Monitoring and conservation of Japanese Murrelets and related seabirds in Japan

Abstract

Of the 24 species in the Auk (or Alcidae) family of seabirds living in the northern hemisphere, 22 reside within the North Pacific Ocean. These “penguins of the north” use their small wings to “fly” underwater, some to more than 200 meters, where they catch and eat a variety of small fish and invertebrates. In terms of sheer numbers (>65 million) and food consumption, the Auks dominate seabird communities on our continental shelves and they serve as indicators of the health of our ocean. If Auk populations are not all thriving, then we should be concerned about the status of the oceans, plankton and fish that normally sustain them. A few Auk “tribes” genera) are abundant and widespread (such as Uria murres and Aethia auklets), and some are rare and isolated such as Synthliboramphus murrelets, including the Japanese “Crested” Murrelet). Only 8 species of Auk breed in Japan, including species that have either widespread or isolated populations in the North Pacific. During the past century, most of these Auks have declined dramatically in Japan from many causes, including the introduction of predatory rats and cats to breeding islands, bycatch in fishing nets, alteration of food supplies by fishing and climate change, oil spills, and destruction of seabird nesting habitats. Widespread species such as the Common Murre and Tufted Puffin were once common in Japan but now breed in low numbers at only a few locations. Probably common in the past, small numbers of the widespread Ancient Murrelet were recently re-discovered breeding at Teuri Island, which is also home to the world’s largest colony of Rhinoceros Auklet, another widespread species. Though common throughout the North Pacific, Pigeon Guillemots, breed only in the southern Kuril Islands. Their population status is unknown, but they were never considered common in Japan. In contrast, Spectacled Guillemots are an example of an uncommon and isolated population of Auk. They nest along coasts of the Sea of Okhotsk and Sea of Japan, and populations have declined in recent decades. The Long-billed Murrelet has a similar distribution to Spectacled Guillemot, and once bred in Hokkaido, but populations appear to have been extirpated. The Japanese Murrelet has a very small world population, and breeds at only a few locations in southern Japan and the Republic of Korea. The international community of research and conservation biologists is greatly concerned about the ability of this species—probably the rarest of all Auks in the world— to maintain its population size. Owing to its small size and high metabolic demand, this species is especially vulnerable to any stress that increases its food requirements such as changing fish stocks, disturbance on feeding or wintering grounds, or changing ocean climate. Immediate management actions are needed to preserve Japanese Murrelets and other Auks in Japan, by such means as eradicating rats and cats on breeding islands, altering fishing gear to minimize bycatch, and reducing human disturbance to nesting habitats. More research and monitoring of Auk populations in Japan is needed to track population trends, and further identify factors responsible for declines. Interaction between governments and biologists at regional and international levels will be mutually beneficial as we all strive to conserve precious resources and biodiversity in the northwest Pacific, and particularly the Japanese islands.