Distribution S5 #2947 and prey composition of juvenile small epipelagic fishes and myctophids in the Kuroshio-Oyashio Transition Zone in spring, 2002-2004 Kaori Takagi1, Akihiko Yatsu2, Hiroshi Itoh3, Masatoshi Moku4, Ken Mori2 and Hiroshi Nishida1

1: National Research Institute of Fisheries Science, Japan 2: Hokkaido National Fisheries Research Institute, Japan 3: Suidosha Co. Ltd., Japan 4: National Fisheries University, Japan MyctophidsMyctophids’’ relationshipsrelationships withwith commercialcommercial epipelagicepipelagic speciesspecies Such as Japanese sardine (Sardinops melanostictus) Anchovy (Engraulis japonicus) Chub mackerel (Scomber japonicus) Focus on horizontal distributions and prey in the nighttime surface layer at the Kuroshio-Oyashio Transition Zone (KOTZ) Î the key area for recruitment of the Pacific stocks SardineSardine

modified from Stock Assessment Report (FRA,FAJ) Possible migration pattern of dominant myctophids in the KOTZ

After Sassa (2004) Research survey for juvenile small epipelagic fishes • Date : May-June, 2002-2004 • Area :143-160°E, 35-40°N • Gear : Mid-water trawl • Trawling depth : 0-27 m • Depth of cod-end : 14 m • Net length : 89 m • Mesh size of cod-end: 10 mm. • Night-time 30 min. tow at 3.5kt • Sampling points: 45-50 stations

T/S Hokuho-Maru UsingUsing MidMid--waterwater TrawlTrawl forfor Myctophids...Myctophids... Myctophids Anchovy larvae • It is not the best gear for sampling myctophids, though… • We can get both myctophids and small epipelagic fishes simultaneously.

Club-hook squid Juvenile jack mackerels

Juvenile Mackerels by sampling depth in the KOTZ during Ma towof smallpel Catch inweight per30-min epipelagics Small At night

Sardine

Anchovy

Mackerels

Black snake mackerel S. californiensis y 1995 (modified from Yatsu et al., 2005). et from Yatsu y 1995 (modified agic fishesand predomi C. warmingii

M. asperum

Notoscopelus spp. atmsplgcfishes nant mesopelagic Myctophids This study Myctophids were dominant next to anchovy (except 2004)

Sardine Anchovy 80 Mackerels Myctophids

) 60 Others w UE

/ to 40 g CP k ( 20

0 200220032004

CPUE of myctophids Mackerel spp. Sardine are 3.6, 3.9 and 2.0 kg / tow in ’02, ’03 and ’04, respectively. Mainly anchovy The Dominant myctophids 4 dominant species account for more than 80% of all the myctophids (19-29 species). Catch in weight (on board) Diaphus perspicillatus / gigas Myctophum 100 asperum 80

60 Symbolophorus californiensis

Ratio (%) 40 Ceratoscopelus warmingii 20 Transitional water species 0 Subtropical 2002 2003 2004 and Year tropical species Body length of myctophids (sorted on board)

3,000 1,000 N=4,453 2002 N=11,266 2002 0+ 1+ 1,500 500 SC 1+ 2+ MA 0 0 1,000 3,000 2003 N=15,744 2003 N=3,844 1,500 500 0 0 3,000 1,000 2004 N=3,668 2004 N=1,782 fish 1,500 500 0 0 3,000 2002 0+ 1+ N=8,281 1,000 2002 N=1,895 No. of 1,500 500 1+ 2+～ CW 0+ DP 0 0 3,000 1,000 2003 N=1,804 2003 N=13,799 1,500 500 0 0 3,000 1,000 2004 N=4,161 2004 N=579 1,500 500 0 0 5 50 100 150 5 50 100 150 Standard length (mm) Body length of small epipelagic fishes (sorted on board) 20 1,400 2002 N=28 2002 N=1,305 10 Sardine (0+) 700 Mackerels (0+) 0 0 1,400 20 2003 N=15 2003 N=3,531 10 700 0 0 20 2004 N=45 14,000 2004 N=31,926 7,000 fish 10 0 0 60,000 2002 N=83,281 10 50 100 150 200 250

No. of 30,000 Anchovy Fork length (mm) 0 (1+) 60,000 2003 N=92,410 30,000 0 60,000 2004 N=119,763 30,000 Anchovy 0+(mainly 20-60 mm), sardine 0 1+(120-150 mm), and mackerels 1+ (>200 10 50 100 150 200 250 mm) are not shown here due to Body length (mm) organizational problem of data. Horizontal distribution (in 03, for example)

0+ N N Sardine 0+ SCSC 1+ ° 40 ° 2+ 40 15 900 600 10 35 ° 300 35° 5

0+ CWCW Anchovy 1+ 40 ° 1+ 40° 20,000 800 400 10,000 5,000 35 ° 200 35°

MAMA 0+ Mackerels 0+ 40 ° 1+ 40° 3,000 400 1,500 200 500 35 ° 100 35° 140° 150° 160 °E DPDP ～1+ 40 ° 2+～

200 100 SST (℃) 35 ° 50 140 ° 150 ° 160 °E Small epipelagic fishes Myctophids Overlap index (Pianka,1973) Sardine Anchovy Chub mackerel Spotted mackerel 0+ SC 1+ SC 2+ SC CW 0+ CW 1+ 0+ MA 1+ MA DP 0+ DP 1+ DP 2+～ Sardine Anchovy 0.85 Chub mackerel 0.03 0.02 Spotted mackerel 0.02 0.04 0.76 pp SC 0+ ---- 2002 ∑ ikij SC 1+ 0.27 0.31 0.21 0.41 - O = SC 2+ 0.26 0.30 0.03 0.05 - 0.86 jk 2 2 pp CW 0+ 0.01 0.11 0.34 0.58 - 0.55 0.26 ij ∑∑ ik CW 1+ 0.03 0.06 0.10 0.15 - 0.30 0.34 0.28 MA 0+ 0.03 0.08 0.30 0.54 - 0.39 0.17 0.53 0.37 MA 1+ 0.11 0.11 0.27 0.44 - 0.50 0.24 0.51 0.13 0.76 DP 0+ 0.04 0.00 0.04 0.03 - 0.05 0.08 0.13 0.87 0.27 0.07 DP 1+ 0.02 0.04 0.48 0.83 - 0.39 0.06 0.62 0.13 0.65 0.66 0.08 p , p : the proportions of ith DP 2+～ 0.01 0.00 0.03 0.03 - 0.07 0.10 0.12 0.93 0.29 0.03 0.92 0.01 ij ik Sardine station occupied by the jth and Anchovy 0.30 Chub mackerel 0.00 0.02 the kth fishes, respectively. Spotted mackerel 0.00 0.02 0.76 SC 0+ ---- 2003 SC 1+ 0.10 0.45 0.09 0.08 - SC 2+ 0.04 0.62 0.01 0.01 - 0.60 CW 0+ 0.64 0.48 0.04 0.06 - 0.29 0.54 CW 1+ 0.51 0.40 0.18 0.20 - 0.28 0.46 0.86 MA 0+ 0.00 0.00 0.00 0.00 - 0.02 0.01 0.44 0.48 MA 1+ 0.00 0.51 0.00 0.06 - 0.49 0.81 0.63 0.55 0.08 0.9≦OI<1.0 DP ～1+ 0.00 0.01 0.32 0.52 - 0.24 0.03 0.32 0.40 0.63 0.15 DP 2+～ 0.01 0.17 0.00 0.04 - 0.24 0.36 0.10 0.34 0.00 0.16 0.00

Sardine 0.8≦OI<0.9 Anchovy 0.21 Chub mackerel 0.00 0.31 Spotted mackerel 0.01 0.30 0.98 2004 SC 0+ ---- 0.7≦OI<0.8 SC 1+ 0.00 0.43 0.00 0.00 - SC 2+ 0.00 0.45 0.00 0.00 - 0.96 CW 0+ 0.00 0.24 0.00 0.00 - 0.34 0.23 0.0≦OI<0.7 CW 1+ 0.00 0.17 0.00 0.00 - 0.43 0.24 0.69 MA 0+ 0.29 0.31 0.00 0.00 - 0.53 0.54 0.15 0.05 MA 1+ 0.07 0.23 0.22 0.21 - 0.00 0.00 0.05 0.01 0.08 DP ～1+ 0.00 0.00 0.00 0.00 - 0.01 0.00 0.05 0.03 0.00 0.32 DP 2+～ 0.00 0.10 0.00 0.00 - 0.01 0.01 0.46 0.00 0.00 0.00 0.00 Prey analysis SAMPLING • Two nights (11pm-3am) in May 2002 at 4 stations ( ) • Midwater trawl for fishes: towed at 0-80 m (mainly 0-27 m) depth • NORPAC net for macro-zooplankton: mesh size 335 μm, from 150 m or 40 m depth to sea surface N 40° 4 Stations: sardine, anchovy, mackerels, and myctophids were caught together. 35° 15ºC 140° 160°E HANDLING COPEPODS Stations and water temperature at 100 m depth Copepods in stomachs and NORPAC net samples were • identified for their species or genera. • counted. • measured for prosomal length. • estimated for dry weights from length-weight relationships (for copepods in stomachs). List of stomachs Number of fish (range of body length in mm) Epipelagic fishes, N=80 • Japanese sardine: 10 (34.5-52.6) • Anchovy: 40 (35.5-57.4) • Chub mackerel Scomber japonicus: 8 (47.4-137.6) • Spotted mackerel S. australasicus: 22 (49.5-151.1)

Juvenile (J) and adult (A) myctophids, N=270(J=99, A=171) • S. californiensis : J=0, A=32 (71.0-108.7) • C. warmingii : J=32 (22.1-66.1), A=38 (68.6-82.0) • M. asperum : J=7 (21.0-46.4), A=18 (56.9-75.6) • D. perspicillatus : J=29 (25.2-55.2), A=31 (74.3-146.9) • M. nitidulum : J=9 (19.1-43.2), A=40 (50.7-63.6) • Notoscopelus japonicus : J=11 (29.1-37.6), A=1 (92.8) • N. resplendens : J=11 (21.9-35.1), A=11 (64.9-78.4) Stomach contents of juvenile small epipelagic fishes

Paracalanus SardineSardine Fish egg parvus

0% 20% 40% 60% 80% 100% Oncaea venusta Oncaea scottodicarloi AnchovyAnchovy Corycaeus affinis Oncaea spp.

0% 20% 40% 60% 80% 100%

Calanoida Eucalanus spp. Chub mackerelChub mackerel (broken)

0% 20% 40% 60% 80% 100% Neocalanus cristatus Spotted Spotted mackerelmackerel

0% 20% 40% 60% 80% 100% 0 20 40 60 80 100 Number (%) ★Calanoida (broken) : 2-3 mm PL Neocalanus Prey items (only copepods) cristatus Co. affinis % WeightPa. (Copepods) parvus Calanoida Sardine Anchovy Eucalanus Chub Mackerel spp. Spotted Mackerel S. californiensis-Juv Pleuromamma C. warmingii-Juv piseki M. asperum-Juv D. perspicillatus-Juv M. nitidulum-Juv N.japonicus-Juv N. resplendens-Juv S. californiensis-Ad C. warmingii-Ad M. asperum-Ad D. perspicillatus-Ad M. nitidulum-Ad Metridia N. japonicus-Ad pacifica N. resplendens-Ad

Lucucita 0%Eucalanus 20% 40%Pleuromamma 60% 80% 100% fravicornis californicus xiphias Weight (%) Body size of copepods both stomach contents & NORPAC net Paracalanus parvus Epipelagic fishes Corycaeus affinis

Oncaea venusta Mackerels > 120 mm FL

O. scottodicarloi Neocalanus cristatus*

Eucalanus californicus

Rhincalanus nasutus Myctophids < 130 mm SL Lucucita flavicornis

Pleuromamma piseki

Metridia pacifica

Euchirella rostrata

Pl. xiphias*

0369 Prosomal length (mm) * Not caught by NORPAC net here. Density of the copepods

Depth C. affinis Pa. parvus 0-40 m

Euc. californicus

Pl. piseki 0-150 m M. pacifica L. flavicornis

0 200 400 Density ( ind. / m-3)

N. cristatus and Pl. xiphias were not caught by NORPAC net here. Sea surface Small copepods Eucalanus 40 m californicus

Large copepods

(except E. californicus)

150 m

Vertical migration Non -vertical migration (Subsurface DailySeasonal* - intermediate)

Oyashio M. pacifica N. cristatus

Euc. Kuroshio Pl. xiphias californicus L. flavicornis

Pl. piseki (* surface-intermediate layer in spring ) Summary In the nighttime surface layer of the KOTZ (in spring) X Abundance of myctophids: change considerably X Composition of the dominant myctophids: stable S. californiensis C. warmingii M. asperum D. perspicillatus / gigas X Horizontal distribution of the dominant myctophids: wide regardless of their abundance different from that of juvenile small epipelagic fishes X Prey copepods of the dominant myctophids: large copepods in deeper than 40m depth, while small epipelagic fishes prey upon small copepods in shallower than 40m depth Conclusion These results suggest occurrences of resource partitioning between juvenile small epipelagic fishes and the dominant myctophids in terms of habitat and prey. Acknowledgements

• We thank the captain and crew of the T/S Hokuho-maru (the Hokkaido Board of Education Management for Training Ships) for assistance while sampling onboard. We also thank staffs of NRIFS and Suidosha Co., who helped us sorting and measuring fishes and planktons at labs. • This study was supported by grants from the Fisheries Agency of Japan and the Ministry of Agriculture, Forestry and Fisheries of Japan under the Deep-sea Ecosystem and Exploitation Programme (DEEP).

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