The Secret Life inside France’s First Offshore Wind Farm
2025-11-26
// Study Spotlight
How acoustic telemetry reveals how Europe’s energy transition reshapes marine habitats
Estimated reading time: 6–7 minutes
A scientist, a wind farm, and a small shark with a big story
When marine ecologist Lydie Couturier first entered the world of acoustic telemetry, she was tagging manta rays in eastern Australia.
“That’s where I saw the power of a real tracking infrastructure,” she says. Movement maps turned invisible behaviour into something unmistakably clear. “People immediately understand it when you show movement on a map. It speaks to everyone, from scientists to fishermen.”
Years later in France, another question surfaced. Could the same method reveal how offshore wind farms change the lives of the animals living around them?
Europe is scaling up offshore wind energy at record speed. Nowhere is this expansion more visible than along France’s Atlantic coast. Yet while turbine fields reshape the horizon, their ecological impact underwater remains harder to see.
To help close this gap, Lydie and her collaborators launched one of France’s first telemetry-based studies inside an operating wind farm. Their model species: the lesser spotted dogfish (Scyliorhinus canicula), a small benthic shark.
What they discovered inside the Saint Nazaire offshore wind farm is now helping define a new generation of marine impact assessment.
Saint-Nazaire: France’s first operational offshore wind farm and the habitat it creates
Twelve kilometres offshore, Saint-Nazaire’s eighty turbines form a grid that is more than infrastructure. Underwater, each structure reshapes the seascape through:
- artificial reefs around the monopiles
- rocky scour protection where previously only soft sediment existed
- added refuge, structure and shifts in local prey communities
- electromagnetic fields produced by subsea cables
- continuous noise and vibration from turbine operation
For many species, offshore turbines are more than infrastructure – they create an entirely new habitat beneath the surface.
But what does that mean for the lesser spotted dogfish? The species is common across European shelves, relies on structured habitats for feeding and reproduction and often shows strong site fidelity. Yet inside a wind farm, no one knew:
- Do they remain inside the wind farm for long periods?
- Do they use turbines the way they use natural reefs?
- Does this new environment attract or repel them, or alter their seasonal patterns?
To find answers, Lydie’s team deployed Thelma Biotel acoustic receivers around selected turbines. Working with local fishermen, they captured dogfish, performed minimally invasive tag implantation, and released the animals on site.
“It is heavy fieldwork,” Lydie says. “Fifteen kilometers offshore, tight weather windows, tagging surgeries on a moving boat – but the main challenge was actually catching the dogfish.”
Surprising results: A clear tendency for long residency
1. Long residency inside the array
The receivers showed that many tagged dogfish stayed in the wind farm for weeks to months — clear evidence that the turbines supported sustained use rather than attracting brief visitors.
2. One turbine stood out as a hotspot
A single monopile with scour protection, labelled G06, recorded far more detections than all others. Several sharks returned repeatedly, indicating that the mix of boulders and soft patches may offer valuable shelter and foraging opportunities.
3. Seasonal rhythms shaped activity
Detections dropped in the coldest months and increased with rising temperatures. This aligns with known dogfish behaviour and shows that their use of the wind farm follows natural seasonal patterns.
4. Habitat complexity drove site selection
Turbines surrounded by rock protection or mixed substrates saw longer and more frequent visits than rocky bottom areas. Dogfish were present across the farm, but clearly preferred structures resembling natural reef habitat.
Dive deeper in the original study here or via the citation:
Labourgade et al. 2024
What these patterns mean
Scour protection seem to act as a functional hub — providing structure, cover and feeding opportunities that small sharks returned to repeatedly.
“People always ask what fish actually do underwater,” Lydie says. “Telemetry is one of the first non-lethal ways to see their lives. For stakeholders like fishermen it’s very concrete. You can see when the fish are there.”
Wind farms as emerging ecological structures
Taken together — residency, site fidelity and seasonal use — the results show that offshore wind farms could develop into stable ecological features, not just temporary attractants.
Behaviour adapts quickly to human-built environments
Dogfish were believed to not only pass through, but possibly reorganise their activity around specific structures. More data on behaviour prior to windfarm installation is still neccecary, but the results may suggest that the sharks respond directly to habitat complexity and seasonal cues.
Telemetry reveals what traditional surveys can’t
Fine-scale tracking exposed patterns that would otherwise remain invisible: not just presence, but movement pathways, residence times and the specific parts of the wind farm that matter most.
Why this matters now
Offshore wind development in Europe is accelerating:
- The EU plans to triple capacity by 2030
- France is preparing multiple new wind farm zones
- Ecological monitoring still lags behind construction
This study demonstrates that:
- acoustic telemetry works reliably inside operational wind farms
- it generates data that fishermen, developers, and regulators can instantly understand
- it reveals spatial and behavioural patterns classical surveys cannot capture
- it provides urgently needed baseline knowledge for future impact assessments
Most importantly, it shows how marine animals adapt to the new seascapes created by the energy transition.
Linking marine behaviour to Europe’s energy transition
What began with manta rays in Australia has given Lydie the opportunity to step into a European effort to understand how human-built oceans shape marine behaviour.
Lydie now contributes to larger European initiatives such as FISHOWF+, NorTrac and DTOTrack – programs that collectively build a broader understanding of fish movements across the Northeast Atlantic.
“Telemetry lets us be a bit like spies,” she says. “You see where an animal spends time, when it moves and what it uses. And people connect to that — it’s storytelling with data.”
What’s next?
The dogfish study is only the beginning. As offshore energy accelerates, the need for high-resolution behavioural data is rising just as fast. Telemetry is becoming one of the sharpest tools we have to understand how marine life navigates and adapts to an ocean increasingly shaped by human design.
In the next Full Signal installment, we’ll go deeper: inside the wind farms themselves. How do researchers like Lydie operate in these high-energy environments? And how will Europe’s rapidly evolving energy landscape transform the future of marine tracking?
A lot is happening below the surface – join us for a closer look in our next blog post.
Researcher
Dr. Lydie Couturier
Marine ecologist specialising in behaviour, movement ecology and human–ocean interactions. Her work focuses on acoustic telemetry, habitat use in dynamic environments and the design of cross-disciplinary monitoring approaches in offshore environments.
(Links to ResearchGate, LinkedIN)
Thelma Biotel’s Role
This study used Thelma Biotel's acoustic receivers and tags to monitor species behaviour inside the wind farm. The long-term deployments enabled fine-scale insights in one of Europe’s busiest and most acoustically complex marine workplaces.
