GROW OUT OF THE LITOPENAEUS VANNAMEI IN MICROCOSMS FERTILIZED WITH WHEAT BRAN WITHOUT WATER EXCHANGE

摘要

The aim of this study was to analyze the influence of organic fertilizer with the purpose of costs and effluents reduction in the marine shrimp Litopenaeus vannamei culture through two fertilization regimes: 1) CT (control treatment) -inorganic fertilizers (urea, monoammonium phosphate and sodium silicate), and 2) WT (wheat treatment) - organic fertilizer (wheat bran). Experimental tanks consisted of fiberglass with estuarine sediment in the bottom and 25 ppt water. After initial fertilization the tanks were stocked with 40 2.5 g juveniies/m~2 and maintained with aeration during 88 culture days. Shrimps were fed with a 35 percent crude protein commercial pelleted ration through feeding trays, three times per day and adjusted according to daily consumption. Water temperature, dissolved oxygen and pH were measured daily; the transparency and salinity were checked weekly and water samples of each tank were collected biweekly for nutrients analyses. Dissolved oxygen levels were higher in the wheat bran(6.16 ± 0.98 mg/l) than with the inorganic fertilizers (5.92 ± 1.19 mg/l). Different feed conversion ratios were observed along the experiment (1.3 and 2.1), justifying periodic adjustments of the amount of artificial diets. The shrimp's survival wasthe same for both fertilization regimes (96.6 percent). The final weight in CT was 11.89 ± 1.73 g and in WT was 12.28 ± 1.71 g, with lower cost of the wheat bran in relation to the inorganic fertilizers. The wheat bran showed good results both in the maintenance of water quality without exchange and the performance of the shrimps.