Effects of thermal stress responses in goldfish (Carassius auratus): Growth performance, total carotenoids and coloration, hematology, liver histology, and critical thermal maximum

Abstract

The present study aimed to investigate the effect of thermal stress on growth, feed utilization, coloration, hematology, liver histology, and critical thermal maximum (CTmax) in goldfish (Carassius auratus) cultured at three different acclimation temperatures including 27˚C, 30˚C, and 34˚C for 10 weeks. Goldfish were assigned randomly to tanks with a quadruplicate setup, accommodating 20 fish per tank. Fish were manually fed four times a day until satiation. The result showed that fish acclimated at 34˚C exhibited suppress growth indices and significantly decreased feed utilization with linear and quadratic effects on feed efficiency ratio and protein efficiency ratio. The coloration parameter (a* value) was significantly decreased in the trunk region and total serum carotenoids at week 5, as well as a decline in L*, a*, b* values and total serum carotenoids at week 10. Total carotenoid contents in muscle and skin also decreased with increasing temperature. Aspartate aminotransferase, alanine aminotransferase, and triglycerides significantly increased with increasing temperature. However, high-density lipoprotein cholesterol decreased linearly and quadratically. Glucose and cortisol levels linearly increased with increasing temperature with a quadratic effect observed only in glucose levels. Liver histology showed swollen hepatocytes, nuclei displacement, and infiltration of inflammation in fish cultured at 34˚C. Goldfish exposed to a temperature of 34˚C displayed a higher CTmax of 43.83˚C compared to the other groups. Taken together, increasing temperature slightly improves growth (up to 30˚C) but the temperature at 34˚C significantly suppresses feed utilization, coloration as well as stress response with liver histological damage in goldfish.