Transcript Ecological and Economic Considerations in the Conservation

Ecological and Economic Considerations
in Management of the U.S. Pacific sardine
Fishery
Samuel F. Herrick Jr
NOAA Fisheries
Southwest Fisheries Science Center
1
• Report on ongoing work in collaboration with Rognvaldur
Hannesson, Norwegian School of Economics and
Business Administration and John Field, NOAA
Fisheries, Southwest Fisheries Science Center
• Publications:
– Hannesson, R., S. Herrick and J. Field. 2009. Ecological and
economic considerations in the conservation and management
of the Pacific sardine (Sardinops sagax). Ca. J. Fish. Aquat. Sci.
66: 859-868.
– Hannesson, R. and S.F. Herrick Jr. 2010. The value of Pacific
sardine as forage fish. Marine Policy 34: 935–942
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• Account for the total value sardines provide in
terms of their function in the California Current
Ecosystem
• Basically a matter of balancing the economic
benefits from harvesting sardines against the
economic benefits from leaving sardines in the
water
• At this point
– Present the analytical framework for evaluating
the tradeoffs
– Show what has been done with existing data
– Draw some conclusions
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Uses of the Pacific sardine resource in the
California Current Ecosystem
Direct use
as harvest
Other ?
- Human Consumption
- Bait: commercial, recreational
- Aquafeed: fresh/frozen, meal/oil
Sardine Ecosystem Sevices in
the California Current
Ecosystem
Forage for ecologically
important species: gulls, orcas,
toothed whales, sea lions, fur
seals, baleen whales
Indirect Use
as forage
Forage for commercial
predators: salmon,
albacore, coastal sharks,
whiting
Forage for recreational
predators:salmon,
albacore, coastal sharks
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• Summarize as follows
$
Marginal Net Benefit
from Harvest
Marginal Net Benefit
from Forage
$*
H'
Quantity of Harvest
Quantity of Forage
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• The analytical framework to address this issue:
– Suppose that the catch of sardines is reduced by S
– The value of this incremental sardine stock as forage would be
given by
(1)

S
P
ia
ib
i
i
• Where:
– i indexes species that feed on the sardine,
 – Pi is the price (net of fishing costs) of species i,
– ai is the share of the incremental sardine stock that is eaten by
species i, and

– bi is the transfer efficiency, the fraction converted to predator
biomass
– If the sardine is more valuable as commercial landings than as
forage fish the following must hold:
(2)
P

S


SP
b
a

s
i
i
i
i
• Where Ps is the market price of sardine, net of fishing costs.
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• The predators of the sardine are not all
commercially valuable
– Dividing the right hand side of (2) into commercial and noncommercial predators, and canceling the S on both sides, gives

P
b
a

vb
a


s
iii
j
j
(3) P
i
j
Where:
• v is a non-market average value per unit of biomass growth of noncommercial predators attributable to sardine consumption
• i is an index for the commercially valuable species
• j is an index for the non-commercial species
The right hand side is the value of the increase in the amount of
sardine predators provided by a unit increase in the sardine stock
– The Pi’s and v have to be large enough to reverse the inequality
for sardine to be more valuable as forage species
• Calculate the critical value of v, that turns (3) into
an equality
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• We used the data published in Field et al. (2006)
to identify sardine predators and to calculate
values for the parameters a and b for each
predator k
• Prices, P, are real average exvessel prices over
the 1998-2006 period
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•
Critical value of v under different pricing scenarios:
1. Base case, v = $6.78/kg
•
The annual net benefit of a one kg increase in the biomass
of all non-commercial predators induced by the incremental
supply of sardines as forage.
2. Five-fold increase in the price of sharks to reflect
their potential recreational value: from $1.73 to
$8.47/kg, v = $0.0/kg
•
The increase in the value of sharks would suffice to make
the sardine more valuable as forage.
3. 20% increase in salmon and albacore prices with a
20% decrease in price of sardines, v < $0.0/kg
•
These price differences are within the range of prices for
the 1998-2002 period, indicating that the value of sardine as
forage is quite sensitive to realistic changes in its own price
and those of commercially relevant predators.
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•
Critical value of v under different
biological/ecological parameter scenarios:
1. Increase the transfer efficiency, b, to .02 for salmon,
albacore and coastal sharks, v = $3.81/kg
•
A higher transfer efficiency by itself would not make
sardine sufficiently valuable as forage for the commercial
predators alone at the assumed baseline biological
parameter values and exvessel prices.
2. Increase the share of sardines in the diets of
salmon, albacore and coastal sharks by 40%,
v < $0.0
•
If increased consumption of sardines by commercial
predators is realistic, it would imply that the sardine stock is
more valuable as forage fish than as commercial catches.
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• Conclusions:
– The total value of forage species is derived from their commercial
harvest value and their value as prey for commercially, recreationally
and ecologically important stocks
– To quantitatively model this situation requires a great deal of detailed
economic and ecological data
• On the economic side
– Market values
» the net benefits of harvesting sardines and their commercial predators rely
on market prices and costs associated with their harvest
– Non-market values
» recreational catches are not sold
» ecologically important species are public goods
• On the ecological side
– Identify sardine predators
» the proportion of the sardine biomass that is consumed by each predator
» transfer efficiencies
– The relationships that have been modeled here are likely to be nonlinear and dependent on the relative abundance of sardines and their
predators
– Management strategy likely to vary with the composition of the forage
base
• Composition of forage base determined by environment
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Pacific sardine, Pacific mackerel and Northern anchovy biomass estimates (mt) and NE Pacific Ocean cumulative
sea surface temperature, 1932-2009.
6,000,000
12.0000
5,000,000
8.0000
Mackerel Biomass
6.0000
Cumulative SST
Anomaly
4.0000
2.0000
3,000,000
0.0000
-2.0000
2,000,000
-4.0000
-6.0000
1,000,000
-8.0000
2008
2004
2000
1996
1992
1988
1984
1980
Year
1976
1972
1968
1964
1960
1956
1952
1948
1944
1940
-10.0000
1936
0
1932
Biomass (mt)
4,000,000
Anchovy Biomass
Cumulative Anomaly
10.0000
Sardine Biomass
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• Species by trophic level and trophic category.
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Regression of the average trophic level of California commercial fishery landings
on forage stock biomass, 1932-2009.
Stock
Coefficient
P-value|
N
P. sardine
-1.52e-07
0.000
78
P. mackerel
2.04e-07
0.030
78
N. anchovy
2.08e-07
0.022
46
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• Ecological data:
– Field, J.C., R.C. Francis and K. Aydin. 2006. Top-down modeling
and bottom-up dynamics: Linking a fisheries-based ecosystem
model with climate hypotheses in the California Current.
Progress in Oceanography 68:238-270.
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Predators, ecological parameters, shares of sardine eaten by predators
(a), and prices of sardine and its predators.
Predator
d
S/km2
g
b
a
Price
($/kg)
Salmon
0.010
0.367 0.930 0.1600
0.13168
3.50
Albacore
0.050
0.014 0.360 0.0500
0.03111
1.76
Coastal sharks
0.050
0.050 0.180 0.0600
0.04630
1.73
Common murres
0.001
0.009 0.100 0.0008
0.00694
Gulls
0.001
0.002 0.120 0.0010
0.00148
Orcas
0.005
0.001 0.020 0.0020
0.00031
Toothed whales
0.050
0.052 0.070 0.0025
0.44939
Sea lions
0.010
0.012 0.074 0.0050
0.01096
Fur seals
0.010
0.006 0.091 0.0025
0.01348
Baleen whales
0.090
0.075 0.037 0.0050
0.30834
Sardine
0.663
0.10