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 pre industrial levels.”

Myers and Worm 2003

Pacific Ocean Tuna Catch Data

By species 3,000,000

A

2,500,000 2,000,000 Other Skipjack Yellowfin Bigeye Albacore 1,500,000 1,000,000 500,000 0 1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 By method By area 3,000,000

B

2,500,000 2,000,000 Other Purse seine Pole-and-line 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

C

2,500,000 2,000,000 1,500,000 1,000,000 500,000 North Equatorial Tropical Subtropical Temperate 0 1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 Myers and Worm data

35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 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 40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -45 -50 -120 -125 -130 -135 -140 -145 -150 -155 -160 -165 -170 -175 180 Jap LL 1952-1999 YFT 175 BFT BET ALB 170 165 20000 160 155 150 145 140 135 130 125 120 115 110 105 100 95 90 85 80 75 70 -50

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

6 4 2 4 3 5

A

2 1 0 8

B

Total equatorial Total tropical 0 10

C

8 6 Total subtropical 4 2

One species dominates

0 10

D

Total temperate 4 2 8 6 Billfish Southern bluefin Yellowfin Bigeye Albac ore 0 1950 1965 1980 1995 4 2 0 16

H

12 8 4 0 1950 4

E

3 2 1 4 3 0 5

F

2 1 0 6

G

Albacore equatorial Albacore tropical Albacore subtropical Albacore temperate 1965 1980 1995 14 10 1.6

1.2

I

6 0.8

2 0.4

-2 20 15 10 5 0 0.0

J

1.0

0.8

0.6

0.4

0.2

0.0

1.2

K

30 25 20 15 10 5 0 40 30 20 10 0 0.9

0.6

0.3

0.0

0.10

L

0.08

0.06

0.04

0.02

0.00

1950 Bigeye equatorial Bigeye tropical Bigeye subtropical Bigeye temperate 1965 1980 1995 160 3

M

120 2 80 1 40 0 30 20 10 0 10 4 2 8 6 0 3 2 1 0 0 5

N

4 1 0 3 2 3 2 1 0 5

O

4 0.8

P

0.6

0.4

0.2

0.0

1950 Yellowfin equatorial Yellowfin tropical Yellowfin subtropical Yellowfin temperate 1965 1980 1995 800 600 400 200 0 30 20 10 40 30 20 10 0 0 2 0 6 4 10 8

More often than not community CPUE declines faster than abundance

q i q j



B i



t

 1 

r i

 1  

B i



t B K i i

 

B i



q EB i

   

i

0

q K i i

 2    

i K i i

2

q K i i i



i

2

q K i i

2  2  

i j q q K K i j i j B SS



K i i



CPUE SS



q K i i i



i



i r i q i K i K i



i

2 

i



i q r i q K i K i i

 

i

2

q K i i

2 

i

 

j



q i

2 

q j

2 

K K i j r i r j



q q j i

   Biomass declines faster than CPUE

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

0.04

A

Albacore (10°-30°S) 0.03

0.02

0.01

0.00

0.30

B

Yellowfin (10°-40°S, west of 160°E) 0.20

0.10

Is data consistent

0.00

0.05

C

Yellowfin (10°-40°S, 160°E-150°W) 0.04

0.03

0.02

0.01

0.00

4

D

Bigeye (Pacific) 3 2 1 Catchability higher in the early period to describe 0 rapid decline in CPUE 1950 1960 1970 1980 1990 2000

Fishery versus environment for yellowfin tuna in the EPO No fishing Fishing 1500 1000 500 0 75 77 79 81 83 85 87 89 Year 91 93 95 97 99 01 03

Fishery Impact on EPO bigeye tuna

1.0

0.8

Longline Floating object Small discards 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

1.6

1.4

1.2

1 0.8

0.6

0.4

0.2

0 1975 1980 1985 1990 Year 1995 Integrated stock assessement 2000 CPUE 2005

Estimate management quantities

(how useful they are?) 1.0

0.8

0.6

0.4

0.2

0.0

75 77 79 81 83 85 87 89 91 Year -- Aсo 93 95 97 99 01 03

Determine increase in yield by changing fishing methods: Yellowfin tuna in the EPO

Method All Floating Object Unassociated Dolphin associated longline MSY (`000 t) 285 194 243 320 386

Predict effects of management

800000 No closure Closure 600000 400000 200000 0 75 77 79 81 83 85 87 89 91 93 Year -- Aсo 95 97 99 01 03 05 07 09

Abundance of tunas in the Pacific Ocean

Integrated models

7,000,000 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,000 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 Yellowfin Bigeye Albacore 1 0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0 1940 1950 1960

Japanese longline CPUE

70 60 50 40 30 20 10 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 Yellowfin Bigeye Albacore 1970 1980 1990 2000 1.60E+06 1.40E+06 1.20E+06 1.00E+06 8.00E+05 6.00E+05 4.00E+05 2.00E+05 0.00E+00 1940 Estimated biomass Biomass - no fishing Biomass - no longline 1950 1960 1970 1980 1990 2000 2010 2010

Management of fish stocks

• Sustainable fisheries management is based on surplus production • Surplus production increases as the abundance falls towards B MSY • B MSY level is often much less than half the unexploited • B MSY 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