The Magnolia State’s lakes and reservoirs offer some of the best crappie fishing in the country. Enjoyed by Mississippians for decades, the word about our high-quality crappie opportunities has spread, and now Mississippi is a prime destination for out-of-state anglers and crappie tournaments.
This is good for our state’s economy and, although some anglers disagree, good for fishing too — more anglers means revenue from more license sales that can be used to improve fishing.
Mississippi’s fertile waters and long-growing season have much to do with high production of large crappie, but crappies are notorious for cycles in abundance and size. The typical scenario is two to three years of good catches of large crappie interrupted by two or more years of abundant but small crappie. This cycle is the rule rather than the exception in lakes and reservoirs in Mississippi and throughout the Southeast and Midwest. And it applies to both black and white crappie.
The “small-crappie syndrome” and cyclic nature of crappie fisheries has challenged fisheries managers for decades. Crappie population cycles are tied to a fundamental principle of fisheries management called carrying capacity: a lake or reservoir produces only a certain amount of food that is shared by a population of fish or populations of several species of fish. Competition for that limited food reduces growth, and competition is usually greatest among fish of the same species.
Here is how this plays out for crappie. Young-of-the-year crappie feed heavily on zooplankton — the small, often microscopic, animals drifting in the water column. As the crappies grow, larger invertebrates like insect larvae and fish become bigger parts of their diet, and crappie growth rate is strongly linked to the amount of usable forage fish. The outcome of a limited supply of forage fish is simple: Few crappie sharing an abundant food supply results in fast growth, but a lot of crappie competing for the same food supply results in slow growth. You may have heard this called density-dependent growth.
Recruitment
Crappie cycles start with spawning. Crappies are pretty flexible in their spawning requirements, so the spawn usually is good. But a good spawn means little unless the fish survive their first winter and are poised to grow to a catchable size. Fisheries biologists call this recruitment — the measure of fish that will reach catchable size.
Is an abundance of large spawners necessary for good recruitment? Generally not. The success of recruitment is primarily determined by environmental factors. Strong year classes — the number of young produced in a year — generally occur when the weather is warm in the spring and early summer, when water levels are high, and when the flows through lakes and reservoirs are relatively low.
Growth
Beginning in the crappies’ second year in Mississippi waters, density-dependent growth kicks in to affect the crappie cycle. These age 1 crappie usually start their second year of life 4 to 5 inches long. If growth rate is good, the crappie reach 8 inches by the winter. But if it is a strong year class, the abundant crappie compete for food, and growth slows. These crappie may only reach 6 inches at the end of their second year.
The fast-growing crappie enter their third year of life at a size acceptable to most anglers and will grow to 10 to 11 inches by fall. The abundant but slowly growing year class will grow to 8 inches by winter at the end of their third year of growth.
The difference in growth may only be a couple inches, but the fast-growing fish enter the fishery a full year earlier and are producing quality-size fish by age 3. The fish in the abundant year class are barely keepers by age 3, and it will take them at least two more years to reach 10 inches.
Mortality matters
Mortality has two components: natural mortality and fishing mortality. For crappie, fishing mortality is harvest by anglers and the small amount of mortality that results from catch and release. Natural mortality is the sum of all the other forces of mortality, and includes losses due to predation and disease.
A crappie must survive to grow to large size. Annual mortality — the proportion of the population that is lost every year — often is as high as 70 to 80 percent for crappie populations.
This may make more sense if you look at it as survival, the complement of mortality. In Columbus Lake, annual mortality has been estimated at 75 to 80 percent. Therefore, 20 to 25 percent of the crappie in a year class survive each year. If you started with 1,000 age-1 crappie, 200 to 250 fish would be left by age 2. By age 3, the numbers would have dwindled to as few as 40 fish.
Managing with length limits
Crappie management has done an about face over the years. Thirty years ago, management agencies encouraged high harvests to reduce the abundant populations of small, slow-growing crappie. Sometimes liberal harvests worked.
Beginning in the 1980s, some managers advocated high length limits to reduce mortality and produce larger fish. The reasoning was that 10 slabs in the cooler provided a greater yield — the weight of the harvest — than 25 paper-thin 7-inchers. Sometimes the length limits worked.
Why would such opposite management strategies work sometimes and fail other times? Working closely with Mississippi Department of Wildlife, Fisheries and Parks, Dr. Steve Miranda and his students took a lot of the mystery out of crappie management when they assessed the interaction of growth rate and mortality. Using data for crappie populations in Mississippi and throughout the crappie’s range, high length limits, like a 10-inch minimum, improved crappie yield when growth rate was fast, natural mortality was relatively low and fishing mortality was high.
For a crappie population with fast growth, low natural mortality and high fishing mortality, yield with a 10-inch minimum-length limit could be 30-percent greater than with an 8-inch minimum. Under the same conditions, the average size of each fish could increase from a 3/4-pound fish with an 8-inch minimum to a 1¼-pound fish with a 10-inch minimum length limit.
At low rates of fishing mortality, as would be the case in fisheries with little fishing pressure or when large fish are released, the average weight of fish caught with a 10-inch length limit could top 1½ pounds for crappie populations with fast growth and low natural mortality.
The benefits of high length limits diminished for crappie populations with medium growth rate and moderate natural mortality. For populations with slow growth, high minimum-length limits often resulted in reduced yield, especially when natural mortality was high.
Are we there yet?
Much remains to be learned about what influences crappie abundance and growth. High length limits can improve the size of crappie caught by anglers when populations have high growth rate and low natural mortality.
But what can be done to improve fishing for populations with low growth rate or populations where recruitment is low? How fishery biologists have attempted to tackle these and other problems will be discussed in Part II.
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