Matching of the Gray Whales of off Sakhalin and the Pacific Coast of Japan, with a Note on the Stranding at Wadaura, Japan in March, 2016

Thecoast of Japan is a migratory corridor for the western stock of the gray whales(Eschrichtius robustus), which was once considered as extinct and remains endangered. Accordingto the historical records, from 1955 to 2014, only 21 gray whales occurrencehas been recorded in 59 years. However, from 2015 to 2016, intensive occurrenceincluding the seven sightings and the two strandings were noted. In this paper,we found that those sightings were re-sightings of the same individual, whichwas initially sighted off Sakhalin during August, 2014. On 4 March, 2016, ayoung female gray whale (8.9 m in body length) was stranded at Wadaura beach, Chiba prefecture. We also conducted research on this animalincluding taking pictures and external measurements. In addition, we flensed thisanimal to observe the internal organs and collect a skeletal specimen. Thereason for the death of this animal remains unclear; however, from its externalcharacteristics, we identified that this animal was not an identical one,sighted off Sakhalin and the coast of Japan from 2014 to 2016. On 5 April,2016, another young female gray whale (7 m in body length) was stranded at Araibeach, Shizuoka prefecture. We concluded that from 2015 to 2016, at least threedistinct gray whales have migrated along the coast of Japan.