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Mark N. Maunder, John R. Sibert, Alain Fonteneau, John Hampton, Pierre Kleiber, and Shelton J. Harley
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?
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 pre-
industrial levels.”
Myers and Worm 2003
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002C
atch
(t)
OtherSkipjackYellowfinBigeyeAlbacore
A
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002
Cat
ch (t
)
OtherPurse seinePole-and-lineLongline
B
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002
Cat
ch (t
)
NorthEquatorialTropicalSubtropicalTemperate
C
Pacific Ocean Tuna Catch Data
By species
By method
By area
Myers and Wormdata
-
-
-
-
-
-----051122
3
3
4707580859095100105110115120125130135140145150155160165170175180175170165160155150145140135130125120
707580859095100105110115120125130135140145150155160165170175180-175-170-165-160-155-150-145-140-135-130-125-120-50
-45
-40
-35
-30
-25-20-15-10-50510152025
30
35
40
Jap LL 1952-1999 20000YFTBET
BFTALB
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
One species dominates
0
2
4
6
8
10
1950 1965 1980 1995
BillfishSouthern bluefinYellowfinBigeyeAlbacore
Total temperateD
CP
UE
More often than not community CPUE declines faster than abundance
1i ii i i i
i
B Br B q EBt K
⎛ ⎞∂= − −⎜ ⎟∂ ⎝ ⎠
0iBt
∂=
∂
SS SS
i i ii i
B CPUEK q K
<∑ ∑
2i i
i ii ii i
i i ii i
q qK Kr rK q K
>∑ ∑∑ ∑
( )2 2 2 2 2 22i i i j i j i i i j i ji i j i i j
q K q q K K q K q q K K< <
+ > + +∑ ∑ ∑ ∑
1 , pairs Biomass declines faster than CPUEi i
j j
r q i jr q< < ∀ ⇒
1i
j
<
22
i i i i ii i i
q K K q K⎛ ⎞>⎜ ⎟
⎝ ⎠∑ ∑ ∑
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
Is data consistent
Catchability higher in the early period to describe rapid decline in CPUE0
1
2
3
4
1950 1960 1970 1980 1990 2000
Rec
ruitm
ent a
nom
aly D Bigeye (Pacific)
0.00
0.10
0.20
Cat
chab
ility
0.00
0.01
0.02
0.03
0.04
0.05
Cat
chab
ility
C Yellowfin (10°-40°S, 160°E-150°W)
Fishery versus environment for yellowfin tuna in the EPO
Year75 77 79 81 83 85 87 89 91 93 95 97 99 01 03
0
500
1000
1500
No fishingFishing
Bio
mas
s
Fishery Impact on EPO bigeye tuna
Year
75 77 79 81 83 85 87 89 91 93 95 97 99 01 03
0.0
0.2
0.4
0.6
0.8
1.0
Fish
ery
impa
ct
LonglineFloating objectSmall discards
Relative abundance of bigeye tuna in the EPO
0
0.20.4
0.6
0.81
1.2
1.4
1.61.8
2
1975 1980 1985 1990 1995 2000 2005
Year
Rel
ativ
e ab
unda
nce
Integrated stock assessement CPUE
Estimate management quantities (how useful they are?)
Year -- Año
0.0
0.2
0.4
0.6
0.8
1.0
Spa
wni
ng b
iom
ass
ratio
Coc
ient
e de
bio
mas
a re
prod
ucto
ra
75 77 79 81 83 85 87 89 91 93 95 97 99 01 03
Determine increase in yield by changing fishing methods: Yellowfin tuna in the EPO
Method MSY (`000 t)All 285Floating Object 194
Unassociated 243
Dolphin associated 320
longline 386
Predict effects of management
Year -- Año
Tons
-- T
onel
adas
75 77 79 81 83 85 87 89 91 93 95 97 99 01 03 05 07 09
0
200000
400000
600000
800000
No closureClosure
Abundance of tunas in the Pacific Ocean
Integrated models
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
1952
1955
1958
1961
1964
1967
1970
1973
1976
1979
1982
1985
1988
1991
1994
1997
2000
Adu
lt bi
omas
s (t)
YellowfinBigeyeAlbacore
Japanese longline CPUE
0
10
20
30
40
50
60
70
1952
1955
1958
1961
1964
1967
1970
1973
1976
1979
1982
1985
1988
1991
1994
1997
2000
CPU
E (k
g pe
r 100
hoo
ks)
YellowfinBigeyeAlbacore
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
