I have no formal training on trout or any fish. I have been fishing for over a half of a century for Driftless brown trout. Sixty-two years to be exact. I caught my first monster at age five and have been chasing monsters since then.

I have turned many of my fishing friends on to their personal best browns. I take at least 20 assists on tips on where to go to score that mythical 20-incher.

I have felt my friends’ pain on at least five occasions when they lost browns in the 25 to 30-inch range. I have netted eight browns for friends over 26 inches, and one friend I have netted three over 30 inches for him and two more over 27 inches.

I destroyed my 36 years of logbooks about four years ago. I have caught so many big browns through the years that they run together. I thought that much information in the wrong hands could be detrimental to my trout population.

Most of the monsters were caught in bigger water. Most are below non-designated trout water in low-traffic areas. Most have springs in proximity.

I am not saying that all bigs come from big water, however. There are plenty of nightmares in streams that can be stepped across in most places. I no longer chase trout on the weekends due to spot stealers.

My knees are bad, and my trips have become shorter and less frequent. Just recently, I returned to the same hole where I caught an above-average female brown four years prior. I have been back twice a year since then. I like to dream about how big she could be. I get fired up as I approach her home. I am only disappointed for a short while after she does not hit. I typically wonder why she did not do the dance with me. Did she die of old age? Is she too smart now to hit again? These are the questions that keep me coming back. “Where did she go?”

I decided to consult some folks with the skills to answer my questions. I have been talking via emails to the most reputable trout expert in Wisconsin. He has won awards and has a doctorate in Fisheries Science. He works for the Wisconsin Department of Natural Resources. His name is Dr. Matt Mitro. He has done studies with other DNR professionals on browns and aging.

I asked my two favorite WDNR employees how long a Wisconsin driftless area brown lived. I told them I knew the info was an educated guess, and who better to make the educated guess? Below is the information I gleaned from Dr. Matt Mitro, Fisheries Research Scientist, and Kirk Olson, Fisheries Biologist. They talked on emails and collectively helped with the story.

Dr. Mitro’s input:

Dr. Mitro says, “Wisconsin small-stream trout can live to 9 to 10 years old, with the rare brown that can live another 1 to 3 years longer. The average is 4 to 6 years.”

The best example Matt has is of a brown trout caught/shocked repeatedly over several years. The brown trout he first caught and tagged with a color implant tag was in spring of 2011. They do not tag young-of-year trout, so this fish was a minimum of 1 year old. The second time he caught it, two years later in 2013, he gave it a second tag. He then caught that fish eight more times through 2018. The last time they caught it, it was 21.1 inches long, 3.7 pounds, and had to be a minimum of 8 years old. Matt would guess it probably was tagged as a 1-year-old in 2011 given that it was 10.4 inches in 2013. The tagged brown was shocked in a heavily fished stream.

Matt’s data collection has documented these lengths and weights:

“The longest fish was a 22-inch male brown trout. I don’t have a weight for it. The heaviest was a 3.75-pound male brown trout that was 21 inches long.

“The largest female brown trout was 21.25 inches and weighed 3.3 pounds.

“If I had to guess on age, I’d say all these were in the 8- to 10-year-old range. I’ve seen much smaller fish in that age range, too (based on tag-recapture).

“Browns that get bigger have access to rivers to put the feed bag on.

Kirk Olson’s input:

Oldest age

“Matt’s done a lot more ageing than my crew, so I’ll defer to him. Age 10-12 feels about right for the max age of large browns in streams around here. Last time my crew aged trout was on a very small stream in Vernon County. Our oldest brown trout, based on otolith cross-sections, was approximately 6 years old, and only 11.2 inches. It wasn’t the largest fish in our sample; we caught several larger fish (up to 14.9 inches), but we aged them between 3 and 5. Otolith cross-section is a stone in brown’s head that is the best way to get ages.”

Average growth?

“My crew has been tagging and recapturing fish at our annually surveyed trend sites since 2021. In that time, we’ve recaptured 385 tagged brown trout that give us a decent picture of what growth looks like in those six streams.

“Growth rate is highly dependent on trout size. Growth is rapid in the early years of a trout’s life and, generally, growth declines as the fish reaches maturity and gets larger. For example, brown trout that we initially marked between 6 to 9 inches grew an average of 2.2 inches a year, while those 9 inches and larger grew an average of 1.0 inch a year.

“The two largest fish that we’ve marked were 16.5 and 17.2 inches at marking. The 16.5-incher grew to 16.7 in a year and the 17.2-incher grew to 17.7 in a year.

“Stream also plays a role; we see quite a bit of variation among the six streams where we tag fish. Growth can also vary quite a bit among individual fish of similar size in the same stream. For example, we’ve seen growth of 9-inch brown trout in Vernon County vary from 1.8 to 4.0 inches in a year.”

Fewer large browns?

“I haven’t seen a decline in larger brown trout based on our more recent data or my general observations from the past 7 years. Looking at our trend data from 2008 to 2024 on six streams, maximum lengths haven’t declined over time.”

Growth rates vary from stream to stream. There are many factors when it comes to growing an old trout. Old does not always equate to big. An overpopulated stream will grow some big browns. Both Matt and Kirk have shocked monsters from populated creeks that have high traffic. Overfishing can cause fewer fish and fewer big ones. Heredity has some impact. Colder water in streams slows down growth rates.

Brown trout can spawn repeatedly in consecutive years, but not all do. It is possible that an older trout may spawn one year and then not the next, for whatever reason.

In general, the larger the female trout, the more eggs it can produce. There is certainly variability among individuals, but as size goes up, egg production goes up.

Both Matt, Kirk and I agree that big brown trout are still out there and are not on a downward trend.

Thank you, Matt and Kirk, for helping me and for the fine work you do for our resources.