Life on the Mississippi: Tale of the Lost River Shrimp

The 20th-century re-engineering of the Mississippi River wreaked havoc on natural systems and devastated once-abundant populations of native river shrimp. Biologist Paul Hartfield has focused his work on studying these creatures, which were known for making one of the world’s great migrations.

“Ninety percent of science is zeros.”

This piece of Southern wisdom was delivered to me out on an expanse of big flat Mark Twain Mississippi River water near Vicksburg, Mississippi. The biologist Paul Hartfield had just piloted his secondhand skiff that his under-funded division of the U.S Fish and Wildlife Service had procured to a little eddy behind a snag of old trees that the river had whipped out of its pathway. With the boat secured, he used a grappling hook to claim a buoy in the water that was tethered to a rope and in turn tethered to a wire mesh trap which had been baited with a can of cat food. Lifting the trap out of water he cracked it open and found … nothing.

Macrobrachium ohione river shrimp
The tiny river shrimp, Macrobrachium ohione, grows up to four inches long. USFWS

Hartfield and his research assistant Tyler Olivier had put out the trap the night before hoping to catch samples of Macrobrachium ohione, a variety of what are generally called “Caridean” shrimp, which live in the Mississippi River and other Southern waterways. An odd-looking creature with one oversized claw (macrobrachium meaning “large arm”), it is pale in color and, today, just as invisible in its public profile.

Previous to my visit with Hartfield, I’d always thought of shrimp as ocean creatures. But when Hartfield introduced me to the oddly overlooked M. ohione, I came to understand what had happened to shrimp-kind. For it turns out that the creature was the original shrimp of the bayou, the one that started the great pink gold rush that would take the world by storm. That it would be Paul Hartfield who would be the one to help put the ohione back on the map makes sense. For Hartfield is a man whose life has been governed by storms.

A lanky stick of a guy in his 60s, Hartfield is as spry as a man half that age. It was a storm he experienced as a young man in his native Mississippi that altered his path and led him to the river shrimp. In 1977, he took a job with the Mississippi Museum of Natural Science in Jackson. Two years later, water from the Pearl River Easter flood inundated the museum, playing havoc with the archive of shelled creatures holed up in the museum’s nether parts. Particularly ravaged was the collection of freshwater mussels. Though not a mussel biologist by training, Hartfield had a knack for general taxonomy, and he then proceeded to sit for nine months re-labeling and categorizing the collection.

In pre-colonial times, river shrimp traveled all the way north to the Ohio River and back again.

From that point forward, Hartfield embarked on an unusual scientific career geared toward discovering and studying ignored creatures. In his picaresque biological journey, he crossed over from taxa to taxa, until he had a sense of the entirety of the lower Mississippi’s ecosystem. He has helped initiate recovery strategies and actions for the river’s five-foot long prehistoric endangered pallid sturgeon. He has identified countless nesting sites for the endangered interior least tern on sandbars and islands that dot the river. But for him, the thing that truly revealed the nature of Old Man River and what humankind had done to it was M. ohione.

“I had a shrimp boat and I was a shrimper in my youth, and so I knew how to work a shrimp net. And when I started studying pallid sturgeon I found river shrimp made it into my nets. I started sampling in the river to do some initial studies and I came to understand that this was one of the great migration stories of the world, and it was so poorly known.”

Paul Hartfield
Paul Hartfield checks a trap for river shrimp. USFWS

It turned out that in pre-colonial times the shrimp traveled all the way north into the upper reaches of the Mississippi’s main eastern tributary, the Ohio River, and back again — a 2,000-mile round trip. It was a journey more amazing than similarly epic migrators like salmon. For whereas adult salmon may have an equally long journey to their upstream spawning sites, it is the quarter-inch juvenile shrimp that swim and crawl 1,000 miles upstream against the strong currents of the Mississippi.

Hartfield turned to historical fishing records and found that not only were river shrimp present in the days of the early colonization of the river, they were a major source of food. In fact they were the shrimp that poor French Acadians found when they migrated from Canada. In 1898, 200,000 pounds of river shrimp were taken by the poorly documented fishery of the Mississippi River and we can assume many more were caught and never reported. Albert “Rusty” Gaudé III in the Louisiana Sea Grant office confirmed this. “I ran the numbers,” Gaudé told me, “and that catch was worth millions of dollars not in today’s dollars but in their money.”

But out on the river, as we hauled up trap after trap, we found only one or two shrimp per trap. Where had they all gone? I asked.

“Ah hah. Where indeed. Tyler?” Paul Hartfield asked socratically of 28-year-old graduate student, Tyler Oliver. In spite of the modest financial prospects of a career in science, Oliver had decided to do a Ph.D. and to make the river shrimp in the Atchafalaya River the subject of his thesis. A chance encounter brought them together and revealed their mutual fascination with the river shrimp as well as the benefits of pooling their efforts. In the formal and yet intimate way of the South the younger man addressed the elder as “Mr. Paul.”

“Where’d they go Mr. Paul?” Tyler answered shaking out a shrimp trap, “Well, they straightened the river.”

“That’s right,” Hartfield said slapping his knee, “they straightened the river.”

The natural way of the Mississippi, and indeed all rivers, is to meander and flood.

The natural way of the Mississippi (and indeed all rivers) is to meander and flood. The turning of the earth bends a river askew as it makes its way downhill. Gravity draws the river back down its original path but momentum causes it to overshoot its gravitational mark and bend again, this time in the other direction. The result is a curvaceous affair wending from the top of the continent in Minnesota down to the bottom in southern Louisiana. A river like that has a wide floodplain rich in nutrients that drop out and fertilize the flora and in turn generate long chains of life from algae up to large carnivores.

Indeed, though the generally accepted Indian meaning of the name Mississippi is “father of waters,” some etymologists say the name stems from the language of the Outouba tribe in which the word Missi meant “everywhere” and sipy meant “river.” Mississippi — literally “the river that is everywhere.” This describes the river as it is really supposed to work — a floodplain dozens to hundreds of miles wide, that gathers water draining from the Rockies to the Appalachians. A sloppy mess where water does what it wants to do.

But not only does water do what it wants to do, it does what fish and shrimp want it to do. The Mississippi once abounded with local fish. River shrimp, giant catfish, caviar-producing sturgeon, a carp-like creature called a buffalo fish — all supported a vibrant local fisheries economy.

Locks and dams on modern Mississippi River
The major re-engineering of the Mississippi occurred after the Great Flood of 1927. U.S. ARMY CORPS OF ENGINEERS

But a river that is everywhere is hard to use toward profitable ends. Oxbows made the Mississippi frustratingly long for travelers. It also regularly overflowed its banks and in certain years it up and moved completely. Channels that were one year navigable by steamships the next became dry sand bars. It was in response to one cataclysmic event, the Great Flood of 1927, that the nation decided enough was enough. The river had to be contained, fish and shrimp be damned. Though levees had been built piecemeal along the river prior to 1927, the Great Flood would spark a wholesale reimagining.

“After the great flood, the farmers along the river wanted the Army Corps of Engineers to do something,” Hartfield told me as we hauled up anchor and sped further up river to pull more shrimp traps. “They wanted the river to be faster and shorter. Most engineers said it was a bad idea. They knew even back then that the river has a way of finding its own equilibrium. And then a man came along who, after all those others said no, said yes. Colonel Harley Bascom Ferguson said, ‘I will do it, and the river will be stable within ten years.’”

The result of this extraordinary act of engineering is that the Mississippi is now a “perched river.” Standing on what was once the floodplain, you must literally look up to see its waters. With all of the straightening, the Mississippi now tears through the southern states at current speeds too fast to allow river shrimp to complete their migration. In addition, all that velocity rips mud and silt down river far faster than it did pre-colonization. By the time the silt reaches the delta, instead of slowly dropping out and building out the alluvial plain, it shoots out into the Gulf of Mexico where it does nobody any good.

In fact it does harm. The nitrogen-rich nutrients that would have normally settled out and fertilized the floodplain further north, instead fertilize the ocean, causing algal blooms. Bacteria consume that algae when it dies, sucking out oxygen as they do so. The result is a large Gulf of Mexico hypoxic or “dead” zone that now affects ocean life to a disturbing degree.

By troubling the river shrimp of the Mississippi, we have also troubled ourselves.

One can throw up one’s hands at all this. Even Hartfield concedes that the Mississippi is “the most engineered river on the planet” and that the forces required to re-engineer the Mississippi into a more river-shrimp-friendly place are monumental. And after all, what do we care if we traded a few trillion river shrimp in exchange for millions of tons of corn, soy, and cotton that we now grow on the floodplain that shrimp used to inhabit?

But there are bigger forces at work that we should care about. Because by troubling the river shrimp, we have also troubled ourselves.

After our day out on the river we retired to the sturdy and beautiful wood house Hartfield had built with his own hands. There, after a meal of wild catfish from the Mississippi, Tyler did an oral presentation of his graduate-school thesis describing the miraculous journey of the river shrimp and the sampling he was doing to demonstrate the migration.

As he talked, a storm brewed. Lightning flashed all around. And then the largest thunder crashes I had ever heard boomed through the house. “Don’t worry,” Hartfield said, “After my last house burned down, I totally overbuilt this one.” On and on through the night the storm raged. The hand-built house shook and rattled. The rooms were illuminated by so many lightning strikes that it seemed like dawn. It was a night that was to become infamous in the South as a night of a hundred tornadoes. But Hartfield’s house held firm.

The next day after bidding goodbye to Paul and Tyler, as I drove downriver toward the Gulf, I listened to the car radio describing how the Lower Mississippi all up and down its length was threatening to blow out levees and inundate the farm land of the Black Belt.

The Mississippi was being true to its Native American name. The river was trying to go everywhere.

And as I listened to the news of the flood unfolding, I couldn’t help but think about the river shrimp and how by making the river unsuitable for them, we were at the same time making life in the river’s valley unsuitable for us. Perhaps in the century ahead, working against the river and the river shrimp is not the best thing we could do. I thought about what Hartfield had told me when I asked him what he’d do if he could have all the money in the world to fix the Mississippi.

“If I had all the money in the world?” he said considering the big open river before him. “I’d move the levees back five miles, then turn it all into a park from Cairo to Baton Rouge. Then I’d leave it alone and let it fix itself.”