Seabird and Dolphin Mortality Associated with Underwater Detonation Exercises

Abstract

We report the details of two wildlife mortality events that were associated with underwater detonations. The detonations occurred as part of military training activities at Silver Strand Training Complex in San Diego, California. In March 2006, an underwater detonation resulted in 70 western grebes (Aechmophorus occidentalis) being killed by subsequent sequential detonations in the same training exercise. Ten of the 70 western grebes impacted were necropsied, verifying cause of death as primary blast injury. In March 2011, a time-delayed underwater detonation resulted in the death of three or possibly four long-beaked common dolphins (Delphinus capensis). While these blast events were unlikely to impact these species on a population level, underwater detonations do have the potential for population-level impacts on wildlife. Both events were accidental mortalities and the first ever documented from Navy underwater detonation training in Hawaii, Southern California, and along the U.S. East Coast. The Navy updated its underwater explosive mitigation measures after each of these mortality events to limit the potential of future mortalities by requiring sequential detonations to occur either less than 5 s or more than 30 min apart and by suspending time-delayed detonation training exercises until more robust precautionary measures can be developed.