Myrcene as water conditioner, stress-reducing and antioxidant agent in transportation of common carp, Cyprinus carpio, with plastic bags

This study aimed at evaluating the efficacy of myrcene on water quality and stress responses of common carp, Cyprinus carpio, during transportation. A total of 126 fish (45.3 ± 1.65 g) were transported using 0, 10, 20, 30, and 50 µL/L myrcene for 6 h. All transported treatments exhibited significant decrease in water pH, dissolved oxygen, and increase in water temperature and ammonia. Myrcene had no effects on water pH and temperature after transportation, but 10 µL/L myrcene significantly decreased water dissolved oxygen, as 30 µL/L myrcene increased it, compared to the fish transported without myrcene. Moreover, 20–50 µL/L myrcene significantly decreased water ammonia, compared to the fish transported without myrcene. Transportation induced significant increases in water alkalinity in 0–30 µL/L myrcene and the highest alkalinity was related to 10 µL/L myrcene. Plasma ammonia significantly increased in all treatments after transportation and the lowest and highest levels were observed in fish transported with 20 and 50 µL/L myrcene. Plasma lactate significantly decreased in fish transported with 0–30 µL/L myrcene; but increased in fish transported with 50 µL/L myrcene. All transported fish showed similar plasma T4 levels, which were significantly lower than the before transportation. Transportation induced significant increase in plasma cortisol, glucose, superoxide dismutase, catalase, malondialdehyde and significant decrease in plasma T3, which 10 µL/L myrcene failed to mitigate such change, and nevertheless, 20 and 30 µL/L myrcene mitigated such changes. 50 µL/L myrcene led to higher cortisol, glucose, CAT, MDA, and lower T3 and GSH, compared to fish transported without myrcene. Plasma glutathione peroxidase activity significantly decreased in fish transported with 50 µL/L myrcene, compared to fish not transported. Myrcene is recommended as a sedative and stress-reducing agent in common carp transportation procedures. The beneficial concentration is 20–30 µL/L, but lower and higher concentrations have negative effects.