Deep-water experiment reveals lobsters’ appetite for jellyfish

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Jellyfish could be a “huge” food source for one of the North Sea’s most commercially important catches, scientists have said after filming a Norway lobster feasting on the species usually considered a pest.

A team from Heriot-Watt University was surprised to find lobster scaring off other marine life in order to eat defrosted helmet jellyfish carcasses which has been attached to an underwater camera and lowered 250 metres in the Sognefjorden in western Norway.

The experiment was designed to find out which deep-water species were most attracted by a jellyfish dinner, with hagfish and amphipods expected to be interested.

But it was the Norway lobster – worth around £80 million to Scottish fishing catches – that was most keen and ate half of the jellyfish.

Scientists said it could sustain lobster for three months and the experiment raises new questions about the place of jellyfish in sustainable commercial fishing.

Dr Andrew Sweetman , associate professor of marine benthic ecology in the Lyell Centre at Heriot-Watt, said: “We had no idea that Norway lobster, which is worth £78 million to Scotland alone, fed on the jellyfish carrion that sinks to the depths, so it was very exciting to capture this on camera.

“The Norway lobsters’ feasting was fast and furious. In both deployments, they located the jellyfish in under 25 minutes, scared the other scavengers away almost immediately and consumed over 50% of the carcass.

“We looked at the nutritional value of the jellyfish, along with average Norway lobster energy intakes in the Firth of Clyde, and found that just one of these jellyfish could satisfy the lobster’s energy requirements for up to three months.

“Jellyfish have historically been considered a ‘dead end’ in the marine food chain, and it was only in 2012 that we discovered that anything was using it as a food source.

“To discover that it’s a potentially huge food source for one of the Atlantic and North Sea’s most commercially important catches is really interesting, and raises questions about how jellyfish could contribute to sustainable commercial fishing.”

Although the experiment took place in Norway, the team are confident that lobsters in UK waters will have a similar appetite.

Dr Sweetman said: “There are various species of jellyfish in Scottish waters and lochs, and I’m confident any Norway lobsters in those areas will also be feasting on the carrion.

“An interesting next step would be to find out how the Norway lobster are using the energy from the jellyfish.

“New techniques mean we could label jellyfish tissue with an isotope and trace it in the lobster – so we could actually tell whether it was going into reproductive cells, or helping general growth.”

The research, published in Nature Scientific Reports, was carried out as part of the Jelly Farm project, funded by the Norwegian Research Council and the Fram Centre Fjord and Coast Flagship Program.