akihiko yatsu, masatoshi moku, hiroshi nishida, kaori takagi, norio yamashita and hiroshi itoh

Possible Ecological Interactions between Small-pelagic and Mesopelagic Fishes in the Kuroshio-Oyashio Transition Zone and Kuroshio

Extension in Spring

Akihiko Yatsu, Masatoshi Moku,

Hiroshi Nishida, Kaori Takagi,

Norio Yamashita and Hiroshi Itoh

Horizontal DistributionVertical DistributionStomach Contents

Survey Area (Spring)

Lantern Fish Migration: Myctophum asperum (left) and Symbolophorus californiensis (right)

After Sassa (2001)

Backgrounds and Purpose Kuroshio-Oyashio Transition Zone (KOTZ) and Kuroshio Extension (KE) are the key areas for recruitment of sardine, anchovy, and mackerel

Mortality of anchovy larvae in KOTZ-KE is mainly caused by predation by black snake mackerel (Nealotus tripes).

Biological interactions between juvenile small pelagics and myctophids may be possible because 1) myctophids are abundant in KOTZ and 2) both are zooplankton feeder

Seek for possible interaction between small pelagics and micronectonic mesopelagic fishes in KOTZ

Day Night

Small pelagics

Meso-pelagics

?

Surface Trawl Survey in Kuroshio/OyashioTransition Zone in Spring since 1996

Net opening diam.: 27m

Towing at: 3.5 knots at night

Typical towing depth: 0-30m

Tansyu Maru (499GT, 1800HP): -1999 Hokuho Maru 　 (664 GT, 2200HP ） 2000-

CPUE (kg / 30 min tow) of Japanese Sardine and SST

2004

2001

2000

1996

1997

1998

1999

2002

2003

1000m and 3000m isobath

Emperor Sea Mt.

Survey Index of and Estimated Recruit No.

0

2

4

6

8

10

12

1996 1998 2000 2002 2004

Rec

ruitm

ent

(bill

ion)

050100150200250300350400450

Abu

ndan

ce in

dexRecruit

Index

0

5

10

15

20

25

30

35

40

45

1996 1998 2000 2002 2004

Rec

ruits

(10̂

5)

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

Sur

vey

inde

x

RecruitIndex

Chubmackerel

Sardine

Fairly good relation indicate early survival is mainly determined after the feeding larvae distributing in Kuroshio and KOTZ

1.E+071.E+081.E+091.E+101.E+111.E+121.E+131.E+141.E+151.E+16

78 80 82 84 86 88 90

Year class

Pop

ulat

ion

num

bers

Egg

Yolk- saclarvae

Feedinglarvae

Recruit

Sardine (Watanabe et al., 1995)

CPUE kg/ 30min

0 10 20 30 40

Anchovy adult

Miscellaneous

Myctophids (juv.+ad.)

Sharks

Anchovy larvae

Neon flying squid

Club-hook squid

Common squid

Spotted mackerel ad.

Mackerel larvae

Sardine

Chub mackerel ad.

Catch WeightComposition in 2002

(0-30m depth)

Club-hook squid

Enoploteuthidae

Anchovy larvae 　 Myctophids

Scomber juv. Jack juv.

2002Symbolophoruscaliforniensis

Ceratoscopeluswarmingii

Myctophumasperum

Diaphusperspicillatus

others

2003

Symbolophoruscaliforniensis

Ceratoscopeluswarmingii

Myctophumasperum

Diaphusperspicillatus

others

Adult Myctophid Biomass Composition in 2002 and 2003 (0-30m depth)

CPUE (kg / 30 min tow) of Small Pelagic Fishes and Myctophids (juv+ad) in 2000

Sardine

juv

Scomber spp. juv

Anchovy

larvae

Symbolophorus californiensis

Ceratoscopelus warmingii

Myctophum asperum

Diaphus perspicillatus


SST

Anchovy.

050

100150200250

0 25 50 75 100 125 150

Body length (mm)

0

1000

2000

3000

0 20 40 60 80 100 120 140

0

1000

2000

3000

0 20 40 60 80 100 120 140

0200400600800

1000

0 20 40 60 80 100 120 140

0100200300400500

0 20 40 60 80 100 120 140

0+

1+ 2+～

2+

0+ 1+

0+ 1+

1+ S. californiensisN = 11,266

C. warmingiiN = 8,281

M. asperumN = 4,453

D. perspicillatusN = 1,895

Scomber spp.

0102030405060

0 25 50 75 100 125 150

Fork length (mm)

J apanese sardine

0

2

4

6

8

0 25 50 75 100 125 150

Fork length (juv.) or Body length (ad.) (mm)

Size Composition ofSmall Pelagic Fishes and Myctophids in 2002

Juv. Sardine ad.

Scomber spp. Juv.

Larvae+Juv. (black) and adults (blue)


Ceratoscopelus

warmingii

Myctophum asperum


Standard length (mm)

Anchovy

Nighttime Vertical Distribution of Small Pelagics, Myctophids and Black Snake Mackerel in May 1995 at 37N 147E

Black Snake Mackerel Nealotus tripes as a Predator

Fi (%)

-60

-40

-20

0

20

40

60W

i (%)

Ci (

%) Unidentified fishes(1,699)

Euphausiids(2,399)

Myctophids(1,767)

Miscellaneous(702)

Anchovy larvae(543)

Squids(390)

Scomber(3)

150-220mm SL N=270

50 250100 150 20020

40

60

Fi %（）

-60

-40

-20

0

20

40

60

Wi (

%)

C

i (%)

Unidentifiedfishes(1,862)

Euphausiids(1,826) Myctophids

(164)

Miscellaneous(1,009)

Anchovy larvae(163)

Squids(209)

Scomber(54)

70 - 149 mm SL N = 223

20

40

60

20 40 60 80 100 120 140 160

Index of Relative

Importance of Diets of

Black Snake

Mackerel in May 2002

Larvae BSM selectively feeds on anchovy larvae (Kubota ,2003)

Subadults

Adults

Freq

% in Weight

% in No.

Prey Composition of Juvenile Small Pelagic Fishes and Myctophids (Adults & Juveniles) in May 2002

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

Myctophum asperum J uv.

Myctophum asperum Ad.

Myctophum nitidulum

Diaphus perspicillatus J uv.

Diaphus perspicillatus Ad.


Notoscopelus resplendens

Notoscopelus japonicus

Ceratoscopelus warmingii J uv.

Ceratoscopelus warmingii Ad.

Anchovy

Sardine

Spotted mackerel

Chub mackerel

Composition by number

EuphausiidsNeocalanusEucalanusMetridiaPleuromammaParacalanus CorycaeusOncaeaCALANOIDA (broken)Other COPEPODASalpsOikopleuraOikopleura houseGelatinousEggs of InvertebratesFishesMiscellaneous

Stomach Contents of Sardine and Prey Availability in Kuroshio Extension during 1997-1998 (Saito et al., 2001)

Small copepods (<0.8mm BL, Paracaranus etc.) are abundant

Large copepods (Calanus pacificus etc.) was less abundant

Optimum prey size for juvenile sardine (25-40mm BL) is 0.8-1.2mm

Juvenile sardine (>33 mm BL) selectively fed on large copepods

Larval sardine (26-31 mm BL) preyed upon small copepods

Juveniles of both myctophids and small pelagics fed on 0.6-0.9 mm BL Paracalanus in KOTZ (our results)

Size of prey (μm)

Prey density (ind m-3)

Summary Juvenile small pelagics and myctophids (ad.+juv.) horizon

tally overlap in surface waters (0-30m) of KOTZ in spring Black snake mackerel shift their diet from anchovy larvae,

to krill and myctophids with ontogenetic descent Corycaeus and Oncea (epipelagic) were preyed by juvenil

es of small pelagics and some juvenile myctophids Krill, Pleuromamma and Metridia (deil vertical migrants wi

th photophores) were exclusively consumed by myctophids

Possible competition for large copepods Further studies are needed for 1) competition with juvenile myctophids for epipelagic ZP,

2) indirect effects of black snake mackerel, 3) quantitative evaluation

SpawningStock Biomass

and Recruitment

of Sardine

and Chub mackerel

R per SSB =f (SSB, SST

in key areas) but imperfect

050,000

100,000150,000200,000250,000300,000350,000

0 5,000 10,000 15,000SSB (1000t)

Rec

ruitm

ent

(mill

ion) 80

86

77

88

Sardine

0

5,000

10,000

15,000

20,000

25,000

0 1,000 2,000 3,000 4,000SSB (1000t)

Rec

ruitm

ent

(millio

n)

64

67

71

79

63

77

85

69

66

Chub mackerel

Myctophids: Diel Vertical Migration and Feedingin Oyashio Area (Moku et al., 2000)

Prey Composition of Juvenile Small Pelagic Fishes and Myctophids (ad.+juv.) in May 2002

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

Myctophum asperum

Myctophum nitidulum



Notoscopelus resplendens

Notoscopelus japonicus


Anchovy

Sardine

Spotted mackerel

Chub mackerel

Composition by number

EuphausiidsNeocalanusEucalanusMetridiaPleuromammaParacalanus CorycaeusOncaeaCALANOIDA (broken)Other COPEPODASalpsOikopleuraOikopleura houseGelatinousEggs of InvertebratesFishesMiscellaneous

CPUE (catch weight per a tow) of Small Pelagic Fishes and Myctophids (juv+ad) in 1999

Sardine

Juv.

Scomber spp. Juv.

Anchovy

larvae



Myctophum asperum



SST

akihiko yatsu, masatoshi moku, hiroshi nishida, kaori takagi, norio yamashita and hiroshi itoh

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