Good crappie fishing often depends on a strong year-class: an abundance of fish produced in a given year. When those fish grow to a size of interest to anglers — what biologists call “recruit to the fishery” — the result is fast action, filled limits and full coolers. Fast growth and limited harvest often equates to super slabs for the next several years. 


Spawn importance

Although crappie will spawn along the barren shorelines of Mississippi’s flood-control reservoirs, greater survival of spawned fry usually occurs when high water in the spring floods shoreline vegetation in the main lake and lowland vegetation growing on the flood plains uplake, and in major creek arms where the rivers and smaller tributaries enter the lake. 

I explained last month that Mississippi’s flood-control reservoirs — Arkabutla, Sardis, Enid and Grenada — were built to reduce flooding in the lower Yazoo Basin. To accomplish this purpose, they are drawn down in the fall and kept at low levels through winter and spring to allow for storage of runoff from the upper Yazoo Basin. The prescribed seasonal changes in water levels are called the “rule curve.” Unfortunately, fulfilling their flood-control purpose results in water levels not always conducive to strong crappie spawns.

In some years, downstream flooding or heavy rains in the Yazoo Basin result in the reservoirs having high water early in the year. These years typically feature a strong spawn, according to Keith Meals, a veteran fisheries biologist for the Mississippi Department of Wildlife, Fisheries, and Parks who oversees fisheries in the flood-control reservoirs.


Judgment day

A weak spawn will never produce a strong year-class, but Meals makes it very clear that a strong spawn does not always produce a strong year-class. In all fisheries, winter is an invisible killer of young fish. 

Young crappie are limited in the size of forage they can eat. Winter is a season of dwindling food supply as the number of small, young forage fish declines and the survivors become too large to eat. Invertebrates also are an important food resource for young crappie. Many of these invertebrates, especially aquatic insect larvae that have summer-to-summer life cycles, are abundant but small. Further, fall drawdowns on flood-control reservoirs massively reduce the numbers and habitat of aquatic insects. Larger crappie have ample energy reserves in their own bodies to endure lean times, but a long, cold winter takes a toll on small crappie that have little to eat and few energy reserves to draw on. 

High overwinter mortality is common in many fisheries, but according to Meals, young crappie in flood-control reservoirs face another threat: rapid water withdrawals. In a normal fall, water is slowly discharged to lower the lake levels to winter pool to provide flood storage capacity. An exceptionally wet fall or winter refills the reservoir and necessitates high discharge to restore the capacity. With the gates wide open, water and fish — including crappie — leave the reservoir. 

Young crappie are weak swimmers compared to their older and larger kin. Cold water lowers their swimming ability and further increases their vulnerability to getting caught in the discharge. Monitoring some years ago substantiated that losses of young crappie can be high.

Not knowing what future precipitation will be, or how many young crappie will be caught if high winter discharges occur, Meals always withholds judgment on the strength of a year class until the spring after the fish were spawned.

Are high, winter discharges common? Let’s say they are not unusual. This year, for example, heavy rains in the Coldwater River basin in early January raised Arkabutla Lake well above the winter pool specified by the rule curve. The discharge gates were opened to allow 5,000 cubic feet of water per second to flow out of the reservoir, and the lake level was lowered 13 feet in 21 days. Multiple rainfall and discharge events in a season make fish losses greater, and in late February, Arkabutla had again risen almost to spillway elevation. 

Mississippi’s flood-control reservoirs are among the best, and in any given year might be the best, crappie fisheries in the country. But the abundance of crappie in these reservoirs depends on water — how much, when it comes, and when and how fast it goes.