Diel-depth distributions of fish larvae off the Balearic Islands (western Mediterranean) under two environmental scenarios

M P Olivar1 A Sabatés1 F Alemany2 R Balbín2 and A Pérez2M. P. Olivar , A. Sabatés , F. Alemany , R. Balbín and A. Pérez

1 Institut de Ciències del Mar (CSIC), Passeig Marítim 37-49, 08003 Barcelona, Spain.

2 Centre Oceanogràfic de Balears Instituto Español de Oceanografía IEO Palma de Mallorca Spain2 Centre Oceanogràfic de Balears. Instituto Español de Oceanografía, IEO. Palma de Mallorca, Spain.

OUTLINE

Introduction on ichthyoplanktonIntroduction on ichthyoplankton

Objectives

Material and Methods

General hydrographic featuresy g p

Results:

Comparisons of integrated abundanceComparisons of integrated abundance

Larval assemblages

Vertical patterns (day-night and size stratification)

Conclusions

INTRODUCTION: Life cycle of fishes

LARVAE

Meso & macrozooplankton 0-200 mp

TRANSFORMING

ADULT

JUVENILE

RECLUTAMIENT PROCESS (Houde 1987)

OBJECTIVES

Objective

Analyse the effect of seasonal variability on the early developmentalAnalyse the effect of seasonal variability on the early developmental stages of fishes that live and reproduce on the shelf and slope off the Balearic region

Determine the diel-depth vertical distribution of the different species in relation to the environmental situation

OCEANOGRAPHIC STUDY REGION

MATERIAL AND METHODS

OCEANOGRAPHIC CRUISES

STUDY REGION

December 2009 July 2010

L b SAMPLING

Environment

Lab. Fish larvae

CTDStratified collectionStratified collection

HYDROGRAPHY: Vertical structure

December 2009December 2009

July 2010

HYDROGRAPHY: Integrated fluorescence

December 2009 July 2010y

0

25

0 0.2 0.4 0.6 0.8 1 1.2

Fluorescence

(m)

0

25

50

0 0.2 0.4 0.6 0.8 1 1.2

Fluorescence

(m)

50

75

100

Dep

th (50

75

100

Dep

th

MATERIAL AND METHODSDecember July

°N

39.8

1 21000 m

200 m

Mallorca Island

39.3

0.25 m21 m2

800 mCabrera

MultinetDecember 2009

. CTD

°E1.8 2.3 2.8 3.338.8

MocnessJuly 2010

Fixed stations 24-48

RESULTS: INTEGRATED DATA. DIFFERENCES AMONG ZONES

39 species1.6December 2009

3.5December 2009 39 species

1.2

1.4

N. S

pp

December 2009

2.5

3.0

abun

danc

e

December 2009

Autumn

CShelf Slope0.8

1.0

log

CShelf Slope1.5

2.0lg to

tal

60 speciesSummer

C S

Shelf SlopeBathymetric strata

C S

Shelf SlopeBathymetric strata

1 4

1.5

1.6July 2010

3 0

3.2

3.4

ance

July 2010

1.1

1.2

1.3

1.4

log

N. S

pp

2 2

2.4

2.6

2.8

3.0

log

tota

l abu

nda

C S

Shelf SlopeBathymetric strata

0.9

1.0

C S

Shelf SlopeBathymetric strata

2.0

2.2l

Higher number of species in summerThe majority of the species were present both in the Cabrera and Sóller zonesDominance of mesopelagic larvae both at shelf and slopep g p

RESULTS: GROUPS OF SAMPLESDecember 2009

Hlvl2D Stress: 0.14 range mHlvlSURTbTbDL

g0-6060-90

90-100-120100-120-300

>300

no significant differences by zone orbathymetric strata

July 2010lvlHid

SUR

2D Stress: 0.16

SURTbTbDL

i ifi t diff i l tirange m

significant differences in relation to the level of the water column

i ifi t d i ht diff

0-2525-5050-100100-300

>300significant day-night differences

High overlapping among surface and thermocline samples

RESULTS: GROUPS OF SPECIES TRANSFORMING AND JUVENILES

0-150 -100 -50 0 50

N/1000 m3

0-400 -200 0 200

N/1000 m3

0

100

200

0

100

200200

300

400pth

(m)

200

300

400pth

(m)

500

600

Dep

500

600

Dep

700

800

Cyclothone braueriDecember Slope

700

800

Cyclothone braueriJuly Slope

e.g., T & J C. braueri

RESULTS: GROUPS OF SPECIES *DEEP LARVAE

0-8 -4 0 4 8

N/1000 m3

0-8 -4 0 4 8 12

N/1000 m3

0

100

200

0

100

200200

300

400pth

(m)

200

300

400pth

(m)

500

600

Dep

500

600

Dep

700

800

Argyropelecus hemigymnusDecember Slope 700

800

Argyropelecus hemigymnusJuly Slope

FlexionPreflexion

PostflexionTransforming

RESULTS: GROUPS OF SPECIES *SUR & T DECEMBER 2009

B. glaciale C. maderensis C. braueri H. benoitiB. glacialeB. glaciale

105

75

45

15

105

75

45

15

105

75

45

15

105

75

45

15

105

75

45

15

105

75

45

15

4 2 0 2 4 6 8

155

25 20 15 10 5 0 5

155

150 100 50 0 50 100

155

60 40 20 0 20

155

15

H. hygomii

15

L. crocodilus

15

L. pusillus

15

L. dofleini

4 2 0 2 4 6 8

155

4 2 0 2 4 6 8

155

155

105

75

45

155

105

75

45

155

105

75

45

155

105

75

45

60 40 20 0 20 15 10 5 0 5 10 15 100 50 0 50 40 30 20 10 0 10

45

15

S. veranyi

45

15

V. attenuata

45

15

S. pilchardus

45

15

Lestidiops sp.

20 15 10 5 0 5 10

155

105

75

30 20 10 0 10

155

105

75

60 40 20 0 20 40

155

105

75

15 10 5 0 5 10

155

105

75

*Distribution in the *upper mixed layer and thermocline. Higher concentration at the gradient zone at night. Vertical sinking and retention at the thermocline Shallower distribution during the day. Higher light intensity. Higher food availability?

*

RESULTS: GROUPS OF SPECIES SURFACE JULY 2010

0-25

Arnoglossus

0-25

A. rocheiA. rochei

0-25

E. encrasicolus

0-25

T. draco

151-200

126-150

101-125

76-10051-75

26-50

151-200

126-150

101-125

76-10051-75

26-50

151-200

126-150

101-125

76-10051-75

26-50

151-200

126-150

101-125

76-10051-75

26-50

40 30 20 10 0 10 20 30 20 10 0 10 20 30 20 10 0 10 20 15 10 5 0 5 10

51-75

26-50

0-25

T. thynnus

51-75

26-50

0-25

T. mediterraneus

76 10051-75

26-50

0-25

C. julis

51-75

26-50

0-25

S. hepatus

20 15 10 5 0 5 10

151-200

126-150

101-125

76-100

4 2 0 2 4

151-200

126-150

101-125

76-100

20 10 0 10

151-200

126-150

101-125

76-100

C. pygmea D. holti

4 2 0 2 4

151-200

126-150

101-125

76-100

126-150

101-125

76-10051-75

26-50

0-25

pyg

126-150

101-125

76-10051-75

26-50

0-25

D. holti

SUR

50 40 30 20 10 0 10

151-200

4 2 0 2 4

151-200

6 50

Larvae restricted to the surface both day and nightLarvae restricted to the surface both day and nightMostly shelf dwelling species

RESULTS: GROUPS OF SPECIES JULY 2010

0-25

C. maderensis

0-25

C. braueri

0-25

H. benoiti

0-25

L. dofleini

SURFACE & THERMOCLINE

151-200

126-150

101-125

76-10051-75

26-50

151-200

126-150

101-125

76-10051-75

26-50

151-200

126-150

101-125

76-10051-75

26-50

151-200

126-150

101-125

76-10051-75

26-50

*800 600 400 200 0 200 400 600 400 200 0 200 400 1000 500 0 500 1000 10 5 0 5 10

51-75

26-50

0-25

L. crocodilus

51-75

26-50

0-25

L. pusillus

51-75

26-50

0-25

S. veranyi

51-75

26-50

0-25

V. attenuataTHERMOCLINE

60 40 20 0 20 40

151-200

126-150

101-125

76-100

20 10 0 10 20 30

151-200

126-150

101-125

76-100

20 15 10 5 0 5

151-200

126-150

101-125

76-100

20 10 0 10

151-200

126-150

101-125

76-100

BELOW THERMOCLINE

101-125

76-10051-75

26-50

0-25

B. glaciale

101-125

76-10051-75

26-50

0-25

Lestidiops spp

101-125

76-10051-75

26-50

0-25

M. puctatum

101-125

76-10051-75

26-50

0-25

N. rissoiBELOW THERMOCLINE

150 100 50 0 50

151-200

126-150

100 50 0 50 100

151-200

126-150

40 30 20 10 0 10

151-200

126-150

0 5

15 10 5 0 5 10

151-200

126-150

No shallower concentration during daylight hours

RESULTS: LARVAL SIZE STRATIFICATION. MYCTOPHIDS

-30 -20 -10 0 10N/1000 m3

-400 -200 0 200 400N/1000 m3

0

50

)

0

50

)

100

150

Dep

th (m

)100

150

Dep

th (m

)

PreflexionFlexion

200

Hygophum benoitiDecember Shelf

Hygophum benoitiJuly Shelf

200

-20 -10 0 10N/1000 m3

Postflexion

0

50

20 10 0 10 Preflexion stages preference shallower layersPostflexion stages reached deeper layers

100

150

Dep

th (m

)

Flexion and postflexion stages migration to 150

200

Hygophum hygomiiDecember Shelf

p g gsurface during the day in December

-60 -40 -20 0 20N/1000 m3

-10 0 10N/1000 m3

RESULTS: LARVAL SIZE STRATIFICATION. MYCTOPHIDS

0

50

m)

0

50

m)

Postflex and flex migration to the surface during the day, particularly in December

100

150

Dep

th (m

Lampanyctus pusillus Lampanyctus pusillus

100

150

Dep

th (m

y p y

200

Lampanyctus pusillusDecember Shelf

Lampanyctus pusillusJuly Shelf

200

0-40 -20 0 20 40

N/1000 m3

50

(m)

Preflexion stages shallower distributionPostflexion stages wider nocturnal range

Lampanyctus crocodilusJ l Sh lf

100

150

Dep

th Postflexion stages wider nocturnal range

P fl i July Shelf200

Preflexion

PostflexionFlexion

CONCLUSIONS

Variation in specific composition among periods, mainly due to the shelf species.p p g p , y p

No differences between zones (same species, similar abundance)

Larval depth vertical ranges differed among species with vertical habitatpartitioning:

Deep species (100-300): A. hemigymnus

Below thermocline species (from lower thermocline 200 m): B glacialeBelow thermocline species (from lower thermocline - 200 m): B. glaciale

Thermocline species: H. benoiti

Surface species: C. maderensis and many of the shelf speciesp y p

Transforming and juveniles appeared below 300 m.

Differences in diel vertical distributions between periods are relate to the

water column structure

In summer the majority of species were concentrated in the first 50 m

of the water column (thermocline), both day and night.

In autumn larvae were also concentrated in the surface layers during

the day (upper mixed layer) but showed a deeper distribution at nightthe day (upper mixed layer), but showed a deeper distribution at night(thermocline layer).

CONCLUSIONS

Larval size stratification was evident. Younger stages occupy the upper layers,g g py pp y ,

day and night. Postflexion reached much deeper layers and performed

vertical displacement to surface, during the day.

The thermocline acts as a retention structure during the non active night

hours. While light is the trigger factor for day migration to the surface.

Up to the moment remains an open question whether this displacement isUp to the moment remains an open question whether this displacement is

related to a suitable light intensity for feeding, or to a higher availability of food.

Thank you!