Robust Nile fish to aid sick salmon

August 28, 1998

The observation by fish farmers that some fish families are more resistant to disease than others is to be exploited by researchers at Stirling University.

Randolph Richards, John Sargent and Brendan McAndrew of Stirling's Institute of Aquaculture have hooked a total of Pounds 1,945,800 from the university, the Scottish Higher Education Funding Council and the Natural Environment Research Council for a four-year research programme called Aquagene.

Researchers at NERC's Unit of Aquatic Biochemistry, also based at Stirling, will be integrated into the research programme. It will cover the five main areas of aquatic research: fish disease, reproduction and genetics, environment, nutrition and aquatic systems.

The main thrust of Aquagene will be the genetic manipulation of fish and shellfish to improve production efficiency.

William Crowe, of the Scottish Salmon Grower's Association, said:

"Aquaculture is only 25 years old compared with agriculture's 150 years. It's really catching up with agricultural technologies and pushing forward the frontiers of science."

Also joining the team is Alan Teale as professor of aquatic molecular genetics. The fact that he has never worked with fish before reflects the youthfulness of aquatic science. Professor Teale joins Stirling from the International Livestock Research Institute in Nairobi.

"Gene mapping is a numbers game," said Professor Teale. "Fish breed very fast in large numbers so the pace of scientific advance is potentially very great."

The institute will not introduce non-parent genes into embryos. Professor Richards, director of the institute, said that the aquatic equivalent of Dolly the sheep was possible, but the industry was against it.

Instead, the researchers at Stirling will identify and "tag" trait-specific genes in fish. The tagged genes will be those useful to commercial fish production, including disease resistance, growth, appetite, nutritional requirements and behaviour. Such "tagging" of the genome will allow the screening of whole populations of fish and shellfish with that particular gene.

Researchers will be able to breed fish and shellfish by "marker-assisted breeding" in close collaboration with British salmon and trout farmers and the shellfish industry in Southeast Asia. The fish will become resistant to environmental pathogens, in a slower, less dramatic, more natural, way than by transgenic methods.

Tilapia, a tropical fish, holds the key to disease resistance. Having evolved in the Nile Delta, tilapia can breed very fast in high densities, live in dirty waters and appear to be robustly resistant to bacterial disease. Professor Teale aims to take "the benefit of millions of years of tilapia evolution to the salmon" and fight salmon's most common diseases.

Another potential approach for controlling bacterial diseases is to use their own enemies, bacteriphages, which infect and kill bacteria. The Stirling scientists now have the molecular genetics to use the "natural parasites of bacteria to control them" and improve health in fish.

"Twenty-five years ago we thought immunology was the answer to everything but people are coming to terms with the fact that vaccines do not exist for everything out there," said Professor Teale. The new approach will be "affordable, sustainable" and the potential spin-offs "enormous".

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