The Implications of Incomplete and Imperfect Information for Multinational Management
of Transboundary Marine Fisheries: A Cooperative Research Project
Robert McKelvey – U. Montana
:
OVERVIEW
The Project: Setting and Program
Harvested marine fish stocks have been depleted worldwide.
• The Culprit: Common Harvest of a breeding fish stock by non-cooperating fleets-The Tragedy of the Common
• The Remedy: Central management by a governmental regulatory authority, to
restrain and allocate harvests among fleets.
• Complications:
Transboundary fish stocks, which migrate across zones of national authority,
requiring multilateral cooperative management.
Stochastic stock demographics, due to oceanic environmental variability
(e.g. El Nino episodes.)
Inability to predict environmental regime shifts accurately, and in a timely way, so
as to make current harvesting decisions optimally.
***
• The program: Examine alternative management institutions through case studies
and game-theoretic modeling.
Kathleen Miller – National Center for Atmospheric Research : Peter Golubtsov – Moscow State University, Russia
SPLIT STREAM MODEL RESULTS
APPLICATION: MULTINATIONAL TUNA MANAGEMENT
EEZ’s in the WCPO
Tuna Fisheries Worldwide: A Comparative Study
The Dynamic Imperfect Information Split Stream
Harvesting Model
• Species of tuna are found is all of the world’s oceans, in a wide variety of
oceanographic, ecological, socioeconomic, and political circumstances. The goal
here is to understand the implications of these differing conditions.
Ra = q R
S
• All tuna stocks are highly migratory, and thus their ranges may intersect the EEZs of
many coastal nations. Furthermore, oceanic climates are often quite variable, so
that the sites of high concentrations of a tuna stock may move great distances from
year to year. Hence fish concentrations within any particular EEZ may fluctuate
substantially.
Spawn
R = F(S,b)
Sa
S+
Sa + Sb
R
Harvest Hb
Sb = Rb - Hb
Rb = (1-q) R
q
b
Pa
Harvest Ha
Sa = Ra - Ha
Sb
n = (b,q)
Pb
Hb = Pb(S,xb).
Policy: Harvest Ha = Pa(S,xa),


ca
dx
Pa = pHa - Ca ( Ra , Ha ) =   p qa a ( x) 
Sa 
Ra
• Tuna are valuable market fish, and while some high-value species have been overharvested, most stocks are not yet severely depleted. Thus, fishing fleets from
many distant-water nations are attracted to all major tuna fisheries.
Annual Payoff:
p - landing price, qa – catchability,
•
• These circumstances complicate cooperative management, since there are a great
many stakeholders, with differing rights and playing differing roles in the fishery.
•
Pacific Tuna Catch and the El Nino 3 Index
1995-1998
• The strategic model is designed to explore the impact of all these circumstances on
effective fishery management, and the interrelations among the stake-holders.
Global Tuna Fisheries are Big Business
The Stochastic Imperfect Information
Split-stream Game
90000
4
80000
3.5
- schooling density:
Both the stock-recruitment parameter b and the stock-split parameter q are random and
imperfectly observed.
Each fleet’s objective is to maximize the discounted sum of its annual payoffs to the time
horizon T.
Influence of harvesting cost/price ratio
for different knowledge structures.
Symmetric game.
3
70000
a
b
2.5
60000
Highly Migratory Species: Export Value (Nominal)
a (x )
Yellowfin Tuna
Swordfish
Southern Bluefin Tuna
Skipjack
Northern Bluefin Tuna
Marlins
Bigeye Tuna
Albacore
2,500,000
2,000,000
1,500,000
1,000,000
• Each fleet chooses its harvest policy to maximize the expected discounted sum of
annual net payoffs over time, in response to the policy of its competitor. Thus it
harvests to optimize the balance of immediate net return and its expected share of
anticipated future returns.
• The model demonstrates that, in non-cooperative harvesting, enhancing the
quality of the fleets’ information may actually be destructive to both—thus
contradicting the maxim that information transparency is always advantageous.
• (Details on the far-right panel.)
• All of these stake-holding countries are members of the RFMC. The Commission
makes long term policy for the fishery, gradually lowering the overcapacity of the
fleets and thereby raising the brood-stock level for sustainability and profitability. It
does this by negotiating annually the distribution of harvest capacity among the fleets
and/or vessel days of harvest among the coastal states.
• With these regulatory rules, it sets up annually a sequence of single-season
competitive sub-games among the fleets and coastal states. Thus each coastal state
sets its harvest-access royalties and allocates it’s vessel-days of harvest among the
fleets, and each fleet allocates its vessel distribution among coastal sites.
• The Tropical-Pacific tuna case, displayed on the central panel, illustrates the
management issues to be addressed through this modeling analysis.
(Currently the strategic model is being fine-tuned.)
20000
0
10000
Cost / price
Knowledge
structure:
98
19
98
19
98
98
98
97
97
97
97
97
97
96
98
19
19
19
19
19
19
19
19
19
19
19
96
19
96
96
96
96
19
19
19
95
95
95
95
95
19
19
19
19
19
95
East Skipjack catch was landed
east of the international date
line and west of 120W. The
west skipjack catch was landed
east of the international date
line and west of 130E.
-1
19
20
00
19
98
19
96
19
94
19
92
19
90
19
88
19
86
19
84
19
82
19
80
a
b
-0.5
0
19
78
West Skipjack Purse Seine
El Nino 3 Index
40000
0.5
500,000
19
76
1.5
30000
Year
Years
Effects of an El Niño
Harvest of tuna by zones (1950-1997)
Cost / price
Cur = full current knowledge, both fleets
Min = minimum current knowledge (only probability distribution) both
Cur-Min a = outcome for fleet a when it has full knowledge and fleet b has
only minimal knowledge
Cur-Min b = corresponding outcome for player b
All alternatives competitive unless marked Coop = cooperative
Note Information Inversions i.e. enhancing information yields inferior outcomes
Application to small schooling pelagics
Indian Ocean East
Indian Ocean West
Pacific Center West
Pacific South
Pacific North West
Pacific Center East
Atlantic Center East
Atlantic North
Others
(e.g. sardines-anchovies)
Coop
Coop
Coop
Coop
Multilateral Management of Highly Migratory
Stocks through a Regional Fisheries
Management Commission (RFMC)
• The RFMC Strategic Game Model assumes M countries with fleets and N coastal
countries whose extended economic zones (EEZs) intersect the range of a highly
migratory harvested fish-stock. Here M,N may be large, and while they may
intersect, usually differ.
East Skipjack Purse Seine
1
0
• The new generation grows to maturity and once again splits into sub-streams.
The growth and subsequent split processes both are stochastic, and imperfectly
observed by the fleets. The process repeats annually.
50000
19
• A migratory stock splits into two sub-streams, each accessible to only one of two
competing harvesting fleets. After harvest, the residual sub-streams reunite to form
the brood-stock for the subsequent generation.
$
Thousand
Thousands US
of USD
• A generic game, adjustable to describe various species-types, e.g. salmon,
migrating along coastlines and small schooling species (sardines, anchovies) which
are easily over-harvested and subject to large annual demographic variations.
3,000,000
Catch in MT
2
Cost / price
1998, Nov
Note dominance of Pacific Center Region (i.e. Tropical Pacific) and the dominance of
Pacific Center West over Pacific Center East
Tropical Tuna in the Western Pacific:
Specific Circumstances
• Stock ranges are huge, and contain an unusually large number of coastal states,
mainly island states, within the stocks’ range. Further most tuna are harvested
within their EEZs rather than on the high seas.
• However stock concentrations move about from year to year, across vast distances,
following the loci of food concentrations, as determined by ocean currents and
surface temperatures.
Management issues in the
Tropical Western Pacific
• The new Western and Central Pacific Tuna Commission treaty came into effect in
late 2004, with substantive debate in 2005. Unusually, the island states have been
working together closely, especially the 8 “haves” (parties to the Nauru Agreement”).
Their interests deviate from those of the 7 “sometimes haves” at the opposite pole of
the El Nino cycle, plus Australia and New Zealand.
•
Specifies symmetry in information but erratic temporal changes in stock growth and distribution.
(Figures show mean values over time)
•
Usually the growth rate is high, and stock-split favors the a-site, but rarely the growth rate is small,
with stock almost exclusively at b-site. The tight schooling favors over-harvesting.
•
The cooperative solution based on bargaining which is responsive to the asymmetries in the fleets’
competitive strengths.
Varying the Fleets’ Risk Attitude
• The harvesting nations do not cooperate, but instead compete with one another
for access to the island state’s EEZs. Nevertheless, they retain the lion’s share of
the returns from harvest.
• These tuna stocks are the largest and most valuable in the world, attracting many
distant-water fleets (DWFs) worldwide. Few coastal states have substantial fleets of
their own, and the DWFs take 85% of the catch.
• The island states hope that, by further cooperation, they will achieve a higher
share of harvest returns. To this end, they insisted on a voting system within the
RFMC which gives them, collectively, a veto over its decisions. They also have
insisted that the regulatory controls allocate vessel-days of harvest to them, rather
than allocating harvesting capacity to the fleets.
• Over time, stock-harvest has expanded dramatically, with total fleet size becoming
excessive, so that stocks are increasingly vulnerable to over-harvest.
•Our RFMC model is designed to examine the effectiveness, and societal
implications of these circumstances
• Risk attitude: risk averse for d < 1, risk neutral at d = 1; risk accepting for d > 1
• Note small inversion on left (where fleets highly risk averse), but not on right (where fleets mildly risk
averse or mildly risk accepting)
• As risk aversion increases (i.e. d → 0) then competitive outcomes merge with cooperative outcomes.