We are pleased to announce our new publication: Danil, K, N. Beaulieu-McCoy, S. Dennison, D. Rotstein, T. Rowles, S. Wilkin. 2021. Uncommon Stranding Event of Bottlenose Dolphins (*Tursiops truncatus*) in San Diego, California (October 2015). NOAA Tech. Memo. NMFS-SWFSC-641, 26 p. https://swfsc-publications.fisheries.noaa.gov/publications/TM/SWFSC/NOAA-TM-... Executive Summary Two freshly dead, adult coastal common bottlenose dolphins (Tursiops truncatus), stranded one mile apart from each other on Silver Strand State Beach in Coronado, San Diego County, California on October 21, 2015. On this same day, the U.S. Department of the Navy began a major training exercise (MTE). Ten days later, an additional adult T. truncatus stranded dead in advanced decomposition along the same beach. The spatial and temporal similarities of the strandings represented an unusual occurrence for the region. Post-mortem examinations revealed that all three dolphins were in robust body condition, had no external signs of fishery interaction, and presented with subcutaneous hemorrhage in the head region concentrated along the lower jaws, with subcutaneous emphysema associated with areas of cervical blubber hemorrhage. Hemoabdomen, gas bubbles within the mesenteric and cerebral vasculature, and evidence of recent feeding were observed in both dolphins that were examined in greatest detail. Additionally, cerebral hemorrhage and hemopericardium was observed in one specimen and scant lipids in the lungs of another. The combined findings indicate that the dolphins were exposed to acute, severe trauma, likely anthropogenic in nature. Based on previous case studies, an underwater detonation, peracute underwater entrapment (PUE) (e.g. net entanglement) or mid-frequency active (MFA) sonar are the most plausible explanations for the observed trauma. However, no underwater detonations were reported as part of the MTE. Three coastal fisheries that target squid, bait, and lobster operate in October that could potentially entrap a coastal T. truncatus. However, no squid fishery vessels were operating off San Diego during this time, no bait fishing activity the day preceding the strandings occurred, and lobster pots are unlikely to entrap 3 dolphins at one time. An illegal U.S. fishery or nearshore Mexican fishery could be an alternate source of PUE. MFA sonar was in use on October 19 and 20, with the closest Navy ship within 6 NM of the stranding location. Although MFA sonar seems the most likely source of the observed trauma, PUE from an unidentified fishery or unknown source remain a possibility. -- Kerri Danil (she/her/hers) Research Biologist, Southwest Fisheries Science Center NOAA Fisheries | U.S. Department of Commerce Cell: (858) 366-2667 Stranding hotline: (858) 546-7162 https://www.fisheries.noaa.gov/west-coast/science-data/cetacean-health-life-... https://swfsc-publications.fisheries.noaa.gov/publications/?search=danil