Fish oil extracted from plant seeds
Scientists have genetically engineered plant seeds to contain Omega-3 fatty acids normally found in oily fish.
Seeds from Camelina sativa (false flax) plants were modified using genes from microalgae - the primary organisms that produce these fatty acids.
The oil has now been incorporated into salmon feed to assess whether it's a viable alternative to wild fish oils.
It is hoped that the transgenic plants will provide a more environmentally friendly source of the oil.
The work is published in Plant journal.
Fish do not produce Omega-3 naturally, rather they get it from the algae in the marine environment which then moves up the food chain.
Farmed salmon are therefore given feed containing fish oil in order to mimic their natural feeding habits and crucially, so that they contain the essential fatty acids we need in our diet.
Johnathan Napier, associate director at Rothamsted Research, said that the finished product he helped produce represented a "sustainable, terrestrial source of fish oils, which is really exciting".
"One of the problems with the current supplies of fish oils is that fish stocks are a diminishing natural resource," Prof Napier told BBC Radio 4's Inside Science programme.
"What we're trying to do here is provide an alternative, sustainable source of fish oils."
Although Omega-3 can be obtained from some nuts, seeds and vegetables, it is only in the marine environment, in algae and fish, where the long-chain forms of Omega-3 are found - docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which we need in our diet.
Prof Napier said that the next step was to see if the oil from the transgenic plants had similar properties to natural fish oil.
"Ultimately we think it could be really useful as a contribution to human health and nutrition as an alternative source of fish oils, but that's something that needs to be tested and evaluated by the appropriate regulators," he said.
"It's still an experiment, it's a very big experiment but at the moment there's no possibility this is going to enter the human food chain."
Commenting on the work, Colin Lazarus from Bristol University, who has previously put genes from fatty acids into other plants, said he hoped the oil would be a "standard bearer for introducing GM to the industry".
"I'm delighted the work has come this far. 10 years ago we demonstrated that higher plants could produce these polyunsaturated fatty acids, but we didn't attempt to direct the synthesis to seeds.
"What's not realised generally is that fish don't make these oils themselves. Genetic modification and sustainability are clearly not mutually exclusive."
A team at the University of Stirling has already incorporated the oil into salmon feed. It will now analyse the fish to see if the properties are the same as those given their usual feed.
Douglas Tocher, from the University of Stirling's Institute of Aquaculture, said that on first glance the composition of the fish from the feeding trials was the same.
"There isn't enough fish meal and fish oil being produced in the world to sustain the great increase we're seeing in aquaculture production. The beauty and great breakthrough is that we are now looking at an alternative to fish oil.
"The conventional vegetable oils are good at feeding fish but do not supply the long-chain Omega-3 that we require fish to have in order for them to be a nutritionally high quality product," Prof Tocher told BBC News.