## 3 Results  
The _conchix_ weight within the group of mussels from Sv. Nedjelja was significantly higher in comparison with that from the IMB (\(p\) = 0.043), while significant differences between other groups, analyzed by the Mann-Whitney U test, were not observed (\(p\) > 0.05; Figure 3a). The weight of the dry shell valve in mussels from Cogi was significantly lower in comparison to that from the other two sites (\(p<0.05\)), while the differences between Sv. Nedjelja and Cogi were not significant (\(p>0.05\)). In general, a significant correlation (\(p<0.05\); \(r=0.562\)) between the _conchix_ weight and the weight of the dry shell valve within the mussels' samples from all studied sites was determined using the Spearman correlation test. The values of the condition index (CI) in mussels from Sv. Nedjelja were significantly lower in comparison with Cogi and the IMB (\(p<0.05\)), while there were no statistically significant differences between Cogi and the IMB (\(p>0.05\); Figure 3b). A statistically significant correlation between the _conchix_ weight and CI within the mussels' samples from all studied sites was not observed (\(p=0.298\); \(r=-0.085\)). _Conchix_ % in the shell valve within the group of mussels from Cogi was significantly higher in comparison with the other two sites (\(p<0.05\)), while the differences between Sv. Nedjelja and Cogi were not statistically significant (\(p>0.05\); Figure 4a). Figure 4: (**a**) _Conchix_ % in the shell valve and (**b**) correlation of _conchix_ % with a dry weight of the shell valve within the group of _M. galloprovincialis_ L. specimens sampled from Sv. Nedjelja, Cogi, and the IMB. ab—statistically significant difference (\(p<0.05\)) in comparison with the other sampling sites. Dashed lines represent confidence bands lines while the fitting line is in the middle. Statistical significance (\(p<0.05\)) was tested using the Mann–Whitney U test, while the correlation was determined by the Spearman correlation test. Figure 3: (**a**) _Conchix_ weight in the shell valve; (**b**) condition index within the group of _M. galloprovincialis_ L. specimens sampled from Sv. Nedjelja, Cogi, and the IMB; a and b—statistically significant difference (\(p<0.05\)) in intercomparison; ab—statistically significant difference (\(p<0.05\)) in comparison with the other sampling sites. *—extremes. Statistical significance was tested using the Mann–Whitney U test. Data on _conchix_ % in the shell valve from all studied groups showed a significant correlation with the CI (\(p\) = 0.044; \(r\) = 0.163) and a negative correlation (\(p\) \(<\) 0.05; \(r\) = \(-\)0.316) with the weight of the dry shell valve (Figure 4b). Table 1 presents trace metal concentrations and the MPI in four different media of _M. galloprovincialis_ L., namely shell (KS, KC, KI), soft tissue (TS, TC, TI), _conchix_ (OS, OC, OI), and shell extract (ES, EC, EI) sampled from Sv. Nedjelja (S), Cogi (C), and the IMB (I). The highest contents of Zn, Mn, and Cd were found in the soft tissues, while the highest contents of Cu, Fe, and Hg were found in the _conchixes_. Lead contents were generally highest in soft tissues with a mean value of 0.92 \(\mu\)g g\({}^{-1}\), although the highest single concentration (1.22 \(\mu\)g g\({}^{-1}\)) was found in _conchixes_ from Sv. Nedjelja. The lowest concentrations were generally found in extracts, although Pb (\(<\)0.25), Cd (\(<\)0.03), and Hg (\(<\)0.001) contents were below the detection limits in both extracts and shells, except for Pb content in the shell sample from the IMB (0.31 \(\mu\)g g\({}^{-1}\)). In addition, the lowest Fe contents were found in the shells as well. The highest MPI values were found in the soft tissues of mussels from Sv. Nedjelja, Cogi, and the IMB were 2.319, 2.711 and 2.929 \(\mu\)g g\({}^{-1}\), respectively (Table 1). The _conchixes_ from Sv. Nedjelja had higher MPI values (2.158 \(\mu\)g g\({}^{-1}\)) in comparison with Cogi and the IMB, which were 1.214 and 1.163 \(\mu\)g g\({}^{-1}\), respectively.