February 23, 2017
Study: Seismic Testing Disrupts Fish Behavior
By Brad Rich
Coastal Review Online
anyone who’s thrown a hook in the water to catch a fish in a quiet
atmosphere probably knows intuitively that loud noises spook them: you
don’t scream at fish to bite, after all, you wait patiently.
intuition isn’t science, and seismic airguns don’t make just any loud
noise, so when University of North Carolina Institute of Marine
Sciences doctoral student Avery Paxton and some colleagues got the
opportunity to do some real science on an issue that’s germane to the
hot topic of oil and gas exploration by seismic surveys, they jumped at
What they found, back in September 2014 when they
did a study during a National Science Foundation seismic mapping effort
in the Atlantic Ocean off Beaufort Inlet, not only confirmed intuition,
but surprised them in its degree: 78 percent of the fish on a reef near
the seismic survey “went missing,” compared to counts at the same time
the three previous days during the evening hours, the peak time for
fish, such as snapper, grouper and angelfish, to gather there.
had been hundreds of fish in the evenings before the survey took
place,” Paxton said. “The numbers had been low to moderate in the
morning and afternoon, but what we found was that after the survey, it
(fish numbers) did not peak like it usually does in the evening.”
got the numbers by painstakingly counting the fish on the videos, even
by species. They had collected 10-second-long videos every 20 minutes
for three days, before and through the day when the seismic surveying
“Noises from seismic surveying were audible as
discrete airgun shots in video recordings, allowing us to associate any
observed behavioral responses with timing of individual shots. To
prevent observer bias, fish were first counted with video sound turned
off; then sound was turned back on to detect whether shots were
present,” the paper states.
It was, Paxton said, as if only one
of five members of a human family came home in the evening after school
and work. You’re not sure where they went, or how long they stayed away
from the house, but they sure weren’t where they usually were.
peer-reviewed study was recently published online in “Marine Policy,” a
science journal that focuses on ocean policy studies, and is due to be
published in the paper version of the journal in April.
researchers have long known much about the effects of seismic activity
on whales and dolphins and other marine mammals, this was, according to
Paxton, a student in Pete Peterson’s lab at UNC-IMS, the first study to
document how multiple species of fish respond to seismic surveys in
their natural environment.
Paxton noted that more research is
needed before conclusions should be drawn about how long the fish
stayed away, or where they went. The researchers surmise they went to a
nearby, quieter reef, but the study shows that, “we need to consider
fish when we think about seismic surveys. We can’t ignore it.”
research was funded by the Bureau of Ocean Energy Management, the
federal agency that permits seismic surveys for oil and gas deposits,
as well as drilling. Colleagues involved in the project included
Peterson of UNC-IMS, Chris Taylor of the National Oceanic and
Atmospheric Administration’s National Ocean Service, Julian Dale of the
Duke University Marine Laboratory, Elijah Cole of the Duke University
Pratt School of Engineering, Christine Voss of UNC-IMS and Doug Nowacek
of the Duke lab. Nowacek is one world’s leading experts on marine
mammals, and has been outspoken in expressing concern about the
potential effects of seismic surveys on the feeding, mating and
migration of whales, including the endangered right whale.
and the others conducted their study at a natural rock reef and popular
fishing spot – the “210 rock” – about 30 miles offshore from Beaufort
Inlet, at a depth of 100 feet.
They had learned, shortly
beforehand, that the National Science Foundation’s mapping effort was
going to be in the area, and managed to get microphones and video
cameras posted to monitor the reef and the fish populations. The
academic objective of the seismic survey was to study the formation and
evolution of the Eastern North American Margin, and involved use of an
airgun array of similar volume to those used during oil and gas
exploration. Most of the survey occurred in deep waters off the
continental shelf, although it continued across the continental shelf
and into shallow shelf waters of northeastern Onslow Bay. The area,
according to the paper, supports hard-bottom reefs that sustain an
abundance of fish, including tropical, subtropical, and warm-temperate
“It was a rare opportunity, and we’re grateful to get
the opportunity and grateful that BOEM provided funds,” Paxton said.
During the whole marine mammal-driven seismic survey debate – President
Obama finally banned it off the Atlantic Coast right before he left
office in mid-January – “I had wondered what was happening to the
fish,” she added.
It’s a particularly important question at
reefs, because they are crucial to some species of fish, many of which
are valuable to commercial and recreational fisheries. The fish eat
there, reproduce there and seek shelter from potential predators
one-time event like the mapping survey likely just moved the fish away
temporarily, Paxton noted, but she wonders for how long, and she, like
other marine scientists, such as Nowacek, is concerned about the
cumulative effects on things that live in the water when oil and gas
surveys take place for days, almost continuously, sometimes by multiple
At one point, eight seismic survey firms had applied
for permits to search for oil and gas off North Carolina. They fire
their multiple airguns as often as every 10 to 12 seconds, sometimes
more than 7,000 blasts in 24 hours. Experts say the sounds can carry
for hundreds or thousands of miles.
Research shows that the blasts’ intensity exceeded 170 decibels, so loud it overloaded the microphones.
seismic sound levels are compared to jet engine noise, but Paxton said
the comparison isn’t fair, because sound is different in water than in
air. She said an exploding grenade may be a more accurate comparison. A
jet engine at 75-80 feet away can be about 140 decibels. Sounds louder
than 85 decibels can cause permeant hearing loss in humans. The Natural
Resources Defense Council says, “a substantial and growing body of
research now indicates that ocean noise pollution negatively affects at
least 55 marine species, including several endangered species of whales
and 20 commercially valuable species of fish.”
Reefs are normally quiet, with just the sounds of shrimp “crackling” and other marine species eating.
Seismic Industry Disputes Study
Adams-Jackson, vice president for communications for the International
Association of Geophysical Contractors, called the study incomplete and
limited, noting it was one day at one site.
“Second, the effect
is no different from what has been reported elsewhere where fisheries
and seismic have coexisted for decades: the Gulf of Mexico, the North
Sea, West Africa and throughout the world,” she said. “Marine seismic
surveys have been conducted since the 1950s and experience shows that
fisheries and seismic activities can and do coexist. There has been no
observation of direct physical injury or death to free-ranging fish
caused by seismic survey activity, and there is no conclusive evidence
showing long-term or permanent displacement of fish.”
Further, she said, the seismic industry works with local fishing organizations to coordinate activities.
Adams-Jackson said, the seismic industry “takes these concerns
seriously, even if the substance behind them is of variable quality.
While no harmful effects on ecosystems or fisheries have been found
from seismic surveys, we continue to encourage and support additional
study and monitoring.”
The seismic industry, along with oil and gas companies, are supporting more than $1 million worth of research on the topic.
Regulators Support Research
Gillette, a spokesperson for BOEM, said the agency funded the study
because “BOEM is very interested in research on sound as it relates to
fish and marine mammals. Since 1998, BOEM has invested more than $50
million on protected species and sound-related research, including fish
and marine mammals,” she added.
BOEM is a leading contributor to
the growing body of scientific knowledge about the nation’s marine and
coastal environment. The bureau regularly relies on the expertise of
universities and other science organizations.
“This study is a
snapshot in time but didn’t follow up on what was happening on the reef
after the surveys were taken. We’re funding an additional study with
NOAA to learn more about the effects of sound on fish and fish
Gillette said there had been few studies conducted in the open ocean focused on how fish respond to human-produced sound.
has funded laboratory-based experiments to address the consequences of
sound exposure to fish, but these experiments have limitations as to
how they represent what happens in the real world,” Gillette said. “As
with any scientific investigation, these field-based observations add
to our understanding of how fish may respond to sound, but like many
scientific efforts, more questions are often raised than answered.
We’re funding an additional study with NOAA to learn more about the
effects of sound on fish and fish populations.”
That study is
looking closely at black sea bass, which according to BOEM, “show
affinity” for certain habitats within oil- and gas-lease areas. In
addition, black sea bass produce sounds, such as grunts and thumps,
which have been associated with feeding and escape.
and recreational fishermen have expressed concern that noise produced
during sub-bottom surveys, pile-driving, and operation of renewable
energy facilities may have a negative effect on the behavior of black
sea bass ranging from catchability to long-term sub-lethal behavioral
impacts. This species is known to utilize mid-frequency acoustics to
communicate during spawning and feeding but their sensitivities to
anthropogenic sounds, and their behavioral responses to them is not
study summary also notes that black sea bass could be vulnerable to
sounds generated by offshore wind development, because the fish are
known to use acoustic communication and because their habitats overlap
within renewable energy lease areas.
acknowledged the validity of some of the criticism, and she expected
it. She and her colleagues would love to participate in follow-up
studies, but Paxton stands by the conclusion that the results generated
by their work show in clear terms that concerns about effects of
seismic surveys on fish are warranted.
“Although working with
limited data, this study provides evidence that during exposure to
seismic noise, the prevailing pattern of heavy fish use of reefs during
the evening was suppressed,” according to the report. The finding is
notable because it goes well beyond detection of a startle response
from individual fish, instead suggesting a multi-species response to
The Magnuson-Stevens Fishery Conservation and
Management Act of 2007, the nation’s main fisheries-protection law,
“mandates protection of reefs, including those studied here, as
Essential Fish Habitat,” the paper adds. “Reducing opportunities for
fish to aggregate causes concern as this could reduce options for
foraging, mating, or other important life history functions. Though
there are no observations to indicate the duration of the observed
effect, these research results augment and confirm issues raised by
marine mammal experts and suggest that concerns associated with marine
seismic surveys appear to be realistic and well-founded.”
Reef before seismic surveying
Video: UNC Institute of Marine Sciences
Reef during seismic surveying
Video: UNC Institute of Marine Sciences