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Home > Resources & Publications > Newsletters & Magazines > Fact Sheets > Sack of Milk

Resources & Publications: Fact Sheets

by Jerald Horst

Sack of Milk is the English interpretation of “sac-a-lait”, the Cajun French name for crappie. The fish are called “white perch” in north Louisiana, but in both places they are so esteemed for their mild, sweet flesh that the Louisiana legislature has declared them the official state freshwater fish.

Actually, two species of crappie exist in Louisiana, the white crappie and the black crappie. Both are often found and caught together in the same waters, although each has specific preferences. Black crappie prefer clear, still lake or back-swamp waters. White crappie prefer the moving water of rivers and bayous and are much more common than black crappie in turbid, muddy waters. Both species tend to concentrate around some kind of cover, such as brush, fallen trees and stumps.

Black crappie are darker in color with black flecks scattered randomly on their silver sides. In white crappie, the black flecks are arranged in vertical bars. White crappie usually have 5 or 6 spines in their dorsal fins and black crappie usually have 7. The most reliable way to differentiate the two is that in the ski-jump-nosed white crappie, the distance from the tip of the nose to the front base of the dorsal fin is longer than the length of the entire base of the dorsal fin. For black crappie the lengths are equal.

Both species eat insects, insect larvae, grass and river shrimp, and any small fish. White crappie especially prey on minnows and other fish, including their own young. Crappie begin to actively spawn when water temperatures reach 61°F. This is earlier than the other members of its family, bass and bream.

Wherever they are found, crappie populations go up and down noticeably, with good catches some years, followed by years of very poor catches. In Louisiana, this cycle seems to be more noticeable in man-made lakes and reservoirs than in rivers, the Atchafalaya Basin, or in freshwater marshes. But even in these areas, a population cycle may be noted.

Scientists have found that at least two things affect these population cycles. When good conditions produce a very successful spawn, a large brood known as a dominant year class, survives. The next year, this dominant year class devours its own young, as well as other fish, and few young crappie survive. This holds true for several years, although each year fewer fish of the dominant year class exist. Finally, their numbers become so low that they cannot control the young crappie and another dominant year class develops. Few crappie live beyond age 5. The result is a couple of years of poor fishing with many small fish followed by a couple of good years. This phenomenon is especially true in ponds and small lakes under 10 acres.

Environmental conditions also affect crappie populations. Research done in Iowa indicates that water level and clarity affect the success of crappie year classes. High water levels at the time of the spawn were found to result in high numbers of larval crappie. The only exceptions to this relationship were in years of low clarity (muddy) water. Larval crappies were never found when waters were very muddy during spawning season. The biologists concluded, based on previous research, the adult crappie abandoned their nests when muddy water creates low light conditions on the bottom. They did note that actual suffocation of the eggs may also have occurred.

Changing regulations like size and creel limits may not work to stabilize crappie populations. Oklahoma biologists using predictive models have found that improving the harvest by regulation is more the exception rather than the rule for crappies. They concluded that only under conditions of fast growth and low natural death rates would management with minimum size limits improve crappie populations. Even then, anglers would have to accept decreased harvest in numbers of fish to get an increased average weight.

Biologist recommendation is to never stock crappies in ponds smaller than 10 acres. In spite of these recommendations, some pond owners stock crappie. Research done in ponds, again in Oklahoma, indicates that crappies compete with bass for food and serve as food for bass, making their management difficult. They found that the most important factor in producing good crappie fishing was a large population of bass to feed on small crappies (under 8 inches) to reduce their numbers.

In order to keep the population of bass high, the number of bass harvested by fishermen has to be kept low. High bass numbers means that few bass in the population will grow larger than 15 inches because of competition. Also, the few large bass produced should not be harvested because they are effective crappie predators.

Very few fishermen want to lower their catch of bass, and in fact most fishermen would like a pond to produce as many large bass as possible. The researchers also point out that even if bass populations are kept high, the unpredictability of crappie spawning success from year to year makes management for large crappies difficult.

The researchers concluded that trying to produce quality crappie fishing in small ponds with public access is not likely to work. They indicated that it is possible in closely managed private ponds. They also pointed out that a pond managed for productive crappie fishing would probably also produce high-quality bluegill populations.

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