Planktonic and bentonic responses to different fertilizations in the Farfantepenaeus subtilis (Pérez-Farfante, 1967) shrimp culture

Abstract

This work aimed to evaluate the natural food induction in Farfantepenaeus subtilis culture, through different fertilization regimes. Twelve 500 L fiber glass tanks were stocked with 30 shrimps.m^-2 (2.57 ± 1.27 g). Four experimental treatments were adopted in triplicate, using the three organic fertilizers: wheat bran í  FT (28 g.m^-2), rice bran í  FA (28 g.m^-2) and molasses í  ML (40 mL.m^-2), and one control í  CT, with inorganic fertilizers (2 mg.L^-1 nitrogen and 0.2 mg.L^-1 phosphorus). Artificial feed was offered in feeding trays three times a day, and plankton, benthos and water samples were collected fortnightly. Results showed no significant difference (Pâ"°¥0.05) in survival among the organic fertilizers treatments, but showed statistical difference (P<0.05) between FT and CT. About the natural food organisms, there was no significant difference (Pâ"°¥0.05) among planktonic groups. In the phytoplankton, there was predominance of Cyanophyta, while in the zooplankton the major representants were rotifers. In the benthos, Cyanophyta also represented the phytobenthos, but there was statistical difference (P<0.05) only in Euglena group, in which FA was different (P<0.05) from FT and CT. In the zoobenthos it was registered the predominance of rotifers and nematodes, showing significant difference (P<0.05) in rotifers group in ML, when compared with CT and FT. Nematodes differed (P<0.05) in FA when related to FT and ML, which also predominated in mesobenthos, with no significant difference (Pâ"°¥0.05) among the treatments. It was concluded that in the experimental conditions adopted, both organic and inorganic fertilizers effects were similar related to natural food induction.