The influence of nutritional and environmental factors on osmoregulation and cataracts in Atlantic salmon ( Salmo salar L)

• Published in: Aquaculture 2004-06, Vol.235 (1), p.101-122
• Main Authors: Bjerkås, Ellen, Sveier, Harald
• Format: Article
• Language: English
• Subjects: anadromous fish; Animal aquaculture; animal growth; animal nutrition; Animal productions; Aquaculture; Biological and medical sciences; blood plasma; Cataract; Cataracts; Diet; dietary fat; disease incidence; environmental factors; Eye; feeds; fish culture; fish diseases; fish farms; Fundamental and applied biological sciences. Psychology; General aspects; Histidine; Marine; osmoregulation; Risk factors; saline water; Salinity; Salmo salar; Salmon; Smoltification; sodium chloride; Temperature; zinc
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2003.10.005

Cataracts leading to visual disturbance or blindness in farmed Atlantic salmon ( Salmo salar L) in Northern Europe have been a common occurrence during the last years. The cause of cataracts in farmed salmon may be considered multifactorial, with both dietary factors as well as environmental factors involved in cataractogenesis. Deficiency of histidine or histidine-related compounds has been suspected of being a significant contributing factor. In this series of studies, the effect of feeding increased histidine concentrations, as well as feeding a diet with 5% NaCl added before and during smoltification on later cataract development was investigated. The influence of variation in water salinity and temperature on the effect of feed NaCl and histidine concentrations was further studied. In addition, the possible effect of feeding increased histidine and taurine concentrations simultaneously was studied, as well as investigating the potential effect on cataract incidence when feeding moderately elevated histidine level and varying concentrations of dietary zinc and fat. Results showed that increasing dietary histidine levels had a cataract-preventive effect. Adding 5% NaCl to the feed before and during smoltification also reduced cataract frequency and severity. This effect of increasing dietary NaCl level in freshwater seemed to some extent to overrule the effect of increasing dietary histidine on cataract formation in sea water. Fluctuating water salinity and increases in water temperature were also identified as factors contributing to cataract development. No cataract-preventive effects of feeding taurine, zinc, or dietary fat above recommended levels were found. This series of studies showed that several factors contribute to cataract development in farmed Atlantic salmon, and that interaction between factors may be involved.