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)