Field-based assessment of heavy metal accumulation and tissue-specific distribution in the demersal freshwater fish Hypostomus sp.

This study investigated the tissue-specific distribution and bioaccumulation of seven heavy metals (Pb, Cd, Hg, As, Cr, Cu, and Zn) in the demersal freshwater fish Hypostomus sp. collected from the Surabaya River, Indonesia. As a benthic species with continuous sediment contact, Hypostomus sp. provides an effective model for assessing metal exposure in polluted tropical rivers. Metal concentrations were quantified in muscle, gills, liver, bone, and eggs using ICP–MS, alongside parallel measurements in water and sediment. Sediment contained the highest metal loads, confirming its role as the dominant contamination reservoir. Among fish tissues, the liver accumulated the greatest concentrations of most metals, followed by the gills, reflecting their respective functions in detoxification and respiration. Bone showed the highest Pb deposition, consistent with its osteophilic affinity, while muscle exhibited the lowest accumulation across metals. Notably, maternal transfer was evident for Cu, Zn, Hg, As, and Pb, with measurable concentrations detected in eggs. The overall accumulation profile (liver > gills > bone > muscle) highlights metal-specific affinities and physiological regulation in demersal fish exposed to sediment-bound contaminants. These findings highlight clear metal-specific accumulation patterns in this demersal fish, demonstrating how exposure to sediment-bound contaminants shapes the distribution of heavy metals across different tissues.