Lake Oahe is a popular spot for anglers to try their luck catching walleye, bass, pike, and many other sport fish.
However, Oahe holds another secret: salmon.
On a windy evening on Lake Oahe, John Murphy, who supervises conservation officers for the South Dakota Game, Fish and Parks Department, attached a gray 10-pound weight to fishing line. The ball pulled a lure down about 80 feet where salmon feed on smaller fish.
“So, what I’ll do, I’m going to put this on the line, and I’ll attach this to that ball, and it’ll pull it down so when a fish hits it, it actually comes away from the ball.”
John held up a shiny, flat sheet of metal that reflected the sun. A lure trailed behind it.
“So, these are what they call flashers, so this is what it’s supposed to look like going through the water,” John said. “So, this is supposed to simulate a school of smelt and this is like a sick one at the end and that’s why they go for the last one.”
“They’ll spin in the water,” John’s wife Leslie added.
Leslie formerly worked for the Department of Game, Fish and Parks and currently is an environmental scientist for a private company. They love salmon-fishing and have developed a few tricks of the trade. John reached into a cooler to bring out a container filled with an odorous mixture of tuna and garlic to cover the lures. The intention is to entice salmon with the strong smell.
Each year, the Department of Game, Fish and Parks stocks salmon in the Missouri Reservoir, drawing anglers from around the Midwest.
Salmon biologist Robert Hanten, who works for the state, said salmon fishing brings in $1.7 million in local and state revenue annually.
“When chinook salmon were first introduced, found in the reservoir, anglers immediately took notice, were super interested. It created what was called almost like a salmon mania,” Hanten said.
During an experimental period in 1970, North Dakota stocked salmon in Lake Sakakawea. A few juvenile salmon wiggled their way down stream to Lake Oahe. South Dakota fishery managers understood the unique possibilities of introducing chinook salmon into the Oahe reservoir. Hanten's father started the salmon program in South Dakota in the 1980s.
“It’s not a normal, natural environment,” Hanten said. “This is a man-made system with these large Missouri River reservoirs and chinook salmon happened to fit that mold pretty well, even though it’s basically salmon out on the prairie.”
In their native habitats, chinook salmon spawn in fresh water and then make their way out to the ocean. After four to five years, they return to their spawning spot to breed and die. Research surrounding the fish’s ecology has centered around reproduction because the Oahe chinook salmon cannot reproduce sustainably in the lake.
“In the actual hatching process back at the hatcheries, different life stages occur with those eggs in development that instead of that actually hatching out and becoming a little fish, you actually have high rates of loss or mortality where those eggs just don’t survive to become fish,” Hanten said.
New research will track how well young salmon do in South Dakota’s Missouri reservoirs.
Game, Fish and Parks biologist Dylan Gravenhof is conducting research surrounding the behavior and survival of juvenile salmon after they are stocked in Lake Oahe for his thesis project. Gravenhof and his team are tracking 50 salmon this summer and 50 more the following summer.
“We purchased these special little transmitters that we can surgically implant inside the fish, stitch the fish back up, [and] we return them to their tanks at the hatchery,” Gravenhof said. “Eventually, when those fish get released into the water, we can track and see where they go and if they survive.”
They use passive and active trackers to record the location of each fish. When a fish swims by a passive tracker, a signal is recorded to pinpoint where that individual fish is and that it is still alive. The tracking devices have a special polymer coating that will dissolve if the salmon is eaten by a predator.
Gravenhof says so far, the research shows a 25 percent mortality loss.
Melissa Wuellner is an associate professor at the University of Nebraska-Kearney and works with Gravenhof on the project. She said the data will allow them to determine better ways to stock the lake.
“It takes a lot of time, and manpower and really money to raise fish to be stocked out and you want to kind of maximize that return on that investment. And so, we can look at improving success of stocking in so many different ways.”
Gravenhof foresees applying the data to surrounding areas as well.
“I think it definitely will be some good information for other states. North Dakota has a similar salmon program to us. Montana has a similar program so it could definitely be very useful information for them because they have similar systems and fisheries as us.”
Gravenhof hopes his research can help existing salmon programs in the Midwest become more sustainable.
The Murphys have been salmon fishing together for over a decade; John started fishing for salmon with his father from a young age.
Leslie grew up hunting and fishing for walleye in rural Minnesota, so she is not a stranger to fishing. However, she became hooked after the first time she caught a salmon.
“It’s a fun fish to catch if you can catch one,” Leslie said. “It’s a lot of time, it’s time-consuming. There’s a lot of effort that goes into salmon fishing, but once you get one of those big salmon on the line, it’s a fun fish to catch. They put up a good fight.”
Leslie and John Murphy are on a streak this summer. They’ve caught a salmon every time they’ve gone fishing on Lake Oahe.