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  • Writer's pictureAllen Crater

Hunting Trophy Brown Trout In Marginal Waters

Updated: Jun 10

Large brown trout in a net

OH SHIT!" The words erupt without permission after two quick strips and a metallic flash engulfs my streamer. The rod pulses wildly as line burns out from under calloused fingers. I'm pretty sure I'm into one of the monster smallies this water is known for, until I get another look and realize I'm attached by nothing more than a thin clear thread to a trophy brown.

Fly fisherman in blue shirt and sunglasses holding a large brown trout

This unexpected brown came from marginal waters when we were chasing smallies

My buddy, Jon Osborn (Ozzy) and I live in a state that boasts an embarrassing abundance of quality cold-water trout fisheries: the Manistee, Pere Marquette, and Au Sable among the most notable, with several others of lesser renown, not to mention the dozens and dozens of smaller tributaries. And while many of these rivers fish well, they see their fair share of angling pressure.

So, in the cooler shoulder seasons, Ozzy and I like to chase brown trout in some of the state's more marginal water. Places that fly under the radar and see less pressure. Places that during the warm summer months you're much more likely to find bass or northern pike than trout.

Because browns are the best adapted of all the trout for more marginal conditions, you can find some true giants in unexpected places. And we have made it our mission to seek those places out.

We're not guides or experts, just two buddies that like to explore and love to fish. But we have learned a few things through trial and error that might prove helpful if you are looking at doing the same.

In this blog we are going to share a few of our tips and tricks, talk about scouting and planning, and discuss ideal conditions, equipment, flies, techniques and safety.

But the first thing we need to do is define marginal water.

Defining marginal water.

Generally speaking, marginal water can be thought of as water where, at least during summer months, you are more likely to hook into a smallmouth bass or northern pike than a trout.

Chart showing river water temperatures

A water temperature chart example from USGS

Jacob Lemon, Monitoring and Community Science Manager for TU says this:

"There isn’t a hard and fast definition for marginal water. There are just too many variables.


When I make maps, I usually place the cutoff where the maximum weekly average temperature (highest average temperature for any seven-day period throughout the year) exceeds 70. But this is an imperfect threshold that doesn’t hold in all situations.

Generally, streams classified as “cool” span the gamut from holding no trout to what I’d consider marginal trout water. I’d consider some cold-transitional streams marginal but others I probably wouldn’t."

In basic terms, temperature is one of the primary drivers of oxygen levels in a water system, and, generally speaking, trout require more oxygen than other fish. Trout need cold water to survive because cooler water temperatures allow it to hold more oxygen.

Our buddy, Tim Shultz, author of The Habits of Trout: And Other Unsolved Mysteries explains this phenomenon well.

"From an angler’s perspective, the oxygen content of water is determined by temperature and turbulence. The temperature dependence is governed by something called Henry’s Law. In simplified terms, the amount of oxygen in water decreases as the temperature increases. Freezing water at the standard sea-level barometric pressure contains about fourteen milligrams of oxygen per liter. At sixty degrees Fahrenheit, the oxygen concentration falls to about ten milligrams per liter. It’s down to about nine milligrams per liter at seventy degrees Fahrenheit. These concentrations are typical of calm, stationary water, though, and for the same reason swirling a spoon in your cup causes your coffee to absorb more sugar, the turbulent water around waterfalls and riffles generally contains more oxygen than the stagnant and slow-moving parts of a river or stream. Find a river with cool, fast-moving water, and you’ll find more oxygen. Find more oxygen, and you’ll find more trout."

But shoulder seasons on traditionally warmer or more marginal rivers can produce – especially during spring runoff, in the fall (assuming water levels cooperate), or even in the winter months.


For us, the "off-season" is for scouting. You can learn a lot through books, digital maps, rumors overheard at local taverns, bribery, and brute force (okay not that… but we don't rule it out).

Before you get too far in your explorations, you'll want to check the legality of the river you are targeting - some streams in Michigan (type 1 and 2) have limited seasons (typically the last Saturday in April through September 30th), while others (type 3 and 4) are open year-round, and others still have specialized regulations beyond these parameters. It's always best to check the rules before you go. This interactive map is helpful when searching out particulars for different rivers.

Often the key to success in marginal waters is to fish where others won’t – in many cases access to some of these out-of-the-way waters can be tricky for wade fishing, but with a canoe or raft you may be able to get to spots landlocked by private property or bypass tight confines of others. We often use OnX (or similar) to find potential locations and navigate difficult access challenges.

color coded map of Michigan showing river temperatures

Here’s a color-coded map of the watersheds provided by MITU. Take a look at the green sections, which denote large and small cool-water stretches, or what might be considered "marginal" water.


We find our most success fishing high, off-color water and cloudy days. But that isn't always the case. The key is to learn the optimal flow for the river you fish. Every river seems to have a sweet spot. For example, one river Ozzy frequents fishes best around 200 CFS. Flows above 300 mean it's blown out. Flows below 100 CFS mean it's running too low. It can be a narrow window.

The USGS website provides a number of tools to monitor stream flows and conditions.

We practice-catch-and-release angling so we don't fish for trout when water temps reach seventy. But, as temps approach this range, springs, seeps, and creek confluences, where there is an influx of colder water, can often hold fish.

Chart from USGS showing river flow rates

Here is an example of the USGS flow monitor. Generally speaking freshly rising water levels can turn on fishing in marginal waters.


Because in this type of fishing we target shoulder seasons (that often fall outside of typical hatch patterns) and big fish we are primarily fishing streamers (or mice/frogs on occasion), so when we go. we fish like we're chasing trophies – this type of fishing isn't a numbers game; this is a hunt for one or two trophy sized trout.

Given the nature of the flies we are throwing and the fish we are targeting, we typically leave the five weights at home and fish seven or eights, and we fish like every cast may be our last chance. That all being said, don't forget to pack at least one dry-fly setup, even in the shoulder seasons you can hit an unexpected hatch, and we have.

Because a lot of the water we fish is small and tight, we often reach for medium-fast action rods (instead of an ultra-fast action rods) for easier casting in tight quarters. When fishing streamers we throw sinking line – our favorite is the Sonar series from Scientific Anglers. While some of these lines in the Sonar family are built a half-weight heavy, we also, on occasion, over-line our rods to make the short, abbreviated casts we need. IE: using eight-weight line on a seven-weight rod.

With streamers, short, stout leaders are the name of the game. We typically use between three and four feet of straight fluoro in 12 to 20-pound.

Fly fisherman wearing camo and sunglasses holding a large brown trout


The first step is to learn a stream's predominant prey species (sculpins, sucker fry, crayfish, leaches, etc) and do your best to match it.

Many of these waters seem to have consistent favorites. But, just because a white Circus Peanut worked in yesterday's conditions, doesn't mean it will produce today. It's probably a good place to start, but don't get too fixated and be sure to change flies often (Kelly Galloup suggests anywhere between 5 – 15 minutes, depending upon density of trout in the stream you’re fishing) until you settle on one that seems to be drawing follows and strikes.

We often utilize articulated streamers for more movement in tight confines. And be sure to pack plenty of patterns, sizes, and colors – in order to hit the best spots, you’re going to need to sacrifice a few soldiers in the process, and it sucks to lose the one thing that is working. Trust us.

large brown trout being released back into the river after being caught


When exploratory fishing, and streamer fishing in general, the key is covering a lot of water. Employ machine-gun casts and keep the fly in the river as much as possible – save those false casts for dry-fly season. While you want to focus on the obvious spots: ledges, cut banks, color lines, feeding channels, and areas of cover, even unassuming water can hold big fish.

When fishing streamers, vary your retrieves and manipulate the fly with the rod tip. Ozzy and I have very different go-to retrieve styles, as do most of our friends – the key is to mx it up, incorporate pauses, and make the streamer "swim" as naturally as possible. Using a loop knot will give your streamer more action in the water.

While fast strips draw out the predator in browns, remember in colder (and sometimes even in the borderline warmer) water temps, slow down your retrieve for lethargic fish.

smiling fly fisherman holding large brown trout


When fishing in the shoulder seasons, we often finding ourselves fishing colder weather, and colder water – and sometimes from the somewhat precarious perch of a canoe. In these conditions it's critical to plan for potential hazards.

When fishing in these conditions, Ozzy and I both pack dry bags with extra clothes, matches, a handsaw, and a headlamp. It's sounds extreme but these items could literally save your life in a serious situation, or at least extend your time on the water in a less critical scenario. Beyond the dry bag we always pack at least one extra rod/reel, and, in the canoe, we make sure to tie down everything of critical importance.


Maybe the most important element in this style of fishing is persistence. This is a swing-for-the-fences approach that can lead to a lot of strikeouts before a home run. Think of each outing as a learning opportunity – sometimes you have to figure where the fish aren't in order to deduce where they are.

Last, be courteous. when you do find a spot that produces, don't blow it up. Be careful about photos and descriptions, and be judicious who you share it with – it doesn't take long to wreck a great spot.


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