ABSTRACT
Baird’s beaked whale, Berardius bairdii Stejneger 1933, is known in Japan as tsuchi, tsuchi-kujira or, tsuchin-bo. In addition to these well-known names, whalers in Chiba Prefecture used kokushira for this species and ko-kujira (in two Chinese characters meaning small whale) probably for gray whales (Documents Nos 182 and 183 cited in Kishinoue 1914, in Japanese; see Section 1371), while the same ko-kujira was used for gray whale and Baird’s beaked whales in the Wakayama area (Hattori 1887-1888, in Japanese) Thus, caution is required to avoid misinterpretation The gray whale was called variously koku, koku-kujira, ko-kujira, chigo-kujira, aosagi, or share. Yamase (1760, in Japanese) used asobikujira with a drawing of a whale having a rostrum identifiable as a Baird’s beaked whale but having teeth in both jaws in his book Geishi [Natural History of Whales] Hattori (18871888, in Japanese) accepted the opinion in a book Santei Geishi [Corrections to Geishi] (not seen) by an anonymous author that the name asobi-kujira was due to a mix-up of the Chinese character for tsuchi with another character that looked slightly similar and considered the name incorrect (Kasuya and Yamada 1995, in Japanese) Although the species is dealt with by the International Whaling Commission (IWC) as a small-cetacean species for management purposes (Preface and Section I22), it is the largest species of the family Ziphiidae and is comparable to female sperm whales in body size It reaches 11-12 m; females grow slightly larger than males The dorsal fin is 25-32 cm high, has a concave posterior contour, and is placed at a position about one-third of the body length from the posterior end The head is much smaller than that of the sperm whale, and the proportion of length from the anterior end of the upper jaw to the anterior insertion of the flipper is only 15%–19% of the body length, which is much smaller than the 30% attained by sperm whales of the same size
A slender beak projects 50-60 cm beyond the melon, and the severed head looks like a mallet (tsuchi), which gave rise to the Japanese name No teeth are present in the upper jaw, but there are two or three pairs of flat triangular teeth near the tip of the lower jaw (Kirino 1956; Kuroe 1960, in Japanese) The anterior-most pair is the largest, attaining 10 cm in length and anterior-posterior width and 5 cm in lingual-buccal thickness (Kasuya 1995, in Japanese) The size of the posterior teeth is less than half that of the anterior-most teeth, and they are hidden in the mouth if the jaws are closed The anteriormost teeth are placed beyond the anterior tip of the upper jaw; thus they do not function to grasp food but show abrasion, caused by contact with the sea floor, food, or the skin of other individuals of the same species
The body is dark brown except for an irregular white area along the ventral midline A pair of main throat grooves and
accessory groves are seen in the throat region (Omura et al 1955) These throat grooves are also present in other members of the Ziphiidae and in sperm whales and probably function in suction feeding to increase laryngeal capacity by expanding the throat region The single blowhole is crescent-shaped and is posteriorly concave when closed, which is the same as in another member of the genus B. arnuxii Duvernoy, but differs from the state in other members of the Ziphiidae and all the Delphinoidea species
The anterior end of the melon is often marked with scars, presumably caused by contact with the sea floor while feeding Whales have more flexibility in bending the body ventrally than dorsally, which is similar to our condition Swimming upside down would be a reasonable posture in which to approach the sea floor for feeding on benthic organisms and then return to the water column This is the opposite of surfacing for respiration
Baird’s beaked whales have numerous tooth marks on the dorsal surface from the neck to the dorsal fin, presumably from contact with members of the same species The dorsal surface of older individuals often appears almost whitish with heavy scarring (see frontispiece)
Body weights of a fetus of 169 cm and three postnatals at or below 108 m produced the following relationship between body length (L, cm) and body weight (W, kg) (Kasuya et al 1997):
Log W = 3081 × log L + log(6339 × 10-6), r = 099
This can be rewritten as
W = (6339 × 10-6)L3081
Body weight in many cetacean species is proportional to the 26-28th power of body length (Bryden 1986), which means the body becomes more slender with growth However, the equation above suggests that Baird’s beaked whales do not change body shape with growth It also suggests a body weight of 987 kg for neonates (456 m) and 127 tons for a full-grown female of average body length at 1045 m
Baird’s beaked whales usually live in schools of 3-20 individuals and are found in a tight school at the sea surface This together with body scars on the dorsal surface suggests that they live a social life
Recent whaling for Baird’s beaked whales in the Okhotsk Sea and whale-sighting surveys by Russian scientists in the region were unable to identify the presence of the northern bottlenose whale, Hyperoodon ampullatus, in the Okhotsk Sea, and the conclusion was reached that the species is absent there (Tomilin 1967) While supporting the conclusion of Tomilin (1967), Heptner et al (1976) presented two photographs
and thought to be Baird’s beaked whale(s) However the shape of the melon as well as the direction of concavity of the closed blowhole disagreed with those of Berardius, and were more likely to be of a whale of the genus Hyperoodon Either the species or the location of the photographs is in question
Some Japanese whalers in Abashiri (44°01′N, 144°15′E) on the Okhotsk Sea coast of Hokkaido identified a particular type of whale similar to ordinary Baird’s beaked whales but darker or smaller and more difficult to approach within shooting distance They were called by the fishermen kurotsuchi [black Baird’s beaked whale] or karasu [crow or raven] I remember that biologists of the Whales Research Institute in the 1960s, when I was a young staff member there, often talked about the unidentified species in the Okhotsk Sea with speculation that it might represent a species of Ziphiidae yet to be reported from the sea This idea was documented by Nishiwaki (1965, in Japanese) He noted that whales recorded by Okhotsk Sea whalers as Baird’s beaked whales and were pregnant at a body length below 76 m could possibly represent the northern bottlenose whale Hyperoodon ampullatus Two years later, now referring to the vernacular name kurotsuchi, Nishiwaki (1967) stated, “Considered from the record of the body length of a pregnant female, which is less than 25 ft, and body shape as observed by whalers, the whale cannot be presumed to be Baird’s beaked whale … the author ventures to identify it with Foster’s species [ie, northern bottlenose whale]” The source of data on the small pregnant female was not given in either of the documents mentioned earlier Kasuya (1986) questioned the presence of H. ampullatus in the Okhotsk Sea after examining skulls and teeth of Ziphiidae species available at the time from the sea
T Yamada of the National Science Museum in Tokyo presented new information on the unidentified whales Three stranded unidentified toothed whales were reported on the Hokkaido coast of the southern Okhotsk Sea and Nemuro Strait since June 2008 They were similar to each other and had a body shape similar to that of ordinary Baird’s beaked whale including shape of the blowhole, but one of them (a male) was physically mature at a body length of 66 m Schools of the same small whales have been sighted annually in the Nemuro Strait (44°N, 145°20′E) In addition to the small body size, these whales lacked the tooth marks that are abundant on ordinary Baird’s beaked whales, but they had white scars of cookie-cutter shark bites scattered on the dark body None of the ziphiid species known from the North Pacific agree with these specimens The information given earlier was in Asahi Shimbun Press (2010, in Japanese) and in a personal communication from Yamada in 2010
The unidentified whales agree with Berardius in the direction of the closed blowhole but grow only to 60%–70% of the body length of the ordinary Baird’s beaked whale Less intense tooth marks on the body of these whales suggests some difference in their social behavior I am not aware of any studies on the density of bites of cookie-cutter sharks on Baird’s beaked whales, but such scars are also present on ordinary Baird’s beaked whales taken off Wadaura (35°03′E, 140°01′E) in
Pacific coast of central Japan (Figure 1313) The difference in density of bites, if confirmed, suggests some difference in habitat It should be noted that both the recently identified Berardius-like whales (which are smaller) and ordinary Baird’s beaked whales (which are larger) inhabit the southern Okhotsk Sea in summer
An ex-whaler S Fukuoka (personal communication in February 2014) of Abashiri, who has experienced whaling for minke and Baird’s beaked whales in the Okhotsk Sea, identified three types of Baird’s-beaked-whale-like whales: aka-tsuchi [red Baird’s beaked whale], kuro-tsuchi [black Baird’s beaked whale], and karasu [crow or raven] He described the first type as having numerous scars on the back and swollen dorsal muscles and as the largest of the three types and stated that this type was the same as those taken off the Pacific coast of Japan His description agreed well with our understanding of Baird’s beaked whales dealt with in the main body of this chapter The second type, kuro-tsuchi, was slender, slightly smaller than the first type, and had black pigmentation without such heavy tooth marks as seen on the first type The third type of Fukuoka, karasu, was similar to the second type in coloration but distinct in small body size, growing only to half the size of the first type, which reached 11-12 m Fukuoka also stated that this third type tended more to approach shallower waters if chased by whalers in the Okhotsk Sea than the ordinary Baird’s beaked whales, which preferred deeper waters
The description of the third type, or karasu, agrees with the whales that were stranded on the southern Okhotsk Sea and examined by Yamada and probably with the kuro-tsuchi as described by Nishiwaki (1967), but its taxonomic position is still left to be determined The second type of Fukuoka, kuro-tsuchi, has not been examined by scientists Validity of these two type of animals remains to be confirmed Unless stated otherwise, the following parts of this chapter deal only with ordinary Baird’s beaked whales*
Baird’s beaked whale is endemic to the northern North Pacific (Figure 131) It was described based on a specimen obtained on Bering Island (55°N, 166°15′E) in the western Bering Sea Analysis of mitochondrial DNA has confirmed the taxonomic distinctness of the species from Berardius arnuxii in the southern hemisphere (Dalebout et al 2004) The ordinary southern limit of this species in the eastern North Pacific is off the northern part of the Baja California Peninsula (ca 30°N), but a mass stranding was reported from La Paz (24°N) in the
southern Gulf of California (Aurioles-Gamboa 1992) If the distribution of the species in the Gulf of California and in the Pacific is assumed to be continuous, which is without evidence, the southern limit of the species in the eastern North Pacific can be placed at around the tip of the Baja California Peninsula at about 23°N The range of the species extends north along the west coast of North America to the Aleutian Islands and to Cape Navarin (62°N) in the Bering Sea (Reeves and Mitchell 1993)
The usual southern limit of this species on the Asian side of the Pacific is in Sagami Bay (34°45′–35°19′, 139°E-139°45′E), and the range extends north to the east coast of the Kamchatka Peninsula and the central Okhotsk Sea at latitude 57°N The species is known from the entire Sea of Japan
13.2.2.1 Chinese coast Wang (1999, in Chinese) reported a Baird’s beaked whale taken in the vicinity of the Zhoushan Islands (31°N, 122°E) in the East China Sea in the 1950s and collection of a specimen from the whale The method of the take was not stated but it could have been captured by a whaling operation that existed in the area in those days The species has not been reported from Taiwan Cetacean-sighting cruises conducted by the Fisheries Agency of Japan in January-March and JuneSeptember did not record the species in the East China Sea (Kasuya and Miyashita 1997) The single record was likely a stray or from an unconfirmed population on the Chinese coast; this awaits further surveys in the Bohai and Yellow Seas The shallow water depth, less than 50 m, in the western half of the Yellow Sea and the Bohai Sea and absence of sightings of the species in deeper waters off the Korean coast in the East China Sea suggest that the individual was a stray
Wang (1999, in Chinese) recorded a Chinese whaling operation that lasted from 1953 to 1980 The operation in Daya Bay (23°16′N, 114°25′E) near Hong Kong started in
ended in 1970 The catch was mainly humpback whales but also included some gray and minke whales Another whaling operation with hand harpoons started in 1953 on the Leizhou Peninsula (20°50′N, 110°05′E) and lasted for 2 years Whaling in the northern Yellow Sea started in 1953 off Dalian (38°57′N, 121°38′E) and expanded to the southern Yellow Sea in 1963 using a newly introduced large catcher boat and five smaller vessels that had been in use since earlier years The catch was of fin and minke whales, but it declined after 1965 Japanese whaling off the Goto Islands (33°N, 129°E) in the East China Sea started in 1955 for fin whales, and Korean whalers also took minke whales at the time These operations could have influenced the decline of Chinese whaling at Dalian China ceased all whaling operations in 1980 and joined the International Convention for Regulation of Whaling in the same year Wang (1999, in Chinese) also noted that Taiwan started whaling in 1955 as a joint venture with Japanese whalers or by hiring one or more Japanese gunners, started shipboard flensing in 1979, and continued whaling until 1981 These whaling operations did not record take of Baird’s beaked whales
In the North Pacific, the take of bowhead, right, and gray whales has been prohibited by international convention since the pre-World War II period (Sections I22 and 722), that of humpback and blue whales since 1966, and that of fin and sei whales since 1976 (Table 72) The only great whale species allowed to be taken in the North Pacific in September 1980 when China joined the convention were Bryde’s and minke whales
13.2.2.2 Sea of Japan The Fisheries Agency of Japan carried out extensive cetacean surveys in the eastern part of the Sea of Japan in June to October and recorded sightings of Baird’s beaked whales in June-August They were sighted in almost the entire range of the surveyed area from west of Rebun Island (45°22′N, 141°02′E) to west of Oki Island (36°14′, 133°15′) (Kasuya and Miyashita 1997)
Japanese small-type whaling operated in the Sea of Japan during the post-World War II period and recorded takes of Baird’s beaked whales Omura et al (1955) analyzed the catch statistics for the years 1948-1952 The main grounds for Baird’s beaked whales were in Toyama Bay (36°45′N-37°15′N, 137°–137°30′) and off the west coast of the Oshima Peninsula (42°30′N-43°30′N) in south-western Hokkaido (Omura et al 1955) These whaling grounds of past operations were part of the area where the species was recorded by recent surveys as reported by Kasuya and Miyashita (1997) Since minke whales were the main target of the small-type whaling of the time and Baird’s beaked whales were a secondary target, it is uncertain if the observed season of Baird’s beaked whales in the Sea of Japan, June to August with a peak in July, reflected a real seasonal change in their density Nishiwaki and Oguro (1971) also analyzed similar records of small-type whaling in Japan for the 1965-1969 seasons, but hunting of Baird’s beaked whales was not recorded in the Sea of Japan,
reasons
Presence of Baird’s beaked whales in the eastern Sea of Japan in months other than June-August has been confirmed from strandings: on the coast of Kyoto Prefecture (35°30′N-35°46′N) in October, in Niigata Prefecture (36°59′N-38°33′N) in December and February, in Yamagata Prefecture (38°33′N-39°07′N) in October, and in Akita Prefecture (39°07′–40°20′) in February (Nishimura 1970; Ishikawa 1994, in Japanese) There is a record of the species in April in Peter the Great Bay on the west coast of the Sea of Japan (Tomilin 1967) Kasuya and Miyashita (1997) concluded from these records that Baird’s beaked whales are present in the Sea of Japan year-round
The whaling grounds for this species in the Sea of Japan, in Toyama Bay and off the coast of the Oshima Peninsula, had a common feature, the 1000 m isobath located close to the coast On the Pacific coast of Japan this species at least in the summer season occurs on the continental slope between the 1000 and 3000 m isobaths (Kasuya 1986) It is likely that Baird’s beaked whales in the Sea of Japan also prefer continental slope waters, and the fishing grounds were at places where deep submarine canyons approached the coast If Baird’s beaked whales in the Sea of Japan also prefer the continental slope, it is possible that there are two separate populations on the two sides of the sea Although there is no evidence supporting such a population structure, the hypothesis could be a safe choice for management in the Sea of Japan
Omura et al (1955) compared the body length of Baird’s beaked whales taken by small-type whaling in different grounds and reported that Sea of Japan whales had a smaller modal length than those off the coast of Chiba and Sanriku (37°54′N-41°35′N) on the Pacific coast: 30-32 ft (sexes combined) versus 34-35 ft (males) and 36 ft (females) A similar geographical difference was also observed in maximum body size, which would be more likely influenced by sample size If we remember that the same whalers operated in those days in both the Sea of Japan and Pacific areas, the 3-to 4-ft difference in modal length can be assumed to be a real body-length difference
Kishiro (2007) analyzed external measurements of Baird’s beaked whales taken by small-type whaling in the Sea of Japan (21 taken during 1999-2004), Pacific area (47, 1992-2004), and Okhotsk Sea (34, 1988-2004) All the samples from the first two areas were measured by him Although he did not mention it, his data showed a similar geographical body size difference as that noted by Omura et al (1955) Both the mean body length (940 m) and maximum body length (1015 m) in the Sea of Japan sample were smaller than the corresponding figures (mean 999 m, maximum 1090 m) for the Pacific sample It is very likely that Baird’s beaked whales in the Sea of Japan are about 60-70 cm smaller than those off the Pacific coast of Japan
Kishiro (2007) carried out a multivariate analysis of the external measurements of his sample, adjusting for body size difference, and concluded that the Sea of Japan sample taken off the Oshima Peninsula and the sample from the Pacific coasts of Chiba and Ibaraki Prefectures (35°45′N-36°50′N)
flippers contributed most to the observed morphological difference between the two samples This analysis placed the Okhotsk Sea sample intermediate between the other two samples, but Kishiro refrained from conclusions about it because the measurements were collected by multiple scientists The flipper lengths presented by him were 1259 cm in the Pacific sample and 1149 cm in the Sea of Japan sample (mean of both sexes with body length ≥84 m), which could have reflected the body size difference mentioned earlier These measurements are 126% (Pacific) or 122% (Sea of Japan) of mean body length Age-related change in the proportional size of flippers has not been compared between the two samples from the Pacific and the Sea of Japan
This information supports the idea that the Sea of Japan is inhabited by a Baird’s beaked whale population or populations different from those inhabiting the waters off Chiba and Ibaraki, near the southern range of the species in the western North Pacific The identity of the Okhotsk Sea population is left for further investigation Kasuya (1986) hypothesized that Baird’s beaked whales in the Sea of Japan do not migrate through the four channels that connect the sea with the Okhotsk Sea, North Pacific, and East China Sea The Sea of Japan has a maximum water depth of over 3000 m in the northern part and is connected with the outer seas by the four shallow channels Two of them, the Tsugaru Strait (41°30′N, 140°30′E) opening to the Pacific and the Tsushima Strait (34°N, 129°E) opening to the East China Sea, are the deepest with maximum depths of 130 m The remaining two-the Mamiya or Tatar Strait (50°N, 141°E) and the Soya or La Perouse Strait (45°46′N, 142°00′E), both opening to the Okhotsk Sea-are shallow, with maximum depths of about 20 and 30 m, respectively We know that the species in the Sea of Japan does not usually, if at all, migrate to the East China Sea through the Tsushima Strait (see Section 13221), but there is no evidence that denies movement of the species to the Okhotsk Sea or to the North Pacific Further investigation is required, particularly on possible seasonal movement of the Sea of Japan individuals to the Pacific coast of Hokkaido through the Tsugaru Strait and to the southern Okhotsk Sea through the Soya Strait (Figure 132)
13.2.2.3 Western North Pacific and Bering Sea Before examining the history of hunting Baird’s beaked whales in this region, records of sighting surveys will be discussed The Fisheries Agency of Japan in the early 1980s started a systematic sighting survey of commercially exploited cetaceans in the western North Pacific with the objective of estimating their abundances Japanese waters known to be inhabited by Baird’s beaked whales, a latitudinal range of 34°N-43°N or from the east coast of the Izu Peninsula (34°36′N-35°05′N, 138°45′E-139°10′E) to eastern Hokkaido, were surveyed in the months of July-November, while waters south of the range were surveyed through almost the whole year except for December and March (Figure 132) Using these data, Kasuya and Miyashita (1997) analyzed the distribution of Baird’s beaked whales in the western North Pacific
With the exception of one record of this species in July in Suruga Bay off the west coast of the Izu Peninsula, which can be dealt as an outlier, all the other records occurred east of the peninsula and north of 34°N This is the usual range of this species in the western North Pacific
Japanese cetacean sighting cruises before the cruises analyzed by Kasuya and Miyashita (1997) often had only whalers on board and no scientists, and there remain uncertainties on the species identification of small cetaceans Records of Baird’s beaked whales are not the exception There have been sightings reported in the North Pacific of an unidentified beaked whale apparently similar to the Baird’s beaked whale, now considered to represent Longman’s beaked whale, Mesoplodon pacificus (Pitman et al 1999; Dalebout et al 2003) Trouble with identification could relate to not only this species but other species as well Careful observation of the pigmentation of the body, direction of the blowhole, and body size can distinguish Longman’s beaked whales from Baird’s beaked whales
The asobi-kujira described by Yamase (1760) from the present Wakayama Prefecture (33°26′N-34°19′N, 135°00′E135°59′E) could also be a ziphiid species other than Baird’s beaked whale, because the area is outside the current usual range of that species However, the presence of teeth in both jaws disagrees with any of the Ziphiidae except the Southern Hemisphere species Tasmacetus townsendi Ishikawa (1994, in Japanese) reported a Baird’s beaked whale from Tosa Bay (33°15′N, 133°30′E) or south of the usual range of the species He stated that the species was identified based on skull, mandible, and mandibular teeth Before this record can be evaluated, more information on the specific features used in the identification is needed, together with how the specimen was obtained, whether by stranding or hunting Kasuya and Miyashita (1997) analyzed sightings of Baird’s beaked whales during 1982-1994 and reserved confirmation of the species identification in eight sightings recorded by onboard scientists as Baird’s beaked whales (Figure 132) These were sighted
in 35°N-45°N and east of 145°E under unfavorable weather conditions or by inexperienced observers
Analyses of earlier sighting records made by the crews of scouting boats attached to whaling fleets have concluded that Baird’s beaked whales are distributed continuously from the Japanese coast to the coast of the United States (eg, Ohsumi 1983; Kasuya and Ohsumi 1984), but such records are now believed to contain misidentifications of species and the conclusion has been rejected These scouting boats could have correctly recorded species of large cetaceans hunted by them, but the observers probably did not pay sufficient attention to identification of other smaller species
After rejecting the dubious records off the Pacific coast of Japan, there remain sightings of Baird’s beaked whales that ranged from 34°N near the southern entrance of Sagami Bay on the east coast of the Izu Peninsula to the southern coast of Hokkaido at 43°N (Figure 132) In addition there is one record of a sighting off the southern Kuril Islands Off the coast of Russia, the former USSR’s whaling operated from land stations at the middle (47°N) and northern (52°N) Kuril Islands and recorded take of 109 Baird’s beaked whales in MayNovember (Reeves and Mitchell 1993) Sleptzov (1955, in Japanese) reported records of Baird’s beaked whales from both sides of the central Kuril Islands continuing to Pacific waters off the east coast of the middle of the Kamchatka Peninsula The species has also been reported in the southeastern Okhotsk Sea around the Shiretoko Peninsula (43°40N′–44°19N′, 144°50′E-145°20′E) including the Nemuro Strait in AugustOctober (Figures 132 and 134), but it is known to occur also in early spring in the Nemuro Strait (see Section 13224) These records indicate distribution of the species at least in the summer off the east and west coasts of the entire Kuril Islands chain The species probably passes through the Kuril Islands, which have several passes deeper than 1000 m
Tomilin (1967) reported sightings of numerous Baird’s beaked whales made during whaling operations in 1934 (Table 131) As the USSR’s whaling of the time targeted fin, humpback, and sperm whales (Sleptzov 1955, in Japanese),
not necessarily mean absence of the species in the region However, the recorded sightings will be used for present purposes as far as species identification is reliable Tomilin (1967) indicated that the northernmost record was around Cape Navarin at 62°16′N, 179°06′E and that local marine mammal hunters in the Bering Strait area did not know about the species He concluded that the northern limit of the species in the Bering Sea is on the continental shelf edge extending from Cape Navarin toward the east or southeast Baird’s beaked whales have been recorded from St Matthew Island and the Pribilof Islands on the edge of the continental shelf (Rice 1998) This does not disagree with the opinion of Tomilin (1967) Thus, the northern limit of the distribution of this species in the Bering Sea is likely on a line connecting Cape Navarin, St Matthew Island, the Pribilof Islands, and the tip of the Alaska Peninsula
13.2.2.4 Okhotsk Sea A triangular oceanic basin (Kuril Basin) is situated in the southeastern Okhotsk Sea The eastern margin of the basin extends from around 50°N, 163°E off the northern Kuril Islands, along the Kuril Islands, to the southern Kuril Islands at around 44º30′N, 145º40′E The southwestern border of the basin is near southern Sakhalin Island at around 47°N, 144ºE Shallower water extends to the north of the Kuril Basin, with the depth decreasing from about 2000 m at the northern edge of the basin to 1000 m at 55°N and less further north In winter most of the Okhotsk Sea is covered with ice, leaving a small open area in the southeastern part
The Fisheries Agency of Japan operated systematic shipboard surveys for cetaceans in the Okhotsk Sea (Figure 132) The surveys covered most of the area outside the territorial waters of Russia (12 nautical miles) and months from May to October with major effort in August and September Some sightings of Baird’s beaked whales were made in each month (Kasuya and Miyashita 1997) They occurred mostly in the southern Okhotsk Sea, ranging from 48°N off southern Sakhalin Island to the Shiretoko Peninsula and the northern coast of Hokkaido (both at 44°N) (Figure 132) Another two sightings were in August near the northern coast of Sakhalin Island at 55°N and off the Pacific coast of the southern Kuril Islands, on the continental slope near the 1000 m isobath
Fedoseev (1985) reported to the Scientific Committee of the IWC on the presence of Baird’s beaked whales in the northern Okhotsk Sea, based on data obtained during aerial sighting surveys for seals The surveys were made in AprilMay of 1979 and 1981 along track lines set at 20-30 km intervals and recorded a total of 70 Baird’s beaked whales in waters between the northern tip of Sakhalin Island and south of Okhotsk City, at 54°N-59°N, where concentrations of bowhead whales and belugas were also observed In addition to these sightings, Fedoseev recorded one sighting of Baird’s beaked whales in the central Okhotsk Sea and two in waters west of the southern Kuril Islands The whales were in dense schools of 7-11 traveling at high speed through open water in the sea-ice field and submerging synchronously
TABLE 13.1 Baird’s Beaked Whales Recorded by Soviet Whalers Operating in the Western Bering Sea and off the East Coast of the Kamchatka Peninsula
Baird’s beaked whales in the southern range of the species off the Pacific coast of Japan in the Chiba and Ibaraki areas, but their body length was not estimated and there remains a possibility that some of these observation, particularly those in northern waters, might represent the small “Baird’s-beaked-whale-like” whale known from the southern Okhotsk Sea (Section 131)
Water depths at the sighting of Baird’s beaked whales were estimated on a map to be in a range between 200 and 1000 m (Fedoseev 1985) Fedoseev (1985) noted three Baird’s beaked whales sighted in the same area in December 1983, when the sea was not covered by ice, and concluded that the whales observed by him were not migrants proceeding toward the north through melting sea ice but year-around residents of the Okhotsk Sea
The presence of Baird’s beaked whales (or “Baird’s-beakedwhale-like” whales) in the northern Okhotsk Sea throughout the year suggests that they represent a population to be distinguished from those in the Sea of Japan and in waters off the Pacific coasts of central Japan We know that Baird’s beaked whales are also present along the Hokkaido coast of the Okhotsk Sea and the Pacific in the summer through autumn and presumably in other seasons too (see Section 1323) and that distribution of the species in the northern and southern Okhotsk Sea is possibly discontinuous Based on these observations, Kasuya and Miyashita (1997) proposed a hypothesis of two Baird’s beaked whale populations in the Okhotsk Sea, that is, a southern Okhotsk Sea population and a northern Okhotsk Sea population Weighing of this hypothesis against the presence of “Baird’s-beaked-whale-like whales” has not been carried out at the time of this writing Baird’s beaked whales taken from the southern concentration were analyzed by Kishiro (2007) and found to disagree, although inconclusively, with the same species inhabiting the Chiba-Ibaraki area in the Pacific and Sea of Japan (Section 13222) The identity of the population off the Pacific coast of Hokkaido and hunted off Kushiro (Table 1314) also needs to be analyzed in comparison with those in nearby waters, that is, the Sea of Japan, the southern Okhotsk Sea, and the Chiba-Ibaraki area, for population identity
Baird’s beaked whales are known to occur on the Okhotsk Sea side of the Nemuro Strait at around 44°N, 145°20′E, which connects the Okhotsk Sea and the Pacific in MarchApril in the presence of ice floes (Ishii 1987, in Japanese; personal communication of H Sato in 1998) through to October (Photo in the frontispiece; Walker et al 2002; Fukuoka 2014, in Japanese) Walker et al (2002) examined 15 individuals taken in August and September off Rausu in the Nemuro Strait at 44°N-44°20′N for their stomach contents analyses, which indicated that these individuals were probably feeding at a water depth of about 200 m (Table 133) It should be noted that the species occurs there in early spring when sea ice can still remain Although it still remains to be confirmed whether Baird’s beaked whales pass through the Nemuro Strait (about 20 m deep) to travel between the Pacific and the Okhotsk Sea, there are sufficient sightings that suggest communication of
Islands near the Nemuro Strait
We know that a population of Dall’s porpoises winters in the Sea of Japan and summers in the southern Okhotsk Sea One of their two northward migration routes is a short cut through the Soya Strait, and the other is a distant route to enter the Pacific through the Tsugaru Strait and then into the Okhotsk Sea through the southern Kuril Islands However, another Dall’s porpoise population that winters off the Sanriku Region does not use the Tsugaru/Soya route but migrates through the Kuril Islands to reach a summering ground in the central Okhotsk Sea This type of asymmetry of migration route between populations might be a reflection of geological history and might also be expected for Baird’s beaked whales off Japan
13.2.3.1 Distribution Almost nothing is known about the winter range of Baird’s beaked whales in the western North Pacific The usual summer range on the Pacific coast of Japan is from east of the Izu Peninsula at 139°E to north of Miyake Island at 34°N Figures 132 and 133 represent the summer distribution in this range Sighting cruises presented in Figure 133 covered the months of June to September 1984 and were conducted with the purpose of investigating the distribution of sperm whales and Baird’s beaked whales I was on board the cruises from July 7 to August 6 to cover the area north of 34°N and west of
numerous sighting of Baird’s beaked whales but none of sperm whales The track lines were set perpendicular to the coastline There were also some additional saw-tooth tracks because of the statement by Nishiwaki and Oguro (1971), who analyzed whaling records, that Baird’s beaked whales seemed to inhabit waters outside the 1000 m isobath My cruise confirmed this and obtained the additional information that the distribution was limited to waters shallower than 3000 m It was very impressive to find the species every time the vessel entered this depth range The furthest eastern (not shown in Figure 133) and southern track lines were surveyed by other scientists and resulted in only one sighting of Baird’s beaked whales (close to 34°N as shown in Figure 133) and a limited number of sperm whales These cruises made it evident that Baird’s beaked whales in summer inhabit very limited coastal waters off the Pacific coast of Japan but not the more offshore western North Pacific
Baird’s beaked whales taken off the Pacific coast of Chiba Prefecture and processed at a land station at Wadaura were known to feed on deep-water bottom fish (Section 1331) Sometimes we found stones in their stomachs, which were often larger than a child’s fist and could not have been acquired via a fish stomach Additionally we found numerous scratches on the anterior portion of the melon caused by contact with some hard substance, perhaps the sea floor These data suggest that Baird’s beaked whales off the coast of Chiba and nearby Ibaraki Prefectures, at latitudes 34°N-37°N, feed on deep-sea fish on the sea floor The continental slope area at depths of 1000-3000 m is probably inhabited by the fish species preferred by Baird’s beaked whales (Section 133)
The continental slope with depth of 1000-3000 m is not limited to north of 34°N off the Pacific coast of Japan It extends westward along the southern coast of Japan to reach the east coast of Taiwan through the Japanese Nansei Islands [Southwestern Islands] It also extends southward along the submarine ridge to the Bonin Islands However, we do not have confirmed records of Baird’s beaked whales in these waters, and some factors other than water depth are expected to be working in the distribution of Baird’s beaked whales in this case The sea surface temperature, 23°C-29°C at the position of sighting the species in July-August, does not seem to be the controlling factor, but deep-sea temperature is a possibility The southern limit of Baird’s beaked whales in summer is correlated with water temperature of 15°C at a depth of 100 m This water temperature is used by oceanographers as an indicator of the front of the warm Kuroshio Current (Section 1236), and the position does not exhibit much seasonal fluctuation The mid-or deep-water environment seems to regulate distribution of Baird’s beaked whale or its prey species (Kasuya 1986)
13.2.3.2 Seasonal Movements and Population Structure
The southern coast of Hokkaido (42°N-43°30′N) is probably the place where Baird’s beaked whales in May make their first appearance within the overall range of the species along the Japanese Pacific coast (Kasuya and Miyashita 1997)
found along the entire extent of the coastline from Hokkaido (43°N) in the north to the Izu area (north of 34°N and east of 139°E) in the south, and this distribution remained the same through August-September (Figure 132) Limited sighting effort in October recorded them in a limited area off the coasts of Aomori (40°27′N-41°30′N) and Hokkaido (41°30′N-45°30′N) Prefectures and suggested possible disappearance from the area off the Chiba coast (south of 36°N) In November, our survey was limited to only south of 38°N and resulted in no sightings of the species These observations allow the following deduction
Baird’s beaked whales first arrive off the Pacific coast of Hokkaido in May and extend their range south in summer to the Sagami Bay area east of the Izu Peninsula, which is the southwestern limit of the usual range of the species After the summer, they disappear from the southwestern habitat, remaining only off the Hokkaido coast in October, and totally disappear from the Pacific coast of Japan in November If this deduced pattern is accepted, questions remain to be answered: (1) what is their wintering ground and (2) what is the actual movement of individual whales (if they move north/south or vary in timing of arrival/departure from/to the unknown wintering ground)?
