Combined Results of 34 Published Tracking Studies

The Susceptibility Of River Bass

Anglers have a dramatic impact on smallmouth bass populations in streams. Studies on the Maquoketa River in Iowa from 1994 to 1995 indicated that every smallmouth over 6 inches long was caught an average of 6.3 times during that period. “Some of the bass were caught 9 or 10 times,” biologists told us. If not for special no-kill regulations, smallmouths over 10 inches could have ceased to exist in the Maquoketa for years, which would devastate year classes and send the population into a downward spiral, which is difficult to recover from.

Stream smallmouths can be aggressive, and biologists have often noted that anglers can easily develop misconceptions about the size of the population. Life can be harsh in streams and rivers. Floods, droughts, and exceptionally cold winters can literally kill fish and dramatically affect populations of prey species and the strength of year classes for smallmouth bass.

Some observations and conclusions by Lyons and Kanehl: “Smallmouth bass fry are susceptible to displacement from high flows and may be carried many miles downstream by floods (Larimore and Duever, 1968; Simonson and Swenson 1990). Evidence suggests that survival of fry displaced long distances by floods is low; downstream drift of smallmouth fry during nonflood years appears to be uncommon at best.”

Regarding establishment of special-regulation areas:

“If special fishing regulation areas for smallmouth bass are to be established in streams, then these areas should include the potentially large annual home range of smallmouth bass. Although it may seem impractical to cover an entire home range with special regulations, the regulation area should be as large as possible. Ideally, the regulation area should include locations where smallmouth bass are most vulnerable to anglers during fall and spring migrations.” They went on to cite the Zumbro River in Minnesota, where 40 percent of the smallmouths tagged within a special-regulation area were later caught by anglers outside the area.

Regarding stocking practices:

“Stocking does not appear to be useful for enhancing smallmouth bass populations in streams. Transplanted smallmouth bass tend to leave the stocking area rapidly and often leave the stream itself, typically moving downstream. If stocking were to be done, it would be best to use wild-caught fish from the same drainage system. At least some smallmouth bass populations undertake long and specific migrations, and the tendency to make these migrations may be controlled genetically. If there is a genetic component to smallmouuth bass movements, then it will be important not to mix populations and risk losing adaptive migratory behaviors through introgression.”

Regarding dams, culverts and crossings:

“Long-distance movements are an important component of the life history of smallmouth bass populations in some systems. Therefore, dams and other structures that prevent or impede movement will (negatively) affect these populations. On smaller tributaries, road crossings, and culverts should be designed to allow passage by adult smallmouth bass so that spawning areas are not cut off. Effective upstream and downstream passage for adult smallmouth bass should also be pursued at dam sites.”

As we increasingly impact and alter the course of our rivers, let’s hope that common sense prevails and consideration is given to the needs of smallmouths and other wildlife that depend on flowing water, so that all studies we’ve funded come to some meaningful end—so that our grandchildren will still be able to catch smallmouth bass in the rivers they inherit from us.