Underwater Cannon May Help Protect U.S. Great Lakes

Scientists struggling to protect fish native to the U.S. Great Lakes from a greedy predator called the round goby are taking a page from the playbook of stores that pipe classical music through loudspeakers to chase away loitering teens.

Gobies hang around prime spawning areas and gobble up eggs laid by trout, whitefish and other species important to the region's commercial and sport fishing industries. Biologists plan to strike back by firing loud underwater cannons near some of the gobies' favorite haunts, hoping to drive them off long enough for the eggs to survive.

It's part of the increasingly sophisticated war against invasive animals and plants that cost the nation's economy billions of dollars each year. Government agencies, universities and nonprofit groups are turning to high-tech weaponry to prevent new attacks and limit the effects of those under way.

Such work is particularly important in the Great Lakes, which are besieged by at least 185 aquatic invaders that have clogged water intake pipes, spread diseases and unraveled food chains.

"If we want to reduce chances for new invasions, we have to get beyond standard fishery methods such as netting and develop more effective control tools that can be used across a range of habitats," said Lindsay Chadderton, an invasive species specialist with the Nature Conservancy, one of the participants in the goby project.

The region's biggest new threat is Asian carp, which have infested the Mississippi River and its tributaries and are threatening to enter Lake Michigan through Chicago-area waterways. The federal government has budgeted more than $100 million to fight the fish, with some of the money funding development of new techniques that include light radiation and pheromones that could lure fish into traps.

Another potentially helpful instrument is the seismic water gun that government scientists are testing in Western lakes. Experts hope the system can create sound barriers that would repel bighead and silver carp.

It will also be tried next year against round gobies in Lake Michigan's Grand Traverse and Little Traverse bays.

The voracious bottom-feeders, measuring up to 10 inches long, have spread rapidly since arriving in European freighters' ballast water in the 1990s. They help the ecosystem by eating zebra and quagga mussels, which are among the Great Lakes' most damaging invaders. But their appetite for other fishes' eggs offsets the good they do. Gobies also spread botulism that has killed thousands of shorebirds.

The project will focus on a half-dozen rocky reefs where lake trout and whitefish spawn. Three of the reefs also are the only known spawning beds for a rare native species called the cisco, or lake herring.

"We know we can't get rid of gobies from the entire lake," said Randy Claramunt, a fisheries biologist with the Michigan Department of Natural Resources. "But if we can keep them from critical habitats at critical times, we think it can make a huge difference."

Since the 1960s, the oil and gas industry has used air and water guns that bounce energy pulses off the ocean floor to search for good places to drill.

Jackson Gross, a researcher with the U.S. Geological Survey's Northern Rocky Mountain Science Center in Bozeman, Montana, has pioneered the use of such devices against invasive fish.

The guns are mounted on boats that cruise along a lake surface as operators fire high-velocity jets of water toward the bottom. The action creates booms at frequencies audible to most fish, along with pressure waves powerful enough to make them extremely uncomfortable. Claramunt said he hopes the blasts will be lethal for at least some gobies, although Gross said his goal is to drive fish away, not kill them.

The key questions are how many shell-shocked gobies will flee, and for how long. Even a 50 percent reduction in goby numbers would be a success, Gross said.

Scientists plan to fire the guns in September, shortly before larger fish arrive to spawn. Their eggs incubate through the winter and start hatching in April, but are particularly vulnerable while drifting in the water column for about a month after being laid. After settling into the reefs' cracks and crevices, they're safer from predators.

"We're hoping the gobies don't move right back, but it's a possibility," said Matt Herbert, a Nature Conservancy aquatic ecologist. "Obviously if they return at the same density as before, it didn't work."

Gross said the water gun also might clear the reefs of rusty crayfish, another egg eater. If the trials succeed, the gun could be used against undesirable species in other places. One possibility: dislodging clumps of zebra and quagga mussels from hard surfaces, including water pipes and dams along the Colorado River.

"The one thing great about sound is, you put it out there and it goes away," Gross said. "It doesn't persist in the environment like a chemical."