Boost to local fishing?
By Joshua Geaughan / ecoRI News contributor
Since the first offshore wind project
was developed in Rhode Island in 2016, University of Rhode Island researchers
have been attempting to understand their impacts on local marine ecosystems.
That work is continuing with first-year URI Ph.D. student Emmanuel Oyewole’s
study of the artificial reefs that are often found at the base of turbines.
Jonah crabs are being studied in Rhode Island waters
as part of a project examining the effect of offshore
wind turbines on underwater ecosystems.
(Atlantic States Marine Fisheries Commission)
It’s been established through research surrounding offshore wind that the base of turbines serves as a foundation for algae and coral, which acts as a base for a booming ecosystem.
In an attempt to find the cause of this blossoming of
aquatic activity, Oyewole is studying the movement and dietary habits of one
special creature found at the base of offshore wind turbines: Jonah crabs. He’s
working with his academic advisor, Kelton McMahon, an associate professor of
oceanography.
“It’s really, really important for understanding the impact of these wind farms on biodiversity, on ecosystem structure and function, and on fisheries production,” McMahon said.
Jonah crabs were often overlooked by Rhode Island commercial fishermen and were thrown away when caught in lobster traps, according to Oyewole, but as the local lobster population has declined due to overfishing and warming waters, the Jonah crab population has become a viable source of income.
Oyewole said Jonah crabs have seen an increase in market
value and about 70% to 85% of all Jonah crab stock is from the Rhode Island
area. Jonah crab fishing doesn’t require new equipment or infrastructure;
lobster boats can use the same lobster cages to catch the crabs. Although the
market for Jonah crabs is new and growing, understanding the impacts of
offshore wind is important in understanding the future of the market.
“If [the turbines] are aggregating different biomasses from
different areas, that means that you’re having a lot of stock like Jonah crab
stock coming from fishable areas to that particular area, which is less
fishable,” Oyewole said.
To study the crabs’ movements, Oyewole and McMahon are using
isotopic analysis, which can be used to understand the flow of energy through a
food web and reconstruct past environmental and climatic conditions. The
analysis is an “internal or intrinsic biomarker of where you live and what you
eat,” according to Oyewole and McMahon.
“I’m sure you’ve heard the age-old adage you are what you
eat,” McMahon said. “We actually record chemical information about the food we
eat, which can change depending on where you get that food. As you live and
feed in an environment, you take on the isotopic or chemical signal of that
local food source, and we can use that to track organisms and they move across
different places and eat different things.”
Jonah crabs are easy to track using isotopic data due to
their hard shell, or carapace. When a Jonah crab sheds its carapace and molts,
which happens annually, the softer new tissue takes on the isotopic properties
of the place where the shell was developed. Then, as the shell hardens, that
isotopic signal is frozen. Oyewole compares this data to isotopic data taken
from the muscle fiber of the Jonah crab and maps them both.
“This map can tell me if the Jonah crab was here when it was
born,” Oyewole said. “So if a Jonah crab migrated from place to place, the
carapace reading would be [different from the turbine’s location] and the
muscle reading would be [at the turbine].”
The opposite is also true; if the carapace and the muscle
reading are the same, that means the Jonah crab was born and raised next to the
turbine, and wouldn’t have migrated. Additionally, Oyewole is also gathering
metabolic data from Jonah crabs’ stomach acid to see what they have been eating
to better understand why they might be drawn to offshore wind projects.
McMahon said the experimental process is not exclusive to
Jonah crabs, as Oyewole has also been running similar tests on black sea bass.
According to McMahon, black sea bass are historically found in temperate
subtropical waters like that found off the coasts of Delaware and the
Carolinas, but as the water around Rhode Island warms due to climate change,
researchers are starting to see more bass in the same ecosystems created by
offshore wind turbines in which Jonah crabs are found.
“Everyone when they see me asks about my research. [They
ask], ‘Is it good or bad?’ I’m just trying to understand what is happening so
people can know,” Oyewole said.
As part of his research process, Oyewole has gone out on
fishing boats at 4 a.m. with Rhode Island fishermen to gather Jonah crabs for
testing. Oyewole said he has enjoyed his time spent with the fishermen and
described his time on the water as both serene and beautiful.
He said his research is important because it will better
inform both policy and Rhode Island residents, while also helping to demystify
offshore wind. Both Oyewole and McMahon said the public’s impression of
offshore wind farms has been skeptical, and they described how some fishermen
are concerned about fishing near the turbines.
“I think the impression right now is complicated, and I
think rightfully so,” McMahon said. “There are a lot of really important values
that things like renewable offshore wind provide and there are always
challenges that come with it. There’s nothing that we do in the world that’s
all good or all bad, and I think that the way we bridge those challenges is
with sound, reproducible scientific information.”
Oyewole’s own understanding of science is what allowed this
research project to take the shape it has. Oyewole, who came to America from
Nigeria in 2023, graduated from URI’s School of Oceanography program with a
master’s degree in marine affairs, and he did his undergrad studies in
fisheries and aquaculture. Oyewole said he has always been interested in the
way that science can be used to help better inform policy and society at large.
He has used his interest in social science to better inform the outcome of the
research process.
He said he envisions this work being used for both
developing future offshore wind projects and better informing fishermen on the
best spots to fish and which specific fishing industry is strengthened because
of the unique effects of the turbines.
Oyewole explained that if the study finds that the Jonah
crabs are in fact migrating to the turbines, then it could be concluded that
there’s less of a Jonah crab population in the current fishing areas without
turbines. If the turbines are drawing Jonah crabs away from hot spot fishing
areas, Oyewole said the recommendation would be that turbines be developed
further away from those spots. If the Jonah crabs are instead being born at the
base of the turbines, then there will be a spillover effect in the region where
even at the hot spot fishing spots there will be a growing population of Jonah
crabs.
