To evaluate the capacity of the European conger (Conger conger) as a reliable bioindicator to investigate marine contaminant sources and pathways, the muscles of 24 individuals caught in a semi-enclosed industrialized bay (Gulf of Fos, France) were analyzed for numerous organic compounds, metal elements, and stable isotopes. The contaminant levels were elevated to moderate, which relates to the great anthropic pressure from the surrounding industries and maritime traffic. Stable isotope analyses finely discriminated between three geographical areas and between two age groups. Mercury (Hg) and arsenic (As) concentrations (nd-1.35 mg.kg −1 and 5.94-60.1 mg.kg −1 wet weight (ww), respectively), as well as chlorination by-products, were elevated in particular areas, identifying specific industrial sources. Levels of Σ 42 PCB (7.15-28.67 µg.kg −1 ww), Σ 16 PAH (3.64-9.48 µg.kg −1 ww) and Σ 10 pesticides (1.91-18.42 µg.kg −1 ww) in fish muscles, as expected, did not differ among sites.