New research suggests that the UK’s first large-scale offshore mussel farm may actually function as a means of ecological restoration rather than introducing entirely new habitats to the area. An 1871 map indicates that a significant portion of the seabed, stretching from Torquay in the west to Lyme Regis in the east, was once home to “rich shell beds.” The region has transformed from muddy sediment with low biodiversity to thriving reefs, which studies indicate could support various commercial fish and crustacean species, along with enhancing the overall ecosystem.
The UK’s inaugural large-scale offshore mussel farm is facilitating the return of shellfish reefs to sections of England’s south coast seabed for the first time in nearly 150 years, according to new findings.
Over the last ten years, researchers have been investigating the environmental effects of the mussel farm, which was established in Lyme Bay, South Devon, in 2013.
During this period, the seabed under the farm’s ropes has begun to evolve as mussels from the lines settle on the seabed beneath.
This change has led to a shift from mud with minimal biodiversity to thriving reefs, which studies have indicated can benefit various commercial fish and crustacean species, as well as the ecosystem as a whole.
However, a recently discovered historic map—uncovered by an artist from Devon—suggests that this might be a case of restoration, rather than the creation of entirely new habitats.
This French map from 1871 describes a vast region of the seabed, extending from Torquay in the west to Lyme Regis in the east, as home to “rich shell beds.”
Scientists suspect these were likely oysters or mussel reefs that have been lost due to bottom-towed fishing methods used in the 20th century.
Following restrictions on such fishing practices due to the designation of the Lyme Bay Marine Protected Area (MPA), and with the mussel farm located above these ancient shell beds, the area is poised to regain shellfish reefs once again.
The map, part of the Marine Biological Association’s collection, has been donated to artist Hannah Wisdom, who shared it with researchers from the University of Plymouth. These scientists have been collaborating with fishing communities along the Lyme Bay coast to monitor the effects of the MPA since 2008, as well as the mussel farm since 2013.
Dr. Emma Sheehan, an Associate Professor in Marine Conservation and the lead author of the study, stated: “When we initially began monitoring the mussel farm in 2013, we aimed to uncover evidence of its potential to restore the seabed’s health. We have consistently demonstrated that, with new marine flora and fauna frequently observed around its ropes and the seabed. However, discovering that such habitats existed in this region 150 years ago is incredibly thrilling. It demonstrates that the farm not only has a favorable impact on the ocean’s health today but is also helping to restore the seabed to a semblance of its former self.”
In the study published in Science of the Total Environment, researchers underscore how the newly created shellfish reefs are benefiting various commercially significant species.
Using a combination of acoustic tags and underwater monitoring equipment, researchers found that individual European lobsters (Homarus gammarus) remained under the farm for as long as 283 days, utilizing both the farm’s anchors and areas of seabed enriched with fallen mussels for feeding and shelter.
In contrast, brown crabs (Cancer pagurus) displayed little inclination to remain within the farm’s structures, leaving the observed area within nine days.
This may suggest that the mussel farm is providing refuge and feeding opportunities for lobsters and crabs similar to those found in their natural rocky reef habitats.
John Holmyard, the Managing Director at Offshore Shellfish Ltd, which oversees the Lyme Bay mussel farm, commented: “These results indicate that a previously flat, muddy, and degraded seabed can be revitalized into a productive, biodiverse habitat. Through strategically placing an offshore mussel farm, we’re creating effects comparable to those seen from protecting rocky reef areas. This provides lobsters and crabs the opportunity to feed and grow safely before moving out to support surrounding fisheries.”
