An estimated 20 percent of Atlantic bluefin tuna, spawned this year in the Gulf of Mexico, died because of BP’s oil spill according to an assessment based on satellite images.

The European Space Agency, in league with the Ocean Foundation, reached that conclusion after collecting satellite images and other data from the start of the spill on Apr. 20 until Aug. 29. The nearly-200 million gallon spill occurred at the height of the spawn and affected one of two areas in which the tuna spawn.

Already under great stress because of overfishing and the impacts of longline fishing, the oil spill has put the tuna in such peril that the National Marine Fisheries Service is conducting its own year-long study into whether it should be protected under the Endangered Species Act.