Crawfish aquaculture is based on management practices that mimic hydrological and vegetative cycles in natural habitats. Natural reproduction is relied upon as a source of hatchlings each farming season. Rainfall and temperature extremes throughout the year can significantly impact production.
Spring
Newly established crawfish ponds and many rice fields — some 70% of Louisiana’s crawfish aquaculture is conducted in rotation with rice production — are partially flooded and stocked in the spring with mature adult crawfish. Soon after stocking, the crawfish burrow along the levees to reach wet, saturated soil below the surface. Then they plaster and seal their burrows from the inside to trap and conserve water for the months ahead. Burrow openings are typically sealed with plugs of clay soil that soon become very hard. These plugs require significant rainfall to soften them enough for crawfish to leave their burrows. In permanent ponds used only for crawfish production, burrowing is most common in the spring as water temperatures rise. Mild temperatures and frequent rainfall improve burrowing success.
Summer
As summer progresses in ponds with rice rotation, rice is harvested for grain and the stubble begins to regrow. Alternately, in crawfish-only management, a forage crop of late-planted rice or natural vegetation is cultivated. In either case, this takes place while the crawfish pass the summer months sealed in their burrows. Very low oxygen is typical in burrows, and high temperatures can worsen these conditions. While still in their burrows, a few female crawfish begin to lay eggs as early as late August. Water must be present in the burrow for successful egg laying, so regular rainfall is important over the summer to maintain some soil moisture and keep the pond banks from cracking. Soil types with limited clay content, or soil with very high clay content that cracks when dry, also may limit crawfish survival while in burrows. AgCenter research published in 2004 confirmed that 71% of the variability in crawfish crops from 1993 to 2002 could be explained by precipitation levels at three locations in Louisiana’s crawfish-producing region.
Under drought conditions, if the surrounding soil cracks and allows outside air to enter a crawfish’s burrow, the water inside will evaporate and the crawfish will die. In the 1990s, AgCenter researchers excavated more than 100 crawfish burrows and found dead crawfish only in burrows with no remaining water. They indicated that dry summer conditions can result in a significant reduction in crawfish populations. Permanent ponds (managed solely for crawfish year after year) appear to be more resilient to drought conditions than those in rotation with rice.
Fall
Egg laying reaches a peak in early October. Normally, a female crawfish’s eggs hatch while she is still in her burrow and the young remain attached to, or clinging to, her tail until she eventually emerges. Ponds and rice fields are typically flooded from late September through late October to create a suitable environment for newly hatched crawfish. During this period, heavy rainfall events prompt females with eggs or hatchlings to leave their burrows, as their plugs become soft enough to push open. Across the crawfish producing region, folks know “the mama crawfish don’t come out until they hear the thunder.”
In a study published in 2000, AgCenter researchers observed strong relationships between crawfish emergence (with eggs or young) and rainfall events, even in ponds that were not yet flooded. They concluded that lengthy periods of low (or no) rain in the fall may be problematic because large percentages of crawfish carrying their young emerge only after sufficient rain. On the other hand, from late August through mid-October, heavy rains associated with tropical storms and hurricanes can force females to emerge from their burrows too early, especially if they are temporarily submerged under the storm water. Many crawfish producers have learned over the years that holding stormwater in an attempt to save these animals is usually not a good idea, especially in hot weather. Losing some crawfish that emerge early does not hurt the crop as much as holding deep, rancid water with little or no oxygen.
Winter
After ponds or fields are flooded in the fall, the rice stubble or other vegetation that grew during the summer begins a gradual breakdown process, supporting a natural food web that can typically produce between 350 and 900 pounds of harvestable crawfish per acre over the following seven to eight months. Depending on several factors, mainly temperature and dissolved oxygen levels, hatchlings will grow to marketable size in eight to 16 weeks, with peak harvests from March through May. Freezing temperatures rarely kill crawfish; they simply wait for the water to warm up so they can start moving and growing again. However, harsh winter conditions often eliminate any vegetation remaining above the water surface, significantly reducing food resources for the remainder of the season.
Summary
Weather patterns throughout the year impact crawfish aquaculture in Louisiana. A recent analysis of eight years of harvest data from six ponds at the AgCenter Aquaculture Research Station indicated that, across all years, precipitation levels in October and November had a statistically significant positive effect on monthly crawfish harvests in pounds per trap. Of note is the finding that the number of hours at or below freezing one or two months prior to harvest had a statistically significant negative impact on harvests. Fall precipitation levels impacted harvests throughout the rest of the season. Clearly, Louisiana’s crawfish industry is at the mercy of Mother Nature like any other agricultural commodity.
C. Greg Lutz is a professor and specialist in the School of Renewable Natural Resources.
This article appeared in the spring 2024 edition of Louisiana Agriculture magazine.
In rice-crawfish rotation, mature crawfish are stocked in the spring to produce the next season’s crop. AgCenter file photo
Rice-Crawfish-Fallow Rotation
In this production strategy, rice is not cultivated in the same field during consecutive years. This aids in the control of rice diseases and weeds for maximum rice yields. Crawfish are stocked into stands of young, growing rice in the late spring or early summer with the crawfish crop following the rice cultivation period.
Between the end of the crawfish season (typically June) and the planting of the next rice crop (typically the following March or April) the land is fallow. As a result, a field in this rotation strategy requires stocking every other year to reestablish the crawfish population. The most recent survey of Louisiana crawfish producers indicates some 70% of farmed crawfish are produced in rotation with rice crops.
2024 Crawfish Season Update
Following the prolonged drought conditions experienced in 2023, crawfish harvests had risen to roughly 25% of what could be considered normal as of early April 2024. However, total production prior to March was only 5% to 10% of the typical amount.
As young crawfish that entered ponds after widespread rains in early December finally reached harvestable size, prices had begun to drop. But most producers and industry observers agree that prices were barely enough (and in some cases not quite enough) to cover costs associated with harvesting.
Another problem will be facing many crawfish producers by June. Crawfish populations will have to be reestablished in ponds that were not in production this season due to saltwater intrusion or lack of water altogether. Crawfish will also be needed to stock the roughly 180,000 acres that would normally be in rice-crawfish rotation.