northernmost record of a whale shark ...

Download Northernmost record of a whale shark
               Rhincodon typus
               from the Sea of Okhotsk

Post on 01-Apr-2017

213 views

Category:

Documents

1 download

Embed Size (px)

TRANSCRIPT

  • Journal of Fish Biology (2014) 84, 243246

    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 worlds 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 worlds 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 458 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

    140130

    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 46E), Aomori, Japan (Yano et al., 2002) (Fig. 1). High-latitude occurrences have alsobeen reported from the north-eastern Pacific Ocean, off Patricks 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 1519 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 1830 C (mostly 2125 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 (44 202 N; 143 229 E, 95 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, 243246

  • 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) 4580 1000Fork length 3930 858Precaudal length 3595 785Pre-second dorsal length 2840 620Pre-first dorsal length 1965 429Head length 1025 224Prebranchial length 718 157Prespiracular length 280 61Preorbital length 157 34Prepectoral length 1110 242Snout-vent length 2460 537Interdorsal space 522 114Dorsal-caudal space 405 88Pectoral-caudal space 1030 225Vent-caudal length 2120 463Interorbital space 850 186Mouth width 640 140Clasper outer length 124 27Clasper inner length 208 45Clasper base width 42 09

    Okhotsk. In the water around the tower, the monthly mean SST during September2012 (208 C) was 18 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).

    References

    Colman, J. G. (1997). A review of the biology and ecology of the whale shark. Journal ofFish Biology 51, 12191234.

    Compagno, L. J. V. (2001). Sharks of the World: An Annotated and Illustrated Catalogueof Shark Species Known to Date, Vol. 2. Bullhead, Mackerel and Carpet Sharks (Het-erodontiformes, Lamniformes and Orectolobiformes). Rome: FAO.

    Ebert, D. A., Mollet, H. F., Baldridge, A., Thomas, T., Forney, K. A. & Ripley, W. E.(2004). Occurrence of the whale shark, Rhincodon typus Smith 1928, in Californiawaters. Northwestern Naturalist 85, 2628.

    2014 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 243246

  • 246 T. T O M I TA E T A L .

    Eckert, S. A. & Stewart, B. S. (2001). Telemetry and satellite tracking of whale sharks, Rhin-codon typus , in the Sea of Cortez, Mexico, and the north Pacific Ocean. EnvironmentalBiology of Fishes 60, 299308.

    Gudger, E. W. (1952). Northernmost record of the whale shark. Science 116, 432433.Iwasaki, Y. (1970). On the distribution and environment of the whale shark, Rhincodon

    typus , in skipjack fishing grounds in the western Pacific Ocean. Journal of the Collegeof Marine Science and Technology, Tokai University 4, 3751.

    Turnbull, S. D. & Randell, J. E. (2006). Rare occurrence of a Rhincodon typus (whale shark)in the Bay of Fundy, Canada. Northeastern Naturalist 13, 5758.

    Uchida, S. (1995). Whale shark. In Basic Data for the Japanese Rare Wild Animals II (JapanFisheries Resource Conservation Association, ed), pp. 146153. Tokyo: FisheriesAgency of Japan (in Japanese).

    Wilson, S. G., Polovina, J. J., Stewart, B. S. & Meekan, M. G. (2006). Movements of whalesharks (Rhincodon typus) tagged at Ningaloo Reef, Western Australia. Marine Biology148, 11571166.

    Yano, K., Sugimoto, T. & Nomura, Y. (2002). Capture records of manta ray, Manta birostris ,and whale shark, Rhincodon typus , at Mutsu Bay, Aomori, Japan. Report of JapaneseSociety for Elasmobranch Studies 39, 813.

    2014 The Fisheries Society of the British Isles, Journal of Fish Biology 2014, 84, 243246