Gaskin et al.: Phocoena phocoena in the coastal waters of northern Japan 



451 



Nemuro, and northwestern Honshu are possibly in the 

 low hundreds 8 . Tobayama et al. (1991) noted that about 

 1,700 large trap nets and about 10 times that number 

 of smaller-scale nets are in operation at some time of 

 year in Japan. About 4,800 nets operate in Hokkaido 

 waters; 2,500 on the Pacific coast of northern and west- 

 ern Honshu and perhaps about 1,500 on the northern 

 half of the Sea of Japan coast of Honshu. All these 

 regions are coincident with the distribution of the har- 

 bor porpoise in Japanese waters. Tobayama et al. con- 

 cluded that where minke whale entrapments were con- 

 cerned, the catches were largely unrecorded through 

 the coastal fisheries statistics. Presumably this is also 

 true of harbor porpoise entrapments. Given that we 

 noted deaths of P. phocoena in gill nets not recorded in 

 the annual statistics, there is significant under-report- 

 ing of incidental kills by gill netting too. We lacked the 

 resources to conduct a survey to determine how large 

 the incidental catch of harbor porpoises by fixed gear 

 in Japanese waters might be. 



The status of the harbor porpoise in Japanese wa- 

 ters is basically unknown. Anecdotal accounts from 

 fishermen in the Usujiri region indicate that it is not 

 particularly abundant in comparison to other dolphins 

 (species not specified) and seasonal in occurrence 

 (spring and fall). It is present in waters off Otaru in 

 all but the months of July-September (Hiroshi Nitto, 

 personal communication). A detailed assessment of its 

 status in the western North Pacific is required. The 

 species now appears to be threatened in some eastern 

 and western North Atlantic waters (Gaskin, 1992). The 

 limitations imposed by the fixed litter size of one, the 

 relatively late age at first maturity and an annual 

 reproductive cycle all point to little reproductive flex- 

 ibility with which to respond to significant additional 

 mortality from hunting or incidental capture (Woodley 

 and Read, 1991; Gaskin, 1992). 



Acknowledgments 



The authors thank the following for their cooperation 

 during the collection and study of specimens for this 

 study: Nobuyuki Miyazaki of the National Museum of 

 Science, Tokyo; Seiji Ohsumi (retired) and Toshio 

 Kasuya of the Far Seas Fisheries Research Labora- 

 tory, Shimizu; Hideo Omura, former Director of the 

 Whales Research Institute, Tokyo; Hiroshi Nitto of the 

 Otaru Aquarium; Yasunori Sakurai and Takahiro Koga 

 of the Asamushi Aquarium, Aomori; Masaaki Mori, Act- 

 ing Director of the Sunshine City Aquarium, Tokyo, 



'A. Kawamura, Faculty of Bioresources, Mie University, Tsu 514, 

 Japan, unpubl. data. 



"Hiroshi Nitto, pers. commun. 



and Kiyoji Miyagaki, President of Sunshine Kogyo Cor- 

 poration, Tokyo; Junroku Ogasawara and Syuichi 

 Nishiuchi of the Hokkaido Fisheries Experimental Sta- 

 tion, Wakkanai; Kiyoshi Nomura and all the fishermen 

 of the Nomura Fishing Company in Usujiri, Hokkaido; 

 and the University of Hokkaido Faculty of Fisheries at 

 Hakodate which provided laboratory and field facili- 

 ties and subsidized accommodation. Special thanks are 

 extended to our good friend Yoetsu Arashida, Manager 

 of the University of Hokkaido Marine Biology Station 

 at Usujiri who looked after our field accommodation 

 and gave many personal kindnesses during our two 

 lengthy stays. Funding for this work was provided by 

 two travel fellowships (1985 and 1986), under the Bi- 

 lateral Agreement between the Natural Sciences and 

 Engineering Research Council of Canada and the 

 Japan Society for the Promotion of Science (special 

 thanks to Hiroshi Kida and A. Kugler), and with the 

 further support of NSERC Operating Grant A5683. 



Literature Cited 



Amano, M., and N. Miyazaki. 



1992. Geographic variation in skulls of the harbor por- 

 poise, Phocoena phocoena. Mammalia 56: 133-144. 

 Amu iid in, M., and B. Amundin. 



1974. On the behavior and study of the harbour por- 

 poise, Phocoena phocoena, in the wild. In G. Pilleri 

 (editor), Investigations on Cetacea, Vol. V, p. 317- 

 328. Berne, Switzerland. 

 Andersen, L. W. 



1990. The population structure of Phocoena phocoena 

 in Danish waters. Annual meeting of the Scientific 

 Committee of the International Whaling Commission, 

 Noordwijkerhout, The Netherlands, 10-23 June 1990, 

 document SC/42/SM50. 

 Barlow, J. 



1988. Harbor porpoise, Phocoena phocoena, abundance 

 estimation for California, Oregon and Washington: 



I. Ship Surveys. Fish. Bull. 86: 417-432. 

 Barlow, J., and D. A. Hanan. 



1990. An assessment of the status of harbor porpoise 

 populations in California. Annual Meeting of the Sci- 

 entific Committee of the International Whaling Com- 

 mission, Noordwijkerhout, The Netherlands, 10-23 

 June 1990, document SC/42/SM6. 

 Barlow, J., C. W. Oliver, T. D. Jackson and B. L. Taylor. 



1988. Harbor porpoise, Phocoena phocoena, abundance 

 estimation for California, Oregon, and Washington: 



II. Aerial Surveys. Fish. Bull. 86: 433-444. 

 Bjorge, A., and S. Kaarstad. 



1990. Preliminary analysis of growth and reproduc- 

 tion of harbour porpoises Phocoena phocoena in Nor- 

 wegian waters. Annual Meeting of the Scientific 

 Committee of the International Whaling Commission, 

 Noordwijkerhout, The Netherlands, 10-23 June, docu- 

 ment SC/42/SM2. 



