Journal of Fish Biology (2014) 84, 243–246

doi:10.1111/jfb.12273, available online at wileyonlinelibrary.com

Northernmost record of a whale shark Rhincodon typusfrom the Sea of Okhotsk

T. Tomita*†, T. Kawai*, H. Matsubara‡, M. Kobayashi‡ andS. Katakura§

*Hokkaido University Museum, 3-1-1, Minato-cho, Hakodate 041-8611, Hokkaido, Japan,‡Department of Aquatic Biology, Faculty of Bioindustry, Tokyo University of Agriculture,193, Yasaka, Abashiri 099-2493, Hokkaido, Japan and §City of Mombetsu, 1, Kaiyokoen,

Mombetsu 094-0031, Hokkaido, Japan

(Received 12 May 2013, Accepted 10 October 2013)

The whale shark Rhincodon typus is the world’s largest fish and it occurs in tropical, subtropicaland warm temperate waters. Here, the northernmost record of R. typus is reported, when it wasfound in the Sea of Okhotsk for the first time. This occurrence can be explained by the unusuallyhigh sea surface temperature during the summer of 2012.

© 2014 The Fisheries Society of the British Isles

Key words: Chondrichthyes; distribution; Hokkaido; Orectolobiformes; sea surface temperature.

The whale shark Rhincodon typus Smith 1828 (Elasmobranchii, Orectolobiformes,Rhincodontidae) is the world’s largest fish, reaching at least 12 m in total length(LT; Colman, 1997; Compagno, 2001). On 2 October 2012, a R. typus was founddead at 44◦ 22′ 50′′ N; 143◦ 21′ 44′′ E in a set net for chum salmon Oncorhynchusketa (Walbaum 1792) and pink salmon Oncorhynchus gorbuscha (Walbaum 1792)off Mombetsu (Hokkaido, Japan) (Fig. 1).

The specimen was an immature male of 4·58 m LT and 880 kg body mass (seeadditional measurements in Table I). It was easily distinguished from other largeshark species because of its slightly flattened head, terminal mouth, long straightgill openings, prominent lateral ridges on its flanks and the prominent pattern ofwhite spots between vertical and horizontal stripes, reminiscent of a checkerboardpattern (Compagno, 2001). Following assessment of its external measurements, thepectoral, pelvic and caudal fins were removed from the specimen and preserved forfurther investigation at the Hokkaido University Museum (Hakodate, Japan; HUMZ215293). The rest of the body was disposed of.

This specimen was the first confirmed occurrence of R. typus in the Sea ofOkhotsk. Rhincodon typus mainly occurs between 30◦ N and 35◦ S in the westernPacific Ocean (Compagno, 2001). The species rarely occurs at latitudes north of

†Author to whom correspondence should be addressed. Tel.: +81 138 40 5553; email: t-tomita@museum.hokudai.ac.jp

243

© 2014 The Fisheries Society of the British Isles

244 T. T O M I TA E T A L .

40°

30°

50°

140°130°

Mombetsu

Sea of Japan

North Pacific

Sea of Okhotsk

HUMZ 215293(44° 22′ 50′′ N, 143° 21′ 44′′ E)

Yano et al. (2002)

Hokkaido

Hokkaido

143°

44°

Fig. 1. Location map of male Rhincodon typus , 4.85 m total length (museum catalogue number HUMZ215293). Grey area in the left figure represents the limits to distribution suggested by Compagno (2001).

40◦ N. The northernmost record of R. typus in the western Pacific region is that ofUchida (1995), who noted rare occurrences of the species off southern Hokkaido(Japan), but detailed information (e.g . identification methods, dates and locations ofsightings) was not provided. The most reliable northernmost report in the westernPacific Ocean is based on a specimen collected in Mutsu Bay (41◦ 13′ N; 140◦ 46′E), Aomori, Japan (Yano et al., 2002) (Fig. 1). High-latitude occurrences have alsobeen reported from the north-eastern Pacific Ocean, off Patrick’s Point, California(41◦ 10′ N; 124◦ 15′ W) and the north-western Atlantic Ocean, off Nantucket Island,Massachusetts, U.S.A. (42◦ 02′ N; 62◦ 50′ W and Bay of Fundy, Canada (44◦ 15′19′′ N; 67◦ 44′ 07′′ W) (Gudger, 1952; Ebert et al., 2004; Turnbull & Randell,2006). The current record is the northernmost record worldwide, and extends thenorthern record of the species by over 3◦ latitude in the western Pacific Ocean. Thisoccurrence was also the first reliable record of this species that was found in coldtemperate waters in the western Pacific Ocean.

As R. typus is unlikely to be able to survive the severe winter conditions in the Seaof Okhotsk, it is possible that the specimen in this study travelled north followingthe warm Tsushima Current, and entered the Sea of Okhotsk through the La Perouse(Soya) Strait during summer 2012. All high-latitude sightings of R. typus north of40◦ N have been made during summer or early autumn (Gudger, 1952; Yano et al.,2002; Ebert et al., 2004; Turnbull & Randell, 2006). This suggests that high-latitudeoccurrences of this species depend on a relatively high water temperature. Basedon data from fishing vessels for skipjack tuna Katsuwonus pelamis (L., 1758) inthe north-west Pacific Ocean from 1955 to 1967, sightings of R. typus were madein areas having a sea surface temperature (SST) of 18–30◦ C (mostly 21–25◦ C)(Iwasaki, 1970). This temperature preference of R. typus is supported by recentsatellite tracking data for south-east Asia and Western Australia (Eckert & Stewart,2001; Wilson et al., 2006). The Okhotsk Tower (44◦ 20·2′ N; 143◦ 22·9′ E, 9·5 mwater depth, 1 km off Mombetsu) is a marine observatory station in the Sea of

© 2014 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 243–246

R H I N C O D O N T Y P U S I N T H E S E A O F O K H OT S K 245

Table I. Morphometric measurements of (male Rhincodon typus , 485 m total length(museum catalogue number HUMZ 21529)) from the Sea of Okhotsk

cm %LT

Total length (LT) 458·0 100·0Fork length 393·0 85·8Precaudal length 359·5 78·5Pre-second dorsal length 284·0 62·0Pre-first dorsal length 196·5 42·9Head length 102·5 22·4Prebranchial length 71·8 15·7Prespiracular length 28·0 6·1Preorbital length 15·7 3·4Prepectoral length 111·0 24·2Snout-vent length 246·0 53·7Interdorsal space 52·2 11·4Dorsal-caudal space 40·5 8·8Pectoral-caudal space 103·0 22·5Vent-caudal length 212·0 46·3Interorbital space 85·0 18·6Mouth width 64·0 14·0Clasper outer length 12·4 2·7Clasper inner length 20·8 4·5Clasper base width 4·2 0·9

Okhotsk. In the water around the tower, the monthly mean SST during September2012 (20·8◦ C) was 1·8◦ C higher than the mean September SST from 1997 to 2011.Globally, 2012 was the ninth hottest year on record since 1880 according to the SSTdata from National Aeronautics and Space Administration (NASA). This suggeststhat the high SST during summer 2012 may explain the unusual occurrence of R.typus found in the Sea of Okhotsk.

We are grateful to W.J. Richards (National Marine Fisheries Service, Southeast FisheriesScience Center, NOAA) for his valuable comments and English corrections. We also thankthe director of set net section Hiroaki Iida, the crew members of F.V. 58 Shotoku Maru(Mombetsu Fisheries Cooperative Association) and K. Yoshiyama (Hokkai Minyu NewspaperInc.) for providing data and specimens. Mombetsu Fisheries Cooperative Association staff, theTokyo University of Agriculture, and HUMZ at Hokkaido University undertook preservationof the specimen. A part of this project was supported by the Tokyo University of AgricultureStrategic Research Program (TUA-SRP).

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© 2014 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 243–246