The levels of Hg, Cd, Pb, Cr, Cu and Zn were measured in the tissues of four edible fish species namely: Diplodus annularis, Pagellus erythrinus, Merluccius merluccius and Mullus barbatus, collected from the Turkish Coast of the Aegean Sea. Except for D. annularis, the levels of Cd and Pb in all fish tissues sampled in Aliaga Bay in 2009 were above the tolerable limits according to the Food and Agriculture Organization of the United Nations (FAO). Hg in P. erythrinus and M. barbatus were higher than the maximum permitted limits (FAO), while D. annularis and M. merluccius were lower than the limit for biota in the district of Aliaga. Although the Target Hazard Quotient (THQ) values for Cd, Pb, Cu, Cr, Zn in all fish samples were lower than 1.0, the THQ for Hg levels were higher than 1.0 for most of the samples. According to the THQ values, M. merluccius may be consumed in moderation from Aliaga Bay, while the consumption of M. barbatus and P. erythrinus collected from Aliaga Bay are potentially hazardous to human health due to the Hg concentrations. Fish collected from Izmir Bay can be consumed safely.

The concentrations of polychlorinated biphenyl (PCB) congeners were examined in two fish species from the Izmir Bay. A total of 624 individuals of different fish samples were sampled by trawling from three regions in Izmir Bay between 2010 and 2013. The total levels of indicator PCBs in all samples varied LOD (limit of detection) to 34.3 ng g⁻¹ (dry weight) in the study area. The highest concentrations of PCBs were found in Gulbahce for Mullus barbatus and Diplodus annularis in 2011 and 2010, respectively. PCB153 was the major contributed congener in both fish species during sampling periods. Principal component analysis (PCA) was performed to evaluate the correlation of the determined variables in fish species. According to PCA, the PCBs are not related with fish length. One-way ANOVA test indicated that significant temporal variations were generally detected for PCBs, while non-significant spatial variations were examined between sampling sites. Six PCB congeners were found as 0.59–6.64 ng g⁻¹ (wet weight, wwt) and compared with iPCB6 limits of 75 ng g⁻¹ (wwt) revealed by the Environmental Food Safety Authority. Accordingly, all fish species analyzed did not surpass the safe limits of iPCB6 suggested by EU. The estimated daily intake of 6 PCB congeners by the people were less than the tolerable daily intake (TDI, 10-ng kg⁻¹ body weight day⁻¹) recommended by WHO (2003), suggesting that this intake would not cause adverse effects to residents of Izmir.

The concentrations of heavy metals (Cd, Cu, Fe, Pb, Ni, and Zn) were measured in the liver, gills, and muscle of Solea vulgaris, Liza aurata, and Diplodus annularis, collected from the south coast of Sfax (Gabes Gulf, southwestern Mediterranean). The concentrations of heavy metals in water exhibited the following decreasing order (expressed in μg l⁻¹): Fe > Ni > Zn > Cu > Pb > Cd whereas the trend is somewhat different in sediments (mg kg⁻¹ D.W.) Fe > Zn > Pb > Ni > Cu > Cd. The levels of heavy metals varied significantly among fish species and tissues. Heavy metal levels were found generally higher in the liver and gills than the muscle in all species. The liver was the target organ for Cd, Cu, Fe, Ni, and Zn accumulation. Nickel and lead, however, exhibited their highest concentrations in the gills. The three studied fishes showed a difference in metals accumulation decreasing in following order S. vulgaris > D. annularis > L. aurata. Solea vulgaris with the highest TFwₐₜₑᵣ, TFₛₑdᵢₘₑₙₜ, and metal concentrations in tissues would be considered as a potential bio-indicator in the south coast of Sfax for the assessment of environmental pollution status. Comparative studies with Luza zone indicate considerable bioaccumulation of heavy metals (Pb and Zn) in the various tissues of fish samples of the south coast of Sfax.

Organochlorine (OCs) concentrations were measured in two fish species, Mullus barbatus and Diplodus annularis, collected from Izmir Gulf during 2009–2012 in order to explain the status of these contaminants in edible fish. No data is available on the levels of organochlorines in marine organism from Izmir Gulf. In both fish species from the study area, Aroclors were determined in higher concentrations than organochlorine pesticides (OCPs). Maximum concentrations of OCPs and PCBs measured in the edible part of D. annularis were 45–165 and 530–1591 ng g⁻¹ lipid weight (lw), respectively. DDTs (sum of DDT and metabolites) and cyclodienes ranged from 4–56 to 16–110 ng g⁻¹ lw, respectively. The levels of DDTs measured in the present study were generally comparable or lower than those found in studies from other Mediterranean and non-Mediterranean regions. The potential risks for fish consumers were assessed. Although the estimated daily intake (EDI) for DDTs, heptachlor, and drins through the sampled fish species by Izmir inhabitants was quite lower than the ADI (acceptable daily intake) established by the FAO/WHO, EDI for Aroclor 1254 was close to the ADI value of 20 ng g⁻¹ recommended by the IPCS (2000).

A wide variety of contaminants in the aquatic environment causes several deleterious effects on aquatic organism traits ranging from molecular to individual and population levels. This in situ study investigated morphometry, growth performance, and reproduction success of a teleost fish, Diplodus annularis, from a polluted site “Sayada” and a reference site “Salakta” in the eastern Tunisian coastline. Morphometric indexes, generalized Procruste analysis, thin plate, and otolith contour methods were used to assess the pollution effects on morphological traits. The growth performance of fish from contaminated and control sites were studied using the Von Bertalanffy equation. Gonadosomatic (GSI) and Hepatosomatic (HSI) Indexes and absolute and relative fecundity were used to assess the impact of pollution on the reproduction success of this species. The obtained results showed that the fish of the contaminated zone had significant alteration of the morphology, slower growth, significant increase in the HSI, significant decrease in female GSI, and a decrease in absolute and relative fecundity compared to specimens from the unpolluted zone. Based on these results, the biological traits of Diplodus annularis can be used as biological biomarkers in the monitoring and protection programs of the marine contamination in the Mediterranean Sea.