“LMR” is lower Mississippi River, the 1000-mile stretch from the mouth of the Ohio River at Cairo, Illinois to the Gulf of Mexico. “10 kph” is 10 kilometers per hour, a speed equivalent to about 6 miles per hour.

That is how fast we go downstream when we are tracking sonic-tagged sturgeon to determine their location.

For 15 days beginning the last week in October, my graduate assistant Dylan Hann and I traveled in two boats from Memphis, Tenn., to New Orleans to check the whereabouts of pallid sturgeon and shovelnose sturgeon we captured and implanted with ultrasonic sound-emitting transmitters during the last four years.

Research-wise, it was a successful trip. We detected almost 200 of our tagged sturgeon, and these data hopefully will advance our knowledge about the movement and habitat use of these ancient, large river fishes.

That information will be used by managers to conserve their habitat and ideally rebuild their diminished numbers.

For 15 consecutive days, we progressed downstream, listening to the raspy hum of the receivers that translate sound trains of the sonic-tagged sturgeon. Each tagged fish has a slightly different sequence of sound pulses, and the receiver translates each sound-pulse signature into a code number that tells us the identity of the sturgeon.

When a fish is detected — the sonic pulses can be detected more than a half mile away — the boat is maneuvered to pinpoint the location of the fish. Then, we resume our downstream passage.

When evening approached, we sought a suitable campsite, took a bath in the river (invigorating when the air and the water temperatures are 60 degrees), pitched our tent, collected firewood on the few days when it didn’t rain, cooked supper, swapped a few stories, told a few lies and got a good night’s sleep.

But this column is not about sturgeon. It is about where the sturgeon and 136 other species of freshwater fish live — the lower Mississippi River — a river of significant magnitude, whether measured by size, economic importance, management challenge, myths or the abundance of fish.

In those 15 days, we encountered more than a hundred tows, several thousand barges and four fishing boats. And a total of seven people — four recreational anglers and three commercial fishermen.

Many years of sampling fish in the Mississippi River with nets, trotlines and electrofishing have proved that the river is literally full of fish. “Stir ‘em with a stick” might come close to being accurate.

Yet, only seven people were fishing. I haven’t been on every lake and river in the country, but I am confident that the lower Mississippi River has to be the least-fished water body in the United States.

The river is an engineering marvel. Dike fields — long fingers of large quarried rock extending from the bank to the channel — direct the flow of water toward the main channel, harnessing the flowing water’s energy to maintain a deep, snag-free channel for commercial navigation.

Across the river and downstream from the dike fields are revetted banks — river banks paved with concrete slabs and large quarried rock to forestall bank erosion and allow the river to sweep in a wide arc before again being deflected by wing dikes.

This pattern is repeated throughout most of the lower Mississippi River.

But the river is also a precious natural resource. Although extensively altered for navigation and flood control, the river still flows without impoundment from the mouth of the Missouri River near St. Louis, Mo., to the Gulf.

It is primitive, expansive and an unexploited fishery resource. You’ve read stories about expensive wilderness fishing trips to inaccessible, little-fished lakes in Canada or maybe some undeveloped river in South America.

You have that fishing opportunity right here, right now. And it’s free.

Is the river dangerous? Yes, if you’re foolish. I, my students and some of my fisheries colleagues have worked on the river in 16- to 20-foot johnboats for years without mishap.

But caution, vigilance and respect for the unstoppable power of the river are keys to safety and survival.

Catching catfish is easy. Natural banks — near-vertical clay banks without revetment, often located in protected secondary channels and containing numerous fallen trees — are homes to abundant flatheads. Deep holes are often stacked with blues.

Of course, refinement of these patterns, which comes with experience and researching river catfishing methods, increases the numbers and size of your catch.

If you want to fish the Mississippi River, download the Lower Mississippi River Conservation Committee’s guide to fishing the Mississippi River at www.lmrcc.org/programs/fishing-the-lower-mississippi-river-initiative.

If you, or you and a group of friends, want to experience the river to its fullest, visit the website for Quapaw Canoe Company (www.island63.com) or contact John Ruskey at john@island63.com. Ruskey and his team of knowledgeable and experienced guides are slowly — one party at a time — sharing the magic of one of America’s greatest resources.

Whether fishing or just touring, on your own or with an outfitter, the lower Mississippi River is an adventure available to all but experienced by very few.