Finding a hook to tell a scientific story

An offshore mussel farm is restoring not just mussels but a whole eco-system – and the discovery of an old map illustrates its success, as Nicki Holmyard reports.

We have seen a huge upturn in interest in our offshore mussel farm in the past few weeks. Our MD, along with our Plymouth University research team, have had invitations to appear on local and national TV and radio, and friends all over the world have been in touch to tell us they have seen the story.

So, what is the big news and what sparked all the excitement? In reality, to us it is not news. Our research has long shown that the Lyme Bay mussel farm run by Offshore Shellfish is having a beneficial effect on the environment, increasing biodiversity as a result of its floating reef structure, and also building a biogenic reef on a flat, muddy area of seabed that previously had been heavily trawled. Two PhDs have been gained studying the environmental effects of the farm, and many papers published in esteemed journals.

However, the good news rarely caught the eye of the mainstream or even social media, until the chance discovery of an old map, which overnight, became the focus of a story that the general public could relate to.

Dr Emma Sheehan, Associate Professor in Marine Conservation at the University of Plymouth, explains: “I was out shopping with my partner, and we wandered into a gallery where artist Hannah Wisdom knew that we were marine biologists.

“She showed us an old French map from 1871 that had come into her possession from the Marine Biological Association’s collection, because she thought it might be of interest to us. However, she had no idea just how interesting it actually was!”

The map depicted an area of seabed stretching from Torquay in the west and beyond Lyme Regis to the east, and denoted the area as being home to “rich shell beds”, which the scientists believe were likely to have been oyster and/or mussel reefs.

Mussels on the seabed

“This is the exact area that I and my team have been studying in detail for the past 16 years. We have been working with fishing communities along the Lyme Bay coastline to monitor the impacts of the Lyme Bay Marine Protected Area (MPA) since 2008, and the mussel farm since 2013,” Dr Sheehan says.

She adds: “The map immediately changed the way we had been thinking about the mussel farm. Instead of mussels dropping from the lines on the farm causing the creation of new habitats on the barren seabed below, the map revealed that those habitats were actually being restored. Shellfish habitats had been well known and plentiful in the area before they were heavily fished by bottom-towed gear during the 20th century.”

Several parts of Lyme Bay are now designated as an MPA, where trawling is banned, and the use of mobile fishing gear is prohibited by the Devon and Severn Inshore Fisheries Authority (D&S IFCA) in the mussel farm, which is marked on navigation charts as a marine farm.

“Unfortunately, this has not stopped fishing vessels from entering the farm and causing tens if not hundreds of thousands of pounds worth of damage to our gear and stock, and we have several active cases being followed up by our lawyers. However, the recent designation by the IFCA has helped considerably in instantly being able to recognise which vessel has transgressed,” John Holmyard, MD and founder of Offshore Shellfish says.

He explains that extensive surveys of the seabed have been undertaken every year by Plymouth University since before the farm was first set up, adding: “During that time, the seabed beneath the farm’s ropes has started to be transformed. Initially the videos and grab samples showed little or no life, but a muddy sediment clearly criss-crossed with trawl track marks that had limited biodiversity. We are now seeing the area teeming with life, and many commercial fish and crustacean species make use of the farm both as a nursery and a feeding ground.

“This is something that I had anticipated, so it is really exciting to see it happening in real life. The dynamic, high current offshore environment is very different from that found inshore, where mussel farms have been associated in some areas with the build-up of anoxic sediments.”

Mussel ropes

A home for wild lobsters
Dr Sheehan, senior author of the study, published in Science of the Total Environment that first revealed the importance of the map, adds that she had also hoped the mussel farm studies would find evidence of the farm’s potential to restore the health of the seabed.

She says: “We started to notice a change straight away and have consistently seen new species of marine flora and fauna both within the ropes and on the seabed. It is really exciting to think that the farm is not only having a positive impact on the health of the ocean now, but also returning the seabed to some semblance of its former state.”

The Plymouth scientists, using a combination of acoustic tags and underwater monitoring equipment, have found that individual European lobsters (Homarus gammarus) remained beneath the farm for up to 283 days before moving out, providing a resource for local fisheries. The lobsters were found to use both the farm anchors and areas of seabed dominated by fallen mussels for feeding and refuge, in the same way that they use their typical habitat on rocky reefs.

Brown crabs, (Cancer pagurus) on the other hand, showed little willingness to stay within the farm’s infrastructure, and all tagged crabs had left the area of the farm under surveillance within nine days.

The wider benefits of the farm are now being studied in a Fisheries Industry Science Partnership (FISP)-funded project entitled “Ropes to Reefs”.

The project aims to assess the ecosystem services and benefits of offshore mussel farming and the restoration potential of essential fish habitat, along with biodiversity and associated healthy fish stocks. The project also aims to quantify the connectivity of these ecosystem services with the adjacent MPA and spillover effect to fishing grounds.

Dr Sheehan concludes: “Offshore mussel farming has the potential to become one of the world’s most sustainable, large-scale sources of healthy protein. Through the Ropes to Reefs project, we can gauge the industry’s potential benefits far beyond just providing a sustainable source of food.

Working closely with the fishing and mussel farming industry, and building on previous and ongoing research, we can deliver essential evidence regarding the impact of offshore aquaculture. This will enable us to fully assess whether it can serve as a nature-based solution that preserves – if not enhances – the health and productivity of our oceans.”

Nicki Holmyard is a freelance journalist and communications consultant, and a director of Offshore Shellfish Ltd.