Pericarditis and myocarditis in farmed Atlantic halibut Hippoglossus hippoglossus.

Farming of Atlantic halibut Hippoglossus hippoglossus is a growing industry in Norway. This study comprises the first description of heart morphology in fish from one Atlantic halibut farm. Fish with no clinical signs of disease were randomly sampled (8 to 12 mo old, weight 1 to 50 g). The hearts were studied by light and electron microscopy and samples were taken from the kidney and pericardial cavity for bacteriological examination. Slight to severe changes were found in most hearts at all samplings. The most serious pericardial and myocardial changes were seen in larger fish (15 to 50 g). In some of the hearts the affected pericardium formed multifocal protrusions. Eight fish had an adhesion between the apex of the ventricle and the parietal wall of the pericardial cavity. Results of bacteriology and immunohistochemistry investigations for common disease agents were negative.