Polyculture of Pacific White Shrimp Litopenaeus vannamei (Boone) and Red Seaweed Gracilaria birdiae (Greville) under Different Densities

The present study evaluated a polyculture system with Pacific white shrimp (Litopenaeus vannamei) and the macroalga Gracilaria birdiae and its potential to remove nutrients. The experimental design consisted of a shrimp monoculture of 100 animals/m(2) (T0) and three multitrophic cultures with L. vannamei (100 animals/m(2)) and with G. birdiae at densities of 500 (T500), 1000 (T1000), and 2000 (T2000) g/m(2). Nitrogen and phosphorus concentrations decreased at the beginning of the experiment in the treatments with macroalgae, but this reduction was not maintained throughout the cultivation period. The stable values of G. birdiae biomass were perhaps related to the high turbidity of the water. There was an increase in shrimp biomass during cultivation, which reached the final individual averages of 7.5 g (T0), 7.6 g (T500), 5.9 g (T1000), and 7.5 g (T2000), with no significant differences between treatments. Nevertheless, the absence of macroalgae growth provides no added profit for the producer. Thus, there is no economic advantage in using G. birdiae in an integrated multitrophic system with L. vannamei at a high density and conditions of high water turbidity.