Combined Results of 34 Published Tracking Studies

Coalesce is a wonderful word. It describes a process wherein disparate parts, people, meanings—even fish—come together to form one whole, or concentrate in one area. To “become one” with something is to coalesce with it.

That’s why what John Lyons and Paul Kanehl of the Wisconsin Department of Natural Resources have done for fishermen is a wonderful thing. They performed a radio-telemetry study, tracking smallmouth bass in two Wisconsin Rivers. And, in the process, they compared information from 34 published studies on the movements of smallmouth bass in rivers, eight of which involved radio telemetry. The result, Seasonal Movements of Smallmouth Bass in Streams (AFSS, 2002, by John Lyons and Paul Kanehl, Wisconsin DNR), is a must read for river smallmouth fishermen.

“Lotic (river-dwelling) populations of smallmouth bass have been the subject of scientific studies for more than 100 years,” Lyons and Kanehl wrote. Those radio tracking and tagging studies provide a wealth of information revealing not only how dynamic stream smallmouths can be compared to their lake-bound cousins, but also how vulnerable and fragile these populations are. “Despite a long history of research, however, much remains to be learned about smallmouth bass movement patterns and habitat use, particularly from fall through spring.”

Fall Movements

Lyons and Kanehl performed their radio-telemetry study on Otter Creek and the Pecatonica River in southwest Wisconsin from 1992 to 1993. But research includes findings on the seasonal movements of smallmouth bass in rivers of 14 states and Ontario, and the paper reviews and summarizes smallmouth studies by biologists around the continent. From Alabama, Tennessee, and Massachusetts to Oregon, Ontario, and Michigan, these studies blanket the range of smallmouth bass and cover a variety of climates and types of riverine habitats.

They found that latitude and climate have a lot to do with smallmouth behavior in rivers over the course of the seasons. “In fall,” they wrote, “some smallmouth bass populations remain sedentary, while others migrate more than 45 miles to reach winter habitat. Migration distance is correlated with winter severity; smallmouth bass move little in streams that do not freeze, but often move more than 3 miles in systems with ice.

“Winter habitat and activity levels vary among populations and have little obvious relation to winter severity, however. In some systems, smallmouth bass occupy the deepest available water or areas of cover (boulders, logs) where they remain inactive for the winter. In other systems however, smallmouth bass avoid the deepest holes and are often active in areas with little cover all winter.”

For anglers, this rings true. Smallmouths near the northernmost part of their range, in Lake Superior, are easily caught through the ice most days in winter. Yet, 100 miles south, on the Mississippi River, smallmouths become almost impossible to catch after the water drops below 40°F in late fall—let alone during midwinter, through the ice. Near the warming influence of hot-water discharge sites in the same region, on the same river, however, numbers of smallmouths can be caught in open water all winter.

Tagging studies on the Mississippi by the Minnesota DNR reveal that smallmouths tend to migrate to deep wintering holes—usually to plunge pools below dams, reservoirs above dams, or to confluence holes at least 20 feet deep. These migrations were shown to cover 20 miles or more in some cases.

But winter “sanctuaries” differ from river to river, depending not only on latitude, but also where smallmouths find the greatest environmental stability. “In one segment of the Jacks Fork (Missouri), many smallmouths left the main stem when waters cooled below 59°F in fall and entered a tributary spring with constant winter temperatures of about 56°F,” according to Lyons and Kanehl. “They remained there until main-stem temperatures increased above 59°F the following year. The distances smallmouths traveled to reach the spring run were unknown.”