 Radio Script 2001
Trawling for Answers
STORY: In the wheelhouse of the research vessel Big Valley, skipper Gary Edwards does his best to keep pace with the fishing trawler Vaerdal. One hundred feet below, on the ocean floor, the Vaerdal’s net is busy scooping up fish. EDWARDS: "We’re getting a good picture now, the transponder is going. So far so good." Edwards needs to stay close to the Vaerdal so that the transponder on the fishing net can relay the net’s exact position on the seafloor. But it’s not easy. Despite the drag on the 132-foot bottom trawler, Vaerdal skipper Gene Anderson is pulling away. ANDERSON: "I’m going a bit fast here because we’re going with the current." Hours later, researchers deploy a camera-equipped remotely operated vehicle, or ROV, to see what sort of damage the trawl net may have caused to the seafloor. In the ROV’s control shack, a trailer chained to the deck of the Big Valley, graduate student Eloise Brown watches the television monitor. BROWN: "We’re going perpendicular to all the trawl tracks right now. We’re not going down the center of it. There’s one, there’s a furrow! And so, you have the doors, which are these big metal objects that keep the net spread wide. So if we’re crossing the trawl track perpendicular, we’ll probably come across a furrow. That may have been a door furrow. And that should leave a track, because they are really heavy, really large." Observations such as these, along with a host of scientific data about the structure of the seabed and the tiny marine life that live on the ocean bottom, are all part of a study aimed at answering a question on many people’s minds these days: Is dragging a net across the ocean floor harmful? Sue Hills is a leader of the study and a marine science professor at the University of Alaska Fairbanks. HILLS: "There’s been a lot of interest in the last few years about the effects of fishing. Ten years ago people said the effects of fishing meant taking out large numbers of fish. Then people started looking at the effects of the fishing gear—what does the gear actually do? We’re just trying to test one hypothesis: What difference does it make to do commercial flatfish trawling in flatfish habitat? Researchers are concentrating on a one-square-mile chunk of ocean floor near the Round Island State Walrus Sanctuary in Alaska's Bristol Bay. The area is ideal because no one has fished within 12 miles of the sanctuary since 1992. By studying the area before fishing takes place, scientists can measure the impacts after fishing. Helping with the study are fishermen themselves. The Groundfish Forum, a trawler trade association, volunteered the trawler Vaerdal and provided Brown with a research scholarship. Some $250,000 in additional funding comes from the North Pacific Marine Research Program, set up by Congress to unravel the causes of Bering Sea fish, mammal and seabird declines. For a week prior to the Vaerdal's arrival, Brown used scuba divers and underwater cameras to document virtually every detail of the seafloor. They measured the size of the grains of sand and mud and the amount of chlorophyll being produced by algae, seaweed and other plants. They also used a device called an echosounder to measure the density of the seafloor. If trawling compacts or stirs up the bottom, it could alter the makeup of invertebrates that live there, and that could alter the mix of fish in the area. Finally, researchers used a small dredge-like device called a VanVeen grab to snatch a chunk of the seafloor in order to learn what sort of creatures live there. Science diver Cathy Hegwer. HEGWER: "What we’re doing is taking a VanVeen grab—it just takes a scoop out of the bottom of the seafloor. You rinse off the sediments and you’re left with the macro invertebrates. We then go through to identify the species to see if there are any difference in the fauna from a trawled area and the fauna from an untrawled area. They’d be the first to show if there had been any disturbance to the sediment because that’s where they live. What we’ve got here is a sample from a recently trawled area. We have some sand dollars, some gastropods, and some bivalves." Months later, in her lab at the University of Alaska Fairbanks, Eloise Brown and a small army of technicians have viewed hours of videotape and processed hundreds of samples. While obvious changes were hard to pinpoint, Brown says trawling did alter the seafloor in subtle ways. One indication of change is that chlorophyll—needed for photosynthesis—was redistributed in the wake of trawling. BROWN: "Whereas there was no net change in the amount of chlorophyll throughout this two-kilometer patch, each station responded differently. Some stations increased in chlorophyll and some stations decreased in chlorophyll. And that’s what you would expect. In trawling you have a big net come by on the bottom, re-suspends sediments. Some of the stations had chlorophyll removed while others had chlorophyll deposited. I thought that was an interesting result. Obviously there was some disturbance and variability is an indication of disturbance." Sue Hills says people shouldn’t be surprised that damage wasn’t especially obvious, considering the area they studied is flat, featureless sand prone to severe winter storms that routinely mix up the sediments anyway. But that doesn’t let bottom trawlers off the hook. While trawling might have minimal impacts on sandy bottoms, it might very well have real impacts on areas dominated by corals and rocky bottoms. Brown says it's important to know how trawling impacts all of the habitats where fishermen catch fish. OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.
Audio version and related Web sites (sidebar at top right) Thanks to the following individuals for help preparing this script: Eloise Brown Dr. Sue Hills Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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