POLYCULTURE OF PACIFIC WHITE SHRIMP Litopenaeus vannamei AND JUVENILE TILAPIA Oreochromis niloticus IN INDOOR BIOFLOC AQUACULTURE SYSTEMS

Biofloc aquaculture systems contain a dense community of microorganisms in the water column which is responsible for maintaining water quality and can provide supplemental feed for animals.  These systems use very little water and allow for bio-secure, inland production of marine animals, as salt can be conserved.  Shrimp and tilapia have very similar environmental tolerances, making them good candidates for polyculture.  Producing two animal crops may allow farmers to diversify production and maximize the utilization of resources. This study examined the effects of adding juvenile tilapia (O. niloticus) to biofloc shrimp (L. vannamei) production systems; we examined water quality and animal production dynamics.

Eight pairs of two tanks were used with one tank in each pair raised above the other.  Shrimp were stocked in all eight of the raised tanks while only four of the lower tanks were stocked with tilapia, creating two treatments: Shrimp only (SO) and Shrimp with Tilapia (ST)  Water was constantly pumped between each pair of tanks with a screen preventing transfer of feed.  Shrimp were fed a commercial diet while tilapia were not fed directly; they were left to consume biofloc particles in the water column. All shrimp tanks received the same amount of feed.  Water quality parameters were measured routinely and the study lasted 76 days.  

Nitrite, nitrate, and turbidity were all significantly higher (P < 0.05) in the ST treatment compared to SO.  There were no significant differences between the two treatments regarding shrimp production.  However, the total animal biomass produced was significantly greater in the ST treatment.  Likewise, the total feed conversion ratio considering feed inputs and all biomass gained, was significantly lower in the ST treatment.

The results of this study indicate that significantly more biomass can be harvested in a polyculture system with the same nutrient inputs.  Producers may have opportunities to operate tilapia nursery systems concurrently with shrimp biofloc production systems, thereby increasing total output.  However, the burden of extra biomass on water quality needs to be considered.