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Assessing mortality of long-lived organisms is fundamental for understanding population trends and for implementing conservation strategies, but doing so for marine megafauna is challenging. Here we assessed anthropogenic mortality of endangered North Pacific loggerhead turtles in the coastal waters of Baja California Sur, Mexico (BCS), through the synthesis of 3 sources:(1) intensive surveys of an index shoreline from 2003 to 2007;(2) bimonthly surveys of additional shorelines and towns for stranded and consumed carcasses from 2006 to 2007; and (3) observations of bycatch by 2 small-scale fishing fleets. Using Monte Carlo simulations we estimate that 1500 to 2950 loggerhead turtles died per year at BCS from 2005 to 2006 due to bycatch in the 2 observed fleets. Actual mortality may be considerably higher due to bycatch in other fisheries, directed hunting for black market trade, and natural factors …