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Gastric Dilation, Air Sacculitis Syndrome in Farmed Steelhead Trout and Its Association with Maturation, Nutritional Factors, Osmoregulatory and Environmental Stresses



Steelhead trout is the most popular species cultured in Bay d'Espoir. The ability to reach market size earlier than Atlantic salmon with lower marine cycle has made steelhead a better choice. However, steelhead growers have experienced a serious performance problem in the recent past which had a high impact on the industry. The syndrome is known as Gastric Dilation, Air Sacculitis (GDAS) where the affected fish suffer from increased mortality, reduced growth, distended abdomens, silvering and a high number of fat droplets surfacing over the net pens. The frequency of GDAS seems to increase with an increase in water salinity and also when water temperature decreases. Other factors are related to nutrition and early maturation and possibly the genetics of the trout strain used in Bay d'Espoir, however no definitive cause is yet known. This prompted the industry to the possibility of obtaining a Danish strain to replace the current strain of fish they are using. These efforts are currently underway.

To maximize the productivity of steelhead aquaculture in Newfoundland, Newfoundland Salmon Growers Association (NSGA) in collaboration with Fisheries and Oceans Canada and Newfoundland Department of Fisheries and Aquaculture are aiming to identify the possible cause(s) of GDAS in farmed steelhead trout in Bay d'Espoir and to suggest possible mitigating measures. Standard diagnostic health testing will be performed as well as histopathological and biochemical indexes during the production cycle. Secondly, laboratory trials to reproduce GDAS in steelhead trout will be conducted to identify the role of single and/or multiple factors in the development of the syndrome. Finally, a laboratory comparison between the currently used steelhead strains in Bay d'Espoir farming and those strains used in Denmark, which NSGA are currently trying to import, in relation to their susceptibility to GDAS will be performed in order to help the industry with its decision in regard to such importation.

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)


2005 - 2008


Atlantic: Newfoundland, Labrador Shelves

Principal Investigator(s)

Atef Mansour

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