Crawfish are best described as opportunistic eaters, that is, given the opportunity, they will eat it. This coupled with the fact that crawfish production is fairly extensive in management, crawfish are "fed" a vegetative crop that is planted and grown in the summer and flooded over in the fall. There is only 3 criteria for a good forage crop for crawfish.
One, the crop must produce 10,000 lbs. of biomass per acre. It is estimated that the feed coversion ratio for crawfish feeding on vegetative matter is about 10:1. Therefore, to have any hopes for producing 1000 lbs. of crawfish per acre per year, you will need 10,000 lbs. of vegetation in the pond prior to flooding.
Two, the crop needs to be able to withstand a flood. As fall arrives, the pond, with all of its vegetation, will be flooded to an eventual depth of 18 inches of water. The vegetation needs to be able to remain standing so as not to negatively impact the water quality. Crops such as millet typically are not good forage crops for crawfish in that they have a tendency to fall over when flooded. This causes a rapid deterioration of the water quality through the decomposition of the vegetation. The resulting depletion of dissolved oxygen in the water can cause reduced growth and death for the crawfish.
Three, the crop must have a low rate of decay. The crop must be able to persist throughout the winter and well into the spring to give the crawfish an adequate base from which to forage. A crop which is essentially depleted by early spring can cause a stunting problem for the crawfish due to a lack of food.
Research has also indicated that a persisting standing crop for vegetation is also beneficial as simply a vertical substrate for the crawfish to disperse upon. Research conducted at the Rice Research Station in Louisiana by Dr. Ray McClain indicated that crawfish yielded better if there was a vertical substrate in the pond even if that substrate had no nutritional value. In Dr. McClain's study, the crawfish raised in an enclosure with cut forage laying on the bottom of the pond and wooden dowels averaged 21% heavier than crawfish in an enclosure with just cut forage and no substrate and were the same size as crawfish raised in enclosures with a standing rice crop. Therefore, a forage crop should not be just considered as a food source for crawfish, but also as a vertical substrate for the crawfish.
Crops that are typically planted in North Carolina for crawfish are grain sorghum, or milo, sorghum sudan- grass, and rice. Many producers will plan to plant milo in June to early July, weather permitting. If the weather does not permit a producer to plant at this time, another window of opportunity will occur in mid- August with the planting of sorghum sudan-grass. Planting sorghum sudan-grass too early in the year will allow the plant to reach heights in excess of 6-8 feet and make harvesting difficult. By planting the sorghum sudan-grass in mid or even late August, the plant will only be 4-6 feet tall by the flood date. A disadvantage to sorghum sudan-grass is that it does not tolerate the excessive moisture of even a heavy rain as a seed or seedling. However, once the plant reaches a height of 2-3 feet and better, it becomes very tolerant to even being able to withstand a permenant flood. Rice is also a very good choice in that it is a semi-aquatic plant to begin with and can withstand the floods associated with crawfish culture. However, North Carolina is disadvantaged with the cost of freight to ship the seed into the state from the rice producing states.