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Aquaculture: Externalities and Policy Options
May 23, 2022
Frank Asche
School of Forest, Fisheries and Geomatics Science and Food Systems Institute
University of Florida
PO Box 110570; Gainesville, FL 32611, USA
Frank.Asche@ufl.edu
and
Department of Safety, Economics and Planning
University of Stavanger
4036, Stavanger, Norway
Håkan Eggert
Department of Economics
University of Gothenburg
PO Box 640; SE 405 30, Sweden
Hakan.Eggert@gu.se
Atle Oglend
Department of Safety, Economics and Planning
University of Stavanger
4036 Stavanger, Norway
atle.oglend@uis.no
Cathy A. Roheim
Department of Agricultural Economics and Rural Sociology
University of Idaho
Moscow, ID 83844, USA
croheim@uidaho.edu
Martin D. Smith
Nicholas School of the Environment and Department of Economics
Duke University
Box 90328; Durham, NC 27708, USA
martin.smith@duke.edu (corresponding)
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Abstract
Global seafood supply is increasing and seafood prices are stable, despite the plateauing of global wild-
caught fishery harvests and reports of collapsing fish stocks. This trend is largely due to rapid growth in
aquaculture (farmed seafood), which now accounts for roughly half of global seafood supply. Although
aquaculture is a key contributor to food security, fish farming interacts closely with the surrounding
ecosystem, and its rapid global growth raises many environmental concerns. Potential negative
externalities include decreases in water quality, disease spillovers, genetic interactions between wild and
domesticated fish, overuse of antibiotics, and pressures on fish stocks from reliance on wild-caught fish
for feed. We show that the environmental externalities of aquaculture can be positive or negative; some
externalities are not true externalities because firms have incentives to internalize them; some perceived
externalities do not exist; and the remaining externalities can be addressed primarily through spatial
management. Because outcomes are strongly influenced by the management of spatial issues such as
siting of production facilities, management challenges include both commons and anti-commons
problems. We conclude that management should focus on spatial approaches, adaptation to climate
change, and facilitating technological innovation to address externalities and encourage sustainable
development of the aquaculture sector.
JEL Codes: Q22, Q28, Q55
Keywords: fish farming; innovation; common-pool resources (CPRs); anti-commons; technical change;
climate change; spatial management
Acknowledgement Footnote: Håkan Eggert acknowledges financial support from Sida through the
Environment for Development Initiative.
INTRODUCTION
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Seafood plays an important role in global food security, accounting for 17% of global animal
protein consumption (FAO, 2020) and providing critical micro- and macronutrients to support human
health. It is a major food source for many low-income populations that have few alternatives. The seafood
sector also provides employment in harvesting, fish farming, processing, distribution, and food retailing.
For decades, global seafood demand has grown in response to increasing populations and rising incomes
(Kobayashi et al. 2015; Kidane and Brækkan 2021). Growth in seafood supply has been facilitated by
technological change, institutional reform, and globalization, with nearly all growth since 1990 coming
from aquaculture.
Aquaculture is the farming of fish, shellfish, and other aquatic invertebrates, as well as aquatic
plants such as seaweed, in marine, freshwater, and estuarine aquatic environments. Aquaculture as a
production method is often contrasted with wild-caught (or capture) fisheries.
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Aquaculture accounts for approximately half of global seafood consumption and, with an average
annual growth rate of 8% since 1970, it has been the fastest growing food sector for the past five decades
(FAO, 2020). Aquaculture and chicken are the only animal protein sources whose production shares are
increasing, and aquaculture’s current global production of 82 million metric tons makes it a larger source
of animal protein globally than either beef or lamb (FAO, 2020). Aquaculture production has continued to
grow at a high rate despite having matured to the point that it is a significant contributor to the global
food system (Garlock et al. 2020).
Aquaculture includes a wide range of species and production methods and is practiced on all
continents except Antarctica. Salmon and shrimp contribute the most value to the global seafood trade.
Although salmon and shrimp are produced mainly in high- and middle-income countries, more than 95%
of aquaculture production by volume takes place in developing countries (Garlock et al. 2020). In
developing countries, 34% of aquaculture by volume is carp production, a low-valued fish consumed
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Throughout this article, we use “wild-caught” and “capture” interchangeably.
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almost exclusively within the producing countries (FAO, 2020). This suggests that in many countries,
aquaculture production makes an important contribution to food security (Belton et al. 2018). However,
a number of environmental challenges are associated with the rapid expansion of aquaculture, with new
technologies engaging the ecosystem in ways that result in new externalities. Thus, it is important to ask
whether aquaculture's contributions to economic value and global food security will continue to grow and
whether the aquaculture sector will develop sustainably.
This article, which is part of a symposium on The Future of Seafood,
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addresses these questions.
The future of aquaculture will depend critically on the extent of key externalities, how governance evolves
to address these externalities, and the extent to which markets and other institutions provide incentives
for technological innovation. Governance in this context refers to natural resource management and
environmental regulation by governments as well as private sector initiatives and efforts by non-
governmental organizations that seek to influence consumer behavior, supply chain management, and
production practices. Potential market failures in aquaculture include natural resource scarcities that
stem from the problem of the commons and a number of environmental externalities. In order to consider
appropriate policies and governance structures, we distinguish between externalities that are
endogenous (determined within the sector) and externalities that are exogenous (determined outside the
sector). For example, disease in aquaculture is endogenous because one aquaculture firm’s failure to
manage disease risk affects other firms’ location and production possibilities. By contrast, climate change
is largely exogenous to the aquaculture sector because firms must accept it as given in their production
decisions.
The remainder of the article is organized as follows. First, we provide an overview of aquaculture’s
role in the global food system and the sector’s patterns of growth. We then examine the most significant
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The other articles are by Abbott et al. (2022), who discuss the economics of recreational fisheries, Kroetz et al.
(2022), who focus on the future of wild-caught fisheries, and Cojocaru et al. (2022), who provide a synthesis of the
other three articles in the symposium and discuss key issues concerning the global seafood system.
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externalities associated with the aquaculture industry. Although freshwater species dominate global
aquaculture production totals, we focus on examples from the shrimp and salmon industries because they
provide important insights about aquaculture, externalities, and the likely future of the sector. We
conclude with a summary and policy recommendations aimed at addressing externalities and facilitating
continued innovation and sustainable growth in the aquaculture sector.
AQUACULTURE AND THE GLOBAL FOOD SYSTEM
In this section, we describe aquaculture’s role in the seafood system and contextualize seafood in the
broader food system. We first explain why seafood prices have been stable despite the fact that many
fisheries are overfished and there has been substantial degradation of marine ecosystems. We then
discuss factors contributing to aquaculture growth.
Why have Seafood Prices been Stable?
Given the widespread claims of degraded aquatic ecosystems and global patterns of overfishing, it is
important to understand why real prices for seafood have not increased. Indeed, as shown in Figure 1,
the global quantity of wild-caught seafood supplied has been stagnant for decades, while global demand
for seafood has grown dramatically as income and population have grown (Kobayashi et al. 2015; Asche
and Smith 2018). Because capture fisheries are exhaustible, there are absolute limits on how much
seafood an individual fishery can produce in the long run. Thus, the fact that the capture fishery supply is
stagnant should not be surprising. In theory, the long-run supply curve for individual capture fisheries is
backward-bending under open access (that is, when users of the exhaustible resource cannot be
excluded), whereas under an effective governance regime that aims to achieve maximum sustainable
yield, the long-run supply is hockey-stick shaped (a backwards ‘L’), which means quantity supplied will
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initially increase as price increases and then become constant at higher prices (Anderson 1985;
Valderrama and Anderson 2010; Li et al. 2021).
To illustrate the implications of these features of seafood markets, we present stylized supply and
demand curves for capture seafood. As shown in Figure 2, SOA represents the long-run supply curve
associated with an open-access fishery, while SMSY represents the supply curve associated with a well-
managed fishery that maintains the fish stock at the level associated with maximum sustainable yield
(MSY). Under open access, the point in time at which individual fisheries reach the backward-bending rate
(that is, where supply (SOA) decreases as price increases) varies. As long as under-harvested fish stocks
remain, rising prices will create incentives to exploit these stocks and add them into aggregate supply.
However, the plateau in the quantity of wild-caught seafood supplied in the late 1980s suggests that
fisheries are now close to being fully exploited globally. As shown in Figure 2, when these long-run supply
curves are overlayed with demand growth, seafood prices should, in theory, increase (when the demand
schedule shifts from D0 to D1). However, as shown in Figure 1, real prices of seafood have not increased.
Indeed, at various times, real seafood prices have actually declined, leading to a net effect of almost no
change in real prices for three decades.
Why have prices not increased? The simple solution to this puzzle is aquaculture. That is, global
seafood prices have not increased because aquaculture production has grown substantially during the
period of stagnating capture fishery production (see Figure 3), which means that total seafood supply has
actually grown at a rate that is similar to the growth in demand. Indeed, because for most seafood
consumers, seafood from capture fisheries and aquaculture are close substitutes, their price
determination processes are similar. There is strong empirical evidence for this finding in major seafood
markets like salmon, shrimp, and whitefish (e.g., cod, tilapia, catfish) (Asche, Bremnes and Wessells 1999;
Asche et al 2012; Bronnmann et al. 2016).
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The trends in Figures 1 and 3 suggest that the conceptual demand and supply model that best fits
the evidence has neither a vertical nor a backward-bending supply curve in the long run. Rather, long-run
seafood supply consists of seafood from both capture fisheries and aquaculture, with aquaculture making
the aggregate supply curve slope upward (Anderson, 1985). In Figure 4, we combine the supply curves
from open-access and well-managed capture (wild) fisheries into a single backward-bending supply curve
(S0,W); that is, we horizontally sum the two supply curves from Figure 2 to create S0,W. To create the total
supply curve (S0,Total), we add (horizontally sum) the supply from aquaculture (S0,A) to the supply curve
from wild (S0,W). Figure 4 suggests that when fish farming was first emerging, demand growth (from D0 to
D1) could have increased prices because the supply from aquaculture (S0,A) was not enough to keep pace
with demand. However, when the supply from capture fisheries reaches the backward-bending part of
the supply schedule for open-access fisheries or the vertical part of the supply schedule for managed
fisheries (see figure 2), the anticipated price increase incentivizes aquaculture expansion. Empirically, the
quantity supplied from aquaculture has increased dramatically over time (as shown in Figure 3). This trend
is often referred to as the “blue revolution” (Garlock et al., 2020), and it suggests that the supply curve
for aquaculture shifted outward (e.g., from S0,A to S1,A in Figure 4). Thus, the total seafood supply shifted
outward (from S0,Total to S1,Total), which has kept prices stable (as shown in Figure 4).
Asche and Smith (2018) argue that the shift in the supply schedule for aquaculture is consistent
with a process of induced innovation. Demand growth combined with limited supplies of wild-caught
seafood created incentives to innovate and expand aquaculture supply. Such an outward shift in the
supply schedule is not unique to aquaculture; in fact, it is common for food sectors (Alston et al. 2009).
However, inward supply shifts are also possible, most notably if climate change were to decrease the
productivity of capture fisheries and aquaculture.
Drivers of Growth in Aquaculture
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Extensification refers to increasing the number of regions and facilities that farm seafood as well
as the number of species that are farmed, while intensification refers to increasing the size of facilities
and/or amounts of inputs. Both extensification and intensification have driven growth in aquaculture
production, often in combination with new technology. Extensification has occurred in several ways. First,
new species have been added to the global aquaculture production mix. For example, farmed Atlantic
salmon was introduced in the 1960s and is the second-most consumed seafood in the U.S. Intensive
production of farmed tilapia and pangasius started in the 1980s and 1990s, respectively, and within two
decades of domestication, both were among the top-10 most consumed seafoods in the U.S. (Love et al.,
2020). Such successes have created incentives to attempt domestication of other species, particularly
highly valued species such as tuna and halibut. Second, successes in one region have been copied by other
regions, leading to increased production through expansion of the geographical area where a species is
farmed. For example, although there are no wild salmon native to the southern hemisphere, Chile is now
the world’s second largest producer of Atlantic salmon (Salazar and Dresdner, 2021). Even more striking,
tilapia, which were originally native to Africa, are now farmed in significant quantities in Asia, South
America, and Africa (Kumar and Engle, 2016). Lastly, firms have added more facilities within existing fish
farming industries and regions; for example, the number salmon farms in Norway grew throughout the
1990s (Asche and Bjørndal, 2011) .
Intensification has contributed to growth in aquaculture production in diverse ways. Across
species and regions, fish farming involves different levels of capital intensity and control of the production
system (Anderson, 2002). Aquaculture systems that developed early (and are sometimes still used) tend
to be extensive because the farmer controls few aspects of the production process. Indeed, extensive
operations rely heavily on the surrounding environment for inputs and tend to resemble capture fisheries,
with the farmer providing primarily labor to harvest and enhance habitat (Klinger et al. 2013). However,
the production systems for many species have become more intensive over time by adding feed and
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capital inputs such as feed dispensers and water quality monitors, exerting greater control over the
production process, increasing productivity, and ultimately farming on a larger scale (Asche, 2008). Larger
firms are also able to invest in the marketing and distribution of fish, including new product forms,
improved logistics, and expanded market outlets (Anderson, 2002; Asche, 2008). Because intensive fish
farming does not depend on just one common-pool natural resource, the structure of aquaculture
production that has emerged is very different from wild-caught fisheries. In particular, the most important
species group in aquaculture is fresh water fish (Garlock et al., 2020), and the largest producing countries
are the most populous developing countries (Belton et al., 2018). In contrast, the largest wild-caught
fisheries are marine species, and the largest producers are a mix of developing and industrialized nations,
with some having relatively small populations.
A key feature of aquaculture intensification is innovation that facilitates growth. Innovation
typically triggers productivity growth, reduces production costs, and makes the sector more competitive
(Mundlak, 2005). While innovations can be based on genuinely new insights, most often they are
adaptations of existing knowledge and technologies to new settings. Asche (2008) argues that the blue
revolution was largely caused by the transfer of technologies from terrestrial livestock production to the
production of aquatic organisms. This knowledge is not entirely transferable because the technological
challenges in aquatic environments are substantially different from those in land environments;
nevertheless, the basic principles are similar. Moreover, the innovations that facilitate growth in
aquaculture also result in some environmental externalities that are unique to the aquatic environment.
With his background on aquaculture, in the next section, we identify and discuss the common-
pool resource failures and other externalities that are the most urgent to address to ensure sustainable
growth in aquaculture that continues to contribute to global food security.
KEY EXTERNALITIES IN AQUACULTURE
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Because aquaculture uses the natural environment both extensively and intensively, the list of potential
negative externalities created by the industry (i.e., endogenous externalities) is long, including water
pollution from effluent, genetic contamination of wild populations from escaped domesticated fish,
habitat degradation from converting undeveloped environments to farming operations, disease spread,
and increased pressure on other natural resources due to input demands like feed. At the same time,
negative externalities from other industries (i.e., exogenous externalities) may affect aquaculture
production, including upstream water quality degradation, overfishing of capture fishery stocks that limits
aquaculture feed (aquafeed) supplies, and climate change. Aquaculture also has the potential to generate
positive environmental externalities through enhanced water quality, reduced reliance on more
greenhouse-gas-intensive animal proteins, and reduced pressure on capture fisheries. In this section, we
examine the evidence for these externalities and highlight those that are the most urgent to address
through better governance or policy interventions.
Pollution, Water Quality, and Escapes
Aquaculture farms interact with the surrounding environment. The specific production
technology and the size of the farm determine the scale of the effects on the surrounding ecosystem and
thus the potential externalities, both positive and negative. Aquaculture practices often closely interact
with the local ecosystem because there are few barriers that prevent water exchange between the farm
and the surrounding area. Oxygenated water is an essential input for aquaculture, which means farms
must either obtain it from exchanges with the surrounding environment or mechanically oxygenate. As
firms gain greater control over the production process, reliance on the surrounding natural environment
can be reduced. For instance, catfish ponds in Mississippi do not allow river water to flow through the
ponds or re-circulate water to re-oxygenate the water; rather they limit the effects of nitrogenous
excretions from the fish using aerators and sometimes oxygen gas to re-oxygenate water in the ponds
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(Tucker et al., 2017). In recent years, land-based recirculating aquaculture systems began producing fish
in completely closed systems, with water cleaned in biofilters and then re-oxygenated (Bjørndal and
Tusvik, 2019). Moreover, farming of some species may actually provide positive water quality externalities
because the organisms provide water filtration, as is the case with oyster farming (DePiper et al. 2017).
If the inevitable effluent and food waste from fish farms are not collected, they will spread in the
surrounding environment, increase the nutrient load, and degrade water quality. Antibiotics or other
medicines typically administered in feed may further contaminate effluent. In addition, maintenance of
production equipment at the farm may lead to chemical emissions into the surrounding ecosystem. For
example, cleaning equipment while it is in the water can release solvents. Finally, in all aquaculture
systems, if fish escape and survive, they may establish themselves as an exotic species and genetically
contaminate or compete with wild stocks.
Fish farmers have strong private incentives to address all of these environmental problems
(Pincinato et al., 2021). In general, increased control of the production process will increase the farmer’s
ability to reduce negative externalities, and innovations may encourage farmers to internalize some
externalities if doing so leads to increased revenues or decreased costs. For instance, an escaped fish is
lost revenue, which is added to the incurred costs of rearing the fish, and thus creates an incentive to
reduce escapes. Similarly, farm productivity generally increases with improvements in water quality,
which creates incentives for farmers to limit nutrient or chemical emissions.
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For example, Hukom et al.
(2020) show that shrimp farmers in Indonesia generate economic benefits from maintaining and even
improving water quality. However, without an appropriate governance system, farmers may lack
incentives to maintain or improve water quality (Pincinato et al 2021). In addition, despite individual
farmer incentives to internalize some water quality externalities, individual actions may fall short of the
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Innovations in land-based aquaculture that isolate production from the surrounding environment have the
potential to eliminate the escape problem and substantially internalize water quality effects.
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social optimum if the costs and benefits are not fully internalized. Moreover, because total emissions of
the industry within a region may be the most relevant for water quality, there is potential for free riding.
This suggests that cooperation or regulation will be necessary to address this externality.
For key pollutants in Norwegian salmon aquaculture, some degree of internalization of
externalities has occurred. The industry appears to have followed an Environmental Kuznets Curve in that
pollution initially increased with production, but as production continued to grow, the industry adapted
and pollution declined (Tveteras 2002). Antibiotic use and escaped fish in salmon farming provide
examples of this pattern, with both declining markedly as total production of salmon increased.
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Space as Both a Common-pool Resource and an Anti-commons Problem
Aquaculture is similar to terrestrial agriculture in that it has the potential to transform its
environment in dramatic ways. In particular, many aquaculture facilities are located in ecologically
productive nearshore and estuarine environments, and the type and amount of physical space required
to farm fish threatens the ecosystem services provided by these productive environments. Conceptually,
the physical space in marine and estuarine environments is a common-pool resource. That is, the use of
space for aquaculture may preclude (or subtract from) other uses, and without well-defined property
rights or regulation, the space is non-excludable (i.e., anyone can enter and use the resource). In the
extreme, there may be a race for space to set up new aquaculture facilities in locations where there is
limited excludability. Here we discuss the race for space in shrimp aquaculture, conceptualize physical
space as a commons problem, and introduce the anti-commons problem as a potential explanation for
slow aquaculture growth in some coastal nations.
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See Figures A1 and A2 in the online appendix.
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The race for space in shrimp aquaculture
The race for space argument is consistent with the history of early extensification in shrimp
aquaculture, which relied heavily on clearing mangroves, often from public lands. Mangroves are
generally favorable environments for extensive farming of warm-water shrimp, which dominate global
shrimp markets. However, mangrove deforestation is a significant environmental externality because
mangroves provide carbon sequestration, storm protection, juvenile fish habitat, and other ecosystem
services. From 1990 to 2020, global mangrove areas declined 6.6%, but the annual loss has slowed to
0.14% in the most recent decade (FAO 2020). It is unclear how much of the recent slowing in mangrove
loss is due to sector-specific governance interventions in aquaculture. For example, organic farms in South
America and Asia have either limitations on mangrove area disturbance or requirements for mangrove
reforestation (Ahmed et al. 2018). But it is not known whether such programs result in mangrove gains
relative to a counterfactual in which mangrove losses are slowing anyway. One reason for this ambiguity
is that shrimp farming has greatly intensified in recent decades, and thus has relied less on clearing
mangroves to establish production facilities (Petesch, Dubik, and Smith 2021). Moreover, areas that
avoided mangrove loss from shrimp aquaculture may not be immune to loss from other types of
development (Friess et al. 2020). For example, mangrove loss has been associated with growth in rice and
palm plantations and general economic development, and these drivers are heterogeneous across
different locations and time (Barbier and Cox, 2003; Friess et al. 2020).
Physical space as the common-pool resource
Determining the extent to which particular crops, aquaculture, or development patterns contribute to
externalities may not be essential if the overarching problem is that the common-pool resource is the
physical space itself. It is well known that a common-pool resource can provide benefits to society (often
in terms of resource rent) if use of the resource is rationed. These benefits can be squandered under open
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access because excess entry leads to overuse and diminished value for all users. By characterizing the
common-pool resource as space itself, the idea is to ration access to space and not necessarily to regulate
sector-specific effluents or usage of space. By contrast, sector-specific regulation could allow the race for
space to continue for other sectors. For example, regulation may prevent further agricultural
development but do nothing to prevent further clearing of mangroves for aquaculture. One could also
characterize the underlying commons problem as a failure to price ecosystem services, which means that
creating incentives to preserve ecosystem services could ameliorate mangrove loss regardless of the
specific sector driving the loss. For example, Siikamaki et al. (2012) estimate that a carbon price of just
$10 per ton of C02 would be sufficient to avoid most greenhouse gas (GHG) emissions associated with
mangrove loss.
The anti-commons problem
Although failure to adequately govern space can lead to overexploitation of coastal environments,
it is also possible that governance failures can lead to under-exploitation. In fact, a number of countries
that have greater capacity to govern space in the coastal zone, such as the United States, have actually
experienced dramatically lower rates of aquaculture growth (Abate et al., 2016; Garlock et al. 2020). There
are several possible explanations for these trends: 1) the coastal zone simply has more valuable
alternative uses in wealthier countries; 2) governance has been effective in combating externalities by
limiting aquaculture growth; 3) aquaculture growth has been limited because of the inability to compete
with imports from countries that rely on uncorrected externalities and/or have lower labor costs; or 4)
governance has led to under-exploitation of coastal environments. From the perspective of welfare
economics, the first and second explanations suggest that the trends in aquaculture growth are as they
should be, while the third explanation suggests that improved governance in places with high aquaculture
growth could stimulate similar growth in regions that are lagging. The fourth explanation, which has
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received less attention in the literature, suggests that wealthy countries have sacrificed jobs and economic
welfare through overly restrictive regulations (Anderson et al., 2019). We next examine this possibility
using the lens of an anti-commons problem.
An anti-commons problem refers to a common-pool resource setting in which there are multiple
exclusion rights that may lead to underuse of the resource (Heller 1998). That is, the use of anti-commons
resources may provide economic value, but the number of agents with exclusion rights may be large
enough to completely eliminate the ability to use the resource and thus to capture that value. Buchanan
and Yoon (2000) develop an anti-commons model and apply it to the example of residential construction.
They show that construction may be prevented when permits are required by several overlapping
agencies and failure to obtain any one of those permits is enough to stop construction. This means that
construction could be underprovided. They show that common-pool resource problems and the anti-
commons are symmetrical in that anti-commons problems are characterized by underutilization and
commons problems are characterized by over-utilization. Similarly, regulation of the anti-commons can
prevent value-enhancing behaviors, while regulation of the commons can prevent value-reducing
behaviors.
Applying this conceptual framework to aquaculture, coastal space can be viewed as an anti-
commons (Filipe et al., 2011). More specifically, the establishment of a coastal aquaculture facility may
require approval by multiple agencies that regulate or supply environmental quality, water resources,
public parks and open space, capture fisheries, transportation infrastructure, and agriculture. Moreover,
because multiple levels of government may assert exclusion rights, entry into fish farming may ultimately
be over-excluded. That is, the myriad of exclusion rights may lead to the underuse of aquatic space for
aquaculture (Knapp and Rubino, 2015). Indeed, if those empowered to issue permits do not seek to
maximize social welfare and pay little attention to forgone rents, they will rarely allow potential welfare-
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improving aquaculture investments. Abate et al. (2016) argue that this is the case in wealthy countries,
which are generally characterized by strict environmental regulations and limited aquaculture growth.
Disease as a Production Externality
Over the past two decades, the rapid rise of aquaculture through extensification and
intensification has led to major supply shocks from disease outbreaks. For example, Chilean farmed
salmon output decreased more than 60 percent from 2008 to 2010 due to a viral outbreak of infectious
salmon anemia, which led to a stagnation in global salmon production after years of substantial growth
(Fischer et al, 2017). The industry also continues to struggle with sea lice (a parasitic pathogen), which
cost the Norwegian industry an estimated US$436 million in 2011 (Abolofia et al. 2017). The shrimp
farming industry, which is the largest contributor to the global seafood trade, has also been plagued by
disease problems. Stentiford et al. (2012) estimate that up to 40% of tropical shrimp production is lost
annually, due mainly to viral pathogens. White spot disease hit the industry particularly hard in the 1990s,
with estimated losses in the range of $8-15 billion (Petesch, Dubik, and Smith 2021), and between 2010
and 2017, early mortality syndrome caused the Asian shrimp industry estimated losses of US$7.38 billion
(Shinn et al, 2018). The costs of disease outbreaks in the farmed salmon and shrimp industries highlight
the importance of disease management to both firms’ profits and policy makers concerned about the
aquaculture sector’s contributions to the economy and food supplies.
Why are these disease problems not simply a matter of production risk that firms can fully
internalize? The simple answer is that both extensification and intensification contribute to disease risks
that spill over from one facility to another and possibly to the wider ecosystem. More extensive farming
means more facilities are in close proximity to each other and thus often share the same natural
environment. As the number of farms increases, the possibility of disease outbreaks that spread to other
farms also increases. In addition, more intensive farming means higher stocking densities within each
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facility, which increases the potential for both higher facility-level pathogen loads and disease spread to
neighbors. Using a theoretical model, Fischer, Guttormsen, and Smith (2017) show that intensification
increases disease risk in a region, while a higher number of firms (extensification) dampens the incentive
to internalize disease risks. This implies that one possible mitigation approach for salmon farming would
be firm-specific licensing within a particular fjord that is isolated from other firms in a neighboring fjord.
This is how salmon licensing operates in the North Atlantic’s Faroe Islands (Bakkafrost 2019). However, in
settings with many producers, regulations that coordinate farmers’ risk mitigation actions are also likely
to be necessary, and regulations to address non-production externalities (such as nutrient pollution that
harms local ecosystems) would still be required. Complicating matters further, addressing disease through
entry restrictions could lead to intensification among incumbent producers, which could aggravate
existing problems because the greater stocking densities associated with intensification increase the
disease load (Oglend and Soini, 2020).
Climate Change
Climate change has the potential to affect aquaculture, and the expansion of aquaculture has the potential
to affect climate change. Here we examine climate threats to aquaculture, potential climate mitigation
benefits, the importance of modeling the price response to understand the interactions between climate
change and aquaculture, and the potential impact of a carbon tax on the competitiveness of farmed
seafood relative to other protein sources .
Threats to aquaculture from climate change
Some forms of aquaculture are clearly threatened by climate change. For example, increasing
frequency and intensity of storms can disrupt coastal marine aquaculture and estuarine aquaculture
operations. In addition, ocean warming can push temperatures beyond the ideal range for farming a
particular species in a particular location (Hermansen and Heen, 2013) and also affect pelagic (i.e., the
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upper water column) fisheries that supply important feed ingredients (Pincinato et al, 2020). Ocean
acidification can disrupt aquaculture facilities, with mollusks being particularly vulnerable (Colt and Knapp
2016). Because creatures that are kept in captivity are not able to adjust to changed local conditions by
migrating, these climate changes create incentives for firms to relocate or change species. Fish farmers
would be expected to adapt in this way if they have sufficient capital, are not prohibited from adapting
through regulation, and have some means to be licensed in new locations (or lease new locations). This
means that the anti-commons problem looms large in wealthier countries because it may prevent this
sort of adaptation by farmers. In lower-income countries, capital constraints may be a larger challenge to
adaptation and interfere with efforts to address food security challenges (Mitra et al., 2019).
Climate mitigation benefits
Growth in aquaculture may also yield climate mitigation benefits if it facilitates global substitution
away from more GHG-intensive animal proteins. Using ecological models and life cycle analysis, studies
of the contributions of food to GHG emissions emphasize the energy needed to produce calories or
protein (Poore and Nemecek, 2018; Springmann et al. 2018). In these frameworks, seafood generally
produces low GHG emissions relative to other animal proteins. Thus, the expansion of aquaculture has
the potential to reduce negative externalities in the global food system by replacing more GHG-intensive
terrestrial protein sources. This potential benefit of aquaculture depends on a combination of 1) dietary
substitution toward seafood and away from more GHG-intensive animal proteins like red meat and 2)
disproportionate growth in seafood to supply the future demand growth associated with rising incomes
and population. This shift toward seafood could also occur through relative price decreases of farmed
19
seafood due to technological innovation and/or explicit pricing of carbon that lowers the relative price of
farmed seafood.
The magnitude of future GHG mitigation attributable to aquaculture is uncertain. Nevertheless,
aquaculture is projected to grow even without favorable climate policies. For example, Kobayashi et al.
(2015) project that total seafood supply will grow from 154 million tons in 2011 to 186 million tons by
2030, with all of the growth coming from aquaculture. By contrast, non-economic models of aquaculture
potential tend to focus more on GHG intensity and thus do not provide information about the magnitudes
of the GHG mitigation potential of aquaculture because they fail to consider price and supply responses.
5
As we discuss below, economists have long criticized this kind of modeling because it ignores price and
incentives, the very elements that have contributed to the significant growth and innovation in
aquaculture.
Implicit modeling of the seafood market and climate change
Understanding the interactions between climate change and growth in aquaculture requires an
explicit model of price formation (as in Figures 2 and 4). Unfortunately, ecological models tend to
completely ignore prices. Deirdre McCloskey summarizes the economics critique of the ecological
approach, using oil as an example: “The non-economic scientists declare, ‘We have such-and-such a
structure in existence, which is to say the accounting magnitudes presently existing, for example the
presently known reserves of oil.’ Then ignoring that the search for new reserves is in fact an economic
activity, ... they calculate the result of rising ‘demand’ (that is, quantity demanded, not distinguished from
the whole demand curve), assuming no substitutions, no along-the-demand-curve reaction to price, no
5
The non-economics literature typically estimates the potential magnitude of aquaculture’s contribution using
models that resemble the approach used in Limits to Growth (Meadows et al. 1972). Specifically, these models
assume technology with fixed proportions of inputs (effectively Leontief production), input supplies that are
unresponsive to price, and no technological innovation (Gentry et al. 2017; Froehlich et al. 2018).
20
supply reaction to price, no second or third act, no seen and unseen, such as an entrepreneurial response
to greater scarcity.” (McCloskey 2019, p. 191).
Because non-economic models of aquaculture production and other natural resource systems
persist, and economists often must comment on the issues that they address, we illustrate what such
models imply about the market for seafood. Figure 5 translates ecological models into a supply and
demand framework, depicting supply as perfectly elastic such that price is always fixed at P0, with some
absolute limit at QMax. Demand is viewed as a series of points (illustrated by D0 through D3) that somehow
never lie above or below the perfectly elastic supply. That is, demand is unresponsive to price, and price
is unresponsive to demand. In this modeling framework, one can be optimistic or pessimistic. If current
demand (D0) and projected future demand (D1) are below the limit to growth (QMax), then optimism
prevails because fish are cheap, and anyone who can pay P0 for them can buy them. If current demand is
at or near the limit to growth (D2) or future demand exceeds the limit (D3), then pessimism prevails
because although price remains low, there is a permanent shortage with no mechanism to clear the
market, and thus an unspecified gloomy future ensues. With no possibility for a supply or demand
response to price, this model fails to produce any meaningful prediction or information about the future,
including the future of GHG mitigation from aquaculture. Moreover, if climate change decreases or
increases the supply of seafood, there is no price response, and thus any resulting shortages or surpluses
will depend on one’s level of optimism.
Explicit modeling of the effects of climate change mitigation on aquaculture
One policy that is frequently discussed as an option for mitigating climate change is a carbon tax. To
illustrate the potential impact of such a tax on aquaculture, in particular on the competitiveness of farmed
seafood relative to other protein sources, consider a carbon price of $100 per metric ton of CO2. Using
median CO2 equivalents from Poore and Nemecek (2018) and assuming no technological change, we
21
calculate that such a tax would lead to price increases of $6.00/kg for beef, $4.00/kg for lamb, $1.30/kg
for pork, $0.90/kg for poultry, and $0.70/kg for farmed fish.
6
Given that farmed fish is generally more
expensive than ground beef, this hypothetical carbon tax would not only have a greater impact on the
absolute price of beef than on the absolute price of fish; it would also increase the price of beef relative
to fish, which means income and substitution effects will decrease beef consumption and reduce
associated GHG emissions.
Interactions with Capture Fisheries and the Role of Aquafeeds
Here we discuss the possibility that growth in aquaculture reduces pressure on capture fisheries, the role
of aquafeeds, evidence concerning whether aquaculture growth puts pressure on capture fisheries that
supply aquafeeds and whether aquafeed supply has limited growth in aquaculture, and the potential for
interactions between capture fisheries and feed to cause problems for aquaculture growth in the future.
The potential for aquaculture to reduce pressure on capture fisheries
Aquaculture may have positive environmental impacts by reducing pressure on capture fisheries
that are poorly managed. For example, suppose severe overfishing coupled with demand growth would
have led to an equilibrium along the backward-bending portion of capture seafood supply (where D1
intersects S0,W in Figure 4). This outcome can be thought of as a counterfactual (that is, when there is no
aquaculture sector). The actual outcome in the capture fisheries sector when there is supply from the
aquaculture sector is where the equilibrium price (i.e., P1) intersects S0,W, which corresponds to a higher
equilibrium stock than what would have occurred without aquaculture. The same improvement in stock
condition can be seen in Figure 2, if we interpret an increase in aquaculture supply as a decrease in the
6
To put these numbers in perspective, in January 2021, the U.S. retail price of ground beef was $8.74/kg. (U.S.
City Average from https://www.bls.gov/regions/mid-
atlantic/data/averageretailfoodandenergyprices_usandmidwest_table.htm ).
22
residual demand for capture fisheries (an inward shift in demand from D1 to D0). In this case, the resulting
equilibrium intersection of D0 with SOA implies an improvement in stock condition. Although this effect has
the potential to produce conservation benefits, it is not a perfect substitute for effective management of
capture fisheries (Li et al. 2021). In a well-managed fishery with the supply schedule SMSY (shown in Figure
2), a similar reduction in demand will lead to a price reduction with no quantity change if the harvest
quota is binding (Valderrama and Anderson, 2010).
The role of aquaculture feed
Just as in land-based animal production, feed is a key input factor in aquaculture. Omnivorous and
carnivorous fish species require, or are greatly aided by, fishmeal and fish oil in their diets because these
feed components provide important micronutrients, fatty acids, and protein not easily replaced by
vegetable components. Marine protein in feed predominantly comes from turning fish from capture
fisheries into fishmeal and fish oil. A higher level of marine components is generally included in feed for
high-value carnivorous and omnivorous species, such as shrimp and salmon, which are the largest
consumers of fishmeal and fish oil, respectively (Shepherd et al, 2017).
Fishmeal and fish oil in aquafeed originates primarily from capture fisheries of small pelagic
species, known as reduction fisheries. The largest fishmeal producing country is Peru, where anchoveta
(the world´s largest fishery by quantity) are reduced to fishmeal. Anchoveta and other capture fisheries
are substantial suppliers of aquafeed to the aquaculture sector. For example, in 2018, Peruvian anchoveta
accounted for 37 percent of global fishmeal supply and an estimated 7 percent of all fish produced globally
was from reduction fisheries (FAO, 2020). The growth in aquaculture production has raised concerns
about excessive pressure on the capture fisheries that supply marine feed components and the possible
diversion of food fish to aquafeed and away from low-income households (Troell et al 2014). In particular,
23
Naylor et al. (2000) have argued that sustainable aquaculture growth depends on a reduced reliance on
wild fish inputs.
The connection between aquaculture and capture fisheries through feed as an input raises two
key questions about externalities. First, does growth in aquaculture and the associated demand for marine
ingredients for feed increase pressure on capture fisheries and induce common-pool resource
externalities? Second, do common-pool resource externalities in capture fisheries limit supplies of marine
feeds in ways that constrain aquaculture growth? The hypothesis that there is a “fishmeal trap” asserts
that the answer to both of these questions is affirmative, which implies a positive feedback loop between
aquaculture’s use of aquafeed and declining fish stocks (Naylor et al., 2000). That is, if the fishmeal trap
hypothesis holds, there is a vicious cycle in which aquaculture demand bids up the price of feed, reduces
capture fishery stocks, decreases long-run catches and feed supplies, constrains aquaculture growth,
further bids up the price of feed, and adds yet more pressure on capture fisheries. In the remainder of the
discussion, we examine the evidence for the fishmeal trap; that is, the link between aquaculture and the
status of fish stocks that provide feed supplies and whether capture fishery-based feed supply has limited
aquaculture growth.
Impact of aquaculture on fish stocks that supply feed
Although most fishmeal and fish oil supplies are used by the aquaculture sector, there is little
evidence to suggest that aquaculture has caused declines in capture fisheries. First, most of the top
contributors to fishmeal supplies are not overfished or undergoing overfishing.
7
Because aquaculture has
grown substantially over the past five decades, if it were causing declines in capture fisheries, we would
expect to see poor stock conditions for the main pelagic species that supply fishmeal and fish oil as well
as continued overfishing. In fact, overfishing of these stocks was more of a problem in the past (Hilborn
7
See Table A1 in the online appendix.
24
et al., 2020) when aquaculture was an emerging sector and most fishmeal went toward terrestrial
livestock feed and fertilizer (Asche and Oglend et al., 2013). Second, a simple regression of the annual
total fishmeal production on Peruvian achoveta landings (for the 1976-2016 period) suggests that
approximately two-thirds of the variability in fishmeal supply can be explained by fluctuations in these
landings.
8
However, this fishery has sophisticated management with strict quota controls that now include
catch shares
9
(Tveteras et al., 2011), and fluctuations have largely been due to environmental variability,
especially El Niño-Southern Oscillation cycles. Third, catches in the remaining fisheries that contribute to
fishmeal supplies have been relatively stable over the last five decades.
10
Although stable catches do not
rule out the possibility of overfishing, there is no evidence of precipitous declines in these fisheries that
correspond to the rise of aquaculture over the past 50 years.
The aggregate data suggest that the expansion of aquaculture has actually led to some
conservation benefits for capture fisheries because (as suggested in Figures 1-4) prices have not increased
and capture seafood supplies have not declined. Although this evidence is not causal, it seems unlikely
that capture fisheries overall would be faring as well as they are today in a world without aquaculture
supply and with substantially higher real seafood prices.
Impact of feed supply on aquaculture growth
We next examine the evidence on the link between feed supply and aquaculture growth. First,
the fishmeal trap implies that aquaculture production will be unable to grow beyond the limitation set by
the availability of fishmeal and fish oil. When viewed in this way, the fishmeal trap hypothesis is not
supported by the data. Indeed, as shown in Figure 6, between 1976 and 2017, total aquaculture
8
See Table A2 in the online appendix.
9
Catch shares, which include individual fishing quotas, are market-based policies that resemble cap and trade in
pollution control and are aimed at addressing the commons problem.
10
See Figures A3a and A3b in the online appendix.
25
production and production by species group grew substantially more than total fishmeal and fish oil
production.
11
Because carnivorous species rely more on marine ingredients, one would expect growth to
be lower among these species if marine ingredient availability substantially limited growth. However, this
is not the case. Average annual growth rates for production of crustaceans and marine fish were 14.8%
and 8.2%, respectively. For fresh water fish, the rate was 8.5%, while the rate for mollusks (which are
generally not fed marine ingredients) was the lowest, at 6.2%. Thus we are able to reject the second
element of the fishmeal trap hypothesis; that is, that aquaculture growth has been limited by feed
supply.
12
The future of the fishmeal trap
Because aquaculture feed remains a large consumer of fishmeal and fish oil, it is important to
examine whether the fishmeal trap is likely to be a problem in the future. In recent years, the prices of
fishmeal and fish oil have been high (Asche and Oglend et al. 2013; Misund et al., 2017). Higher prices
provide economic incentives to reduce reliance on the fisheries that have historically supplied the raw
materials for fishmeal and fish oil. For example, the marine components from byproducts of fish
processing (such as heads and tails) have become more important in aquafeed supply, now accounting
for around 25-35 percent of all fishmeal and fish oil produced (FAO, 2020). Greater utilization of waste
from fish processing suggests that there are some self-regulating features of the aquaculture-feed linkage
because higher feed prices have created incentives to use waste byproducts from the processing of edible
fish. The selective use of marine components during different production stages (e.g., focusing on early
life stages) has contributed to a decline in total use of marine feed, and efforts to replace marine
11
From 1976 to 2017, average annual growth rates of fishmeal and fish oil production were 1.2% and 1.8%,
respectively. In the same period, the corresponding rate for aquaculture production was 7.8%.
12
More specifically, we test the null hypothesis that the annual growth rate of aquaculture is equal to the growth
rate of fishmeal production and reject (P < 0.01) for all species groups. For fish oil, we reject the null hypothesis for
all species (P < 0.01) except mollusks (P < 0.025).
26
components with non-marine substitutes are continuing. For example, aquafeed in Norwegian salmon
production contained as much as 70% marine components in 2000, but by 2014, the share had declined
to 27% (Misund et. al., 2017). Moreover, Kok et al (2020) find that global aquaculture currently produces
three to four times more fish than it consumes, casting further doubt on the notion that aquafeed supply
has limited aquaculture growth.
Addressing the fishmeal trap hypothesis
The lack of evidence thus far for the fishmeal trap suggests that a combination of market incentives and
governance in fisheries can both ensure sustainable future aquaculture growth and avoid the negative
effects of demand for marine ingredients on capture fisheries. As we have discussed above, there is no
evidence that feed places a limit on aquaculture growth; nor is there evidence that aquaculture has
deleterious effects on capture fisheries. Moreover, the aquaculture industry faces strong incentives to
reduce use of marine ingredients. Nevertheless, some regulators and environmental organizations have
sought to steer landings of pelagics away from use in fishmeal and towards human consumption, including
the Aquaculture Stewardship Council’s guidelines for reduction of marine ingredients in aquafeeds
(Osmundsen et al., 2020) and various attempts to channel Peruvian anchoveta toward human
consumption (Freon et al., 2014). Although it is clear that globally many fisheries require improved
governance to reduce overfishing, including some fisheries that supply feed ingredients, these particular
interventions are attempting to address a problem that does not exist.
SUMMARY AND POLICY RECOMMENDATIONS
This article has discussed the importance of seafood to global food security (Asche et al. 2015;
Belton et al. 2020). Moreover, we have argued that as wild fish stocks get closer to being fully exploited,
aquaculture is the only seafood sector that can significantly increase production, albeit with the potential
27
for a number of externalities. We have shown that the environmental externalities of aquaculture can be
positive as well as negative; some externalities are not true externalities because firms have incentives to
internalize them; and some perceived externalities do not exist. Since farmed seafood is heavily traded
internationally and a substantial share of aquaculture production is based in developing countries with
limited management capacity, there is growing interest among policy makers in using international trade
policy to manage aquaculture externalities. However, such policies run the risk of having little or no
environmental impact and serving only to reduce economic opportunities and increase global income
inequality (Asche et al. 2016). This suggests that more direct national and regional policies and regulation
are needed to address these externalities and to ensure more sustainable growth in the global
aquaculture sector. With this in mind, we conclude with policy recommendations aimed at addressing
externalities, improving spatial governance, and supporting technological innovations in the aquaculture
sector.
Address Endogenous Externalities
The types of regulations that could be used to address endogenous externalities such as farm effluents,
genetic contamination, disease spread, and pressures on other natural resources have been discussed in
detail in the economics literature. Such regulations include monitoring of point source pollution,
restrictions on siting and size of aquaculture facilities, and fines for failure to comply. For example, for
existing facilities, the regulation of disease externalities could include requiring bio-security measures and
monitoring of pathogens. For new facilities, siting decisions that isolate firms from each other would
increase incentives to internalize disease externalities. To this end, policy makers may want to consider
granting local production monopolies within a common pool to address the spatial nature of disease
externalities.
28
Demand side market-based approaches, such as eco-labeling and third-party certification, could
also be used to address aquaculture externalities. However, as with capture fisheries, the evidence on the
effectiveness of these approaches in changing producer and consumer behavior is mixed (Bush et al. 2013;
Roheim et al. 2018).
Improve Spatial Governance
Siting new aquaculture facilities to minimize disease highlights the general importance of governing space
in aquaculture. Improved governance of space through, for example, deliberate spacing of aquaculture
facilities, could not only mediate some disease externalities but also help to reduce the habitat
degradation associated with effluent, the clearing of mangroves, and the ecological effects of escaped
fish. It could also promote spatially explicit positive externalities such as the ecosystem services provided
by oysters (DePiper et al. 2017). At the same time, if underdeveloped aquaculture is indeed a reflection
of the anti-commons in countries like the U.S., improved spatial governance is essential to reduce the
excess regulatory burden from overlapping jurisdictions.
13
Support Technological Innovations
If aquaculture is overall a “green” production technology relative to other animal protein sources,
then future research to spur technological innovations will be critical to ensuring an increased role for
aquaculture in sustainable food production. Innovations do not generally occur accidentally. Rather, they
tend to emerge in order to avoid anticipated scarcities. Hence, we would expect emerging technologies
in aquaculture to resolve specific scarcities, such as those concerning feed utilization. Some aquaculture
industries require more technical expertise than others and, even for the same species, there is
13
We expect that such governance would manifest as excess exclusion that is principally applied at the facility
siting stage.
29
considerable variation in production methods, with some being far more efficient than others. Thus,
facilitating the adoption of existing efficient technologies can be just as important as developing new
technologies. This suggests that improving feeds or instituting breeding programs for existing species
could be as important for the continued growth of aquaculture as new technologies.
Summary of Policy Recommendations
To summarize, we recommend three broad actions for policy makers to consider to support
sustainable aquaculture and its contribution to food security: 1) improve spatial management; 2) facilitate
adaptation to climate change and climate change policy; and 3) promote innovation. We argue that spatial
management is the most important governance action to pursue because the greatest environmental
policy challenges in aquaculture (that is, overuse or underuse of the spatial commons and disease
externalities) all have a spatial dimension. Moreover, even for conventional effluent problems such as
nutrient pollution, setting standards so that loads do not overwhelm the surrounding ecosystem requires
customizing spatial management to the facility and its surrounding geography. Adaptation to climate
change also has a spatial dimension. To the extent that aquaculture facilities are embedded in natural
systems facing a changing climate, adaptation will require clear guidelines that specify when facilities are
permitted to substitute one species for another in a location and that allow facilities to relocate in
response to changing local climate conditions. Relocating facilities will, in turn, require functioning
markets that allocate space in the aquatic environment. Good spatial governance would also enable firms
to adapt to carbon pricing and to capture the gains from maintaining the ecosystem services associated
with mangroves, for instance, or to more readily shift to less carbon-intensive species. Lastly, if
aquaculture is to realize its green potential, it is essential to facilitate continued innovation. Polices that
explicitly ban or limit the adoption of new technologies such as genetically modified fish or offshore fish
farming could undermine aquaculture’s green potential. Similarly, investing resources in problems that
30
are minor or non-existent (such as the fishmeal trap) shifts these resources away from more productive
uses within the aquaculture sector. By contrast, policies that invest in improved breeding and feeding
technologies, as well as biosecurity measures that reduce disease transmission, would be more likely to
facilitate sustainable growth of the aquaculture sector.
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(a)
(b)
Figure 1. Stagnation in global capture fishery production, real income, and real prices. Panel a: capture
fishery production, 1950-2018. Panel b: 1990-2018, with production overlayed with real seafood price
(based on the UNFAO Fish Price Index (Indexed to 1990) and inflation-adjusted with the U.S. CPI for All
Urban Consumers) and real world income (measured as IMF gross domestic product adjusted by
Purchasing Power Parity). Sources: FAO FishStat Plus, https://www.fao.org/; IMF, https://www.imf.org;
Tveteras et al. (2012); U.S. Bureau of Labor Statistics, https://www.bls.gov/cpi/
0
20
40
60
80
100
120
Million Metric Tons
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
20
40
60
80
100
120
Index Value (1990=1)
Million Metric Tons
Capture Production Real World GDP Real Seafood Price
36
Figure 2. Stylized Demand and Supply for Capture Seafood. Notes: SMSY is the global supply with all fisheries managed according to maximum
sustainable yield, and SOA is the global supply with all fisheries under open access. Based on Anderson (1985) and Li et al. (2021).
Quantity
Price
D0
D1
Q1OA
SOA
QMSY
P1OA
SMSY
P1MSY
P0OA
P0MSY
Q0OA
38
Figure 4. Stylized Demand and Supply for Seafood (Including Aquaculture)
Notes: S0,W is the wild-caught fishery supply combining SOA and SMSY from Figure 2, S0,A is initial (low) aquaculture supply, S1,A is later (high)
aquaculture supply, S0,Total is the sum of S0,W and S0,A, and S1,Total is the sum of S0,W and S1,A. D0 is low demand, and D1 is high demand.
Quantity
Price
D0
D1
Q0
S0,W
Q1
P0 = P1
S0,Total
S0,A
S1,A
S1,Total
39
Figure 5. Implicit Model of the Aquaculture Market in Non-economic Studies of Growth Potential
Quantity
Price
D0
Optimistic
Present
QMax
P0
D1
Optimistic
Future
D2
Limit to Growth
Pessimistic
Present
D3
Pessimistic
Future
S0
40
Figure 6. Aquaculture, Fishmeal and Fish oil Production
Notes: All production is in million tons, from 1976 to 2017. Fishmeal production indicated by black line; Fish oil production indicated by black
dotted line. Source(s): FAO FishStat Plus, https://www.fao.org/
0
10
20
30
40
50
60
70
80
90
1976 1986 1996 2006 2016
Million Metric Tons
Crustaceans and Molluscs Freshwater fishes
Marine and Diadromous fishes Fishmeal
Fish Oil
