Usefulness of clustering blood biochemical markers to assess thermal stress and acclimation in red seabream, Pagrus major

Abstract

Temperature is a pivotal key in fish physiology but is limited in determining blood bone biomarker as a stressor. In this study, fourteen blood biochemical markers were evaluated by employing clinical blood test methods to identify the causation between temperature and the levels of sensitivity for the given temperature in a red sea bream, Pagrus major. The survival rate of 2-year-old P. major decreased below 10 °C. The physiological biomarkers could be categorized into four clusters based on their level-changing patterns. Cluster 1 included the factors that did not change by temperature. Cluster 2 significantly changed at cold temperature including direct bilirubin (≤ 6 °C), cortisol (≤ 8 °C), albumin (≤ 8 °C), and total cholesterol (≤ 8 °C), and free T3 and aspartate aminotransferase (≤10 °C). Total bilirubin, which is classified as cluster 3, significantly changed at both cold (≤ 8 °C) and high temperature (28–30 °C). Cluster 4 comprised total protein, glucose, lactate, and IL-8, which significantly responded to both low temperature (≤ 15 °C) and high temperature (28–30 °C). These results suggest that some physiological diagnostic biomarkers have temperature specific blood levels, so classifying them by their sensitivity and tracing them with clusters are useful to evaluate stress or stressors in P. major. In addition, the markers belonging to clusters 2, 3, and 4 were more sensitive to acclimated temperature, therefore, clustering and comparing them might be very useful for the case of P. major health and environmental monitoring programs.