Assessing the potential role of predation by jumbo squid and fishing on small-pelagics (common sardine and

anchovy) and demersal (hake) stocks in central Chile, 33° S - 30° S

Hugo Arancibia1 and Sergio Neira2

1: Departamento de Oceanografía, Universidad de Concepcion, Chile2: Zoology Department , University of Cape Town , South Africa

Hawaii, November 2006

IRD supports the Ph. D. of Sergio Neira at the University of Cape Town, South Africa.

INCOFISH Consortium is a EU Project about “Integrating multipledemands on coastal zones with emphasis on aquatic ecosystems andfisheries”. Some results exhibited in this talk have been obtained fromthis project.

1. Introduction

• Since early 2000s, an unusually high presence of jumbo squid hasbeen detected off central Chile (33ºS-39ºS).

• This outbreak has been associated (by some stakeholders) to declines in small pelagic (common sardine, anchovy) and demersal fish (hake).

• In this study we present an analysis of the role of predation by jumbo squid, with emphasis on the potential impacts on pelagic and demersal fish stocks in central Chile.

75° 70°

31°

40°

E

L

I

H

C

32°

33°

34°

35°

36°

37°

38°

39°

71°72°73°74°

Concepción

Valparaiso

Valdivia

• Area:from 33°S to 39° S and from thecoast line up to 30 nm, with 50,000 km2

• Narrow continental shelf with stronglyseasonal upwellings

• High PP

• Main fishing grounds of fleets, e.g.: purse seiners and trawlers

• Globally significant landings:4.5 million tons in 1995, butdecreasing since then (1,2 milliontons )

0

1000

2000

3000

1990 1992 1994 1996 1998 2000 2002 2004

Biomass (hydroacoustic)Vulnerable biomass (SPA)Total biomass (SPA)

0.00

0.05

0.10

0.15

0.20

0.25

1990 1992 1994 1996 1998 2000 2002 20040

30

60

90

120

150F=Y/BLandings Landing (ton 10

3)

Years

Bio

mas

s (to

n 10

3 )Fi

shin

g m

orta

lity

(yea

r-1)

Chilean hake biomass (Source: Secretary of Fisheries, 2005)

Presence of jumbo squid

(% in hake surveys)La

ndin

g (to

n 10

3 )

0

30

60

90

120

150

1990 1992 1994 1996 1998 2000 2002 20040

20

40

60

80

100LandingsAbundance (relative)

Y e a r s

Jumbo squid (Secretary of Fisheries, 2005)

predation predation

Industrial Trawlers Small-scale jigging fleet Industrial and small-scalepurse-seiners

Biological (prey-predator) and technical (fleets) interactions

2. Methods

• In spite of biomass assessment for jumbo squid, we assumed an ecologically sound biomass level for jumbo squid based in predator requirements from a 31-group Ecopath model representing central Chile in year 2000.

• With this model we calculate the biomass of prey removed by jumbo squid per year.

• In addition, we simulate an increase in Bjumbo squid in one order of magnitude from year 2000 to 2005 using Ecosim.

• Then, we analyze the effects of this change in the biomass of hake and small-pelagic fish under mixed (v=2) and top-down (v=5) trophic controls (bottom-up control shown no changes).

Data requered by EcopathData Data requeredrequered by by EcopathEcopath

For each group, four variables are input data (green) and with thesofware we estimate the last one (red):

1) B, P/B, Q/B, EE, DCs, ...2) B, P/B, Q/B, EE, DCs, ...3) B, P/B, Q/B, EE, DCs, ...4) B, P/B, Q/B, EE, DCs, ...

P/B = Z, and Q/B > B > DCs >> EE

Generally, EE is output. EE is the proportion of production used in thesystem (predation + export)

ForFor eacheach groupgroup, , fourfour variables are variables are inputinput data (data (greengreen) ) andand withwith thethesofwaresofware wewe estimateestimate thethe lastlast oneone ((redred):):

1)1) B, P/B, Q/B, B, P/B, Q/B, EEEE, , DCsDCs, ..., ...2)2) B, P/B, B, P/B, Q/BQ/B, EE, , EE, DCsDCs, ..., ...3)3) B, B, P/BP/B, Q/B, EE, , Q/B, EE, DCsDCs, ..., ...4)4) BB, P/B, Q/B, EE, , P/B, Q/B, EE, DCsDCs, ..., ...

P/B = Z, P/B = Z, andand Q/B > B > Q/B > B > DCsDCs >> EE>> EE

GenerallyGenerally, EE , EE isis output. EE output. EE isis thethe proportionproportion ofof productionproduction usedused in in thethesystemsystem ((predationpredation + + exportexport))

Ecotrophic model representing central Chile, year 2000

2. Methods (cont.)

• An Ecopath model representing the central Chile marine ecosystem in year 1970 was calibrated with time series 1970-2004 (B, F, CPUE, …).

• Using the dynamic Ecosim module we simulated the biomass of hake (2005-2010), under the following scenarios:

• Fishing mortality (F): • Constant (F=F2005)• Zero (F= zero from 2007-2010)

• Recruitment: • Constant (average recruitment 2000-2005)

• Predation mortality• Constant (M2=2005), • Variable (jumbo squid biomass constant from 2005-2007, and then 50%

decrease from 2008-2010)

Inputs and outputs (bold) obtained from the balanced ecotrophic model representing theupwelling ecosystem off central Chile, year 2000.

Group name TL B P/B=Z Q/B EE GE Y F M2ton*km-2 year-1 year-1 ton*km-2year-1 year-1 year-1

cetaceans 4.29 0.01 0.60 10.00 0.17 0.06 0.10sea lion 3.93 0.07 0.25 20.00 0.38 0.01 0.10marine birds 3.55 0.07 0.50 20.00 0.00 0.03hake (j) 3.35 7.79 2.50 8.32 0.77 0.30 0.06 0.01 1.91hake(a) 3.92 12.19 0.46 5.16 0.46 0.09 2.14 0.18 0.03sardine (j) 2.03 41.36 1.45 14.53 0.30 0.10 8.51 0.21 0.23sardine(a) 2.03 14.60 1.88 18.75 0.28 0.10 4.59 0.32 0.20anchovy (j) 2.03 23.97 0.70 7.03 0.57 0.10 3.65 0.15 0.25anchovy (a) 2.03 14.63 2.12 21.20 0.24 0.10 4.52 0.31 0.20squid 3.73 2.05 3.50 10.61 0.99 0.33 3.50mesopelagic fish 3.40 29.56 1.20 12.00 0.99 0.10 1.20red squat lobster(j) 2.00 0.20 5.90 18.00 0.98 0.33 5.79red squat lobster(a) 2.00 0.36 3.57 12.50 0.96 0.29 0.08 0.22 3.22yellow squat lobster 2.00 0.08 3.57 11.60 0.78 0.31 0.06 0.77 2.03pink shrimp 2.00 0.40 2.50 12.00 0.47 0.21 0.09 0.22 0.94horse mackerel 3.52 23.98 0.56 14.20 0.36 0.04 3.16 0.13 0.07hoki 3.75 7.20 0.44 4.40 0.98 0.10 1.51 0.21 0.22sword fish 4.64 0.64 0.50 5.00 0.75 0.10 0.24 0.38black conger 3.53 0.30 0.70 3.50 0.35 0.20 0.07 0.23 0.02rattail fish 3.00 0.33 0.70 3.50 0.55 0.20 0.00 0.00 0.39flounder 3.00 0.20 0.70 3.50 0.01 0.20 0.00 0.01cardinal fish 3.50 0.78 0.70 3.50 0.29 0.20 0.12 0.15 0.06sand perch 3.57 0.05 0.70 3.50 0.10 0.20 0.00 0.07skates 3.00 0.25 0.36 2.41 0.13 0.15 0.01 0.05polichaets 2.00 1.89 2.41 15.90 0.00 0.15jellies 2.63 7.77 0.58 1.42 0.15 0.41 0.09copepods 2.25 57.28 45.00 154.52 1.00 0.29 44.96eufausiids 2.50 48.90 13.00 31.71 1.00 0.41 12.99phytoplankton 1.00 259.52 120.00 - 0.30 - 36.00detritus 1.00 - - - 0.00 -

EwE model (Walters et al., 1997)

ii B

PB ⎟

⎠⎞

⎜⎝⎛• Yi

∑=

•⎟⎠⎞

⎜⎝⎛•

n

1jji

jj DCB B

Q-- -- --BaBa ==

== -- --dtdB i ( )Bf --( )∑

=

n

1jjiij B,BcFiBi MoBi

( )EEB ii

i 1BP

−•⎟⎠⎞

⎜⎝⎛•

Unavailable prey B-V

Unavailable prey B-V

Available prey, VAvailable prey, V

v’Vv’V

Predator, PPredator, P

Prey vulnerability: top-down/bottom up controlPrey vulnerability: top-down/bottom up control

v = predator-prey specific behavioral exchange rate (‘vulnerability’)v = predator-prey specific behavioral exchange rate (‘vulnerability’)

aVPaVP

v(B-V)v(B-V)

3. Results (first part): Mass-balance Model

3 4 5

sword fish

jumbo squid

Cetaceans

sea lion

Chilean hake(a)

hoki

squid

marine birds

Pacific sand perch

black conger

horse mackerel

cardinal fish

mesopelagic fish

Chilean hake (j)

T r o p h I c L e v e l

3 4 5

Rel

ativ

e B

iom

ass

1965 1975 1985 1995 2005

1975 1985 1995 2005

Years

copepods euphausiids

macrobenthos anchovy

sardine mackerel

hake

F’s= 27%

V’s= 21%

PP=18%

Year

Rel

ativ

e bi

omas

s

Sea

surf

ace

tem

pera

ture

(°

C)

Upw

ellin

g in

dex

(m3

s-3)

Ano

mal

y in

PP

Years

0

0.5

1

1.5

2

2.5

-200

-100

-0

100

200

300

10

20

30

40

50

0

1965 1975 1985 1995 2005

hake

(j)

hake

(a)

jum

bo s

quid

mes

opel

agic

fish

hoki

ratta

il fis

hco

mm

on s

ardi

nean

chov

y

Bio

mas

s(m

illio

n to

ns)

DC

jum

bo s

quid

(%

in w

eigh

t)Q

jum

bo s

quid

(mill

ion

tons

)

0

10

20

30

40

50

0

0.5

1

1.5

2

2.5

3

0

0.2

0.4

0.6

0.8

1

EwE estimated a biomass for jumbo squid of ~ 300 thousand tons (EE=0.5)

B and Q resulted from multiplying Ecopathinputs/outputs by the surface of the study area

0

1

2

3

hake

(j)

hake

(a)sa

rdine (

j)sa

rdine (

a)an

chovy

(j)an

chovy

(a)

jumbo sq

uid

F M2 M0

0%

20%

40%

60%

80%

100%

hake

(j)

hake

(a)sa

rdine (

j)sa

rdine (

a)an

chovy

(j)an

chovy

(a)

jumbo sq

uid

Mor

talit

y co

effic

ient

s(y

ear-1

)M

orta

lity

coef

ficie

nts

(% o

f Z)

Year 2000

3. Results (second part). EwE simulations

Mixed control (v=2) Top-down control (v=5)B

iom

ass

(thou

sand

tons

)B

iom

ass

(mill

ion

tons

)

0

200

400

600

800

1000

1200

2000 2001 2002 2003 2004 2005 2006

hake (j)hake (a)

0

1

2

3

4

2000 2001 2002 2003 2004 2005 2006

anchovycommon sardine

0

200

400

600

800

1000

1200

2000 2001 2002 2003 2004 2005 2006

hake (j)hake (a)

0

1

2

3

4

2000 2001 2002 2003 2004 2005 2006

anchovycommon sardine

Y e a r s

3. Results (third part). EwE simulations (fitted model)

0

5

10

15

1970 1980 1990 2000 2010

0

0.1

0.2

0.3

0.4

1970 1980 1990 2000 20100

0.1

0.2

0.3

0.4

1970 1980 1990 2000 2010

F=cte, R=cte, M2=variableF=cte, R=cte, M2=cte

0

1

2

3

4

5

6

1970 1980 1990 2000 2010

CPUEAcousticScenario 1

0

1

2

3

4

5

6

1970 1980 1990 2000 2010

CPUEAcousticScenario 2

Bsq

uid

(rel

.)

Rel

ativ

e bi

omas

sF

(yea

r-1)

Year

Year

0

5

10

15

1970 1980 1990 2000 2010

F=0, R=cte, M2=cte F=0, R=cte, M2=variable

0

1

2

3

4

5

6

1970 1980 1990 2000 2010

CPUEAcousticScenario 3

0

1

2

3

4

5

6

1970 1980 1990 2000 2010

CPUEAcousticScenario 4

0

0.1

0.2

0.3

0.4

1970 1980 1990 2000 20100

0.1

0.2

0.3

0.4

1970 1980 1990 2000 2010

F (y

ear-1

)

Year

Year

Bsq

uid

(rel

.)

Rel

ativ

e bi

omas

s

4. Conclusions

• The outbreak of jumbo squid during early 2000s could have had different impacts on pelagic and demersal fish stocks off central Chile:

• moderate-to-strong impact in hake (depending on the kind of trophic control simulated);

• not noticeable impact on common sardine and anchovy (regardless the kind of trophic control simulated).

• However, these results strongly rely on the diet composition used. In particular, the proportion of hake, common sardine and anchovy in the stomach contents of jumbo squid are against the well-know opportunistic behavior of this predator.

• More reliable data on DC is needed to evaluate the impacts of this predator in the food web.

• The dynamics of the stock of hake simulated using EwE indicates:• recovery of the stock in the medium- to long-term could be possible only

under a F=0 scenario.• the effect of predation by jumbo squid on the dynamic of hake would be

non-significant from 2005 onwards.

Thanks for your attention.

Thanks to the Co-convenors (Bob, Jock and John) for the invitation to participate in this workshop.

Thanks to the Pelagic Fisheries Research Program (PFRP) and GLOBEC-CLIOTOP WG-3.

Sea lion

Hake (a)

Hake (j)

Common sardine (j)

Anchovy (a)

Jumbo squid

Anchovy (j)

Common sardine (a)

Sea

lion

Hak

e (a

)

Hak

e (j)

Com

mon

sar

dine

(j)

Anch

ovy

(a)

Jum

bo s

quid

Com

mon

sar

dine

(a)

Anch

ovy

(j)

Mixed Trophic Impacts (year 2000)