Skeletal deformities and cardiac growth dynamics in underyearling Atlantic salmon smolts (out-of-season, 0+ smolts)

The proposal addresses the topic of production related problems identified as a priority in the strategic plan for "Havbruk" published by the Norwegian Research Council. Deformities in fish are a recurrent problem in aquaculture, and the industry is face d with loss of money as well as a bad reputation due to these problems. Field data indicate that fish transferred to sea as underyearlings are more susceptible to vertebral deformities than yearlings, and that cardiac development may be inferior in these fish. The project builds on recent advances in research on the relation between intensive fish farming procedures and causal factors for bone deformities in Atlantic salmon. The project aims to include basic studies on growth dynamics for skeletal and ca rdiac structures in relation to rearing methods for underyearling smolts, as well as applied studies of direct relevance to the industry. The project will include two long term rearing experiments and will address temperature conditions, vaccination stra tegies, rearing density and water quality in freshwater. The effects of these factors, individually and in combination, will be examined by means of a range of methods, including growth dynamics and morphometric analyses, radiography and image analyses, m icroscopy and molecular studies. The fish will be monitored no less than six months after seawater transfer, and as close up to harvest size as practical conditions allow. Special focus will be on vertebral deformities and on cardiac size and form.