Anesthesia and transport of juveniles of Mugil liza mullet

Author: Reinaldo da Silva Braz  (Currículo Lattes)
Supervisor: Dr Ricardo Vieira Rodrigues


Mugil liza mullet is a species of marine fish that has shown potential for aquaculture and has been studied with the purpose of developing its technological production package. However, there are no studies reporting the use of anesthetics for the species. One of the main characteristics of this species is the fact that it is eurialina, being able to be created in fresh water being an alternative for production far from the coast. However, there is no information on the transport of M. liza. Therefore, the first study aimed to determine the efficient concentrations of four anesthetics in juvenile mullet. The fish (6.9 ± 1.4 g) were individually exposed (N = 10 per concentration) to four concentrations of benzocaine (30, 40, 50 and 60 mg L-1), MS-222 (100, 125, 150 and 175 mg L-111), eugenol (50, 70, 90 and 110 mg L-1) and menthol (175, 200,225 and 250 mg L-112). The evaluation of the best concentrations was performed based on the maximum time range of anesthesia (3 minutes) and recovery (5 minutes). The most efficient concentrations found for anesthetics were: Benzocaine 50 mg L-1, MS-222 150 mg L-1, eugenol 70 mg L-1 15 and menthol 225 mg L-116. The second study aimed to transport juvenile mullet in different salinities. To carry out the experiment, the fish were transported in 18 bags with 10 L of water and 20 L of oxygen each. The fish (1.6 ± g and 5.2 ± 0.7 cm) were stored with a density of 27 g L-119. Afterwards, they were transported for 24 h in 3 salinities: 5 (low salinity), 13 (close to the isosmotic point) and 35 (typically marine salinity). At each salinity tested,3 bags contained buffer (1g NaHCO3 per liter of water), and 3 bags without the addition of buffer. It was observed that in treatments with the addition of NaHCO3, the pH values ​​suffered a lower reduction compared to treatments without the addition of buffer. In spite of this, in treatments with low salinity (5 and 13) an increase in the values ​​of carbon dioxide in the water was verified. The animals' survival was significantly affected by the addition of NaHCO3 in transport at salinities 5 and 13. Therefore, it is recommended to use 1 g NaHCO3 L-1 28 per liter of water for transporting M. liza only when carried out in salinity 35, not the use of this buffer is indicated for the transport of juveniles of this species in low salinities.