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Achieving Higher Economic Value under the Same Conversation Goal:

Tradeoff Analysis of the Eastern Pacific Ocean Tropical Tuna Fishery between Longline and Purse-seine Fishing

Jenny Sun1, Mark N. Maunder2, Minling Pan3, Alexandre Aires-da-Silva2, William H. Bayliff2,

and Guillermo A. Compeán2

1 Institute of Applied Economics, National Taiwan Ocean University

2 Inter-American Tropical Tuna Commission 3 Pacific Islands Fisheries Science Center, NOAA Fishery.

Open Access Fisheries Entry until collapse

Managed Fisheries – “Tragedy of the Commons”

Excessive investment Dangerous fishing Destructive fishing practices Short seasons Poor quality product Lobby for larger catch

Theory

Stocks decline Economic value is lost

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1950 1960 1970 1980 1990 2000

BBLLPSTROLOTH

0%

20%

40%

60%

80%

100%

1950 1960 1970 1980 1990 2000

BBLLPSTROLOTH

Fig. 5 World tuna catch by species and share (Source: FAO and RFMO databases)

BET YFT

Spawning biomass ratio (SBR)

• Under the allocation of effort in 2008, MSY for BET occurs at a spawning biomass level that is 19% of the unexploited level.

• The current IATTC recommends reducing both the longline and purse-seine fishing effort proportionally by 20.5% during 2009-2011.

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Landings by Species/Gear in the EPO

020406080

100120140

1979 1988 1997 2006

Thou

sand

s m

t PS LL

Fig. 2a Catches of BET

0

20

40

60

80

100

1993 1998 2003 2008

Thou

sand

s m

t PS_NOAPS_OBJPS_DEL

Fig. 2b BET by PS Gears

0

100

200

300

400

500

1979 1988 1997 2006

Thou

sand

s m

t PSLL

Fig. 3a Catches of YFT

0

100

200

300

400

500

1993 1998 2003 2008Th

ousa

nds

mt PS_NOA

PS_OBJPS_DEL

Fig. 3b YFT by PS Gears

BET YFT

BET YFT

SKJ

5

0

100

200

300

400

1979 1988 1997 2006

Thou

sand

s m

t PSOthers

Catches of Skipjack

0

100

200

300

400

1993 1998 2003 2008Th

ousa

nds

mt

PS_OBJPS_NOAPS_DEL

SKJ Landings by PS in the EPO

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Ex-vessel Prices in 2007 (US$/MT)

LL_YFT LL_BET PS_YFT PS_SKJ PS_BETPrice ($/MT) 7,858 9,576 1,710 1,425 1,568

0

5,000

10,000

Both yellowfin and bigeye tuna in EPO are caught at sizes too small to take full advantage of their individual growth and the higher price obtained for large fish in the sashimi market.

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Purse-seine vs Longline

Achieving higher revenue requires an understanding of both economic and biological tradeoffs among different management actions.

LL_YFT 2%

LL_BET 6%

PS_YFT 36% PS_SKJ

43%

PS_BET 13%

Landings (excluding discards) (Total: 480,562 MT)

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Landings & Values by Gear & Species in EPO

LL_YFT 5%

LL_BET 26%

PS_YFT 29%

PS_SKJ 30%

PS_BET 10%

Revenue (Total: US$ 1 Billion)

Three analyses are conducted to evaluate the economic and biological tradeoffs of different levels of purse-seine and longline fishing effort.

1. Evaluate the different combinations of effort that

could produce the target biomass level.

2. Simulate combinations of effort that optimize equilibrium (long-term) yield and economic value.

3. Measure the dynamic (short-term) effect of different combinations of effort.

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Objectives

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Biological model

The analyses are based on the IATTC’s stock assessments for bigeye (Aires-da-Silva and Maunder, 2010) and yellowfin tuna (Maunder and Aires-da-Silva, 2010).

No reliable assessment is available for skipjack tuna.

Therefore, changes in equilibrium yields for skipjack were assumed to be proportional to changes in purse-seine equilibrium yields for yellowfin tuna.

Methods

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It is assumed that if the catches of small bigeye and yellowfin were reduced, the gains to the biomass of those species due to growth would exceed the losses to it due to natural mortality.

This would increase the availability of large bigeye and yellowfin to the longline fishery, which, in turn, would increase the total catches of those species, provided there was sufficient fishing effort by longliners.

It is further assumed that bigeye and yellowfin are well mixed within the EPO, in which case reductions in the catches of small tunas anywhere in the EPO would be beneficial to longliners operating anywhere in the EPO.

Assumption

Economic value The economic value was simply calculated by summing

the ex-vessel prices multiplied by the total landings for each of the three species and each gear. In the dynamic calculations, the value is summed over all projected years.

Equilibrium value The stock assessment models for bigeye and yellowfin

tuna is used to calculate the SBR, catch, and economic value of the fisheries for different levels of longline and purse-seine fishing effort in a steady state. A large number of simulations in effort combinations are used to analyze the tradeoff.

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Methods

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Spawning Biomass Ratio (SBR)

Purse Seine Effort

LL E

ffort

Purse Seine Effort

LL E

ffort

Figure 1&2 Surface and contour plot of equilibrium bigeye and yellowfin tuna spawning biomass ratio (SBR) under different PS

and LL effort levels relative to effort levels in 2008

BET YFT

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Four Scenarios: SBR of BET

A) Standardized LL&PS Effort in 2008; (PS=1, LL=1) B) 20.5% equal proportional reduction in LL and PS, (PS=0.795, LL=0.795) C) Fixed LL effort and a 16.3% reduction in PS (PS=0.737, LL=1) D) Fixed PS effort and a 86.7%reduction in LL, (PS=1, LL=0.133)

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Equilibrium Catches and Values

Fig. 2a&3a Contour plot of BET steady-state catches and value

Figure 3 The Change in total landings values of the EPO

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-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0.5 1.0 1.5

0.5

1.0

1.5

Change in value (billions)

Purse seine effort

Lo

ng

lin

e e

ffo

rt

0

0.5

1

1.5

2

0 0.5 1 1.5 2

SBR=0.12SBR=0.19

A B

C

D

Changes in landings Value (Billion US$)

PS Effort

LL E

ffort

1% reduction in PS effort associated with floating objects (roughly 84 sets) would reduce the PS catch by

301 tons, allows a 1,170-ton

increase in the LL catch increase the total

revenue by $10.74 millionc of LL after compensating for the loss of catches by the PS.

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Retained Catches Revenue Fishery LL PS LL Changes PS Changes Total Changes Species (1,000 (1,000 to Case B to Case B to Case B Scenario* mt) mt) (mil. $) (mil. $) (mil. $) (mil. $) (mil. $) (mil. $)

All Tuna Case A 42 532 366 838 1203 Case B 49 514 436 Base 810 Base 1246 Base Case C 63 500 551 115 788 -22 1339 93 Case D 7 551 65 -371 869 59 934 -311

Table 1 LL and PS Landings and Value under BET SBR = 0.19

For the purse-seiners, there are $22 million loss, however there is a net gain of $94 million revenue in total. In addition, the purse-seine fleet would not have any costs of fishing so the benefit to them would be higher.

Tradeoff Under Target SBR of Bigeye Tuna One ton of BET not caught by the PS:

1. $1,540 loss in PS 2. $36,878 gain in LL revenue.

3. after providing $1,540 compensation to the loss of PS's BET landings value, 4. the total BET landings value would increase to $35,340.

1% reduction in PS effort associated with FOB (roughly 84 sets):

1.reduce the PS catch by 301 tons,

2.allows a 1,170-ton increase in the LL catch, and

3.increase the total revenue by $10.74 million after compensating for the loss of catches by the PS.

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0.1

0.2

0.3

2000 2005 2010 2015 2020

Spaw

ning

Bio

mas

s R

atio

(SB

R)

Case A (PS=1, LL=1)

Case B (PS=0.795, LL=0.795)

Case C (PS=0.737, LL=1)

Case D (PS=1, LL=0.133)

Targeted SBR

Dynamic projections of SBR of bigeye tuna

$58

Net Benefits: Case C vs. Case B

Reach the targeted SBRBET = 19%

Net Gain

= $93 million

$11

$57

$3 $8

$93

BET YFT

SKJ

Cast C vs. Case B Total

PS

LL

We have shown that the economic value of the resource is highly dependent on the allocation of effort between the LL and PS fisheries.

Management objectives differ among resource users, and there are a multitude of factors that need to be considered. 1). Property rights 2). Compensation 3). Bycatch compensation 4). Vessel buybacks

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Conclusion and Discussion

Gracias!