Metal accumulation and health risk assessment in the anadromous fish Tenualosa ilisha across riverine, estuarine, and marine habitats of Bangladesh.

The concentrations of heavy metals (Cd, Zn, Mn, Fe, Cu, Ni, Cr, and Pb) were analyzed in the muscle and gut of hilsa shad (Tenualosa ilisha) from 36 samples collected across six sites (two riverine, two estuarine, and two marine) in Bangladesh using Flame Atomic Absorption Spectrometry. Metal accumulation showed clear tissue- and habitat-specific variation, with higher levels in the gut. Fe was dominant in both muscle (108.37 ± 107.62 mg/kg, ww) and gut (878.86 ± 380.22 mg/kg, ww), while Cd and Pb were lowest. The overall order was Fe > Zn > Cu > Mn > Ni > Pb > Cr > Cd in muscle and Fe > Zn > Cu > Mn > Ni > Cd > Cr > Pb in gut. Riverine hilsa accumulated elevated Fe, Mn, Cr, and Zn, whereas marine hilsa had higher Cu and Pb. Ni exceeded permissible food limits in estuarine and nearshore marine waters. Pearson correlation and PCA indicated positive associations between FeZn and CuCd, with distinct tissue and moderate habitat clustering. THQ values <1 across sites indicated negligible health risks. Cancer risks exceeded thresholds for Ni but remained negligible for other metals. UNMIX receptor modeling identified three sources: a dominant anthropogenic source (Cd, Zn, Cu, Fe), a mixed lithogenic-anthropogenic source (Mn, Ni), and a Pb-associated source, consistent with PCA and MPI patterns. Results suggested that the migratory behavior of T. ilisha may facilitate the transport of metals across ecological boundaries, linking inland pollution with offshore areas of the Bay of Bengal.