Biofloc systems have a dense microbial community in the water column which helps maintain water quality and may act as a supplemental nutritional source for shrimp . Biofloc facilitates high levels of biosecurity , water conservation, and production of marine species inland. High tunnel greenhouses can help to extend the growing season for warm-weather crops in subtropical and temperate latitudes. H igh tunnel greenhouses have no artificial heat; they are warmed only through solar radiation , and cooled using passive ventilation and shade clothes. Varying stocking densities and substrates have shown effects on shrimp growth and performance as well as water quality. The purpose of this study was to assess these effects on production, and water quality conditions to help optimize shrimp production in high tunnels.
The experiment included 16 wooden framed tanks lined with a 45 mil rubber liner. Four tanks were located in each of four high tunnel greenhouses. Each tank contained approximately 11 m3 of water aerated with one 2.5 HP regenerative blower per high tunnel. Solids were controlled using conical bottom settling chambers and in-house made foam fractionators . Shrimp were fed a 35% protein commercial pelleted diet two times daily. Four treatments were used: high density with substrate (HD-S), high density without substrate (HD-NS), low density with substrate (LD-S), and low density without substrate (LD-NS) . High density tanks were stocked with 300 shrimp/m3, low density were stocked with 200 shrimp/m3 ; tanks with substrate contained 4. 2 m2 of polypropylene construction safety fence suspended in the water column. Each treatment was randomly assigned to one tank within each high tunnel, thereby blocking for tunnel and tank location. Shrimp were stocked after a 90 day indoor nursery period when they weighed 2.7 g, and the experiment was conducted for 101 days.
The concentrations of ammonia and nitrite were higher in the high density systems compared to low density, suggesting that some degree of caution is warranted when shrimp are grown at higher densities. Survival was significantly better in the low density treatments, but the shrimp biomass production (kg/m3) was significantly higher in the HD/S treatment compared to all other treatments. Furthermore, there was no significant difference in the mean weight of individual shrimp between any treatments.
Overall, the results of this study are encouraging for the production of marine shrimp in a land-locked, temperate location such as Kentucky using no supplemental heat. The significantly greater biomass production and the fact that density had no effect on shrimp size indicate that high density with substrate inclusion may allow production managers to optimize shrimp performance in these relatively simple systems.