Origin of the mass mortality of the flathead grey mullet (Mugil cephalus) in the Tanshui River, northern Taiwan, as indicated by otolith elemental signatures

► A massive kill of mullet (estimated at 50 tons) occurred on August 10, 2006 in the Tanshui River in northern Taiwan. ► To investigation the origin of the mullet, concentrations of trace elements in otoliths were measured to indicate life history of the mullet. ► Half of the fish lost were estuarine residents and the remainders were from marine and freshwater habitats. ► The number of mullet inhabiting in estuary appears contradictory to the conventional view of mullet habitat use in the Tanshui River.