Question and Concepts
Model details
Indicator
Conclusion
An Indicator for Ecosystem Externalities in Fishing
Lars J. Ravn-Jonsen∗ , Ken Haste Andersen†
& Niels Vestergaard∗
∗ Department
of Environmental and Business Economics,
University of Southern Denmark, Esbjerg
† National Institute of Aquatic Resources,
Technical University of Denmark, Charlottenlund
NAAF, Ketchikan, May 19–22, 2015
Question and Concepts
Model details
Indicator
Question
What is the ecosystem externalities of fishing on forage fish?
What is the ecosystem externalities of fishing on piscivorous fish
(large fish)?
Conclusion
Ecosystem
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Harvest
Forage Fish
Fleet Harvest
Ecosystem
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
Ecosystem
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
Ecosystem
Change
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
Ecosystem
Change
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
Internal
change
Ecosystem
Change
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
Internal
change
Ecosystem
Continue
as usual
Large Fish
Fleet
Change
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
External
change
Internal
change
Ecosystem
Continue
as usual
Large Fish
Fleet
Change
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
External
change
Internal
change
Ecosystem
Continue
as usual
Large Fish
Fleet
State
Change
Forage Fish
Fleet
Large Fish
Fleet Harvest
Forage Fish
Fleet Harvest
Ecosystem
Large Fish
Fleet
Forage Fish
Fleet
Large Fish
Fleet Rent
Forage Fish
Fleet Rent
Internal
change
External
change
Ecosystem
Change
Large Fish
Fleet
Continue
as usual
Forage Fish
Fleet
Question and Concepts
Model details
Indicator
Ecological Model
Trait based community size spectrum model
Two dimensions:
Size (mass) of individual fish 0.001 g—100 kg
Asymptotic size 4 g—100 kg
Explicit links mortality—consumption—somatic growth
Conclusion
Question and Concepts
Model details
Indicator
Ecological Model
Trait based community size spectrum model
Two dimensions:
Size (mass) of individual fish 0.001 g—100 kg
Asymptotic size 4 g—100 kg
Explicit links mortality—consumption—somatic growth
Conclusion
Question and Concepts
Model details
Indicator
Ecological Model
Trait based community size spectrum model
Two dimensions:
Size (mass) of individual fish 0.001 g—100 kg
Asymptotic size 4 g—100 kg
Explicit links mortality—consumption—somatic growth
Conclusion
Question and Concepts
Model details
Economic Model
Two fleets, knife edge wrt. species
Price
Increasing price wrt size for Large fish
Flat price for Forage fish
Indicator
Conclusion
Question and Concepts
Model details
Economic Model
Two fleets, knife edge wrt. species
Price
Increasing price wrt size for Large fish
Flat price for Forage fish
Indicator
Conclusion
Method
A marginal change of forage fleet’s fishery:
-10
-5
e year-1
0
Change Rent
0.0
0.1
ton year-1
Change Harvest
0.2
Change in forage fish’s fishing mortality
0
5
Year
10
15
0.1
0.0
ton year-1
Change Harvest
0.2
Change in forage fish’s fishing mortality
0
-5
∆Vl = −255.70 e
-10
e year-1
Change Rent
∆Vf = 16.10 e
0
5
10
Year
15
0.1
∆Yf = 3.569 ton
0.0
ton year-1
Change Harvest
0.2
Change in forage fish’s fishing mortality
0
-5
∆Vl = −255.70 e
-10
e year-1
Change Rent
∆Vf = 16.10 e
0
5
10
Year
15
0.1
∆Yf = 3.569 ton
Bf/f = 4.51 e ton-1
∆Vl = −255.70 e
Bl/f = −71.63 e ton-1
-5
0
∆Vf = 16.10 e
-10
e year-1
Change Rent
0.0
ton year-1
Change Harvest
0.2
Change in forage fish’s fishing mortality
0
5
10
Year
15
0.1
∆Yl = 3.544 ton
0.0
ton year-1
Change Harvest
0.2
Change in large fish’s fishing mortality
0
-50
Bl/l = −1 093.01 e ton-1
∆Vl = −3 873.64 euro
-100
e year-1
Change Rent
Bf/l = −3.31 e ton-1
∆Vf = −11.73 euro
0
5
10
Year
15
Question and Concepts
Model details
Indicator
Net Benefit Indicator
Present value of rent
∞
Z
Vj ≡
πj (t) e−ρt dt
0
Present value of harvest
Z
Yi ≡
∞
yi (t) e−ρt dt
0
Net Benefit Indicator
Bj/i ≡
∂Vj
∂Yi
Conclusion
Question and Concepts
Model details
Indicator
Net Benefit Indicator
Present use of the North Sea
With respect to
Forage fish fleet
Internal Benefit
External Benefit
Total Benefit
4.5 e ton-1
-71.6 e ton-1
-67.1 e ton-1
Large fish fleet
-1 093 e ton-1
-3 e ton-1
-1 096 e ton-1
Conclusion
0.0
0.2
0.4
0.6
0.8
1.0
Large Fish Harvest 106 ton year-1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Forage Fish Harvest 106 ton year-1
1.4
Forage Fish Fishery
Internal Benefit
1.4
-30
-20
1.2
0
1.0
10
0.6
0.8
20
0.2
0.4
20
30
40
40
0.0
Forage Fish Harvest 106 ton year-1
-10
-10
0.0
0.2
0.4
0.6
0.8
1.0
Large Fish Harvest 106 ton year-1
Forage Fish Fishery
Internal Benefit
1.4
1.4
-30
-20
A
0
A
1.2
1.2
-150
1.0
1.0
10
-100
0.8
0.8
20
0.6
0.6
50 0
0.4
0.4
20
10
0
-50
30
40
0.4
0.6
0.2
0
0.2
0.0
0
40
0.0
50
0.2
0
0
0.0
Forage Fish Harvest 106 ton year-1
-10
-10
External Benefit
0.8
1.0
0.0
Large Fish Harvest
0.2
106
0.4
0.6
ton year-1
0.8
1.0
1.2
Large Fish Fishery
External Benefit
Internal Benefit
1.4
8
1.2
-2
00
0
10
0.8
1.0
00
-1
2
4
-8
50
0
-10
2
1.0
-10
0.8
6
4
1.2
A
-12
0.6
0.6
-6
0.4
8
0.4
-4
0.0
0.2
0.4
0.6
0.8
1.0
0.0
Large Fish Harvest
0.2
106
0.4
0.2
0.0
0
-500
0
6
0.2
-2
0.0
Forage Fish Harvest 106 ton year-1
500
1000
1500
1.4
-14
A
0.6
ton year-1
0.8
1.0
1.2
Marginal Net Benefit
A
0.8
0
50
-50
0
0.8
-100
-1
-2
50
00
0
0
-10
1.0
00
-150
0
B
B
0.4
150
0.2
0.4
0.2
0.6
0.6
10
0
150
0
0.2
0.4
0.6
0.8
1.0
0.0
Large Fish Harvest
0.2
106
0.4
0.0
0 0
-500
0
0.0
0
20
0.0
1.0
1.2
500
1.2
1.4
-200
A
1000
Forage Fish Harvest 106 ton year-1
Wrt. Large Fish
1500
1.4
Wrt. Forage Fish
0.6
ton year-1
0.8
1.0
1.2
Question and Concepts
Model details
Indicator
Conclusion
Conclusion
Forage fish fishery have a notable economic impact on large
fish fishery. Not the other way around.
Present management of the North See not far from the right
balance; but present explotion is to high.
Question and Concepts
Model details
Indicator
Conclusion
Conclusion
Forage fish fishery have a notable economic impact on large
fish fishery. Not the other way around.
Present management of the North See not far from the right
balance; but present explotion is to high.
Community size spectrum model
zoo
pla
nk
ton
etc
.
foo
d
N
growth
size
0
Pristine system
10
-1
10
-2
10
-3
Biomass density
10
-4
10
-5
10
-6
10
-7
10
-8
10
-9
10
10
-10
0.1 g
10 g
1 kg
Weight
100 kg
Andersen & Pedersen (2010)
0
10
Example: fishing large fish
-1
10
-2
10
-3
Biomass density
10
-4
10
Fishing
-5
10
-6
10
-7
10
-8
10
-9
10
10
-10
0.1 g
10 g
Weight
1 kg
100 kg
Andersen & Pedersen, Proc. Roy.Soc. B (2010)