First report of a Risso’s dolphin (Grampus griseus) stranded in Jeju Island, Republic of Korea: findings from necropsy, histopathology and microbiome analysis

A female Risso's dolphin (Grampus griseus) carcass was found stranded in fresh condition at Jeju Island of the Republic of Korea on February 18, 2018. Body surface lacerations, gross pathology and histology of the lung indicated the cause of death as drowning by fishing gear entanglement. The dolphin was a five-year-old mature female having ovaries with follicles and a corpus albican. This is the lowest recorded age thus far of a Risso's dolphin with active ovaries. The stomach was filled with Japanese flying squid and based on their distribution, it is believed that the dolphin was foraging in the South Sea, which had not been known as their habitat before. Intestinal microbiome analysis revealed that the bacterial community predominantly comprised phylum Proteobacteria (92.8 per cent). To our knowledge, this is the first microbiome analysis and the first official necropsy report of stranding in Jeju Island of the Risso's dolphin.