Fish of many different shapes and sizes use reefs for their home. Because warm and cold water mix off the coast of NC, both warm- and cold-water associated species call NC reefs their home. Credit: J. McCord/ UNC-CSI
Fish are being pushed from their homes by seismic testing, a surveying method that uses dynamite, a specialized air gun or a seismic vibrator to develop images of the rock layers below the ground.
Avery Paxton, a marine ecologist Ph.D. student from the University of North Carolina, recently studied the impact seismic testing has on fish who inhabit a reef 30 miles off the coast of North Carolina and found that during seismic surveying, reef-fish abundance declined by 78%.
“What was really interesting is that this decrease occurred during the evening hours, when before the survey the fish were most active on the reef,” Paxton said in an exclusive interview with R&D Magazine. “We don’t know exactly where they went, we assume that they moved from the noisy reef to a nearby quieter reef or perhaps some of the smaller fish went and hid in the holes or crevices.”
Paxton said to conduct the study the research team placed underwater cameras and microphones at the reef and observed the data three days before the test and also during the seismic test.
However, due to a battery issue the study does not include any data after the survey.
Paxton said the majority of research on the impacts of seismic testing centers around marine mammals and not fish.
“Typically when we think of seismic surveying we think of the impacts to marine mammals like dolphins and whales,” she said. “But I’m a reef biologist, so I always wondered what about the fish hearing these loud noises.
“We looked at the literature and there hasn’t been a comprehensive study of what fish on reefs did when they were exposed to these noises,” she added.
While there is no evidence that any fish died from the noise, Paxton said in lab experiments the fish exhibited damage that had an impact on their ability to find food or reproduce.
Paxton posted a pair of videos on her personal website, one showing a plethora of fish at the reef and another that shows basically no fish present during the seismic testing.
According to Paxton, this particular seismic test is unusual because it was done in relatively shallow water, just 100 feet deep.
“Typically seismic surveying is done in deep water, so this was a relatively rare occurrence,” Paxton said.
Paxton said this particular seismic survey was done for geological research, while the majority of the surveys are to seek gas and oil.
However, she said the air gun used for the survey is similar to the one used for oil and gas discovery, and she compared the noise emitted to a planned explosion.
Paxton said she hopes the data can be used to drive marine policy and permitting decisions.
She also said there will be further studies on the impact of seismic testing.
“We’d like to follow up on this research by even doing another seismic survey to figure out more information about where the fish went, what they did when they went away, how long it took for them to come back,” Paxton said.
The study was published in Marine Policy.
