RIVERDALE - The first thoroughly monitored tests of the effect on fish exposed to bursts fired from powerful air guns began Sept. 10 on Lake Sakakawea. The purpose of the testing is to determine how, or if, seismic exploring for oil formations beneath Lake Sakakawea can be accomplished with little or no harm to the state's largest fishery.
Scientists and biologists watched closely as a seismic testing barge equipped with air guns repeatedly fired test shots near the marina at Lake Sakakawea State Park. Below were holding cages containing endangered pallid sturgeon, paddlefish and walleyes. The air guns fire a downward burst that results in pulses of sound penetrating into the earth at the bottom of the lake.
Fish are known to be sensitive to sound, but what isn't known is what level of sound may adversely affect fish and at what distances. Initial tests on Lake Sakakawea showed no immediate effects on fish that were positioned as little as 3 meters from the air guns.
Professor Tony Hawkins, Scotland, left, and John Young, Houston, are among those leading a study to determine the effect of seismic activity on fish in Lake Sakakawea. This photograph was taken at the Garrison Dam National Fish Hatchery.
"There was no mortality. My experience is that would be completely abnormal. It's not dynamite," said Jackson Gross, a leading expert in the field of sound technology who has initiated the use of sound to control unwanted fish movement, such as Asian carp in the Great Lakes and elsewhere.
Gross is employed by Smith-Root of Vancouver, Wash. He is in charge of science oversight for the Lake Sakakawea project. Total oversight is in the hands of John Young of Houston. Young is employed by Continental Shelf Associates, an environmental company based in Stuart, Fla.
"What you have here is mankind wanting to get access to mineral resources and you've got animals that need access to the water, so we are trying to share resources," said Young. "Seismic is a tool that is used by petroleum companies to see inside the earth. How much does the sound that the seismic companies use impact the animals? It could be physical impacts or behavioral impacts. In this study one of the first things we are looking at is the physical impact to these animals."
Young explained that the innovative testing being conducted on Lake Sakakawea should result in creation of a "dose response curve," a graph that will indicate statistically at what point fish might be harmed by seismic testing.
"If we know that distance, then we know how far away we have to stay," said Young. "For example, pallid sturgeon like to stay on the bottom. You need data from the deeper portion so you always have enough distance from the sound source to the animals, a safe distance."
Although it will be several months before all of the data from the testing will be fully analyzed and professional opinions printed, Young thinks the study will help design a way to mitigate the effect of seismic activity on fish - possibly through the use of high-quality sonar that would locate fish in the path of a seismic barge.
"Prior to taking a shot, if sonar indicates lots of fish, we'd just move somewhere else," explained Young. "We could come back later after the animals have moved."
Another option under consideration, if necessary, is using a sound source to move fish out of an area where seismic activity is taking place. It is all part of the factors under scrutiny in what Young calls the "complexity of the experiment."
Hess Corp. put together the team of scientists working at Lake Sakakawea as part of the preliminary work required in the permitting process to drill for oil. Several agencies are participating, including the U.S. Fish and Wildlife Service, North Dakota Game and Fish Department and U.S. Army Corps of Engineers.
The knowledge gained from the testing is expected to have worldwide application.
"That's right," said professor Tony Hawkins, Scotland. "Everyone has been concerned for years about the impact of these seismic surveys, but doing it on an ocean scale is really quite difficult. Doing it in the North Sea, for example, would be almost impossible. Here, you've got a good environment in which to do experiments and the local people have been very cooperative. This is ideal. This is a good place to start things off."
Hawkins is the former director of fisheries research for Scotland and the coordinator of fisheries research for the United Kingdom. He was involved in designing the Lake Sakakawea experiment and is also focused on mitigation.
"How can we avoid exposing the fish to the seismic in the first place?" said Hawkins. "The idea is to not expose fish unnecessarily, just to be on the safe side. This will be all new data for me, but fish are the same the world over."
Hawkins says what is learned at Lake Sakakawea be applied elsewhere, even in the North Sea where thousands of wind turbines are scheduled to be installed. To do so, extensive pile driving is needed. Pile driving, says Hawkins, creates extremely loud noise which travels easily through water.
"This is going to expose fish in the North Sea to very high levels of sound and we really want to know in advance what this is going to do to these fish," said Hawkins. "It is much more difficult to work in the sea. We can develop techniques here that can be applied in a more adverse environment. Of course, we have crabs, lobsters, prawns and animals that live on the seabed as well."
Of concern to recreational users of Lake Sakakawea is whether or not fish in the lake will be harmed by seismic activity and whether or not drilling will take place on the lake. The team of expert scientists, in cooperation with other governing agencies on Lake Sakakawea, should ensure minimal impact on the resources by seismic testing. Drilling on the lake is not considered likely. A number of horizontal wells already reach underneath Sakakawea, most about 2 miles in length. The technology exists to drill horizontally many times that distance.
A closer look
Necropsy work on fish exposed to seismic air guns began late this past week at the Garrison Dam National Fish Hatchery. Particular attention will be given to the inspection of air bladders and kidneys of exposed fish. Those organs should reveal if any harm to fish occurred due to seismic activity. It is believed any physical damage to fish would become evident within seven days of exposure to the seismic air guns.
"We want to know the real facts of where the harm is, if there is harm," said Young. "People who do the necropsies will have no idea of the treatment that animal got because we don't want any bias in the results. Hess has really done a good job of putting together an international team to do a study that's never been done with seismic before, so this is one-of-a-kind."
According to Young, the initial report on the findings from the Lake Sakakawea study are due to be presented to Hess Dec. 1. It will take an additional eight months for scientists to develop papers that will summarize the testing.
"It is exciting to get up every day and work with people who are so smart," remarked Young. "The young and the older ones are just brilliant. We'll find a way to bridge the gap between what mankind wants to do and what the animal world is. You can find a balance where you can do both. That's great. That's really good."