Aquaculture America 2023

February 23 - 26, 2023

New Orleans, Louisiana USA


 Mahala Gambill*, Mark G. Shirley, John  J. Sonnier


Louisiana State University AgCenter

8026 Mai n Street, Suite 402, Houma, LA 70360


 Crawfish producers in south Louisiana create a suitable  wetland habitat for crawfish to survive, reproduce and grow to harvest size.

These s hallow water impoundments are used for both crawfish and rice production. In fields where a crawfish crop follows a rice crop, it is the stubble, harvest debris (straw) and ratoon rice growth that create the food web for the duration of the crawfish season.

 Rice is typically planted in March or April for harvest in July or August.  When the rice is harvested, several thousand kilograms of straw per hectare is left scattered in the field.  If  fertilized and  reflooded, the ratoon growth will result in several thousand  more  kilograms  per hectare of live biomass in the pond by October when ponds are flooded deeper  for crawfish production . The live biomass has very low Biological Oxygen Demand (BOD), but the dead stubble and straw have a very high BOD in water .  This can result in hypoxic  water conditions in the pond during the fall, and reduce  crawfish survival, and retard growth.  Hypoxic conditions require frequent flushing of the pond at considerable expense.

 The persistence of the live and dead biomass contributes to the food web that crawfish need throughout the season. Most of the dead stubble and straw decomposes over the winter with little persisting into the spring. The ratoon growth will eventually die during the winter but will persist  in the colder water later into the spring.

 Four different stubble management schemes were evaluated at the LSU AgCenter Rice Research Station in Crowley, LA during the 2021-2022 crawfish season. A one-way analysis of variance (ANOVA) was performed to assess the effect of common post-harvest management methods on crawfish food supply during the season.  The treatments included bushhogging the stubble, rolling the stubble, burning the straw off the top of the stubble and the control was scattering the straw and not manipulating the stubble in any way.  In addition, fertilizer was added to one set of treatments and not to the other set. Total biomass was measured in each treatment monthly from October 2021 to May 2022. Overall, there was no significant difference between the stubble treatments. The only significant difference was  due to the addition of fertilizer after the  rice crop was harvested. The results of this study suggest that crawfish farmers should consider applying fertilizer to the stubble rather than spending time and resources on manipulating the stubble vegetation.