Toxicity of nitrite on shrimp Litopenaeus vannamei reared in clear water and biofloc systems

Abstract

This work aimed to evaluate the toxicity of N-nitrite on growth, survival and the amount of total hemocytes in the hemolymph of the shrimp juveniles Litopenaeus vannamei (1.60±0.06 g) reared in different concentrations of N-nitrite and two culture systems. The shrimps were distributed into 24 experimental units (area of 0.20 m² and useful volume of 30 L) at a density of 75 shrimp m-² in a completely randomized design with 2x2 factorial scheme, using four nitrite-N concentrations (0í Control, 10, 20 and 40 mg NO₂-N L^-1) and two culture systems (clear water and biofloc). Juveniles of L. vannamei were fed with commercial feed (35% crude protein). The NO₂-N concentrations influenced significantly (P<0.05) body weight (1.71 to 3.36 g), survival (40.7 to 96.3%) and specific growth rate (0.15 to 2.42% day^-1). The interaction between the N-nitrite concentrations and culture systems did not affect significantly (Pâ"°¥0.05) the total amount of hemocytes. Thus, it is possible to culture the L. vannamei shrimp at concentrations of 10 and 20 mg N-NO₂ L^-1 for a period of 30 days without compromising growth and survival.