Transcript Problems with interpreting catch-per-unit-of

Problems with interpreting catch-per-unit-of-effort data
to assess the status of individual stocks and
communities: is integrated stock assessment,
ecosystem modeling, management strategy evaluation,
or adaptive management the solution?
Mark N. Maunder, John R. Sibert, Alain Fonteneau, John
Hampton, Pierre Kleiber, and Shelton J. Harley
The importance of appropriate
interpretation and analysis of data
• “… by the illogic of the old paradigms …
yet another randomized trial … was
performed … and resulted in 25 more
infant deaths …” Royal 1997
“…large predatory fish biomass
today is only about 10% of preindustrial levels.”
Myers and Worm 2003
Pacific Ocean Tuna Catch Data
3,000,000
A
Other
2,500,000
By species
Catch (t)
Skipjack
2,000,000
Yellowfin
Bigeye
1,500,000
Albacore
1,000,000
500,000
0
1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002
3,000,000
B
Other
By method
Catch (t)
2,500,000
Purse seine
Pole-and-line
2,000,000
Longline
1,500,000
1,000,000
500,000
0
1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002
3,000,000
By area
Catch (t)
2,500,000
2,000,000
C
North
Equatorial
Tropical
Subtropical
1,500,000
Temperate
1,000,000
500,000
0
1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002
Myers and Worm
data
40
-120 -125 -130 -135 -140 -145 -150 -155 -160 -165 -170 -175 180 175 170 165 160 155 150 145 140 135 130 125 120 115 110 105 100 95 90 85 80 75 70
4
35
3
30
3
25
2
20
2
15
1
10
1
5
5
0
0
-5
-
-10
-
-15
-
-20
-
-25
-
-30
-
-35
-
-40
-
-45
-
-50
-120 -125 -130 -135 -140 -145 -150 -155 -160 -165 -170 -175 180 175 170 165 160 155 150 145 140 135 130 125 120 115 110 105 100 95 90 85 80 75 70
Jap LL 1952-1999
YFT
BET
BFT
ALB
20000
Spatial expansion of the longline
fishery
Change in targeting: from albacore to bigeye
Blue is total catch, green is Taiwan CPUE, red is Japan CPUE
CPUE is inconsistent with catch and population
dynamics
Blue is total catch, red is CPUE
4
2
2
One species dominates
0
10
D
Total temperate
8
CPUE
16
Billfish
Southern bluefin
Yellowfin
Bigeye
Albacore
6
4
H
12
8
4
2
0
1950
0
1965
1980
1995
0
1950
More often than not community CPUE
declines faster than abundance
 Bi
Bi
 ri 1 
t
 Ki

 Bi  qi EBi

BSS
CPUESS

 K i  q iK i
i
qi
i r Ki
i

 Ki
2


2
q
K

K
q
Ki



i
i
i
i


 i

i
i
qi
1
qj
Bi
0
t
q K
2
i
i
2
i
i
i
qi2
i r Ki
i
 qi K i
i
 2 qi qj Ki K j   qi Ki    qi  qj  Ki Kj
2
i j
2
i
ri qi
  1i, j pairs  Biomass declines faster than CPUE
rj q j
2
i j
2
Integrated stock assessment
models
•
•
•
•
•
•
•
•
•
Uses all data
Determine if data is consistent
Fishery versus environment
Fishery impact by gear
Use more information for longer predictions
Estimate management quantities
Determine yield efficiency of gear
Investigate management options
Can be combined to calculate community
abundance
Catcha
Is data consistent
0.10
0.00
Catchability
0.05
Yellowfin (10°-40°S, 160°E-150°W)
C
0.04
0.03
0.02
0.01
Recruitment anomaly
0.00
4
Bigeye (Pacific)
D
3
2
Catchability higher in the
early period to describe
0rapid decline in CPUE
1
1950
1960
1970
1980
1990
2000
Fishery versus environment for
yellowfin tuna in the EPO
No fishing
Fishing
Biomass
1500
1000
500
0
75
77
79
81
83
85
87
89
91
Year
93
95
97
99
01
03
Fishery Impact on EPO bigeye tuna
1.0
Longline
Floating object
Small discards
Fishery impact
0.8
0.6
0.4
0.2
0.0
75
77
79
81
83
85
87
89
Year
91
93
95
97
99
01
03
Relative abundance of bigeye tuna
in the EPO
2
1.8
Relative abundance
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1975
1980
1985
1990
1995
2000
Year
Integrated stock assessement
CPUE
2005
Estimate management quantities
(how useful they are?)
Spawning biomass ratio
Cociente de biomasa reproductora
1.0
0.8
0.6
0.4
0.2
0.0
75
77
79
81
83
85
87
89
91
Year -- Año
93
95
97
99
01
03
Determine increase in yield by
changing fishing methods: Yellowfin
tuna in the EPO
Method
All
Floating Object
MSY (`000 t)
285
194
Unassociated
243
Dolphin associated
320
longline
386
Predict effects of management
800000
No closure
Closure
Tons -- Toneladas
600000
400000
200000
0
75
77
79
81
83
85
87
89
91
93
Year -- Año
95
97
99
01
03
05
07
09
Abundance of tunas in the Pacific
Ocean
Integrated models
1
0.9
7,000,000
5,000,000
0.6
Yellowfin
4,000,000
Year
0.7
Bigeye
3,000,000
0.5
0.4
Albacore
0.3
2,000,000
0.2
1,000,000
0.1
0
1940
1950
1960
1
19
52
19
55
19
58
19
61
19
64
19
67
19
70
19
73
19
76
19
79
19
82
19
85
19
88
19
91
19
94
19
97
20
00
0
70
1.60E+06
60
1.40E+06
50
Yellowfin
1.20E+06
Bigeye
1.00E+06
40
30
Albacore
Biomass (t)
CPUE (kg per 100 hooks)
Japanese longline CPUE
Estimated biomass
Biomass - no fishin
Biomass - no longl
8.00E+05
6.00E+05
20
4.00E+05
10
2.00E+05
0
19
52
19
55
19
58
19
61
19
64
19
67
19
70
19
73
19
76
19
79
19
82
19
85
19
88
19
91
19
94
19
97
20
00
Adult biomass (t)
0.8
6,000,000
0.00E+00
1940
1950
1960
Management of fish stocks
• Sustainable fisheries management is based on
surplus production
• Surplus production increases as the abundance
falls towards BMSY
• BMSY is often much less than half the unexploited
level
• BMSY and MSY are dependent on many factors
• CPUE alone tells us nothing about the above
Management of communities and
ecosystems
• Cannot maximize yield of two species
caught simultaneously by the same gear
because their productivities and
catchabilities differ
• What would be the impact on the
ecosystem if all commercially valuable
stocks were fished at their single species
MSY
Adaptive management, management
strategy evaluation, and ecosystem
models
• Adaptive management provides information for
integrated stock assessments and has been
used for yellowfin tuna in the EPO
• Management strategy evaluation can be used to
compare integrated stock assessments to other
approaches (e.g. raw CPUE). Operating model
is often based on integrated stock assessment
• Multispecies and ecosystem models can be
used to investigate how species interactions
may influence single species integrated stock
assessments and management
Conclusions
• Integrated stock assessment provides a
much broader picture than simple CPUE
• Integrated stock assessment can provide
many insights into managing a fishery
• Integrated stock assessment is not the
answer to everything, other methods may
provide alternative perspectives
• Management strategy evaluation provides
a method to compare Integrated stock
assessment with alternatives
The End