The use of anesthetics in sedation and transport of juvenile white shrimp Litopenaeus vannamei
The white shrimp Litopenaeus vannamei is one of the main species produced in aquaculture worldwide. Many routine practices can generate stress and compromise the shrimp's physiological state, leading to reduced performance and survival. Anesthetic substances reduce and soothe animals, reducing metabolic costs in transport and improving handling during aquaculture procedures. Therefore, the objective of this work was to determine the induction and recovery times for juvenile L. vannamei shrimp submitted to immersion baths, in aquariums with 1L of water, in the different anesthetics: benzocaine (300, 400, 500mg L-1) , menthol (600, 800, 1000mg L-1), Citrus lemom (84, 168, 252mg L-1), Citrus sinensis (84, 168, 252mg L-1) and Eucalyptus globulus (450, 675, 900mg L-1 ). Besides that,concentrations were also evaluated for use in handling and transportation practices. In the stress test, the prawns were initially exposed to the treatments: control (pure sea water) for 5min and 252mg L-1 C. lemom or 900mg L-1 E. globulus, until they reached stage 2 of anesthesia. Then, they were exposed to air (30s) to cut the rostrum. At the end, they were transferred, randomly, to tanks (50L) with different salinities (2 or 29ppm) for survival evaluation (48h) (n = 10 shrimp / treatment / triplicate). For transportation, 120 shrimp were randomly distributed in polyethylene plastic bags with 10L of water and transported for 12 hours in the following treatments: control (sea water), ethanol, 9 and 90mg L-1 of E. globulus. At the end, the hemolymph was collected from two shrimps, by replication, for the determination of glucose.The other specimens were transferred to recovery tanks (50L) for 24 hours. Almost all anesthetics had induction times as expected (<5min), with the exception of concentrations of 700mg L-1 of menthol and 450 mg L-1 of E. globulus. The induction times for E. globulus were concentration-dependent. Benzocaine and menthol showed the longest recovery times (> 10min). The C. lemom OE resulted in a high mortality rate in the stress test for both salinities. The treatments with E. globulus showed total survival during transport and in the recovery period. Lower glucose levels were found in prawns transported in 90mg L-1 of E. globulus. In conclusion, all anesthetics were effective for sedation of L. vannamei. However,menthol is not indicated for anesthetizing white shrimp. The concentrations of 400 and 500mg L-1 of benzocaine can be indicated for long-term procedures. For induction tests, concentrations of 300mg L-1 of benzocaine, 84mg L-1 of C. sinensis, 168mg L-1 C. lemon and 450 or 900mg L-1 of E. globulus are recommended. The concentration of 90mg L-1 of E. globulus can be used to transport shrimp, as it demonstrates positive effects on water quality and on the performance of animals during and after transport.