Deep-water construction impact on fisheries studied

Deep-water wind turbine farms have been built throughout the United Kingdom and in Germany and Denmark, but studies on the effects of their construction on nearby fisheries have been limited, a researcher told a Rhode Island audience.
Frank Thomsen, a researcher with the United Kingdom’s Centre for Environment, Fisheries & Aquaculture, on April 23 told a packed conference hall in Rhode Island that he’s in the early stages of a few studies that could better define some of those effects, specifically related to noise. One study, which will get under way this summer, will put brown trout in cages near the construction of an underwater turbine.
Bringing a new, obtrusive noise into a habitat could have negative effects on the behavior, reproduction rates and the population of fish and other sea creatures, Thomsen said. He pegged the underwater noise of a pile being driven at about 230 decibels, significantly higher than the 130 decibels that a commercial passenger airplane makes. “So it’s much higher – it’s really loud,” he said.
Those sound levels could cause temporary or permanent hearing loss for nearby fish, Thomsen said. That would subsequently affect their “life habits.”
Of course, the effects of any turbine construction would be site and species specific, Thomsen told the crowd at the Rhode Island Natural History Survey’s annual conference: Rhode Island’s Off-Shore Marine Ecosystem and the Potential Impacts of Alternative Energy Development.
But there are similarities between all species and locations. Most fish and cetaceans – dolphins, whales and other mammals – find food, communicate and navigate using sound. “The ocean is, of course, not silent. It’s very noisy,” Thomsen said. “The reason why the ocean is so noisy is that water is a really ideal conductor for sound. Sound travels underwater four times faster than in the air.”
Thomsen said the noise created by a pile being driven is, at about five miles away, greater than the normal, ambient noise in the ocean. “And theoretical models indicate that porpoises would detect this signal at distances perhaps up to 1,000 kilometers,” he added.
And even after the turbines are constructed, there’s still a “suspicion” that they would make a significant amount of noise underwater, Thomsen said.
For the Ocean State’s fishermen, the predictability of marine habits is immensely important, Stephen Medeiros, president of the Rhode Island Saltwater Anglers Association, said in an interview. “Only scientists are going to be able to answer questions” about whether they’ll be affected, he added, “but obviously we have concerns.” Medeiros’ advocacy group is participating in Rhode Island’s Special Area Management Plan process, which will likely help define the offshore area where New Jersey-based Deepwater Wind could build a 100-turbine, $1.5 billion wind farm. “And of course, extensive environmental studies will have to be held before this could ever progress to reality,” Medeiros added.
For anglers, the effects on Rhode Island’s fish population could also be more basic than any large-scale behavior changes. Fish rely on underwater “structure” – anything from valleys to holes to rock piles – that are the “only places fish live,” Medeiros said.
“So, if you suddenly remove a certain rock pile or ledge or oyster bed, you suddenly remove the home for all the creatures that live there,” he said. “If a perfect spot for a wind turbine happened to be right on top of an underwater ledge – something like that – it would displace the animals living there now.”
Medeiros added that it is unclear whether adding turbines to the area would actually create new “structure, which hopefully will draw fish.”
Thomsen said European turbine development companies have come up with noise-mitigation techniques. Those include putting the pile in a “sleeve” as it’s knocked into place and putting a “bubble curtain” around the whole project. But their effectiveness in cutting down noise hasn’t yet been determined and is “mostly of doubtful efficiency,” Thomsen said.
Gov. Donald L. Carcieri, who spoke before Thomsen, said that there is an “urgency” to get Rhode Island’s project under way. The United States’ Atlantic coast has the best wind in the country for such farms, he said.
“We are leading the way. …We said we were going to do this and we’re going to do it right – in the scientific manner,” he said. “That is to bring all the brain power together in terms of how we decide in what parts of the offshore are suitable … for the wind turbines.”
And Medeiros said his group is also concerned about what will happen after the SAMP and construction process. Will fishermen still be allowed to go to their favorite spot, near the turbines?
“We wouldn’t want to loose access to that area. Obviously, we’d never want to see that closed off because the turbines are there,” Medeiros said. “And [we want] to make sure we can fish by these turbines.” &#8226