🦞 The field that works twice

A crawfish farm is not really a building or a machine. It is a schedule for water. The LSU AgCenter puts it plainly: crawfish aquaculture relies on control of pond hydrology to simulate the wet and dry conditions that happen naturally in rivers and wetlands — the animals grow and mature during the flooded cycle and get through the dry one by digging burrows. So the farmer's main job is deciding, twice a year, when the field is a lake and when it is a field.

Basis: LSU AgCenter, “Crawfish Production: Production Systems and Forages”: “Crawfish aquaculture relies on control of pond hydrology to simulate optimal wet and dry conditions occurring in natural riverine and wetland habitats. Crawfish grow and mature during the wet or flooded cycle and survive the dry periods by digging burrows.”

The calendar is written down. In the rice-crawfish-rice rotation, the standard fact sheet gives the year as: March–April, plant rice; June, once the rice stands 8 to 10 inches deep in its permanent flood, stock 40 to 50 pounds of adult crawfish per acre; August, drain the field and harvest the rice; October, re-flood the rice field; December–April, harvest crawfish; then drain again in March–April and replant. And the crawfish's food is the crop's leftovers: after the grain comes off, the remaining stubble is fertilized, flooded and allowed to re-grow, and that second growth — the ratoon crop — is the forage base.

Basis: Southern Regional Aquaculture Center, SRAC Publication No. 241, “Crawfish Production: Production Systems and Forages” (revised October 1998; distributed by the LSU AgCenter): “Rice fields are the most readily adaptable areas for crawfish culture. The rice farmer can use the same land, equipment, pumps and farm labor that are already in place. After the grain is harvested, the remaining stubble is fertilized, flooded and allowed to re-grow. This ratoon crop is the forage base for crawfish production.” Rice-Crawfish-Rice timetable: “March - April: Plant rice. June: At permanent flood (rice 8 to 10 inches high), stock 40 to 50 pounds of adult crawfish per acre. August: Drain field and harvest rice. October: Re-flood rice field. December - April: Harvest crawfish. March - April: Drain pond and replant rice.”

That is why rice keeps turning up in the story. The LSU AgCenter's rice research station says rice plays an integral part in the farming of crawfish — either inside rice-crawfish crop rotation systems, or as the single most important forage crop, planted purely to feed the crawfish with no intention of harvesting the grain. Read that second half again: sometimes the rice is grown and never picked. It is the crawfish's dinner.

Basis: LSU AgCenter, H. Rouse Caffey Rice Research Station — Aquaculture: “Because rice plays such an integral part in the farming of crawfish, either within highly effective rice-crawfish crop rotation systems or as the single most important forage crop planted to provide a food resource for culturing crawfish with no intention of grain harvesting, this project was established as a vital component of the H. Rouse Caffey Rice Research Station in the early 1980s.”

The AgCenter names two species as the important ones in the southeastern United States: the red swamp crawfish (Procambarus clarkii) and the white river crawfish (Procambarus zonangulus). The AgCenter says culture methods are relatively simple compared with those for other aquatic animals, and that crawfish culture fits well into a farm's plans because it uses marginal lands, existing labor and farm equipment during off-peak farming periods. In other words: the ground, the tractor and the people were going to be idle anyway.

Basis: LSU AgCenter, “Pond Construction and Water Supply”: “The species of crawfish important in the southeastern United States are the red swamp crawfish (Procambarus clarkii) and the white river crawfish (Procambarus zonangulus). Culture methods are relatively simple compared to those for other aquatic animals. Crawfish culture can fit well with farm management plans because it uses marginal lands, existing labor and farm equipment during off-peak farming periods.”

Harvest does not look like fishing either. The AgCenter notes that unlike fishes, crawfish are not harvested by seining — no net dragged through the water. Instead they are taken with a passive system that uses baited traps. The farmer sets the traps, the crawfish walk in, and the field does the waiting.

Basis: LSU AgCenter, “Crawfish Production: Harvesting”: “Unlike fishes, crawfish are not harvested by seining. Instead, crawfish are harvested with a passive system that uses baited traps.”

One more reason this animal belongs here and not everywhere. The USGS gives the red swamp crawfish's native range as the Gulf coastal plain from the Florida panhandle to Mexico, plus the southern Mississippi River drainage up to Illinois. Beyond that range it shows up as a nonindigenous species, and the USGS says those United States populations likely resulted from a release from aquaculture or from the aquarium trade. Same animal: at home in a Louisiana field, an escapee somewhere else.

Basis: U.S. Geological Survey, Nonindigenous Aquatic Species database, species profile for Procambarus clarkii: “Native Range: Gulf coastal plain from the Florida panhandle to Mexico; southern Mississippi River drainage to Illinois”; “Nonnative populations in the United States are likely to have resulted as a release from aquaculture or from the aquarium trade.”