Fort William, United Kingdom
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Leclercq E.,University of Stirling | Taylor J.F.,University of Stirling | Hunter D.,Marine Harvest Scotland Ltd. | Migaud H.,University of Stirling
Aquaculture | Year: 2010

Body size dimorphism between immature and early sexually recruited cohorts of farmed Scottish Atlantic salmon were investigated with the view to optimize the practical management of early maturation over the second-year at sea. Mixed-sex smolts from a single strain and freshwater source were stocked into four discrete commercial sites and sampled at harvest from June to December 2007, 15 to 22 months post-sea transfer. Individuals were sexed and their maturity status was determined based on gonado-somatic-index (GSI) and oocyte leading stage. Whole body weight (BW), fork length (FL) and Fulton condition factor (K) were measured and flesh quality analyzed. The immature mixed-sex population and each gender analyzed separately had an isometric weight-length relationship (WLR) but exhibited seasonal variations in K. Body size of immature Atlantic salmon were consistently sexually dimorphic with males exhibiting a higher BW (+ 13.4%) and FL (+ 5.9%) but a lower K (- 5.0%) than females. Individuals at an early stage of sexual maturation had a significantly higher BW (+ 35.2%) and K (+ 20.6%) than the immature cohort in June and July. During this period BW, FL and K together or BW alone was strong and standard indicators of early maturity in our discrete sites. Body size dimorphism described in this study shows that sex-ratio is an important parameter of farmed Atlantic salmon populations which is likely to vary following weight-grading and that population composition (sex-ratio and maturation rate) affects the seasonality in K typically observed at harvest. Importantly, the commitment of Atlantic salmon into maturation in spring can be rapidly and accurately estimated in a number of discrete populations by using simple weight-length morphological indicators characterized in a single rearing unit. Following maturation rate estimation, weight-grading implemented according to the predicted stock morphological structure could be used to selectively harvest a high proportion of maturing individuals at a stage where their flesh quality remains optimal. This could be applied as a powerful and practical on-site maturation management tool in the salmon industry as well as in other commercially important fish species. Crown Copyright © 2010.

Bell J.G.,University of Stirling | Pratoomyot J.,University of Stirling | Strachan F.,University of Stirling | Henderson R.J.,University of Stirling | And 5 more authors.
Aquaculture | Year: 2010

The present study compared the effects of diets formulated with reduced fishmeal (FM) content and either 100% fish oil (FO) or 100% of a vegetable oil (VO) blend in post-smolts of three family groups of Atlantic salmon. Two groups were selected as being either "Lean" or "Fat" based on estimated breeding values (EBV) for flesh adiposity of their parents derived from a breeding programme, while the third group (CAL) was a mix of non-pedigreed commercial families unrelated to the two groups above. The VO blend comprised rapeseed, palm and a new product, Camelina oil in a ratio of 5/3/2, and diets were fed to duplicate pens of each salmon group. After an ongrowing period of 55. weeks, to reach a mean weight of 3. kg, the fish from all treatments were switched to a decontaminated FO for a further 24. weeks to follow restoration of long-chain n-3 polyunsaturated fatty acids (LC-PUFA) in the fish previously fed VO. Final weights were significantly affected by family group and there was also an interaction between diet and group with Fat and Lean FO fish being larger than the same fish fed VO. Specific growth rate (SGR) was highest in CAL fish (1.01), feed conversion ratio (FCR) was highest in the Lean fish but there were no significant effects on thermal growth coefficient (TGC). Condition Factor (CF) was lowest in CAL fish while the hepato-somatic index (HSI) was highest in Lean fish and viscero-somatic index (VSI) highest in Fat fish. Flesh and viscera lipid content was affected by both family group and diet with a significant interaction between the two. Flesh lipid in fish fed FO was in the order Fat>CAL. >Lean although this order was Fat=Lean>CAL when fed VO. Flesh fatty acid compositions were affected mainly by diet although some minor fatty acids were also influenced by group. Fish fed VO had n-3 LC-PUFA reduced by ~. 65% compared to fish fed FO but this could be restored by a 16-week FO finishing diet phase. The differences observed in lipid and fatty acid deposition suggested that genetics affected lipid deposition and metabolism and that breeding programmes could select for fish that retained more n-3 LC-PUFA in their flesh, particularly when fed diets low in these fatty acids. © 2010 Elsevier B.V.

Frenzl B.,University of Stirling | Stien L.H.,Norwegian Institute of Marine Research | Cockerill D.,Marine Harvest Scotland Ltd | Oppedal F.,Norwegian Institute of Marine Research | And 4 more authors.
Aquaculture | Year: 2014

This paper describes a study in which environmental manipulation of salmon swimming depth was tested in an attempt to reduce farm infection of Atlantic salmon, Salmo salar by the salmon louse, Lepeophtheirus salmonis. The effects of submerged artificial lighting (positioned at 10. m depth) in combination with submerged feeding (delivered at 5. m depth) were tested with respect to salmon swimming depth and sea lice infection, following the hypothesis that L. salmonis infection in a commercial salmon population is reduced when exposed to deep lighting and feeding. This is based on two assumptions, firstly that planktonic L. salmonis larvae principally remain in surface waters (top 4. m) and secondly, that deep lighting and feeding attract salmon to deeper water depths. Results from commercial scale trials confirmed that salmon swimming behaviour is altered under submerged feeding conditions with fish attracted to the feeding corridor during the feeding process. When the fish reached satiation or feeding ceased, they returned to the surface waters during the day. Submerged lighting attracted the fish to the illuminated water depths during the night. During the day, natural light overruled these effects to some extent. The number of L. salmonis on fish exposed to deep submerged lighting was significantly lower than the number of lice found on salmon in cages with surface lighting during the summer months. Submerged feeding showed no advantage over surface feeding with respect to the number of L. salmonis found in these trials. The results of the study suggest that swimming depth manipulation can be used at a commercial scale to reduce salmon lice burdens on Atlantic salmon stocks. © 2014.

Leclercq E.,University of Stirling | Dick J.R.,University of Stirling | Taylor J.F.,University of Stirling | Bell J.G.,University of Stirling | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010

The external coloration of fish is a key driver in consumer buying decisions and is typically altered during sexual maturation in salmonids. Farmed Atlantic salmon (Salmo salar L.) exhibiting distinct phenotypes from the typical silver and nuptial coloration were described in terms of sexual development, flesh quality, and skin pigment profiles. Reconditioning of skin coloration during storage was also tested (CIE[1976]L*a*b*) with the overall view to optimize quality management. The intermediary phenotype never reflected significant deteriorations of flesh quality. It originated from a lack of purine pigments (guanine and hypoxanthine), revealing the carotenoid compounds dominated by the yellow-orange β-carotene. The resulting distinctive lightness and yellowness were reduced by direct ice contact at a post-mortem stage. Storage conditions can be optimized to improve and standardize the coloration of whole-fish, yielding superior flesh quality parameters. This would facilitate product quality grading during primary processing and also increase product acceptance and attractiveness. © 2010 American Chemical Society.

Frenzl B.,University of Stirling | Migaud H.,University of Stirling | Fjelldal P.G.,Norwegian Institute of Marine Research | Shinn A.P.,University of Stirling | And 5 more authors.
Pest Management Science | Year: 2014

BACKGROUND: Sea lice infection is the most expensive disease factor for Atlantic salmon sea-cage farming. For triploid salmon to be accepted as a commercial possibility, investigation of susceptibility of triploid salmon to sea lice infection is a fundamental milestone. The susceptibility of diploid and triploid salmon to infection with Lepeophtheirus salmonis was examined in a tank trial in Scotla tank trial in Norway and a cage trial in Scotland. RESULTS: Following a single infection challenge, results indicated a significant correlation between fish size and the number of attached sea lice. Triploid fish were larger than diploids at the smolt stage. In the tank trials, no difference was found between infection levels on diploids and triploids after a single infection challenge. The tank trial in Scotland continued with a second infection challenge of the same fish, which also showed no infection differences between ploidies. A borderline correlation between first infection and re-infection intensity was found for PIT-tagged diploid salmon examined after each challenge. No significant difference in louse infection between diploid and triploid salmon (∼2kg) was found in the cage trial undertaken under commercial conditions. CONCLUSION: This study concludes that triploid Atlantic salmon are not more susceptible to sea louse infection than diploid fish. © 2013 Society of Chemical Industry.

Agency: European Commission | Branch: FP7 | Program: BSG-SME | Phase: SME-1 | Award Amount: 1.34M | Year: 2008

With the rapid growth of aquaculture seen in recent years, one major fundamental problem has arisen being the environmental pollution due to increased numbers of escapee fish interacting with wild populations. A greater public awareness, the need to protect natural resources and increase the food safety requires the development and implementation of new environmental regulations. There is therefore an urgent need to address this negative environmental impact of salmon farming. To date, two means are available 1) preventing fish escaping by improving cage design and containment or 2) produce sterile fish. Although considerable technological advances have been made in the design of cage systems, no system will be fully reliable as escapees through natural disasters are inevitable. Therefore, there is a clear need to revive the previously abandoned triploid concept as the only means, known to date, to address the environmental impact of escapees contributing to genetic pollution. Furthermore, the production of sterile fish would be very beneficial to salmon breeders as a way to protect their domesticated stocks which are the result of long and costly selection processes aiming to improve important traits such as disease resistance, growth performance and flesh quality. Triploidy would also alleviate early maturation problems and subsequent welfare associated infringements and decreased quality standards. However, prior to discussing the potential implementation of such a radical change within the salmon farming industry, previously based on equivocal results, a sounder understanding of triploid requirements and performances is needed at a commercial scale given the significant advancement in rearing protocols made throughout the production cycle over the last decades. It is only through the establishment of a strong trans-national collaboration supported by key players of the salmon industry that such a project can be undertaken.

Robbins C.,Grallator | Gettinby G.,University of Strathclyde | Lees F.,University of Strathclyde | Baillie M.,University of Strathclyde | And 2 more authors.
Aquaculture | Year: 2010

At a time when sea lice control is a major issue for salmon aquaculture worldwide it has become imperative that scant veterinary medicinal resources for the treatment of fish on farms should be conserved and used effectively. This communication reports the use of the mathematical simulation model SLiDESim to investigate how best to administer cypermethrin bath treatments on Scottish salmon (Salmon salar L.) farms to control the challenge from lice (Lepeophtheirus salmonis) during a two-year production cycle. It was found that these topical treatments are most effective when administered in pairs approximately six weeks apart. Timing of treatment is critical and depends on the number of treatments administered over the production cycle. For 4, 5 or 6 treatments during a two-year production cycle, SLiDESim indicated that the first pair of treatments is best initiated in autumn of the first year of production with the second pair starting between 13 and 18. weeks later. This strategy can produce considerable gains in the predicted reduction of sea lice levels when compared with those historically observed when using cypermethrin on Scottish farms. The effects of altered efficacy were also explored using the model and indicate that even a moderate reduction in treatment efficacy can have considerable impacts on lice control over a production cycle. The SLiDESim computer model provides a framework to explore the more efficient use of veterinary treatments for the control of sea lice on salmon farms. © 2010.

Biomar Group A S, Marine Harvest Scotland Ltd and University of Glasgow | Date: 2016-06-29

The present invention relates to methods for determining pathological tissue damage in fish. Also the present invention relates to methods for diagnosing infectious disease in fish. In particular, the present invention is based on the surprising finding that mixing fish serum with an aqueous protein precipitation solution according to the present invention will result in a protein precipitation reaction if the fish is suffering from pathological tissue damage. Moreover it was surprisingly observed that the degree of turbidity of the precipitate in the mix of sample and aqueous protein precipitation solution was dependent on the state of infectious disease in fish.

Agency: GTR | Branch: Innovate UK | Program: | Phase: Collaborative Research & Development | Award Amount: 770.40K | Year: 2014

The production and farming of triploid salmon, which are reproductively sterile, could be a highly beneficial culture option to industry to help prevent potential interbreeding between farmed escapees and wild salmon populations, thus allowing sustainable and environmentally sound aquaculture to be practiced whilst maintaining a food product of high nutritional quality and health status beneficial to the human diet. However, although triploid salmon can be easily produced, significant problems during culture have prevented the adoption of this technology within the farming sector.The proposed research seeks to overcome welfare concerns and production bottlenecks associated with the farming of reproductively sterile triploid Atlantic salmon in order to reduce the environmental impact and increase the sustainability of the aquaculture industry in the UK.

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