A biophysical model to study the dynamics of sardine and anchovy ichthyoplankton in the

Canary Upwelling System

II. Continent-archipelago interactionsTimothée Brochier, Eurocean PhD student, IRD

Azeddine Ramzi INRH, MoroccoChristophe Lett IRD, FranceEric Machu IRD - INRH, MoroccoSantiago Hernández-León ULPGC, SpainPierre Fréon IRD, France

Modelling the biophysical dynamics of sardine and

anchovy ichthyoplankton in the Canary Upwelling

System: continent-archipelago interactions

Summary

1. Issues:a. Filament-eddy systemb. Spawning patterns (anchovy and sardine)c. Larval presence in Canary area

II. Method:a. Hypotheses to testb. Modelling toolsc. Simulation design

III.Results and discussion

Filament-eddy system

•Connecting the coastal upwelling area with the archipelago and its associated eddy field

•Near-surface structures, ~10 km wide, up to several hundred km long

•Filament + associated eddy = favourable fundamental triad for a reproductive habitat (Bakun, 1996). --> cyclonic eddies may provide nursery grounds for neritic fish

Major filaments Adapted from Pelegri et al. 2004, image from Javier Aristegui

Eddy

fiel

d

Spawning patterns(Sardine and anchovy)

Sard

ine

Anchovy

Sardin

eAnchovy

Winter

6

5

4

3

2

1

6

5

4

3

2

1

0 225 450 675 900

Anchovy Sardine

Coa

stal

Are

aC

oast

al A

rea

Summer(eggs.m-3)

Winter(eggs.m-3)

•Upwelling Seasonality: maximum in summer, almost permanent south of Cap Juby

•Anchovy spawn mainly north of Cap Juby in summer and in the central area in winter

• Sardine spawn mainly south of Cap Juby in summer, and both north and south in winter

• Data from INRH cruise surveys from 1994 to 1999

Berraho Amina, 2007. Relations spatialisées entre milieu et ichtyoplancton des petits pélagiques de la côte Atlantique marocaine (Zones centrale et sud). Thèse de Doctorat, Univ. Mohamed V, Rabat, 261p.

Summer

Larval presence near Canary archipelago

Anchovy larvae more frequent, not associated with filaments(Becognée et al. 2006)

Sardine larvae associated with filaments(Rodriguez et al., 1999; Becognée et al. 2006)

No anchovy nor sardine eggs off the African shelf(Rodriguez et. al, 2006)

Larval presence is associated with lunar cycle(Becognée et al. 2006)

Similar vertical distribution, mainly in the upper 100m(Rodriguez et. al, 2006)

Fig. 5 Mean vertical concentrations of a mesozooplankton, b totalfish larvae, c larval taxonomic diversity, d Engraulis encrasicoluslarvae, e E. encrasiclous eggs, f Sardina pilchardus larvae, g Anthiasanthias larvae, h Cyclothone braueri larvae, i Ceratoscopelusmaderensis larvae, j Notolichnus valdiviae larvae, k Diogenichthys

atlanticus larvae and l Myctophum punctatum larvae (horizontallines indicate positive values of standard error). The mean verticalprofile of temperatures recorded at the ichthyoplankton stations isoverlapped to the vertical distributions of mesozooplankton andfish larvae

891

Mean vertical concentrations of Engraulis encrasicolus larvae (Rodrıguez et al, 2006)

Hypotheses to test1. Ichthyoplankton transport to Canary islands is

associated with filaments of upwelled waters

2. Ichthyoplankton transport to Canary island coasts is more frequent from anchovy spawning areas than sardine spawning areas

3. Vertical migration of larvae impact their transport in filaments

Modelling tools

• The hydrodynamic field is reproduced by a numerical model (ROMS)

• Eggs and larvae are released along Moroccan coast as Lagrangian particles at regular dates and places using an IBM (Ichthyop)

We used a coupled IBM-hydrodynamic model:

30 daysInitial release 15 days

ROMSSST

http://www.eco-up.ird.fr/projects/ichthyop/

Ichthyop: A Lagrangian tool for modelling

ichthyoplankton dynamics

Download page:

Simulation design

• Simu 1: passive tracers• 3 release depth levels (0-33m, 33-66m,

66-100m)

• 3 repeats

• Simu 2: active individuals• 3 egg densities (1.021, 1.023, 1.025)

• 4 vertical migration schemes (15m, 50m, 100m, 20-50m)

Transport Duration = Larval stage duration: about 1 month for anchovy and sardine

Transport success = being transported to one of the following areas: eastern islands, eastern eddy field, western islands, western eddy field

• 5000 particles released every month• 6 areas of release (along the African shelf)• 3 years of release

Release and Recruitment areas

Result - Simu 1: passive tracers

- Maximum transport to Canary area:- from areas 3, 4 and 5- for release near surface (0-33m)- during summer (July-August)

- No variation between repeats

Results consistent with field observations of filaments and with the upwelling index

A- Transport from the upwelling area to the entire Canary area:

1_nord 2 3 4 5 6_sud

Release area

Tran

spor

t suc

cess

(%)

02

46

810

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Release month

Tran

spor

t suc

cess

(%)

02

46

810

97 98 99

Release year

Tran

spor

t suc

cess

(%)

02

46

810

−0.0 to −66.0 −33.0 to −66.0 −66.0 to −66.0

Release depth (m)

Tran

spor

t suc

cess

(%)

02

46

810

0 1 2

Replicate

Tran

spor

t suc

cess

(%)

02

46

810

05

1015

20

Release month

Tran

spor

t suc

cess

(%)

01 02 03 04 05 06 07 08 09 10 11 12

dataset$ReleaseArea123456

02

46

810

Release depth (m)

Tran

spor

t suc

cess

(%)

−0.0 to −66.0 −33.0 to −66.0 −66.0 to −66.0

dataset$ReleaseArea123456

24

68

10

Release month

Tran

spor

t suc

cess

(%)

01 02 03 04 05 06 07 08 09 10 11 12

dataset$Year979899

Release area

1 2 3 4 5 6North South

Month of releaseJan Mar May Jul Sep Nov

depth0-33m 33-66m 66-100m 0 21

repeat

Tran

spor

t su

cces

s (%

)

12

34

56 Release

areas

10 10

1010

40

60

80

100

120

140

160

180

2 4 6 8 10 12

Upwelling index

Result - Simu 1: passive tracers

- Western archipelago: - No transport to the western islands (zone 1)- Some transport to the western area (zone 3) from the southern release areas

- Eastern archipelago: - Transport to the eastern islands (zone 2) max in March-April, coming from northern release areas - Transport to the eastern area (zone 4) is max in summer, from the southern areas

B- Transport from the upwelling area to the specific Canary area:

Transport to Recruitment area (max 8%)

Month of maximum transport(3-4; 7-8)

I 2

3 4

(5-6-7)

(3-4; 7-8)

(1; 7-8)

Recruitment area

Release area(shelf)

Result - Simu 2: Active individuals

More transport to Canary area when larvae remain in the upper layer

More transport to Canary area for higher egg density

Time since spawning

spawn

3 days 10 days

eggs(buoyant)

yolk sac larvae (passive)

Active larvae(vertical migration)

Impact on the transport to Canary area:1_nord 2 3 4 5 6_sud

Release area

Tran

spor

t suc

cess

(%)

01

23

45

Jan Mar May Jul Sep Nov

Release month

Tran

spor

t suc

cess

(%)

01

23

45

97 98 99

Release year

Tran

spor

t suc

cess

(%)

01

23

45

1.021 1.023 1.025

Egg dentity

Tran

spor

t suc

cess

(%)

01

23

45

1 2 3 4

Target depth (m)

Tran

spor

t suc

cess

(%)

01

23

45

1.5

2.0

2.5

3.0

3.5

4.0

target_depth

Tran

spor

t suc

cess

(%)

1 2 3 4

dataset$Year

97

98

99

02

46

Release depth (m)

Tran

spor

t suc

cess

(%)

1 2 3 4

dataset$ReleaseArea

1

2

3

4

5

6

02

46

8

Release month

Tran

spor

t suc

cess

(%)

01 02 03 04 05 06 07 08 09 10 11 12

dataset$target_depth

1

2

3

4

Egg density

1.021 1.023 1.025

Tran

spor

t su

cces

s (%

)

1_nord 2 3 4 5 6_sud

Release area

Tra

nsport

success (

%)

02

46

810

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Release month

Tra

nsport

success (

%)

02

46

810

97 98 99

Release year

Tra

nsport

success (

%)

02

46

810

1.021 1.023 1.025

Egg dentity

Tra

nsport

success (

%)

02

46

810

!100.0 to !100.0 !15.0 to !15.0 !20.0 to !50.0 !50.0 to !50.0

Target depth (m)

Tra

nsport

success (

%)

02

46

810

100m

1_nord 2 3 4 5 6_sud

Release area

Tra

nsport

success (

%)

02

46

810

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Release month

Tra

nsport

success (

%)

02

46

810

97 98 99

Release year

Tra

nsport

success (

%)

02

46

810

1.021 1.023 1.025

Egg dentity

Tra

nsport

success (

%)

02

46

810

!100.0 to !100.0 !15.0 to !15.0 !20.0 to !50.0 !50.0 to !50.0

Target depth (m)

Tra

nsport

success (

%)

02

46

810

50m 20-50m

1_nord 2 3 4 5 6_sud

Release area

Tra

nsport

success (

%)

02

46

810

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Release month

Tra

nsport

success (

%)

02

46

810

97 98 99

Release year

Tra

nsport

success (

%)

02

46

810

1.021 1.023 1.025

Egg dentity

Tra

nsport

success (

%)

02

46

810

!100.0 to !100.0 !15.0 to !15.0 !20.0 to !50.0 !50.0 to !50.0

Target depth (m)

Tra

nsport

success (

%)

02

46

810

15m

Tran

spor

t su

cces

s (%

)

Vertical migration

100m 50m 20-50m 15m

Target depth

Simplified larval development model:

Conclusions• The results comfort our hypotheses:

• The transport patterns correspond to filament characteristics (seasonality, location and depth structure)

• The sardine spawning area is exposed to transport toward the eddy field south of the islands (~8%), but rarely to the islands (<1%)

• At the opposite, the anchovy spawning area is subject to transport towards the eastern islands (~6%), but less to the southern eddy field (~4%)

• No ichthyoplankton transport to the western islands

• Larval vertical migration can double the transport to the Canary area, from 2% (100m) to 4% (15m)

Questions?