Interspecific and Size-related Differences in Cadmium Accumulation in Gill Tissues of Three Marine Fish Species from the Adriatic Sea (Albania)

Abstract

Background: Fish gills, due to their direct contact with water, represent a primary site of metal uptake and are sensitive indicators of environmental metal exposure. This study aimed to quantify cadmium (Cd) concentrations in the gill tissues of three ecologically and commercially important marine fish species (Solea solea, Dicentrarchus labrax and Mugil cephalus) collected from the Adriatic Sea near the Ishëm River estuary (Albania) and to evaluate interspecific and size-related differences in cadmium accumulation. Methods: Fish samples were collected between February and April 2023 and classified into juvenile ( less than 150 g) and adult ( greater than 150 g) size classes. Cadmium concentrations in gill tissues, seawater and marine sediments were determined by graphite furnace atomic absorption spectrometry (GFAAS). Statistical analyses were performed using heteroskedasticity-robust linear models (HC3), robust Wald tests, Welch’s tests and Games-Howell post hoc comparisons. Result: Cadmium concentrations in seawater were below the limit of quantification ( less than 0.07 µg/L), whereas marine sediments contained measurable Cd concentrations (50±5.4 µg/kg dry weight). Significant interspecific differences in gill Cd concentrations were observed, with Solea solea exhibiting the highest concentrations, Mugil cephalus intermediate concentrations and Dicentrarchus labrax the lowest overall concentrations. Although the overall effect of fish size was not significant, size-related differences varied among species, resulting in a significant species × size interaction. These findings demonstrate that fish gills are sensitive biomarkers of cadmium exposure and provide baseline data for future environmental monitoring of the Adriatic coastal ecosystem influenced by riverine pollution.