The objective of this study was to evaluate the effects and interactions of stocking density and light
level on the growth and survival of Litopenaeus vannamei in zero-exchange mixed biofloc systems. The
necessity of light and its effects on stocking density could provide essential information for efficient
system design in temperate regions. Twelve, 3800-L conical-bottom tanks housed in a greenhouse
were filled with dechlorinated city water, adjusted to 25 ppt salinity, inoculated with mixed biofloc
communities, and randomly assigned to one of four different treatment combinations. The study was
a 2 × 2 factorial arrangement with main effects being stocking density (182 shrimp/m2 [low density;
LD] vs. 364 shrimp/m2 [high density; HD]) and light (natural light [NL] vs. low level artificial [LL])
with three replicate tanks per treatment. Tanks in the NL treatment received ambient greenhouse
light. For the LL treatment black plastic was used to block NL and a single 60-W incandescent
bulb was hung over each low-light tank and operated on a 12:12 h schedule. Juvenile L. vannamei
(0.40 ± 0.28 g) were stocked in rotation into each tank and fed a 35% protein diet twice daily at
an initial 10% of body weight, gradually decreasing to 3% of body weight prior to harvest. After
12 wk, there was a statistically significant (P ≤ 0.05) interaction between density and light level;
therefore, data were analyzed in terms of treatment combinations. Average harvest weight of shrimp
was significantly higher (P ≤ 0.05) in the LD/NL treatment (14.5 g) than in the HD/LL treatment
(12.4 g), but neither was significantly different from HD/NL (13.6 g) and LD/LL (13.4 g). Survival
of shrimp was significantly lower (P ≤ 0.05) in the HD/LL treatment (61.8%) than in the LD/NL
(89.8%) and LD/LL (89.0%) treatments. Survival in the HD/NL treatment (82.7%) was intermediate
and not significantly different (P > 0.05) from the other treatments. Harvest yield was significantly
greater (P ≤ 0.05) in the HD/NL treatment (4.1 kg/m2) than in the LD/NL, LD/LL, and HD/LL
treatments (2.4, 2.2, and 2.8 kg/m2, respectively), which were not significantly different (P > 0.05)
from each other. These data indicate that a combination of high stocking rate with high light levels or
NL may be needed to achieve maximum production; however, relatively low levels of artificial light
may be suitable at low stocking densities. Further research should investigate the type and amount
of light needed to achieve optimal results.