Norfolk scientists find cure for cataracts - in salmon

Norfolk scientists have delivered a big boost to a $11bn worldwide industry after identifying a key nutrient that prevents cataracts in salmon.

Norwich Eye Research Group at the University of East Anglia (UEA) has shown how the nutrient histidine, when added to the diet of farmed salmon, prevents the eye condition from developing.

The research is published today in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology.

Following fears over BSE in the early 1990s, blood meal was removed from the diet of farmed salmon. This coincided with a large increase in the incidence of cataracts, which cause economic losses and fish welfare problems.

Lead author Dr Jeremy Rhodes said: 'The international research team of which we are a part has identified a key nutrient (histidine) that is present in high quantities in blood meal but was deficient in the post 1990s diet. We also found that by adding histidine to the salmon's diet, cataracts could be prevented.

'During the life cycle of salmon the young salmon parr spend the early part of their life in fresh water before they enter the sea as salmon smolts where they grow to maturity before returning to fresh water to spawn.

'In this paper, the latest of several from the project, we show that histidine has a protective role in the lenses of salmon, enabling them to withstand the considerable environmental stresses that their life cycle demands. When histidine is deficient in the diet, these environmental stresses lead to the development of cataract.'

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Salmon farming is worth $11bn worldwide and Norway is the largest producer with a 33pc share. Fish farming is Norway's third largest exporter after oil and metals.

A collaboration between the research labs of UEA's Norwich Eye Research Group and the National Institute of Nutrition and Seafood Research (NIFES) in Norway, plus industrial partners Biomar Ltd (Scotland) and Marine Harvest (Norway) was set up in 2004 to investigate the cause of the cataract outbreaks in farmed salmon.

The work of the group has had a global impact on the salmon farming industry and the histidine content of food for farmed salmon has been increased as a direct result.

The full paper will be available at