The effect of environmental factors on distribu5on of Walleye pollock (Theragra chalcogramma) juveniles in Funka Bay and vicinity, Hokkaido, Japan

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1 PICES 2012 Annual Meeting, Hiroshima, Japan, October 16, 2012 The effect of environmental factors on distribu5on of Walleye pollock (Theragra chalcogramma) juveniles in Funka Bay and vicinity, Hokkaido, Japan Yohei Kawauchi (Hokkaido University), Masayuki Chimura, Takashi Muto, Masamichi Watanobe and Kazushi Miyashita

2 Transition of food organisms for Japanese walleye pollock stock (JPS) In juvenile stage (3 4 months from hatching ) (e.g., Nakatani et al. 2003) Psudocalnus etc. Neocalanus, Eucalanus etc. Kawauchi et al Large juv. Oyashio current water Deep, Cold and Salty Small juv. Surface water of coastal Oyashio current Shallow Warm and Sweet They can feed foods appropriate for each body size If juveniles grow and survive in the optimal environment Larger body size in the after life stages & Low prey Improvement of survival potential to recruitment Yamamura 2012 TL (mm) Detph (m)

3 Diel vertical migration of JPS Diel Vertical Migration (DVM) Changing the distribution vertically during day and night (e.g., Tanaka et al. 2009) Day Night Pollock juveniles... Day Large aggregation in mid-water Night Scatter or float Miyashita et al. 2004;2008 Stay in the suitable environment using DVM is important Objec&ves To reveal diel change of juvenile distributions and environments To verify the feeding habitat in the transition period

4 Materials Period: Mid May 2011 Area: Inside and Outside of FunkaBay Hokkaido Island Inside R/V: Ushio-maru & Kinsei-maru (only NORPAC net) Contents: Oceanographic observation by CTD - In fixed points & towed points by FMT net Funka Bay FMT3 FMT1 Outside Acoustic measurement by quantitative echosounder 38kHz, Simrad, in day and night - Assumed that all echo above 100m in depth are juvenile s Funamoto 2010 Lines & points by Ushio-maru Collecting juvenile samples in each water-mass by FMT net in day and Night above and below 33.0psu - TL mesurement & gastric contentsnalysis Collecting zooplankton samples by NORPAC net day above 33.0psu and all layer indicates NORPAC point by Kinsei-maru

5 SA effect SA effect Result Inside Outside Inside Outside Day SA effect Night Depth (m) Surface water of coastal Oyashio current Oyashio current Water Day: Cold Night: Warm *Generalized Additive Model plot

6 Result 40 Inside FMT3 p=0 p= Outside FMT1 p= n.s. n.s. p= Day Night Total length (mm) No data S. D. Mean S-CO 1 OW 2 S-CO 3 OW 4 S-CO 1 OW 2 S-CO 3 OW 4 n=237 n=189 n=340 0 n=77 n=55 n=226 n=132 0 *P value: Tukey-Crammer multiple comparison

7 Result Day A) Day-time Inside FMT3 Mean Sv (db) S-CO Day A) Day-time Surface Outside FMT1 Mean Sv (db) OW Juvenile aggrega5on Night B) Night-time 100m Sea bottom Sea bolom Night B) Night-time 100m 100m m 100m -70 Sv (db) OW: Thin OW: Thick

8 Percentage Small (<30mm) Large (<30mm) Day Night Day Night day night day night Result Composition of individual number Small copepods (<0.5mm in Body width) Large copepods (>0.5mm in Body width) Fish egg ( mm in diameter) Euphausiids Food size: Large juv. > Small juv. Night > Day %(GCW/BW) 6% 4% 2% Inside of FB Outside of FB Day Night Day Night S-CO OW S-CO OW S-CO OW S-CO OW No Data!" #" $" %" &" '" (" )" *"!+"!!"!#"!$"!%"!&"!'" S L S L S L S L S L S L S L S L n=5 n=5 n=5 n=5 n=5 n=5 n=5 n=3 n=5 n=2 n=5 n=5 n=5 n=5 Inside: OW>S-CO & Night>Day Outside: S-CO OW & Day Night *GCW: gastric contents weight, BW: body weight, S: small juvenile, and L: large juvenile

9 Percentage Inside St Psudocalanus 2 Eucalanus Neocalanus Psudocalanus 2 Eucalanus Neocalanus St.32 All S-CO All S-CO Outside St.6 St.15 Psudocalanus Eucalanus Neocalanus Neocalanus spp. Eucalanus spp. Psudocalanus spp. Other copepods Amphipods Euphausiids Others Psudocalanus 2 Eucalanus Neocalanus All S-CO All S-CO All S-CO St.12 Result & Discussion Composition of WW S-CO shallower than depth of 33.0psu All from bottom to sea surface Psudocalanus Eucalanus Neocalanus In OW, large juv. could feed large planktons - E. bungii do not performs the significant DVM (Schabetsberger et al. 2000) Outside of FB, juv. could feed small foods in both water-mass - Psudocalanus spp. matches chl. a maximum layer (Yamaguchi 1999)

10 Discussion Inside of FB Outside of FB Day Night Day Night S- CO Warm OW Cold Day: Low metabolism in cold water Fish aggregation for low prey Day: Fish aggregation in mid-water Small copepods were fed Night: Feeding in warm, bright water Night: Feeding in warm, bright water Large one escape from predator Large one descend for large food

11 Discussion In the present study, Inside of FB: Large Juveniles Outside of FB: Small juveniles Spawning area In winter, Inside of FB: Warm High growth Outside of FB: Cold Low growth If pollock can be carried into FB, the growth and survival will be good (Nakatani and Maeda 1988) Juveniles outside of FB may not grow and survive well - In late May or June, Psudocalanus spp. reduces in FB (Nakatani and Maeda 1987)

12 Discussion Smaller Percentage Small Zoop. Pollock Juv. Large Zoop. Pollock Juv. Large fish Year Larger bigger is better (Modified from Coyle et al. 2011) Recruitment biomass (billon ind.) Large juv. fed large zoop. more than small one If juvenile feeds large foods, prey by predator in next life-stage may be fewer (coyle et al. 2011) But -In 00 s, large copepods have incrased (Tadokoro 2012) In 2011, the ratio of large juv. was fewer than recent other years They might not feed large foods well - They could not survive well in after life-stage? As the future works, Interannual difference of survival will be estimated by analyzing each nutri5onal status

13 Acknowledgements Many thanks for Prof. M. Ohara, Dr. O. Shida, Cap. Y. Kamei & Crews of R/V Ushio-maru, Crews of R/V Kinsei-maru, Dr. Y. Ito, Dr. J.Yamamoto, Mr. S. Fukui, Mr. T. Iwamori, Dr. H. Miyake, Mr. H. Okumura, Dr. T. Funamoto, Dr. Y. Mitani Dr. H. Takahara, and all members of LAMECA, Hokkaido University This study was conducted by: Financial support by Fisheries Agency of Japan Grant-in-Aid for Japan Society for the Promotion of Science (JSPS) Fellows