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Sperm whales (Physeter macrocephalus) are being watched and in some cases, studied in whale watching communities such as Ogasawara (Bonin Islands), Nachi-Katsuura, Muroto, Futo, and Choshi, along Northwest Pacific coast of Japan (Hoyt 2005, Ishihara and Suda 2006).

For years, sperm whales are also known to occur, caught by coastal whaling in the past, and more recently being watched in northern part of Nemuro Strait (which is a part of the World Nature Heritage site), eastern Hokkaido. However, their ecology has been poorly known in this water.
In 2006, we begun to accumulate photographs of natural markings of sperm whales for photographic identification (Photo-ID) in this area. This can be carry on long-term and with collaboration with both researchers and public volunteers through the opportunities such as local whale watching trips. We followed Ishihara and Suda (2006) to organize 2006-2010 ID images.

In Nemuro Strait, Dr.Masao AMANO (Nagasaki University) and his students and colleagues begun ecological studies of sperm whales in Nemuro Strait in 2007, such as analisys of diving behavior with data-logger, acoustic analyses, as well as at sea and land-based observation of the whales. Our Photo-ID has been undertaken as a part of those scientific studies to know about social structure and population size of sperm whales in Nemuro Strait.

Our preliminary results regarding sperm whale sightings and ID were summarized in table 1below. Table 2 shows history of occurrence of all identified-animals, 2006-2010.
We provided the ID catalogue of tail fluke shoots and in some cases, dorsal fin images as well, for all of our identified-animals in Table 3.
Total 114 individuals were identified through 2006-2010 seasons. The most approximate body size of the sperm whales in Nemuro Strait are more than 12 meters long, and we seldom recognized "calluses" on their dorsal fin, which usually be found on those of mature females (Mori et al., 2009), we suppose that we are watching both young and mature males. And here is probably one of the feeding canyon for male sperm whales, like as those recognized in such as Norway, Canada and New Zealand (Ciano & Huele, 2001).
To share our ID catalogue with other colleagues around the world, we hope this helps to know more about the move of individuals and population structure of sperm whales.

Table 1

	2006	2007	2008	2009	2010
1. Months animals occurred	Aug-Oct	Jun-Oct	Jun-Oct	May-Nov	May-Oct
2. Total sighting days	38	45	60	65	83
3. Total number sighted	420	561	492	761	768
4. Averaged number of animals per a day (3/2)	11.1	12.5	8.2	11.7	9.3
5. Total individuals identified in each season *See table 2 as well	28	41	32	43	40
6. Individuals newly identified in each season (out from 5) *See table 2 as well	28	28	18	26	14
7. Number of re-sightings from the previous season *See table 2 as well	-	13	14	17	26
8. Re-sighting ratio of identified animals in each season (7/5)	-	31.7%	43.8%	39.5%	65%

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Ciano, J.N. & Huele, R. 2001. Photo-Identification of Sperm Whales at Bleik Canyon, Norway. Marine Mammal Science, 17(1):175-180.
Hoyt, E.. 2005. Watching Whales and Dolphins in Japan, Hong Kong, Taiwan and Korea. WDCS and IFAW,
Kochi, Japan. 44pp.
Mori, Kyoichi, Yoshioka, Motoi and Amano, Masao.2009. Physeter macrocephalus Linnaeus, 1758. The Wild Mammals of Japan. Ohdachi et al (Ed.) pp.336-337. Shoukadoh Book Sellers, Kyoto, Japan.
石原茉里・須田泰臣, 2006. 小笠原諸島周辺海域におけるマッコウクジラの個体識別.　卒業論文, 帝京科学大学．21pp. (in Japanese)

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