Assessment of Fish Health: Seasonal Variations in Blood Parameters of the Widely Spread Mediterranean Scorpaenid Species, Scorpaena porcus

The measurement of haematological and biochemical parameters is essential for monitoring the health status of wild fish. More specifically, blood parameters provide crucial information on the physiological changes that occur in fish in response to various fluctuations in their environment. This study presents reference ranges and seasonal variations for 15 blood parameters of the black scorpionfish, Scorpaena porcus, as a species of high value for ecosystem monitoring in the Mediterranean. The mean haematocrit (HCT) values differed significantly between seasons, with the highest value recorded in winter. In addition, six plasma parameters varied significantly during the year. Cholesterol (CHOL), non-esterified fatty acids (NEFA), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and superoxide dismutase (SOD) concentrations were notably higher during the spring/summer period and at their lowest levels in autumn/winter. On the contrary, levels of glucose (GLU) were highest during autumn and lowest during the spring season. The post hoc Tukey test revealed that there were significant differences in HCT values for winter vs. spring, in CHOL for spring vs. all other seasons, in NEFA for summer vs. autumn and summer vs. spring, in GLU for spring vs. summer, in AST for autumn vs. spring, in ALP for winter vs. all other seasons and in SOD for summer vs. all other seasons (p < 0.05 in all cases). A total of nine blood parameters showed a significant relationship with fish size throughout different seasons. Our results suggest that monitoring blood parameters may serve as a useful biomarker, and we provide a reliable basis for the future monitoring of the health status of the investigated S. porcus. Considering significant seasonal variations, the use of season-specific reference ranges is recommended for this scorpaenid species.