Mussel farms provide snapper with healthier diets than natural habitats - new study

New research shows snapper living in or around mussel farms in the Hauraki Gulf are eating more nutritious diets than those living in natural habitats.

The project, funded by The Nature Conservancy, is the first of its kind to look at the effect of seaweed and shellfish aquaculture on biodiversity in cold water ecosystems.

The scientists involved said it means properly managed mussel and kelp farms could help repair the ecosystem and restore fish numbers in a marine environment that's been pushed to the brink.

It's no surprise to anyone who's a keen fisher that mussel farms are a spot where you're likely to hook a decent snapper.

University of Auckland marine scientist Dr Andrew Jeffs said that anecdotal knowledge is now backed by scientific research - and the benefits exceed those enjoyed by fishers.

"It's much greater than improving the recreational fishing amenity, it's actually contributing to the wider ecosystem," Dr Jeffs said.

Dr Jeffs said these results are a promising sign that mussel and kelp farms can provide both settlement and nursery habitats and an important source of food for wild fish species.

Due to overfishing and habitat degradation, there's currently not enough food to support the snapper population in the Hauraki Gulf.

"In some places up to 20 percent of the snapper are skinny or have milky flesh syndrome and it looks like they're malnourished," Dr Jeffs said.

He said mussel and seaweed farms could help turn the tide.

"What we were really surprised about was the fact the mussel and kelp farms were behaving at a similar level to really productive natural habitats like rocky reef systems."

Unlike farmed fish, kelp and mussels don't need to be fed and they clean rather than pollute the water.

The Government has a goal to make aquaculture a $3 billion a year industry by 2035, but the industry's success depends on its social licence to operate.

It's hoped the scientific evidence showing the environmental benefits of certain types of aquaculture will give it more value in the eyes of consumers.

"The kelp are taking up the nutrients running off the land and that's particularly important in somewhere like the Hauraki Gulf where we have a lot of nitrogen and phosphorus running off farmland," Dr Jeffs said.

Mussel and kelp farms might prove to be not only a source of high-quality food, but a way to begin to repair a fishery and an ecosystem in c