Performance of Pacific white shrimp Litopenaeus vannamei raised in biofloc systems with varying levels of light exposure

Most research on biofloc systems has been performed in greenhouses with abundant natural light. The functionality of these systems in an environment devoid of light remains poorly understood, especially with regard to growth and survival of reared animals. This study evaluated the performance of Litopenaeus vannamei reared in a biofloc system with varying levels of light. Treatments were 24 h with light (24WL), 12 h with light/12 h without light (12WL/12WOL), and 24 h without light (24WOL), each with four replicate tanks. The 24WL and 12WL/12WOL treatments were supplied with light intensity of 10000 lx. Shrimp with mean +/- SD initial weight of 3.3 +/- 0.1 g were reared in 850 L-tanks at a density of 300 shrimp m(-3). With the exception of nitrate, TSS, VSS and chlorophyll a, there were no significant differences (P > 0.05) in water quality parameters among treatments. Nitrate was higher (P < 0.05) in 24WOL treatment than in 24WL but neither was significantly different from 12WL/12WOL. TSS and VSS were higher (P < 0.05) in 24WL treatment than 24WOL, but were not significantly different from 12WL/12WOL treatment. Chlorophyll a was higher (P < 0.05) in 24WL treatment than in 12WL/12WOL and 24WOL treatments. There were no significant differences (P > 0.05) in shrimp survival and feed conversion ratios among the treatments. However, shrimp in 24WL treatment grew at a significantly greater rate and reached a significantly greater final weight than shrimp in 24WOL treatment (P < 0.05), but neither was significantly different from 12WL/12WOL. The results demonstrate that shrimp production was higher in the treatment that were exposed to light; however Pacific white shrimp can be raised in total absence of light with acceptable performance. (C) 2012 Elsevier B.V. All rights reserved.