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Fivelstad S.,Bergen University College | Kvamme K.,Bergen University College | Handeland S.,University of Bergen | Fivelstad M.,Bergen University College | And 2 more authors.
Aquaculture | Year: 2015

Atlantic salmon (Salmo salar L.) parr (33g start weight) were exposed to five different mean levels of carbon dioxide partial pressure for about five weeks in an open flow system: 0.7mmHg (1.9mgL-1; control group), 3.9mmHg (10mgL-1; low group), 6.5mmHg (17mgL-1; medium group), 9.5mmHg (25mgL-1; high group) and 12.4mmHg (33mgL-1; very high group). The water temperature was 15°C. Plasma chloride concentration decreased linearly with increasing carbon dioxide concentration on days 9, 20 and 37 (p<0.05). The mean reduction in plasma chloride was 0.65mM/(mgL-1 CO2). The specific growth rate (SGR) decreased with decreasing plasma chloride concentration (p<0.05). The relationship between carbon dioxide concentration and SGR can be described using a second-order polynomial model (p<0.01). Based on this second-order polynomial model, SGR is 100% until 15mgL-1 is exceeded and minor reductions occur between 15 and 20mgL-1. However, at higher concentrations the reductions in SGR increase very fast. That the relationship between CO2 and growth was curvilinear rather than linear seems an important overall advance in the state of knowledge. It should also be noted that some fish grew well even at high CO2 concentration (38mgL-1). © 2014 Elsevier B.V.

Karlsbakk E.,Norwegian Institute of Marine Research | Olsen A.B.,Norwegian Veterinary Institute Bergen | Einen A.C.B.,Norwegian Institute of Marine Research | Mo T.A.,Norwegian Veterinary Institute | And 5 more authors.
Aquaculture | Year: 2013

Ballan wrasse (Labrus bergylta) is cultured for the use as cleaner fish in Atlantic salmon farms. A low level of mortality was experienced in ballan wrasse broodstock tanks during spawning. Examined moribund and clinically healthy fish showed patchy gill lesions characteristic of amoebic gill disease (AGD). Microscopy on wet preparations from gill patches showed large numbers of amoebae. Histology revealed pathology characteristic for AGD, such as extensive hyperplasia, bridging of lamellae and forming of interlamellar spaces. Lesions were associated with amoebae, resembling Paramoeba spp. Molecular studies on both gill samples and gill-derived amoeba-cultures showed the presence of Paramoeba perurans. These observations show that cultured ballan wrasse may host P. perurans infections. Since this observation suggests that ballan wrasse may be infected with P. perurans also in nature, the possible role of wrasses in the epizootiology of AGD in salmonid aquaculture needs to be examined. © 2013 The Authors.

Nilsen H.,Norwegian Veterinary Institute Bergen | Johansen R.,Norwegian Veterinary Institute Oslo | Colquhoun D.J.,Norwegian Veterinary Institute Oslo | Kaada I.,VestVet A S | And 3 more authors.
Diseases of Aquatic Organisms | Year: 2011

We describe the first case from Norway of increased mortality in Atlantic salmon Salmo salar (L.), with septicaemia and necrotic myositis, associated with infection by Flavobacterium psychrophilum. The outbreak occurred in smolt of 60 to 100 g in fresh water on a landbased farm in Western Norway during winter 2008-2009. The water temperature was 5°C and the accumulated mortality was 7.0%. Necropsy of dead and moribund fish revealed a swollen dark spleen, pale liver, serohaemorrhagic ascites and haemorrhage in the abdominal fat and muscle. F. psychrophilum was isolated from the kidney and spleen of diseased fish. Muscle biopsy revealed the presence of long filamentous rods in necrotic areas of skeletal muscle. Immunohistochemistry was positive for F. psychrophilum. Identification of cultured isolates as F. psychro - philum was confirmed using phenotypic testing and sequencing of the 16S rRNA gene. Analysis by allele-specific polymerase chain reaction (allele-specific PCR) indicated that 2 different genotypes of the bacterium were present in the outbreak. ©Inter-Research 2011.

Hellberg H.,Norwegian Veterinary Institute Bergen | Vagnes T.B.,Norwegian Veterinary Institute Bergen | Noga E.J.,South Eastern Aquatechnologies Inc.
Fish and Shellfish Immunology | Year: 2013

The morphology, ontogeny and tissue distribution of mast cells were studied in common wolffish (Anarhichas lupus L.) at the larval, juvenile and adult life stages using light and electron-microscopy and immunohistochemistry. Fish were sampled at 1 day, 1, 2, 3, 4, 8 and 12 weeks post-hatching in addition to 6 and 9 months and 2 years and older. From 8 weeks post-hatching, mast cells in common wolffish mainly appeared as oval or rounded cells 8-15μm in diameter with an eccentrically placed, ovoid nucleus and filled with cytoplasmic granules up to 1.2μm in diameter. Granules were refractile and eosinophilic to slightly basophilic in H&E and stained bright red with Martius-scarlet-blue and purple with pinacyanol erythrosinate in formalin-fixed tissues. Mast cells stained positive for piscidin 4 and Fc e{open} RI by immunohistochemistry. From 1 day to 4 weeks post-hatching, immature mast cell containing only a few irregularly sized cytoplasmic granules were observed by light and electron-microscopy in loose connective tissue of cranial areas. From 1 day post-hatching, these cells stained positive for piscidin 4 and Fc e{open} RI by immunohistochemistry. From 12 weeks post-hatching, mast cells showed a primarily perivascular distribution and were particularly closely associated with lymphatic vessels and sinuses. Mast cells were mainly located at the peripheral border of the adventitia of arteries and veins, while they were in intimate contact with the endothelium of the lymphatic vessels. Numerous mast cells were observed in the intestine. A stratum compactum, as described in salmonids, was not observed in wolffish intestine, nor were mast cells confined to a separate layer, a stratum granulosum. Lymphatic vessels consisting of endothelium, intimal connective tissue and a poorly developed basal lamina were observed in the intestine. Scanning electron microscopy was used to compare the structure and localization of intestinal mast cells of common wolffish and rainbow trout. Scanning electron microscopy also revealed endothelial surface features and confirmed the existence of three distinctly different types of vessels in the wolffish intestine. Rainbow trout mast cell granules appeared as intact globular structures while empty vacuoles were observed in common wolffish. Mast cells were closely associated with lymphatic vessels in common wolffish, but not in rainbow trout. © 2013 Elsevier Ltd.

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