January 13, 2016

The Mighty Mississippi and the Louisiana Marsh

The Mississippi is rising and spillways will alter fish patterns. But why are the spillways there and how can we catch fish despite the river water?

The breezy summer air blew across my face as I stood on the bow of the bay boat. It was 7am and the sun was well above the horizon. I sighed, looking around for any sign of diving birds and there were none.

The bow of the boat continued to rise and fall gently, up and down. It was quiet and rather serene on the water, interrupted only by clients talking amongst themselves.

Inside my head was a different story, there was a great tempest, a battle going on as to what I should do next to put my clients on a great trout bite; for it was 7am on a June morning and we only had a few speckled trout to show for it.

“Time is burning. Figure something out.”

Peeking over the horizon was my next spot, a natural gas platform that had been put in place a long time ago, probably before I was born. I had caught many specks there over the years and had caught there recently as well.

It would be a bumpy seven mile run, seeing there was a 15 knot wind, that would be worth it if trout were there. The anchor came up, the trim tabs went down and off we went, rocketing towards our new destination.

We were halfway there when I came off plane and made the command decision to turn around. Seeing the confused looks passed around the boat, I merely pointed at the water less than a hundred yards away.

“River water.”

More confused looks went around. I told them I would explain later. Time was burning and, begrudgingly, I knew it was time for Plan Redfish.

I had a lot of fun running the charter that day. No two days are ever the same and I was up for the challenges thrown at me, especially those posed by the Mississippi River. We had to jump around a couple spots, catching one or two redfish here and there, but we went to one spot where the bite was on fire and we caught our limit of twenty redfish.

I did take time to explain why we turned around.

While they were fishing, I’d narrate the history of the River and it’s impact on us in Louisiana. I explained to them the brown, dirty water we saw was water from the Mississippi River. I went on to talk about how speckled trout hate dirty water and will abandon an area if it is present.

Even being as far away as we were the Mississippi River could still influence the area, especially with the aid of tide and wind.

This was mind-blowing to one gentleman on the boat, who couldn’t believe a river so far away could have such a powerful effect.

After all, he could see no land from our location in Breton Sound.

Brief History of the River

If you don’t want to read this part then scroll down to the part relevant to fishing.

The Mississippi River is older than the oldest old-timer you will ever take fishing advice from. She is worth talking about because she is the reason for everything that ever defined Louisiana.

If you look at bayous like Bayou LaLoutre in St. Bernard Parish and Bayou Lafourche in Lafourche Parish you will see they run straight, long and true. Those waterways used to be the main channel of the Mississippi River.

It is said that Bayou LaLoutre is where the Mississippi River flowed about 3,000 years ago and the River would change course about every 1,000 years.

She would flow in one direction for an eon, building up land mass before finding an easier path to the sea and beginning a new chapter in her life. Over time, she built an incredible estuary for all kinds of fishing.

The Mississippi River would build land by taking sediment from other parts of the North American continent and dumping them off here in Louisiana. This would take place during the spring months, when the River would swell from all the snow melt up north.

Controlling the River

Man began to populate land around the river and found her annual flood an obstacle to progress. We suffered many catastrophes caused by the Mississippi River, namely in 1927.

The Flood of ’27 was one of nightmarish proportions and affected ten states. Right now, the Mississippi River is flowing at about 1.25 million cubic feet of water per second (CFS) and during the Flood of ’27 she was flowing nearly three times that amount at over 3 million CFS.

That’s enough water flow capacity to fill the Superdome in less than a second.

Through time we have learned there are three ways to control the Mississippi River’s enormous flow capacities:

  • cut offs
  • spillways
  • levees


A levee is a high wall designed to prevent the Mississippi River from flooding an area. If you have been in Louisiana for five minutes you have seen a levee. They are usually constructed from earth.

Once upon a time, it was believed that only levees can control the river and this approach contributed to the disaster of the Flood of 1927.

Cut Offs

The Mississippi River is a twisty-turny river. These turns allow river water to remain in an area longer than what it needs. These turns also weaken spots where river water can ram against the shoreline, causing the levee to break.

We overcome the danger of these turns by creating a “shortcut” across them. We literally cut a path through the turns, providing an easier, straighter route for the river.

A cut off looks like a dollar sign, $. The “S” part is the original path of the river and the vertical line is the cut off. Using cut offs causes river water  to run straight and true, leave the area much faster and relieve pressure on levees.


Spillways are an intentional break in the levee designed to allow the river flow into another area, relieving pressure on the levees downstream.

The Bonnet Carré Spillway is a great example. Rather than send additional river water towards the all-important Port of New Orleans, the spillway diverts the high river water into Lake Pontchartrain and, subsequently, into the Gulf of Mexico.

As I sit here and write this article the Army Corps is opening Bonnet Carré Spillway to safeguard everything downstream of it.

Confining the Mississippi River has not been without consequence. The full strength of her land-building capabilities is had when she is at a flood stage because faster water currents can carry a higher sediment load.

Being cut off from the River has forever changed our marshes.

How River Water Affects Inshore Fishing

River water is both a blessing and a curse, according to Venice native Captain Boola Landry.

That dirty water is a blessing because it nurtures inshore life, in the long term. For the short term it chases away fish. For a trout or redfish, dirty river water is like being stuck in a sandstorm.

I can tell you it is miserable. You get a layer of dust in your nose, grit invades your mouth and sand finds a way under your eyelids. Fish have gill plates that can be irritated by the suspended sediment (read: dirt) of river water and will avoid it like a plague.

They will simply go somewhere else.

Update In 2016 we had the displeasure of the Bonnet Carré being opened, putting river water once again into salty Lake Pontchartrain. On top of that, more river water was introduced via a 500 year flood in April then a 1,000 year flood in August.

After August we had a drought and stiff east winds to balance it all out. This combination contributed to the best speckled trout fishing the Lake had seen in years.

You can read more in this fishing report (click)

How can we catch fish despite the spillway?

This is really easy: don’t fish in river water.

Fish anywhere but where you see river water. As the river water spills from Bonnet Carré and heads east it will drive the fish east.

Fish will leave the Causeway to go to the Trestles. When river water covers the Trestles, they will leave there and head to the the Wall and Lake Borgne. Some of them may even cross Lake Borgne and go to the Biloxi Marsh.

I know I have tagged speckled trout in Bayou Biloxi and had them recaptured at the Wall, so its not unreasonable to assume some of them will go to places like Bayou St. Malo, Muscle Bay, Stump Lagoon and more.

The Biloxi Marsh, for the most part, is protected from freshwater sources on each side.

It’s important to note that freshwater is lighter than saltwater and can float on top rather than mix. If you are fishing an area with a light smattering of river water then try fishing deep, to where the saltier water is.

Remember why trout seek deep water during the wintertime and if you want to get your lure to the bottom of a deep hole, you need to use a heavier weight or jighead.

You should use at least a 3/8 oz weight but don’t be surprised if you must go heavier, like a 1/2 oz weight. A drop shot with a really heavy 1 oz weight would definitely get the job done.

How long will the spillway be open?

This is a question no one really has the answer to as the spillway has never been opened this early before.

The Mississippi River drains all the land from New York to New Mexico, so who can say? In addition to this, there is a lot of snow up north that has yet to melt.

When it does, it will find its way to the Mississippi and come to Louisiana. Bonnet Carré can be open for a long time. In 2011 it gorged river water for 42 days with nearly all of the bays opened (330 out of 350, the Bonnet Carré Spillway is opened one bay at a time by use of a crane) and discharged water at a rate of approximately 235,000 CFS.

At the end of the day, the spillway is there to save people, homes and businesses so the river does not interrupt our lives as it once did. Yes, it is a minor inconvenience to us fishermen, but fortunately today we have high horsepower outboard motors that can simply take us somewhere else.

The true victims of the spillway are the businesses who rely on the water. Marinas and commercial fishermen will get hit the hardest and it’s courteous to keep that in mind.

Consequences of River Water

The Mississippi River is not what she was a hundred years ago. Today she carries pollutants and invasive species of fish like Asian Silver Carp. Her impact on Lake Pontchartrain and other areas can have detrimental effects.

There are government agencies monitoring for these effects in order to protect the surrounding areas.

Ultimately, time will tell.

Education is Key

Knowing inshore fishing and conservation in Louisiana means knowing the Mississippi River and its history.

I strongly suggest reading Rising Tide: The Great Mississippi River Flood of 1927 and How it Changed America by John M. Barry.

The author does an excellent job of detailing the history of the Army Corps of Engineers, the Mississippi River and how everything came to be in its present form.

For example, you may not have known the Bonnet Carré Spillway was originally formed by a break in the levee in 1871 and that the idea for the Mississippi River Gulf Outlet (MRGO) originated in 1832, over a hundred years before it was dug.


Captain Devin

About the Author

Devin is a veteran of the Iraq War and former fishing guide. He founded Louisiana Fishing Blog in 2012 to share his ideas as a charter captain and still writes in it today. Since then he's created a fishing university — LAFB Elite — where he teaches inshore anglers how to safely navigate Louisiana's coast and catch more fish.

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