A three-year study of walleye and sauger in the Missouri River downstream of Fort Benton has concluded that walleye may be competing with sauger for food and living space.

“The study provides substantial evidence that sauger and walleye live in the same areas and eat mostly the same foods in the river,” says Brian Bellgraph, a graduate student at Montana State University who conducted the study as part of his master’s thesis in fisheries. PPL Montana funded the study, and Fish Wildlife and Parks cooperated with the fieldwork.

To be absolutely sure these fish compete requires proof they share resources. That’s difficult to prove, but in this case, the evidence is strong.

 That non-native walleye may be competing with native sauger for food and habitat is important because sauger populations are declining in the Missouri, while walleye numbers are not.

“Sauger are listed as ‘species of special concern’ in Montana due to limited habitat and population declines,” Bellgraph says.

Starting in fall 2003, Bellgraph fitted 26 sauger and 24 walleye with radio transmitters. The fish were captured in a 30-mile stretch of the Missouri between Fort Benton and Coal Banks.

“Tracking showed that both sauger and walleye migrated 80 to 100 miles downriver during the fall and winter,” Bellgraph says, “to areas where they spawned in March and April.”

 By late spring, all of the sauger returned to their original summer river reach. Only about half the walleye returned to their original reach.

Bellgraph also discovered:

Steve Leathe, regional fisheries manager for FWP, says: “This study is a great example of how research is used to guide our fisheries management program.”

The study, Leathe added, confirmed the importance of the current sauger-walleye daily fishing limit of five fish, to include only one sauger, between Great Falls and Fort Peck Reservoir.

“This was probably a good idea because it shifted angler harvest towards walleye, which may well compete with sauger,” Leathe says. “And we now know for sure that sauger routinely use almost the entire river for their annual life cycle.”

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