Physiological changes in juvenile tambaquis (Colossoma macropomum) transported using essential oil of Ocimum gratissimum

Essential oils may be used as natural anesthetic for fish in several farming and laboratory procedures. They are considered safe for both the fish and the environment. In this way, studies that evaluate essential oils as fish stress reducers are necessary to confirm such recommendations. Transportation is one of the most stressful fish farming practices, since fish are severely disturbed. Stress among fish may induce undesired consequences such as diseases and mortality. This study evaluated the effect of Ocimum gratissimum essential oil on the physiological parameters of stress in Colossoma macropomum subjected to transportation. Fish were transported in plastic bags under different concentrations of O. gratissimum essential oil (0, 5, 10, 15 and 20 mg L-1) for 4 h. Blood samples were collected before and after transportation. Glucose and ammonia levels increased and lactate levels decreased after transportation with O. gratissimum essential oil in the water. The total plasmatic protein and hepatic glycogen levels presented great variations, while hematological parameters did not show any difference between treatments. The fish recovered from transportation stress after 24 h. The concentrations of O. gratissimum essential oil evaluated here were not efficient in mitigating the stress responses of C. macropomum. Additional studies are needed to evaluate effective concentrations of O. gratissimum that would reduce stress responses in transportation, along with their associations with other products and procedures.