There is no evidence that fish farming lead to malformations. While abnormalities are sometimes found in farmed fish, these also occur in wild populations. However, a key difference is that the fish farmers monitor their fish and remove any with abnormalities, so we are more aware of them.

Malformed individual fish appear in variable and unpredictable numbers in farmed stocks in both warm and cold waters, and entail severe losses to the production sector. The similarity of malformation symptoms across fish species and culture environments implies that there is a general causal effect within the rearing conditions of farms, and a wide scope research effort is required when seeking to identify this or these causes.

Available scientific knowledge and practical experience on the causes of malformation problems led to the identification of the following focus areas:

• rearing temperatures, with emphasis on early life stages,
• nutrition, with focus on nutritional quality and impact on bone mineralization of both starter and grower diets, and
• tank environment, including gas supplementation and hydrodynamics.

A series of experimental studies will seek to clarify the impact of the experimental factors, aiming to provide practical guidelines on how to avoid malformations. The experimental fish will be subject to thorough examination, using practical diagnostic procedures and supplementary studies on disease mechanisms, using state-of-the-art methods in morphological as well as molecular sciences.