Indução do alimento natural através de diferentes regimes de fertilização no cultivo do camarão marinho Farfantepenaeus subtilis (Pérez-Farfante,1967)

Abstract

Marine shrimp Farfantepenaeus subtilis is found along the Brazilian northeast coast. It tolerates salinity variations and grows quickly under culture conditions. However, it has a feeding habit predominantly carnivorous, using mainly polichaets as your main feeding source. The present work aimed at to induce the natural food in the experimental culture of F. subtilis through different fertilization strategies. A randomized entirely design with three treatments and three replicates was applied, being one with inorganic fertilizer: Control (CT) - 3 mg/L of urea and 0.3 mg/L of mono ammonium phosphate; and two with organic fertilizers: Wheat bran (FT) - 25 g/m2; Soybean meal (FS) – 18.75 g/m2. Nine 500L fiber glass tanks were used, with a stocking density of 16 shrimps/m2 (≈ 2.0 g), that were fed with a 35% crude protein commercial ration at 8:00, 12:00 and 16:00 hrs. The water and plankton samples were accomplished biweekly, and benthos was monthly. During the culture the water quality maintained it self adequate to shrimp culture. The growth data showed no significant difference (P≤0.05) among the treatments, where it was verified a growth rate of 0.44 g/week and a mean survival of 75%. With relation to the natural food, the phytoplankton (921 cells/mL) was predominated by the diatoms with 86, 49 and 83%, respectively, for thetreatments CT, FT and FS. The phytobenthos was also represented by Bacilariofíceae with 88%, 66% and 78%, respectively, for CT, FT and FS. The zooplankton (9.220 individuals/L) it was represented mainly by rotifers in the treatments CT (45%), FT (38%) and FS (65%). In zoobenthos the predominance was copepods in the treatments CT (97%), FT (91%) and FS (88%). The study showed similarity among the organic and inorganic fertilizers, indicating that the fertilization process was not efficient to supply enough natural food organisms, but it was observed that the three protocols applied were similar in terms of the F. subtilis shrimps growth and maintenance of water quality.