# Metallic trace elements in wild and farmed fish from the Aveiro Region (Portugal)

Nathalie El Deghel, Hugo C Vieira, Maria D Bordalo, Steve Peuble, Frederic

Gallice, Jean-Philippe Bedell

► To cite this version:

Nathalie El Deghel, Hugo C Vieira, Maria D Bordalo, Steve Peuble, Frederic Gallice, et al. Metallic trace elements in wild and farmed fish from the Aveiro Region (Portugal). Marine Pollution Bulletin, 2026, 222, pp.118774. 10.1016/j.marpolbul.2025.118774. hal-05302889

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# Metallic trace elements in wild and farmed fish from the Aveiro Region (Portugal)

Nathalie El Deghel<sup>a, *</sup>, Hugo C. Vieira<sup>b</sup>, Maria D. Bordalo<sup>b</sup>, Steve Peuble<sup>c</sup>, Frederic Gallice<sup>c</sup>, Jean-Philippe Bedell<sup>a</sup>

## ARTICLE INFO

### Keywords:

Metal contamination

Fish muscle

Human exposure

Risk assessment

Metal Pollution Index

## ABSTRACT

This study assessed the concentrations of 11 metallic trace elements (MTEs: As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Zn) in fish muscle from eight wild and farmed species collected in the Aveiro region of Portugal, an area historically affected by industrial pollution. A total of 66 samples were analyzed by ICP-MS. Mean concentrations (mg/kg ww), arranged in ascending order, were: Ni (0.0001), Cd (0.0015), Co (0.0020), Pb (0.0023), Cr (0.0179), Mn (0.0862), Cu (0.2500), Se (0.2964), Fe (1.9236), As (1.9260, total As), and Zn (3.3701). Significant differences were observed among species and between wild and farmed fish, particularly in *Dicentrarchus labrax* and *Sparus aurata*. Although Cd and Pb concentrations remained below current European maximum levels, risk assessment based on safe consumption limits (SCLnc) identified total Se, Cd, and Pb as the most restrictive elements for daily intake, especially in children. For arsenic, only total concentrations were considered, as inorganic As could not be distinguished in this study. No significant non-carcinogenic risks were identified at current national average fish consumption levels; however, the potential cumulative and synergistic effects of multiple metals in chronic exposure warrant further investigation. The Metal Pollution Index (MPI < 1 for all samples) confirmed low overall contamination. These findings underscore the importance of ongoing monitoring of trace elements in fish to ensure food safety and protect vulnerable populations.

## 1. Introduction

Seafood consumption is steadily increasing worldwide due to its recognized nutritional and therapeutic benefits, such as reducing the incidence of diabetes and cardiovascular diseases, and enhancing cognitive functions (El-Moselhy et al., 2014; Daschner, 2016; Ballesteros et al., 2020). Fish represents a vital component of the human diet, providing essential nutrients such as proteins, lipids, minerals, and omega-3 content (Prato and Biandolino, 2015; Babenko, 2016; Ward and Hintze, 2016; Miao et al., 2020). In Portugal, fish plays a central role in national dietary habits. Among European countries, Portugal ranks first in terms of its high fish and seafood consumption, with an annual average intake of 59.91 kg (fresh weight) of fish per capita from both wild catch and aquaculture (Murthy et al., 2023).

Among Portuguese coastal regions, Aveiro, located in the center of Portugal, is widely recognized for its historical contamination,

particularly mercury (Hg), due to former chlorine-alkali industrial activities (Cabral-Pinto et al., 2020). Despite this legacy, agricultural and fishing activities in the Ria of Aveiro lagoon, and also in the adjacent sea, remain important (Bedell et al., 2023). Fish consumed in this region, therefore, represents both a nutritional resource and a potential pathway of exposure to environmental contaminants.

Marine ecosystems can be affected by industrial, agricultural, domestic, and mining waste, leading to contamination by metallic trace elements (MTEs) (Hanbeyoğlu et al., 2024), which has been a global problem for years due to their toxicokinetic properties, which can pose a risk to the aquatic fauna and flora (Gambo et al., 2022; Murthy et al., 2023). Fish are commonly used as biomarkers for monitoring MTEs pollution in aquatic ecosystems, as their muscle elemental fingerprints can serve as natural markers to trace the origin of fish, which reflect the chemical composition of the surrounding environment, such as water and sediments, as well as their diet (Luczyńska et al., 2018; Gopi et al.,

<footnote><sup>a</sup> Université Claude Bernard Lyon 1, LEHNA UMR 5023, CNRS, ENTPE, F-69518, Vaulx-en-Velin, France</footnote>

<footnote><sup>b</sup> CESAM - Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, 3810-9 193, Aveiro, Portugal</footnote>

<footnote><sup>c</sup> Mines Saint-Etienne, CNRS, Univ Jean Monnet, Univ Lumière Lyon 2, Univ Lyon 3 Jean Moulin, ENS Lyon, ENTPE, ENSA Lyon, UMR 5600 EVS, centre SPIN, F-42023, Saint-Etienne, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: nathalie.eldeghel@entpe.fr (N. El Deghel).</footnote>
2019). While aquaculture has emerged to meet the rising demand for fish and seafood, some systems reuse treated wastewater or water from dams, rivers, and streams sourced in developing countries, which can cause the introduction of some residual MTEs into the culture environment (Azanu et al., 2016; Nyamete et al., 2022). Furthermore, food formulas, essential for fish, and crops grown in contaminated soil, used as animal feed in aquaculture production, can also contain MTEs (Nyamete et al., 2022; Sarkar et al., 2022; Jiang et al., 2023).

MTEs are classified as crucial for development, such as Mn, Cr, Fe, Se, Zn, Cu, and Co, and non-essential elements, such as As, Cd, Pb, and Ni (Korkmaz et al., 2017; Atamaleki et al., 2020).

Fish can absorb contaminants in the marine environment through the gills, skin, and food ingestion (Jabeen et al., 2018; Dehghani et al., 2022). Various factors, including species and sex, ecological needs, diet, season, metal concentration, water composition, and certain physicochemical parameters, can influence the accumulation of these metallic elements, whether essential or not, in fish muscle (Bella et al., 2017; Renieri et al., 2019).

Located at the top of the aquatic food chain, fish can potentially become a source of toxic metals for humans (Gall et al., 2015). Humans may consume the fish's liver, stomach, and muscle, while fishermen sometimes use these tissues as feed for other fish (Gopi et al., 2019). The risk to human health arises from the concentration of MTEs in fish and the varying eating habits across countries (Renieri et al., 2019). Some studies have reported differences in metal accumulation between wild and farmed fish in the Mediterranean (Lounas et al., 2021), while others found no significant differences, suggesting that metal levels are more influenced by site-specific pollution than production system (Cammilleri et al., 2023).

Few studies have compared the levels of various MTEs in fish caught locally and farmed fish sold in supermarkets or fish markets in the Aveiro region (Pérez Cid et al., 2001; García-Seoane et al., 2016). Most existing research has concentrated on mercury (Hg) contamination in fish (Pereira et al., 2009; Reis et al., 2009; Cardoso et al., 2023), leaving significant knowledge gaps regarding other MTEs. Unlike previous studies, our work investigated a broader spectrum of MTEs in both wild-caught and farmed fish species directly consumed by the local population. Addressing this gap is essential to improve food safety assessment and to support local monitoring strategies.

Therefore, the main objectives of this study are: (i) to quantify metallic trace elements in different fish species consumed in Aveiro, Portugal; and to characterize their dispersion; (ii) to compare, where possible, wild-caught and farmed fish, and (iii) to assess the potential health risks associated with their consumption.

# 2. Materials and methods

## 2.1. Sampling locations

The Aveiro region was selected due to its legacy of industrial contamination and its ongoing importance for fisheries. Eight species from both wild and farmed populations were collected post-mortem from traditional fish markets and supermarket fishmongers. All samples were handled and analyzed exclusively within the project's laboratories, and the research team did not engage in the capture or handling of live specimens.

## 2.2. Fish species examined

### 2.2.1. Xiphias gladius (Linnaeus, 1758)

Xiphias gladius (Linnaeus, 1758; *X. gladius*), commonly known as the swordfish, inhabits the Atlantic, Pacific, and Indian Oceans, as well as the Mediterranean Sea. It is a pelagic, migratory and opportunistic predatory fish that feeds on pelagic fish and invertebrates, mainly squid. It is also known for its high food needs, which leads to an increased intake and, consequently, greater exposure to minerals. Swordfish are

characterized by their high metabolic rate. It is important to evaluate anthropogenic contamination by monitoring concentrations in swordfish over time, because they occupy a top position in the trophic chain, making them the final reservoir for metal bioaccumulation (Mansour and Sidky, 2002; De Azevedo e Silva et al., 2007; Kojadinovic et al., 2007; Girolametti et al., 2023).

### 2.2.2. Scomber scombrus (Linnaeus, 1758)

Scomber scombrus (Linnaeus, 1758; *S. scombrus*), known as Atlantic mackerel, is an abundant pelagic fish and an opportunistic feeder. This schooling species inhabits both sides of the North Atlantic Ocean: the North-West Atlantic (NWA) and the North-East Atlantic (NEA) (Jansen et al., 2019; Moura et al., 2020; Frantzen et al., 2024).

### 2.2.3. Trachurus trachurus (Linnaeus, 1758)

Trachurus trachurus (Linnaeus, 1758; *T. trachurus*), the Atlantic horse mackerel, is a pelagic, carnivorous, voracious fish (Rahmani et al., 2020). This fish contains minerals, vitamins, and polyunsaturated fatty acids (Bektas and Belduz, 2009; Turan et al., 2009; Özden, 2010).

### 2.2.4. Sparus aurata (Linnaeus, 1758)

Sparus aurata (Linnaeus, 1758; *S. aurata*), the gilthead sea bream, is a demersal species, found in Posidonia seagrass beds, and on sandy and rocky bottoms (Fellouh, 2022). It is a common species in the Mediterranean. It lives along the eastern Atlantic coasts, from Great Britain to Senegal, and is rare in the Black Sea (FAO - Sparus aurata Linnaeus, 2009). It is one of the principal Mediterranean aquaculture species and represents an essential economic resource (Mhalhel et al., 2023).

### 2.2.5. Dicentrarchus labrax (Linnaeus, 1758)

Dicentrarchus labrax (Linnaeus, 1758; *D. labrax*), the European Sea bass, is a strictly carnivorous, demersal, and coastal fish (de Pontual et al., 2023; Wassef et al., 2023). This species is found in the Mediterranean Sea and Eastern Atlantic (Fritsch et al., 2007). It is exploited through both capture and recreational fisheries. Due to the increasing demand for these fish species, it's now more commonly produced through aquaculture than fisheries. Sea bass farming is predominantly concentrated in the Mediterranean region, which accounts for 94 % of total production, primarily in Türkiye, Greece, Egypt, and Spain (Vandeputte et al., 2019).

### 2.2.6. Pagrus pagrus (Linnaeus, 1758)

Pagrus pagrus (Linnaeus, 1758; *P. pagrus*), the red porgy, is a fairly new species in aquaculture, with a wide geographical distribution. It inhabits the Eastern Atlantic from the British Isles to Senegal and the Western Atlantic from North Carolina to Argentina, and is also found in the Mediterranean and Adriatic Seas. A carnivorous, bottom-dwelling sparid, the red porgy typically lives on flat sandy bottoms, rhodolith, and seagrass beds. Throughout its native range, it is heavily targeted by both commercial and artisanal fisheries (Van der Salm et al., 2004; Anderson et al., 2022).

### 2.2.7. Helicolenus dactylopterus (Delaroche, 1809)

Helicolenus dactylopterus (Delaroche, 1809; *H. dactylopterus*), the bluemouth rockfish or the blackbelly rosefish, is a marine demersal deep-sea scorpionfish that inhabits coarse and muddy sandy bottoms of the continental shelf and slope at depths from 20 to 1000 m; it is a carnivorous predator found in the Atlantic Ocean and the Mediterranean Sea (Nouar and Maurin, 2000; Mili et al., 2016; Rodríguez-Mendoza et al., 2019).

### 2.2.8. Cynoglossus cadenati (Chabanaud, 1947)

Cynoglossus cadenati (Chabanaud, 1947; *C. cadenati*), also known as Ghanaian tonguesole, is a demersal fish that inhabits the Eastern Atlantic from Senegal to Angola. It can be found on sandy and muddy bottoms of coastal waters from 10 to 30 m (Menon, 1977).
## 2.3. Sample preparation

Length and weight were measured, and the Fulton's condition factor was calculated (CF: fish weight (g) * 100/length³ (cm)) (Eq. (1)) (Renieri et al., 2019). Condition factor helps to assess whether the fish is well nourished. It can be used as an indicator of fat content and reserves in fish (Gao, 2024).

Bones, scales, fins, and entrails were removed from fish samples. Muscle tissues were extracted using a scalpel, weighed, placed in Eppendorf tubes, and stored at -20 °C. Samples were freeze-dried for four days and then weighed again to determine the dry weight. Samples were ground into fine particles using an agate mortar to ensure a homogeneous and representative sample for subsequent analyses.

0.5 g of muscle was weighed into microwave closed vessels and digested using 3:1 mixture of 6 mL of nitric acid (HNO₃, 67 %, Merck Suprapur®) and 2 mL of hydrogen peroxide (H₂O₂, 35 %, Chimie-Plus Laboratoire®). Samples were left at room temperature overnight before digestion. The digestion was then performed using a microwave digestion system (CEM MARS 6), with the temperature raised to 210 °C over 20 min and maintained at 200 °C for 15 min. After cooling to ambient temperature, the digests were diluted to 25 mL with ultrapure water and filtered through Whatman™ No. 541 filter paper with a pore size of 22 µm. All reagents were of analytical grade. Glassware was soaked in 10 % nitric acid and then rinsed with distilled water before use to avoid metal contamination. MTEs (As, Cd, Cu, Co, Cr, Mn, Ni, Pb, Se, Zn) were analyzed and quantified using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS), Agilent 7800 installed at Mines Saint-Etienne, France. Calibration curves were prepared using certified multi-element standard solutions manufactured by SCP Science®. The reference material of fish muscle ERM-BB422 (Table S1) was digested under the same conditions as all samples. All concentrations are given in mg/kg ww (wet weight).

## 2.4. Estimation of safe consumption limits

The non-carcinogenic safe consumption limit (SCL<sub>nc</sub>) estimates the amount of fish that adults (70 kg) or children (15 kg) can safely consume daily without having a non-carcinogenic health effect (US EPA, 2015). This limit was only calculated for metals having a chronic oral reference dose (total As and Co were excluded).

$$SCL_{nc} = \frac{RfDo * BW}{C} \qquad (2)$$

where:

SCL<sub>nc</sub> = non-carcinogenic safe consumption limit

C = Concentration of metal in mg/kg ww

RfDo = chronic oral reference dose (mg/kg/day) (with 1.0E-04 for Cd, 3.0E-03 for Cr, 4.0E-02 for Cu, 7.0E-01 for Fe, 1.4E-01 for Mn, 2.0E-02 for Ni, 4.0E-03 for Pb, 5.0E-03 for Se and 3.0E-01 for Zn) (Nag and Cummins, 2022; US EPA, 2024)

BW = 70 kg for adults and 15 kg for children.

## 2.5. Metal Pollution Index (MPI)

The MPI was calculated using the metal concentrations found in fish muscle to assess the overall environmental contamination level. This index summarizes the impact of all metals for evaluating toxicity in food and aquatic ecosystems (Ustaoğlu and Yüksel, 2024).

$$MPI (mg/kg) = (Cf_1 \times Cf_2 \times \dots \times Cf_k)^{1/k} \qquad (3)$$

where Cf<sub>1</sub> is the concentration of the first metal, Cf<sub>2</sub> is the concentration of the second metal, and Cf<sub>k</sub> for the K<sub>th</sub> metal.

## 2.6. Data expression

The limit of detection (LOD) was set at 3 times the standard deviation (SD) of the mean of blank determinations, and the limit of quantification (LOQ) at 10 times the SD of the mean of blank determinations (Wenzl et al., 2016). LOD and LOQ were determined in ppm wet weight after correction by the sample weight (0.5 g dry weight) and corresponding dilution. For some metals, concentrations were found to be below LOQ. To calculate mean concentrations, values below the LOD are taken as equal to the LOD, and those found between the LOD and the LOQ are taken as equal to the LOQ (Noël et al., 2003). The coefficient of determination (R²) values indicated a good linearity for all calibration curves. Detailed values of LOD, LOQ and R² for each element are presented in the Supplementary material (Table S2).

Descriptive statistics (range (min-max) and mean concentration ± SD) were computed based on fish species, fishing method, and origin. All values were expressed in mg/kg ww.

## 2.7. Statistical analyses

The Shapiro-Wilk test was used to verify the normality of the data (Ali et al., 2020). The test revealed non-normal distributions. Therefore, non-parametric tests were applied for statistical analyses. The Spearman correlation was used to explore the association between MTEs and morphometric characteristics of the fish. Kruskal-Wallis tests were used to compare MTEs concentrations among different fish species issued from wild capture, followed by Dunn's post hoc test (with Bonferroni correction) for pairwise comparisons. Finally, a specific focus was placed on *D. labrax* and *S. aurata* to evaluate the difference between the fish origins. All analyses were performed using RStudio© 2024.12.1; The test's significance level (p) was consistently set at 0.05 (Tables S4 and S5).

# 3. Results and discussion

## 3.1. Samples and condition factor (CF)

A total of 66 fish samples were collected. Details of the fish species by

<table><caption>**Table 1**
List of fish species sampled according to biotype and production type.</caption><thead><tr><th>Scientific name</th><th>Common name</th><th>Habitat</th><th>Production type</th><th>Number of samples (n)</th></tr></thead><tbody><tr><td><i>S. scombrus</i></td><td>Atlantic mackerel</td><td>Pelagic</td><td>Wild</td><td>5</td></tr><tr><td><i>D. labrax</i></td><td>European sea bass</td><td>Demersal</td><td>Wild<br>Aquaculture (Portugal)<br>Aquaculture (Greece)<br>Aquaculture (Türkiye)</td><td>5<br>5<br>5<br>5</td></tr><tr><td><i>S. aurata</i></td><td>Gilthead seabream</td><td>Demersal</td><td>Wild<br>Aquaculture (Portugal)<br>Aquaculture (Greece)<br>Aquaculture (Türkiye)</td><td>5<br>5<br>5<br>5</td></tr><tr><td><i>T. trachurus</i></td><td>Horse mackerel</td><td>Pelagic-neritic</td><td>Wild</td><td>5</td></tr><tr><td><i>X. gladius</i></td><td>Swordfish</td><td>Pelagic-oceanic</td><td>Wild</td><td>3</td></tr><tr><td><i>P. pagrus</i></td><td>Red Porgy</td><td>Benthopelagic</td><td>Wild</td><td>5</td></tr><tr><td><i>C. cadenati</i></td><td>Ghanian tonguesole</td><td>Demersal</td><td>Wild</td><td>5</td></tr><tr><td><i>H. dactylopterus</i></td><td>Blackbelly rosefish</td><td>Bathydemersal</td><td>Wild</td><td>3</td></tr></tbody></table>
biotype and production type are presented in Table 1. Only *D. labrax* and *S. aurata* were available from both wild and aquaculture sources. The mean length (cm), fresh weight (g) of the whole fish and condition factor are presented in Table 2, summarized by species, origin, and fishing type.

The condition factor (CF) was calculated for each sample. A High CF reflects a good nutritional status, and high fat reserve. Meanwhile, a low CF may indicate a low-fat composition in fish, typically observed when length increases faster than weight (Gao, 2024).

Thus, 19% of the samples had a CF below 1, all of which were wild-caught. The lowest values were recorded in *X. gladius* (mean CF = 0.152 ± 0.022; range: 0.126–0.165) and *P. pagrus* (mean CF = 0.303 ± 0.047; range: 0.233–0.359).

For *D. labrax*, significant differences in condition factor were observed among origins (*p* < 0.05). Seabass from Greece showed a significantly lower mean CF (1.57) compared to those from Portugal (1.9), Türkiye (1.88), and Aveiro (1.8) (Fig. 1A). For *S. aurata*, significant differences for CF were detected among the origins (*p* < 0.05). The condition factor was significantly lower in seabream from Greece (2.65) than those from Türkiye (3.18) (Fig. 1B). CF can be influenced by species, life stage, environmental factors, and season. Low CF values are typically observed during the colder season, while high levels are associated with warmer months (Ahmad and Ahmed, 2019). In this study, all aquaculture-derived samples exhibited a good CF (above 1). Feed quality and quantity can influence the health and the growth of the fish (Ahmad and Ahmed, 2019). Effectively, farming practices can also affect fish length and weight, as previously shown in *S. aurata* from different aquaculture systems (Mamede et al., 2022). However, since our samples were purchased from the supermarket, detailed information regarding the farming process (e.g., earth ponds, sea cage aquaculture) was not available, limiting further interpretation.

## 3.2. MTEs results

The mean (± SD) concentration and the results' range (min-max) grouped by fish species, production type, and origin for essential (Co, Cr, Cu, Fe, Mn, Se, Zn) and non-essential (As, Cd, Pb, Ni) trace elements are expressed in mg/kg ww in Table 3. When compared to other studies, where results were expressed in dry weight (dw), an average moisture content of around 80% in fish was considered (Lounas et al., 2021).

### 3.2.1. MTEs and morphometric parameters

The concentration of MTEs in fish tissues can be influenced by several factors, such as age, size, and length (Al-Yousuf et al., 2000).

To explore these relationships, Spearman correlation analysis was performed on all samples to assess the relationships between morphometric characteristics, condition factors, and concentrations of MTEs.

The results revealed that each element has at least one significant correlation (*p* < 0.05) with another variable (Fig. 2).

Subsequently, separate Spearman tests were conducted for each species to explore correlations between morphometric characteristics and MTEs. For *X. gladius* and *H. dactylopterus*, Spearman correlation was not applied due to the low number of samples (*n* = 3 only). In *S. scombrus* and *P. pagrus*, no significant correlations were observed between the tested variables.

In *D. labrax*, the CF showed correlations with several MTEs (Co, Ni, Cd, Pb). Length was negatively correlated with Cu and Zn. Length and weight were positively correlated with Se. Elements such as Cr, Mn, Fe, and As showed no significant correlations with any of the morphometric parameters.

In *S. aurata*, only As showed a significant (negative) correlation with both length and weight.

In *T. trachurus*, a significant negative correlation was found between length and Zn. A perfect correlation between condition factor and Co (*p* = 1) was observed, but should be interpreted cautiously. In *C. candenati*, weight showed significant positive correlations with both Cu and Cd.

In this study, negative and positive correlations, or even non-significant correlations, between morphometrics and element concentration, as different correlations for the same elements, were found, which is in line with other studies exploring the same relationships (Al-Yousuf et al., 2000; Canli and Atli, 2003; Merciai et al., 2014; Milosković and Simić, 2015; Traina et al., 2019). Several factors or hypotheses may explain the negative correlations-observed. For instance, the growth rate of fish tissue can be faster than the metal intake. Additionally, seasonal fluctuations in body condition (e.g., weight-length ratios) may lead to opposite trends in a given species sampled at different times of the year (Merciai et al., 2014). Other relevant factors may include the species's detoxification capacity and lipid content (Canli and Atli, 2003).

### 3.2.2. MTEs between species

Concentrations of MTEs were initially compared among the wild-caught fish species sampled from the Aveiro Region. All MTEs, except for Cr, showed statistically significant differences between species (*p* < 0.05). Different letters in the same column in Table 3 indicate significant interspecific differences for each element. Essential element concentrations were quantified in all analyzed fish samples, with notable variations between species.

The mean values (±SD), expressed in mg/kg (ww) of essential and non-essential elements are presented as follows Ni (0.0001 ± 0.0006) < Pb (0.0007 ± 0.0041) < Co (0.0025 ± 0.0016) ≈ Cd (0.0026 ± 0.0034) < Cr (0.0149 ± 0.0102) < Mn (0.0785 ± 0.0444) < Cu (0.2169 ± 0.1304) < Se (0.3868 ± 0.1579) < Fe (2.2439 ± 1.7251) < Zn (3.0097 ± 0.9408) < As (3.0623 ± 4.9114).

Results were also compared with other studies summarized in

<caption>**Table 2**</caption>

Morphometric characteristics and condition factor (CF) of fish by species, origin, and fishing type (W for wild, A for aquaculture). All values are expressed by mean (±standard deviation; SD) and range (min-max).

<table><thead><tr><th>Scientific name</th><th>Fishing type</th><th>Origin</th><th>Length (cm)</th><th>Fresh weight (g)</th><th>Condition factor (CF)<sup>a</sup></th></tr></thead><tbody><tr><td><i>C. candenati</i></td><td>W</td><td>Aveiro</td><td>32.3 ± 2.178 (29–34.5)</td><td>349.38 ± 80.489 (236.7–445.1)</td><td>1.022 ± 0.092 (0.965–1.184)</td></tr><tr><td rowspan="4"><i>D. labrax</i></td><td>A</td><td>Portugal</td><td>25.98 ± 0.581 (25.1–26.7)</td><td>333.48 ± 27.368 (303.4–359.9)</td><td>1.901 ± 0.12 (1.756–2.048)</td></tr><tr><td>A</td><td>Greece</td><td>26 ± 0.612 (25–26.5)</td><td>276.34 ± 21.459 (241.2–294)</td><td>1.569 ± 0.019 (1.544–1.591)</td></tr><tr><td>A</td><td>Türkiye</td><td>33.46 ± 2.053 (30.6–35.9)</td><td>697.86 ± 58.254 (640.7–761.2)</td><td>1.878 ± 0.242 (1.645–2.236)</td></tr><tr><td>W</td><td>Aveiro</td><td>29.1 ± 0.822 (28.5–30)</td><td>443.36 ± 33.385 (413.3–499.3)</td><td>1.799 ± 0.089 (1.65–1.871)</td></tr><tr><td><i>H. dactylopterus</i></td><td>W</td><td>Aveiro</td><td>26.167 ± 0.289 (26–26.5)</td><td>535.5 ± 28.922 (512–567.8)</td><td>2.987 ± 0.07 (2.913–3.051)</td></tr><tr><td><i>P. pagrus</i></td><td>W</td><td>Aveiro</td><td>20.84 ± 1.737 (19–23.5)</td><td>27 ± 2.338 (24.6–30.3)</td><td>0.303 ± 0.047 (0.233–0.359)</td></tr><tr><td><i>S. scombrus</i></td><td>W</td><td>Aveiro</td><td>29.06 ± 0.498 (28.4–29.6)</td><td>248.98 ± 13.103 (226.5–258.5)</td><td>1.016 ± 0.077 (0.929–1.129)</td></tr><tr><td rowspan="4"><i>S. aurata</i></td><td>A</td><td>Portugal</td><td>23.74 ± 1.276 (22.2–25.7)</td><td>376.48 ± 61.8 (293.8–468.1)</td><td>2.795 ± 0.103 (2.685–2.917)</td></tr><tr><td>A</td><td>Greece</td><td>26.16 ± 1.197 (25–27.5)</td><td>477.22 ± 68.84 (402.5–565.7)</td><td>2.653 ± 0.143 (2.485–2.817)</td></tr><tr><td>A</td><td>Türkiye</td><td>26.98 ± 0.829 (25.9–28)</td><td>621.2 ± 24.578 (590.1–653)</td><td>3.176 ± 0.292 (2.838–3.431)</td></tr><tr><td>W</td><td>Aveiro</td><td>24.96 ± 1.477 (23.5–26.8)</td><td>423.88 ± 38.544 (381.2–479)</td><td>2.738 ± 0.258 (2.488–3.074)</td></tr><tr><td><i>T. trachurus</i></td><td>W</td><td>Aveiro</td><td>19.88 ± 0.669 (19.4–21)</td><td>91.12 ± 11.099 (76.9–107.8)</td><td>1.156 ± 0.06 (1.053–1.204)</td></tr><tr><td><i>X. gladius</i></td><td>W</td><td>Aveiro</td><td>95.5 ± 3.122 (92–98)</td><td>1338.833 ± 308.868 (984.3–1549.7)</td><td>0.152 ± 0.022 (0.126–0.165)</td></tr></tbody></table>

<footnote>a Condition factor was calculated using this formula: CF = fish weight (g) * 100 / length³ (cm) (Eq. (1)) (Renieri et al., 2019).</footnote>
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Condition factor values for *Dicentrarchus labrax* (A) and *Sparus aurata* (B) according to their origins. Bars with different letters indicate statistically significant differences between groups (*p* < 0.05).</figcaption></figure>

<figure><img src="image_4.png" /></figure>

Table S3.

3.2.2.1. **Arsenic (As).** The highest total As concentrations were observed in two demersal fish species, *C. cadenati* (14.2 ± 5.8 mg/kg ww) and *H. dactylopterus* (2.198 ± 0.2). Other species, ranked in descending order of As levels, included: *T. trachurus* > *X. gladius* > *P. pagrus* > *S. scombrus* > *S. aurata* > *D. labrax*.

The elevated concentrations in *C. cadenati* and *H. dactylopterus* (a demersal carnivore) could result from sediment contamination and ingestion of benthic prey (Zhang and Wang, 2012). Similar findings were reported by Saei-Dehkordi et al. (2010), who noted higher concentrations of As and Hg in demersal species compared to benthopelagic and pelagic species. However, in the present study, As concentrations in *S. aurata* and *D. labrax*, both demersal, were lower than those found in pelagic species.

No previous studies reported As in the *C. cadenati* species. Still, related species such as *Cynoglossus arel* showed levels between 1.8 and 1.92 mg/kg dw basis (Ali et al., 2020), while *Cynoglossus joyneri* from Chinese coastal waters, the mean As concentration was found to be 17.6 ± 2.23 and 48.4 ± 6.32 µg/g dw basis in two different locations (W. Zhang and Wang, 2012).

For *H. dactylopterus*, the As concentrations observed in our study (2.034–2.421 mg/kg ww) align with those from the Condor seamount (0.87–3.0 mg/kg ww) (Raimundo et al., 2015), but are lower than those reported in Portugal (mean: 4.4 ± 0.81; range: 2.8–5.8 mg/kg ww) (Anacleto et al., 2009), and much lower than the values observed in specimens collected from the red mud-impacted zone near the Cassi-daigne Canyon in the northwest of the French Mediterranean (10.166 ± 5.484; range: 2.690–25.008 mg/kg ww), as well as from a nearby reference zone (5.281 ± 2.442 mg/kg ww; range: 2.111–12.1 mg/kg ww) (Bouchoucha et al., 2019).

3.2.2.2. **Cadmium (Cd).** Cd, a toxic metal, can accumulate in fish muscles, posing a health risk to consumers (Ustaoğlu and Yüksel, 2024). To mitigate this risk, maximum permitted levels for Cd have been established: 0.10 mg/kg ww in *S. scombrus* (Atlantic mackerel), 0.25 mg/kg ww in *X. gladius* (Swordfish), whereas for other fish species, it is set at 0.05 mg/kg ww (EC, 2023). Cd was detected in 54.5 % of the samples. Mean Cd concentrations ranged between <LOD and 0.008 ± 0.005 mg/kg ww, with an overall mean of 0.0026 ± 0.0034 mg/kg (upper bound).

The highest mean concentration was found in *P. pagrus* (0.008 ± 0.005 mg/kg ww), followed by *T. trachurus* (0.004 ± 0.004 mg/kg ww) and *X. gladius* (0.004 ± 0.003 mg/kg ww). For other fish species, concentrations were near 0.001 mg/kg ww. Cd tends to accumulate more in

the liver and kidneys, due to the presence of high levels of metallothioneins, chelating proteins that store Cd, to protect fish against metal toxicity, thereby explaining the low muscle levels (Mille et al., 2018).

The Cd values in *P. pagrus* are considerably lower than those reported in Egypt (0.49 mg/kg ww; Malak et al., 2025). Conversely, Cd was below the detection limits in *P. pagrus* and *T. trachurus* from the Northeast Mediterranean (Korkmaz et al., 2022), as well as in *T. trachurus* from some coastal and inland waters in Ghana (Tay et al., 2008). In comparison, mean Cd level in horse mackerel from the Sea of Marmara was approximately ten times higher (0.039 ± 0.0079 mg/kg ww) (Hanbeyoğlu et al., 2024). Cd was not detected in *X. gladius* samples from the Mediterranean Sea (Di Bella et al., 2020), whereas higher levels (0.16 ± 0.05 mg/kg ww) were reported by Barone et al. (2018).

3.2.2.3. **Lead (Pb).** Pb was detected in only one wild-caught *T. trachurus* (0.025 mg/kg ww equivalent to 0.121 mg/kg dw), well below the maximum permitted level for Pb, set as 0.30 mg/kg ww (EC, 2023). Pb was not detected in most of our samples, aligning with findings from the Portuguese coastal fish (Pinto et al., 2022), as it tends to accumulate less in muscle compared to metabolically active organs (Lee et al., 2019). Higher concentrations have been reported in samples from the polluted Sea of Marmara (0.36 ± 1.13 mg/kg ww; Hanbeyoğlu et al., 2024), in Ghana, where concentrations reached 1.09 ± 0.58 mg/kg ww (Tay et al., 2008), and in specimens caught in the polluted Durban Basin in South Africa (4.1 ± 0.51 mg/kg dw) (Debipersadh et al., 2023). In contrast, all Pb concentrations were below the limit of quantification on the Mauritanian coast (Learoussy et al., 2022).

3.2.2.4. **Nickel (Ni).** Ni, essential for fish metabolism at minimal concentrations, is absorbed by the gills via waterborne exposure or by the gastrointestinal tract through dietary intake. Once inside the organism, Ni binds to peptides and accumulates in the kidneys. However, it can also exert genotoxic effects and may harm fish health at high concentrations (Pyle and Couture, 2011; Singh and Sharma, 2024). Ni was below the detection limit for nearly all the samples, similar to findings in the Northeast Mediterranean (Korkmaz et al., 2022). Only *X. gladius* exceeded the LOQ (0.021 mg/kg ww), a value within the range of those found in swordfish (0.010–0.268 mg/kg ww) from the Mediterranean Sea (Di Bella et al., 2020) and around Corsica Island (Mediterranean Sea), with a range of 0.003 and 3.191 mg/kg ww (Gobert et al., 2017). This value was lower than those reported in wild aquatic species by Iamiceli et al. (2015), 0.088 and 0.124 mg/kg ww, and those reported by Barone et al. (2018) (mean: 0.52 ± 0.33; range: 0.08–1.15 mg/kg ww).
<caption>Table 3</caption>

Mean (±standard deviation; SD) and range (min-max) of trace elements concentrations (mg/kg ww) in the analyzed fish muscles.

<table><thead><tr><th>Scientific name</th><th>n</th><th>Cr</th><th>Mn</th><th>Fe</th><th>Co</th><th>Ni</th><th>Cu</th><th>Zn</th><th>As</th><th>Se</th><th>Cd</th><th>Pb</th></tr></thead><tbody><tr><td>C. cadenati (wild-Aveiro)</td><td>5</td><td>0.014 ± 0.013<sup>a</sup><br>(0.003-0.035)</td><td>0.1 ±<br>0.044<sup>ab</sup>(0.059-0.174)</td><td>1.034 ±<br>0.287<sup>abc</sup><br>(0.62-1.388)</td><td>0.005 ± 0.002<sup>a</sup><br>(0.002-0.007)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.113 ± 0.029<sup>a</sup><br>(0.072-0.143)</td><td>3.849 ± 0.405<sup>a</sup><br>(3.214-4.274)</td><td>14.179 ±<br>5.787<sup>a</sup><br>(7.379-20.76)</td><td>0.68 ± 0.12<sup>a</sup><br>(0.587-0.889)</td><td>0.001 ±<br>0.002<sup>ab</sup><br>(0-0.005)</td><td>0 ± 0<sup>ab</sup><br>(0-0)</td></tr><tr><td>D. labrax (aquaculture-Portugal)</td><td>5</td><td>0.04 ± 0.054<br>(0.007-0.136)</td><td>0.138 ± 0.026<br>(0.117-0.179)</td><td>2.643 ± 0.703<br>(1.678-3.614)</td><td>0.002 ± 0.001<br>(0.001-0.003)</td><td>0 ±<br>(0-0)</td><td>0.473 ± 0.053<br>(0.383-0.525)</td><td>4.229 ± 0.901<br>(3.278-5.526)</td><td>0.425 ± 0.035<br>(0.398-0.487)</td><td>0.162 ± 0.016<br>(0.149-0.189)</td><td>0 ± 0<br>(0-0)</td><td>0 ±<br>(0-0)</td></tr><tr><td>D. labrax (aquaculture-Greece)</td><td>5</td><td>0.009 ± 0.005<br>(0.001-0.015)</td><td>0.115 ± 0.037<br>(0.087-0.179)</td><td>1.178 ± 0.574<br>(0.761-2.175)</td><td>0.001 ±<br>(0-0)</td><td>0 ±<br>(0-0)</td><td>0.247 ± 0.088<br>(0.17-0.366)</td><td>3.634 ± 0.553<br>(3.052-4.495)</td><td>0.545 ± 0.36<br>(0.252-0.987)</td><td>0.149 ± 0.024<br>(0.122-0.168)</td><td>0 ± 0<br>(0-0)</td><td>0 ±<br>(0-0)</td></tr><tr><td>D. labrax (aquaculture-Türkiye)</td><td>5</td><td>0.026 ± 0.046<br>(0.003-0.107)</td><td>0.123 ± 0.017<br>(0.103-0.144)</td><td>0.996 ± 0.565<br>(0.566-1.969)</td><td>0.001 ±<br>(0-0)</td><td>0 ±<br>(0-0)</td><td>0.17 ± 0.041<br>(0.116-0.227)</td><td>3.33 ± 0.221<br>(3.085-3.637)</td><td>0.343 ± 0.106<br>(0.24-0.521)</td><td>0.196 ± 0.014<br>(0.18-0.207)</td><td>0 ± 0<br>(0-0)</td><td>0 ±<br>(0-0)</td></tr><tr><td>D. labrax (wild-Aveiro)</td><td>5</td><td>0.014 ± 0.003<sup>a</sup><br>(0.012-0.02)</td><td>0.159 ± 0.045<sup>a</sup><br>(0.095-0.208)</td><td>1.751 ±<br>0.818<sup>abc</sup><br>(0.838-2.628)</td><td>0.002 ± 0<sup>ab</sup><br>(0.001-0.002)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.313 ± 0.16<sup>a</sup><br>(0.133-0.484)</td><td>4.312 ± 1.217<sup>a</sup><br>(3.235-6.4)</td><td>0.695 ± 0.437<sup>b</sup><br>(0.289-1.368)</td><td>0.262 ±<br>0.023<sup>bc</sup><br>(0.231-0.287)</td><td>0.001 ±<br>0.001<sup>ab</sup><br>(0-0.002)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td></tr><tr><td>H. dactylopterus (wild-Aveiro)</td><td>3</td><td>0.006 ± 0.006<sup>a</sup><br>(0.002-0.013)</td><td>0.045 ± 0.009<sup>bc</sup><br>(0.038-0.056)</td><td>0.82 ± 0.261<sup>ab</sup><br>(0.605-1.11)</td><td>0.002 ± 0.001<sup>ab</sup><br>(0.001-0.002)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.082 ± 0.034<sup>a</sup><br>(0.052-0.119)</td><td>2.309 ±<br>0.318<sup>ab</sup><br>(1.955-2.57)</td><td>2.198 ± 0.2<sup>ab</sup><br>(2.034-2.421)</td><td>0.408 ±<br>0.024<sup>abc</sup><br>(0.388-0.435)</td><td>0.002 ±<br>0.002<sup>ab</sup><br>(0-0)</td><td>0 ± 0<sup>ab</sup><br>(0-0)</td></tr><tr><td>P. pagrus (wild-Aveiro)</td><td>5</td><td>0.015 ± 0.014<sup>a</sup><br>(0.005-0.039)</td><td>0.038 ± 0.012<sup>c</sup><br>(0.024-0.052)</td><td>1.63 ± 0.637<sup>abc</sup><br>(1.089-2.548)</td><td>0.003 ± 0.001<sup>ab</sup><br>(0.002-0.004)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.123 ± 0.018<sup>a</sup><br>(0.101-0.146)</td><td>2.359 ±<br>0.471<sup>ab</sup><br>(1.84-3.086)</td><td>1.135 ±<br>0.549<sup>ab</sup><br>(0.656-2.029)</td><td>0.468 ± 0.09<sup>ab</sup><br>(0.392-0.613)</td><td>0.008 ± 0.005<sup>a</sup><br>(0.003-0.015)</td><td>0 ± 0<sup>ab</sup><br>(0-0)</td></tr><tr><td>S. scombrus (wild-Aveiro)</td><td>5</td><td>0.018 ± 0.007<sup>a</sup><br>(0.008-0.025)</td><td>0.058 ± 0.013<sup>abc</sup><br>(0.047-0.08)</td><td>4.922 ± 0.662<sup>c</sup><br>(4.084-5.887)</td><td>0.002 ± 0<sup>ab</sup><br>(0.001-0.003)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.309 ± 0.044<sup>a</sup><br>(0.255-0.37)</td><td>2.232 ± 0.387<sup>b</sup><br>(1.94-2.907)</td><td>1.056 ±<br>0.381<sup>ab</sup><br>(0.399-1.397)</td><td>0.306 ±<br>0.026<sup>abc</sup><br>(0.262-0.329)</td><td>0 ± 0<sup>b</sup><br>(0-0.001)</td><td>0 ± 0<sup>ab</sup><br>(0-0)</td></tr><tr><td>S. aurata (aquaculture-Portugal)</td><td>5</td><td>0.035 ± 0.028<br>(0.008-0.068)</td><td>0.07 ± 0.017<br>(0.058-0.099)</td><td>2.089 ± 0.832<br>(1.431-3.503)</td><td>0.002 ± 0.001<br>(0.001-0.003)</td><td>0 ±<br>(0-0)</td><td>0.428 ± 0.249<br>(0.237-0.865)</td><td>3.808 ± 0.758<br>(3.017-4.764)</td><td>0.971 ± 0.262<br>(0.516-1.165)</td><td>0.25 ± 0.022<br>(0.225-0.279)</td><td>0 ±<br>(0-0.001)</td><td>0.025 ±<br>0.055<br>(0-0.124)</td></tr><tr><td>S. aurata (aquaculture-Greece)</td><td>5</td><td>0.013 ± 0.014<br>(0.002-0.036)</td><td>0.062 ± 0.026<br>(0.041-0.105)</td><td>1.114 ± 0.853<br>(0.479-2.561)</td><td>0.001 ±<br>(0-0)</td><td>0 ±<br>(0-0)</td><td>0.186 ± 0.033<br>(0.146-0.234)</td><td>3.843 ± 0.372<br>(3.251-4.257)</td><td>0.647 ± 0.224<br>(0.412-0.922)</td><td>0.183 ± 0.021<br>(0.151-0.201)</td><td>0 ± 0<br>(0-0)</td><td>0 ±<br>(0-0)</td></tr><tr><td>S. aurata (aquaculture-Türkiye)</td><td>5</td><td>0.006 ± 0.005<br>(0.001-0.014)</td><td>0.063 ± 0.014<br>(0.052-0.087)</td><td>1.214 ± 0.622<br>(0.581-2.256)</td><td>0.001 ±<br>(0-0)</td><td>0 ±<br>(0-0)</td><td>0.234 ± 0.114<br>(0.138-0.431)</td><td>3.973 ± 0.872<br>(2.957-5.073)</td><td>0.444 ± 0.072<br>(0.358-0.51)</td><td>0.187 ± 0.023<br>(0.166-0.227)</td><td>0.001 ± 0.001<br>(0-0.002)</td><td>0 ±<br>(0-0)</td></tr><tr><td>S. aurata (wild-Aveiro)</td><td>5</td><td>0.017 ± 0.014<sup>a</sup><br>(0.004-0.039)</td><td>0.057 ± 0.008<sup>abc</sup><br>(0.046-0.066)</td><td>1.538 ±<br>0.525<sup>abc</sup><br>(0.788-2.157)</td><td>0.001 ± 0<sup>b</sup><br>(0.001-0.002)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.251 ± 0.075<sup>a</sup><br>(0.133-0.327)</td><td>3.326 ±<br>0.755<sup>ab</sup><br>(2.378-4.458)</td><td>0.9 ± 0.534<sup>b</sup><br>(0.492-1.826)</td><td>0.2 ± 0.047<sup>c</sup><br>(0.156-0.273)</td><td>0.001 ±<br>0.001<sup>ab</sup><br>(0-0.002)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td></tr><tr><td>T. trachurus (wild-Aveiro)</td><td>5</td><td>0.017 ± 0.012<sup>a</sup><br>(0.005-0.034)</td><td>0.077 ± 0.021<sup>abc</sup><br>(0.053-0.105)</td><td>4.499 ±<br>1.566<sup>ac</sup><br>(3.048-6.617)</td><td>0.003 ± 0.002<sup>ab</sup><br>(0.002-0.005)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td><td>0.352 ± 0.145<sup>a</sup><br>(0.224-0.581)</td><td>2.767 ±<br>0.429<sup>ab</sup><br>(2.155-3.289)</td><td>1.854 ±<br>1.161<sup>ab</sup><br>(1.133-3.862)</td><td>0.341 ±<br>0.041<sup>abc</sup><br>(0.278-0.39)</td><td>0.004 ±<br>0.004<sup>ab</sup><br>(0-0.008)</td><td>0.005 ±<br>0.011<sup>ab</sup><br>(0-0.025)</td></tr><tr><td>X. gladius (wild-Aveiro)</td><td>3</td><td>0.014 ± 0.012<sup>a</sup><br>(0.004-0.027)</td><td>0.081 ± 0.02<sup>abc</sup><br>(0.062-0.102)</td><td>0.482 ± 0.213<sup>b</sup><br>(0.242-0.651)</td><td>0.001 ± 0<sup>b</sup><br>(0.001-0.001)</td><td>0.001 ±<br>0.002<sup>a</sup><br>(0-0.004)</td><td>0.086 ± 0.015<sup>a</sup><br>(0.071-0.101)</td><td>2.399 ± 0.14<sup>ab</sup><br>(2.31-2.56)</td><td>1.517 ±<br>0.518<sup>ab</sup><br>(1.214-2.115)</td><td>0.47 ± 0.052<sup>ab</sup><br>(0.431-0.528)</td><td>0.004 ±<br>0.003<sup>ab</sup><br>(0.002-0.008)</td><td>0 ± 0<sup>a</sup><br>(0-0)</td></tr></tbody></table>

Different letters in the same column demonstrate statistical variations between fish species from wild capture (p < 0.05).
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Spearman correlation matrix (ρ) between calculated condition factor, fish morphometric characteristics (length and weight), and the concentrations of the analyzed elements (mg/kg ww).</figcaption></figure>

3.2.2.5. Chromium (Cr). Cr can exist in several oxidation states as divalent (Cr⁺²), trivalent (Cr⁺³), and hexavalent (Cr⁺⁶). The Cr⁺³ is an essential element for fish development and metabolism, meanwhile Cr⁺⁶ is considered the toxic form owing to its high membrane permeability and its intracellular reduction to Cr⁺³, where it can bind to macromolecules (e.g., genetic material), leading to toxic and mutagenic effects (Farag et al., 2006; Bakshi and Panigrahi, 2018). In this study, total Cr concentrations were measured, with mean values ranging from 0.006 mg/kg ww in *H. dactylopterus* to 0.018 mg/kg ww in *S. scombrus*, and an overall mean of 0.015 ± 0.01 mg/kg ww. These values were lower than those reported in wild fish from the Mediterranean Sea (0.07 to 0.09 mg/kg ww; Iamiceli et al., 2015) and the Adriatic Sea (0.007–0.083 mg/kg; Sepe et al., 2003). Cr concentrations in *H. dactylopterus* were lower than those found by Bouchoucha et al. (2019) and in the Azores (0.10–0.32 mg/kg; Raimundo et al., 2015).

3.2.2.6. Copper (Cu). Cu is an essential element necessary for fish growth and development, primarily absorbed via the gills and digestive tract (Lall and Kaushik, 2021). However, exposure to elevated Cu concentration can cause acute toxicity in aquatic organisms, potentially leading to mortality. Cu concentrations ranged from 0.082 ± 0.034 mg/kg ww in *H. dactylopterus* and 0.086 ± 0.015 mg/kg ww in *X. gladius* to 0.352 ± 0.145 mg/kg ww in *T. trachurus*, which showed the highest levels. The overall mean concentration was 0.2169 ± 0.1304 mg/kg ww. Cu levels in *X. gladius* were lower than those reported by Gobert et al. (2017) (0.349 ± 0.029 mg/kg ww) and in the Indian Ocean (0.342 ± 0.175 mg/kg ww) (Bodin et al., 2016). Cu concentrations in *H. dactylopterus* (0.052–0.119 mg/kg) were within ranges reported in Raimundo et al. (2015) (0.039–0.40 mg/kg) and Raimundo et al. (2013) (0.028–0.23 mg/kg), but lower than those reported in Carvalho et al.

(2005). *T. trachurus* levels were similar to those found in Korkmaz et al. (2022) (0.34 ± 0.35 mg/kg ww), but too much lower than those found in Ghana for the same specimen (7.68 ± 1.61 mg/kg ww; Tay et al., 2008).

3.2.2.7. Zinc (Zn). Zn is an essential element in several physiological processes, including immunity, fertility, and antioxidant defense (Zhao et al., 2014). However, Zn is often present at low concentrations in raw materials, making dietary supplementation necessary to meet nutritional needs. Nevertheless, high Zn concentrations and intake can lead to adverse effects in fish, such as functional alterations of internal organs, impaired nerve impulse transmission, and reduced mobility (Tomilina et al., 2014; Naz et al., 2023). In this study, the highest Zn concentration was found in *D. labrax* (4.312 ± 1.217 mg/kg ww), while *S. scombus* showed the lowest mean concentration (2.232 ± 0.387 mg/kg ww). Zn concentrations were found to be higher than those reported by Yildiz (2008) (3.1 ± 0.12 mg/kg ww), and similar to those reported in Marengo et al. (2018) (4.221 ± 0.165).

3.2.2.8. Selenium (Se). Se is a micronutrient that fish acquire from their natural environment or through dietary supplementation in aquaculture. It improves oxidative stress defense by activating the selenoenzymes and selenoproteins (Khan et al., 2017) and protects against Hg and Cd toxicity (Newairy et al., 2007; Ralston and Raymond, 2010). Insufficient Se intake can lead to growth depression and immune dysfunction (Lin and Shiau, 2005). However, excessive Se can accumulate in muscles and vital organs, causing toxicity (Rodríguez and Rojas, 2014).

The mean Se concentration in wild-caught fish was 0.39 ± 0.16 mg/kg. The highest mean concentration was found in *C. cadenati* (0.68 ±
0.12 mg/kg ww), and the lowest in *S. aurata* (0.2 ± 0.047¹ range: 0.156-0.273 mg/kg ww). A higher results range (0.255-2.788 mg/kg ww) was reported in wild *S. aurata* from the Portuguese mainland coast (Mamede et al., 2022). In contrast, comparable results were found in specimens from the Corsican coast (0.228 ± 0.011) (Marengo et al., 2018).

### 3.2.2.9. Manganese (Mn).
Mn is an essential element for fish growth and metabolism (Yu et al., 2024). Mn showed its highest average level in *D. labrax* (0.159 ± 0.045 mg/kg ww). These values are in line with those found in Marengo et al. (2018), while higher values were reported in Yildiz (2008). The lowest concentration was found in *P. pagrus* (0.038 ± 0.012 mg/kg ww). Mn was not detected in *P. pagrus* caught from the Northeast Mediterranean, while in the same study, higher values (0.33 ± 0.57 mg/kg) were found at another sampling site in the same region (Korkmaz et al., 2022).

### 3.2.2.10. Cobalt (Co).
Co is an essential element in fish that induces the synthesis of vitamin B12, also known as cobalamin (Blust, 2011). Co was most concentrated in *C. cadenati* (0.005 ± 0.002 mg/kg ww), and lowest in both *S. aurata* and *X. gladius* (0.001 mg/kg ww). Literature values (Table S3) were found in the same range as those found in our specimens, while some studies reported non-detectable (Korkmaz et al., 2022).

### 3.2.2.11. Iron (Fe).
Fe is known for its importance to fish species, owing to its oxygen transport function. Fe is present at low concentrations in natural waters, so fish rely on supplemented feed to meet Fe requirements (Lim et al., 2001). Fe levels peaked in *S. scombrus* (4.922 ± 0.662 mg/kg ww). The values were four times higher than those found in Gambo et al. (2022). The lowest mean was recorded in *X. gladius* (0.482 ± 0.213 mg/kg ww), much lower than values detected in swordfish in the Mediterranean Sea (Di Bella et al., 2020; Gobert et al., 2017).

According to our results, it can be concluded that despite the historical contamination in the Aveiro region, metal concentrations in the muscle tissue of fish caught in this area are considered low. This could be attributed to a decline in industrial discharges, but also to the fact that essential and non-essential trace metals accumulate in metabolically active organs such as the liver and kidneys. These organs are therefore more appropriate than muscle tissue for assessing metal bio-accumulation (Storelli et al., 2005).

## 3.2.3. Focus on *D. labrax* (European sea bass) and *S. aurata* (gilthead sea bream)

The Mediterranean aquaculture of European sea bass and gilthead sea bream has expanded in recent decades (Arechavala-Lopez et al., 2016). In this study, both wild and farmed specimens were sampled and analyzed for these two species. Farmed fish originated in aquaculture in Portugal, Greece, and Türkiye, while wild-caught individuals were sampled from the Aveiro region. To assess whether the geographical origin and production method influence trace element concentrations in fish muscle, a Kruskal-Wallis test was applied.

### 3.2.3.1. *D. labrax* (European sea bass).
For European sea bass, significant differences were found for Fe, Co, and Cu (*p* < 0.05), as well as for Ni, Se, Cd, and Pb (*p* < 0.01). A Dunn post hoc test with Bonferroni correction indicated that fish from Portuguese aquaculture stood out as the most contaminated for Fe, Co, Ni, Cu, and Pb.

Non-significant differences were shown for Cr, Mn, Zn, and As. Specimens from Aveiro (Wild Catch) showed higher concentrations of Se and Cd. In contrast, fish from Greece and Türkiye appeared to be less contaminated overall for these metals. To better understand trace element concentrations observed in farmed *D. labrax*, results from our study were compared with previously published data from aquaculture

systems in Greece, Türkiye, and Portugal (Tables 4 and S4).

The trace element concentrations measured in farmed sea bass from Greece in the present study are in line with values reported in the literature. Essential elements, such as Fe, Zn, and Cu, fell within expected ranges; however, some variations were noted. Compared to Kalantzi et al. (2016), our study reported lower concentrations of Zn (3.052-4.495 mg/kg vs 5.31-6.38), and total As (0.252-0.987 vs 0.42-1.06 mg/kg) in Greek farmed *D. labrax*, while Fe levels remained lower, and Cu levels were slightly higher. Data reported by Fuentes et al. (2010) supported this trend, with Zn, Fe, and Cu values generally consistent with our results. Non-essential elements such as Cd and Pb are also in line with the literature, found below detection limits or in trace amounts in fish muscle.

In Turkish aquaculture, trace element concentrations were generally consistent with those reported in previous studies. Thus, Zn, Cu, and Se levels fell within comparable ranges, except Zn concentrations in our samples, which were extremely lower than the exceptionally high value of 17 mg/kg ww reported in Bat et al. (2022) in fish from Sinop. Moreover, Fe concentrations were also lower than those reported in the same region and Iskenderun (Bat et al., 2022; Varol et al., 2019). As levels were moderated and aligned with the literature. Cd and Pb were undetectable or present in trace amounts in all studies, except for a Cd value of 0.06 mg/kg reported in Ulusoy and Mol (2022), which exceeds the safety limit of 0.05 mg/kg (EC, 2023).

For specimens from Portuguese aquaculture, Fe, Zn, and Cu levels were within the same order of magnitude as those reported by Lourenço et al. (2012) and Fernandes et al. (2009). Slight variations were observed depending on the sampling site, with major variations found for Cu values in the study of Matias et al. (2024), where this element was not detected. Cd and Pb were either undetected or found at very low levels across all studies, including ours, confirming the low contamination levels in the muscle tissue of farmed *D. labrax* in Portugal.

### 3.2.3.2. *S. aurata* (gilthead sea bream).
For gilthead seabream, significant differences were observed for Ni, Cu, As, Se, and Pb (*p* < 0.05). For nickel, farmed fish from Türkiye tended to show higher concentrations than wild specimens from Aveiro. For Cu, As, and Pb, significant differences were observed between farmed fish from Portugal and those from Greece, Türkiye, and wild fish from Aveiro, respectively. In all three cases, fish from Portugal exhibited higher concentrations, indicating a potentially greater exposure to these elements in Portuguese aquaculture environments. To better understand trace element concentrations observed in farmed *S. aurata*, results from our study were also compared with previously published data from aquaculture systems in Greece, Türkiye, and Portugal (Tables 5, S5).

For farmed fish from Greece, Zn and As concentrations were slightly lower than those reported in Kalantzi et al. (2016), while Se concentrations were comparable. Fe concentrations fell in the same range as those reported in the same study. Non-essential elements, Cd and Pb, were either below the detection limit or found in trace amounts, as reported in Renieri et al. (2019). Our values for Cu, Cr, and Mn were quantified contrary to those reported as below detection in Kalantzi et al. (2016).

For those from Turkish aquaculture, Zn concentrations were similar to those reported in other studies; values were lower than those reported in Korkmaz et al. (2022) in fish from Iskenderun and those reported in Canli and Atli (2003). Cu concentrations in our dataset were slightly higher than those of Varol et al. (2019), and comparable with Korkmaz et al. (2022) in Iskenderun, suggesting overall consistency for this essential metal. Fe and As concentrations were lower than those in other studies (cf Table 5), when the elements could be detected in quantified amounts. Cd and Pb were undetectable or present in trace amounts in all studies.

In specimens from Portuguese aquaculture, the Fe average was comparable to all values reported in the literature, with a slight
<caption>**Table 4**</caption>

Metallic trace elements in *D. labrax* reported in this study and the literature. Results are presented as mean ± SD (min-max) and expressed in mg/kg wet weight (ww).

<table><thead><tr><th>Site</th><th>Cr</th><th>Mn</th><th>Fe</th><th>Co</th><th>Ni</th><th>Cu</th><th>Zn</th><th>As</th><th>Se</th><th>Cd</th><th>Pb</th><th></th></tr></thead><tbody><tr><td>Greece</td><td>0.009 ± 0.005<br>(0.001-0.015)</td><td>0.115 ± 0.037<br>(0.087-0.179)</td><td>1.178 ± 0.574<br>(0.761-2.175)</td><td>0.001 ±<br>0 (0.001-0.001)</td><td>0 ±<br>0 (0-0)</td><td>0.247 ± 0.088<br>(0.17-0.366)</td><td>3.634 ± 0.553<br>(3.052-4.495)</td><td>0.545 ± 0.36<br>(0.252-0.987)</td><td>0.149 ± 0.024<br>(0.122-0.168)</td><td>0 ± 0 (0-0)</td><td>0 ± 0 (0-0)</td><td>Our study</td></tr><tr><td>Greece</td><td>0.04-0.06</td><td>-</td><td>Bdl-5.49</td><td>Bdl-0.01</td><td>Bdl-0.19</td><td>Bdl</td><td>5.31-6.38</td><td>0.42-1.06</td><td>0.15-0.2</td><td>Bdl</td><td>Bdl</td><td>(Kalantzi et al., 2016)</td></tr><tr><td>Greece</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>0.001 ± 0</td><td>0.021 ±<br>0.047</td><td>(Renieri et al., 2019)</td></tr><tr><td>Greece</td><td>-</td><td>0.08 ± 0.02</td><td>1.10 ± 0.23</td><td>-</td><td>-</td><td>0.29 ± 0.07</td><td>2.34 ± 0.47</td><td>-</td><td>-</td><td>-</td><td>-</td><td>(Fuentes et al., 2010)</td></tr><tr><td>Türkiye</td><td>0.026 ± 0.046<br>(0.003-0.107)</td><td>0.123 ± 0.017<br>(0.103-0.144)</td><td>0.996 ± 0.565<br>(0.566-1.969)</td><td>0.001 ±<br>0 (0.001-0.001)</td><td>0 ±<br>0 (0-0)</td><td>0.17 ± 0.041<br>(0.116-0.227)</td><td>3.33 ± 0.221<br>(3.085-3.637)</td><td>0.343 ± 0.106<br>(0.24-0.521)</td><td>0.196 ± 0.014<br>(0.18-0.207)</td><td>0 ± 0 (0-0)</td><td>0 ± 0 (0-0)</td><td>Our study</td></tr><tr><td>Türkiye<br>(Iskenderun<br>Bay)</td><td>0.040 ± 0.020</td><td>0.227 ± 0.049</td><td>5.17 ± 3.54</td><td>0.047 ± 0.044</td><td>0.016 ±<br>0.019</td><td>0.20 ± 0.09</td><td>4.25 ± 0.45</td><td>0.61 ± 0.23</td><td>-</td><td>0.0027 ±<br>0.0038</td><td>Bdl</td><td>(Varol et al.,<br>2019)</td></tr><tr><td>Türkiye (Sinop)</td><td>-</td><td>-</td><td>8.5</td><td>-</td><td>-</td><td>0.27</td><td>17</td><td>0.13</td><td>-</td><td>0.012</td><td>0.038</td><td>(Bat et al.,<br>2022)</td></tr><tr><td>Türkiye (Silifke)</td><td>Bdl</td><td>0.24 ± 0.35</td><td>0.01 ± 0.01</td><td>-</td><td>Bdl</td><td>0.10 ± 0.23</td><td>4.62 ± 1.88</td><td>0.52 ± 0.37</td><td>-</td><td>Bdl</td><td>Bdl</td><td>(Korkmaz et al., 2022)</td></tr><tr><td>Türkiye (Aegean<br>Sea)</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>0.24 ± 0.05<br>(0.18-0.34)</td><td>0.06 ±<br>0.12<br>(bdl-0.39)</td><td>0.03 ±<br>0.03<br>(bdl-0.08)</td><td>(Ulusoy and<br>Mol, 2022)</td></tr><tr><td>Türkiye (4<br>aquaculture<br>sites)</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>0.316</td><td>-</td><td>0.021</td><td>0.15</td><td>(Özden<br>et al., 2024)</td></tr><tr><td>Portugal</td><td>0.04 ± 0.054<br>(0.007-0.136)</td><td>0.138 ± 0.026<br>(0.117-0.179)</td><td>2.643 ± 0.703<br>(1.678-3.614)</td><td>0.002 ± 0.001<br>(0.001-0.003)</td><td>0 ±<br>0 (0-0)</td><td>0.473 ± 0.053<br>(0.383-0.525)</td><td>4.229 ± 0.901<br>(3.278-5.526)</td><td>0.425 ± 0.035<br>(0.398-0.487)</td><td>0.162 ± 0.016<br>(0.149-0.189)</td><td>0 ± 0 (0-0)</td><td>0 ± 0 (0-0)</td><td>Our study</td></tr><tr><td>Portugal</td><td>0.31 ± 0.08</td><td>0.30 ± 0.07</td><td>5.0 ± 2.0</td><td>-</td><td>0.04 ±<br>0.02</td><td>0.46 ± 0.10</td><td>5.2 ± 0.4</td><td>-</td><td>-</td><td>-</td><td>-</td><td>(Lourenço<br>et al., 2012)</td></tr><tr><td>South Portugal<br>and Northeast<br>Spain (value<br>reported in dry<br>weight)</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>1.5-3.5</td><td>20-30</td><td>-</td><td>-</td><td>0.16-1.81</td><td>-</td><td>(Fernandes<br>et al., 2009)</td></tr><tr><td>NE Atlantic coast<br>of Portugal</td><td>0.005 ± 0.003</td><td>-</td><td>-</td><td>-</td><td>0.014 ±<br>0.003</td><td>Bdl</td><td>5.542 ± 0.724</td><td>-</td><td>-</td><td>0.003 ±<br>0.002</td><td>Bdl</td><td>(Matias<br>et al., 2024)</td></tr><tr><td>Portuguese pilot<br>facility</td><td>0.010 ± 0.009</td><td>-</td><td>-</td><td>-</td><td>0.020 ±<br>0.004</td><td>Bdl</td><td>3.657 ± 0.045</td><td>-</td><td>-</td><td>0.003 ±<br>0.001</td><td>Bdl</td><td></td></tr></tbody></table>

Bdl: below detection limit.
<table><caption>**Table 5**
Metallic trace elements in *S. aurata* reported in this study and the literature. Results are presented as mean ± SD (min-max) and expressed in mg/kg wet weight (ww).</caption><thead><tr><th>Site</th><th>Cr</th><th>Mn</th><th>Fe</th><th>Co</th><th>Ni</th><th>Cu</th><th>Zn</th><th>As</th><th>Se</th><th>Cd</th><th>Pb</th><th></th></tr></thead><tbody><tr><td>Greece</td><td>0.013 ± 0.014<br>(0.002-0.036)</td><td>0.062 ± 0.026<br>(0.041-0.105)</td><td>1.114 ± 0.853<br>(0.479-2.561)</td><td>0.001 ±<br>0 (0.001-0.001)</td><td>0 ±<br>0 (0-0)</td><td>0.186 ± 0.033<br>(0.146-0.234)</td><td>3.843 ± 0.372<br>(3.251-4.257)</td><td>0.647 ± 0.224<br>(0.412-0.922)</td><td>0.183 ± 0.021<br>(0.151-0.201)</td><td>0 ± 0 (0-0)</td><td>0 ± 0 (0-0)</td><td>Our study</td></tr><tr><td>Greece</td><td>0.05-0.15</td><td>-</td><td>Bdl-2.77</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>4.29-7.02</td><td>0.98-2.99</td><td>0.16-0.23</td><td>Bdl</td><td>Bdl</td><td>(Kalantzi<br>et al.,<br>2016)</td></tr><tr><td>Greece</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>0.001 ±<br>0.001</td><td>0.03 ± 0.042</td><td>(Renieri<br>et al.,<br>2019)</td></tr><tr><td>Türkiye</td><td>0.006 ± 0.005<br>(0.001-0.014)</td><td>0.063 ± 0.014<br>(0.052-0.087)</td><td>1.214 ± 0.622<br>(0.581-2.256)</td><td>0.001 ±<br>0 (0.001-0.001)</td><td>0 ±<br>0 (0-0)</td><td>0.234 ± 0.114<br>(0.138-0.431)</td><td>3.973 ± 0.872<br>(2.957-5.073)</td><td>0.444 ± 0.072<br>(0.358-0.51)</td><td>0.187 ± 0.023<br>(0.166-0.227)</td><td>0.001 ±<br>0.001<br>(0-0.002)</td><td>0 ± 0 (0-0)</td><td>Our study</td></tr><tr><td>Türkiye<br>(Iskenderun<br>Bay)</td><td>0.031 ± 0.014</td><td>0.127 ± 0.026</td><td>2.73 ± 1.7</td><td>0.015 ± 0.017</td><td>0.065 ±<br>0.059</td><td>0.15 ± 0.04</td><td>4.72 ± 0.5</td><td>1.13 ± 0.3</td><td>-</td><td>0.0036 ±<br>0.0025</td><td>0.006 ±<br>0.013</td><td>(Varol<br>et al.,<br>2019)</td></tr><tr><td>Türkiye<br>(values<br>reported in<br>dry weight)</td><td>1.24 ± 0.46</td><td>-</td><td>19.60 ± 7.84</td><td>2.84 ± 0.43</td><td>-</td><td>-</td><td>26.66 ± 7.62</td><td>-</td><td>-</td><td>0.37 ± 0.11</td><td>5.54 ± 0.74</td><td>(Canli and<br>Atli, 2003)</td></tr><tr><td>Türkiye<br>(Iskenderun)</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>0.24 ± 0.41</td><td>6.2 ± 1.9</td><td>0.69 ± 0.1</td><td>-</td><td>Bdl</td><td>Bdl</td><td>(Korkmaz<br>et al.,<br>2022)</td></tr><tr><td>Türkiye<br>(Silifke)</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>2.98 ± 0.86</td><td>0.57 ± 0 0.08</td><td>-</td><td>Bdl</td><td>Bdl</td><td></td></tr><tr><td>Türkiye<br>(Antalya)</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>Bdl</td><td>0.43 ± 0.41</td><td>4.51 ± 1.25</td><td>0.61 ± 0.31</td><td>-</td><td>Bdl</td><td>Bdl</td><td></td></tr><tr><td>Portugal</td><td>0.035 ± 0.028<br>(0.008-0.068)</td><td>0.07 ± 0.017<br>(0.058-0.099)</td><td>2.089 ± 0.832<br>(1.431-3.503)</td><td>0.002 ± 0.001<br>(0.001-0.003)</td><td>0 ±<br>0 (0-0)</td><td>0.428 ± 0.249<br>(0.237-0.865)</td><td>3.808 ± 0.758<br>(3.017-4.764)</td><td>0.971 ± 0.262<br>(0.516-1.165)</td><td>0.25 ± 0.022<br>(0.225-0.279)</td><td>0 ±<br>0 (0-0.001)</td><td>0.025 ±<br>0.055<br>(0-0.124)</td><td>Our study</td></tr><tr><td>Portugal (Earth<br>ponds-<br>Olhão)</td><td>0</td><td>0-0.790</td><td>3.207-48.519</td><td>-</td><td>0-0.313</td><td>0.140-0.871</td><td>7.678-15.488</td><td>0.260-8.323</td><td>0.360-0.565</td><td>-</td><td>0.127-2.065</td><td>(Mamede<br>et al.,<br>2022)</td></tr><tr><td>Portugal (sea<br>cage-Olhão)</td><td>0</td><td>0-0.446</td><td>2.150-55.494</td><td>-</td><td>0-0.475</td><td>0.248-1.139</td><td>7.400-18.369</td><td>1.322-3.729</td><td>0.321-0.498</td><td>-</td><td>0-1.113</td><td></td></tr><tr><td>Portugal (sea<br>cage-<br>Madeira)</td><td>0-0.547</td><td>0-0.350</td><td>1.841-49.487</td><td>-</td><td>0</td><td>0.335-1.081</td><td>6.502-13.386</td><td>0.746-2.455</td><td>-</td><td>-</td><td>0-0.605</td><td></td></tr><tr><td>Portugal</td><td>0.31 ± 0.14</td><td>0.14 ± 0.02</td><td>4.8 ± 3.0</td><td>-</td><td>0.04 ±<br>0.02</td><td>0.71 ± 0.17</td><td>4.9 ± 1.0</td><td>-</td><td>-</td><td>-</td><td>-</td><td>(Lourenço<br>et al.,<br>2012)</td></tr></tbody></table>

Bdl: below detection limit.
<caption>Table 6</caption>

Estimation of non-carcinogenic safe consumption limit (SCLnc) for an adult (70 kg) based on the concentration of metallic trace elements found in samples. Results are presented as mean ± SD (min-max) and expressed in kg fish (ww)/day.

<table><caption>SCLnc Safe consumption limit (kg of fish in ww) for an adult of 70 kg</caption><thead><tr><th>Scientific name</th><th>Fishing type</th><th>Cr</th><th>Mn</th><th>Fe</th><th>Ni</th><th>Cu</th><th>Zn</th><th>Cd</th><th>Pb</th><th>Se</th></tr></thead><tbody><tr><td>Cynoglossus cadenati</td><td>Wild</td><td>30.7 ± 30.5<br>(6.1-82.6)</td><td>110.6 ± 39.1<br>(56.2-165.5)</td><td>51 ± 16.9<br>(35.3-79)</td><td>1,374,889.6 ± 44,773.1<br>(1,342,281.9-1,450,777.2)</td><td>26.1 ± 8<br>(19.6-38.8)</td><td>5.5 ± 0.6<br>(4.9-6.5)</td><td>1463.4 ± 3237<br>(1.5-7253.9)</td><td>274,977.9 ± 8954.6<br>(268,456.4-290,155.4)</td><td>0.5 ± 0.1<br>(0.4-0.6)</td></tr><tr><td>Dicentrarchus labrax</td><td>Aquaculture</td><td>35.4 ± 47.4<br>(1.5-190.9)</td><td>81.4 ± 17<br>(54.7-112.3)</td><td>42.2 ± 23.2<br>(13.6-86.6)</td><td>1,092,980.9 ± 89,174.6<br>(954,328.6-1,268,115.9)</td><td>11.9 ± 5.8<br>(3.8-6.9)</td><td>5.8 ± 0.9<br>(3.8-6.9)</td><td>5464.9 ± 445.9<br>(4771.6-6340.6)</td><td>218,596.2 ± 17,834.9<br>(190,865.7-253,623.2)</td><td>2.1 ± 0.4<br>(1.7-2.9)</td></tr><tr><td>Dicentrarchus labrax</td><td>Wild</td><td>15 ± 2.6<br>(10.8-17.8)</td><td>66.5 ± 22.8<br>(47.1-103.4)</td><td>34.4 ± 17.8<br>(18.6-58.5)</td><td>1,178,652.5 ± 85,274.6<br>(1,099,764.3-1,320,132)</td><td>11.6 ± 6.8<br>(5.8-21.1)</td><td>5.1 ± 1.2<br>(3.3-6.5)</td><td>1104.3 ± 2456.6<br>(3.5-5498.8)</td><td>235,730.5 ± 17,054.9<br>(219,952.9-264,026.4)</td><td>1.3 ± 0.1<br>(1.2-1.5)</td></tr><tr><td>Helicolenus ducalipters</td><td>Wild</td><td>75.7 ± 53.8<br>(15.9-120.1)</td><td>221.6 ± 41.6<br>(176.3-258.2)</td><td>63.6 ± 18.5<br>(44.1-81.1)</td><td>1,422,369.6 ± 26,353.1<br>(1,393,034.8-1,444,043.3)</td><td>38.1 ± 15<br>(23.5-53.5)</td><td>9.2 ± 1.3<br>(8.2-10.7)</td><td>4.8 ± 2.9<br>(1.4-6.8)</td><td>284,473.9 ± 5270.6<br>(27860.7-888.07)</td><td>0.9 ± 0.1<br>(0.8-0.9)</td></tr><tr><td>Pagrus pagrus</td><td>Wild</td><td>24.8 ± 16.1<br>(5.3-43.1)</td><td>282.5 ± 93.5<br>(187.7-411.5)</td><td>33.6 ± 11.6<br>(19.2-45)</td><td>1,280,216.5 ± 39,666.3<br>(1,232,394.4-1,336,515.5)</td><td>23.1 ± 3.4<br>(19.2-27.8)</td><td>9.2 ± 1.3<br>(6.8-11.4)</td><td>1.3 ± 0.8<br>(0.5-2.6)</td><td>256,043.3 ± 7933.3<br>(246,478.9-267,303.1)</td><td>0.8 ± 0.1<br>(0.6-0.9)</td></tr><tr><td>Scomber scombrus</td><td>Wild</td><td>13.6 ± 7.4<br>(8.3-26.5)</td><td>173.2 ± 31.8<br>(122.8-210.6)</td><td>10.1 ± 1.3<br>(8.3-12)</td><td>1,199,499.7 ± 96,317.6<br>(1,084,010.8-1,325,130.1)</td><td>9.2 ± 1.3<br>(7.6-11)</td><td>9.6 ± 1.4<br>(7.2-10.8)</td><td>4749.2 ± 2689.9<br>(8.4-6625.7)</td><td>239,899.9 ± 19,263.5<br>(216,802.2-265,026)</td><td>1.1 ± 0.1<br>(1.1-1.3)</td></tr><tr><td>Sparus aurata</td><td>Aquaculture</td><td>44 ± 67.8<br>(3.1-272.3)</td><td>161.1 ± 39.8<br>(93.3-239)</td><td>45.6 ± 27<br>(14-102.4)</td><td>1,051,899.2 ± 63,185.3<br>(884,396.7-1,130,399.7)</td><td>12.3 ± 4.8<br>(3.2-20.3)</td><td>5.6 ± 0.9<br>(4.1-7.1)</td><td>4221.5 ± 2202.2<br>(3.3-5652)</td><td>181,199.9 ± 74,522<br>(2.3-226,079.9)</td><td>1.7 ± 0.3<br>(1.3-2.3)</td></tr><tr><td>Sparus aurata</td><td>Wild</td><td>21 ± 16.8<br>(5.4-48.5)</td><td>174.5 ± 27.4<br>(149.2-215)</td><td>35.9 ± 15.6<br>(22.7-62.2)</td><td>1,158,913.8 ± 71,485.1<br>(1,106,719.4-1,280,292.6)</td><td>12.3 ± 5.1<br>(8.6-21.1)</td><td>6.6 ± 1.5<br>(4.7-8.8)</td><td>1224.8 ± 2414<br>(3.6-5535.8)</td><td>231,782.8 ± 14,297<br>(221,343.9-256,058.5)</td><td>1.8 ± 0.4<br>(1.3-2.2)</td></tr><tr><td>Trachurus trachurus</td><td>Wild</td><td>19.8 ± 14<br>(6.1-40.2)</td><td>135.8 ± 36.3<br>(93-184.7)</td><td>11.9 ± 3.8<br>(7.4-16.1)</td><td>1,309,856.6 ± 27,820.3<br>(1,281,464.5-1,353,310.8)</td><td>8.9 ± 3<br>(4.8-12.5)</td><td>7.7 ± 1.3<br>(6.4-9.7)</td><td>21.7 ± 42.4<br>(0.8-97.4)</td><td>207,841.1 ± 116,212.1<br>(11.1-263,902)</td><td>1. ± 0.1<br>(0.9-1.3)</td></tr><tr><td>Xiphias gladius</td><td>Wild</td><td>29.7 ± 27.1<br>(7.7-59.9)</td><td>126.8 ± 31.3<br>(95.9-158.5)</td><td>122.2 ± 69.9<br>(75.2-202.5)</td><td>978,975.9 ± 847,516.7<br>(358-1,472,134.6)</td><td>33.1 ± 6.1<br>(27.6-39.6)</td><td>8.8 ± 0.5<br>(8.2-9.1)</td><td>2.8 ± 1.7<br>(0.9-4.2)</td><td>294,068.7 ± 1049.4<br>(292887-294,892)</td><td>0.8 ± 0.1<br>(0.7-0.8)</td></tr></tbody></table>

difference, except that the values in Lourenço et al. (2012) were reported to be higher. For Mn, Cr, Ni, and Zn results in our dataset were found to be lower than those in other studies. As levels remained below levels of concern and were lower than some values in Mamede et al. (2022) (up to 8.3 mg/kg) for fish from different farming systems, while Se was relatively stable and aligned with expected ranges. In our study, Cd was either undetectable or found in trace amounts. Pb concentration (0.025 ± 0.055 mg/kg) was lower than those reported in other studies and below regulatory limits.

In our study, differences in Cu and Se between farmed and wild fish were not consistent across species. For *D. labrax*, Se concentrations were higher in wild individuals, which can be explained by higher concentrations in the aquatic environment, whereas Cu was higher in aquaculture fish from Portugal. In contrast, for *S. aurata*, both Cu and Se were higher in aquaculture fish. These patterns suggest that diet composition in aquaculture may partly influence Cu and Se accumulation, although species-specific physiology and environmental factors likely also play a role (Marengo et al., 2018).

The observed variations in metal concentrations within the same fish species, even between geographically close regions, may underscore the influence of multiple factors. Water quality (salinity, pH) and source (from dams, rivers, treated wastewater) can affect the concentration and the bioavailability of trace elements (Emenike et al., 2022).

Additionally, fish feed composition plays a major role in some aquaculture systems, such as in pond-based systems, where feed is a combination of natural and manufactured food (Mamede et al., 2022). Furthermore, aquaculture infrastructure can be a source of contamination. In some systems, cages and nets are coated with copper-based material to prevent biofouling (Guardiola et al., 2012).

In marine systems, sediments are a key reservoir of MTEs, which can be suspended, transported, and released into the water, and subsequently ingested by the aquatic organisms through the food web, direct ingestion of sediments, or uptake from the water (Zhang et al., 2017; Naz et al., 2023). This explains why demersal species feeding near the bottom often accumulate higher levels of sediment-associated elements such as As (Zhang and Wang, 2012).

Dietary exposure is also considered an important pathway for metal uptake, in high-trophic-level species and can reflect biomagnification of MTEs (Oros, 2025). Javanshir Khoei (2023) has demonstrated that in both pelagic and demersal fish, MTEs concentrations in muscles were significantly higher in carnivorous and euryphagous species than in herbivorous and phytoplanktivorous fishes. Age can also affect MTEs in fish (Brázová et al., 2025); older fish can often show higher levels due to prolonged exposure, although contradictory conclusions have also been reported depending on species and metals (Has-Schön et al., 2015). The accumulation of heavy metals, whether non-essential or essential above tolerable limits, in organs such as the liver, kidneys, gills, and muscles reflects failures in detoxification mechanisms and can lead to pathological tissue alterations (Shahjahan et al., 2022).

### 3.3. Safe consumption limit (SCLnc)

The SCLnc values were calculated individually per sample and metal, origin, to estimate the daily quantity (in kg) of fish muscle that can be safely consumed by adults (70 kg) and children (15 kg) without inducing non-carcinogenic health effects (Tables S6 and S7). The most restrictive SCLnc values were associated with Cd and Pb, both non-essential elements, and Se, an essential trace element. For Cd, the lowest SCLnc was found for the wild *P. pagrus* sample (PD-W-PP 3), at 0.5 kg/day for adults, and 0.1 kg/day (100 g) for children. For Pb, the lowest SCLnc values were 2.26 kg/day for adults and 0.48 kg/day for children, found in a farmed sample of *S. aurata* from Portugal (CN-AP-SA 1). Regarding Se, the lowest SCLnc values were observed in *C. cadenati* (PD-W-CC 3), with 0.4 and 0.08 kg/day, for adults and children, respectively.

Mean SCLnc values by species are presented in Tables 6 and 7. Overall, Se appeared to be the most limiting element, with low
<caption>Table 7</caption>

Estimation of non-carcinogenic safe consumption limit (SCLnc) for children (15 kg) based on the concentration of metallic trace elements found in samples. Results are presented as mean ± SD (min-max) and expressed in kg fish (ww)/day.

<table><caption>SCLnc Safe consumption limit (kg of fish in ww) for children of 15 Kg</caption><thead><tr><th>Scientific name</th><th>Fishing type</th><th>Cr</th><th>Mn</th><th>Fe</th><th>Ni</th><th>Cu</th><th>Zn</th><th>Cd</th><th>Pb</th><th>Se</th></tr></thead><tbody><tr><td>Cynoglossus cadenati</td><td>Wild</td><td>6.6 ± 6.5<br>(1.3-17.7)</td><td>23.7 ± 8.4<br>(12-35.5)</td><td>10.9 ± 3.6<br>(7.6-16.9)</td><td>294,619.2 ± 9594.2<br>(287,631.8-310,880.8)</td><td>5.7 ± 1.7<br>(4.2-8.3)</td><td>1.2 ± 0.1<br>(1.1-1.4)</td><td>313.6 ± 693.6<br>(0.3-1554.4)</td><td>58,923.8 ± 1918.8<br>(57,526.4-62,176.2)</td><td>0.1 ± 0<br>(0.1-0.1)</td></tr><tr><td>Dicentrarchus labrax</td><td>Aquaculture</td><td>7.6 ± 10.2<br>(0.3-40.9)</td><td>17.4 ± 3.6<br>(11.7-24.1)</td><td>9 ± 5<br>(2.9-18.6)</td><td>234,210.2 ± 19,108.8<br>(204499-271,739.1)</td><td>2.6 ± 1.2<br>(1.1-5.2)</td><td>1.2 ± 0.2<br>(0.8-1.5)</td><td>1171.1 ± 95.5<br>(1022.5-1358.7)</td><td>46,842 ± 3821.8<br>(40,899.8-54,347.8)</td><td>0.5 ± 0.1<br>(0.4-0.6)</td></tr><tr><td>Dicentrarchus labrax</td><td>Wild</td><td>3.2 ± 0.6<br>(2.3-3.8)</td><td>14.3 ± 4.9<br>(10.1-22.2)</td><td>7.4 ± 3.8<br>(4-12.5)</td><td>252,568.4 ± 18,273.1<br>(235,663.8-282,885.4)</td><td>2.5 ± 1.5<br>(1.2-4.5)</td><td>1.1 ± 0.3<br>(0.7-1.4)</td><td>236.6 ± 526.4<br>(0.8-1178.3)</td><td>50,513.7 ± 3654.6<br>(47,132.8-56,577.1)</td><td>0.3 ± 0<br>(0.3-0.3)</td></tr><tr><td>Helicolensius dactylopterus</td><td>Wild</td><td>16.2 ± 11.5<br>(3.4-25.7)</td><td>47.5 ± 8.9<br>(37.8-55.3)</td><td>13.6 ± 4<br>(9.5-17.4)</td><td>304,793.5 ± 5647.1<br>(298,507.5-309,437.9)</td><td>8.2 ± 3.2<br>(5-11.5)</td><td>2 ± 0.3<br>(1.8-2.3)</td><td>1 ± 0.6<br>(0.3-1.5)</td><td>60,958.7 ± 1129.4<br>(59,701.5-61,887.6)</td><td>0.2 ± 0<br>(0.2-0.2)</td></tr><tr><td>Pagrus pagrus</td><td>Wild</td><td>5.3 ± 3.5<br>(1.1-9.2)</td><td>60.5 ± 20<br>(40.2-88.2)</td><td>7.2 ± 2.5<br>(4.1-9.6)</td><td>274,332.1 ± 8499.9<br>(264,084.5-286,396.2)</td><td>4.9 ± 0.7<br>(4.1-6)</td><td>2 ± 0.4<br>(1.5-2.4)</td><td>0.3 ± 0.2<br>(0.1-0.6)</td><td>54,866.4 ± 1700<br>(52,816.9-57,279.2)</td><td>0.2 ± 0<br>(0.1-0.2)</td></tr><tr><td>Scomber scombrus</td><td>Wild</td><td>2.9 ± 1.6<br>(1.8-5.7)</td><td>37.1 ± 6.8<br>(26.3-45.1)</td><td>2.2 ± 0.3<br>(1.8-2.6)</td><td>257,035.6 ± 20,639.5<br>(232288-283,956.5)</td><td>2 ± 0.3<br>(1.6-2.4)</td><td>2.1 ± 0.3<br>(1.5-2.3)</td><td>1017.7 ± 576.4<br>(1.8-1419.8)</td><td>51,407.1 ± 4127.9<br>(46,457.6-56,791.3)</td><td>0.2 ± 0<br>(0.2-0.3)</td></tr><tr><td>Sparus aurata</td><td>Aquaculture</td><td>9.4 ± 14.5<br>(0.7-58.4)</td><td>34.5 ± 8.5<br>(20-51.2)</td><td>9.8 ± 5.8<br>(3-21.9)</td><td>225,407 ± 13,539.7<br>(189,513.6-242,228.5)</td><td>2.6 ± 1<br>(0.7-4.3)</td><td>1.2 ± 0.2<br>(0.9-1.5)</td><td>904.6 ± 471.9<br>(0.7-1211.1)</td><td>38,828.5 ± 15,969<br>(0.5-48,445.7)</td><td>0.4 ± 0.1<br>(0.3-0.5)</td></tr><tr><td>Sparus aurata</td><td>Wild</td><td>4.5 ± 3.6<br>(1.2-10.4)</td><td>37.4 ± 5.9<br>(32-46.1)</td><td>7.7 ± 3.3<br>(4.9-13.3)</td><td>248,388.7 ± 15,318.2<br>(237,154.2-274,348.4)</td><td>2.6 ± 1.1<br>(1.8-4.5)</td><td>1.4 ± 0.3<br>(1-1.9)</td><td>262.5 ± 517.3<br>(0.8-1186.2)</td><td>49,667.7 ± 3063.6<br>(47,430.8-54,869.7)</td><td>0.4 ± 0.1<br>(0.3-0.5)</td></tr><tr><td>Trachurus trachurus</td><td>Wild</td><td>4.2 ± 3<br>(1.3-8.6)</td><td>29.1 ± 7.8<br>(19.9-39.6)</td><td>2.6 ± 0.8<br>(1.6-3.4)</td><td>280,683.5 ± 5961.5<br>(274,599.5-289,995.2)</td><td>1.9 ± 0.7<br>(1-2.7)</td><td>1.7 ± 0.3<br>(1.4-2.1)</td><td>4.7 ± 9.1<br>(0.2-20.9)</td><td>44,537.4 ± 24,902.6<br>(2.4-56,550.4)</td><td>0.2 ± 0<br>(0.2-0.3)</td></tr><tr><td>Xiphias gladius</td><td>Wild</td><td>6.4 ± 5.8<br>(1.6-12.8)</td><td>27.2 ± 6.7<br>(20.5-34)</td><td>26.2 ± 15<br>(16.1-43.4)</td><td>209,780.6 ± 181,610.7<br>(76.7-315,457.4)</td><td>7.1 ± 1.3<br>(5.9-8.5)</td><td>1.9 ± 0.1<br>(1.8-1.9)</td><td>0.6 ± 0.4<br>(0.2-0.9)</td><td>63,014.7 ± 224.9<br>(62,761.5-63,191.2)</td><td>0.2 ± 0<br>(0.1-0.2)</td></tr></tbody></table>

maximum safe consumption levels of 0.5 kg/day for adults (X. gladius) and 0.1 kg/day (C. cadenati). For Cd and Pb, safe limits were generally below 1.5 kg/day for adults and 0.5 kg for children. All other elements showed higher tolerable limits, indicating lower potential risk from fish muscle consumption. In Portugal, the average daily consumption of fish is around 44 g for adults and 25 g for children, respectively (Lopes et al., 2018). Therefore, based on these estimates, the local population in the Aveiro region is unlikely to be at risk of non-carcinogenic effects from fish consumption if consistent with the national level.

### 3.4. MPI

The MPI is used to classify the degree of contamination as low (MPI <1), initial (MPI = 1), or increasing (MPI > 1) (Fahmy et al., 2023). In this study, all MPI values were below 1 (Table S8), suggesting a low level of metal contamination in the Aveiro region where the fish were caught. However, the absence of elevated MPI values (>1) should not be interpreted as evidence of an uncontaminated environment. Given the unknown capture locations and the spatial variability of pollution in estuarine systems like the Ria de Aveiro, it remains possible that certain areas present higher levels of contamination and were not reflected in our samples.

MPI was calculated excluding mercury (Hg), a key contaminant of the Aveiro region, linked to industrial discharges. Additionally, our analysis focused on fish muscle, which tends to accumulate lower metal concentrations compared to other organs, such as the liver and kidneys. It is also worth noting that the fish were caught in the surrounding region of Aveiro and sold in the fish market. Therefore, the MPI evaluation represents a general screening of the contamination situation, without specific information about the capture sites near pollution hotspots.

## 4. Conclusion

According to the findings in our study, metallic trace elements in the most consumed fish species in the Aveiro region were all within the expected ranges in wild and farmed specimens. Non-essential (Cd, Pb) elements were detected at low levels in most samples, below European regulatory thresholds. In addition, the metal pollution index (MPI) for wild-caught fish was low, indicating generally low levels of metal contamination in fish available in Aveiro markets. Significant differences were observed between species, origins, morphometric and MTEs concentrations, with some farmed fish showing elevated levels. Risk assessment based on SCLnc indicated that, under current dietary habits, the health risk for the local population remains low.

Further studies should focus on metabolically active organs (liver, gills) and environmental compartments (sediments, water) to understand exposure pathways. Additionally, monitoring other contaminants such as persistent organic pollutants is crucial due to their high affinity to fat content (Ho et al., 2023). Cooking practices and consumption habits (quantity, frequency) should be considered, as they can influence metal bioavailability, uptake, and exposure (Ersoy et al., 2006). Finally, cross-referencing environmental and dietary data with human biomonitoring (e.g., blood or hair analyses) and stress biomarkers in fish would allow a more comprehensive assessment of health risks and support the development of targeted public health recommendations.

### CRediT authorship contribution statement

**Nathalie El Deghel:** Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Hugo C. Vieira:** Writing – review & editing, Methodology, Investigation, Conceptualization. **Maria D. Bordalo:** Writing – review & editing, Methodology, Investigation, Conceptualization. **Steve Peuble:** Writing – review & editing, Investigation. **Frederic Gallice:** Writing – review & editing, Investigation. **Jean-Philippe Bedell:** Writing – review & editing, Formal analysis, Conceptualization.
## Funding sources

This work was carried out within the framework of the OHMi-Estarreja and the project "Can I Eat This Fish?" that benefited from state funding managed by the French National Research Agency under the LabEx DRIIHM "Investing in the Future Program" (reference # ANR-11-LABX-0010) and by national funds through FCT – Fundação para a Ciência e a Tecnologia I.P., under the project/grant UID/50006 + LA/P/0094/2020 (doi.org/10.54499/LA/P/0094/2020).

Analytical work was conducted in collaboration with the Spectroscopy and Chemical Analyses platform at Mines Saint-Étienne, École de l'Institut Mines-Télécom, 158 cours Fauriel, 42023 Saint-Étienne, France.

Nathalie El Deghel's thesis was funded by the research direction of ENTPE.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgments

We sincerely thank the students who contributed to sampling for their hard work and assistance in collecting samples.

We also extend our thanks to the OHMi Estarreja, part of the SASI project (*Système alimentaire Sous Influence*), supported by the French National Research Agency under the LabEx DRIIHM "Investing in the Future Program" (reference # ANR-11-LABX-0010), for its scientific and logistical support. The collaboration with the "Can I Eat This Fish?" project was made possible through the SASI project, and in particular through the support of OHMi Estarreja.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.marpolbul.2025.118774.

## Data availability

Data will be made available on request.

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