Combined Results of 34 Published Tracking Studies

Smallmouths everywhere tend to spawn within a window of water temperatures ranging from slightly below 60°F to about 64°F . Every year, in every riverine habitat studied with tag returns or radio telemetry, smallmouths seem to start moving out of wintering habitat when water temperatures approach 50°F , and they soon appear near spawning habitat. By the time the water reaches 60°F, every smallmouth that is going to spawn is on or near spawning habitat. But some studies have also shown that not every mature smallmouth spawns every year, which perhaps explains why one smallmouth in the study by Lyons and Kanehl didn’t migrate at all in spring or summer.

How far do smallmouths migrate in spring in the rivers and creeks you fish? It isn’t possible to answer that question based on latitude, climate, or by what the bass do in other rivers nearby. Each stream environment seems to invest within its smallmouth populations a genetic propensity to follow the unique drumbeat of that system’s characteristics. Apparently, smallmouths will seek near-perfect habitat for each season, regardless of the distances involved.

Summer Habitat

Once smallmouths migrate to summer habitat, conventional wisdom indicates they stay put unless floods or severe drought force them to move. This has been the assumption of most avid bass anglers, and most biologists, for many years, the theory buoyed by several early studies.

“Nearly all published studies on summer (defined here as postspawn, from mid-June through mid-August) movements have been based on recaptures of marked fish and have concluded that smallmouth bass stay within a relatively small area of a stream or river, often a single pool, unless environmental conditions become extreme,” Lyons and Kanehl wrote. “For example, in Jordan Creek (central Illinois), Larimore (1952) found that most tagged smallmouth bass had home pools that they rarely left during the summer, and that they occupied the same pools in successive years. During severe drought, smallmouth bass moved over a mile downstream as their habitat dried up, but returned when the drought ended.”

Studies in Indiana (Gerking, 1953, 1959) discovered much the same thing. Smallmouths in those streams remained within reaches less than 365 yards long, and tagged fish were found in the same pools for several years in a row during summer. On the Snake River along the Idaho-Washington border, Munther (1970) reported that “most recaptured individuals came from the same pool where they were tagged, and 95 percent were recaptured within .75 miles of their release point.”

Smallmouths of the Jacks Fork in Missouri, however, ranged up to about 3 miles. Studies on the Des Moines in Iowa revealed that some smallmouths moved as much as 2 miles in summer, while most bass with tags moved no more than a quarter mile. In the Deerfield River in western Massachusetts, radio-tagged bass had home ranges that varied from 70 yards to over a mile.

“In our radio telemetry study,” continued Lyons and Kanehl, “five adult smallmouth bass were tracked during the summer of 1993; four in Otter Creek and one in the Pecatonica River. All of these fish stayed within a small area, never moving more than 200 yards upstream or downstream. In late June, an extended flood created flows more than two times normal, but no substantial movement occurred during this event. By mid-August, however, smallmouth bass began to leave Otter Creek on their migration to winter habitats.”

Since smallmouths tend to use the same seasonal habitats year after year, it must be assumed that their chosen summer habitat has the potential to provide a stable source of protein every year, with lots of rearing habitat for minnows, crayfish, aquatic insects, and a steady supply of plankton, since the metabolic requirements of smallmouths are greatest in summer. These areas tend to have structural diversity with inflows from lakes, tributary streams, or springs. The classic “riffle-pool” habitat of summer smallmouths provides oxygen through the mixing action of water running over shallow rock. The rocks and subsequent eddies provide plenty of habitat for crayfish and minnows, and the deeper pools gouged out downstream of the riffles provide prime areas for smallmouths to rest or hide.