Shared migratory stocks and
the NEA mackerel
Rögnvaldur Hannesson
Norwegian School of Economics
Bergen
A sea change: the 200 mile zone
• Established national ownership to fish stocks
• Migratory stocks: shared ownership
• Limited number of countries with legitimate interest
• High seas fishing: number of claimants indefinite
• Destroys incentives for better management
• Might invite newcomers
Management of shared stocks in the NE
Atlantic
• Successful for
• NE Arctic cod
• Demersal stocks shared betwen EU & Norway
• Periodic breakdowns for
• North Sea herring
• NSS herring
• Mackerel
• Stocks with breakdowns are migratory with (at times) radical changes
in distribution and migration
Game theory and shared fish stocks
• Studies interactions between players where the outcome for Player i
depends on actions by Player j
• Reasonable to study best reply of i to j’s action and seek a consistent
solution
• Leads to extremely agressive behavior
• Extinction of stocks not unlikely
• Player i leaves one fish behind in expectation to get 1+g next year
• But with N>1 players, he gets only (1+g)/N
• Viable solution only if one dominant player
Game theory (cont’d)
• But would the players willingly destroy the fishery?
• Alternative approach:
• Assume cooperation
• Defection would lead to retaliation
• If retaliation makes defection unprofitable, cooperation can be
maintained by an implicit threat
Migrations of mackerel
Migrations of mackerel (cont’d)
Economic zones in the
Northeast Atlantic
The banana-shaped on is
high seas
Norway has Spitsbergen and
Jan Mayen
Since 2007 a substantial migration to Iceland
Catches (shares)
Stock
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
6
Mill. tonnes
5
4
3
2
1
EU
Norway
Faeroe Islands
Russia/Soviet
Iceland
2011
2008
2005
2002
1999
1996
1993
1990
1987
1984
1981
1978
1975
1972
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
0
Consequences
• Iceland set its own quota > EU & Norway willing to accept
• Faeroe Islands withdrew from agreement with Norway and
EU
• No agreement on mackerel quota until 2014 when Faeroe
Islands again joined, but Iceland still outside
• What does game theory tell us the parties will do when
acting on their own?
• Their fishing seems moderate by comparison
Game scenarios
• Full cooperation as benchmark
• Iceland deviates from cooperation (chooses F in its own zone)
• Faeroe Islands also deviate (adjusts its F to the others’ and Iceland
readjusts its own to the new situation, etc., until no further
adjustments by Iceland and Faeroe Islands pay off)
• Norway also deviates, with mutual readjustments of Icelandic,
Faeroese and Norwegian F.
• All deviate (including fishery on the high seas)
Outcome with random (left) verus stockdependent (right) migrations
350
300
300
250
250
200
Cooperation
200
Iceland deviates
Cooperation
Icel deviates
150
Icel.&Faeroes dev.
150
All deviate
Icel.&Faeroes dev.
All deviate
100
100
50
50
0
0
EU
Norway
Faeroes
Iceland
Int
EU
Norway
Faeroes
Iceland
Int
The stock has grown since 2007.
Million tonnes
In reality, the parties have
followed a relatively cautious
strategy despite all rhetoric.
6
0.35
5
0.3
4
0.25
0.2
3
0.15
2
0.1
1
0.05
0
0
The exploitation rate is moderate (well below msy-level).
Mutually consistent fishing mortalities in the absence of
coordination would mean immediate fishing of 2-3 million
tonnes and possibly a total destruction of the fishery.
Stock
Catches
C/S
Conclusion
• Do we have a degree of implicit cooperation because of
mutually assured destruction otherwise?
• Just like mutually assured destruction kept the cold war
cold?