Mortality Event

A mortality event is a sudden die-off of marine animals beyond normal background rates, caused by harmful algal-bloom biotoxins, disease, hypoxia, cold or heat stress, or starvation. In the US, the Marine Mammal Protection Act defines an Unusual Mortality Event (UME) as a stranding that is unexpected, involves a significant die-off, and demands immediate response. The national Working Group on Marine Mammal UMEs assesses events against seven criteria covering marked changes in magnitude, timing, location, and species, age, or sex composition, then recommends a UME declaration to NOAA’s Assistant Administrator for Fisheries, which triggers investigation and response funding.