Culture du saumon de l'Atlantique Salmo salar en eau salée dans l'estuaire du St-Laurent,Québec (Canada) avec hivernage en eau douce

On most of the eastern coast of Canada, the seawater is too cold during the winter to keep the Atlantic salmon Salmo salar continually. The authors therefore reared salmon in the St Lawrence estuary during the summer of 1983 and during the winter transferred them to the aux Outardes river and subsequently to a fish rearing station. They were put back in seawater the following summer until the fall of 1984. In 1983, a group of salmon, used for comparison, was reared in freshwater only. Starting with a mean weight of 43 g, an average weight of 1·28 kg after 17·3 months and a mean instantaneous growth rate of 0·64 % day⁻¹ were reached. The fish in seawater showed a better growth, ratio of feed to flesh conversion and rate of survival than the fish in freshwater. Despite a low survival of 32 %, it is concluded that the rearing of Atlantic salmon in seawater involving a wintering in freshwater is technically and biologically feasible. The heavy mortalities and the low growth can be explained by the fact that the fish were underfed at the beginning of the experiment.     

Mise en evidence de lésions epithéliales digestives et olfactives chez les poissons,au moyen du microscope electronique à balayage

Scanning electron microscopy was successfully used for studying some histological alterations observed in two farmed fish of aquacultural interest: the gilthead bream, Sparus auratus, and the sea bass, Dicentrarchus labrax.In the gilthead bream, several types of abnormality were observed in the mid-gut: protuberance of the apical cell surface, multiplication of mucous cells, exulcerations and, in particular, regression of microvilli from the enterocyte surface.In the sea bass, lesions occurred in the olfactory epithelium, with the disappearance of cilia and microvilli of the receptor cells and the agglutination of cilia of the non-receptor cells.