The literature reports of Mesoplodon carlhubbsi strandings are confusing, owing to the erroneous identification of Mesoplodon species. Mesoplodon carlhubbsi is distinct from M. stejnegeri and closely related to M. bowdoini. Adult M. carlhubbsi are recognized by white (males) or light-colored (females) beaks. We report 31 strandings of this species from both the east and west coasts of the North Pacific. Scarring is very marked in older males and probably results from intraspecific aggression. Calving season is in the summer. Length at birth is about 250 cm. Both females and males reach 488-532 cm at physical maturity. Food items are fish and squid. Distribution extends from the confluence of the Kuroshio and Oyashio currents in the west to the mixed region of the California current in the east
