is small, on average only 0.11% of the total body weight of males, and there is little difference in the size of running-ripe and non-running testes. At most 1.5 ml of milt was stripped from a running male, and males were found to be running during most of the spawning season. Running males have a papilla on their urogenital pore which may serve as a copulatory organ. Morphological as well as behavioural evidence strongly suggests that the eggs of the common wolffish are fertilized internally, and that copulation takes place 8–15 h before spawning. No successful, natural spawning took place in the various facilities tested, ranging from small tanks (4 m 2 ) with single pairs to big basins (up to 1500 m 2 ) with many wolffish present. The common wolffish seems to have a complex reproductive behaviour which probably makes it difficult to obtain natural spawning on a regular basis in captivity. Procedures are suggested for artificial fertilization of common wolffish eggs.

Five groups of juvenile common wolffish were fed either moist or dry pellet feeds in indoor tanks. Two groups were given moist pellets differing in protein source, while three groups were given dry pellets having different contents of protein, fat and carbohydrate. Protein energy (PE/TE) in the feeds varied between 50 and 63%. Mortality was between 0 and 17.4% in the different groups during the 134 days of the experiment. The groups given dry pellets grew significantly faster (∼0.26 g day−1) than the groups fed moist pellets (∼0.15 g day−1), most likely caused by the lower carbohydrate content in the dry pellet. The hepatosomatic indices of the fish given dry pellets were significantly higher than those of the fish fed moist pellets. Fat and protein contents of the fillet, and fat content of the liver were lower in fish fed moist pellets than in those given dry pellets. Linear relationships were observed between the fat content in the feed and those in the liver and fillet.

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. (C) 2011 Elsevier Inc. All rights reserved.

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.

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 predatory impact of the American lobster Homarus americanus and the Atlantic wolffish Anarhichas lupus on the green sea urchin Strongylocentrotus droebachiensis was investigated in a multifactorial experiment. Both predators exhibited either Type 2 or Type 3 functional responses to increasing prey density, but the magnitude of the response differed for the two predators, and for different prey sizes. Predation on large (>20 mm ) sea urchins increased approximately three-fold, i.e., from 1.12 to 3.54 urchins·day −1 for wolffish, and from 0.35 to 0.97 urchins·day −1 for lobster, when prey density was increased sixfold, i.e., from 5 to 30 urchins·tank −1 . Although more urchins were killed at the highest density, the proportion of available urchins that were killed dropped by ≈50%. Predation on small (⪯20m) sea urchins was similar for both predators, increasing from ≈0.5 to ≈1.9 urchins·day −1 with increased prey density. In the lobster treatment, a rock crab, Cancer irroratus Say, was included as alternative prey. The lobsters killed 5.78% of the total number of available rock crabs, and 5.01% of the total number of available urchins, but lobster predation on urchins was nearly halved in replicates where the crab was killed. Experimental factors other than prey density and prey size, i.e., season; availability of food and physical refuges for the prey, and whether the prey had been fed or starved prior to the experiment , had no significant effects on the predation rates of either predator. These results are consistent with the hypothesis that green sea urchin outbreaks may be triggered by reductions in predation pressure. There was no evidence of significantly increased predation on morbid sea urchins although ≈1% of the experimental sea urchin population exhibited symptoms of amoeboid, Paramoeba invadens (Jones), disease.

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 genus Neophasis is defined. The taxonomic status of the genus is discussed in the light of its life-cycle, hosts and cercarial and adult morphology. It is considered to be closest to the family Acanthocolpidae due to the utilisation of a fish second intermediate host, the form of the cercarial excretory system and, in the adult, the presence of a uterine seminal receptacle and the absence of an external seminal vesicle. The taxonomic value of morphological features are discussed and a key to the north Atlantic species given. The following species are described: Neophasis oculatus (Levinsen) from Myoxocephalus scorpius off West Greenland (type-material), Norway and Denmark, Lycodes esmarkii off NW Scotland and the Faroes, and L. vahli off Newfoundland; N. burti n. sp. (distinguished from N. oculatus by sucker-ratio and testicular configuration) from Myoxocephalus octodecemspinosus off Nova Scotia (type-locality) and New Brunswick, also? immature in Gadus morhua from the Gulf of St. Lawrence; N. anarrhichae (Nicoll) from Anarhichas lupus in the North Sea and off the Faroes; and N. pusilla Stafford from A. lupus off ‘eastern Canada’ (type-material) and Nova Scotia. The only other species in the genus is N. symmetrorchis Machida from the NW Pacific Ocean.

International audience; 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 degrees 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.

The genetic population structure of spotted wolffish Anarhichas minor (Olafsen) in the North Atlantic was in- vestigated by allozyme electrophoresis and by PCR based RFLP variation in mtDNA. Samples were collected from five sites distributed across the North Atlantic and from second generation Norwegian broodstock. The present data demon- strates that significant differences exist between almost all sampling sites, indicating biologically different groups of indi- viduals, and thus the existence of different management populations of spotted wolffish in the North Atlantic. Overall, the data indicated that isolation by distance is weak among spotted wolffish at the geographic scale investigated in this study, suggesting that gene flow between neighbouring spotted wolffish populations is low. The present study demonstrates a high level of geographic population structure between the western Atlantic, middle and eastern Atlantic and Baltic Sea, and thus, the findings should be useful in devising overall management and conservation strategies for the species.

Common wolffish larvae (25–35 mm) were caught at sea, transferred to the laboratory and fed both moist and dry pellets. A total mortality between 49.6 and 69.3% was observed in the different groups during an experimental period of 100 days. The causes of the mortalities included parasitism by Trichodina sp., infection by Vibro pelagius, cannibalism and starvation. Cannibalism amounted to 18.7–43.7% in the different groups but was negligible in groups above 8 g average wet weight. Mortality caused by starvation was significantly lower in the groups fed moist pellets (2.2-2.3%) than in groups fed dry pellets (11.0–28.4%). In all groups an increased hepato-somatic index of the dead fish was observed as the experiment proceeded.

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.

An understanding of how extinct animals functioned underpins our understanding of past evolutionary events, including adaptive radiations, and the role of functional innovation and adaptation as drivers of both micro- and macroevolution. Yet analysis of function in extinct animals is fraught with difficulty. Hypotheses that interpret molariform teeth in fishes as evidence of durophagous (shell-crushing) diets provide a good example of the particular problems inherent in the methods of functional morphology. This is because the assumed close coupling of form and function upon which the approach is based is weakened by, among other things, behavioural flexibility and the absence of a clear one to one relationship between structures and functions. Here we show that ISO 25178-2 standard parameters for surface texture, derived from analysis of worn surfaces of molariform teeth of fishes, vary significantly between species that differ in the amount of hard-shelled prey they consume. Two populations of the Sheepshead Seabream (Archosargus probatocephalus) were studied. This fish is not a dietary specialist, and one of the populations is known to consume more vegetation and less hard-shelled prey than the other; this is reflected in significant differences in their microwear textures. The Archosargus populations differ significantly in their microwear from the specialist shell-crusher Anarhichas lupus (the Atlantic Wolffish). Multivariate analysis of these three groups of fishes lends further support to the relationship between diet and tooth microwear, and provides robust validation of the approach. Application of the multivariate models derived from microwear texture in Archosargus and Anarhichas to a third fish species—the cichlid Astatoreochromis alluaudi—successfully separates wild caught fish that ate hard-shelled prey from lab-raised fish that did not. This cross-taxon validation demonstrates that quantitative analysis of tooth microwear texture can differentiate between fishes with different diets even when they range widely in size, habitat, and in the structure of their trophic apparatus. The approach thus has great potential as an additional tool for dietary analysis in extant fishes, and for testing dietary hypotheses in ancient and extinct species.

Atlantic cod and spotted wolffish fry were fed high-M alginate containing feed for 59 and 55 days, respectively. During this period the fry showed a higher specific growth rate compared to controls. Uptake and distribution of alginate was studied by inclusion of the 125 I-labelled molecule in the feed. The stomach and intestine contained the highest amount while the kidney, liver and spleen contained some, indicating that the alginate was taken up by the gut and transported to internal organs. Cod fry fed 0.06% and 0.1% high-M alginate showed a death rate of 51.4% and 53.3%, respectively. The lowest mortality, 48.1%, was found in fry fed 0.01% high-M alginate. Controls showed a mortality rate of 49.0%. Differences were, however, not statistically significant. Challenge of the immunostimulated fry (fed 0.02% and 0.06% alginate for 62 days) with atypical Aeromonas salmonicida bacteria resulted in accumulated mortalities of 56% and 49%, respectively, 47 days after infection. The group that received 0.06% alginate for a shorter period (47 days) and then control feed until challenged, and the group that received alginate by bath reached a cumulative mortality of 59% and 60%, respectively. Lowest mortality (44%) was seen in the control group. Numerous microabscesses were found in both immunostimulated and control fish in secondary lamellae of the gills, haematopoietic tissues of the kidneys, the submucosa and mucosa of the intestine, the spleen, the liver and the myocardium of the heart.

Two species of commercially important cold water fish were investigated for content of sulfated glycosaminoglycans (GAGs) in muscle tissue by use of in vivo 35S-sulfate labeling combined with different digestions (papain, chondroitinase ABC, keratanase and nitrous acid treatment), DEAE chromatography, SDS-PAGE and histology techniques. The species investigated in this study have different gaping properties. The non-gaping species, spotted wolffish (Anarhichas minor), contained 3-4 times more 35S-sulfated anionic components than the gaping species, Atlantic cod (Gadus morhua). The higher level of sulfation in wolffish was supported by light microscopy studies using Alcian blue staining with different concentrations of MgCl2 as critical electrolyte. Furthermore, the muscular connective tissue in the non-gaping species was dominated by chondroitin sulfate (CS)/dermatan sulfate (DS), whereas the gaping species was more dominated by heparan sulfate (HS). Moreover, structural differences were observed in the junctions between the myofibers, which were more pronounced in the wolffish. The histological studies revealed that the basement membrane area was rich in acidic mucopolysaccharides in both species.

Spotted wolffish Anarhichas minor (approx. 0.7 g) were found to be susceptible to infection with a nodavirus isolated from Atlantic halibut (AHNV) by bath-challenge. During the acute stage of infection, 4 to 8 wk post-challenge, viral encephalopathy and retinopathy (VER) were diagnosed by histopathology, immunohistochemistry (IHC) and reverse transcriptase-polymerase chain reaction (RT-PCR). Accumulated mortality was 52% in the challenged group. The surviving fish were sampled 16 wk post-challenge, by which time they had grown to approximately 17 g. No clinical signs of VER were observed in these fish. RT-PCR examination revealed the presence of nodavirus in several organs of the survivors, but no immunopositive cells were detected by IHC. Nodavirus was reisolated from fish at the last sampling in SSN-1 cells, showing that nodavirus retains virulence in persistently infected wolffish for at least 16 wk post-bath-challenge.

Atypical Aeromonas salmonicida strains comprise a heterogeneous group in terms of molecular and phenotypic characteristics. They cause various conditions of ulcer diseases or atypical furunculosis and are being isolated in increasing number from various fish species and geographical areas. Several marine fish species susceptible to atypical A. salmonicida, including spotted wolffish Anarhichas minor O., are now being farmed and new vaccines may be needed. A commercial furun- culosis vaccine for salmon is reported to protect wolffish poorly against experimental challenge with atypical A. salmonicida. The protective antigen(s) in furunculosis vaccines is still unclear, but in oil- adjuvanted vaccine for Atlantic salmon Salmo salar L., the surface A-layer was shown to be important for protection. In spotted wolffish, the efficacy of atypical furunculosis vaccines seems to vary with the atypical A. salmonicida strains used as bacterin in the vaccine. In the present study we investi- gated whether differences in the A-layer protein among atypical strains might be responsible for the observed variation in vaccine efficacy. Atypical A. salmonicida strains from 16 fish species in 11 coun- tries were compared by genome polymorphism analysis using amplified fragment length polymor- phism (AFLP) fingerprinting and by comparative sequencing of the vapA genes encoding the A-pro- tein. The A-protein sequences appeared to be highly conserved except for a variable region between Residues 90 to 170. Surprisingly, the grouping of strains based on AFLP- or A-protein sequence sim- ilarities was consistent. In addition, serological differences in the A-protein among the strains were demonstrated by an A-protein-specific monoclonal antibody. Vaccines based on atypical A. salmoni- cida strains possessing genetically and serologically different A-layer proteins were shown to result in significantly different protection in spotted wolffish.