Offshore Impact on Highly Migratory Species

In the last few decades, a global increase in offshore oil production has resulted in a corresponding decline of marine life. The world’s oceans have been polluted by an estimated 5 trillion gallons of oil. Oil spills are not only lethal to sea life but also to humans and the environment as well.

The highly migratory fish migrate to different areas of the ocean in order to find food. However, due to the offshore oil and gas industry, these species may not be able to migrate as easily.

If you’re an East Coast fisherman, you’re probably aware that state and federal initiatives to generate renewable energy in the form of offshore wind power are increasing. To far, the federal agency in charge of offshore wind development, the Bureau of Ocean Energy Management (BOEM), has granted 16 leases in the Northeast and Mid-Atlantic, covering an area larger than Delaware. Over the next decade, over a thousand wind turbines may be erected off the shore.

There are a slew of studies ongoing to figure out how these constructions may impact our coastal ecosystems and fisheries, whether at the scale of a single wind turbine, a windfarm with hundreds of turbines, or the whole coast. From the perspective of an angler, the most dramatic effects may be for bottom fish—for example, the turbine buildings’ artificial-reef effect may attract species such as black sea bass and tautog, offering fishing possibilities. Until recently, however, little thought has been given to how offshore wind development could affect the distribution of the wide-ranging tuna, sharks, and billfish that are so vital to recreational fishermen along the coast (together known as Highly Migratory Species, or HMS).

Acoustic Tagging as a Starting Point

Dr. Jeff Kneebone, research scientist at the New England Aquarium’s Anderson Cabot Center for Ocean Life, recognized the study gap and started interacting with offshore wind companies and regulators in 2018 to discuss the need to carefully examine HMS. “It’s critical that we understand how offshore wind development affects HMS distribution and abundance, whether it’s due to noise from construction and operation, electromagnetic field generation from transmission cables, changes in currents or water temperature, or the physical structures themselves,” he explained. To assess such effects, the first step is to get a better understanding of the HMS distribution before the windfarms are built—the baseline data.

Kneebone teamed up with Brian Gervelis, a project scientist with INSPIRE Environmental, for a two-year pilot study to assess HMS residency and movements in the southern New England wind-energy areas, with funding from the Massachusetts Clean Energy Center, BOEM, and the Rhode Island Department of Environmental Management. “While recreational fishermen conduct thousands of trips targeting HMS every year all across southern New England,” Gervelis said, “we chose to concentrate our study on three especially popular destinations—Cox Ledge, The Claw, and The Fingers.”

The researchers concentrated on placing acoustic tags on three species in 2020, the study’s first year: bluefin tuna, blue sharks, and shortfin mako sharks. The experiment began with the deployment of acoustic receivers that would “listen” for any fish tagged with acoustic tags, which emit a unique identifying code on a regular basis and may be detected within a quarter-mile of a receiver. They installed 15 acoustic receivers, five in each of the three main fishing locations, with the assistance of Capt. Greg Mataronas, a commercial fisherman from Rhode Island. Individual fish could be followed throughout the area using the acoustic receivers, which were intended to operate together as an array.

Acoustic Marine Receivers The researchers were able to “listen” for tagged fish using fifteen acoustic receivers (blue dots) placed in an array inside the wind lease zones south of Martha’s Vineyard, giving crucial baseline data.

Then came the fun part: deploying tags. Kneebone and Gervelis affixed acoustic tags to bluefin tuna, blue sharks, and shortfin mako sharks across southern New England while sailing with Capt. Rob Taylor of Newport Sportfishing Charters and Capt. Willy Hatch of Machaca Charters. “Acoustic tags may possibly offer us long-term information on fish before, during, and after windfarm construction since they have a battery life of up to seven years,” Kneebone said. “Acoustic tags also provide us with extremely accurate information about movements and habitat usage within the area where acoustic receivers have been placed, as opposed to other technologies such as pop-up satellite tags.” Another advantage is that there are many additional acoustic receiver arrays for other research projects up and down the coast, which means that if a tagged fish swims into one of those arrays, it may be spotted by other scientists.

“On a local level, we’re collaborating with scientists from UMass Dartmouth’s School of Marine Science and Technology and the Massachusetts Division of Marine Fisheries, who have placed 10 more receivers around Cox Ledge as part of a cod spawning study,” Gervelis said. “If our receivers detect their cod, we’ll give them the information, and vice versa.”

To-Date Results

Kneebone and Gervelis had to traverse a lot of territory to locate their target species in 2020, whether it was for study or pleasure. They eventually found their prey and were able to place 29 tags on it: 13 on blue sharks, 8 on shortfin mako sharks, and 8 on bluefin tuna.

They’ve just had a year of tagging and detection data, but they’ve already discovered some intriguing outcomes. “Despite the fact that we tagged the majority of our fish outside of the lease zones, two-thirds of those fish were identified on at least one of the acoustic receivers,” Gervelis said. Half of the bluefin tuna tagged 40 miles south of Montauk were detected a month later by the team’s acoustic receivers on Cox Ledge and the Fingers, indicating that these fish use various locations throughout the season, including the lease areas.

Looking Ahead: HMS Monitoring’s Long-Term Vision

Kneebone and Gervelis aim to target bluefin tuna, blue sharks, and mako sharks in 2021, the project’s second and final year, while also deploying tags on other HMS of interest, including as thresher sharks, dusky sharks, sandbar sharks, and white marlin. Moving ahead, they’ll listen for tagged fish swimming near the arrays (or any other arrays up and down the coast) to learn more about how each species utilizes the regions that may ultimately be used for offshore wind development. Kneebone explained, “We’ll be looking at this baseline distribution data in conjunction with environmental variables like water temperature, Gulf Stream location, and forage fish abundance to help us tease apart whether future changes in their movements and habits are attributable to offshore wind activities.”

Kneebone and Gervelis want to improve baseline HMS data throughout the whole planned windfarm development area, which presently spans from Massachusetts to North Carolina, in the long run and on a larger scale. “Our long-term aim is to collaborate with offshore wind companies to establish a regional HMS monitoring program,” Gervelis added. “We need a consistent methodology to track the effect on each step of the offshore wind development process on HMS—surveying, building, operations, and, eventually, decommissioning. Developers will ultimately be able to determine how various actions impact HMS using such a software and baseline data, which can then be utilized to limit any detrimental effects on both the fish and the humans who target them.”

Frequently Asked Questions

What is a highly migratory species?

A highly migratory species is a species that has a tendency to migrate from one place to another in large numbers.

What organizations is primarily responsible for regulating highly migratory species such as blue fin tuna?

The IATTC is primarily responsible for regulating highly migratory species such as blue fin tuna.

Are sharks highly migratory?

Sharks are highly migratory.

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