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Essential oils beneficial to fish while in transit: study

Using essential oils to reduce stress in larva, fingerling and broodstock during transit is more ideal than utilizing synthetic compounds, according to a new report published in Frontiers in Physiology.

“Essential oils are volatile and, therefore, do not remain in the water for a long time, reducing pollution. In addition, most essential oils used are from plants that are used for seasoning food, so the fish exposed to them are supposedly not harmful for human consumption,” Dr. Juan Miguel Romero Mancera, who is with the University of Cadiz in Spain, told Hatchery International. “This aspect is essential, because the health legislation is becoming increasingly strict in the use of artificial compounds in aquaculture practice.”

Mancera and his team identified Aloysia triphylla and Lippia alba (chemotype linalool) as essential oils that could be used on most fish species.

Using essential oils on fish comes with a caution, however. “The concentrations to be used must be carefully chosen because concentrations higher than recommended for a given species may provoke stress instead of reducing it,” said Dr. Bernardo Baldisserotto, who is with the Santa Maria Federal University in Brazil.

Mancera and Baldisserotto are among the authors of “Essential Oils as Stress-Reducing Agents for Fish Aquaculture: A Review,” published in Frontiers in Physiology.

The review is the result of collaboration among different laboratories in the two universities. Completing the team are Dr. Carine de Freitas Souza, Dr. Matheus Dellaméa Baldissera and Dr. Berta Maria Heinzmann of the Santa Maria Federal University, and Dr.Juan Antonio Martos-Sitcha of the University of Cadiz.

Acclimatizing to a new aquaculture facility is already stressful enough. Coupled with being transported, Baldisserotto explained that the ensuing heightened level of stress may alter physiological and biochemical equilibrium of the fish, and sometimes can provoke death or impair immunological response.

In using essential oils during transportation, water parameters have to be observed, mainly dissolved oxygen and ammonia levels. Sedating fish with essential oil should reduce its metabolism and, consequently, its consumption of oxygen and excretion of ammonia, he said. These makes allowances for longer time in transit.

The dosage of essential oils to sedate fish is a critical factor. While the fish will have reduced activity, the sedative stage must not be so deep that it “loses swimming equilibrium to avoid hitting the walls of the transport box,” Mancera said. “Finally, we must note the need to reach the optimal dose of essential oils in order to reduce stress during transport and not to compromise correct recovery of the specimen.”