The effectiveness of eugenol in mitigating water quality, biochemical, and histopathological alterations during transportation of giant freshwater prawn juveniles

The giant freshwater prawn (Macrobrachium rosenbergii) is a high-value aquaculture commodity with increasing global demand. Adequate transportation of high-quality prawn juveniles is critical to ensuring sustainable production. Eugenol is widely known for its anesthetic characteristics. It can diminish metabolic rates and alleviate stress responses in aquatic organisms during handling and transportation. This study assessed the efficacy of eugenol, a natural anesthetic, in enhancing juvenile transport conditions by evaluating water quality, hemolymph biochemistry, histopathological alterations, and production performance. A randomized experimental design was employed with five eugenol treatments (0, 0.75, 1.87, 3.75, 5.63 mg/L) and control, combined with activated carbon and zeolite to maintain water quality during a 24-hour transport simulation. The results showed that the treatment with 1.87 mg/L eugenol yielded the best outcomes. This treatment maintained better water quality parameters, encompassing lower total ammonia nitrogen (TAN) and elevated dissolved oxygen (DO) levels compared to controls. Biochemical analysis revealed reduced stress response in juveniles, as evidenced by increased total protein, hemolymph glucose levels, high-density lipoprotein (HDL), and pH stability. Histopathological evaluation revealed minimal gill tissue hyperplasia and swift recovery post-transport from eugenol treatment. Treatment with 1.87 mg/L eugenol also achieved the highest juvenile survival rate (75.33%) at post-transportation (24 hours) and 10-day rearing. In contrast, the specific growth rate of all treatments was not significantly different. These findings underscore the potential of eugenol in enhancing the sustainability and transport efficacy of Macrobrachium rosenbergii juveniles.