Long-term ecological monitoring of offshore aquaculture

Providing scientific evidence on the ecosystem restoration benefits of offshore shellfish aquaculture
Restorative offshore aquaculture
Photo by John Holmyard
Title: Long-term ecological monitoring of offshore shellfish
Funding: Offshore Shellfish Ltd.; Defra; European Maritime and Fisheries Fund (EMFF); Dorset and East Devon Fisheries Local Action Group (FLAG); Pig Shed Trust
Duration: 2013–ongoing (updated December 2024)
 
 
 
The University of Plymouth has been performing long-term monitoring of the UK's first large-scale mussel farm with the aim of exploring its interaction with the surrounding ecosystem. Operated by Offshore Shellfish Ltd., the farm is located three-to-six miles offshore in Lyme Bay, South West England. Once fully operational, it is expected to cover 15.4 square kilometres, over three sites, annually producing up to 10,000 tonnes of mussels.
Since its pre-development, the applied Marine Ecosystems Research (aMER) unit has continuously monitored the farm and its surrounding environment.
Over the years, the research has evolved to address new questions. Early work focused on long-term benthic and pelagic surveys, to monitor any changes in these ecosystems, and then expanded to include studies on the farm's effects on local physical oceanography and plankton. Collaborative efforts with the local fishing community, particularly through projects like Response Of predators to Protection and Enhancement (ROPE) and Spillover, have investigated animal movements within the farm and between the farm and the nearby Lyme Bay Marine Protected Area (MPA).
Offshore mussel farm ecology
Offshore shellfish rope-cultured mussel farm
Bass among the mussel ropes Photo by Dr Llúcia Mascorda-Cabré
European bass among the mussel ropes
The mussel bed below the farm Photo by Dr Llúcia Mascorda-Cabré
Biogenic reef forming below the farm
Building on this foundation, current work – including the Ropes to Reefs project – incorporates techniques such as acoustics and fish tracking to study how fish use the habitat provided by the mussel farm, which includes commercially important fish and crustacean species.
These methods are also used to assess potential spillover effects into adjacent fishing grounds, and to explore connectivity with the nearby Lyme Bay MPA and other aquaculture operations found in the area, which include a scallop farm and a seaweed farm.
Results to date reveal that offshore mussel farming environmental interactions are very different to those produced by other types of aquaculture. Beneath the farm, biogenic reef structures have formed, providing new habitat and contributing to seabed restoration. Both the benthic habitats and the water column around the mussel lines are supporting a greater abundance and diversity of marine life compared to nearby control sites. This includes an increase in commercially important species such as lobster and European bass.
This research continues to deepen our understanding of the farm’s interactions, from individual species to the whole ecosystem, while supporting sustainable aquaculture development.
 
 
 
 
 

Explore our long-term offshore aquaculture research

Led by Dr Emma Sheehan and funded by Offshore Shellfish Ltd, PhD researchers working within the applied Marine Ecosystems Research unit have been instrumental in building the evidence base to assess the environmental interactions of offshore aquaculture.

Ecological Interactions with a Large-Scale Offshore Mussel Farm

Dr Danielle Bridger, 2015–2019
The first PhD to research the ecological interactions of the Offshore Shellfish Ltd. mussel farm in Lyme Bay, building on the baseline monitoring work conducted on the farm since 2013. Danni took a whole-ecosystems approach to the research, investigating every aspect of the ecosystem within and surrounding the farm, from the microscopic to the macroscopic, including plankton, infauna in seabed sediments, mobile and sessile benthic species, and the pelagic water column, plus birds and mammals, and also carried out a socio-economic study.
PhD Dannielle Bridger

Investigating Ecological and Oceanographic Impacts of a Large-Scale Offshore Mussel Farm

Dr Llúcia Mascorda-Cabré, 2019–2023
Llúcia continued the long-term monitoring of the entire ecosystem of the mussel farm and brought in a physical oceanographic component to the research, to assess the impact of the farm infrastructure on localised water circulation within and around the site. Her research also assessed the potential for the farm to create biogenic reef habitat under the mussel lines, as well as potential recovery of the seabed at the site, which was damaged by years of destructive bottom trawling fishing in the area prior to the farm being established.
PhD Llucia Mascorda-Cabre

Assessing the Ecological Value of Offshore Mussel Farming for Fisheries and Conservation

Jake Hebb, 2023–2027
Building on the long-term ecological monitoring at the offshore mussel farm, Jake is incorporating genetic techniques, including eDNA sampling and stomach analysis, to identify feeding behaviours of commercially important species. Alongside this, passive acoustic monitoring is being conducted through the tagging and tracking of lobster movements around the farm using acoustic telemetry. Active acoustic monitoring using an EK80 echo sounder is also being employed to measure fish biomass around the farm infrastructure and to explore potential spillover effects into adjacent fisheries.
PhD Jake Hebb

Key research projects

Find out more about the restorative offshore shellfish aquaculture research carried out by the applied Marine Ecosystems Research unit.

Ropes to Reefs project logo

Ropes to Reefs FISP
Assessing the wider benefits of the UK's first large-scale offshore mussel farm, located in Lyme Bay, off the south coast of Devon.

Managing crab and lobster catches could offer long-term benefits to fishermen and the environment

Spillover
Determining whether economically valuable fisheries species spill over from offshore aquaculture into adjacent fishing grounds.

ROPE

ROPE
Using acoustic tracking to understanding how mussel farms influence the movements of commercially important fish and crustaceans.

Monitoring the recovery of Lyme Bay

Pioneering research in Marine Protected Areas that supports fishing communities while meeting international conservation goals.
Our team provided foundational evidence for the UK Government's whole-site approach, enabling policy development for the recovery and renewal of marine habitats with potential for linked social and economic benefits.
Getty lyme bay
 
 
 

These projects have been supported by a number of funding bodies, partners and supporters

Offshore Shellfish LTD logo

Working in partnership

Much of our work on offshore aquaculture builds upon a long-running partnership between the University and Offshore Shellfish Ltd, and utilises the unique before and after 10-year dataset – generated through PhD studentships supported by the company – that has been collected throughout the development of the farm.
We also work with other organisations directly involved in the UK offshore aquaculture industry, including Scallop Ranch Ltd and local seaweed farmer Biome Algae, along with a range of charitable trusts and government bodies.
 

Funders

Details of project funding:
Long-term mussel farm research and PhDs - Offshore Shellfish Ltd; Ropes to Reefs FISP - Defra; ROPE/Spillover - EMFF and FLAG; Scallop Farming Project - Pig Shed Trust
 

Supporters

Our long-term mussel farm research has been supported by The Fishmongers' Company, who also support the Ropes to Reefs FISP project along with the other supporters listed above.
 
 
 

Historic map reveals how mussel farm is bringing shellfish reefs back to the seabed

A new study highlights how the development of new aquaculture sites in Lyme Bay is enabling the restoration of centuries-old habitats.
The map dating from 1871 which shows shell beds along the coastline of Lyme Bay Hannah Wisdom
 
 
 
 
 

See some of our research in action

 
FISH INTEL

Focus on: Fish Intel Network

The Fish Intel Network (FIN) is a series of underwater acoustic receivers used to track fishes, elasmobranchs and crustaceans. The network has revealed vital habitats for reproduction and feeding, and generated fascinating new insights into species behaviour, including site fidelity and impressive migrations. These novel insights are providing essential evidence to inform ambitious new sustainable ecosystem-based fisheries management and policy.
With receivers located near to mussel farm sites in Lyme Bay, as well as all along the south coast of the UK and the coast of France, the Fish Intel Network provides critical information for improving our understanding of the potential ecological benefits of offshore aquaculture.
 
 
 

Research publications based on our work with long-term mussel farm monitoring

2024
Mascorda-Cabre L, Hosegood P, Attrill MJ, Sheehan EV, (2024) Biogenic reef creation and biodiversity enhancement by an offshore longline mussel farm. Ecological Indicators, Volume 167. https://doi.org/10.1016/j.ecolind.2024.112708
Mascorda-Cabre L, Hosegood P, Attrill MJ, Sheehan EV, (2024) Assessing benthic recovery below the United Kingdom’s first large-scale, offshore, longline mussel farm. Aquaculture Aquaculture Research – Wiley Online Library
Stamp T, Pittman SJ, Holmes L, Rees A, Ciotti BJ, Thatcher H, Davies P, Hall A, Wells G, Olczak A, Sheehan EV (2024) Restorative function of offshore longline mussel farms with ecological benefits for commercial crustacean species. Science of the total Environment. https://doi.org/10.1016/j.scitotenv.2024.174987
Bridger D, Attrill MJ, Rees SE, Sheehan EV (2024) The aggregation effect of offshore mussel farming on pelagic fishes. Aquaculture, Fish and Fisheries. https://doi.org/10.1002/aff2.165
Mascorda-Cabre L, Sheehan EV, Attrill MJ, Hosegood P (2024) Assessing the impact of an offshore longline mussel farm on local water circulation in a highly hydrodynamic energetic bay. Aquaculture https://doi.org/10.1016/j.aquaculture.2024.740697

2023
Mascorda-Cabre L, Hosegood P, Attrill MJ, Bridger D, Sheehan EV (2023) Detecting sediment recovery below an offshore longline mussel farm: A macrobenthic Biological Trait Analysis (BTA). Marine Pollution Bulletin, Volume 195, 2023 https://doi.org/10.1016/j.marpolbul.2023.115556

2022
Bridger D, Attrill MJ, Rees S, Davies B, Mascorda L, Sheehan EV (2022) The restoration potential of offshore mussel farming on degraded seabed habitat. Aquaculture, Fish and Fisheries http://doi.org/10.1002/aff2.77

2021
Mascorda Cabre L, Hosegood P, Attrill M, Bridger D, Sheehan E (2021). Offshore longline mussel farms: a review of oceanographic and ecological interactions to inform future research needs, policy and management. Reviews in Aquaculture. https://onlinelibrary.wiley.com/doi/10.1111/raq.12549

2019
Sheehan EV, Bridger D, Mascorda Cabre L, Cartwright A, Cox D, Rees D, Holmes LA, Pittman SJ (2019) Bivalves boost biodiversity. Journal of the Institute of Food Science and Technology. 33(2): 18-21. https://ifst.onlinelibrary.wiley.com/doi/10.1002/fsat.3302_5.x
 
 
 

Staff involved in our restorative offshore aquaculture research

 
 
 
 

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