The Status and Perspectives for the Species

Svåsand, Terje; Otterå, Håkon; Taranger, Geir Lasse; Litvak, Matthew K.; Skiftesvik, Anne Berit; Bjelland, Reidun M.; Павлов, Д. А.; Holm, Jens Chr.; Harboe, Torstein; Mangor‐Jensen, Anders; Norberg, B; Howell, B. R.

doi:10.1002/9780470995617.ch10

Cited by 22 publications

(17 citation statements)

References 67 publications

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“…Cannibalism in cod may be severe in cohorts exhibiting large size variation, especially in inadequately fed groups (Folkvord, 1991). Ensuring adequate food distribution within a sea cage environment of ''nursery phase'' cod may be difficult, and cannibalism resulting from sub-optimal feeding strategies may ensue (Svåsand et al, 2004). There is an evident lack of research pertaining to optimal feeding strategies in post-transfer cod and, for the on-grower, this is of great concern.…”

Section: Discussionmentioning

confidence: 98%

“…However, changes in the economic climate, brought about by low salmon prices and the decline in wild cod (Gadus morhua L.) stocks, have caused farmers to begin to diversify into cod culture. Despite promising results from preliminary trials (Svåsand et al, 2004) and considerable interest being expressed by investors (Adoff et al, 2002), there remains a need to optimize certain protocols, especially at a regional level , both in larviculture and early on-growing.…”

Section: Introductionmentioning

confidence: 97%

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Comparison of performance of two size groups of farmed cod (Gadus morhua L.) juveniles following transfer to sea cages

Watson¹,

Sales²,

Cumming³

et al. 2006

ICES Journal of Marine Science

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In order to investigate the biologically and economically optimum size for sea transfer of cultured cod, replicated trials were undertaken using experimental cages (1.5 m × 1 m × 1 m) stocked with two size grades of cod juveniles previously “untested” for on-growing at sea in Shetland: “small grade” (SG), 9.3-g mean weight (±2.08 s.d.) and “large grade” (LG), 19.4-g mean weight (±4.48 s.d.). Survival was high in both grades tested, with no significant difference in overall mortality (7.3% (SG) and 8.4% (LG)). A significant difference was observed in the overall percentage growth per day (%SGR) (p = 0.02), with SG and LG exhibiting values of 1.3 and 1.08, respectively. Regression analysis of body weight gain over time between the two grades revealed a significantly higher proportional weight gain in SG (p = 0.01). Cost analysis revealed an initial saving of 8.5% by selecting SG juveniles. This saving was reduced to 2.9% when the cost of feeding these fish was taken into account. However, food wastage was higher in this study than would be expected in a commercial operation, suggesting that the actual saving for the on-grower could be greater than 2.9%. Selecting smaller sized juveniles for transfer will increase the growout period. However, this may be offset by the fact they may be transferred earlier, at a significantly lower price.

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Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

Comparison of performance of two size groups of farmed cod (Gadus morhua L.) juveniles following transfer to sea cages

Watson¹,

Sales²,

Cumming³

et al. 2006

ICES Journal of Marine Science

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“…Population studies of algal cultures used as feed for scallop larvae have identified a variety of bacterial strains associated with the algal cultures (Sandaa et al 2003, Nicolas et al 2004, probably including opportunistic pathogens as well as commensal or mutualistic bacteria. In intensive aquaculture, cod larvae are offered rotifers, usually Brachionus plicatilis, and brine shrimp, mostly Artemia franciscana, as live feed (Svåsand et al 2004, Reitan 2005. Recently, Korsnes et al (2006) demonstrated the presence of bacteria with high sequence similarity to Vibrio anguillarum in rotifer cultures and the gut of cod larvae fed rotifers.…”

Section: Discussionmentioning

confidence: 99%

“…Atlantic cod Gadhus morhua L. aquaculture has been expanding rapidly in Norway since 2000 (Svåsand et al 2004). In 2006, about 10 384 tonnes of farmed cod (full life cycle) were slaughtered and 214 licenses for cod farming to 104 companies were operational (Directorate of Fisheries, Bergen, Norway.…”

Section: Introductionmentioning

confidence: 99%

Screening and characterisation of potentially pathogenic bacteria associated with Atlantic codGadus morhualarvae: bath challenge trials using a multidish system

Sandlund

Bergh²

2008

Dis. Aquat. Org.

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In intensive aquaculture systems, high concentrations of nutrients and high densities of fish larvae provide favorable conditions for opportunistic pathogenic bacteria to flourish. We screened potentially pathogenic bacterial strains isolated from moribund Atlantic cod Gadus morhua larvae, pollack Pollachius pollachius, coalfish Pollachius virens, Atlantic halibut Hippoglossus hippoglossus, rotifers, algae and water samples from different hatcheries. Three identical challenge experiments tested a total of 53 strains. A multidish system was used: cod eggs were placed in single wells, together with 2 ml of sterile seawater, and exposed to the bacterial cultures. Final bacterial concentrations in the wells were 10 6 and 10 4 CFU ml -1. Eggs and larvae not exposed to bacteria were used as unchallenged controls. Challenged controls were exposed to Vibrio anguillarum strain 610. Eggs were challenged approximately 48 h prior to hatching and mortality was recorded daily throughout the yolk-sac period. In spite of the high challenge dose of 10 6 CFU ml -1, only 5 bacterial strains tested caused higher mortality than the unchallenged controls. Four of these strains were identified by 16S rDNA and gyrase B gene (GyrB) sequencing as resembling V. anguillarum and 1 strain resembled Carnobacterium sp. Most of the larvae exposed to these strains died within 10 d of challenge. Serotyping of the strains resembling V. anguillarum gave inconclusive results. This indicates differences in serology compared to the serotypes O1, O2 and O3, associated with disease. Three bacterial strains seemed to have a slower infection rate, indicating a longer incubation period. The remaining 45 strains did not seem to have a negative effect on larval survival, suggesting that these are not primary pathogens.

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“…During the last few years, substantial progress has been made in developing methods of intense juvenile cod production (Svåsand et al, 2004). Currently, the cost of producing cod from larvae to market-sized fish is too high to make cod farming profitable.…”

Section: Introductionmentioning

confidence: 99%

Effects of water quality and stocking density on growth performance of juvenile cod (Gadus morhua L.)

Björnsson

Ólafsdóttir

2006

ICES Journal of Marine Science

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S. R. 2006. Effects of water quality and stocking density on growth performance of juvenile cod (Gadus morhua L.). e ICES Journal of Marine Science, 63: 326e334.In a 5-month experiment where groups of juvenile cod were reared in a flow-through system at low density (Group 1) and in a recirculating system at low (Group 2) and high densities (Group 3), the recirculated water had negative effects on growth rate, nutritional condition, and mortality. After the first month, mean weight was significantly larger in Group 1 than in the other two groups. The effect of stocking density on mean weight was not significant until the end of the experiment, when densities were 9.0 and 48.3 kg m ÿ3 in Groups 2 and 3, respectively. Initial mean weight of fish was 37.3 g and at the termination of the experiment mean weights were 225.2, 181.8, and 167.9 g in Groups 1, 2, and 3, respectively. After 5 months, mean condition factors were 1.074, 0.965, and 0.946, mean liver indices 9.5, 9.0, and 7.6, and mean mortalities over the course of the experiment were 1.0%, 5.1%, and 2.4% in Groups 1, 2, and 3, respectively. Water temperature (10.4e10.6(C), pH (7.2e7.4) and oxygen concentration (8e10 mg l ÿ1 ) were similar among groups. Concentration of total ammonia nitrogen (TAN) was similar among groups for the first half of the experiment (0.3e0.4), but during the last month it was 0.6, 1.3, and 1.5 mg l ÿ1 in Groups 1, 2, and 3, respectively. There was a negative correlation (r 2 ¼ 0.48, n ¼ 36) between relative growth rate and TAN, suggesting that ammonia may have been a limiting factor in the recirculating system. The apparent threshold limit of TAN for reduced growth was approximately 1 mg l ÿ1 .

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The Status and Perspectives for the Species

Cited by 22 publications

References 67 publications

Comparison of performance of two size groups of farmed cod (Gadus morhua L.) juveniles following transfer to sea cages

Comparison of performance of two size groups of farmed cod (Gadus morhua L.) juveniles following transfer to sea cages

Screening and characterisation of potentially pathogenic bacteria associated with Atlantic codGadus morhualarvae: bath challenge trials using a multidish system

Effects of water quality and stocking density on growth performance of juvenile cod (Gadus morhua L.)

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