No coastal or other wintering ground has been found for North Pacific right whales. Which factors cause right whales not to favor inshore waters is unknown. Off the west coast of the United States, Point Conception is a turning location in terms of sighting records in the 19th and 20th centuries, and this may contribute to support the once-abandoned idea; existence of historical breeding grounds in coastal waters including along North American continent. Ryukyu Islands had been suggested as a wintering ground for the western population, but little evidence supports this. According to Maury's chart, in winter, some concentrations could be seen at several areas such as the southern Sea of Japan, around southern coasts of Korean Peninsula (such as around today's Dadohaehaesang National Park on southwestern Korean Peninsula) and Jeju Island, areas off Shanghai and the Zhoushan archipelago, Taiwan Strait (e.g. Fujian coasts like Pingtan Island, Penghu Islands, west coast of Taiwan), the northwestern Hawaiian Islands. (with smaller areas scattered among southern Korean and Japanese waters). In Asia, southernmost of areas with higher catch densities were the pelagic waters between continental China (latitudes equal to Shanghai and Zhoushan Islands) and west of Kyushu in south to southern coasts of Korean Peninsula during the summer. Some whales were caught off Hainan Island and this area is possibly the southernmost location of known range for the western population. The whales are also known to occur around the northern Mariana Islands. A map had been academically created which forecasts potential wintering habitats for right whales in north Pacific according to environmental factors corresponding to that of north Atlantic species, including further south to Hainan, Leizhou Peninsula, and northern Gulf of Tonkin. Historical occurrences of vagrancy around Borneo have been considered as well, while possibilities of migrations to or through Philippines are unclear.