Offshore renewable energy improves habitat, increases fish

Underwater renewable energy structure

Underwater renewable energy structures provide habitat for juvenile fish as they grow. Photo by Udo van Dongen, Bureau Waardenburg

Offshore turbines and other renewable energy structures can have beneficial impacts on seafloor habitats and fish communities, said researchers from Belgium and the U.K. at a recent webinar on lessons learned from offshore renewable energy. 

The European scientists, whose countries have a long history with offshore renewable energy, shared their findings with U.S. colleagues who are eyeing proposals for thousands of offshore wind turbines to be installed in the U.S. Atlantic.

Andy Lipsky, who serves as the fisheries and offshore wind science lead for NOAA’s Northeast Fisheries Science Center, said, “It’s vital that we understand how these offshore wind developments interact with [other] existing uses and with our ecosystem.” He added that the U.S. has important wildlife and fisheries in the areas where the offshore wind farms are planned “and so sharing lessons learned from our European colleagues is vitally important.”

Jan Vanaverbeke, a senior scientist at the Royal Belgian Institute for Natural Sciences, Operational Directorate Natural Environment, Marine Ecology and Management Group, and a visiting professor at Ghent University, Belgium, said that scientists know that there is high biodiversity around the turbines, but researchers sought to determine whether the turbines are simply aggregators of fish, meaning they attract them from elsewhere, or whether they contribute to secondary production, meaning that because of the turbines there are actually higher numbers of fish in the water.

For the two commercial species that they studied at a Belgian offshore wind farm, researchers found evidence that the wind turbines not only attracted fish, providing both shelter and food (from the organisms that grew on the turbines), but also served a role in their life cycle, with young fish attracted to the wind farm where they would grow, then leave to spawn, and then other juveniles would come to the wind farm to grow. In a separate study, they also found that the presence of filter feeders on the turbines, such as mussels, increased the nutrients in the seafloor around the turbines. 

Emma Sheehan, a senior research fellow at the School of Biological and Marine Sciences and Faculty of Science and Engineering at the University of Plymouth, United Kingdom, looked at the impacts of wind farms and wave energy structures on seafloor habitats and species. She also talked about the interactions of offshore mussel aquaculture and fisheries. Her group’s research has shown that “in areas that were heavily degraded seabed, we’ve seen that the mussel shell fallout onto the seabed habitat seems to be increasing biodiversity. It’s restoring benthic habitats. It’s also increasing the benthic commercially valuable species such as lobster and crab on the seabed,” she said, as well as increasing commercially valuable bait species that fishermen will gather for use as they head off to their traditional fishing grounds.

Despite these positive findings, and despite the potential that both researchers talked about for utilizing these installations for aquaculture, these offshore renewable energy developments do take away access for fishing vessels due to the navigation hazards that the structures present. 

“We’re really pushing to try and manage the sites to optimize their benefits because the seabed can only take so much. So if we just keep adding structures … that’s not a good thing. But if you manage them to be, you know, as good as they can, then to me that I can justify that more,” Sheehan said.

Offshore windmills in Belgium

Wind turbines being constructed on the Thornton Bank, on the Belgian part of the North Sea. © Hans Hillewaert / CC BY-SA 4.0

 

Q&A:
The following section has been edited for length and clarity.

Julia Livermore, supervising biologist with the Rhode Island Department of Environmental Management’s (RIDEM) Division of Marine Fisheries: Emma, you mentioned that the wind farms in Europe have kind of acted as de facto marine protected areas. In the U.S., we’re actually trying to ensure that fishing will be able to continue operating in wind farm areas. I’m curious if the benefits of habitat creation might be negated by fishing activity or if that’s something that we don’t have to be worried about because the benthic habitat benefits occurred very close to the turbine foundations, where fishing is less likely to occur.

Emma Sheehan: From my point of view … I just think that so little of the seabed is protected. [In the U.K., MPAs are] tiny, tiny, protected [areas] from any types of fishing. So I just see this [offshore renewable energy] as a massive opportunity on a worldwide scale to provide some really good protection for our seabed that can then help us start recovering the systems that are so degraded, even maybe better than MPAs because they’re kind of all delineated, and they’ve got structure in the sea. So I think that even though impact of the turbine [is] in quite a local area, if you then just mask the area around it from, you know, destructive fishing activity, it would then probably … recover, and therefore the whole area is more valuable, and then the spillover potential would be more valuable. 

Fred Mattera, via chat: I have seen reports that UK fishermen state that there are few cod around the wind farms and they need to relocate their activities.

Jan Vanaverbeke: There is this newspaper stuff popping up nowadays that says, okay, offshore wind farms are scaring the fish away. But this is really not based in anything. This is fake news. 

Emma Sheehan: I can’t comment on this exact story, but what I know from a lot of experience is that whenever something new is coming, whether it be an MPA, or offshore mussel farm, there is always such resistance. I mean, there’s resistance if I, you know, if I just want to deploy a receiver on the seabed, it’s the natural response … to push back, and I think that’s to defend areas of the sea that they’ve had exclusivity on for a long time. But the good news is that over time, what we’ve shown is the advantages of these [MPAs]. So, at the MPA we’ve seen a lot of fishermen who change gear types to take advantage of the MPA to use more benign fishing methods, or even at the mussel farm, we’ve started seeing fishermen that tow around the edge of the mussel farm and will actually exchange a bag of fish with a bag of mussels with the farmers. So there’s always resistance and there’s always this conflict at the start, [but] if they’re managed correctly to optimize the whole marine environment, then I think they can help build new relationships.

Andy Lipsky: There’s some conversation [in the chat] about [how] marine protected areas can be established for a variety of [purposes] and some marine protected areas don’t eliminate commercial and recreational fisheries from these areas, so it’s important for us to understand the definition of MPAs and how we apply them, particularly in the context of obtaining benefits or not obtaining benefits when considering MPAs within the wind farm context.

Emma Sheehan:  MPA is actually quite an unuseful term really, because it … actually means nothing apart from delineating an area and someone claiming it’s an area protected. So, I’m using this term really loosely, to talk generally. The MPA that I am drawing some of these stories from was the first the U.K. at that scale to adopt the whole-site approach. So everywhere else … MPAs have the feature-based approach [which may only protect] very specific identified features that can be absolutely tiny compared to the area that MPAA [covers]. The Marine Conservation Society has actually quantified that difference. And it’s called the MPA Reality Check. And it’s a really great piece of work. So what we’ve learned by protecting the whole site is just the massive benefits in our whole area and the more we learn about marine ecosystems, they don’t just work in isolation on single uses, they have life history stages that use different habitats, so it makes sense to protect whole areas.

David Bethoney, Executive Director of the Commercial Fisheries Research Foundation: There’s a specific … area that’s utilized by fishermen here, yet they’re going to develop a wind farm right on top of it; that is really forefront for us as a concern. 

Emma Sheehan: I don’t know your waters well … [but if] we have got really good habitat and we have other places to develop … that’s the sort of area to me that should just be protected. And so I wouldn’t like to see the loss of important habitats.

A recording of this webinar may be viewed online. It was the second in a series of four sponsored by Rhode Island Sea Grant and the Coastal Resources Center with the International Council for the Exploration of the Sea (ICES) Working Group on Marine Benthal Renewable Energy Developments (WGMBRED) and Venture Café & District Hall Providence to share lessons learned from offshore renewable energy development. All webinars are free. For more information, visit https://seagrant.gso.uri.edu/special-programs/baird/.