Polyculture of Pacific white shrimp , Litopenaeus vannamei and r ed s wamp crawfish , Procambarus clarkii is a new production strategy being explored by commercial shrimp farmers in west Alabama. Crawfish are being produced on a pilot-scale in earthen ponds and a split pond on one commercial shrimp farm. Traditional crawfish production relies on primary productivity of the pond to fuel growth and reproduction of the crop, while low salinity shrimp culture i nvolves annual stocking and supplemental feeding . The excess nutrients generated during shrimp production may be beneficial to crawfish growth. The main area of concern is that crawfish are known to feed on sm all fish, insects, detritus, and plant material. This feeding strategy raises the question of whether crawfish would feed on juvenile shrimp, causing a negative impact on shrimp survival and production. Two controlled experiments were set up using two different systems to investigate the polyculture potential for these two species. The first experiment consisted of a 24-tank system (75 L per aquaria) with water recirculated through a sand filter, biofilter, and sump. The salinity was maintained at ~2.3 g/L using reconstituted seawater. Three treatments ( with 8 replicates), each with 20 shrimp (0.53 g mean weight) were used to evaluate the impact of crawfish presence on shrimp growth/survival : shrimp only with shrimp ration ; shrimp + 1 crawfish with shrimp/crawfish ration ; shrimp + 1 crawfish with only shrimp ration . After 21 days of rearing, shrimp were harvested and evaluated for survival and growth. The second experiment used a green water on-levee flow-through (4.9 L/min) 12-tank system (800 L per tank) at Greene Prairie Aquafarm (salinity of 2 g/L). This system had three treatments (with 4 replicates) with similar treatments, as above (each with 35 shrimp at 0.15 g mean initial weight and 4 crawfish) . The first experiment indicated crawfish presence had a significant negative effect on shrimp survival (Fig 1A). H owever, the second experiment showed no significant differences among treatments for survival and growth (Fig. 1BC) . These results indicate that although crawfish will prey on shrimp in a clear water system, the need or ability to prey on shrimp did not occur in a green water system.