## 4 Discussion  
This study provides the first comprehensive data on haematological and biochemical reference values for _S. porcus_ in the Adriatic Sea, and even in the entire Mediterranean, and is a valuable step towards using these parameters for the health monitoring of the investigated species. The analysed blood parameters covered a wide range of biological functions and metabolic processes, including the stress response (e.g., HCT), nutritional status (e.g., TP, CHOL, TRIG, NEFA and GLU), organ function (e.g., AST and ALP) and antioxidant defence system (e.g., GPx and SOD). Studies of blood parameters have proven to be a good approach for analysing fish health status. It is therefore not surprising that there has been a growing interest in such studies in recent years [23; 24]. Most results showed that the baseline values of blood parameters are species-specific and were affected by numerous endogenous and exogenous factors, such as water temperature, food, and the age and sex of the fish [23]. The present study demonstrated the temporal variation in both the haematological and biochemical parameters of _S. porcus_, with non-significant alterations with respect to sex. Specifically, seven blood parameters showed significant seasonal differences, and while the values of CHOL, NEFA, AST, ALP and SOD were significantly higher during the warmer period (spring/summer), the levels of HCT and GLU were highest during colder seasons (autumn/winter). Elevated water temperatures during the spring and summer lead to an increase in fish metabolic rate; however, it should be emphasised that seasons in which most of the parameters increased (spring and summer) correspond to the spawning period of the investigated species (May-September) [25]. CHOL, NEFA and GLU, as contributors to the observed variations between seasons in _S. porcus_, can yield information about the fish nutritional status. Seasonal variation in the lipid profile analysis revealed that two fractions (CHOL and TRIG) were the highest in spring, probably in relation to the food availability and the feeding rate. Similar results were also reported in the past for other fish species in the Mediterranean and other areas [26; 27; 28]. On the other hand, it should be emphasised that the mean values of CHOL and TRIG for _S. porcus_ throughout the year are lower than those reported for some Mediterranean species: _Oblada melanura_[11], _Scylhorithus canicula_[27], _Sparus aurata_[29] and mullets [30]. The only similarity was noted with the wild _Dicentrachus labrax_ from the northern Adriatic Sea, whose TRIG values were 0.67 mmol/L [31]. The most metabolically active lipid form in the blood is NEFA, and it is indicative of the extent to which fish rely on lipid as a fuel [32]. However, as NEFA plasma levels are also affected by spawning in a way that causes concentrations to increase during this process, we believe that this is precisely the reason for the increased NEFA in _S. porcus_ during the summertime. This peak associated with spawning is linked with gametogenesis and reflects the mobilisation of lipid reserves required for the development of gonads [33]. Seasonal variation in the blood GLU concentrations revealed a pattern different to that observed for the lipid profile parameters. Even though GLU is accepted as an indicator of fish nutritional status, this parameter is highly responsive to stressors, so its variations in the blood are more likely to be associated with other stress indices than with nutritional status [34]. In addition, in contrast to the results of the present study, _S. porcus_ captured in the Dardanelles had the highest and the lowest GLU levels in spring and autumn, respectively [17]. These differences could be related to the sampling area and specific local conditions. In general, GLU concentrations vary considerably between species, which can be confirmed by a comparison with the results of research on blood parameters in other Mediterranean fish species.