Species-wise Mercury Accumulation in Fish from Ulhas River Estuary and Thane Creek in the vicinity of Mumbai, India and its Relation to the Feeding Habits of Fish

Thane Creek (73°14’ E, 19°14’N to 72°54’ E, 19°17’ N) and Ulhas River estuary (72°55’E, 19° N to 73°E, 19°15’N), in the vicinity of Mumbai, India receive industrial effluents and sewage from industries and residential complexes respectively, located along their banks. Survey of the fishing villages along these water bodies revealed estuarine/creek fish as the dietary mainstay of the inhabitants here and species of fish consumed depends upon their availability in that particular site. Species-specific study of mercury levels in fish from three different sites on Ulhas River estuary and Thane Creek revealed that herbivorous species like juvenile prawns, Tilapia mossambica and Mugil cephalus accumulated lesser mercury (non-detectable to 0.357 μg.g^-1) in comparison to the permissible limit of 0.5 μg.g^-1recommended by World Health Organisation (WHO) while those of higher trophic levels like Mystus gulio, Arius maculatus and Scylla serrata had elevated levels of mercury (0.428 to 2.48 μg.g^-1). The results also revealed that mercury in fish proportionally increased with the percentage of animal matter in the stomach. This study therefore recommends the fish-eating populations along Thane Creek and Ulhas River estuary to consume preferably the herbivorous fish; omnivorous fish should be consumed in moderation and avoid the consumption of carnivorous fish.