Download Balanced harvesting in fisheries: a preliminary analysis of

ICES Journal of
Marine Science
ICES Journal of Marine Science (2016), 73(6), 1668– 1678. doi:10.1093/icesjms/fsv156
Contribution to the Themed Section: ‘Balanced harvest and the ecosystem approach to
fisheries’
Original Article
Balanced harvesting in fisheries: a preliminary analysis
of management implications‡
S. M. Garcia1 *, J. Rice 2, and A. Charles 3
1
IUCN Commission on Ecosystem Management, Fisheries Expert Group (IUCN-CEM-FEG), Gland, Switzerland
Fisheries and Oceans Canada, Ottawa, Canada
3
Saint Mary’s University, Halifax, Canada
2
*Corresponding author: tel/fax: +39 0661705228; e-mail: [email protected]
Garcia, S. M., Rice, J., and Charles, A. Balanced harvesting in fisheries: a preliminary analysis of management implications‡. – ICES Journal of
Marine Science, 73: 1668– 1678.
Received 30 March 2015; revised 24 July 2015; accepted 10 August 2015.
Balanced harvest (BH) proposes to distribute a moderate mortality from fishing across the widest possible range of species, stocks, and sizes in an
ecosystem, in proportion to their natural productivity so that the relative size and species composition are maintained, in line with the CBD requirement for sustainable use. This proposal has many and not always intuitive implications for fisheries management, e.g. in relation to selectivity,
protection of juveniles and spawning sites, models of harvesting strategies, a focus on size and species, the impacts of discarding, aspects of emblematic species and ecosystem services, operational complexity, partial implementation, ecosystem rebuilding, and relations with broader management frameworks. The paper closes with a discussion of BH implementation, concluding that a logical step would be to integrate several separate
initiatives to move fisheries into a more ecosystem-conscious context. Implementation challenges will be encountered, but there are lessons to be
drawn from fishery ecosystems already close to BH, as in some tropical multispecies fisheries, and further, the implementation challenges are already
being taken on in many well-managed fisheries and areas as management begins to address the realities of what ecosystem-based fishery management actually entails.
Keywords: balanced harvest, biodiversity conservation, ecosystem approach, fisheries management, implementation, management strategy.
Introduction
The Ecosystem Approach is defined by the 1998 Malawi Principles,
adopted formally by the Convention on Biological Diversity in 2000
(CBD Decision V/6). While the Principles provide a wide range of
guidance—on governance, management, cross-sectoral impacts,
economic incentives, balance between conservation and use; information needs and participation—there is only one Principle referring explicitly to ecosystem parameters. Principle 5 states that
conservation of ecosystem structure and functioning, in order to maintain ecosystem services, should be a priority target of the ecosystem
approach. Two key assumptions lay behind this wording. First, continued provision of ecosystem services is essential for the well-being
of both humanity and other species, since all depend on ecosystem
services for survival. Second, continued provision of ecosystem services requires maintaining ecosystem functioning and resilience,
which in turn depends on a dynamic relationship within, among,
and between species and their abiotic environment, as well as the
physical and chemical interactions within the environment.
At the time the Malawi Principles were adopted, scientific evidence in support of both assumptions was incomplete, but they
were considered firmly enough grounded in sound science to be
accepted by all Parties. In the years since, scientific evidence has continued to accumulate progressively reinforcing these assumptions
(Hails and Ormerod, 2013; Micheli et al., 2014; Mumby et al.,
‡
Paper based on a presentation made at the IUCN-CEM-FEG on Balanced Harvest. Balanced Harvest in the Real World. Scientific, Policy and
Operational Issues in an Ecosystem Approach to Fisheries organized in close cooperation with the Food and Agriculture Organization of the
United Nations (FAO), Rome, 29 September–2 October 2014.
# 2015
International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved.
For Permissions, please email: [email protected]
Balanced harvesting in fisheries
2014). As a consequence, conservation and, where appropriate,
restoration of these interactions and processes appears of greater
significance for the long-term maintenance of biological diversity
than simply protection of species (UNEP/CBD, 1998; FAO, 2003a).
This forms the basis for the recent proposal to shift fisheries
towards a balanced harvest strategy (BH, referred to as “Balanced
Exploitation” in Zhou et al., 2010) is a proposed harvesting strategy
that “distributes a moderate mortality from fishing across the widest
possible range of species, stocks, and sizes in an ecosystem, in proportion
to their natural productivity so that the relative size and species composition is maintained” (Garcia et al., 2011, 2012). The broad aim
of BH is to provide a means to help maintain ecosystem structure
and functioning [to the extent that it is maintained by maintaining
structure (cf. Ecosystem structure and function)], in keeping with
the goals of the Convention on Biological Diversity. The concept,
which is still under examination and development, emerges from
a critique of the common concentration of heavy fishing pressure
on medium to large sizes and species and its negative effects on
ecosystem structure and function, e.g. truncation of the size/age
distribution (Fisher et al., 2010; Brunel and Piet, 2013); reduction
in size/age at maturation; excessive reduction in spawning potential; modification of the species composition and assemblages
dominance (fishing down the foodweb); and loss of resilience to
climatic oscillations (Pauly et al., 1998; Dulvy et al., 2003; Enberg
et al., 2009; Fisher et al., 2010; Hsieh et al., 2010; Vasilakopoulos
et al., 2011; Heino et al., 2013; Christensen et al., 2014).
The proposal for BH has implications for changes to some basic
aspects of conventional fisheries management that address the selection of fish (and invertebrates) to harvest, and the intensity of fishing
the selected species and sizes. These aspects are rooted in the 1982
United Nations Law of the Sea Convention (LOSC) and the 1995
Fish Stock Agreement (FSA), both of which make the maximum
sustainable yield (MSY) the foundation for management strategies
and tactics. The MSY concept has been for each species considered
largely in isolation from the rest of the ecosystem and with quite
variable degrees of success (Larkin, 1977; May et al., 1979;
Jakobsen, 1992; Mangel et al., 2002; Hilborn and Stokes, 2010;
Finley and Oreskes, 2013). The broader accountabilities of ecosystem functioning and services provided in the Malawi Principle 5
have underscored the shortcomings of single-species MSY implementations at the ecosystem scale. Although these shortcomings
are now well documented (Blanchard et al., 2014; Voss et al.,
2014), many of the proposed alternatives are simply proposals for
which some species will be under-harvested relative to MSY, so
that other species can be fully harvested relative to that standard
(May et al., 1979; Mace, 2001). This still falls short of addressing
the biodiversity and ecosystem services concerns expressed in the
Malawi Principles, and necessarily must reduce overall sustainable
harvests from an ecosystem, thereby running counter to the increasing need for fish in meeting future global food security needs (HLPE,
2014).
The idea of shifting to BH also has major implications for the
choices of strategies and tactics for managing human uses of ecosystems, and moreover, the need for full assessments underlying such
choices—which include the daunting task of assessing ecosystem
structure, function, and services. Although ecosystem structure
can be directly monitored and quantified, models become increasing important as assessments attempt to also quantify trends in ecosystem functioning, services, and their resilience (IPBES, 2015).
Thus, in practice over many decades, aspects of structure (such as
spawning-stock biomass) were quantified in assessments, with
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models used to infer how functions (such as the production of
recruits) would be expressed, with such models being continually
improved as their shortcomings were understood and the models
augmented (Godbold et al., 2011; Wilen and Wilen, 2012;
Planque et al., 2014). This increasing reliance on models in assessments of ecosystem functions and services is true of evaluations of
even conventional management practices (i.e. , based on Beverton
and Holt Yield/Recruit theory and applied since WWII at single
stock level to optimize or maximize yield, controlling the age-atfirst-capture and fishing pressure, using a range of instruments),
and is essential for exploration of alternative strategies that have
yet to be implemented, including BH (Plaganyi, 2007; Zhou et al.,
2010; Rochet et al., 2011; Jacobsen et al., 2014).
Early research on BH focused essentially on its bio-ecological and
modelling aspects, with little on policy, economic, and operational
implications. It was stressed from the onset that more thought was
needed in those areas (e.g. Garcia et al., 2011, 2012), and this contribution seeks to provide an analysis of fishery management implications, in particular. This reflects on discussions that have taken place
on the BH concept, since 2010, with diverse groups of scientists,
advisers, policy-makers, and managers in the CBD, IUCN, FAO,
and ICES arenas as well as in national and regional meetings. These
rich discussions inspired a series of papers to address current developments in many key areas. These comprise both a few BH-related
papers already published (Andersen and Pedersen, 2010; Hsieh
et al., 2010; Kolding and van Zwieten, 2011, 2014; Rochet et al.,
2011; Smith et al., 2011; Law et al., 2012, 2013; Heino et al., 2013;
FAO, 2014a, b; Jacobsen et al., 2014; McGarvin, 2014) as well as
Charles et al. (this volume).
The management implications of BH are still more diffuse than
the questions about ecological and economic aspects, and depend to
some extent on the outcomes of those studies. This paper explores
the management implications of BH even as their understanding
evolves, to inform the ongoing “policy dialogue”. A full policy dialogue will require pilot projects implementing policy options, to be
run and evaluated; planning those pilots will be based on the ecological and economic results that are just emerging. This paper is
intended to summarize the nature of the management and policy
questions that are emerging, and suggest ways that the emerging ecological and economic insights might be viewed in the policy contexts
provided by both the ecosystem services and functioning of the
Malawi Principles on the Ecosystem Approach, and the growing
awareness that fisheries (as well as aquaculture) have a role to play
in addressing the increasing concerns about global food security.
The paper does not seek to analyse specific management tools
(e.g. implications for total allowable catch and catch quota
systems, for fishing effort controls, or for Territorial Use Rights in
Fishing, to name a few), except in certain specific cases (e.g. gear
restrictions and discard bans). In the following sections, we highlight and discuss issues concerning the relations between BH and:
(i) selectivity, (ii) protection of juveniles and spawning sites; (iii)
modelling complexity and realism; (iv) focus on size and species;
(v) discard bans; (vi) emblematic species and ecosystem services;
(vii) operational complexity; (viii) partial implementation; (ix) ecosystem rebuilding; and (x) relations with broader management frameworks. The paper closes with a broader discussion of BH
implementation, concluding that it is a logical step to integrate
several separate initiatives to move fisheries into a more ecosystemconscious context (e.g. fleet scale management and discard bans).
Implementation challenges will be encountered, but they are implementation challenges already being taken in many well-managed
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fisheries and areas as management begins to address the realities of
what ecosystem-based fishery management actually entails.
Selected issues
Several of the most significant issues arising in relation to BH, and
relating in some manner to fisheries management, are discussed
below. Many are still under consideration and therefore the analysis
below should be considered as a “work in progress”.
Ecosystem structure and function
Ecosystem structure (e.g. size and composition, biodiversity,
habitat) and functions (e.g. productivity, biomass transfer, resilience) are at the core of ecological theory (e.g. Odum, 1971), and
their maintenance has long been considered a priority for conservation, sustainable use, and restoration of ecosystems. This is found,
for example, in the 1980 World Conservation Strategy (IUCN/
UNEP/WWF, 1980), and enshrined in the 1998 CBD Malawi principles, discussed above.
In fisheries, the need to maintain ecosystem structure and function has been acknowledged by fisheries at least since the Reykjavik
Declaration (FAO, 2003b) and is embedded in the goals of the
Ecosystem Approach to Fisheries (EAF) and other ecosystem-based
fishery management frameworks (Mangel et al., 1996; FAO, 2003a;
Sinclair and Valdimarsson, 2003; Fogarty, 2013). However, it has
been an explicit policy requirement only from a biodiversity conservation (CBD) perspective, and there has been little elaboration on its
operational implications for fisheries. The question now is whether
and to what extent BH could provide a fishery response to the emerging cross-sectoral concern over maintaining ecosystem structure
and, by consequence, function.
There has been substantial work on ecosystem structure, for
example, on species assemblages and predator–prey relations,
from the early work of Larkin (1966), Andersen and Ursin (1977),
Dickie (1979), or Pimm and Rice (1987) to the substantial developments on multispecies virtual population analysis (Helgason and
Gislason, 1979; Pope, 1979). However, with few exceptions—
notably Sainsbury (1988)—the problems considered concerned
mainly the impact of these relations on the dynamics of single populations, the resulting biases in conventional stock assessments, and
the validity of the predictions used as basis for scientific advice on
fisheries management and stock rebuilding. Attention of multispecies harvesting strategies is much more recent, but developing
rapidly (Smith et al., 2013; Blanchard et al., 2014; Fulton et al.,
2014). Calls have also been repeatedly made in the last decade, to
protect top predators (e.g. Heithous et al., 2007) or better manage
the populations of forage fish species needed by predators, including
mammals and seabirds (Pikitch et al., 2012). The approaches did not
consider the maintenance of the overall ecosystem structure and
function as such, nor the impacts on total biomass of harvest
across exploited species. Thus, while helping to sound the limits
of conventional single-species management and proposing corrective action, they did not step really into a more squarely integrated
ecosystem approach to fisheries. More recently, the developing literature of EAF and EBFM (e.g. FAO, 2003a; Fogarty, 2013)
propose explicitly to maintain the basic structural elements of the
ecosystems within specified stochastic bounds. However implicitly,
they still make ecological considerations the primary determinant of
harvesting strategies, with issues such as food security as subordinate at best.
BH fits into EAF or EBFM frameworks, particularly with its aim
of maintaining the age/size structure and species composition of
S. M. Garcia et al.
exploited ecosystems. It may tangentially touch on habitat conservation as well, if living habitat structures (coral reefs, seagrass beds,
etc.) are considered as part of the species assemblage and food
chain—but these issues have not been touched on yet. In terms of
functions, BH addresses indirectly (through the structure) natural
productivity (where “natural productivity” takes into account recruitment, growth, and natural mortality—including predation
mortality), as well as fisheries production and the trophic chain.
By contributing to a reduction in age structure truncation, BH
touches also tangentially addresses population and ecosystem resilience to climate oscillations and change (Garcia et al., 2011, 2015;
Burgess et al., 2015). It does not pretend to directly address other important, possibly related functions of energy and biogeochemical
cycling and primary production, ecosystem regulation and evolution (ecological successions) or carbon sequestration, and other services of a recreational or cultural nature.
The implicit assumption in a BH management strategy is that
maintaining structure will also maintain ecosystem function, and
that rebuilding structure will improve or re-establish function.
However, the relation between ecosystem structure and functions,
and the resilience of these functions to changes imposed by
fishing, are complex, fuzzy, not well known and partly unpredictable
(NMFS, 1999; Chapin et al., 2000; Rosenfeld, 2002; Cortina et al,
2006; Schindler et al., 2010). The literature related to EAF and BH
does not address the issue explicitly, although some steps in this direction are being taken (cf. Cury et al., 2011; Rice, 2011; Essington
et al., 2015).
The relation between structure (biodiversity) and function (processes and services) is therefore neither simple nor intuitive and will
need to be further addressed.
BH and selectivity
The challenge is being faced in implementing some policies with
strong foundations in ecosystem functions and services (ICES,
2014). However, conventional fisheries management strategies are
systematically selective at a stock/population level with a typical approach aiming (i) to protect all fish stocks until they are mature (on
average) and spawn at least once, and (ii) above that age/size, for the
populations to be fished at or close to their MSY level of abundance
(in line with the LOSC. This requirement applies to target species
but applies, though less specifically prescribed, to associated and dependent species for which reproduction should not be threatened).
In reality, conventional fisheries are at best as imperfectly selective as
illustrated by the recurrent problems and debates on bycatch and
discards (Hall, 1996; Nielsen and Mathiesen, 2003; Catchpole
et al., 2005; Suuronen et al., 2007), but even if selectivity were
perfect, functionality considerations do not extend beyond the targeted species’ productivity. In contrast, BH proposes to distribute a
moderate fishing pressure on ALL usable sizes and species within
normative boundaries to be determined by the authorities concerned (see Garcia et al., this issue). Thus, BH is comparatively
“unselective” but at an ecosystem level.
That aspect of non-selectivity has led to the common misconception that under BH, all fisheries will be asked to, or allowed to, operate
unselectively is common (see, for example, FAO, 2014a, b: 137, 139).
Indeed, it has sometimes been argued that under BH, all vessels would
have a “license to kill” everything in the fishing path.
The concern arises because the proposal to spread fishing pressure on a larger range of species and sizes in the ecosystem is mistakenly applied to every single fishery/vessel/gear and envisioned
as an obligation. However, this is unnecessary from a BH
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Balanced harvesting in fisheries
perspective, as it is the aggregate results across all fisheries that is important. In addition, truly unselective fishing would not make ecological sense because in communities of fish with life histories that
vary by even a moderate amount, such indiscriminate fishing
would not be balanced with productivities. From a fisher perspective, non-selectivity at an individual level is unlikely to make business sense as individual fishing practices will need to be selective
to allow fishers to reduce unwanted bycatch and waste, and, at
least in commercial fisheries, to maintain economic viability.
An analogy might be made between fishers harvesting species and
sizes in proportion to their natural productivity, under BH, and the
situation of natural predators in the ecosystem. Each natural predator
has its preferred preys, and selects them according to their availability,
balancing energy costs and benefits (Ivlev, 1961). Together, however,
the set of natural predators preys on all the available species/sizes,
along the entire food chain, imposing on all preys a natural mortality
rate which, on average, is equal to their natural productivity (Caddy
and Csirke, 1983; Caddy and Sharp, 1986; Jacobsen et al., 2014), generating the classical linear size spectrum describing the distribution of
particle sizes in the ocean (Sheldon et al., 1972). Under a BH approach,
each fisher or fleet/métier operating in an ecosystem will have its own
preferences (targets) while the requirement collectively is to harvest
species and sizes in proportion to their productivity, replacing a part
of the natural mortality by fishing mortality. Of course, this will not
likely happen naturally. As an emergent new property of a complex
system, it may be that the fishery sector will seek to optimize its own
operations (e.g. expanding the spectrum of species sought by existing
métiers, creating new multi-purpose métiers, and coordinating harvesting strategies across métiers), but there will likely be a need for considerable management intervention to achieve precise BH results.
BH and protection of juveniles and spawning sites
Two classic ingredients of fisheries management are the protection
of juveniles and the protection of spawning fish in an exploited fish
population. Conventional fishery management theory calls for
leaving juveniles in the water, as a good investment in future yield
as long as growth is higher than mortality. In contrast, in BH
theory and modelling, the aim is not to protect juveniles until
they reproduce, but rather to exploit juveniles, along with other segments of a fish population, proportionally to their productivity.
While BH results indicate this spreading of fishing mortality more
broadly across fish sizes will improve aggregate yield and provide
other ecosystem benefits (e.g. reduced genetic drift, increased resilience; Zhou et al., 2010), it will lead to juveniles being more highly
exploited than is typical under conventional fishing.
Although this indicates a contrast between BH and conventional
harvesting strategies, it does not imply that, under BH, the protection of juveniles would become superfluous. Even if the size range
was broadened, the exploitation rate on each size would still need
to be limited to that corresponding to natural productivity.
Achieving the precisely optimal level of exploitation of juveniles
(and indeed of other age/size classes) is unlikely to occur with unrestricted fishing, but rather would require some regulation, including gear restrictions, quotas, and closed areas, the implications of
which are not trivial. Modellers are still debating as-yet-unresolved
issues of the size at which productivity per recruit is maximized and
potential overcompensation in size-based models (e.g. Burgess
et al., 2015), but in any case, there is certainly a need for sufficient
escapement of juveniles to maintain the stock, even if the best way
to achieve it will be case-specific, while attempting to balance harvesting on common sizes. Particular attention will need to be
paid, in any case, to the special requirements of long-lived, slowmaturing, and low fecundity species (Enberg et al., 2009; Heino
et al., 2013) and the management measures to meet these requirements.
Evaluating harvesting strategies
The choice of a harvesting strategy is a key ingredient of fisheries
management, and therefore, how such strategies are assessed and
compared is critically important. To date, this assessment and comparison, between BH and other strategies, has relied on a series of
modelling exercises. These include models focused on the flow of
biomass through sizes (e.g. Law et al., 2012, 2013; Jacobsen et al.,
2014), species communities (Rochet et al., 2011), trophic levels
(Bundy et al., 2005), and complex models of the entire ecosystem
such as Ecopath and Atlantis (e.g. in Zhou et al., 2010; http://
atlantis.cmar.csiro.au/).
Different challenges are encountered in using different models,
individually and collectively, to explore fishing and management
strategies for particular ecosystems (itself a greater challenge than
in examining fishing strategies for a single-species stock), whether
balanced or unbalanced. Some of the models used for comparing
BH with other strategies consider trophic interactions between
species across the foodweb, and do not impose or maintain constant
growth, mortality, and stock recruitment relationships, making
them—to some extent—more realistic than most conventional
fishery science models. However, the models used to explore BH
often achieve their breadth of treatment at a much higher cost in
model complexity, data and parameter requirements, number of
assumptions, and fitting difficulties, compared with an individual
single-species fishery model. (One could alternatively compare
model complexity in BH analyses with the aggregate of all singlespecies fisheries models relevant to all harvesting undertaken in an
ecosystem.)
A concern about the models underpinning the BH concept and
related management implications is that they cover only fish species,
while omitting molluscs, crustaceans, etc. It is true that some
foodweb models may indeed only represent a subset of species
and/or sizes, but also some size- and trait-based models do not
deal directly with species at all. Rather they account for life history
diversity to investigate the effect of fishing on “animals” with different asymptotic sizes (e.g. Andersen and Pedersen, 2010). This is
fitting since the analyses (like BH itself) are meant to consider harvesting across the entire food chain (including all species, stocks, and
sizes in the ecosystem) with “productivity” (as in the BH definition)
being the rate at which biomass (in all forms) flows through the food
chain (and its sizes, species, communities, or trophic levels).
The initial 2010 meeting on BH (Garcia et al., 2012) found that
there was general agreement of all the models used to evaluate harvesting strategies, with respect to the key aspects of BH. However, a
more recent 2014 meeting (REF) has shown that the debate is not
closed and further studies are needed to fully understand the
strengths and weaknesses of the various models in investigating
how to harvest an ecosystem (Garcia et al., 2015).
BH and the management of individual species
A key component of the BH analyses carried out to date have been
based on size-based modelling (Garcia et al., 2012, 2015; Law
et al., 2012; Jacobsen et al., 2014) creating the impression, for
some, that species, per se, are not considered relevant under BH
(or specifically that BH might aim to remove a defined proportion
of the biomass of each size class of fish, regardless of species). If
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that were the case, there would be enormous implications for fisheries management. It must be emphasized, therefore, to examine the
role of individual species in the concept and analysis of BH.
Keeping in mind that BH aims to remove a proportion of the
biomass of each component of the ecosystem structure, with the proportion directly related to the productivity in aggregate of that component, the set of existing BH models take varying approaches to
how ecosystem components are defined—whether by size, species,
or tropic levels. Perhaps the most “iconic” modelling representations of BH are based on the size spectrum (e.g. in Garcia et al.,
2011, 2015, this issue; Kolding and van Zwieten, 2011, 2014; Law
et al., 2013). Within these models, BH removes a proportion of
the biomass of each size class in a foodweb, with this proportion
related to the size class productivity in aggregate, not productivities
of each “species” present in the size class. In these analyses, individual species are not considered. On the other hand, in the size and
trait-based models used by Andersen and Pedersen (2010) or
Jacobsen et al. (2014) and in these models, the systematic “loss” of
functional types (proxies for “species”) would show up in the performance of the models. Moreover, species and communities are explicit components of complex ecosystem models also used to
explore BH implications (e.g. Bundy et al., 2005; Zhou et al.,
2010; Rochet et al., 2011. See also point iii, above). Finally, in presenting empirical evidence from African lakes, Kolding and van
Zwieten use classical fishery landings and scientific survey data—
by size and species—to generate BH-like diagrams that contain
both, simultaneously.
The BH concept, therefore, does not disregard species, and much
of the modelling work on BH is exploring the question of how, in
practice, sizes and species or trophic levels will be jointly considered
in a management system. Thus, it is essential to include a diversity of
treatments of species, sizes, and traits in the modelling. An important point of discussion (and of uncertainty) in that respect is,
indeed, the necessary two-way articulation between the size and
species data, aggregating them for ecosystem-scale assessments
and disaggregating back the ecosystem-scale results stemming
from these assessments in species-relevant and fishery-specific
advice and regulation. This issue is only beginning to be addressed
and requires operations research and cost–benefit analyses. It
seems likely that the collection of both sizes and species would
need to continue for use in any form of nested assessment processes,
at annual level for operational fishery stock assessments and at
multi-annual level for more strategic ecosystem-level assessments.
The African examples mentioned above have emerged in fisheries
without any science backup and top-down management, but it is
not realistic to assume that similar outcomes will emerge without
active management and “balancing” incentives in modern, marketdriven, fishery systems in which different prices for species and sizes
strongly influences the distribution of fishing pressure (see Charles
et al., this issue).
BH and fish discarding
Discards have been a long-standing problem in fisheries, with
impacts on food security and fishery revenues, ethical issues
around the waste of natural production they represent, and
impacts on fish and fishery assessments—by increasing uncertainty
when assessing how fisheries are affecting target and non-target
species. In addition to attempts to improve selectivity of fishing activities, discard bans and restrictions have been actively considered
as management measures to solve these problems.
S. M. Garcia et al.
It has sometimes been speculated that, in striving to broaden the
range of sizes and species impacted by fisheries under BH, one
means to accomplish that would be by allowing discards (or equivalently, by removing existing discard bans). This, it is suggested,
would lead to greater mortality on undesired sizes and species
than if fishers had incentives (e.g. through discard bans) to avoid
such mortality.
In terms strictly of producing mortality on a range of species and
sizes, it is true that it does not make any difference whether the fish is
landed and eaten or discarded at sea, dead. However, several points
arise. First, as noted above, discarding implies a waste of resources,
so bans may be implemented to reduce waste, promoting better use
of currently “unwanted” species, an ethical and utilitarian requirement in conventional fisheries management, and one of the motivating considerations behind the interest in BH. Second, BH requires
accurate accounting of what has been killed to assess the distribution
of fishing pressure on ecosystem components, just as single-species
assessments require accurate data in fish killed to calculate fishing
pressure on the target (and bycatch) species. Thus, discard bans
may be needed to ensure the collection of comprehensive catch
data as well as to monitor management performance. Indeed, accurate catch data are needed for any management system, so whether or
not discard bans are an effective tool to improve catch reporting
remains a valid question both for conventional management and
BH. Finally, discard bans may also be promoted in conventional
management to increase their cost to industry and indirectly
prompt bycatch-reducing innovations of the industry (cf. Borges,
this issue). This expectation might not be satisfied however—even
under conventional management—if economically better and
acceptable alternatives are found by the industry.
BH, emblematic species, and ecosystem services
Since BH inherently involves a broader than conventional range of
sizes and species contributing to the catch, the question arises as to
exactly what should be included in the harvesting. Concern has been
expressed about ecological and social impacts if BH were used to legitimize harvest of currently unused ecosystem components, such as
some marine mammals or seabirds, or underused small forage
species needed by predators including mammals and seabirds.
The concern is genuine, but the information available is conflicting.
With respect to forage fish, Smith et al. (2011) stress the risk of
overexploiting forage fish, particularly in “wasp-waist” ecosystems
where a large part of the plankton production is funnelled
through a small number of low trophic level species to higher
trophic levels. They indicate that there is a tension between achieving broader goals of protecting and maintaining biodiversity (including ecosystem structure and function) and global food
security. This differs from the case of African lake fisheries (in
Kolding and van Zwieten, 2011, 2014) where broadened fishing
strategies produce higher yields and maintain ecosystem structure,
so such differences need to be resolved. Certainly, since BH aims
to balance the needs of preys and predators, using all components
in proportion to their productivity, this should ensure that there is
enough food available for predators. A component of “productivity”
is survivorship from age to age, and predation mortality is inherently a component of the survivorship. This is part of the assessments since, under BH, both predators and preys are reduced
proportionally along the whole trophic chain.
Potential problems would emerge, however, in cases where some
top predators, such as large mammals, are protected, i.e. not
included in the widening of species being harvested under BH.
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Although the predation mortality of such species would still be
included as a part of the productivity of the species/sizes of their
prey, truly balancing the additional fishing mortality, with some predators excluded from the BH framework, would be an additional
challenge to implementing BH, one that would not be straightforward. Indeed, if such excluded predators were severely depleted
but recovering, and their future needs are not taken into account
in deciding about exploitation rates of their food items by humans,
this could result in a overharvesting of prey species. Thus, care will
be needed if BH is implemented, to determine how to best “distort”
a BH strategy on both ends (its largest and smallest species)—
although the risks involved might actually be lower than under conventional management, in which predator–prey relations are often
not accounted for at all.
Ultimately, it is crucial to recognize that any implementation of
BH in practice would have to best meet the mix of societal goals for
the specific fishery and the ecosystem overall. This might include
prohibitions on harvesting certain species (e.g. mammals, forage
species, or other iconic species) and/or size ranges, as societal
choices (see also the section on partial implementation below).
Specifically, it has been noted, in the various discussions on BH,
that BH parameters (e.g. the reference and target situations and
the species and size boundaries) are a societal prerogative [The
Malawi Principle N81 states that the objectives of management of
land, water and living resources are a matter of societal choices
(CBD Decision V/6, 2000). This principle is also reflected in the
EAF Guidelines (FAO, 2003a)] to be decided upon case by case
(cf. Garcia et al., this issue). This reflects already-existing practice
in fisheries management of restricting or regulating the catch of nonfishery mammals and birds—notably through bycatch management,
using bycatch quotas, discards bans, etc. Economic innovations such
as payments for ecosystem services (PES) and offsets are still in early
stages of policy discussions, but might be relevant here as well.
BH and implementation costs
If BH were to be implemented, then to deliver the desired balanced
outcome at the ecosystem scale, there is likely to be a need for
fishery-based management targets for separate fisheries and fish
stocks (revisited every year or every few years for multiyear management plans), nesting the fishery-related targets in a more strategic
layer of ecosystem-based targets. The fishery-related management
targets may function much the same as under contemporary management, but their derivation will be a process of first estimating
ecosystem-scale management targets and then, when needed, disaggregating them to species targets—a logical sequence that will be
more complex, not simpler.
This would need to be carried out within a framework of multiple
management objectives that is typical in fisheries. The CBD objective of maintaining ecosystem structure and function (the primary
goal underlying BH) is added to MSY-based goals highlighted in
the 1982 Law of Sea Convention (LOSC) and the 1995 UN Fish
Stocks Agreement, as well as a range of social and economic objectives. Note that although the MSY-related goals have been often unrealized, the CBD goal is certainly not easier to achieve—being
equivalent to maintaining all the stocks in an ecosystem close to,
but below, the maximum yields they can sustain, taking predator–prey as well as life history dynamics into account. Seen from
that angle, BH can be viewed as a re-expression of the LOSC requirement for MSY (i.e. harvesting proportionally to productivity),
extended explicitly to the ecosystem, rather than selected species individually, and not explicitly requiring that the standard be the
maximum yield available from the ecosystem; only that it be a sustainable yield.
The challenge of meeting these multiple objectives in a complex
multilayered system has significant implications for management
costs under BH. On the one hand, the expected need to add
another strategic layer to conventional management, to meet BH
systemic goals, is unlikely to reduce costs. On the other hand, a reduction in costs could arise through the system-wide coordination
resulting from a BH approach, if: (i) laws, regulations, and tasks can
be linked across species, rather than as at present, being usually set
independently for each target species and métier, with a subsequent
ad hoc and often difficult coordination and reconciliation across
métiers (Kraak et al., 2012); or (ii) there is a progressive adaptation
of conventional management and layered fishery systems into a
more coherent ecosystem-based fishery system. At this stage, this
remains a speculation, although a more comprehensive discussion
of the economic aspects of BH implementation are found in
Charles et al. (this issue).
Related to management costs are the costs involved in performance assessment. These might be reduced under BH, if there is a “systemic” simplification of the fishery management and exploitation
systems, and hence of the monitoring and assessment parts of
these systems. However, as discussed above, the features to be considered in a BH implementation plan are likely to be more complex
than merely monitoring size composition, so a simple performance
evaluation using a single ecosystem structure norm, such as size
spectrum, would probably not be sufficient. In any case, it remains
to be seen how a coordinated evaluation of the performance of the
aggregate fisheries against a modest suite of outcome targets compares in complexity and cost with separately assessing and then aggregating the individual performances of all fisheries in an
ecosystem. It is also unclear whether the signal/noise ratio of the
data used for the assessment will be sufficiently large to allow for a
meaningful interpretation of extent and direction of changes in
the situation. Certainly, translating the overall performance of the
sector (for an entire ecosystem) to a set of performances for the different component fisheries—which will indeed remain the object of
management—might not be simple.
Analogously, at the operational level of the fishery system, there
arises the question of how BH would affect fishing operations. This
depends very much on how BH would be implemented (Charles
et al., this issue), e.g. whether there would be a reduction in the
number of management rules, such as technical measures, to
follow within the management system, or whether BH will automatically reduce the selectivity burden of each vessel. A cost-increasing
aspect would be the need for acquisition by operators of a range
of fishing skills, multi-purpose vessels (or fleets), and portfolios of
quotas/species, which may shift in response to the performance of
other fleets. In contrast, adoption of the BH approach might
trigger new strategic developments in technology, practices, fleets
organization, and consumption patterns that will reduce the
burden, optimizing costs/benefits. This scenarios are explored in
more detail in Charles et al. (this issue). The transition to such a
system may not be easy, however, as measures implemented to
achieve change may have many consequences that must be integrated (Bastardie et al., 2010; Dickey-Collas et al., 2010; Kraak
et al., 2012; Eero et al., 2014).
BH and ecosystem rebuilding
Fisheries management invariably faces issues of the timing of management measures, and indeed the order of their implementation.
1674
For BH, it has been argued that it would make little sense to attempt
to implement BH in a fishery system, in which many important
resources are already overfished (a rather frequent situation), until
those overfished stocks have been rebuilt. The argument, then, is
that stock rebuilding should occur before a shift in overall harvesting
strategy, to BH.
In evaluating this matter of timing, one must first note that
rebuilding of fish stocks is a sine qua non-condition not only of
the LOSC, but also of the CBD requirements. The CBD goals do
not call for the structure of the ecosystem to be kept in whatever
state it might be at present, so ecosystem rebuilding may well be
needed. Furthermore, for depleted stocks, the LOSC requirement
for rebuilding to the level that could produce MSY is not only a stockspecific requirement but also one that makes sense in ecological
terms (e.g. for resource stability and ecosystem resilience) and socioeconomic sense (e.g. for sustainable use, livelihoods, and food security) and is thus relevant also to CBD goals and BH.
Given this, what is the best timing for stock rebuilding? And for
shifting to BH if desired? At what point in rebuilding of stocks does
BH become relevant, or conversely, could a rebuilding strategy
across a set of individual stocks be coordinated for the entire
fishing sector, across a number of fisheries/métiers, and aim to
meet BH goals overall?
For an ecosystem with multiple depleted stocks, or whose structure has already been altered by highly selective fishing, planning for
a recovery coordinated across stocks and métiers will be complex.
Implementing coordinated recovery plans might be done efficiently
if the governance system is designed to take advantage of opportunities of synergies and trade-offs that might arise across the sector and
the ecosystem. This is unlikely to occur under conventional fisheries
management, within which externalities are superimposed in ad hoc
ways on single-species/métier management. Indeed, in a complex
social –ecological system in dynamic evolution, a piece-meal approach might be the worst solution. A more ecological and economic systemic governance, perhaps induced by a shift to BH, might
provide the vehicle for more efficient solutions. In summary,
then, while the precise nature of rebuilding targets for ecosystem
structure and function remain to be defined, the need for them
follows from the LOSC and CBD requirements on protecting structure and function seriously, and this implies a coordinated interaction with the rebuilding of individual stocks.
Discussion and conclusions
Balanced harvesting has not yet been implemented in any modern
fishery management system. The only examples available are
small-scale inland fisheries in Africa, which have “naturally” developed near-BH systems under traditional governance and weak
central management. The discussion on BH management implications is therefore, by necessity, conceptual in nature, influenced by
our assessments of conventional management experience, and
subject to difficulties in projecting oneself into systemic frameworks
for the management of complex systems.
Some of the issues addressed in this paper stem from a confusion
between the BH concept as encapsulated in the definition given in
introduction and its translation in the models used to investigate it.
Others stem from genuine concerns about potential management
complexity (and costs) as well as conservation issues regarding specific ecosystem components (e.g. emblematic or forage species). The
abundance of issues raised suggests that prospects for adopting and
implementing BH right away are highly limited. However, it is clear
that the uneven performance of contemporary fishery management
S. M. Garcia et al.
(Worms et al., 2009; Ye et al., 2012; FAO, 2014a, b), the increasing
efforts made to bring biodiversity considerations into fishery management (Garcia et al., 2014), and the overall decline in marine biodiversity, where fishing has played a large role (UNEP, 2012;
Secretariat of the CBD, 2014), all call for alternatives to the status
quo. The CBD requirement to maintain ecosystem structure and
function is a case in point. This is the already-existing background
against which the new contributions on BH are produced, and
against which the potential implications of its implementation
can be explored.
Examining the general principles, challenges, and commitments
of modern, ecosystem-based fishery policies and management
systems indicates that BH could be part of them. More can be
learned about compatibilities or conflicts with thorough case-bycase study of a range of fisheries in different ecosystems. Certainly,
there appear strong indications that economic factors will be very
significant barriers to introducing BH, at least in a complete form
(Charles et al., this issue). In any case, it is advisable to have an
open and structured discussion on BH-related concerns by all stakeholders, from both the fishery and biodiversity conservation as well
as theoretical and operational points of view and this special issue is a
step in that direction.
The starting point is that we are looking for a way to meet the
CBD norm to maintain ecosystem structure and function—which
requires adaptation of the conventional fishing regime at ecosystem
and trophic chain levels—while, at the same time, meeting the LOSC
norm to maintain stocks at the level at which they could produce MSY.
It would be very convenient if there were ways to meet the CBD requirement just managing perfectly at MSY, using conventional
management, or to meet the LOSC requirement using only biodiversity conservation measures. Considering the stormy history
of fishery and conservation governance, most practitioners would
probably consider that neither of these paths is viable (Garcia
et al., 2014). Could therefore the two approaches be implemented
in a coordinated manner, finding synergies, transparently facing
trade-offs, and overall reducing risks to resources, livelihoods, and
food security?
If BH were to be implemented, it is likely to initially require the
use of generic, conventional instruments and approaches such as:
fishing capacity control; good governance; resource allocation measures; fishing rights; and institutionalized performance assessment.
However, new questions arise in relation to these. For example,
could a system of allocation of sizes and species be conceived?
Could fishing rights be organized in coordinated portfolios to
reach ecosystem outcomes? How should conventional technical
measures—related to mesh sizes, gear design, fishing operations,
spatio-temporal restrictions, and habitat protection—best be
applied in a BH context? What would be the role, if any, of
minimum landing size regulations? How best would responsibilities
be distributed between the State and other stakeholders, particularly
industry?
Relating to these questions is the possibility of a “partial implementation” of BH. This was briefly discussed in Garcia et al.
(2015) and is addressed in more detail in Charles et al. (this
volume). A partial implementation would reflect a compromise in
reducing the burden, costs, and difficulties of BH implementation,
by reducing the scope (fisheries, species, and sizes concerned) or the
level of precision required in meeting the norm. This could involve
narrowing down the BH boundaries, and/or excluding some species
or sizes from the BH framework (as discussed earlier). The consequences of this on expected fishery and conservation outcomes
Balanced harvesting in fisheries
are still to be examined. Would a partial implementation of BH
partly achieve the CBD goal, or might it actually be worse than the
status quo, increasing conservation risks or economic costs faster
than it provides ecosystem-scale benefits? To what extent can we
omit certain species and sizes (or even fisheries) from the BH framework before losing benefits or facing unpredictable management
consequences? The point on partial implementation also raises
the need to look at the coherence between conservation and sustainable use regulations (e.g. between the used and protected ranges of
sizes and species) to fulfil the CBD requirement. These questions
have been raised, but responses are still to be explored.
More broadly, there may be a need for a formal re-definition of
management units, at a higher, more ecosystem-based level than
the present ones, perhaps not to replace them, but to nest them at
an ecosystem level. In the case of ecosystems (and food chains)
“shared” by two or more countries, the frameworks available to
manage shared and straddling stocks will need to be implemented
at the right scale. In that context, implementation would be particularly complex for highly migratory top predators, including
seabirds, tunas, and mammals. These feed at the top of many
spatially different trophic webs at different times during their
large-scale migrations, and therefore present, in each of their migration sites, a biomass that is not in direct relation with the base of the
food chain at that site. Elaborating and using a BH norm under such
conditions would require collaboration across large parts of the
ocean (e.g. between regional fisheries management organizations
and between them and single States). In addition, in large oceanic
ecosystems, only large predators are currently used to any significant
extent and balancing the exploitation would be very challenging
(e.g. Would the development of massive exploitation of mesopelagic
fish—to rebalance currently skewed exploitation patterns—make
economic and ecological sense?). Such ecosystems represent probably the largest challenge for BH from the research and institutional
points of view.
Economic aspects will also have a major impact on BH implementation. This is discussed in detail in the paper by Charles et al.
(this issue), where we think the present range of species and sizes
caught in fisheries is largely a result of four major forces: regulations,
markets, technology, and societal preferences. If broadening the
range of species and sizes caught in fisheries is the BH goal, then
addressing these forces will be important. For example, if BH
requires the harvesting of species (and sizes) either not currently
desired in markets or not currently feasible technologically to
catch, the question is how to alter the situation. Essentially some
form of incentive is needed, since a reasonable premise is that
fishers will not want to catch a species of no market value, or for
which a large investment in new technology is needed, without a
subsidy (defined broadly) or other incentive. For example, if there
were a focus jointly on the ecosystem benefits of BH and on the
human goal of meeting food security needs, then in the absence of
market demand for low-price species, a subsidy (or equivalently,
an incentive such as an allocation of fishing rights) could be used
to broaden the species composition of catches, by influencing the
market and consumption patterns. Subsidies, though not the only
possible tool, may help towards better ecosystem structures if
designed with due attention to potential perverse effects.
Shifting to a BH approach will also require some pre-analysis of
various transitional pathways from the present unbalanced state to a
balanced one (Figure 1, top panel), considering the benefits, the
costs, and their distributions on the agents concerned, particularly
the most vulnerable ones, the research and institutional capacity
1675
available, and operational time frames. It will also require the consolidation of the present flow of data collection, assessment,
advice, and decision in a two-way rescaling framework allowing
for consolidation (upscaling) of stock-specific analyses at ecosystem
level and the differentiation (downscaling) of ecosystem-wide analyses to the relevant fishery operations level (Figure 1, bottom
panel).
While some of these challenges relate particularly to BH, most
have a much broader relevance. They are challenges that will be
encountered, in some form, by any other ecosystem approach to
fisheries and biodiversity conservation. They are the challenges inherent in reconciling the fisheries norms of the LOSC and the UN
Fish Stock Agreement (FSA) with the biodiversity conservation
norms of the CBD and related policies (Garcia et al., 2014). BH
might present an opportunity as a single coherent norm under
which such a reconciliation can be sought—an opportunity not provided by any small adjustment to either conventional fisheries management (fully rooted in the LOSC and FSA, while trying to
accommodate biodiversity) or to conventional biodiversity conservation (fully rooted in the CBD and trying accommodate directed
exploitation).
BH is also compatible with the goals of the Ecosystem Approach
to Fisheries (EAF) and could be nested into that broader framework.
Indeed, as noted earlier, BH grew out of a desire to achieve the CBD’s
goal—related to the Ecosystem Approach—of maintaining ecosystem structure and function, and may provide a suitable framework
to reflect it in operational management. At the same time, the EAF
guidance, in particular on impact mitigation, ecological risk assessment, and good governance, provides a framework for implementing a BH strategy.
Figure 1. Schematic representation of the processes involved in the
transition from conventional (fishery-based) management to BH
(ecosystem/sector-based) fishery management. (Top) Multiple
trade-offs and transition pathways needed to re-balance fisheries;
(Bottom) two-way rescaling of research and governance between
strategic and systemic assessment and management and tactical
operational implementation.
1676
Operationalizing BH in an Ecosystem Approach to Fisheries
management (FAO, 2014a, b; Garcia et al., 2015) would require
nesting two interacting processes: a strategic, ecosystem-based
adaptive process with medium to long cycles (5–10 years), providing the over-arching framework, and the more conventional, singlespecies, short-term operational process. Adopting this approach
(already required for implementing the EAF anyway) implies a
shift away from many conventional ideas and implementation
“reflexes”. This may have positive results, but on the other hand,
caution is needed to avoid an over-enthusiastic (and misguided)
sense that BH provides the management solution to all ecosystem
issues in fisheries. It is also possible that fishing operators may see
BH as a solution to their operational headaches (which is unlikely)
or as a new regulation nightmare (which is possible but certainly
to be avoided). The new management challenge for the State
would be to foster innovation at the fishery level and coordination
at the ecosystem level, while focusing on setting and monitoring
strategic goals, leaving the operational details to industry under
co-management. Even broader cross-sectoral frameworks like the
generic Ecosystem Approach (EA), integrated coastal areas management (ICAM), marine spatial planning (MSP), or Ecologically
Sustainable Development (ESD) [Cf. Australian Environment
Protection and Biodiversity Conservation Act 1999 (EPBC Act)]
require balanced management of risk across multiple sectors (including fisheries) and hence an understanding of the impact of
non-fishery stressors on ecosystem structure and function. BH
could be nested in these frameworks, within EAF.
It is too early to have definitive answers and a major intent of this
article was to ensure that a wide range of fisheries management questions and concerns are made explicit, and to provide an analytical
framework that can benefit subsequent dialogue (and supporting
research) aimed towards answering those questions. There is
much more work to be done in studying BH, or more broadly, fisheries impacts on aquatic communities and food chains. Discussions
are still proceeding about the contributions that the various forms of
modelling are bringing to the issue (Garcia et al., 2015). Empirical
experience is generally missing, apart from cases that may or may
not be widely generalizable (e.g. in Kolding and van Zwieten,
2011, 2014). Furthermore, the fisheries management landscape is
facing epochal changes, through a range of new instruments—
such as increased spatial management, use-rights systems, ecolabels, PES, and possibly biodiversity offsets. This is taking place
in a context of ever-increasing ambition in terms of what science,
management, and policy are asked to achieve, from sustainability
in single-species management of increasing numbers of species to
multispecies management, and now to a more integrated ecosystem
goal for management. The CBD requirements move the bar up yet
again for both research and implementation, with BH a new area
for exploration. The dialogue about BH needs to be further
pursued, together with further analysis, particularly from the biodiversity conservation arena, and across multiple disciplines, to
further understand and clarify the implications of BH, before realworld implementation could be advised.
Acknowledgements
We would like to express our grateful thanks to Matthew Burgess
and the two anonymous reviewers for their useful and sometimes
challenging comments and suggestions which have significantly
helped in improving the document.
S. M. Garcia et al.
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Handling editor: Steven Cadrin