Prey consumption and feeding habits of three baleen whale species in the western North Pacific (PICES / W3) Tsutomu TAMURA and Kenji KONISHI

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1 Prey consumption and feeding habits of three baleen whale species in the western North Pacific (PICES / W3) Tsutomu TAMURA and Kenji KONISHI 1

2 Outline of JARPN II -1- Research area : From 14E to 17E Research period : From May to September Research objectives 1. Feeding ecology of whales and ecosystem studies 2. Monitoring environmental pollutants in cetaceans and the marine ecosystem 3. Stock structure 2

3 Outline of JARPN II -2- Common minke whale (Balaenoptera acutorostrata) Body length 7 m Body weight 5 t 22 inds./year Sei whale (Balaenoptera borealis) Body length 14 m Body weight 22 t 1 inds./year Bryde s whale (Balaenoptera edeni) Body length 13 m Body weight 16 t Sperm whale (Physeter macrocephalus) Body length Male: 15m, Female: 11m Body weight Male: 4t, Female: 18t 5 inds./year 1 inds./year 3

4 Outline of JARPN II -3- Measurement of body weight Identification of stomach contents Sampling of stomach contents Measurement of stomach contents The relative prey composition (%) by weight of each prey species (RW) RW = (W i / W all ) 1 W i = the weight of contents containing prey group i W all = the total weight of contents analyzed. 4

5 Prey species of baleen whale species Copepods (Neocalanus spp.) Krill (Euphausia pacifica) Japanese anchovy (Engraulis japonicus) Chub mackerel (Scomber japonicus) Pacific saury (Colorabis saira) Japanese flying squid (Tadarodes pacificus) Sei whale Bryde s whale Minke whale # Differences in feeding habits among three baleen whale species Minke whale Higher trophic level prey (Flying squid) Sei whale Lower trophic level prey (Copepods, Krill) Bryde s whale Lower trophic level prey (Krill, Japanese anchovy) 5

6 Prey species of sperm whales Deep-Sea /epipelagic squids Taningia danae (ML 65cm) Beaks of neon flying squid Onykia robusta (ML 13cm) Mesopelagic /bottom fish Himantolophus groenlandicus (SL 23cm) Otholis of walleye pollock Trachipterus trachypterus (SL 158cm) # Main prey species were deep-sea / epipelagic squids and mesopelagic / bottom fishes 6

7 Prey sizes consumed by baleen whales Japanese anchovy Pacific saury Mackerels Count Minke Count Minke Count Minke Count Count Sei Bryde s Count Sei BL (mm) Count Count Sei Bryde s BL (mm) BL (mm) Minke Sei > Bryde s Minke > Sei Minke > Sei Bryde s Differences of prey sizes among three baleen whale species The minke whale fed on bigger prey species 7

8 Seasonal and geographical change of prey species Early (May-June) Late (July-Sept.) Early (May-June) Late (July-Sept.) Minke whale 5 N 5 N Saury Saury *Coastal area (East off Hokkaido): Walleye pollock, Common squid E E Sei whale 5 N 5 N 45 4 Copepods 45 4 Copepods Copepods Copepods E E Bryde s whale 5 N 5 N 45 4 Krill 45 4 Krill E E ; Copepods; Saury; Mackerels; krill Japanese anchovy is most important prey species 8

9 Estimation of the numbers of whales distributed Early (May-June) Late (July-Sept.) Sighting survey (22-27) Common minke whale 7,338 (CV.71) 2,976 (CV.52) Sei whale 7,744 (CV.27) 5,46 (CV.3) Bryde s whale 1,677 (CV.89) 9,797 (CV.31) Sperm whale 15,929 (CV.44) 2,292 (CV.41) Hakamada et al. (29) 9

10 Estimation of daily prey consumption (a) D = 4.186aM.75 ; F = D / E Perez et al. (199) * PICES 2 * a=317 for toothed whales, 192 for baleen whales (b) D = 863.6M.783 ; F = D / E (c) D = M.524 ; F = D / E Boyed (22) Sigurjónsson and Víkingsson (1997) D : Daily prey consumption (KJ per day) F : Daily prey consumption (kg per day) M : Mean body weight of whales (kg) E : Caloric value of prey species (KJ per kg) Feeding period : 15 days (May to September) 2.2 F Uncertainty of several prey consumption model Comprehensive review of the estimates of consumption (Leaper and Lavigne 27; Tamura et al. 29) 1

11 Daily prey consumption by three models Daily consumption (kg) 1,8 1,5 1, Minke Bryde s Sei b a c 5, 1, 15, 2, 25, 3, 35, 4, Observed stomach contents Species Sex maturity N Average S.D. Max. Min. Minke IM MM IF MF Sei IM MM IF MF , Bryde's IM MM IF MF Body mass (kg) E : Caloric value of prey species (KJ per kg) = 5,45 KJ/kg Minke whale Sei whale Bryde s whale kg per ind./day 221 1,5 kg per ind./day kg per ind./day a: D = 1,329.9M.75 /E (Perez et al. 199) b: D = 863.6M.783 /E (Sigurjónsson and Víkingsson 1997) c: D = 2,529.2M.524 /E (Boyed 22) 11

12 Total prey consumption (tons) during feeding season All Prey species Common minke whale Sei whale Bryde's whale Total Sub-area 7 Sub-area 8 Sub-area 9 Total Sub-area 7 Sub-area 8 Sub-area 9 Total Sub-area 7 Sub-area 8 Sub-area 9 Total (t) Copepods.3 9 5,887 5,897 1,347 2, ,1 269, ,138 Krill 13,43 2,553 2,372 18,328 91, , ,323 62,929 29,86 1,429 13, ,87 B.L < 8 mm ,963 11,179 8,325 58,468 75,958 7,366 43,7 189,33 247,946 B.L > 8 mm 53,223 (Eq-a 9,51Perez 4,346 et al. 66, ) , , ,28 million 39,696tons 42, ,334 21,61 491,51 Saury 2,529 3,213 22,498 28, ,244 15,241 43,481 Mackerels ,974 8, ,372 56,59 118,432 2,45 9,844 1,573 13,461 14,23 Walleye pollock 15,54 (Eq-b Sigurjónsson 6 15,51 and Víkingsson 1997 ) 1.6 million tons 15,51 Japanese flying squid Sardine Pacific pomfret (Eq-c Boyed ) million tons 296 Salmonids Min. armed squid 1,281 1,281 1,281 Attka mackerel Oceanic lightfish 17,45 17,45 17,45 Other fish Other Squid Total 145,33 94, ,69 Total consumption 1,584,13 t Prey consumption of sperm whales:.4-2. million tons 12

13 The feeding impact by three baleen whale species on fish Prey species Prey consumption (tons) Fisheries Resources Equation-1 (Perez et al. 199) Minke Sei Bryde's Total catch (tons) % (tons) % Japanese anchovy thousands tons Japanese anchovy 54,69 324, , ,585 33, ,8, 18. Pacific saury 32,695 18,311 51,6 42, ,1, 5.1 Pacific saury thousands tons Mackerels 5,292 85,957 11,274 12,523 41, 25. 4,5, 2.3 Equation-2 (Sigurjonsson and Vikingsson 1997) Mackerels thousands tons Japanese anchovy 46, , , ,981 33, ,8, 16.1 Pacific saury 28,138 16,528 44,666 42, 1.6 1,1, 4.4 Mackerels 4,549 77,633 1,63 92,245 41, ,5, 2. Equation-3 (Boyed 22) Japanese anchovy is most important prey among three baleen whales Japanese anchovy 15,696 65,942 16, ,23 33, 57. 4,8, 3.9 Pacific saury 9,25 3,712 12,917 42, 3.1 1,1, 1.3 There Mackerelsis the possibility 1,51 17,358 of direct 2,47 interaction 21,329 between 41, baleen 5.2 4,5, whales.5 and important commercial fisheries such as Japanese anchovy and mackerels 13

14 Summary of results ~ the impact on Japan s s fisheries resources ~ Differences in feeding habits among three baleen whale species Differences of prey sizes among three baleen whale species The smaller minke whale fed on bigger prey species Japanese anchovy is most important prey among baleen whales Total prey consumption by three baleen whale species during feeding season is million tons There is the possibility of direct interaction between baleen whales and important commercial fisheries such as Japanese anchovy and mackerels 14

15 Future tasks Up-dating PICES Scientific Report 14 on prey consumption by marine birds and mammals in the PICES region 1) Abundance 2) Prey composition JARPN II (Japan), POWER sighting (IWC), Domestic sighting (Japan) JARPN II, Estimation by some resources 3) Days of occupancy 4) Prey consumption Estimation by some resources 1) +2) +3) 15

16 Up-dating abundance of cetaceans after 2 English name Japanese name Year Abundance A rea Resource Humpback whale ザトウクジラ 27 1, North Pacific IWC-web site Gray whale コククジラ western North Pacific IW C -web site Right whale セミクジラ O khotsk sea Miyashita and Kato (1998) Sei whale イワシクジラ , North Pacific Hakamada et a l. (24) Common minke whale ミンククジラ , North Pacific-Okhotsk Sea IWC-web site Bryde's whale ニタリクジラ ,51 western North Pacific IW C -web site Sperm whale マッコウクジラ ,112 western North Pacific Kato and M iyashita (1998) Dall's purpose (Truei type) イシイルカ , Sea of Japan-O khotsk S ea 宮下ほか (2 7a) Dall's purpose (Dalli type) , North Pacific-Okhotsk Sea 宮下ほか (2 7a) Striped dolphin スジイルカ , western North Pacific Miyashita (1993a) , western North P acific* 南川ほか (27) Pantropical spotted dolphin マダライルカ , western North Pacific Miyashita (1993a) , western North Pacific 南川ほか (27) Bottlenose dolphin ハンドウイルカ , western North Pacific Miyashita (1993a) , western North Pacific 南川ほか (27) Short-finned pilot whale コビレゴンドウ , western North Pacific Miyashita (1993a) Southern-form ( マゴンドウ ) , western North Pacific 南川ほか (27) False killer whale オキゴンドウ , western North Pacific Miyashita (1993a) , western North Pacific 南川ほか (27) Risso's dolphin ハナゴンドウ , western North Pacific Miyashita (1993a) , western North Pacific* 南川ほか (27) Pacific white-sided dolphin カマイルカ , Coastal area around Japan 宮下ほか (2 7b ) , N orth Pacific Miyashita (1993b) Killer whale シャチ ,3 North Pacific-Okhotsk Sea 宮下 (28) スナメリ , Around Japan Yoshida (25) Northern right whale dolphin セミイルカ , N orth Pacific Miyashita (1993b) *: Northern part of 3 N degree. Shimada et al. 28 Kato et al

17 Thank you for your attention! 17