Monitoring and Assessment of Heavy Metal Concentrations in Two Black Fish Species, Capoeta saadii (Heckel, 1847) and Capoeta trutta (Heckel, 1843), in Western Iran.

Contamination of aquatic ecosystems with heavy metals poses a significant global issue due to its hazardous effects and persistent accumulation in living organisms. This study analyzed 51 fish samples from two species of Black Fish, Capoeta saadii and Capoeta trutta, collected from Iran's Khorramroud River during the summer and fall of 2022 to assess heavy metal accumulation in their gill, liver, and muscle tissues. After biometry, the studied tissues of each fish were isolated to measure the concentration of heavy metals (cadmium (Cd), zinc (Zn), chromium (Cr), lead (Pb), copper (Cu), and nickel (Ni)). The tissue concentration of the studied metals was obtained by measuring in the inductively coupled plasma optical emission spectroscopy (ICP-OES) device after chemical digestion. Based on the results of this study, muscle and liver tissues had the lowest and highest accumulation of heavy metals, respectively, with zinc concentration in the liver of C. saadii reaching 118.557 mg/kg, which exceeds the permissible limit of 75 mg/kg. Also, there was no significant correlation between the amount of absorption of heavy elements and the biometric indicators of body weight and length. Although C. saadii accumulated higher levels of Zn, Cu, Cd, and Cr than C. trutta, statistical analysis (ANOVA and PCA) revealed no significant differences in heavy metal accumulation between the two species (P > 0.05). Comparisons with international standards indicated that chromium (2.10-9.97 mg/kg) and zinc concentrations (41.72-118.557 mg/kg) exceeded permissible limits, while Ni, Cu, Pb, and Cr levels remained below the allowable thresholds. These findings underscore the need for strategic planning, management, and continuous environmental monitoring to mitigate heavy metal pollution in aquatic ecosystems and safeguard the health of fish populations in the Khorramroud River.