## 4 Discussion  
To our knowledge, this is the first study that investigated the mercury content in red mullet from the Adriatic Sea, in relation to some biological parameters, sampling area, and human health risk assessment. In the present study, THg content was similar to the findings of previous studies that were carried out in the Mediterranean Sea [17, 18, 19, 20, 21, 22, 24, 25]. Generally, in comparison with previous research carried out in the Adriatic Sea, this study showed similar Hg values to those recorded by [PERSON] et al. (2017) [34], [PERSON] et al. (2012) [23], and [PERSON] et al. (2020) [19], whereas other studies recorded greater Hg concentrations [17, 25]. Our results were also similar to those found for the Gulf of Lions [24]. Additionally, specimens from Sicily and the Spanish fish market recorded similar Hg values [21, 22]. However, mercury concentration in the central Tyrrhenian was higher in comparison with our findings [34] (Table 3). Almost all previous studies focused on Hg and other metal content in different biological tissues of _M. barbatus_ only in relation to biometric indexes, without considering any important parameters such as habitats of this species, the reproductive stage, or the \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Principal Components**} \\ \cline{2-3}  & **1** & **2** \\ \hline Variance explained & & \\ Eigenvalues & 2.6673 & 1.0828 \\ \% of variance & 66.683 & 27.070 \\ Cumulative \% & 66.683 & 93.754 \\ \hline Factor loadings & & \\ Length & 0.5990 & 0.0387 \\ Weight & 0.5985 & 0.0127 \\ Hg & 0.2571 & 0.8452 \\ Lipid & 0.4657 & \(-\)0.5328 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Principal component analysis. Eigenvalues, explained and cumulative variance, loadings of the variables for the first two PCs. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sampling Area**} & \multirow{2}{*}{\(n\)} & **Total Length, cm** & **THg, mg kg\({}^{-1}\)ww** & \multirow{2}{*}{**Reference**} \\  & & **(Weight, g)** & **(Min–Max)** & \\ \hline Adriatic Sea & 407 & 10–17 & 0.20 \(\pm\) 0.15 & \\ Adriatic Sea & (16 pool) & (9–49) & (0.03–0.62) & \\ Adriatic Sea & & & (0.08–1.74) & [17] \\ Central Adriatic Sea & 14 & 13.75 \(\pm\) 0.44 & 0.48 \(\pm\) 0.9 & [25] \\  & & 9.4–15.5 & & \\ Eastern Adriatic Sea & 60 & (10–62) & (0.178–0.996) & [19] \\ Central Adriatic Sea & 25 & \(15\pm\) 0.4 & & \\ Central Tyrrhenian & & (37 \(\pm\) 5) & 0.236 \(\pm\) 0.102 & [34] \\ Sea & 58 & \(18\pm\) 2 & & \\ Spanish market & 20 & (73 \(\pm\) 29) & 0.702 \(\pm\)0.834 & [34] \\ Gulf of Lions & 132 & 8.5–24.5 & & (0.044–1.96) & [22] \\ Sicily & 48 & & 0.138 \(\pm\) 0.107 & [21] \\ Ionian Sea & & & (nd–1.50) & [17] \\ Ionian Sea & & & (nd–1.50) & [18] \\ Spanish & 36 & 13.5–14.5 & (0.074–0.121) & [23] \\ Mediterranean & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: THg concentrations (mg kg \({}^{-1}\) w.w.) recorded in other areas of the Mediterranean Sea. \(n\), number of fish samples; mean \(\pm\) standard deviation, range (min–max). lipid content, as investigated in the present study. To the best of our knowledge, only [PERSON] et al. [23] simultaneously investigated several environmental and biological parameters, including lipid content, in Spanish Mediterranean fish. They found a similar lipid content (1.16-5.65 g/100 g, min-max) as that in the present study, with a marked difference between males and females, with higher levels in females. However, no reference to a correlation with Hg content was mentioned by the authors. Our results demonstrated that the distribution of Hg was influenced by several factors, such as sampling area, sex, and reproductive stage. The specimens collected from the open sea showed higher contamination levels than the samples taken from coastal areas. Our findings showed that there was a difference between coastal and open sea samples. Therefore, our findings suggest that sampling area may influence Hg levels in red mullet tissues. Moreover, our findings could be explained by the fact that _M.