nature

Minnow Day

/ kchalling / Leave a comment

I have been wanting to learn more about minnow-sized fish ever since I started my goal of catching 100 fish species this year.

I should clarify that when I say “minnow-sized,” I am referring to small fish, typically 2-4 inches long, and not necessarily members of the Minnow family. Most species in the minnow family are indeed small, but there are notable exceptions, such as the Common Carp, which can grow to enormous sizes. I do not plan to count minnow-sized fish on my 100-species list, but I am nonetheless very interested in learning more about them.

My son-in-law, daughter, and my grandchildren joined me for an outing to the Zumbro River just south of Apache Mall in Rochester, Minnesota. My daughter, who has become an excellent watercolor painter, took a well-deserved break and spent her time under a shady tree painting a beautiful hummingbird. Meanwhile, the rest of us went hunting for minnows.

At first, my son-in-law and I tried using a seine net in the moderately fast-flowing current of the river. We caught exactly zero minnows with that method and eventually gave up. We then noticed that there were large numbers of minnows in the shallow, slow-moving rivulets along the edge of the river.

Fortunately, I had also brought a dip net. My son-in-law, who is quite a bit faster than I am, quickly began catching minnows and placing them in a bucket. We photographed each fish and then asked iNaturalist to help identify it.

Among the approximately 50 minnow-sized fish we caught were seven different species:

Johnny Darter
Bigmouth Shiner
Rainbow Darter
Central Stoneroller
Creek Chub
Northern Hog Sucker
White Sucker

The first four species remain minnow-sized throughout their lives. The last three were juvenile fish that will eventually grow much larger. Adult Creek Chubs typically reach 4-8 inches in length, White Suckers commonly grow to 12-18 inches, and Northern Hogsuckers often reach 10-18 inches.

One thing I learned while researching these fish is that minnow-sized species generally live much shorter lives than larger fish. Shiners, dace, darters, and killifish often live only two to four years, whereas larger species such as suckers, sunfish, bass, and catfish commonly live eight to twenty years or more.

There are several reasons for this difference. First, small fish experience intense predation pressure. They are preyed upon by bass, pike, walleye, herons, turtles, and even larger fish. Second, their high metabolic rates cause them to burn energy quickly and generally age faster. Third, many small species follow a “live fast, reproduce fast” strategy, spawning multiple times each year and producing large numbers of offspring. Finally, the shallow creeks, riffles, and stream margins where many small fish live are often unstable environments that can be affected by floods, droughts, heat waves, and winter freezing.

Fortunately for these species, their short lifespans are offset by rapid reproduction, allowing populations to rebound quickly after environmental setbacks.

We had a very enjoyable afternoon catching fish and learning more about a fascinating group of species that most anglers rarely pay much attention to. Although none of these fish will count toward my 100-species goal, they reminded me that some of the most interesting discoveries in nature come in very small packages.

Fishing the Minnesota River

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Yesterday, smoke from the wildfires in northern Minnesota and Canada drifted into southeastern Minnesota, producing some of the worst air quality Rochester has experienced this summer. The AirNow website showed an air quality index of 151 for Rochester—bright red on the map and categorized as “unhealthy.” Since the smoke appeared to be less severe farther west, I decided to spend the evening fishing around Mankato.

My target species were Silver Redhorse, Smallmouth or Bigmouth Buffalo, and Common Carp. I started at the Kiwanis Recreation Area on the Minnesota River just north of Mankato. Unfortunately, access to the river was difficult because of the steep banks. After finding a fishable spot and waiting about twenty minutes without a bite, I moved on.

My next idea was to fish below Rapidan Dam, but that turned into a wild-goose chase. The dam area has been heavily impacted by flooding and is now being decommissioned, leaving no practical fishing access.

I finally settled on Sibley Park, a beautiful park in Mankato situated near the confluence of the Blue Earth and Minnesota Rivers. Once I finally got a line in the water, I began catching several small fish that I initially assumed were Yellow Bullheads. After taking a closer look, however, I began to have doubts. The fish seemed much too sleek and handsome for a bullhead, and I wondered if they might instead be juvenile Channel Catfish. After posting a photograph to iNaturalist, my suspicion was confirmed.

Channel Catfish (juvenile)
Minnesota River, Sibley Park

The most obvious field mark that distinguishes the fish I caught from a Yellow Bullhead is the deeply forked tail. Bullheads have a square or only slightly rounded tail, whereas Channel Catfish have a distinctly forked one. The fish also had a long, streamlined body, a relatively small and narrow head, silvery-blue coloration with an olive back, and faint dark spotting along the sides, all features consistent with a juvenile Channel Catfish.

What struck me most was how different these juvenile Channel Catfish looked from the large adults I had caught previously. Large channel cats develop broad heads, heavy jaws, and thick barbels that give them an impressive, rugged appearance. In contrast, these young fish were remarkably elegant. Their streamlined bodies, forked tails, and subtle iridescence created flashes of blue, silver, and gold in the sunlight.

Although the Channel Catfish was not a new species for my list, the outing was nevertheless satisfying. Catching these juvenile fish gave me a deeper appreciation for a species I thought I already knew. Having previously caught only larger Channel Catfish, I had never really noticed how sleek, elegant, and attractive the young fish can be.

Fishing Near Home

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In case you haven’t read any of my other posts, I live in Rochester, Minnesota. I’m a soon‑to‑be fully retired molecular pathologist. Over the years I developed genetic tests for diagnosing and guiding treatment for cancer—one example is a urine‑based test for detecting bladder cancer. With my team, I implemented these assays and signed them out to help oncologists and other physicians care for their patients. It’s been a rewarding career, but now it’s time to pursue my many hobbies, one of which is fishing.

I eventually hope to fish in places like Florida, Texas, and California to reach my 100‑species goal, but most days I’m content fishing close to home. Yesterday I woke up at 5 a.m. to get out before the heat—and because the early bird gets the fish.

I started in the tailwaters below the Silver Lake dam and caught a White Sucker, a Bluegill, and three Bullheads (likely black; next time I’ll check the barbel color more carefully to be sure). After that I headed to Foster Arend Lake to fish from the pier. Even at 8 a.m. it was crowded and already hot with no shade. I caught a good‑sized Bluegill, then decided to look for somewhere quieter.

That led me to explore a few places I’d never fished before. I drove north to Oronoco, a town of about 2,000 people roughly ten miles north of Rochester. The Middle Fork of the Zumbro River runs through town. In the 1930s a dam was built to create Lake Shady, a recreational impoundment upstream of downtown. The dam was heavily damaged by a flood in September 2010, and instead of rebuilding it, the city chose a river restoration approach—replacing the dam with a series of rock‑arch rapids. The project was completed in the mid‑2010s and even received engineering awards in 2019.

Middle Fork Zumbro River

Once I arrived, I found the area promising—potentially a good spot for redhorse. I used my usual rig: 6 lb line, a 1/4‑ounce egg sinker, bead, barrel swivel, about 15 inches of monofilament leader, and a size 8 hook. After about five casts I felt what seemed like a snag, but it turned out to be a nice sized Golden Redhorse. I would have stayed longer, but the heat was building and the morning was getting late, so I headed home.

Golden Redhorse

On the walk back to my car I noticed a beautiful Cardinal Flower—probably my favorite wildflower—growing along the path. A perfect ending to an enjoyable morning of fishing.

Cardinal Flower (in front) and Wild Bergamot (in back)

Why I Don’t Own a Boat

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My wife tells me not to tell this story.

It’s embarrassing, but I’ve always had a sense of humor about my mistakes, so I’m going to tell it anyway. It also helps explain why, in my quest to catch 100 different fish species, I do most—if not all—of my fishing from shore.

This happened a long time ago, in 2001. I was about 42 years old, and my son was 11. Within the previous year, I had purchased a new Ford F-150 pickup and a new boat, an 18-foot Rinker ski boat. I asked my son if he wanted to spend a weekend fishing in the Brainerd Lakes area of Minnesota.

He said yes, so we packed up and headed north. I think we stayed in a hotel on Friday night and planned to return home Saturday evening. I can’t remember the exact lake. There are so many beautiful lakes in that area, and after 25 years they all tend to blend together.

We launched the boat and spent most of the day fishing. Unfortunately, the fish were not cooperating. By mid-afternoon we had not had a single bite and decided to call it a day.

That decision turned out to be the easy part. The boat ramp was extremely steep. As I started pulling the boat out of the water, I heard a scraping sound. From the boat, my son immediately started yelling: “Dad! Stop! Stop! Stop!” I instantly realized my mistake. I had forgotten to trim the outboard motor up before pulling the boat out. I put the truck in park, got out, and went back to the boat to raise the motor. Unfortunately, instead of trimming the motor up, I somehow trimmed it down. That was all it took. The truck’s parking mechanism disengaged, and in an instant the truck began rolling backward down the steep boat ramp toward the lake. I jumped off the boat and made a desperate attempt to get back into the cab and put the truck in park. I didn’t make it. Instead, I fell hard onto the concrete ramp. Fortunately, I missed going under the wheels. Had things been only slightly different, this story might not be getting written. I injured my arm badly in the fall while the truck continued its journey into the lake. The truck ended up window‑deep in the water. Once water gets into the circuitry, the insurance company considers the vehicle totaled, and that’s exactly what happened. The boat sustained damage as well, although it was eventually repaired.

If there is anything funny about the story, it was what we found when we finally opened the driver’s door. About seven sunfish had somehow made their way into the cab of the truck. Those were the only fish we caught all day.

Because of my arm injury, an EMT was called. One of the EMTs was extraordinarily kind and put us up for the night since finding a hotel on short notice would have been difficult.

The whole experience was stressful at the time, but it has become one of those stories that gets funnier with each passing year.

What may surprise you is that I kept the boat for another five years. During that time, I had many enjoyable fishing and water-skiing adventures with both my son and daughter. Eventually, however, we sold it. That reminds me of the old saying that the two best days of a boat owner’s life are the day he buys the boat and the day he sells it.

Now that I’m 67 years old and even less confident in my boating abilities than I was at 42, I’ve decided that shore fishing suits me just fine. I don’t miss launching boats, loading boats, maintaining boats, insuring boats, or writing checks for new boats. I’ve also discovered that rivers often hold a greater variety of fish species than lakes, which is ideal for someone trying to reach 100 species.

That’s not to say I’ll never fish from a boat again. If a particular species requires one, I’ll gladly hire a guide or rent a boat.

Mississippi River Pools

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Ever since I started fishing avidly in April, people have been giving me advice about which Mississippi River pool to fish for various species. If you want Bowfin, try this pool. If you want Sturgeon, try that pool. Looking for Walleye? Fish another pool.

I was vaguely familiar with Mississippi River pools but became curious about exactly what they were. I knew they were stretches of water associated with locks and dams on the Mississippi River, but surely they had not always been there. How many pools are there? Where are they located? And when were they built?

The Mississippi River pools begin in Minnesota, where the Mississippi River originates at Lake Itasca State Park. The pools are numbered consecutively as you travel downstream. The first Mississippi River navigation pool is Pool 1, located in the Minneapolis-St. Paul area. It extends from Lock and Dam 1 (the Ford Dam) upstream to St. Anthony Falls in Minneapolis.

A pool is the stretch of river between two locks and dams. Each lock and dam creates a backed-up section of river known as a pool. The pools are numbered in sequence as you move downstream. Pool 1 is in Minneapolis, Pool 2 is near St. Paul, Pool 3 is near Hastings, and Pool 4 includes Lake Pepin, one of the most popular fishing destinations in the Upper Midwest.

The last numbered Mississippi River navigation pool is Pool 26, located just north of St. Louis. South of Pool 26, the river becomes open river and flows freely all the way to the Gulf of Mexico without additional navigation pools.

Back in Mark Twain’s day, there were no Mississippi River pools. The Upper Mississippi was a free-flowing river with islands, side channels, wetlands, sandbars, and highly variable water levels. Commercial navigation was often difficult and sometimes impossible during periods of low water.

The locks and dams that created the pools were built primarily to provide a reliable 9-foot-deep navigation channel for commercial barge traffic between Minneapolis and St. Louis. The dams create deeper pools of water, while the locks act like elevators that raise and lower boats between pools of different elevations.

Most of the locks and dams that created Pools 1 through 26 were built during the 1930s, with the majority completed by 1940. A few notable exceptions include Lock and Dam 19 at Keokuk, Iowa (completed in 1913), Lock and Dam 1 in Minneapolis (1917), and Lock and Dam 2 (1930). The project transformed the river into what the U.S. Army Corps of Engineers has called a “stairway of water,” with locks functioning as elevators that move boats and barges from one pool to the next.

The locks and dams have had both positive and negative effects on the river ecosystem.

Negative impacts include the loss of a free-flowing river, increased sedimentation in backwaters, altered fish habitats, changes to islands and side channels, and the spread of invasive species. The navigation system created a more connected waterway, making it easier for some invasive aquatic species to move throughout the river system.

On the Positive side, the locks and dams created a reliable commercial transportation corridor, which was their primary purpose. They reduced transportation costs and helped farmers and industries throughout the Midwest reach national and international markets. Construction of the system also provided thousands of jobs during the Great Depression.

The pools created recreational opportunities since stable water levels support boating, fishing, waterfowl hunting, birdwatching, and other outdoor activities. Although some natural river habitat was lost, the pools also created extensive backwaters, marshes, side channels, and aquatic vegetation beds that support many species of fish, migratory waterfowl, bald eagles, and other wildlife.

In addition, many river communities upgraded their sewage-treatment and drinking-water systems after the pools were created because water-quality problems became more apparent in slower-moving water.

Finally, while the lock-and-dam system was not designed for flood control, it does provide more predictable river conditions for navigation and recreation than existed before the dams were built.

Overall, the locks and dams transformed the Upper Mississippi from a shallow, often difficult-to-navigate river into a dependable transportation corridor while also creating many of the fisheries, backwaters, and recreational opportunities that anglers enjoy today. The trade-off was the loss of much of the river’s natural, free-flowing character. Many of the productive fishing areas that exist today are a direct result of the pool system, while many of the river’s original sandbars, islands, and natural channels have been altered or lost.

Species #30: Golden Redhorse

/ kchalling / Leave a comment

I was shooting for Carp again. They have been surprisingly frustrating to catch.

Today was hot as heck—temperatures were in the upper 80s, with sustained winds of 20–35 mph. Still, I felt good about the day. In the morning, I cooked a nice meal of chicken paprikash and Brussels sprouts with bacon and onions. Then, in the afternoon, I met with my advisor from the Office of Staff Services to discuss and plan my retirement this October. With both of those tasks accomplished, I felt I had earned a little time to escape and do some fishing.

My first stop was Silver Lake, where Silver Creek enters the lake on the east side. Several people had reported catching carp there, so I thought it was worth a try. Unfortunately, I didn’t get a single bite. After about 30 minutes of sweltering heat and relentless wind, I decided to move on.

I headed downstream to the tailwaters below the Silver Lake dam. Once again, I targeted Carp using the same simple setup: 6-pound line, a light split shot, a size 8 hook, and a small piece of worm. Below the dam were a series of riffles, a run, and a deeper pool that looked promising.

Almost immediately, I started catching fish. The first was an average-sized Black Bullhead—not a new species for me, but always fun to catch. The next fish, however, was much more exciting. It turned out to be a Golden Redhorse, a species I had never caught before. It was a decent-sized fish and put up a respectable fight before coming to hand.

Golden Redhorse

The action continued for the remaining hour that I was there. I caught six more Black Bullheads and a Bluegill, but despite all the activity, I still failed to land a Carp.

That’s okay, though. I’m sure I’ll catch one eventually, and the Golden Redhorse made the trip worthwhile. Adding a new species to my list is always exciting.

History of the Clean Water Act—and Why It Matters to Fishermen

/ kchalling / Leave a comment

While fishing the other day, I found myself thinking about how river water quality compares to when I was a kid in the 1960s and 1970s. It seems much improved today, even though there is still room for progress.

The first Earth Day was held on April 22, 1970, when I was just 11 years old. I remember it being a big deal, but I had little understanding of what it was about—at the time or even until recently, when I read more about it. One of the most important outcomes, especially for those of us who fish, was the passage of the Clean Water Act.

The Clean Water Act grew out of decades of largely unsuccessful efforts to control water pollution in the United States. Earlier laws, such as the 1948 Federal Water Pollution Control Act, relied mostly on voluntary cooperation and had minimal enforcement power. By the 1960s, many rivers and lakes were heavily contaminated with industrial waste and sewage. Public concern reached a peak after events like the 1969 Cuyahoga River fire, when a polluted river literally caught fire.

In response to this environmental crisis and rising public pressure, Congress passed sweeping reforms in 1972 that became known as the Clean Water Act. Despite a veto by President Nixon, Congress overrode it with strong bipartisan support. The law marked a major shift: rather than relying on voluntary measures, it made it illegal to discharge pollutants into U.S. waters without a permit and established a national regulatory system to control pollution.

Over time, the Act has been strengthened and refined. Amendments in 1977 expanded controls on toxic pollutants and industrial discharges, while changes in 1987 placed greater emphasis on state-led programs and addressed pollution from runoff sources.

Today, the Clean Water Act remains the foundation of water pollution regulation in the United States. It reflects a fundamental transformation—from weak, fragmented efforts to a strong federal framework designed to protect the nation’s waters.

Importantly, the Act applies not only to the rivers and lakes where I fish, but also to coastal waters and estuaries—essentially the country’s interconnected surface waters.

For more information on the history of the Clean Water Act (as well as the EPA and the Clean Air Act), see this excellent video.

Species #29: Shorthead Redhorse

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Woke at 5 a.m. to head back to Northfield below Ames Dam, hoping to catch a Redhorse species—though I would have gladly taken a Bigmouth Buffalo or Carp. I was set up and fishing by about 8 a.m.

I used a simple bottom rig: 6‑lb monofilament main line and leader, a ½‑ounce sliding egg sinker, barrel swivel, and initially a size 8 hook (later switching to a size 10).

After about 20 minutes, I landed a Freshwater Drum. Soon after, I hooked what appeared to be a Redhorse but lost it at the shoreline. The same sequence repeated—another drum, then another lost Redhorse. At that point, I downsized from a size 8 to a size 10 hook to see if it would improve hookups.

That adjustment paid off. I was thrilled to land my first Redhorse—specifically, a Shorthead Redhorse. Interestingly, it didn’t put up much of a fight initially, but as it neared shore, it surged with surprising strength.

Shorthead Redhorse

Unfortunately, the fish was gut‑hooked and visibly bleeding. I chose not to attempt hook removal; instead, I cut the line and released it. My understanding is that cutting the line is generally the best option in these situations, especially when there is bleeding. Attempting to remove a deeply embedded hook in species like redhorse—whose gill arches are delicate and whose throats are narrow—can cause far greater damage.

Research supports this approach. Once a hook passes beyond the tongue pad, removal often leads to tearing of tissue or injury to the esophagus or gill arches. Cutting the line avoids additional trauma. In many cases, the hook will corrode, become encapsulated by tissue, or eventually pass. Studies in similar species (catfish, suckers, carp) show significantly higher survival rates when anglers cut the line rather than attempt removal.

Redhorse are especially prone to gut‑hooking because of how they feed. They inhale food rather than striking it, feed head‑down so the hook slides inward easily, and produce a very subtle bite that’s easy to miss—particularly when using worms, one of their preferred foods.

The fish itself was striking. The fins were a vivid, almost glowing red—peak June coloration. Shorthead Redhorse are among the most beautiful freshwater fish in Minnesota. This coloration comes from carotenoid pigments acquired through their diet, with intensity enhanced by spawning‑season hormones.

These bright red fins likely serve several purposes:

  1. Spawning signal – helping fish locate each other in often murky water
  2. Species recognition – subtle differences distinguish species within the genus
  3. Health indicator – brighter coloration often reflects a well‑fed, healthy fish

This one clearly checked all three boxes—the most visually striking fish I’ve caught in some time.

Which Has Greater Fish Species Diversity in the US, Rivers or Lakes?

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The fact that I prefer fishing from shore has nudged me toward rivers—and that, in turn, led to an unexpected realization: rivers seem to hold an extraordinary diversity of fish. That observation made me wonder whether rivers actually harbor more species than lakes. It turns out they do—and it’s not even close.

So why is that? The short explanation is simple: rivers create more ecological niches per mile than lakes, and niches create species. This reflects a broader ecological principle. Ichthyologists have shown that lotic systems (flowing water) tend to support greater species richness at local scales than lentic systems (still water).

Again, why is that? Rivers generate a remarkable range of habitats—riffles, runs, pools, backwaters, floodplains, estuarine transitions, springs, tributaries, and headwaters. Each of these environments supports different species. In addition, rivers contain fine-scale microhabitats (eddies, seams, root wads, undercut banks) that further expand ecological opportunities. Lakes simply lack this degree of structural complexity.

Rivers also function as connected networks spanning large geographic areas. This allows for dispersal, isolation, recolonization, and ultimately speciation and helps explain why entire groups—darters, shiners, redhorse, and suckers—are predominantly riverine and have diversified into dozens (or hundreds) of species. Lakes, in contrast, are more like isolated bowls: excellent for stability, but less conducive to generating new species.

This pattern is especially evident in the southeastern United States. River systems such as the Tennessee, Cumberland, Mobile, and Apalachicola basins contain the highest freshwater fish diversity in North America—and among the highest in the world outside the Amazon. These are river systems, not lake systems.

So how large is the difference? Of the roughly 800+ freshwater fish species in the United States, the vast majority are associated with rivers and streams. Many are endemic to single watersheds. True lake-specialist species are relatively rare (for example, some ciscoes and pupfish), numbering only a few dozen. By contrast, river-dominated groups are extraordinarily diverse: redhorse (15+ species), darters (200+), minnows (300+), suckers (70+), and madtoms (30+).

None of this diminishes the importance of lakes—they excel in other ways. Lakes support high biomass, offer stable environments, and sustain large, iconic predators such as walleye, pike, and lake trout. They are also central to recreational fisheries. But they are not the primary engines of speciation.

If your goal is species diversity, rivers and streams are the heart of freshwater biodiversity in the United States. Lakes are wonderful—but rivers are where evolution does some of its most creative work.

Species #28: Brown Trout

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I woke up at 4:30 a.m. and headed back to the Root River in Preston, hoping this would be the day I landed a Brown Trout (Salmo trutta). It took about 45 minutes to get there, and I was fishing by 6:00 a.m. It was a little chilly, but a really nice morning—sun, scattered clouds, almost no wind.

This stretch of the Root River is fairly narrow and probably not very deep. The night before, I’d seen some kids swimming in it, and they were often able to stand with their heads out of the water. I’d guess it’s about 30–40 feet across in most places. Still, it clearly holds fish. On earlier trips I had already caught Rainbow Trout, Common Shiner, Creek Chub, and White Sucker.

I started out throwing a couple of small inline Panther Martin spinners. I should have written down the exact size and colors, but didn’t. One was all silver, and the other had green, red, and silver—at least I think that’s what it was. Probably the next-to-smallest size. I made around 40 casts without a single bite. Eventually I decided that was enough persistence for one lure.

The water looked a bit murky, probably from heavy rains the day before, and I began to suspect the fish just weren’t seeing the spinners very well. Or possibly they were seeing them and choosing to ignore them—always another possibility. Either way, I switched back to the bottom rig that had worked well on my last two trips: 6 lb monofilament, 1/8 oz egg sinker, swivel, about a 12-inch leader, and a size 10 hook with a piece of worm.

The action was pretty slow, but then I finally caught a Brown Trout. Not a huge one, but a nice fish and, more importantly, a new species for me. I posted it to iNaturalist and, I’ll admit, kept checking back waiting for confirmation. About eight hours later someone confirmed that it was a Brown Trout. I also picked up another Common Shiner along the way.

Brown Trout

After that, I switched things up and headed over to the Mississippi River to try for Bowfin. That’s a completely different game—different rod, different rig, different mindset. No luck this time, but that’s probably a story for another day when I actually catch one.

With the Brown Trout, I’ve now completed the trout “triumvirate”: Rainbow, Brook, and Brown. I’ve caught Rainbow in Minnesota and Washington, Brook in Washington, and now Brown in Minnesota. Next on the list are Lake Trout, Splake, and Tiger trout—because apparently there is always another fish to chase, and apparently I am fine with waking up at 4:30 a.m. to do it.