Interactive Effects of Temperature and Soybean Meal‐Based Diets on the Physiological Status of Juvenile Totoaba macdonaldi : Growth and Blood Parameters

Growth and haematological parameters are used in aquaculture as indicators of the health of cultivated fish in response to changes in diet and the physicochemical conditions of the water. In this study, the physiological status of Totoaba macdonaldi was evaluated based on growth, haematological parameters and blood chemistry in response to two temperatures (23°C and 26°C) and the partial replacement of fishmeal with soybean meal (SBM—32%, 43% and 56%). In total, 288 fish were distributed among a control group and treatments in a 2 × 4 experimental design with three replicates. The diet was provided to apparent satiety three times a day for 61 days. Temperature significantly affected the final average weight of the fish acclimated to 23°C or 26°C ( p < 0.05). The highest final average weight (264.2 ± 7.9 g) was recorded in fish acclimated to 26°C and fed a diet with 43% SBM, and the Fulton condition index ranged from 0.98 ± 0.01 to 1.05 ± 0.12. The albumin and aminotransferase enzyme concentrations and the albumin:globulin ratio were affected by the acclimation temperature ( p < 0.05). The temperature–diet interaction affected the concentrations of leukocytes, albumin and triglycerides. Diets containing SBM significantly affected ( p < 0.05) the concentrations of leukocytes, total proteins, albumin, globulins, glucose, triglycerides, aspartate and alanine aminotransferases, as well as the albumin:globulin ratio. Increases in these indicators were observed in fish fed diets with higher percentages of SBM. The results show that replacing fish meal with more than 32% SBM could negatively affect health‐related blood parameters in T. macdonaldi , with more pronounced effects when a diet–temperature interaction is present. These findings highlight the need for further research to evaluate the use of SBM in T. macdonaldi diets and its effect on their physiological performance under different thermal conditions.