DNA chip to monitor fish health

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Scientists are to use an advanced molecular biology technique utilising DNA chips to monitor the health of farmed fish.

Experts from three UK universities are developing a DNA chip which to allow them to monitor the health and performance of farmed Atlantic salmon, Salmo salar, a tool which the scientists claim could save the salmon industry thousands of pounds and help to conserve dwindling fish stocks.

Ordinarily, fish farmers assess the health of their fish by monitoring their behaviour and appearance and looking for the presence of external diseases via mucus scrapes. However, the new DNA chip technique could allow fish farmers and conservationists to determine how healthy stocks with a much greater degree of accuracy.

A DNA chip, or microarray as it is also known, is a tiny silicon chip to which thousands of microscopic DNA samples can be added forming an array that can be profiled to monitor the expression of genes. The technique allows scientists to gather vast amounts of biological data that can be interpreted using complex software that can be used to identify disease genes by comparing expression levels between diseased cells and normal cells.

The development of the DNA chip follows a four-year study known as Salmon TRAITS (Transcription Analysis of Important Traits in Salmon) which is being carried out by scientists at the Universities of Stirling, Aberdeen and Cardiff, together with ARK Genomics at the Roslin Institute and researchers at the Norwegian School of Veterinary Science.

Professor Alan Teale,of the Institute of Aquaculture at the University of Stirling and Co-ordinator of TRAITS said that the new technique is very sensitive and will be extremely useful to the salmon industry:

"What we are working on is precision aquaculture, where we use very sensitive measures - gene expression - to pre-empt any adverse production changes in farmed fish populations as well as to maximise their health and wellbeing. This in turn will increase competitiveness and profitability for the salmon farmer.

"We have identified genes involved in polyunsaturated fatty acid metabolism, protein metabolism, bacterial and viral infection, and freshwater to seawater adaptation.

"The DNA chip will be able to identify changes in the activity of these genes and so alert us to any potential problems. It is too early to tell whether this chip will be a commercial success, but it certainly has the potential to be extremely useful to industry."

The study has revealed genes that play different roles in the lifecycle of the salmon, such as the immune response, which can be monitored for expression as a guage of the health of the fish.

Professor Chris Secombes lead researcher from the University of Aberdeen said: "We have identified hundreds of genes which are increased or decreased following infection, many of which may be indicators of disease.

"We have also looked at what other factors impact on these genes, such as nutrition. We are now working to encode this information onto a chip which could help farmers monitor the health and performance of their stocks through methods such as changing their nutritional intake."