Lake Superior, the world’s largest freshwater lake, is experiencing a decline in one of its most highly prized fish stocks – the coaster brook trout. Researchers aren’t sure about the cause for the decline: it could be from shoreline activities, changes to tributaries, competition from other species, or decades of overfishing. What they do know is that coasters are no longer found in many locations on the American side of Lake Superior and the numbers are down in Ontario waters.

A team of scientists and biologists from both sides of the border is using everything from implanted radio tags to computer modelling to find out how to reverse the decline. The project partners include Rob Mackereth, a research scientist with the Ministry of Natural Resources (MNR) in Thunder Bay; MNR biologist Rob Swainson, Nipigon; MNR biologist Ken Cullis, Thunder Bay; and Lee Newman, a biologist with the U.S. Fish and Wildlife Service.

The Lake Superior brook trout is already on the road to recovery in the Nipigon area. Improvements to habitat, new fishing regulations and a long-term water management plan for the Nipigon River are all helping. In addition, the Great Lakes Fishery Commission has produced a plan that focuses on the biology of the coaster, helping researchers understand why it’s in decline and where to best direct their efforts to bring it back.

Coasters appear to be a unique brook trout stock that researchers think may be genetically distinct and thousands of years old. They live along the coast, hence their name, and have always been a valuable sport fish species in Lake Superior.

“The ecologically interesting thing about the fish is the way they use the lake and tributary streams,” says Rob Mackereth. “They swim around out in the lake for most of the year, then some come back up into these small tributary streams and rivers to spawn. The young stay in those streams for at least a year before heading down to the lake.”

What’s also striking about the coaster is its silvery colour. They resemble salmon, until they revert to ordinary brook trout coloration during spawning. They can weigh more than twice as much as ordinary brook trout. In fact, the world record brook trout, weighing in at 6.6 kilograms, was caught in 1915 in the Nipigon River.

The research team is trying to figure out exactly what living conditions coasters need to survive. “Once we understand what’s affecting them out in the lake, and what they need in the tributary streams, we can better predict where the re-introduction of brook trout would most likely be successful,” says Rob Swainson.

Thirty years ago, resource managers restored depleted fish populations by capturing adults, extracting and fertilizing eggs, raising the young in a hatchery and dumping them back into the same water body. Today, groups like this team are improving chances of success through better knowledge and new technology.

This spring, local anglers will assist the researchers by capturing about 30 adult coaster brook trout in Lake Superior. Those fish will be implanted with radio tags – small battery-powered signal-emitting devices about the size of an adult human’s thumb. With these transmitters, the coasters can be tracked all summer. Researchers will monitor the fish using Global Positioning System (GPS) technology.

“At least once a day we’ll enter the locations of each fish into the computer,” says Mackereth. “This will give us a record of where that fish was over a period of time. We’ll analyze that information to find out where the fish spends most of its time and its total range.”

The team will use an underwater video camera to survey the physical conditions of the areas the fish appear to prefer. “In the fall, we hope to follow the fish into the streams where they go to spawn,” says Mackereth. “With all this information in our computers, we’ll be able to analyze the geology and type of vegetation in the areas the fish use for spawning as well as the neighbouring near-shore landscape. In the end, we’ll have a better idea of where the coasters feel most at home year-round.”

Using this information, decisions can be made about the best place to re-introduce brook trout. But will they be the offspring of captured coaster brook trout, or just ordinary brook trout stock? Mackereth says genetic studies will show whether coasters really are a distinct stock, or just ordinary brook trout whose size, color and spawning habits have been altered by many years in Lake Superior’s cold, clean waters.

The research project is supported by funds from the sale of Ontario fishing licences, the federal government, the U.S. Fish and Wildlife Service, the University of Minnesota, Minnesota Sea Grant, Lakehead University, the Thunder Bay Fly Fishing Club, North Shore Steelhead Association and the Ontario Federation of Anglers and Hunters (OFAH). In addition, the project is among the first to receive funding from the Ontario Great Lakes Renewal Foundation, a non-profit environmental organization supporting ecosystem rehabilitation in the Great Lakes.