ABSTRACT

INTRODUCTION
After the two-year feasibility study in 2000-2001, the full-scale survey of the Second Phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) was started in 2002. The objectives of the program are 1) Feeding ecology and ecosystem studies, involving prey consumption by cetaceans, prey preferences of cetaceans and ecosystem modeling; 2) Monitoring environmental pollutants in cetaceans and the marine ecosystem; and 3) Stock structure of whales (Government of Japan, 2002). The JARPN II coastal component using small-type whaling catcher boats started in 2002 to complement the temporal and spatial gap of the offshore components using the Nisshin Maru research vessel. In the original JARPN II plan, the coastal component was presented as a two-year feasibility study to examine the logistic aspects of the methodology (Government of Japan, 2002). The first feasibility survey was carried out in the coastal waters off Kushiro in autumn 2002 (Kishiro et al ., 2003) and the second feasibility survey was conducted in the coastal waters off Sanriku district in spring 2003 (Yoshida et al ., 2004). In each of the surveys, 50 common minke whales were caught. From detailed examination of the logistic aspects of the surveys, it was concluded that no substantial problem occurred and that the coastal survey could be continued as a component of the JARPN II using same kind of vessels (small-type whaling catcher boats) and methodology (Government of Japan, 2004a, Kato et al ., 2004). However, re- calculation of required sample size from the survey data suggested that the size should be modified to 60 individuals in each area/season (Tamura et al ., 2004), and from the possible geographical and/or temporal variations of prey consumption of the whales, the coastal surveys thought to be needed on a yearly basis in each local area (Govemment of Japan, 2004b). The revised survey off Sanriku was carried out in spring during 2005 and 2010 year (Yoshida et al., 2006; Goto et al. , 2007; Bando et al. , 2008, 2011; Yasunaga et al. , 2009, 2010). On March 11 2011 the Ayukawa town, including all research facilities of JARPN II, was destroyed by a large earthquake and tsunami. In this year the spring coastal survey could not be conducted in Ayukawa. Instead the spring survey in 2011 was conducted in Kushiro. Fortunately the Ayukawa research station was reconstructed and the 2012 survey of the JARPN II coastal component in spring could be conducted in this locality again. Here we report the survey carried out in coastal waters off Sanriku from 12 April to 26 May in 2012. This survey was authorized by the Government of Japan in compliance with Article VIII of the International Convention for the Regulation of Whaling. The Institute of Cetacean Research (ICR) planned and conducted the survey in cooperation with the National Research Institute of Far Seas Fisheries and Tokyo University of Marine Science and Technology, and the Association for Community-Based Whaling.
MATERIALS AND METHODS
Research area
The research area was set in the same way as in previous surveys off Sanriku (Bando et. al , 2011). The research area comprised coastal water within 50 n. miles from northeastern part of the Japanese main island, Honshu, (Figure 1). The area was divided into Areas 1, 2 and 3 centering on the Ayukawa port (Figure 1). The research area corresponds to the northern part of sub-area 7, established by IWC (1994).
Whale sampling
Four small-type whaling catcher boats were used as sampling vessels: Taisho Maru No. 28 (hereinafter referred as 28T; 47.3GT), Koei Maru No. 8 (8K; 32.0GT), Katsu Maru No.7 (7K; 32.0GT), and Sumitomo Maru No.51 (51S; 30.0GT). All the animals sampled were landed on the JARPN II research station established at the Ayukawa port for biological examination. All common minke whales collected were examined biologically by researchers at the research station. A list of biological items to be collected is shown in Table 1.
Prey species of common minke whale
Following the same methods used in the JARPN II feasibility survey conducted in 2001 (Fujise, et al. , 2002), stornach contents were weighted to the nearest 0.1 kg, in each of the four chambers, for both cases including and excluding liquid contents. In addition a small sample of forestomach contents was collected and frozen for laboratory analysis.
RESULTS
Searching effort
The whale sampling survey was conducted from 12 April to 26 May, 2012. Cruise tracks by the sampling vessels 28T, 8K, 7K and 51S are shown in Figure 2. The tracks covered widely the coastal waters off Sanriku. Searching distance and time are listed in Table 2, by sampling vessel. Searching distance and time are defined as distance and time recorded under searching activity conducted from the top barrel of the vessels. Total searching distance and time made by the three vessels were 6,488.1 n. miles and 620.1 hours, respectively (Table 2).
Sightings
A total of 95 schools (97 individuals) of common minke whales was sighted during the searching (Table 3, Figure 3). One cow-calf pair was observed. Density index (DI, the number of primary sightings of schools per 100 n.miles searching) of common minke whales in Areas 1, 2 and 3 were calculated as 2.43, 0.43 and 0.49, respectively (Table 4). Two schools (two individuals) of fin whales, 43 schools (58 individuals) of humpback whales and 4 schools (11 individuals) of killer whales were sighted during the searching (Table 3, Figure 4).
Sampling of common minke whales
A total of 60 common minke whales was sampled. Two situations of struck and lost occurred. The sighting positions of sampled animals are shown in Figure 3.
Biological examination
Sex ratio, body length and weight Research items for the biological examination are summarized in Table 1. The sampled animals consisted of 29 males and 31 females. Sex ratio of males was 0.48. Average body length was 5.10 m (max=7.57, min=3.92) for males and 5.34 m (max=8.07, min=4.06) for females (Table 5). The sexual maturity of animals collected is shown in Table 6. For males and females 6.9% and 9.7% of the animals sampled in all areas, were sexually mature, respectively. Among the mature females, one resting, one pregnant and one pregnant & lactating cases were observed.
Prey species of common minke whale
Forestomach contents are listed in Table 7. Adult Japanese sand lance ( Ammodytes personatus ) (46.3%, 19 from 41 animals) and juvenile sand lance (41.5%, 17 from 41 animals) were observed in Area 1, and Japanese anchovy ( Engraulis japonicus ) and krill ( Euphausia pacifica) were observed in two and five animals in Areas 2 and 3, respectively (Table 8, Figure 5). The maximum net weight of forestomach contents was 27.6 kg, consisting of
Observation of marine debris
Observation of marine debris was made in the stomachs of the 60 common minke whales sampled. One plastic piece was found in the stomach of an individual, one fishhook in the stomach of a different individual and three sheets of resins in the stomachs of  three different individuals.
DISCUSSION
The spring survey of the coastal component of JARPN II was re-started in Ayukawa in 2012 after one year of no research activities in that locality as effect of the 2011 earthquake and tsunami. There were no practical problems in conducting the survey in Ayukawa in 2012. In general the weather conditions were good and better that those in previous surveys in Sanriku. This allowed that the research area was searched widely and that the sample size of 60 animals could be attained. The sighting positions of common minke whales in the present survey were concentrated mainly within the Sendai Bay (Figure 3). Whales outside the Sendai Bay were distributed on the shelf region and along the 100-200m isobaths on the slop. The density index (DI) of common minke whales in Area 1 (DI=2.43) was higher than those in Areas 2 (DI=0.43) and 3 (DI=0.49), suggesting that common minke whales were concentrated in the Sendai Bay. The DI in Area 1 in the present survey was slightly higher than those in 2006 (DI=1.83, Goto et al., 2007), 2007 (DI=1.91, Bando et al. , 2008), 2008 (DI=1.57, Yasunaga et al. , 2009) and 2009 (DI=2.08, Yasunaga et al. , 2010). On the other hand the DI of Areas 2 and 3 in 2012 were similar to DI in 2010 (DI=0.66, Yasunaga et al. , 2011). The surveys from 2006 to 2010 were conducted mainly in Area 1. The sex ratio of males of minke whales collected in the present survey (0.48) was similar to those in 2006 (0.43, Goto et al., 2007), 2007 (0.37, Bando et al. , 2008), 2008 (0.38, Yasunaga et al. , 2009), 2009 (0.45, Yasunaga et al. , 2010) and 2010 (0.48, Yasunaga et al. , 2011). Frequency distribution of body length of common minke whales collected in the present survey was similar to those in 2009 and 2010 surveys, and their peaks in 2009, 2010 and 2012 surveys were shorter than those in 2006, 2007 and 2008 surveys (Figure 6). These results suggest that the pattern of migration of common minke whales into the Sendai Bay in spring 2012 was similar to that before the earthquake and tsunami, although more whales were observed in 2012. Adult Japanese sand lances were mainly observed in the forestomachs of whales collected from Area 1 while that Japanese anchovy and krill were observed in forestomachs in whales in Areas 2 and 3 (Table 8). This suggests that common minke whales in the Sendai Bay and in the outside slope feed on different preys (Figure 5). The first dominant prey items of the whales collected from Area 1 in the present research (adult sand lance) are in agreement with those during 2006 and 2010 (Goto et al. , 2007; Bando et al. , 2008; Yasunaga et al. , 2009; Yasunaga et al. , 2010; Band et al. , 2011) (Figure 7). The second dominant prey items of whales collected from Area 1 were juvenile Japanese sand lance. This is the same as those in 2008 (Yasunaga et al ., 2009), while those in 2009 (Yasunaga et al ., 2010) and 2010 (Bando et al. , 2011) were krill and those in 2006 (Goto et al. , 2007) and 2007 (Bando et al. , 2008) were Japanese anchovy (Figure 7). The second dominant prey item for common minke whales in Sendai Bay shows some yearly change.
ACKNOWLEDGMENTS
We acknowledge Luis Pastene (ICR), Tomio Miyashita (NRIFSF) and Tatsushi Matsuo (Fisheries Agency of Japan), for their guidance in the survey design and support. Crewmen, staff of the research station in Ayukawa and the Association for Community-Based Whaling assisted greatly during the survey. We also thank the members of the municipal office of Ishinomaki and Miyagi prefectural office, for their kind assistance. Bando, T., Kato, H., Kishiro, T., Goto, M., Saito, T., Tabata, S., Morita, Y., Okamoto, R., Maeda, H., Inagaki, M., Nagatsuka, S., Ebisui, T., Nakai, K., Matsumoto, A., Gokita, A. and Kawahara, S. 2008. Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2007- Coastal component off Sanriku. Paper SC/60/O6 submitted to the 60 k IWC scientific Committee, 27pp. Bando, T., Yasunaga, G., Kato, H., Ito, N., Tabata, S., Oikawa, H., Nakamura, G., Maeda, H., Miyakawa, N., Zenitani, R., Zennyoji, Y., Yonehara, Y., Ishikawa, Y., Fukutome, K., Tsunekawa, M., Aki, M., Yamasaki, K., Tsutsumi, T., Kitayama, K. and Onodera, K. 2011. Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2010 (Part II) - Coastal component off Sanriku. Paper SC/63/O3 submitted to the 63 th IWC scientific Committee, 14pp. Fujise, Y., Tamura, T., Bando, T., Watanabe, H., Kiwada, H., Otani, S., Kanda, N., Yasunaga, G., Mogoe, T., Konishi, K., Inamori, M., Shigemune, H. and Tohyama, D. 2002. Cruise report of the feasibility study of the Japanese Whale Research Program under Special Permit in the western North Pacific-Phase II (JARPN II) in 2001. Paper SC/54/O16 submitted to the 54th IWC Scientific Committee, 51pp. Goto, M., Kato, H., Zenitani, R., Yoshida, H., Saito, T., Tabata, S., Morita, Y., Sato, H., Okamoto, R., Maeda, H., Odagawa, A., Ebisui, T., Nakai, K., Matsumoto, A., Fujimori, S., Nishiwaki, S. and Kawahara, S. 2007. Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2006- Coastal component off Sanriku. Paper SC/59/O6 submitted to the 59 th IWC scientific Committee, 34pp. Government of Japan, 2002. Research plan for cetacean studies in the western North Pacific under special permit (JARPN II). Paper SC/54/O2 submitted to the 54th IWC Scientific Committee. Government of Japan (Fujise, Y., Tamura, T., Kato, H. and Kawahara, S. eds.), 2004a. Some considerations of the feasibility components of the JARPN II research plan. Paper SC/56/O2 submitted to the 56th IWC Scientific Committee, 36pp. Government of Japan, 2004b. Revised research plan for cetacean studies in the westem North Pacific under special permit (JARPN II). Paper SC/56/O1 submitted to the 56th IWC Scientific Committee, 14pp. International Whaling Commission. 1994. Report of the Scientific Committee, Annex G. Report of the Working Group on North Pacific Minke Whale management trials. Rep. int. Whal. Commn 44:120-44. Kato, H., Kishiro, T., Yoshida, H. and Kawahara, S. 2004. Feasibility of coastal surveys in the JARPN II, from the viewpoint of logistics. Appendix 1, pp4-12. In: Government of Japan (Fujise, Y., Tamura, T., Kato, H. and Kawahara, S. eds.), Some considerations of the feasibility components of the JARPN II research plan. Paper SC/56/O2 submitted to the 56th IWC Scientific Committee, 36pp. Kishiro, T., Kato, H., Ohizumi, H., Yoshida, H., Saito, T., Isoda, T., Tabata, S., Sakakibara, M., Saino, S., Hara., T., Hayashi, T., Miyashita, T., Fukudome, K., Kiwada, H., and Kawahara, S. 2003. Report of the 2002 JARPN II survey in the westem North Pacific. Part II: Coastal component - Coastal Survey off Kushiro, northeast Japan. Paper SC/55/O8 submitted to the 55th IWC Scientific Committee, 26pp. Tamura, T., Hakamada, T., Konishi, K., Fujise, Y., Kishiro, T., Yoshida, H., Ohizumi, H. and Kato, H. 2004. Recalculation of sample size of common minke whales in coastal areas required for estimating consumption of various prey items based on results of JARPN II. Appendix 2, pp13-17. In: Government of Japan (Fujise, Y., Tamura, T., Kato, H. and Kawahara, S. eds.), Some considerations of the feasibility components of the JARPN II research plan. Paper SC/56/O2 submitted to the 56th IWC Scientific Committee, 36pp. Paper SC/56/O16 submitted to the 56th IWC Scientific Committee, 36pp. Yasunaga, G., Kato, H., Kishiro, T., Yoshida, H., Nishiwaki, S., Saito, T., Tabata, S., Okamoto, R., Maeda, H., Nakamura, G., Inoue, S., Otani, S., Iwasaki, T., Kanaji, Y., Mogoe, T., Murase, H., Wada, A., Nakai, K., Matsumoto, A., Gokita, A., Yamazaki, K., Oikawa, H., Onodera, K., Shiraishi, K. and Nagashima, H. 2009. Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2008 - Coastal component off Sanriku. Paper SC/61/O6 submitted to the 61th IWC Scientific Committee, 20pp. Yasunaga, G., Kato, H., Kishiro, T., Yoshida, H., Ishikawa, H., Goto, M., Tabata, S., Maeda, H., Nakamura, G., Inoue, S., Miyakawa, N., Tamura, T., Kumagai, S., Iwasaki, T., Kanaji, Y., Watanabe, H., Hiruta, H., Yamazaki, K., Yonehara, Y., Oikawa, H. and Onodera, K. 2010. Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2009 - (Part II) - coastal component off Sanriku. Paper SC/62/O5 presented to the IWC Scientific Committee, May 2010 (unpublished). 20pp. Yoshida, H., Kato, H., Kishiro, T., Iwasaki, T., Miyashita, T., Ryono, T., Tabata, S., Sakakibara, M., Saino, S., Hara, T., Hayashi, T., Tomizawa, Y., Tamai, K., Okamoto, R., Fukuoka, M., Watanabe, H., Tsunekawa, M. and Kawahara, S. 2004. Report of the coastal survey on common minke whales off Sanriku coast, northeast Japan: the Japanese whale research program under special permit in the western North Pacific – Phase II (JARPN II) in 2003 (Part II) – Coastal component. Paper SC/56/O14 submitted to the 56th IWC Scientific Committee, 31pp. Yoshida, H., Kato, H., Kishiro, T., Iwasaki, T., Miyashita, T., Saito, T., Tabata, S., Morita, Y., Sato, H., Okada, A., Tomizawa, Y., Saino, S., Kuroishi, H., Ebisui, T., Nakai, K., Nishiwaki, S. and Kawahara, S. 2006. Cruise report of the second phase of the Japanese Whale Research Program under Special Permit in the Western North Pacific (JARPN II) in 2005- Coastal component off Sanriku. Paper SC/58/O9 submitted to the 58 k IWC scientific Committee, 30pp.
*²: No. of primary school sightings per 100 n. miles searching.
Table 6. Sex and sexual maturity status of common minke whales collected by the 2012 JARPN II coastal survey off Sannku
Table 8. Weight (kg) of forestomach content of common minke whales collected by the 2012 JARPN II coastal survey off Sanriku
Mitsuhiro Saeki 1 and Genta Yasunaga 2 1 Miyagi Prefecture Fisheries Technology Institute, 97-6 Sodenohama, Watanoha, Ishinomaki, Miyagi 986- 2135, Japan ² The Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan A prey species survey was conducted in the coastal region off Sanriku, northeastern Japan in spring 2012 as a part of JARPNII coastal component off Sanriku. The survey was conducted concurrently with a sampling survey of common minke whales. The survey was conducted in April (16 - 21 April) and May (14 - 18 May). Four stratified blocks were surveyed in April (A, B, C and D) and two blocks (B and C) were surveyed in May.   Zigzag tracklines were set in the blocks. A trawler type RV, Takayo-maru , was used for the survey. Acoustic data were recorded continuously along the tracklines by a quantitative echosounder. Samplings using a midwater trawl net were conducted at 12 stations to identify species and body size compositions. Vertical oceanographic conditions were recorded at 35 stations by using a CTD. Subsurface oceanographic conditions were recorded continuously along the tracklines. JARPN II is designed to contribute to conservation and sustainable use of marine living resources including whales in the western North Pacific, especially within Japan's EEZ (Government of Japan, 2002). One of the major objectives of JARPNII is to study feeding ecology of cetaceans and ecosystem studies, involving studies of prey consumption by cetaceans, prey preference of cetaceans and ecosystem modeling. To accomplish the goal, a sampling survey of common minke whales ( Balaenoptera acutorostrata ) and a survey on biomass estimation of their prey species have been conducted concurrently off Sanriku, Japan as the JARPNII coast component since 2003, except for 2011 when a large earthquake and tsunami affected greatly the region. In this document the results of the prey species survey off Sanriku in 2012 are presented. While the sampling survey of minke whales was conducted in the coastal waters within the 50 n.miles (mainly within 30 n.miles) from Ayukawa, Miyagi prefecture, the prey species survey was conducted in wider area at bottom depths between 20 m and 200 m from 37° 54' N to 38° 40' N off Sanriku, northeastern Japan, to elucidate the distribution and abundance of main prey species. Seven survey blocks (A-G) have been set within the survey block since 2005 for the purpose of biomass estimation of prey species based on a stratified random sampling method using echo-sounder data (Figure 1). Stratification of blocks was based on bottom depth (20, 40, 100, and 200m) and political boundary (boundary between Miyagi and Fukushima prefecture). Because of logistical constraint and Fukushima nuclear accident, only 4 blocks (A, B, C and D ) were surveyed in April, and only 2 blocks (B, C,) were surveyed in May in 2012 (Figure 1). A zigzag track line was set in each block. The waypoints of planned tracklines in each block were shown in Table 1. The survey was conducted in April (16 - 21 April) and May (14 - 18 May). The same blocks and tracklines were surveyed in April and May to see whether the distribution patterns of prey species differed between the months. The survey was conducted during the daytime from an hour after sunrise to an hour before sunset.  Acoustic, trawl and oceanographic surveys were conducted using a trawler-type RV, "Takuyo maru" (Miyagi Prefecture, 120 GT). Data on distribution and abundance of the prey species were recorded by a quantitative echosounder, EK500 (Simrad, Norway) with operating frequency at 38, 120 and 200 kHz. The RV steamed at 9-10 knots along the tracklines. Acoustic data were stored with an aid of software, Echoview (Myriax Software Pty. Ltd., Austlaria). A calibration was carried out in the survey area on 15 April and on 14 May using the copper sphere technique described in EK 500 manual. Vertical oceanographic observations were conducted with CTD. Subsurface (approximately 5m water depth) temperature, salinity and chlorophyll-a were recorded every minute (in time) along the tracklines. Trawl sampling was conducted to identify the species and size compositions of targeting echosigns. The trawl net had a mouth opening of 7 m (width) by 3.5 m (height) and a 3 mm liner cod end. The depth and the height of the mouth of the net were monitored with a net recorder. Towing speed of the trawl net was 2-4 knots. Catches of trawl were identified to the species level and weighed aboard the vessel. For the major species, a sample of 100 animals was taken, and lengths and weights were measured. Scale and standard lengths were used for Japanese anchovy ( Engraulis japonicus ) and sand lance (adult and juvenile, Ammodytes personatus ), respectively. Total length from the tip of the rostrum to the end of the telson was used for krill ( Euphausia pacifica ). Some frozen samples were taken for further analysis in the laboratory. The planned tracklines were almost surveyed by the quantitative echosounder. Trawl was towed at 12 stations. A summary of the midwater trawl samplings was shown in Table 2. CTD casts were conducted at 35 stations. Occurrences of prey species were different between April and May. In April, backscatterings of juvenile sand lance and krill were observed while these of adult sand lance and Japanese anchovy were rarely observed. In May, number of backscatterings of Japanese anchovy was increased. Backscatterings of juvenile sand lance, adult sand lance and krill were also observed in May. Detailed analysis will be conducted in the laboratory and the results will be presented in the near future. We would like to thank the captain of RV "Takuyo-Maru", Mr. Hiroaki Kimura, and his crews who assisted us to collect a valuable data set. This survey was supported by Fisheries Agency of Japan, Miyagi Prefecture and the Institute of Cetacean Research. We thank these institutions for their support. Government of Japan. 2002. Research Plan for Cetacean Studies in the Western North Pacific under Special Permit (JARPN II). IWC/SC/54/O2 submitted to the 54th IWC Scientific Committee Meeting, 115pp.