AquaBreeding Project title: “Towards enhanced and sustainable use of genetics and breeding in the European aquaculture industry”

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Review on Breeding and Reproduction of European aquaculture species

Atlantic Cod (Gadus morhua)

Anna K. Sonesson, Bendik Fyhn Terjesen, Barbara Grisdale-Helland, Turid Mørkøre (AKVAFORSK, Norway), Morten Rye, Terje Refstie (Akvaforsk Genetics Center, Norway), Igor Babiak (University Bodø, Norway), Kjersti Fjalestad, Anne Kettunen (Norwegian Institute of Fisheries and Aquaculture Research, Norway), Brendan McAndrew (Sterling University, UK)
January 2008

1. General information on production and breeding

History of the domestication

The first hatchery for Atlantic cod had already been built by 1882-1884 at Flødevigen, Arendal, Norway. Larvae were released into the sea in order to increase wild stock, which was declining even in those times [1]. In 1976, 4000 Atlantic cod fry were produced for aquacultural purposes at the Institute of Marine Research, Norway. At the end of 1990s, interest in Atlantic cod aquaculture grew as the wild catch decreased and prices went up. The first commercial breeding program started in Norway 2002. Today there are four (semi)commercial breeding programs for Atlantic cod in Europe: two in Norway, one in Scotland and one in Iceland.

Production (Figure 1)

European production of farmed Atlantic cod in 2006 was 12,600 tonnes, of which some originated from wild caught fish. Out of this total, about 10,000 tonnes came from Norway. The other countries that produce cod are Iceland, Faroe Islands, UK, Ireland and Canada; Figure 1. Farmed cod has been well received by consumers in countries where it has been introduced, e.g. France, the Netherlands, U.K., Denmark and Spain.

Figure 1. Distribution area of Gadus morhua wild populations (red) and countries with aquacultural production (green). According to Marteinsdottir 2005 [2].

  • Consumption

The worldwide catch of Atlantic cod was 842 951 tonnes in 2005 [3]. Hence, farmed Atlantic cod production is marginal compared with the quantity caught in the wild.
Biological features of interest for breeding practices

  • Main commercial data on weight and age at harvest and slaughtering performances.

The market size of 2-5 kg is reached after ~18 months in net pens (~27 months after hatching).

  • Feeding practices during the lifecycle

At about 4-5 days after hatching, larvae start consuming live prey, e.g. rotifers and Artemia [4]. Feed for adult fish contains 50 – 60% protein and 13 – 27% lipid [5-7, Grisdale-Helland et al., unpublished]. The replacement of marine raw materials with vegetable raw materials is currently low, but is the subject of ongoing research [8, 9].

The generation interval is 3 years for both males and females.
Main diseases

The main potential disease problems are caused by both bacterial and viral diseases.

The main bacterial diseases are: francisella (Francisella philomiragia), vibriosis (Listonella angullarium) and furunculosis (Aeromonas Salmonicida).

Francisella has a long survival time outside the host, and only a few bacteria are needed for infection [10]. This makes it a serious problem for cod farms. In Norway, auto-vaccines are under test [11].

Vibriosis is a problem over the whole life cycle and is a chronic disease. Vaccines exist for vibriosis, which are given to the fish when they weigh 1 and 5 g [12].

Furunculosis is often seen together with other diseases [11] and is stress-induced [13].
The main viral diseases are: infectious pancreatic disease (IPN) and viral nervous necrosis (VNN).

IPN is especially lethal in larval and juvenile stages.

VNN causes a prolonged disease status in Atlantic cod [11], and no vaccine yet exists. VNN is thought to be induced by high water temperature and risks to decrease with age [11].
Neck and spinal deformities also exist in Atlantic cod. These are partly induced by high water temperature [11].

2. Genetic variability of the species

Wild genetic resources available

Atlantic cod live on the continental shelves of the North Atlantic [14]; Figure 1. A report from the International Council of Exploration of Sea should be consulted for a comprehensive review of the different wild stocks [15].

Differences between wild and/or domesticated populations

Different DNA marker studies have shown different degrees of structuring in populations of Atlantic cod. These include reports of different degrees of population structuring in the eastern [16-18] and western [19] Atlantic. For one genetic marker, PanI, coastal cod is almost fixed for allele A, whereas cod from the Barents Sea is almost fixed for allele B [17, 18]. Other studies report panmixia [20, 21].

Interaction between wild and domesticated stocks

Atlantic cod spawn easily in net cages. Domestic strains therefore have a large potential for genetic impact. Cultured cod mature earlier than their wild ancestors [4]. This early maturation means that a longer production time (~6 months) is needed, because growth is stunted and fish lose weight during mature periods. One aim for Atlantic cod farming is therefore to reach slaughter size before the fish become mature, or else to slaughter at a smaller size.

In addition, escapes of farmed Atlantic cod may become an increasing problem. These fish can escape because they are kept in net pens in the sea, which they can bite their way out of. The number of escaped marine fish in Norway was 288,000 in 2006 and about 70,000 in 2007. Much research is being done in Norway to reduce escapes of Atlantic cod, including the development of stronger pens.
Inbreeding effects

Not documented.

3. Reproduction

Fecundity and main reproductive features

Atlantic cod are batch spawners and females in culture can shed up to 15 batches of eggs during the spawning period. A female with a good nutritional status can spawn up to about 1.5 L eggs per kg bodyweight during the spawning season. The eggs are small (1.1-1.5 mm), spherical and transparent; high quality eggs are also buoyant in sea water. They are usually incubated at 5-7˚C and hatch after about 15 days. Larval length at hatching is around 4 mm. Both natural mating and stripping are performed by breeding companies. Photoperiod treatment is routinely used on broodstock held in tanks, to induce maturity and assure year-round production [22-24].

Atlantic cod are batch spawners and females in culture can shed up to 15 batches during the spawning period. A female in good nutritional status can spawn up to about 1.5 liter eggs per kg bodyweight during the spawning season. The eggs are small (1.1-1.5 mm), spherical, transparent, and high quality eggs are buoyant in sea water. They are usually incubated at 5-7˚C and hatch after about 15 days. Larval length at hatching is around 4 mm. Both natural mating and stripping is performed by the breeding companies. Photoperiod treatment of broodstock in tanks is used routinely to induce maturity and assure production all year around [22-24].


Cryopreservation protocols have been developed [25, 26, Marschhäuser, in prep.], but no commercial products are yet available.


No cryobank has been reported.

4. Selection

Genetic variability per trait

In joint estimates on coastal cod and cod from Barents Sea, heritability was 0.52 [27] and 0.64 [28] for body weight, 0.0 for general survival [27] and 0.21 for sexual maturity [28]. In another Norwegian study, heritability for body weight was 0.41, 0.45 and 0.42 at tagging, 1+ and 2+ years, respectively, and a high genetic correlation of 0.81 between body weight at 1+ and 2+ years was reported [29]. Estimates of heritability for resistance to vibriosis (Vibrio anguillarum) varied from 0.08 to 0.17 [30] and 0.24 [31]. Liver index (% liver weight/total weight) had a heritability of 0.55, and head index (% head weight/total weight) 0.51 [31]. Heritability estimates for fillet and loin yields were 0.16 and 0.06, respectively [31].

Genetic correlations and undesirable side effects

Sexual maturity is a trait influenced by water temperature and photoperiod [22, 32, 33]. A genetic correlation of 0.24 was found between body weight and sexual maturity [28], and a genetic correlation of 0.50 was found between body weight and spinal deformity [32, 34]. Hence, selection for increased body weight will result in increased incidence of spinal deformities.

G*E interactions

In a Norwegian study, no significant interaction was found between strain (coastal cod and cod from the Barents Sea) and growing site in different counties (Møre and Romsdal (63˚) and Troms (71˚)) [28]. The ranking of strains was equal in both environments, meaning that both strains are equally suitable for use in breeding. However, a significant interaction between full-sib group and county was found for body weight (P<0.001), spinal deformity (P<0.01) and sexual maturity (P<0.001) at two years of age. In particular, spinal deformity was lower in the cooler water of Troms county, which is to be expected as spinal deformity is thought to be influenced by water temperature.

Genetic responses, progresses and control lines

Not documented.

Dominance and intraspecific crossing

Not documented.

5. Polyploidisation and monosexing and hybrids

Triploid induction and performances

Triploidisation has not been performed at the commercial level. However, triploid cod has been produced at experimental level using thermal shock [35]. Use of heat shock resulted in 66-100% success of triploidy, but a rather low survival rate (10-20%). Triploidy is also being considered in the project NorthCod, as a way to produce sterile fish [36].

Tetraploid induction and performances

Not documented.

Gynogenesis, androgenesis and mitotic clone performances

Gynogenetic cod has been produced at experimental level using pressure shock (Ghigliotti et al., in preparation).

Interspecific hybridisation

Not documented.

6. Genomics

Genetic markers for genealogical traceability

Microsatellites for parentage testing have been developed and used at the experimental level [37]. Assignment rate to a single parental pair was 91.2%, when 523 mating were considered. Herlin et al. [39] showed, using a mass spawning of Atlantic cod, that there were inconsistencies between different software packages for parentage assignment.

QTL and Marker Assisted Selection

No QTL detection studies have been published. Marker-assisted selection is not presently used in any breeding program.

Other genomic tools

The main institutes that have worked on the development of genomic tools for Atlantic cod are:

Norway: Institute of Marine Research (IMR), Norwegian Institute of Fisheries and Aquaculture Research, AKVAFORSK.

Canada: Huntsman Marine Centre and The Atlantic Genome Centre, Genome Atlantic.

Today, the following resources are available (pers comm. Frank Nilsen, IMR, Norway):

  • Microsatellite markers: ~100

  • Single nucleotide polymorphisms (SNP): ~350 validated

  • Bacterial Artificial Chromosomes (BAC): 92,000

  • Expressed sequence tags (EST): 60,000 in Canada, 50,000 in Norway

  • Microarray probes: 16,000

  • Linkage map: 250 SNP and 60 microsatellites

In addition, an initiative has been taken to sequence the genome of Atlantic cod using Sanger, Solexa and Roche 454 technologies [contact: Dr. K. Jacobsen, Uio, Norway].

Not documented.


  1. P. Solemdal, E. Dahl, D. S. Danielssen, and E. Moksness, “The cod hatchery in Flødevigen- background and realities,” In. Flødevigen rapportser. 1. The propagation of cod Gadus morhua L. Part 1. Edited by: Dahl, E., Danielssen, D.S., Moksness, E., Solemdal, P., 1984, pp. 17-45. IBSN 0333-2594.

  2. G. Marteinsdottir, D. Ruzzante, and E. E. Nielsen, “History of the North Atlantic cod stocks, ICES CM2005/AA:19, 2005, pp17.

  3. FAO,

  4. E. Moksness, E. Kjørsvik, and Y. Olsen, “Culture of Coldwater Marine Fish”. Blackwell Scientific Publications Ltd, UK, 2004, ISBN: 9780852382769

  5. G. M. Berge, J. Ø. Hansen, B. Ruyter, Å. Krogdahl, H. Holm, T. F. Galloway, J. Holm, and M. Hillestad, Utilisation of fat and fatty acids in Atlantic cod (Gadus morhua) fed diets with differing protein: energy ratio. Aquaculture Europe 2005, Trondheim, August 5-9, 2005.

  6. S. Morais, J. G. Bell, D. A. Robertson, W. J. Roy, and P. D. Morris, “Protein/lipid ratios in extruded diets for Atlantic cod (Gadus morhua L.): effects of growth, feed utilisation, muscle composition and liver histology,” Aquaculture, vol. 203, pp. 101-119, 2001.

  7. G. Rosenlund, Ø. Karlsen, K. Tveit, A. Mangor-Jensen, and G. I. Hemre, “Effect of feed composition and feeding frequency on growth, feed utilization and nutrient retention in juvenile Atlantic cod, Gadus morhua L.,” Aquacult. Nutr., vol. 10, pp. 371-378, 2004.

  8. S. Refstie, T. Landsverk, A. M. Bakke-McKellep, E. Ringo, A. Sundby, K. D. Shearer, and A. Krogdahl, “Digestive capacity, intestinal morphology, and microflora of 1-year and 2-year old Atlantic cod (Gadus morhua) fed standard or bioprocessed soybean meal,” Aquaculture, vol. 261, pp. 269-284, 2006.

  9. G. Rosenlund, and M. Skretting, “Worldwide status and perspective on gadoid culture”. ICES Journal of Marine Science, vol. 63, pp. 194-197, 2006.

  10. A. Nylund, K. F. Ottem, K. Watanabe, E. Karlsbakk, and B. Krossoy, “Francisella sp (Family Francisellaceae) causing mortality in Norwegian cod (Gadus morhua) farming,” Archives of microbiology, vol. 185, pp. 383-392, 2006.

  11. A. B. Olsen, G. Bornø, D. J. Colquhoun, K. Flesjå, R. Haldorsen, T. A. Mo, H. Nilsen, H. R. Skjelstad, and B. Hjeltnes, “The health situation in farmed fish in Norway, 2006”. Report by National Veterinary Institute, Norway, 2006.

  12. Ø. Evensen, O. Breck, B. Hjeltnes, F. Nilsen, M. Bjørgan Schrøder, and T. Håstein, “Report Research Council Norway. Helse/sykdomsproblemer hos norske oppdrettsarter,” 2004. ISBN: 82-12-01941-1.

  13. Á. Kristmundsson, S. Helgason, S. H. Bambir, and M. Eydal, “Natural outbreaks of Aeromonas salmonicida ssp. achromogenes among farmed Atlantic cod, Gadus morhua, in Iceland,” Abstract symposium ‘Cod Farming in Nordic Countries’, Reykjavík, 6 - 8 September 2005.

  14. G. R. Lilly, and J. E. Carscadden, “Predicting the future of marine fish and fisheries off eastern Labrador and Newfoundland under scenarios of climate change; information and thoughts for the Arctic Climate Impact Assessment (ACIA),” CSAS Research Document, 2002/111.

  15. ICES, “Spawning and life history information for North Atlantic cod stocks. ICES Cooperative Research Report, No. 274, pp. 152, 2005.

  16. E. E. Nielsen, M. M. Hansen, D. E. Ruzzante, D. Meldrup, and P. Grønkjær, “Evidence of a hybrid-zone in Atlantic cod (Gadus morhua) in the Baltic and Danish Belt Sea, revealed by individual admixture analysis,” Mol. Ecol., vol. 12, pp. 1497-1508, 2003.

  17. S. E. Fevolden, and G. H. Pogson, “Genetic divergence at the synatophysin (syp-1) locus among Norwegian coastal and north-east arctic populations of Atlantic cod, Gadus morhua,” J. Fich Biol., vol. 51, pp. 895-908, 1997.

  18. T. H. Sarvas, and S. E. Fevolden, “The scnDNA locus Pan I reveals concurrent presence of different populations of Atlantic cod (Gadus morhua L.) within a single fjord,” Fisheries Research, vol. 76, 307-316, 2005.

  19. D. E. Ruzzante, C. T. Taggart, and D. Cook, “A review of evidence for genetic structure of cod (Gadus morhua) populations in the NW Atlantic and population affinities of larval cod off Newfoundland and the gulf of St. Lawrence,” Fisheries Research, vol. 43, pp. 79-97, 1999.

  20. P. J. Smith, A. J. Birley, A. Jamieson, and B. A. Bishop, “Mitochondrial DNA in the Atlantic cod, Gadus morhua: lack of genetic divergence between eastern and western populations,” J. Fish Biol., vol. 34, pp. 369-373, 1989.

  21. E. Arnason, “Mitochondrial cytochrome b DNA variation in the high-fecundity Atlantic cod Trans-Atlantic clines and shallow gene genealogy,” Genetics, vol. 166, pp. 1871-1885, 2004.

  22. T. Hansen, Ø. Karlsen, G. L. Taranger, G. I. Hemre, J. C. Holm and O. S. Kjesbu, “Growth, gonadal development and spawning time of Atlantic cod (Gadus morhua) reared under different photoperiods,” Aquaculture, vol. 203, pp. 51-67, 2001.

  23. A. Davie, M. Porter, N. Bromage, and H. Migaud, “The role of seasonally altering photoperiod in regulating physiology in Atlantic cod (Gadus morhua). Part I. Sexual maturation,” Canadian Journal of Fisheries and Aquatic Sciences, vol. 64, pp. 84-97, 2007a.

  24. A. Davie, M. Porter, N. Bromage, and H. Migaud, “The role of seasonally altering photoperiod in regulating physiology in Atlantic cod (Gadus morhua). Part II. Somatic growth,” Canadian Journal of Fisheries and Aquatic Sciences, vol. 64, pp. 98-112, 2007b.

  25. J. D. De Graaf, and D. L. Berlinsky, “Cryogenic and refrigerated storage of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) spermatozoa,” Aquaculture, vol. 234, pp. 527-540, 2004.

  26. R. M. Rideout, E. A. Trippel, and M. K. Litvak, “The development of haddock and Atlantic cod sperm cryopreservation techniques and the effect of sperm age on cryopreservation success,” Journal of Fish Biology, vol. 65, pp. 299-311, 2004.

  27. B. Gjerde, B. F. Terjesen, Y. Barr, I. Lein, and I. Thorland, “Genetic variation for juvenile growth and survival in Atlantic cod (Gadus morhua),” Aquaculture, vol. 236, pp. 167-177, 2004.

  28. K. Kolstad, I. Thorland, T. Refstie, B. Gjerde, “Genetic variation and genotype by location interaction in body weight, spinal deformity and sexual maturity in Atlantic cod (Gadus morhua) reared at different locations off Norway,” Aquaculture, vol. 259, pp. 66-73, 2006a.

  29. A. Kettunen, Genetic parameters for important traits in the breeding program for Atlantic cod (Gadus morhua l.), [Abstract]. International Symposium on Genetics in Aquaculture, IAGA IX, Montpellier, France, June 26-30, 2006.

  30. A. Kettunen, T. Serenius, and K. T. Fjalestad, “Three statistical approaches for genetic analysis of disease resistance to vibriosis in Atlantic cod (Gadus morhua L.),” J. Anim. Sci., vol. 85, pp. 305-313, 2007.

  31. T. Refstie, and I. Thorland, ”Presnetation Status/informasjon om avlsarbeidet i torskeoppdrett at symposium ‘Sats på torsk’,” Bergen, 2007.

  32. B. Norberg, C. L. Brown, A. Halldorsson, K. Stensland, and B. T. Bjornsson, “Photoperiod regulates the timing of sexual maturation, spawning, sex steroid and thyroid hormone profiles in the Atlantic cod (Gadus morhua),” Aquaculture, vol. 229, pp. 451–467, 2004.

  33. L. O’Brien, “Factors influencing the rate of sexual maturity and the effect on spawning stock for Georges Bank and Gulf of Maine Atlantic Cod Gadus morhua stocks,” Journal of Northwest Atlantic Fishery Science, vol. 25, pp. 179-203, 1999.

  34. K. Kolstad, I. Thorland, T. Refstie, and B. Gjerde, “Body weight, sexual maturity and spinal deformity in strains and families of Atlantic cod (Gadus morhua) at two years of age at different locations along the Norwegian coast,” ICES Journal of Marine Science, vol. 63, 246-252, 2006b.

  35. S. Peruzzi, A. Kettunen, R. Primicerio, and G. Kauric, “Thermal shock induction of triploidy in Atlantic cod (Gadus morhua L.),” Aquac. Res., vol. 38, pp. 926-932, 2007.

  36. O. H. Ottesen, I. Babiak, J. Treasurer, D. Penman, E. Hardardottir, O. Nicolaisen, A. Karlsen, and N. Zhuravleva, “NorthCod: sustainable cod production in northern Europe. Abstract symposium ‘Cod Farming in Nordic Countries’,” Reykjavík, 6 - 8 September 2005.

  37. M. S. Wesmajervi, J. I. Westgaard, and M. Delghandi, “Evaluation of a novel pentaplex microsatellite system for paternity studies in Atlantic cod (Gadus morhua L.),” Aquac. Res., vol. 37,pp. 1195-1201, 2006.

  38. M. Herlin, M. Delghandi, M. Wesmajervi, J. B. Taggart, B. J. McAndrew, and D. J. Penman, “Analysis of the parental contribution to a group of fry from a single day spawning from a commercial Atlantic cod (Gadus morhua) breeding tank,” Aquaculture (in press), 2007a.

  39. M. Herlin, J. B. Taggart, B. J. McAndrew, and D. J. Penman, “Parentage allocation in a complex situation: A large commercial Atlantic cod (Gadus morhua) mass spawning tank,” Aquaculture 272, S195-S203, 2007b.

Review on Breeding and Reproduction of European aquaculture species

Turbot (Scophthalmus maximus)


Pierrick Haffray (SYSAAF, France), Paulino Martinez (Lugo University, Spain)
January 2008

1. General information on production and breeding

History of the domestication

Turbot farming was first initiated in the UK at the beginning of the 1970s. An intense investment in research was made in the UK, France and Norway from then until the mid eighties. Advances in reproduction, larval rearing and growing led to the first private investments in production in Norway, the UK, Spain and France. Commercialisation of juveniles from Europe sold to Chile and China in 1992 initiated production in these countries. Turbot has now become the main aquaculture species in northern China, which is currently the leading world producer even if exact production figures are difficult to obtain (> 10,000 T in 2006).

Domestication was initiated simultaneously in Norway, France and Spain at the beginning of the 1990s. Most European juveniles (nearly 10 million) originate from France and Spain, but there is also some production from Denmark and in some cases from Chile. In Asia, China is the leader for juvenile production, which is estimated at more than 50 million fry per year.
Production (Figure 1)

Total European production of farmed turbot reached 7260 T in 2006 [1]. Any further increase in production will be limited as turbot are mainly reared in land based facilities and space to develop such farming is restricted within the EU. Spain is the leading European producer (5700 T), followed by France (800 T) and Portugal (540 T). Expectations about the development of water recirculation systems have not yet been fulfilled as they are not economically viable at present.

Figure 1. Distribution area

of wild populations (red) and

production countries (green).

Source: FAO Fishbase.

  • EU consumption

EU consumption should be more or less equal to the total European production from aquaculture and fisheries. Wild catch from fisheries is estimated at 7000 T per year, varying from 3000 to 9500 T between years, for which the leading country is the Netherlands.
Biological features of interest for breeding practices

  • Main commercial data on weight and age at harvest and slaughtering performances

Turbot is mainly slaughtered at 850-1000 g, as growth is slow and feed conversion ratio too high. Some farms produce bigger sizes (2-3 kg) but low feed efficiency and limited growth increase production costs.

  • Feeding practices during the lifecycle

The turbot is a predator and is initially fed with live food (rotifers and artemia). Weaning is practiced between 50 and 70 days. Fish are then fed with the same type of feed as salmonids. Feed for turbot should be rich in protein but must not contain a high proportion of lipids.

  • Generation interval for males and females

First sexual maturation of some males and females has been described at 2 years old [2]. However, a reasonable quantity of gametes can only be collected from most of broodstock at 3 years of age for males and at 4 years of age for females. Generation interval can theoretically be considered as 3 years of age, but in practice it is closer to 4 - 5 years in optimal farming conditions (temperature, growth).
Main diseases

Turbot is susceptible to several important bacterial diseases [3]: Vibrio anguillarum (vibriosis), Aeromonas salmonicida (furonculosis), Flexibacter maritimus (flexibacteriosis), Pseudomonas anguilliseptica (winter disease), Edwarsielle tarda and Mycobacterium marinum (mycobacteriosis). This species is also susceptible to IPN and VHS virus [4]. Several parasites can also cause serious losses, depending on the farm and the area of production. These include Enteromyxum scophthalmi (Myxosporean) and Uronema marinum that is one of the most important parasites in Spain, China and Korea.

Multiple vaccines are available for Furonculosis, Flexibacter and Vibrio depending upon the country (Spain, France), but the small production level and the absence of officially registered European vaccines are important factors limiting the improvement of broodstock sanitary status.

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