The spotted wolf®sh Anarhichas minor (Olafsen), with its rich and tasty ®llets, popular skin and high growth rates in captivity, is a promising candidate for cold-water aquaculture. We have established a production line for the wolf®sh 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 wolf®sh juveniles fed formulated dry¯oating feed at low temperatures in shallow raceways has been promising. After 2, 3 and 4 years, the mean weights of the ®rst 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.

Temperature influenced the developmental rate, survival and early growth of eggs and embryos of spotted wolffish, Anarhichas minor (Olafsen), an interesting candidate for cold water cultivation. The total incubation period decreased from 220 days at 4 °C (880 daydegrees), to 177 days at 6 °C (1062 daydegrees) and 150 days at 8 °C (1200 daydegrees) in these experiments. The proportion of normal embryos and survival of eggs until hatching were highest when the eggs were incubated at 6 °C. During the incubation period, the embryo and yolk sac size at 280 daydegrees was not significantly different but at 850 daydegrees the embryo size was inversely related to temperature and the remaining yolk sac size positively correlated with the incubation temperature. The transformation of yolk to body mass during incubation appeared to be most efficient at 4 °C, and the embryos hatched with a larger visible yolk sac at 6 and 8 °C. The largest larvae (wet‐weight) hatched from the largest eggs and the egg groups incubated at the lowest temperature (4 °C). There was no effect of temperature on meristic characters. During 6 weeks post‐hatching, all larvae from the three temperature groups were fed formulated dry feed in excess at 8 °C in low water‐level raceway systems. During startfeeding, the larvae from eggs incubated at the lowest temperature (4 °C) showed the highest growth rates (SGR). Best survival of larvae was noted among batches incubated at 6 °C.

In order to define temperature regimes that could benefit successful production of spotted wolffish (Anarhichas minor) juveniles, experiments with offspring from two different females were carried out. The larvae were fed a new formulated feed or a commercial start-feed for marine fish, both of which have given high survival rates. In the first experiment newly hatched larvae were fed at constant 6 8C, 8 8C, 10 8C and 12 8C as well as at ambient seawater temperature (2.9±4.5 8C) during 63 days. High survival, 90% to 96%, was registered at ambient and most constant temperature regimes, whereas in the 12 8C groups survival was reduced to 80%. Growth rate (SGR) was very low, 1.8% day À1 , at the low ambient temperatures. Growth rate was positively correlated with temperature and varied between 3.1% day À1 to 4.7% day À1 , from 6 8C to 12 8C. In the second experiment, set up to include potential detrimental temperatures and study beneficial effects of a more restricted, elevated firstfeeding temperature regime, the larvae were fed at constant 8 8C, 10 8C, 12 8C, 14 8C and 16 8C until 30 days post hatch, followed by constant 8 8C for the next 33 days. In this experiment, low survival, 25% and 2.0%, was registered at 63 days post hatch when larvae were reared initially at 14 8C and 16 8C respectively. The survival of the larvae at the other temperature regimes varied from 47% to 64%, highest survival rate (64%) was found at 8 8C. The lowest specific growth rate, 2.6% day À1 , was noted in the 16 8C group. At constant 8 8C to 14 8C (regulated to 8 8C), the SGR varied from 4.45% day À1 to 5.13% day À1 . The larvae grew faster in the experiment when initially comparable temperatures (8 8C, 10 8C and 12 8C) were regulated to constant 8 8C after 30 days compared with the first experiment where feeding was carried out at the same constant temperatures (8 8C, 10 8C and 12 8C) during the whole experimental period.

The myth of fibroid degeneration in the canine intervertebral disc -A histopathological comparison of disc degeneration in chondrodystrophic and nonchondrodystrophic dogs Myten om fibroid degeneration i hundens intervertebraldiskerEn histopatologisk jämförelse av diskdegeneration mellan chondrodystrofa och icke chondrodystrofa hundar Tove Hansen Supervisor: Niklas Bergknut, Department of Clinical Sciences Examiner: Ragnvi Hagman, Department of Clinical Sciences Degree Project in Veterinary Medicine SUMMARYIn the 1950's, the veterinary pathologist, Hans-Jörgen Hansen noticed several dissimilarities between so called chondrodystrophic and non-chondrodystrophic dog breeds regarding intervertebral disc degeneration and related diseases. Chondrodystrophic breeds are characterized by disproportionally short extremities due to disturbances in the endochondral ossification whereas non-chondrodystrophic breeds have normal bodily constitutions. The two breed types often differ regarding age of onset of disease, spinal location and severity of clinical signs. He also noted different histopathological patterns during the course of degeneration, foremost in the centre of the intervertebral disc, the nucleus pulposus. Due to this, he named the degenerative processes chondroid metamorphosis and fibroid metamorphosis in chondrodystrophic and non-chondrodystrophic breeds respectively. In general, chondroid metamorphosis refers to the replacement of the original cell type (the notochordal cell) with chondrocyte-like cells, whereas the fibroid metamorphosis refers to replacement of these cells with fibrocyte-like cells. This distinction has since then been an accepted distinction between the two breed types. However, more recent studies indicate that the histopathological patterns are more similar in the two breed types than previously described, and that the chondroid metamorphosis might be the degenerative process taking place in both breed types.In this study the histopathological appearances of 42 intervertebral discs from 16 chondrodystrophic and 17 non-chondrodystrophic dogs in early stage intervertebral disc degeneration were examined. After midsagittal transection of the spines, the intervertebral discs were graded macroscopically between one and three on a five-grade scale (the Thompson grading scheme). Subsequently, each intervertebral disc was individually fixated in formalin and decalcified in EDTA. After decalcification, the intervertebral discs were embedded in paraffin, sliced with a microtome and stained with Hematoxilin and Eosin and Alcian Blue/Picrosirius Red. The histological samples were thereafter graded according to a histological grading scheme (the Boos grading scheme) after which the histological scores were compared between chondrodystrophic and non-chondrodystrophic dogs.The results showed that there was a significant difference in total histological scores between chondrodystrophic and non-chondrodystrophic dogs in the two lowest macroscopical grades of degeneration. Chondrodystrophic dogs had a highe...

This study illustrates the embryo development of the spotted wol⁄sh (Anarhichas minor Olafsen), an interesting candidate for cold-water aquaculture. The egg morphology (semitransparent, yellow-white with numerous oil droplets in the yolk), size (5.4^6.5 mm) and long embryogenesis (c. 800^1000 d1, depending on temperature) of A. minor are very similar to Anarhichas lupus. Cleavage is slow, and the ¢rst cell divisions take place at 12 h at 8 1C. After 12 days the 2mm embryo with the ¢rst somites is laid down and the blastopore starts closing. The fat globules in the yolk fuse into one after 22 days, and after 30 days eye pigmentation is noticeable. After 44 days, eye pigmentation is strong, the digestive tract folded and a green gall bladder can be noted in the now 11-mmlong embryo. One week later the blood is brightly red, the intestine is pigmented and the lower jaw is well developed. Premature hatching may occur from this stage. After 58 days vascularization of the yolk is complete, capillaries are noted in the ¢n fold, the ¢rst ray rudiments are established in the tail and pectoral ¢ns, and the four gill arches are covered by the operculum. The preanal ¢nfold is reduced after 72 days, stomach and gill ¢laments are formed, and six pigmented rows are noted on the 17-mm-long embryo body. After 86 days all ¢n rays are seen and the digestive tract is intensely pigmented and folded. Hatching (normal) starts after 110 days and may last for 2^3 weeks. Late embryos and early larvae of A. minor have more distinct bands of pigment along the body compared with the closely related A. lupus. An increase in both length and weight of the embryos in individual batches occurs during the hatching period.