While most Louisiana bass anglers pay close attention to rising and falling water temperatures during the spring, anglers in the Atchafalaya Basin pay far closer attention to rising and falling water levels.

In fact, seasoned bass fishermen on the Atchafalaya Basin will be quick to tell you that the water level is the single most important factor that determines how successful a fishing trip to the basin will be — and how to approach the fish.

The Atchafalaya Basin is not a lake, but a river’s overflow swamp that’s contained between two levees. The levees extend approximately 65 miles in length and are 25 to 30 miles apart. They run from the river-control structure near Simmesport to Atchafalaya Bay.

ABOUT THE BASIN

Through the basin, the Atchafalaya River diverts up to 30 percent of the Mississippi and Red rivers’ combined flow. A river-control structure splits all the water that comes down the Mississippi River and Red River so that 70 percent remains in the Mississippi. Most of the basin is east of the Atchafalaya River channel, making most of the overflow from the basin on the east side of the river channel.

Mike Walker, an inland fisheries biologist supervisor with the Louisiana Department of Wildlife and Fisheries, recommended that fishermen check the river stage gauge at Butte La Rose near Interstate 10.

“The river may be as low as 3 feet in the summer and as high as 17 feet in December. The water will often go down during the spring but may stay high until midsummer,” Walker said. “Most of the locals use the river gauge almost exclusively to determine if fishing conditions will be good. Since the flow runs from north to south, there are places you can get in and fish on the northern part of the basin when the gauge reads 11 feet that you will not be able to get back into when the river drops to 9 feet, because there won’t be enough water in the channel. While fishing may be good in the northern part of the basin at 11 feet, if it’s that high on the southern end, the water is all over the woods. When it drops to 7 feet in the lower end, then the fishing will get better.”

According to Walker, during the drought years of 1998, 1999, and 2000 the basin never received a spring run-off flood. “The river stayed low for three consecutive years, with the water staying in the canals and bayous,” he said “This does a number of things, both good and bad. One of the bad things about the drought was that all the fish were trapped in the bayous and canals for three years, making them very accessible to fishermen. This type situation results in an increased harvest that can have a considerable impact on the fish population.”

Another negative impact of low water, according to Walker: Spawning areas are greatly diminished. Fish that would normally spawn after spring floods had dispersed water over the swamp would have less than 10 percent of the spawning area available, when confined to bayous and canals.

“Predation from gars, catfish, and other predatory species also increased because of the reduced number of acres under water,” Walker noted.

When floodwaters finally returned in 2001, the basin experienced a condition similar to the flooding of a new impoundment, Walker pointed out. As the water dispersed into the swamps, bass again had a large area available for spawning and feeding. Survival of young bass increased because of the expansive cover.

Adding to the “new-lake” phenomenon, food from the banks becomes plentiful after a flood. The flood of 2001 resulted in a strong year-class of bass, meaning that there was a good fry hatch for which the survival rate was good, and that an adequate food supply was available for that year’s hatch.

“The fish spawned in 2001 are now 14 to 15 inches or better,” Walker said. “We also had a good year in 2002. These bass are approaching the 14-inch minimum length by now. We also had a good flood in 2003, so we should have good populations of bass due to the past three excellent spring spawns,” said Walker.

Walker says that the basin thrives on alternating drought and flood cycles. The flood cycle increases the amount of forage available to bass and increases spawning habitat. When the river drops, the river exposes the bottom, which is a collection of sediment and organic material deposited by the overflow. Upon oxidizing, this material promotes the growth of vegetation, which in turn decays and contributes its nutrients into the water column. This oxidation also serves to compact the area as it dries out, creating harder substrates.