Stress relieving potential of two plant-based sedatives in the transport of juvenile tambaqui Colossoma macropomum

Abstract

The objective of this study was to investigate the effects of waxy extract of Spilanthes acmella and essential oil (EO) of Nectandra grandiflora on secondary stress responses of tambaqui Colossoma macropomum transported for up to 10 h. Fish were packed in plastic bags and shipped for 2, 6 and 10 h with or without anaesthetics added to the transport water. Whole blood was collected from the caudal vasculature before and after transport and several haematological variables were measured. No mortalities were observed after transport. Attenuation of secondary stress responses was observed with the use of N. grandiflora EO after 6 h transport based on lower glycaemia and no alteration of blood Na+ concentrations after transport compared to reference values of non-transported fish. Furthermore, dissolved oxygen levels were still maintained in the water after transport for 10 h with N. grandiflora EO compared to water of non-transported fish. While no clear advantages were observed with the use of S. acmella extract at 2 mg L−1 after transport, the use of N. grandiflora EO at 30 μL L−1 should be considered for the transport of C. macropomum for it seems to provide a sparing effect on the water dissolved oxygen levels and an improved physiological condition after transport.