The common thresher shark, a pelagic and globally distributed species, has been relatively understudied in both the Pacific and Atlantic Ocean systems.  Limited historical data suggests that thresher shark populations in the western North Atlantic Ocean may undergo long periods of abundance and decline.  Of the pelagic sharks in the Atlantic – common threshers have recently been classified as a species at high risk.   We are exploring key biomarkers and related parameters to determine baseline individual and population-level health of this important predator.