Responses of oscar (Astronotus ocellatus) to different temperatures and its interaction with early mild stress

• Published in: Aquaculture Vol. 594; p. 741454
• Main Authors: Esmaeili, Noah, Zare, Mahyar, Choupani, Seyedeh Mahsa Hosseini, Kazempour, Mohammad, Hosseini, Hossein, Akhavan, Sobhan R., Salini, Michael
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.01.2025
• Subjects: Antioxidant response; Blood biochemistry; Blood performance; Heat stress; Stress physiology; Blood performance; Antioxidant response; Heat stress; Blood biochemistry; Stress physiology
• ISSN: 0044-8486
• DOI: 10.1016/j.aquaculture.2024.741454

Non-optimum temperature results in stress in fish through different biological and physiological processes. This study investigated how early mild stress (EMS) and temperature can influence growth, hematology, blood biochemistry, immunological response, antioxidant system, liver enzymes, and stress response of juvenile oscar (Astronotus ocellatus; 8.02 ± 0.81 g) before and after acute confinement stress (AC stress). Eight experimental treatments were 17D (farmed at 17 °C), 22D (farmed at 22 °C), 27D (farmed at 27 °C), 32D (farmed at 32 °C), 17DES (farmed at 17 °C and EMS), 22DES (farmed at 22 °C and EMS), 27DES (farmed at 27 °C and EMS), and 32DES (farmed at 32 °C and EMS). At the end of the experiment (nine weeks), there was no significant difference in survival rate, feed conversion ratio, body composition, and survival rate after the AC stress (ten weeks). The growth rates in the 17 and 32 °C groups were lower than others, showing the negative effect of temperature being too high or too low. After nine weeks, fish farmed at 32 °C had the highest hematological parameters (hematocrit, hemoglobin, red blood cells, and blood performance) and liver enzymes (lactate dehydrogenase, alanine transaminase, and aspartate transaminase). This group also has the lowest lysozyme, alternative complement pathway (ACH50), immunoglobulin, complement C3, complement C4, superoxide dismutase, and glutathione peroxidase. The EMS did not positively or negatively affect fish physiology in this study. In conclusion, the optimum temperature for oscar to achieve the best growth performance, immune response, and health status is 22–27 °C. •Excessive high (32 °C) or low (17 °C) temperatures decreased growth and survival of fish.•The early mild stress did not positively or negatively affect fish physiology in this study.•Fish farmed at 32 °C had the highest hematological parameters and liver enzymes.