75
ASSESSMENT OF BIGEYE TUNA (THUNNUS OBESUS) IN THE EASTERN PACIFIC OCEAN January 1975 – December 2006
ASSESSMENT OF BIGEYE TUNA (THUNNUS OBESUS) IN THE EASTERN PACIFIC OCEAN
January 1975 – December 2006
Outline
• Stock assessment– Overview of assessment model– Fishery data– Assumptions– Results of base case model– Projections
• Sensitivity analyses• Summary and conclusions• Discussion
Overview of assessment
• Age-structured, statistical, catch-at-length model (Stock Synthesis II).
• Same type of model as A-SCALA or MULTIFAN-CL
• Differences between SS2 and A-SCALA
Bigeye fishery definitions
Recent FLT (2-5)Discards (10-13)
N Longline (8)S Longline (9)
Early FLT (1)Early & Recent UNA (6, 7)
40
30
20
10
0
10
20
30
40
150 140 130 120 110 100 90 80 70
1, 6-7
40
30
20
10
0
10
20
30
40
150 140 130 120 110 100 90 80 70
8
9
40
30
20
10
0
10
20
30
40
150 140 130 120 110 100 90 80 70
2, 10
3, 11
5, 13
4, 12
FLT – Floating objects; UNA - Unassociated
0
5000
10000
15000
20000
25000
30000Fishery -- Pesqueria 1
75 80 85 90 95 00 05
Fishery -- Pesqueria 2
75 80 85 90 95 00 05
Fishery -- Pesqueria 3
75 80 85 90 95 00 05
Fishery -- Pesqueria 4
75 80 85 90 95 00 05
0
5000
10000
15000
20000
25000
30000Fishery -- Pesqueria 5 Fishery -- Pesqueria 6 Fishery -- Pesqueria 7 Fishery -- Pesqueria 8
0
5000
10000
15000
20000
25000
30000Fishery -- Pesqueria 9 Fishery -- Pesqueria 10 Fishery -- Pesqueria 11 Fishery -- Pesqueria 12
0
5000
10000
15000
20000
25000
30000Fishery -- Pesqueria 13
Year -- Año
Ton
s --
To
ne
lad
as
Data - catch
Early FLT
N Offshore FLT
Equatorial FLT Coastal FLTS Offshore FLT
Early UNA Recent UNA N LL
S LLDisc - S FLT Disc – Eq FLT Disc – coastal FLT
Disc -N FLT
0.0
0.05
0.10
0.15
0.20
0.25
0.30
93 94 95 96 97 98 99 00 01 02 03 04 05 06
Fishery -- Pesqueria4/12
0.0
0.05
0.10
0.15
0.20
0.25
0.30
93 94 95 96 97 98 99 00 01 02 03 04 05 06
Fishery -- Pesqueria5/13
0.0
0.05
0.10
0.15
0.20
0.25
0.30
93 94 95 96 97 98 99 00 01 02 03 04 05 06
Fishery -- Pesqueria2/10
0.0
0.05
0.10
0.15
0.20
0.25
0.30
93 94 95 96 97 98 99 00 01 02 03 04 05 06
Fishery -- Pesqueria3/11
Year -- Año
Dis
card
s/R
eta
ine
d f
ish
--
De
sca
rte
s/P
ece
s re
ten
ido
sData - discards
Southern FLT Equatorial FLT
Northern FLTInshore FLT
0
1
2
3
4
5
Fishery -- Pesqueria 1
75 80 85 90 95 00 05
0.0
0.5
1.0
1.5
Fishery -- Pesqueria 2
75 80 85 90 95 00 05
0.0
0.5
1.0
1.5
2.0
2.5
Fishery -- Pesqueria 3
75 80 85 90 95 00 05
0.0
0.5
1.0
1.5
2.0
Fishery -- Pesqueria 4
75 80 85 90 95 00 05
0.0
0.5
1.0
1.5
Fishery -- Pesqueria 5
0
2
4
6
Fishery -- Pesqueria 6
0
1
2
3
4
Fishery -- Pesqueria 7
0
20
40
60
80
100
120
140Fishery -- Pesqueria 8
200
300
400
500
600
700
Fishery -- Pesqueria 9
0.0
0.5
1.0
1.5
Fishery -- Pesqueria 10
0.0
0.5
1.0
1.5
2.0
2.5
Fishery -- Pesqueria 11
0.0
0.5
1.0
1.5
2.0
Fishery -- Pesqueria 12
0.0
0.5
1.0
1.5
Fishery -- Pesqueria 13
Year -- Año
Tho
usan
ds o
f day
s an
d hu
ndre
ds o
f tho
usan
ds o
f hoo
ksM
iles
de d
ias
y ci
ento
s de
mile
s de
anz
uelo
sData - effort
Early FLT
N Offshore FLT
Equatorial FLT Coastal FLTS Offshore FLT
Early UNA Recent UNA N LL
S LL Disc - S FLT Disc – Eq FLT Disc – coastal FLT
Disc -N FLT
0
1
2
3
4Fishery -- Pesqueria 1
75 80 85 90 95 00 05
0
1
2
3
Fishery -- Pesqueria 2
75 80 85 90 95 00 05
0.5
1.0
1.5
2.0
2.5
Fishery -- Pesqueria 3
75 80 85 90 95 00 05
0
1
2
3
4
5Fishery -- Pesqueria 4
75 80 85 90 95 00 05
0.0
0.5
1.0
1.5
2.0
2.5
3.0Fishery -- Pesqueria 5
0
2
4
6
8
Fishery -- Pesqueria 6
0
1
2
3
4
5
Fishery -- Pesqueria 7
0
1
2
3
4Fishery -- Pesqueria 8
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8Fishery -- Pesqueria 9
0
1
2
3
4
5
Fishery -- Pesqueria 10
0
1
2
3
4
Fishery -- Pesqueria 11
0
1
2
3
4Fishery -- Pesqueria 12
0
2
4
6
8Fishery -- Pesqueria 13
Year -- Año
Sca
led
CP
UE
--
CP
UE
esc
ala
do
Data - CPUE
Early FLT
N Offshore FLT
Equatorial FLT Coastal FLTS Offshore FLT
Early UNA Recent UNA N LL
S LL Disc - S FLT Disc – Eq FLT Disc – coastal FLT
Disc -N FLT
Data - Length frequency data
Quarter20001997 2005
Assumptions (base case) - movement
• Tagging records indicate little exchange of bigeye between E and W Pacific
• Results from conventional and archival tagging indicate regional fidelity for bigeye in EPO
• Different CPUE trends between EPO and WCP
DATA
• Single stock of bigeye in EPO• No net movement of fish between the eastern and
western Pacific• SA for EPO and Pacific wide are consistent
ASSUMPTIONS
Assumptions (base case) - growth
• Von Bertalanffy – fixed parameters
Assumptions (base case) – M
Assumptions (base case) - cont.
• Age-specific maturity and fecundity indices• No S-R relationship (steepness = 1)
Results (base case)
• Fit to the length frequency
• Fishing mortality
• Selectivity
• Recruitment
• Biomass
Fit to LF data – Pearson residuals
Fit to CPUE data – Floating objectFishery 2
0
10000
20000
30000
40000
50000
60000
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
129
132
YEAR
CP
UE
Fishery 3
0
5000
10000
15000
20000
25000
30000
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
129
132
YEAR
CP
UE
Fishery 5
0
5000
10000
15000
20000
25000
30000
35000
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
129
132
YEAR
CP
UE
Fishery 8
0
1
2
3
4
5
6
0 3 6 9 12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
YEAR
CP
UE
Fit to CPUE data – Longline
Fishery 9
0
0.5
1
1.5
2
2.5
3
0 3 6 9 12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
Quarter
CP
UE
Ages 1-4 - Edades 1-4
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 5-8 - Edades 5-8
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 9-12 - Edades 9-12
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 13-16 - Edades 13-16
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 17-20 - Edades 17-20
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 21-24 - Edades 21-24
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 25-28 - Edades 25-28
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 29-32 - Edades 29-32
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 33-36 - Edades 33-36
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Ages 37-40 - Edades 37-40
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
Fishing mortalityAges 1-4 Ages 5-8
Ages 13-16
Ages 17-20
Ages 9-12
Ages 21-24
Ages 25-28 Ages 29-32
Ages 33-36 Ages 37-40
Age-specific fishing mortality
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0 5 10 15 20 25 30 35 40
Age in quarters - Edad en trimestres
Ave
rag
e t
ota
l F -
F t
ota
l me
dia
1975-1992 1993-2006
Ages 1-4 - Edades 1-4
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
Ages 9-12 - Edades 9-12
0.00
0.05
0.10
0.15
0.20
1970 1975 1980 1985 1990 1995 2000 2005 2010
1975-1992
1993-2006
Size selectivity
Early FLT
N Offshore FLT
Equatorial FLT
Coastal FLT
S Offshore FLT
Early UNA
Recent UNA
N LL S LL
Recruitment
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
BiomassBiomass of fish 0.75 + years old
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s (t
on
s)
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s (t
on
s)
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
Spawning biomass
Population fecundity
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
1975 1980 1985 1990 1995 2000 2005
Year
Sp
aw
nin
g b
iom
as
s (
mt)
No LL
No FO
No Dis
No-fishing plot
0
10
20
30
40
50
60
70
80
1975 1980 1985 1990 1995 2000 2005 2010
Year
Me
an
we
igh
t (k
g)
PS
LL
Average weight
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
2007
2006
2005
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
2007
2006
2005
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
2007
2006
2005
Retrospective analysis - biomass
0
2
4
6
1975 1980 1985 1990 1995 2000 2005
Year
Rel
ativ
e re
cru
itm
ent
2007
2006
2005
0
2
4
6
1975 1980 1985 1990 1995 2000 2005
Year
Rel
ativ
e re
cru
itm
ent
2007
2006
2005
0
2
4
6
1975 1980 1985 1990 1995 2000 2005
Year
Rel
ativ
e re
cru
itm
ent
2007
2006
2005
Retrospective analysis - recruitment
Comparisons with A-SCALA
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
SS2 2007
A-SCALA 2006
A-SCALA 2007
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
SS2 2007
A-SCALA 2006
A-SCALA 2007
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
SS2 2007
A-SCALA 2006
A-SCALA 2007
Comparisons with A-SCALA assessments
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s (t
on
s)
SS2 2007
A-SCALA 2006
A-SCALA 2007
Comparisons with A-SCALA assessments
0
2
4
6
1975 1980 1985 1990 1995 2000 2005
Year
Rel
ativ
e re
cru
itm
ent
SS2 2007
A-SCALA 2007
Comparisons to reference points
• Spawning biomass depletion (SBR)
Spawning biomass ratio
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
SS2 2007
SBR comparison with A-SCALA
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
SS2 2007
A-SCALA 2006
A-SCALA 2007
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
SS2 2007
A-SCALA 2006
A-SCALA 2007
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
SS2 2007
A-SCALA 2006
A-SCALA 2007
Time varying indicators
0.00
0.05
0.10
0.15
0.20
0.25
0.30
1970 1980 1990 2000 2010
SA
MS
Y/S
0
0
50,000
100,000
150,000
200,000
1970 1980 1990 2000 2010
AM
SY
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1970 1980 1990 2000 2010
Sre
ce
nt/
SA
MS
Y
0
1
2
3
4
5
6
7
1970 1980 1990 2000 2010
F m
ult
ipli
er
AMSY-quantities
F's 2004 & 2005Base case 2003-2004 2005-2006
AMSY 92,758 101,316 86,134
BAMSY 313,767 325,300 300,779
SAMSY 688 700 664
BAMSY/B0 0.27 0.28 0.26
SAMSY/S0 0.22 0.23 0.22Crecent/AMSY 1.10 1.03 1.21Brecent/BAMSY 1.08 1.05 1.13
Srecent/SAMSY 0.90 0.89 0.93Fmultiplier 0.77 0.75 0.90
AMSY-quantities – by fishery
All gears PS only LL onlyAMSY 92,758 62,566 175,340BAMSY 313,767 230,786 312,126
SAMSY 688 510 416
BAMSY/B0 0.27 0.20 0.27
SAMSY/S0 0.22 0.17 0.14Crecent/AMSY 1.10 1.67 0.60Brecent/BAMSY 1.08 1.47 1.09
Srecent/SAMSY 0.90 1.22 1.49Fmultiplier 0.77 1.41 4.32
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.5 1 1.5 2 2.5 3 3.5 4
S/SMSY(t)
1/F
scal
e
Forward simulations
• Biomass
• Spawning biomass depletion
• Surface fishery catch
• Longline catch
Spawning biomass ratio
Predicted catches – purse-seineSurface fisheries
0
5000
10000
15000
20000
25000
30000
35000
1975 1980 1985 1990 1995 2000 2005 2010 2015
Year
To
ns
Predicted catches – longlineLongline fisheries
0
5000
10000
15000
20000
25000
30000
35000
1975 1980 1985 1990 1995 2000 2005 2010 2015
Year
To
ns
Sensitivity analyses
1. Spawner-recruitment relationship (steepness = 0.75)
2. Growth- Growth estimated - Linf fixed (171.5 and 201.5)
3. Fitting to the initial equilibrium catch
4. Use of iterative reweighting of data
5. Time blocking of selectivity and catchability for southern longline fishery
6. Inclusion of new Japanese longline data
Stock-recruitment relationship (h = 0.75)
Biomass
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
basecase
h = 0.75
Recruitment
0
2
4
6
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
basecase
h = 0.75
Spawning biomass ratio
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
basecase
h = 0.75
Spawner-recruitment curve
0.00E+00
2.00E+06
4.00E+06
6.00E+06
8.00E+06
1.00E+07
1.20E+07
1.40E+07
1.60E+07
1.80E+07
0.00E+00 5.00E+05 1.00E+06 1.50E+06 2.00E+06 2.50E+06 3.00E+06 3.50E+06 4.00E+06
Female Spbio
Rec
ruit
men
t
Expect-mean
Bias-adjust
Time_series
Use of CPUE time series for southern longline fishery only
Spawning biomass ratio
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
basecase
cpue 9
Model fit to CPUE data
0
0.5
1
1.5
2
2.5
3
0 3 6 9 12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
YEAR
CP
UE
Assumed value for the asymptotic length parameter of the VB growth
curve
Growth curves
0
50
100
150
200
250
0 5 10 15 20 25 30 35 40
Age
Mea
n l
eng
th a
t ag
e (c
m)
Base case
Growth estimated
0
50
100
150
200
250
0 5 10 15 20 25 30 35 40
Age
Mea
n
len
gth
at
age
(cm
)
Base case
Lmax = 201.5
Lmax = 171.5
0.0
0.3
0.5
0.8
1.0
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
Lmax = 171.5
Growth estimated
Lmax = 201.5
SBR
Fit to initial equilibrium catch
Spawning biomass ratio
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
basecase
init_catch
Use of iterative reweighting
Iterative reweighting
Basecase Iteration 1 Iteration 2 Iteration 2used used mse
Rec 0.60 0.50 0.63 0.68
Mean input SECPUE
2 0.40 0.38 0.41 0.443 0.40 0.67 0.73 0.765 0.40 0.67 0.76 0.808 0.40 0.52 0.59 0.669 0.20 0.16 0.36 0.54
Mean effective sample sizeLF
1 3.77 21.75 21.86 19.822 15.02 73.04 74.78 74.333 13.58 67.41 64.30 62.514 1.88 7.28 7.05 7.435 9.89 52.89 56.95 57.476 6.45 30.25 31.62 31.637 2.91 15.26 15.66 15.518 4.22 63.96 72.83 73.669 14.64 222.61 255.92 258.21
Spawning biomass ratio
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
basecase
iter_reweight
Fit to CPUE data
0
0.5
1
1.5
2
2.5
3
3.5
4
0 3 6 9 12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
YEAR
CP
UE
Residual plot
Use two time blocks for selectivity and catchability of the southern longline
fishery
Fit to LF data – base case
Spawning biomass ratio
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
awn
ing
bio
mas
s ra
tio
basecase
time blocks
time blocks - iter. rw.
Fit to CPUE data
0
0.5
1
1.5
2
2.5
3
0 3 6 9 12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
Quarter
CP
UE
0
0.5
1
1.5
2
2.5
50
53
56
59
62
65
68
71
74
77
80
83
86
89
92
95
98
101
104
107
110
113
116
119
122
125
Quarter
CP
UE
0
0.5
1
1.5
2
2.5
0 3 6 9 12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
Quarter
CP
UE
0
0.5
1
1.5
2
2.5
50
53
56
59
62
65
68
71
74
77
80
83
86
89
92
95
98
101
104
107
110
113
116
119
122
125
Quarter
CP
UE
With iterative reweighting
Without iterative reweighting
Residual plot
Inclusion of the new Japanese longline data
Biomass
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
1975 1980 1985 1990 1995 2000 2005
Year
Su
mm
ary
bio
mas
s (t
on
s)
basecase
new JPN data
Recruitment
0
2
4
6
1975 1980 1985 1990 1995 2000 2005
Year
Re
lati
ve
re
cru
itm
en
t
basecase
new JPN data
SBR
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1975 1980 1985 1990 1995 2000 2005
Year
Sp
aw
nin
g b
iom
as
s r
ati
o
basecase
new JPN data
Comparisons between models
Smsy/S0 Srecent/Smsy Fmultiplier
Basecase 0.22 0.90 0.77
h = 0.75 0.31 0.61 0.55cpue9 0.22 0.50 0.61growth est. 0.21 1.19 0.98Lmax = 171.5 0.21 1.58 1.34Lmax = 201.5 0.22 0.60 0.57iter. rwt 0.23 0.26 0.79t. blocks 0.25 0.82 1.11t. blocks (iter. rwt) 0.23 0.26 0.79
Summary: Main results
• Both total and spawning biomass is estimated to have substantially declined since 2000
• Current biomass level is low compared to average unexploited conditions
• The current effort levels are too high to maintain the population at level that will support AMSY
• Yileds could be increased if more of the catch was taken in the longline fisheries
What is robust
• Fishing mortality levels are greater than that necessary to achieve the maximum sustainable yield
• Two exceptions: Lmax fixed and time blocks
Plausible Sensitivities and Uncertainties
• Results are more pessimistic with the inclusion of a stock-recruitment relationship
• Biomass trends are sensitive to the weighting of different datasets
• Recent estimates are uncertain and subject to retrospective bias
Conclusions
• Current spawning biomass is unlikely to remain at or above the level required to produce AMSY.
• In the most recent years the fishing mortality is greater than that required to produce AMSY.
• Under average recruitment, the stock is predicted to be below the level that would support AMSY unless fishing mortality levels are reduced further than the current restrictions.
Growth estimationData Basecase h = 0.75 cpue 9 All params Lmax = 171.5 Lmax = 201.5 Fit init. catch Iter. reweight t. blocks t_blocks (iter. rw)
CPUE
2 -20.72 -20.59 - -20.16 -19.04 -22.13 -20.24 -13.60 -20.79 -16.83923 23.61 23.53 - 23.87 25.01 22.41 23.86 10.76 23.69 8.94565 21.41 21.82 - 22.56 23.83 18.99 22.93 12.56 21.20 10.79268 -5.60 -5.83 - -7.15 -6.49 -7.42 -5.22 9.95 -5.15 0.07553549 -153.53 -154.17 -138.23 -156.17 -156.97 -151.35 -154.22 14.02 -160.81 -107.21
Size comps.1 166.84 166.73 166.11 165.71 165.29 167.37 166.79 984.33 166.70 958.9022 195.64 196.72 186.15 205.48 211.91 196.34 196.88 962.80 197.08 945.1433 246.40 246.55 236.11 251.42 258.01 243.94 246.64 1229.45 245.82 1277.034 70.93 75.51 73.64 72.02 70.70 70.10 71.93 268.08 75.36 256.2795 136.75 137.08 129.47 144.17 148.92 136.10 137.49 724.54 137.23 688.796 132.05 132.21 131.48 133.66 134.39 132.97 130.95 655.15 131.98 621.8097 129.59 129.00 128.32 129.50 122.77 136.08 128.03 714.51 129.65 713.5548 124.17 123.89 123.66 119.90 119.22 123.74 123.49 1631.91 123.36 1469.029 272.40 274.77 276.30 244.80 222.73 289.84 286.84 3695.10 236.49 3417.48
Age at length - - - 103.72 112.73 81.44 - - - -
Recruitment -24.72 -20.69 -26.70 -30.02 -32.91 -19.84 -21.23 17.30 -20.16 18.9462
Total 1315.22 1326.52 1286.32 1403.29 1400.07 1418.58 1334.92 10916.86 1281.65 10262.72
Comparisons between models
