Interesting Observations of Smallmouth Bass Aging

Max Wolter, DNR Fish Biologist shared the following research in a recent issue of Wisconsin Outdoor News. “During the last several years, the Hayward DNR fish team has worked on a Couderay River smallmouth bass tagging project, partially funded by the Wisconsin Smallmouth Bass Alliance. Based on its size, the Couderay provided an excellent opportunity to study a river smallmouth population.

We will unpack different aspects of this study over time, but this week, the focus is on the ages of smallmouth in the Couderay. 

We took dorsal spines, the pokey ones on the back of the fish, from the representative number of smallmouths across the spectrum of sizes that we handled, which ranged from 8 to 20.7 inches. If you have the right equipment and training, you can age those spines just like the rings on a tree. 

We found that it takes about 5 years for a Couderay River smallmouth to reach 14 inches. Smallmouth 3 to 5 years old were the most common fish in the river. Indeed, older smallmouth bass were much less common, as would be expected. Smallmouths older than 8 years were rare, and the oldest smallmouth we aged in the project was 10 years of age. 

In summer of 2022, we captured a 20.7-inch smallmouth. It was almost a full inch longer than any smallmouth previously caught in the study. I was confident this fish would also be the oldest fish we would see in the river. When we aged the fish this past winter, however, we found that it, too, was just 10 years old. 

This illustrates an important concept within fish management. Fish, as with most organisms, have considerable variation among individuals. Even smallmouths hatched in the same year and experiencing mostly the same conditions can wind up being fairly different in size. For example, another 10-year-old smallmouth we handled was more than 2 inches smaller than our 20.7-inch fish. 

Understanding the ages of fish is useful for managers but might also help anglers appreciate that a true trophy fish is a special organism and often a decade or more in the making.”