Ginger essential oil as a sedative for yellowtail tetra transport: effects on water quality, gill histopathology, and fillet residues

ABSTRACT: The current study investigated the use of different concentrations of the essential oil of Zingiber officinale (EOZO) in the transport water of Astyanax lacustris by evaluating the behavioral responses of the fish, water quality, gill histopathology and residues in the fillet after transport. Four hundred juvenile A. lacustris (1.99 ± 0.72 g) were randomly distributed in 20 plastic bags, 20 fish each, with 4 L of water and 2/3 of pure oxygen. Five treatments were applied: control and four concentrations of EOZO (5, 10, 15 and 20 µL L-1), with four replicates each in a completely randomized design. The bags were sealed and shaken periodically during a simulated 2-h transport. Water quality variables were measured before and after transport, while fish survival was recorded, and gill and muscle samples were collected, at different times after transport. Gill histopathology was analyzed to detect tissue alterations and muscle (fillet) residues were quantified. The use of low concentrations of EOZO during transport of A. lacustris was effective at sedating the fish, ensuring survival. The histopathological changes observed in the gills of fish transported with 5 and 10 µL L-1 of EOZO were reversible. Furthermore, EOZO preserved water quality, with an observed reduction in ammonia levels for animals transported with 10 µL L-1. Although small histopathological changes were caused to the gills, EOZO residues in fillets were minimal and disappeared quickly (in less than 12 h). Therefore, the use of 10 µL L-1 of EOZO in the transport water of A. lacustris is recommended.