“We are trying to understand the genetic mechanisms that affect how salmon become resistant to lice,” says Robinson.
He is Australian and a senior scientist at Nofima in Norway, and he has just settled down in a chair in an office in Scotland. Accompanying him is Diego Robledo. He comes from Spain, but he conducts research at the Roslin Institute at the University of Edinburgh. The project that Nick Robinson leads really is international.
Lice and salmon
Sea lice live by eating skin and blood. Salmon become sick and lice are a problem both for fish welfare and for the industry. But there are salmon that do well against salmon lice:
“In wild coho salmon, this occurs naturally. The cells of the salmon surround the lice and kill them,” explains Diego Robledo.
(Image credit: Nofima)
Coho and also pink are two salmon species native to the Pacific Ocean that combat sea lice naturally in a way that Atlantic salmon (the salmon we know from Norwegian rivers and fish farms) are unable to manage.
About sea lice
Sea lice are small parasites, adults six to twelve millimeters long, that feed on the skin and blood of salmonids. When the skin and protective mucous layer are damaged by adult lice, the fish are weakened and become more prone to infections.
Welfare and survival
“Our genomic research is helping us to understand which genes are involved in providing resistance against sea lice in the Pacific salmon species, and the next step in our project is to test the function of these genes in Atlantic salmon using gene editing. Early next year, we will be ready to introduce gene edited Atlantic salmon to sea lice in a closed biosecure facility. We want to see whether small and precise changes disrupting the function of these genes can cause the immune cells in Atlantic salmon to encapsulate the lice and kill them, like occurs in coho, or to prevent attachment like occurs in pink salmon,” says Nick Robinson.
He emphasizes that there is no question of the project editing genes in fish that are going to be grown in the ocean, sold and eaten. The scientists will test which genes can affect whether salmon are able to repel lice infestation. They will look at what happens exactly where the lice attach themselves to the salmon and the importance of genes in relation to stopping the lice.
“The benefits could be large in the future if it is possible to use the knowledge gained from the project to produce a resistant salmon. Lice create wounds that become infected. If we can help the fish to become resistant to lice, it has benefits for fish welfare. By potentially changing the whole epidemiology of lice infection on farms we could also relieve the lice pressure on wild salmon,” he says.
Salmon lice are also more tempted to settle on Atlantic salmon than on other salmon species, such as pink salmon. If scientists find out why, it can help salmon avoid lice altogether.
Risks and benefits
In the project, the scientists will edit genes that their research suggests will keep salmon healthy and the lice away. However, is gene editing safe to use on salmon that are to be farmed and sold? “In each instance, there needs to be a thorough evaluation of how the edit might affect the welfare and health of the fish, the aquatic ecosystem and society. This should involve consumers and other interest groups in the decision-making process. The benefits should be weighed in relation to any potential harms”, say Robinson and Robledo.
Therefore, they have written a guide along with their collaborators from Nofima, University of Edinburgh and Deakin University in Australia, (A guide to assess the use of gene editing in aquaculture) that helps assess the risks of gene editing.
“The guide was written to help assess risks and benefits so that informed decisions can be made,” says Robledo. “How to edit the genes, how to make gene editing part of a research program, how case-by-case applications might affect wild animals, how society views the approach, what benefits it might bring to animal health and welfare, ecology, environmental footprint, human nutrition, and local communities?”
“The changes we are making are quite small. We don’t take genes from other animals, we make slight adjustments to the genes that salmon already have,” explains Robinson.
Pigs and cucumber
Their gene editing guide can just as easily be used on other fish, animals and plants. “We focus on aquaculture, but the guide is just as relevant for other species,” says Robledo. “The questions that need to be asked are the same for livestock or plants. We haven’t seen anything like this guide to gene editing risk assessment published or proposed for these other food species,” says Robinson.
The scientists emphasize that gene editing should not replace regular breeding. This is where you select animals with the best genetic variants for the traits you want, and breed these animals in favorable combinations, so that the best genetic variants are passed on the next generation.
