Fisheries
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A Resilience Approach Can Improve Anadromous
Fish Restoration
John Waldman, Karen A. Wilson, Martha Mather & Noah P. Snyder
To cite this article: John Waldman, Karen A. Wilson, Martha Mather & Noah P. Snyder (2016) A
Resilience Approach Can Improve Anadromous Fish Restoration, Fisheries, 41:3, 116-126
To link to this article: http://dx.doi.org/10.1080/03632415.2015.1134501
Published online: 24 Feb 2016.
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FEATURE
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A Resilience
Approach
Can Improve
Anadromous Fish
Restoration
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John Waldman
Biology Department, 65-30 Kissena Blvd., Queens College, Queens, NY 11367, and Biology and
Earth and Environmental Sciences Ph.D. Programs, Graduate Center, The City University of New
York, NY. E-mail: john.waldman@qc.cuny.edu
Karen A. Wilson
Department of Environmental Science and Policy, University of Southern Maine, Gorham, ME
Martha Mather
U.S. Geological Survey, Kansas Cooperative Fish and Wildlife Research Unit, Division of B
­ iology,
Kansas State University, Manhattan, KS
Noah P. Snyder
Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA
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Most anadromous fish populations remain at low levels or are in decline despite substantial investments in restoration.
We explore whether a resilience perspective (i.e., a different paradigm for understanding populations, communities,
and ecosystems) is a viable alternative framework for anadromous fish restoration. Many life history traits have allowed
anadromous fish to thrive in unimpacted ecosystems but have become contemporary curses as anthropogenic effects
increase. This contradiction creates a significant conservation challenge but also makes these fish excellent candidates
for a resilience approach. A resilience approach recognizes the need to maintain life history, population, and habitat
characteristics that increase the ability of a population to withstand and recover from multiple disturbances. To evaluate
whether a resilience approach represents a viable strategy for anadromous fish restoration, we review four issues: (1) how
resilience theory can inform anadromous fish restoration, (2) how a resilience-based approach is fundamentally different
than extant anadromous fish restoration strategies, (3) ecological characteristics that historically benefited anadromous
fish persistence, and (4) examples of how human impacts harm anadromous fish and how a resilience approach might
produce more successful outcomes. We close by suggesting new research and restoration directions for implementation
of a resilience-based approach.
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Un enfoque de resiliencia puede mejorar la recuperación de peces anádromos
La mayor parte de las poblaciones de peces anádromos se encuentran en niveles bajos o están declinando pese a las
sustanciales inversiones que se hacen para su recuperación. En este trabajo se exploró si la perspectiva de resiliencia (i.e.
un paradigma diferente para comprender a las poblaciones, comunidades y ecosistemas) consituye un marco conceptual viable para la restauración de peces anádromos. Muchos atributos de su historia de vida han permitido a los peces
anádromos florecer en ecosistemas no impactados, pero a medida que los efectos antropogénicos se incrementan, dichos
atributos se vuelven en su contra. Esta contradicción genera un importante reto de conservación, pero también convierte
a estos peces en excelentes candidatos para ser estudiados bajo el enfoque de la resiliencia. Este enfoque reconoce la
necesidad de mantener las características de la historia de vida, la población y el hábitat para incrementar la habilidad
de la población para soportar y recuperarse ante múltiples disturbios del ambiente. Con el fin de evaluar si el enfoque de
resiliencia representa una estrategia viable para la recuperación de peces anádromos, se hace una revisión de cuatro aspectos: (1) cómo la teoría de resiliencia puede brindar información sobre la recuperación de peces anádromos, (2) cómo el
enfoque basado en la resiliencia resulta fundamentalmente diferente de las estrategias actuales de recuperación de peces
anádromos, (3) las características ecológicas que históricamente ha beneficiado la persistencia de peces anádromos y (4)
ejemplos de cómo los impactos provocados por el humano dañan a los peces anádromos y cómo el enfoque de resiliencia
pudiera producir mejores resultados. Se concluye sugiriendo nuevas líneas de investigación y guías de recuperación para
implementar el enfoque basado en la resiliencia.
Une approche résiliente peut améliorer le rétablissement des populations de poissons
­anadromes
La plupart des populations de poissons anadromes restent à des niveaux faibles ou sont en déclin malgré des investissements substantiels dans le rétablissement de leurs populations. Nous explorons si la résilience (c.-à-d., un paradigme
différent pour comprendre les populations, les communautés et les écosystèmes) est un cadre alternatif viable pour le
rétablissement des populations de poissons anadromes. Beaucoup de traits d’histoire de vie ont permis aux poissons
anadromes de prospérer dans les écosystèmes intacts, mais sont devenus des malédictions contemporaines à cause de
l’augmentation des effets anthropiques. Cette contradiction engendre un défi important en matière de conservation, mais
rend également ces poissons d’excellents candidats pour une approche résiliente. Cette dernière reconnaît la nécessité de
conserver les caractéristiques de l’histoire de vie, de la population et de l’habitat qui augmentent la capacité d’une population à résister et à se remettre de plusieurs perturbations. Pour évaluer si une approche résiliente représente une stratégie
viable pour le rétablissement des populations des poissons anadromes, nous examinons quatre questions: (1) comment
la théorie de la résilience peut nous informer sur le rétablissement des populations de poissons anadromes, (2) comment
une approche fondée sur la résilience est fondamentalement différente des stratégies de rétablissement de populations de
poissons anadromes existantes, (3) les caractéristiques écologiques qui ont historiquement été bénéfiques à la persistance
des poissons anadromes, et (4) des exemples de la façon dont les impacts humains nuisent aux poissons anadromes et
comment une approche résiliente pourrait produire des résultats plus fructueux. Nous terminons en proposant de nouvelles orientations de recherche et de rétablissement des populations pour la mise en œuvre d’une approche fondée sur la
résilience.
NEED FOR A NEW APPROACH
Exploring new approaches to anadromous fish restoration
is essential. Despite substantial investments in research and
management, precipitous declines have occurred in many
populations of these highly valued organisms, which make
spectacular migrations between freshwater and saltwater
habitats. In the North Atlantic, for example, of 35 anadromous
populations investigated, indices of abundances dropped more
than 98% in 13 populations and more than 90% in an additional
11 populations (Limburg and Waldman 2009).
Like many organisms, anadromous fish are threatened
by a variety of natural and anthropogenic disturbances. The
restoration of anadromous fish is especially challenging because
migratory fish have complex life cycles that use diverse habitats.
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In fact, the unique life history characteristics of anadromous
fish historically aided their resilience in intact ecosystems but
often erode resilience in human-impacted ecosystems. For
example, the ability to move across habitats allows anadromous
fish to take advantage of breeding and nursery grounds that
yield successful recruitment while also utilizing high ocean
productivity for growth. Unfortunately, human modification
of natal rivers and coastal areas, especially the construction
of physical barriers and degradation of estuarine habitat, has
made these taxa extraordinarily vulnerable to extirpation. This
apparent contradiction (historical advantages have become
contemporary curses) has put most anadromous fish at risk
in the 21st century. As a result, anadromous fish are excellent
candidates for a resilience approach to restoration.
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Here, we first review select aspects of the resilience
perspective from the literature to provide specific context
regarding anadromous fish. We also compare and contrast
resilience theory to extant approaches to anadromous fish
restoration to suggest how a resilience perspective might benefit
anadromous fish conservation. (Many individual management
and restoration remedies have been applied to anadromous fish,
but to highlight the potential advantages that resilience theory
may confer to anadromous fish conservation and restoration,
we refer to this body of options as “extant” approaches.) Third,
we review several suites of ecological characteristics that
we hypothesize historically promoted resilience for locally
adapted anadromous fish but, at present, may make them
more vulnerable to extirpation. Next, we illustrate how three
anadromous taxa are threatened by multiple anthropogenic
disturbances and how a resilience theory approach might be
more successful for conservation and restoration. Finally, we
identify needs and challenges for anadromous fish restoration
based on resilience theory and make recommendations for future
research and management actions.
WHAT IS A RESILIENCE PERSPECTIVE?
Resilience is a population’s capacity to deal with
environmental change. In his seminal review, Holling (1973:14)
defined ecological resilience as “a measure of the persistence
of systems and of their ability to absorb disturbance and still
maintain the same relationships between populations or state
variables.” Definitions of resilience (e.g., theory, concept,
approach, perspective, framework, thinking, practice) have
evolved and diversified across authors and disciplines.
Some practitioners of resilience theory emphasize particular
components of investigation, whereas others consider
resilience thinking as a broader approach to sustainability (e.g.,
Walker and Salt 2006, 2012). Nevertheless, maintaining or
restoring the capacity of diverse and functional populations,
communities, and ecosystems to resist and recover from
inevitable environmental change or disturbance (e.g., natural
and anthropogenic, anticipated and unanticipated, frequent
and infrequent, mild and severe) is central to all definitions of
resilience.
Resilience represents a philosophy about conservation
and restoration that guides and organizes planning and action
(Folke et al. 2010) rather than any specific set of actions.
Individual restoration plans may adopt different steps to foster
resilience, but clear differences in action will result from extant
conservation- and resilience-based approaches. For example,
both resilience-based and extant management approaches to
anadromous fish restoration seek healthy populations, but
extant approaches might strive to attain a large numerical target
achieved through hatchery stocking of fish with homogeneous
life histories, whereas a resilience approach might prioritize
a numerically smaller population composed of diverse life
histories that can respond to unanticipated changes and make
fuller use of habitats within a watershed.
Resilience can be viewed as an integrated ecology, social
science, and management approach to sustainability. As such,
much of the current resilience literature falls into three major
categories (Figure 1). One aspect seeks to use quantitative
ecological tools to detect, understand, and model ecosystem
trends (e.g., Bestelmeyer et al. 2011; Spanbauer et al. 2014;
Figure 1). For example, of one area of research within this
approach, state or “regime shift” changes are nonlinear
responses that occur through the interruption of ecosystem
processes or feedbacks (e.g., Holling 1973; discussed in
greater detail in the Challenges section). Most ecological
restoration efforts treat these trends as linear, when they often
are more complex. A focus of quantitative ecological research
on ecosystems that embodies nonlinear dynamics, thresholds,
Figure 1. Major components of resilience thinking. Quantitative ecological tools include threshold detection methods (after Bestelmeyer et al.
2011). Social–ecological system tools consider the impact of external drivers (climate, geology, regulations) on coupled ecological and social
systems (after Chapin et al. 2011). Management and conservation with a resilience perspective considers both the human and ecological impacts of management actions (here, removal of the Great Works Dam, 2012, Penobscot River, Maine). Photo credit: K. Wilson.
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uncertainty, and scale is to characterize population trajectories in
response to change (linear, threshold, or hysteresis; Bestelmeyer
et al. 2011). Most restoration plans for anadromous fish do not
explicitly consider state changes and related feedbacks (Cortina
et al. 2006). However, understanding nonlinear dynamics,
tipping points, and feedback loops is critical in restoration
because they can make state changes difficult to reverse (Walker
and Salt 2012) and challenging to manage.
Understanding state changes is critical for anadromous fish
restoration because small populations can result from either low
numbers in the original state or from an irreversible (or difficult
to reverse) state change. Common restoration strategies (e.g.,
stocking, fishways, habitat improvements) that attempt to simply
reverse impairments will not be enough to revitalize anadromous
fish populations if a state change has occurred. Consequently,
the same restoration intervention may succeed or fail depending
on ecosystem state.
A second major category of resilience literature focuses
on the social–ecological system (SES; Folke 2006; Figure
1) because a resilience perspective encompasses ecosystem
stewardship (Chapin et al. 2011) and the interacting systems of
people and nature (Simonsen et al. 2014). This SES literature
seeks to quantitatively model human effects as an integral
part of ecosystem dynamics, not as a problem external to the
ecosystem. Human impacts are the most commonly cited
cause of ecosystem degradation, including anadromous fish
declines. Proponents of resilience theory often argue that
separating consideration of social aspects from the ecological
has prevented resource managers from dealing effectively with
human impacts. Consequently, the noninterdisciplinary nature
of most management or restoration plans has likely contributed
to population declines and ecosystem degradation. Although
most fish biologists do not seek to function as social scientists,
this SES perspective is important to embrace because “many
of the serious, recurring problems in natural resource use and
management stem precisely from the lack of recognition that
ecosystems and the social systems that use and depend on them
are inextricably linked” (Folke et al. 2010). For example, a
purely ecological perspective might advocate removing all dams
from a single watershed, but an integrated SES perspective
would recognize that politically this solution alone is unlikely
to succeed without co-occurring sociopolitical planning and
interdisciplinary implementation.
A third focus of resilience thinking emphasizes the need
to integrate research with management (e.g., Mitchell et al.
2014; Standish et al. 2014; Figure 1). Adaptive management
(learning while doing) was an early part of the resilience
perspective (Holling 1978) because most resilience problems
are too complex to be addressed as controlled laboratory or
reductionistic field experiments. For example, testing whether
habitat heterogeneity can be increased through the establishment
of natural flow regimes, identifying population consequences of
diverse life histories, and quantifying movements in response
to dam removal can only be examined in collaboration with
fisheries managers. As such, integrating management and
research is essential for a resilience approach. Much of the
resilience thinking literature advocates actions as experiments
(e.g., Curtin and Parker 2014). For example, determining how
much disturbance a system can absorb without switching to a
new state and whether interventions will be needed to assist a
recovering ecosystem (Mitchell et al. 2014; Standish et al. 2014)
are outcomes of resilience research that are integrally connected
to management.
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RESILIENCE VS. EXTANT APPROACHES TO
RESTORATION
A resilience approach builds on, but is philosophically
different from, most ongoing anadromous fish restoration
efforts. Although resilience-based and extant fish restoration
approaches share the recognition of a common conservation
problem and embrace the benefits of established fisheries tools
and techniques, the goals, reference states, and targets of the
two approaches are fundamentally different (Table 1). Typically,
the resilience approach will prioritize maintaining diverse life
histories within a watershed to allow a variety of anadromous
fish populations to withstand environmental change. In contrast,
many extant restoration approaches seek to achieve numerical
fish or habitat targets based on historical references such as
data on earlier run sizes or number of kilometers of previously
unimpeded rivers in a watershed. Large numbers of hatchery
salmon, for example, might result in a larger population size
initially (achieving an extant restoration goal), but the resulting
homogeneity in life histories might reduce a population’s
ability to respond to a variety of future changes (failing to
achieve a restoration-theory goal). Given the current realities
of institutional and geopolitical systems that usually seek to
optimize the gain in one objective rather than the best tradeoff among competing objectives (Hermoso et al. 2012), it is
understandable how (and why) the role of disturbance and
uncertainty has been downplayed. The dismal present state of
most anadromous fish populations makes an effective argument
that a resilience-based approach is worth exploring even if it
requires a more complex, politically difficult, socioecological
strategy.
CHARACTERISTICS THAT HISTORICALLY
PROMOTED HEALTHY ANADROMOUS FISH
POPULATIONS
Functional Diversity in Life History and Habitat
Life history diversity (within and across populations) has
historically contributed to resilience of anadromous fish through
varying functional traits, discrete life histories, multiple year
classes of spawners, and pulsed spawning. In the past, for many
anadromous fish populations, rivers were utilized more fully in
time and space by a broader range of life histories. For example,
discrete life history forms in both alosines and Atlantic Salmon
Salmo salar, noted in earlier centuries, showed observable
morphological and behavioral distinctions (Waldman 2013).
Recent work in ecology has focused on trait-based approaches to
assessing the resilience of systems to disturbance (Tilman 2001),
where functional diversity is defined as “the value and range of
functional traits of organisms present in an ecosystem” (Standish
et al. 2014:44). In this case, the aggregated traits of organisms
(or habitats) in the system modulate response to disturbance and
are measured as response diversity (Mori et al. 2013). Although
many variants have been lost, with today’s sophisticated tools
(e.g., otolith analyses; Turner and Limburg 2012), some robust
contemporary populations still demonstrate substantial life
history variation detectable beyond simple visible inspection.
These life history variants may be the raw material of population
recovery, and they need to be preserved.
The “portfolio effect,” or coexistence of multiple life history
strategies within a population, is an important example of how
diversity in life history can increase resilience and stability
(Figge 2004). Within populations, variation increases resilience
by making fuller use of a watershed’s potential life history
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Table 1. Comparison of resilience approach and some present approaches to anadromous fish restoration
including shared and divergent foundational positions as well as needs and challenges (e.g., quantitative,
social-ecological, and integrated research management). This table also provides a roadmap for the
organization of this perspective.
circuits. For example, annual Sockeye Salmon Oncorhynchus
nerka returns over five decades in diverse Bristol Bay, Alaska,
drainages helped buffer any negative environmental conditions
that occurred in individual tributaries; that is, variability in total
Bristol Bay returns was 2.2 times lower than if the system had
consisted of a single homogenous population (Schindler et al.
2010). For White Perch Morone americana, contingents that
include dominant year classes from brackish water nursery areas
and low-level recruitment life histories from freshwater habitats
allow the entire population to persist in diverse conditions
(Kraus and Secor 2005). Thus, in a variable environment, life
history diversity increases the probability that recruitment will
be successful somewhere within the system, leading to greater
numbers or population persistence.
Functional complexity in life history also can be increased
through the “storage effect” and “split cohorts.” The storage
effect that results from multiple-spawner year classes promotes
resilience by accumulating spawning stock biomass annually
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so that when environmental conditions are favorable, the
consequent high egg production can result in rapid population
growth, as has been shown for Striped Bass Morone saxatilis in
Chesapeake Bay (Secor 2007). Pulsed reproductive efforts that
result in temporally split cohorts, such as multimodality in hatch
dates of American Shad Alosa sapidissima (Olney and McBride
2003), are a form of bet-hedging that is more likely to result
in at least one cohort, and possibly two or more cohorts, that
contributes to recruitment. Thus, the storage effect and pulsed
spawning can enhance diversity in reproduction and contribute
to persistence in anadromous fish, increasing the likelihood that
at least some individuals from a spawning season ultimately
contribute to the pool of adult spawners (Secor 2007).
Habitat heterogeneity also promotes resilience of
anadromous fish. Historically, rivers displayed more complex
morphologies, including multiple channels that made floodplains
more accessible (e.g., Walter and Merritts 2008; Snyder 2012).
Habitat mosaics (adjacent habitats that support different
functions) provide environments for life stages from multiple
life histories (Stanford et al. 1996). Before dams, “open” or
effective distances of rivers were greater and included an array
of diverse habitats. Limburg et al. (2003) estimated a decrease
of 4,000 km of mostly upriver habitat (35%) for American Shad
blocked by dams. Healthy, forested riparian corridors provided
temperature control by shading, bank stability with root strength,
and recruitment of large wood, which drives the scouring of
pools and sorting of bed sediment vital to fish habitat quality
(e.g., Bisson et al. 2009; Beechie et al. 2010). Although these
habitat alteration issues affect a variety of fish, a critical
advantage of habitat complexity for anadromous fish is that
multiple life history forms (Schindler et al. 2010) may persist
and coexist by spawning in spatially and temporally specialized
conditions.
Movement Patterns and Connectivity
Free movement adds resilience to anadromous fish
populations. For movement to confer an advantage, suitable
habitats must exist and be connected, but natural and
anthropogenic changes often isolate patches from one another
(Lake 2000). The ability to move within and across localized
habitats and connectivity across movement corridors are
defining features of populations and habitats when anadromous
fish were historically abundant. Such dispersal is an important
way to resist disturbance and promote resilience. For example,
being able to access refuges during times of drought or floods is
important if anadromous fish populations are to survive largescale disturbances (Sedell et al. 1990). In addition, large systems
can be critical sources both for individuals and genetic diversity;
populations in smaller rivers may rely on the ongoing dispersal
of individuals from adjacent larger rivers to maintain their
populations (Palstra et al. 2007).
Many anadromous fish can also be viewed as occurring in
metapopulations, which are characterized by the interaction
between demographic connectedness (in which populations
are strongly dependent on local demographic processes) and
dispersal (a nontrivial element of external replenishment that
can serve as a hedge against local population extinction).
Substantial stability of a metapopulation can be maintained in
fluctuating environments at low and even moderate levels of
connectivity (Secor et al. 2009). Thus, resilience requires some
degree of connectivity, but too much connectivity results in high
synchrony between components, which can reduce stability.
Figure 2. Normalized time series of indices of abundance of three North Atlantic anadromous fish species. Adapted from Limburg and Waldman (2009).
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Within anadromous fish species, diversity in migration
strategies was likely more common when anadromous fish
were abundant. Currently, some species are still plastic in
their migrations and exhibit a suite of movement patterns
(e.g., Pautzke et al. 2010; Frank et al. 2011). For example,
anadromous Striped Bass show diverse migration behaviors
from life residency within fresh and low salinity river reaches,
to a mainly estuarine existence, to long-distance marine
migrations (Zlokovitz et al. 2003). Furthermore, the extent of
marine migration of Striped Bass appears density dependent
(Waldman et al. 1990). Striped Bass also form distinct
contingents of feeding and migratory behaviors (Mather et al.
2013). These complex movements can connect nutrients, energy,
and populations across estuaries, thus enhancing resistance to
disturbance and, consequently, increasing resilience.
Mobile species such as anadromous fish can aggregate in
time and space in relation to their abundances. Populations,
which normally enter rivers to spawn over a period of weeks to
months, can contract their distributions within rivers spatially
and temporally (Bilkovic et al. 2002). For example, Pink Salmon
O. gorbuscha in some Asian and North American rivers do not
travel as far upstream in years with small runs as in years with
larger runs (Heard 1991). Thus, flexibility in movements that
facilitate concentrations of individuals can sustain reproduction
and mitigate against extirpation at low (and even relict)
population levels by increasing the chances of sheer persistence
(compared to disaggregated spawning).
THREE EXAMPLES
A common suite of primarily anthropogenic disturbances
have eroded many of these above-described characteristics
that conferred resilience in historically abundant anadromous
fish populations. The litany of causes that have contributed to
declines of anadromous fishes is well characterized (Limburg
and Waldman 2009). Commonly cited factors include upstream
and downstream blockage by dams, overfishing, habitat
degradation and pollution, and predation by and competition
with nonnative fishes or hatchery-cultured conspecifics
(Waldman 2013). The relative importance of this common
suite of disturbances, of course, varies across taxa, ecosystems,
and time frames. Below, we briefly illustrate disturbances that
adversely affect three at-risk anadromous taxa and then describe
the present state of resilience-related characteristics.
Striped Bass
Atlantic coastal Striped Bass stocks spawn within the
Hudson, Delaware, or Chesapeake estuaries and then as
subadults and adults make seasonal coastal migrations to feed
before returning to their natal estuary to spawn (Richards and
Rago 1999). After surviving a population crash in the 1980s due
to overfishing, habitat degradation, and other factors, Striped
Bass is the only at-risk Atlantic coast anadromous fish that
subsequently has shown a clear recovery (Figure 2A).
This recovery demonstrates a successful holistic approach
to withstanding multiple disturbances. Even during its crash,
coastal Striped Bass retained a diverse portfolio of life histories,
multiple genetic stocks, and multiple spawning cohorts that
resulted from a long-lived, fecund, iteroparous life history. The
broad physiological tolerances, general life history, and more
coastal–estuarine distribution make Striped Bass less vulnerable
to the reductions in freshwater habitat and connectivity that have
devastated other anadromous fish (e.g., dams for alosines and
salmon). Coastal Striped Bass also have retained a wide array
of within- and across-estuary migration strategies, including
partial migration and behavioral contingents that allow them to
adjust their distribution in time and space (Pautzke et al. 2010;
Mather et al. 2013). Although they continue to face multiple
anthropogenic threats, coastal Striped Bass may serve as a
model for resilience-building restoration strategies for other
anadromous fish.
River Herring
Anadromous river herring include two species (Alewife
Alosa pseudoharengus and Blueback Herring A. aestivalis).
These iteroparous clupeids spawn in rivers and lakes between
New Brunswick and Florida. During their life cycle, river
herring exhibit flexibility by utilizing diverse habitats including
freshwater, estuaries and nearshore marine waters (Kosa and
Mather 2001), mainstem river corridors (Frank et al. 2011), and
the ocean (Stone and Jessop 1992).
Historically, the use of multiple habitats, diverse movement
strategies, and the ability to aggregate and spawn multiple times
allowed these fish to take advantage of locally advantageous
conditions. Unfortunately, for most extant river herring
populations, a common suite of anthropogenic stressors (i.e.,
fishing, habitat degradation, fragmentation) have reduced
their abundances (Figure 2B) and simplified their life history
portfolios such that only a few exhibit multiple life histories
(e.g., Turner and Limburg 2012). Human impacts have also
reduced the storage effect derived from repeat spawning for
many populations (ASMFC 2012). Moreover, anthropogenic
stressors such as dams, introduced predators, and targeted
fisheries prevent remaining river herring from taking advantage
of the broader resources and variability of the entire system.
Atlantic Salmon
The U.S. federally endangered Atlantic Salmon is another
classic example of a species with an anadromous life history that
has declined dramatically (Figure 2C), falling from high total
adult populations in U.S. rivers (as many as 500,000 in Colonial
times) to just 611 in 2013 (USASAC 2014).
Historically, Atlantic Salmon populations displayed
functional diversity within and across populations for many
life history traits, including juvenile residence time in
freshwaters, adult time at sea, and age at first reproduction
(e.g., Thorstad et al. 2008). Stocking of hatchery-produced
individuals, commercial and recreational fishing, and other
human impacts have reduced this life history variation. Atlantic
Salmon can spread risk across many spawning locations, and
run sizes correlate positively with habitat heterogeneity (Kim
and Lapointe 2011). However, human-related habitat changes
reduce these advantages of using diverse habitats. For example,
dams and ineffective passage diminish the proportion of the
population that reaches diverse upriver historical spawning
reaches (Brown et al. 2013).
Variation in movement patterns historically existed within
and across populations. Atlantic Salmon enter and ascend rivers
from as much as a year to shortly before spawning season
(Thorstad et al. 2008), thereby dispersing potential spawners
temporally while helping to ensure that individuals will be
present to reproduce at the appropriate time. Migration allows
this species to aggregate in response to good feeding conditions
in the North Atlantic Gyre and previously successful freshwater
spawning locations. This aggregation that is an advantage under
pristine conditions can also make these fish more vulnerable to
site specific disturbances (e.g., fishing).
The three examples above illustrate how characteristics
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123
A resilience-based strategy emphasizes the
diversification of life history portfolios and
enlargement of storage effects via increased
numbers of spawning cohorts.
that conferred resilience on anadromous fish historically make
them especially vulnerable to human impacts. Extant restoration
approaches are often inadequate to recover what has been lost.
However, a resilience-based approach may provide successful
restoration by seeking to rebuild suites of disturbance-resistant
characteristics that were historically present. In the next section,
we build on the generalities described above to identify needs
and challenges, and then propose future research, restoration,
and management directions to promote a resilience-based
approach (Table 1).
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NEEDS AND CHALLENGES: FUTURE DIRECTIONS
FOR ANADROMOUS FISH
Holistic Integrative Approaches
Holistic integration of multiple disturbances, boundaries
(spatial, temporal, and disciplinary), and human activities (as
problems and solutions) is a critical component of a resilience
perspective (Table 1). Many restoration professionals are aware
of the need for a holistic geographic and interdisciplinary
approach (e.g., Bowden 2013), preferably employing adaptive
management to better understand the system and to evaluate
efforts. Some natural resource agency policies explicitly call
for managing for resilience (i.e., the National Oceanic and
Atmospheric Administration’s Resilient Ecosystems; Benson
and Garmestani 2011). Researchers and managers (1) must
identify the factors that give populations the best chance
of recovery in the face of multiple spatial disturbances, (2)
incorporate solutions over multiple geographic areas, (3) view
the solutions through the lens of an integrated social–ecological
system, and (4) implement management actions that are
integrated geographically and across time.
Quantitative Approaches to Detecting Ecosystem Trends
Complex quantitative dynamics of ecosystem trends (e.g.,
state changes, thresholds, feedbacks) are an integral part of
resilience theory (Table 1). Three trajectories are possible in
population decline and recovery (Figure 1). These include
(1) a simple, largely linear relationship between ecosystem
state or biological response and environmental drivers, (2)
a model in which environmental drivers force the crossing
of a threshold where the ecosystem moves to a new state of
biological response or regime shift, and (3) a “threshold with
hysteresis” or “catastrophic fold” trajectory. In this last response,
environmental drivers force the ecosystem or biological
response past a threshold to a new state, but simply removing the
original disturbance does not return the system to the previous
state because new stabilizing feedbacks maintain the system in
the new state. Understanding the state and trajectory of decline
using existing methodologies (e.g., Bestelmeyer et al. 2011) can
aid the evaluation of restoration actions because management
actions will vary in effectiveness depending on the underlying
ecosystem state. Differentiating between these trajectories is
not trivial and can be difficult to do in the absence of adequate
time series, a common problem for many anadromous species.
However, new methods are available for detecting approaching
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Fisheries | Vol. 41 • No. 3 • March 2016
thresholds (e.g., Dakos et al. 2012; Carpenter et al. 2014), and
we anticipate stronger data sets to become available as these
species undergo greater scrutiny.
Maintain Diversity to Restore Resilience
Resilience theory embodies a different way of thinking
about disturbance and uncertainty and the role of variability
as a source of resilience. This variability, including life history
variants, multiple populations, and repeat or pulsed spawning
cohorts, can help restore resilience. Historically, maintaining
diversity in life histories and spawning year classes has not
been a goal in anadromous fish management and restoration,
largely because of the substantial difficulty in on-the-ground
implementation.
Operationally, a resilience-based strategy emphasizes the
diversification of life history portfolios and enlargement of
storage effects via increased numbers of spawning cohorts.
Functional life history diversity may not be a high priority for
extant restoration approaches because all life history variants
may not contribute equally to population dynamics or be equally
desirable as sport fish. However, a resilience approach would
seek to preserve this diversity, even at the cost of lower returns,
in order to ensure a population’s ability to respond to future
disturbances. In the same way, a resilience approach would seek
to maintain a diversity of habitat types, including less productive
habitats that may have primary importance only as refugia or
alternate spawning habitat during disturbances.
Integration of Habitat Complexity
Ecologically, a resilience-based restoration plan evaluates
what combination of life histories, genetic diversity, habitat type,
amount, and connectivity will give the target population the
best chance to resist and recover from a suite of anthropogenic
and natural disturbances across a range of spatial and temporal
timescales. Habitat restoration efforts need to be considered
within the context of the entire watershed and the dynamic
nature of river systems, not just within a specific political
boundary, static equilibrium condition, or isolated restoration
opportunity such as dam removals or habitat modifications.
Habitat complexity was once strongly connected with life
history diversity of anadromous species, and both are still
needed for resilience. Allowing the elaboration of a suite of
within-species variations in life history strategies through
restoration of an appropriate mosaic of connected habitats for
an entire watershed will form the basis of a resilience-based
approach.
Socioecological Integration and Implementation
A resilience approach does not demand that environmental
professionals look at everything everywhere all of the time,
but a resilience approach does recommend that socioecological
integration be a priority when planning and setting goals.
Integrating humans into the management process (as problems
and solutions within an SES framework) is essential in moving
forward (Table 1). In SES integration, specialization (within
disciplines, agencies, ecosystems) can limit the ability of
researchers and managers to see and pursue a larger integrative
approach. Administrators and policy makers will play a key role
in these challenges in that they need to seek mechanisms by
which synthesis across disciplines and other divisions will be
supported and even rewarded.
A resilience approach also encourages stakeholder
participation, in contrast with extant approaches that considers
stakeholders as external drivers of environmental problems
for whom managers and other experts make management
recommendations. Thus, conservation legislation needs to help
practitioners implement restoration plans across a variety of
stakeholders, disciplines, habitats, watersheds, and institutional
boundaries. Standardized conservation goals, environmental
regulations, land-water policy, and tax incentives across
municipal and state boundaries would assist with watershed
scale planning and enforcement.
Better monitoring of the population and stressors will allow
environmental professionals to assess whether the system is
able to respond to disturbance. An important question upon
implementation of a resilience approach is how to measure
success. One obvious but coarse measure is sheer population
persistence. But more sensitive metrics are needed, such as the
elaboration of alternative life histories and their expansion in
numbers.
Downloaded by [69.113.49.23] at 13:41 24 February 2016
SUMMARY
Anadromous fish populations are being strongly impacted
by humans. A reason fisheries managers cannot easily solve
the human impact issue is that humans need to use land and
water for social benefit. The anadromous fish restoration
problem can only be solved by balancing human use with fish
conservation. As such, a resilience perspective can provide a
fundamentally different approach. This fresh perspective may
be able to accelerate on-the-ground restoration success for
anadromous fish. The “grand challenge” for future anadromous
fish restoration is to radically rethink which interdisciplinary,
geographically integrated, and multistressor approaches to
anadromous fish restoration might prepare populations to
withstand and recover from disturbances and perhaps even
flourish in a holistic, integrated way. We propose that one
underlying principle may be that increased habitat diversity
in conjunction with increased life history diversity will yield
increased resilience and more robust abundances. Our hope
is that our synthesis, which has only scratched the surface of
the problem and solution, stimulates the advancement and
refinement of a future conceptualization and implementation of a
resilience-based approach.
ACKNOWLEDGMENTS
We are grateful to the other participants in the workshop
entitled “Resilience of North Atlantic Diadromous Fish
Assemblages: A Restoration Perspective” organized by the
Diadromous Species Restoration Research Network (DSRRN),
a National Science Foundation Research Coordination Network
(NSF# 0742196), whose mission is to advance the science
of diadromous fish restoration and promote state-of-the-art
scientific approaches to multiple-species restoration. We
dedicate this article to the late Barbara Arter, whose dedication
and assistance with DSRRN helped make this collaboration
possible. For review of an early version of the article, we
thank Ted Castro-Santos, Karin Limburg, and Eric Palkovacs.
The Kansas Cooperative Fish and Wildlife Research Unit
(Kansas State University, the U.S. Geological Survey, the
Kansas Department of Wildlife, Parks, and Tourism, and the
Wildlife Management Institute) provided support during article
preparation. Use of brand names does not confer endorsement
by the U.S. Government.
REFERENCES
ASMFC (Atlantic States Marine Fisheries Commission). 2012. River
herring benchmark stock assessment. Atlantic States Marine
Fisheries Commission, Stock Assessment Report No. 12-02, volumes 1 and 2, Arlington, Virginia.
Beechie, T. J., D. A. Sear, J. D. Olden, G. R. Pess, J. M. Buffington, H.
Moir, P. Roni, and M. M. Pollock. 2010. Process-based principles
for restoring river ecosystems. BioScience 60:209–222.
Benson, M. H., and A. S. Garmestani. 2011. Can we manage for resilience? The integration of resilience thinking into natural resource management in the United States. Environmental Management 48:392–399.
Bestelmeyer, B. T., A. M. Ellison, W. R. Fraser, K. B. Gorman, S. J. Holbrook, C. M. Laney, M. D. Ohman, D. P. C. Peters, F. C. Pillsbury, A.
Rassweiler, R. J. Schmitt, and S. Sharma. 2011. Analysis of abrupt
transitions in ecological systems. Ecosphere 2(12):1–26.
Bilkovic, D. M., J. E. Olney, and C. H. Hershner. 2002. Spawning of
American Shad (Alosa sapidissima) and Striped Bass (Morone
saxatilis) in the Mattaponi and Pamunkey Rivers, Virginia. Fishery Bulletin 100:632–640.
Bisson, P., J. Dunham, and G. Reeves. 2009. Freshwater ecosystems
and resilience of Pacific salmon: habitat management based on
natural variability. Ecology and Society [online serial] 14(1):45.
Bowden, A. A. 2013. Towards a comprehensive strategy to recover
river herring on the Atlantic seaboard: lessons from Pacific salmon. ICES Journal of Marine Science [online serial]. DOI: 10.1093/
icesjms/fst130.
Brown, J. J., K. E. Limburg, J. R. Waldman, K. Stephenson, E. P. Glenn,
F. Juanes, and A. Jordaan. 2013. Fish and hydropower on the U.S.
Atlantic Coast: failed fisheries policies from half-way technologies. Conservation Letters 6:280–286.
Carpenter, S. R., W. A. Brock, J. J. Cole, and M. L. Pace. 2014. A new
approach for rapid detection of nearby thresholds in ecosystem
time series. Oikos 123:290–297.
Chapin, F. S., III., M. E. Power, S. T. A. Pickett, A. Freitag, J. A. Reynolds, R. B. Jackson, D. M. Lodge, C. Duke, S. L. Collins, A. G. Power, and A. Bartuska. 2011. Earth Stewardship: science for action
to sustain the human–earth system. Ecosphere [online serial]
2(8):art89. DOI: 10.1890/ES11-00166.1.
Cortina, J., F. Tomás Maestre, R. Vallejo, M. Jaime Baeza, A. Valdecantos, and M. Pérez-Devesa. 2006. Ecosystem structure, function, and restoration success: are they related? Journal for Nature Conservation 14:152–160.
Curtin, C. G., and J. P. Parker. 2014. Foundations of resilience thinking. Conservation Biology 28:912–923.
Dakos, V., S. R. Carpenter, W. A. Brock, A. M. Ellison, V. Guttal, A. R.
Ives, S. Kéfi, V. Livina, D. A. Seekell, E. H. van Nes, and M. Scheffer.
2012. Methods for detecting early warnings of critical transitions
in time series illustrated using simulated ecological data. PLoS
ONE 7(7):e41010.
Figge, F. 2004. Bio-folio: applying portfolio theory to biodiversity.
Biodiversity and Conservation 13:827–849.
Folke, C. 2006. Resilience: the emergence of a perspective for social–ecological systems analyses. Global Environmental Change
16:253–267.
Folke, C., S. R. Carpenter, B. Walker, M. Scheffer, T. Chapin, and J.
Rockström. 2010. Resilience thinking: integrating resilience,
adaptability and transformability. Ecology and Society [online
serial] 15(4):20.
Frank, H. F., M. E. Mather, J. M. Smith, R. M. Muth, and J. T. Finn. 2011.
Role of origin and release location in pre-spawning movements
of anadromous Alewives. Fisheries Management and Ecology
18:12–24.
Heard, W. R. 1991. Life history of Pink Salmon (Oncorhynchus gorbuscha). Pages 121–230 in C. Groot and L. Margolis, editors. Pacific salmon life histories. UBC Press, Vancouver.
Hermoso, V., F. Pantus, J. O. N. Olley, S. Linke, J. Mugodo, and P. Lea.
2012. Systematic planning for river rehabilitation: integrating
multiple ecological and economic objectives in complex decisions. Freshwater Biology 57:1–9.
Holling, C. S. 1973. Resilience and stability of ecological systems. Annual Review of Ecology and Systematics 4:1–23.
———, editor. 1978. Adaptive environmental assessment and management. Wiley, London.
Kim, M., and M. Lapointe. 2011. Regional variability in Atlantic Salmon
(Salmo salar) riverscapes: a simple landscape ecology model explaining the large variability in size of salmon runs across Gaspé
watersheds, Canada. Journal of Freshwater Fish 20:144–156.
Kosa, J. T., and M. E. Mather. 2001. Processes contributing to variability in regional patterns of juvenile river herring abundance
Fisheries | www.fisheries.org
125
Downloaded by [69.113.49.23] at 13:41 24 February 2016
across small coastal systems. Transactions of the American Fisheries Society 130(4):600–619.
Kraus, R. T., and D. H. Secor. 2005. Application of the nursery-role
hypothesis to an estuarine fish. Marine Ecology Progress Series
291:301–305.
Lake, P. S. 2000. Disturbance, patchiness, and diversity in streams.
Journal of the North American Benthological Society 19:573–
592.
Limburg, K. E., K. A. Hattala, and A. Kahnle. 2003. American Shad
in its native range. Pages 125–140 in K. E. Limburg and J. R.
Waldman, editors. Biodiversity, status, and conservation of
the world’s shads. American Fisheries Society, Symposium 35,
Bethesda, Maryland.
Limburg, K. E., and J. R. Waldman. 2009. Dramatic declines in North
Atlantic diadromous fishes. BioScience 59:955–965.
Mather, M. E., J. T. Finn, C. G. Kennedy, L. A. Deegan, and J. M. Smith.
2013. What happens in an estuary does not stay there: patterns
of biotic connectivity resulting from long-term ecological research. Oceanography 26:168–179.
Mitchell, M., R. Griffith, P. Ryan, G. Walkerden, B. Walker, V. A. Brown,
and S. Robinson. 2014. Applying resilience thinking to natural resource management through a “planning-by-doing” framework.
Society and Natural Resources 27:299–314.
Mori, A. S., T. Furukawa, and T. Sasaki. 2013. Response diversity determines the resilience of ecosystems to environmental change:
response diversity and ecosystem resilience. Biological Reviews
88:349–364.
Olney, J. E., and R. S. McBride. 2003. Intraspecific variation in batch
fecundity of American Shad: revisiting the paradigm of reciprocal latitudinal trends in reproductive traits. Pages 185–192 in K.
E. Limburg and J. R. Waldman, editors. Biodiversity, status, and
conservation of the world’s shads. American Fisheries Society,
Symposium 35, Bethesda, Maryland.
Palstra, F. P., M. F. O’Connell, and D. E. Ruzzante. 2007. Population
structure and gene flow reversals in Atlantic Salmon (Salmo salar) over contemporary and long-term temporal scales: effects
of population size and life history. Molecular Ecology 16:4504–
4522.
Pautzke, S. M., M. E. Mather, J. T. Finn, L. A. Deegan, and R. M. Muth.
2010. Seasonal use of a New England estuary by foraging contingents of migratory Striped Bass. Transactions of the American Fisheries Society 139(1):257–269.
Richards, R. A., and P. J. Rago. 1999. A case history of effective fishery management: Chesapeake Bay Striped Bass. North American Journal of Fisheries Management 19(2):356–375.
Schindler, D. E., R. Hilborn, B. Chasco, C. P. Boatright, T. P. Quinn,
L. A. Rogers, and M. S. Webster. 2010. Population diversity and
the portfolio effect in an exploited species. Nature 465:609–613.
Secor, D. H. 2007. The year-class phenomenon and the storage effect in marine fishes. Journal of Sea Research 57:91–103.
Secor, D. H., L. A. Kerr, and S. X. Cadrin. 2009. Connectivity effects
on productivity, stability, and persistence in a herring population
model. ICES Journal of Marine Science 66:1726–1732.
Sedell, J. R., G. H. Reeves, F. R. Hauer, J. A. Stanford, and C. P. Hawkins. 1990. Role of refugia in recovery from disturbances: modern fragmented and disconnected river systems. Environmental
Management 14:711–724.
126
Fisheries | Vol. 41 • No. 3 • March 2016
Simonsen, S. H., R. Biggs, M. Schlüter, M. Schoon, E. Bohensky, G.
Cundill, V. Dakos, T. Daw, K. Kotschy, A. Leitch, A. Quinlan, G. Peterson, and F. Moberg. 2014. Applying resilience thinking: seven
principles for building resilience in social–ecological systems.
Stockholm Resilience Center, Stockholm, Sweden.
Snyder, N. P. 2012. Restoring geomorphic resilience in streams. Pages 160–164 in M. Church, P. M. Biron, and A. Roy, editors. Gravelbed rivers: processes, tools, environments. John Wiley & Sons,
Ltd., Chichester, West Sussex, UK.
Spanbauer, T. L., C. R. Allen, D. G. Angeler, T. Eason, S. C. Fritz, A. S.
Garmestani, K. L. Nash, and J. R. Stone. 2014. Prolonged instability prior to a regime shift. PLoS ONE 9(10):e108936.
Standish, R. J., R. J. Hobbs, M. M. Mayfield, B. T. Bestelmeyer, K. N.
Suding, L. L. Battaglia, V. Eviner, C. V. Hawkes, V. M. Temperton,
V. A. Cramer, J. A. Harris, J. L. Funk, and P. A. Thomas. 2014. Resilience in ecology: abstraction, distraction, or where the action
is? Biological Conservation 177:43–51.
Stanford, J. A., J. V. Ward, W. J. Liss, C. A. Frissell, and R. N. Williams.
1996. A general protocol for restoration of regulated rivers. Regulated Rivers: Research and Management 12:391–413.
Stone, H. H., and B. M. Jessop. 1992. Seasonal distribution of river
herring Alosa pseudoharengus and A. aestivalis off the Atlantic
coast of Nova Scotia. Fishery Bulletin 90:376–389.
Thorstad, E. B., F. Økland, K. Aarestrup, and T. G. Heggberget. 2008.
Factors affecting the within-river spawning migration of Atlantic
Salmon, with emphasis on human impacts. Reviews in Fish Biology and Fishery 18:345–371.
Tilman, D. 2001. Functional diversity. Encyclopedia of Biodiversity
3:109–121.
Turner, S. M., and K. E. Limburg. 2012. Comparison of juvenile Alewife
growth and movement in a large and small watershed. Marine
and Coastal Fisheries: Dynamics, Management, and Ecosystem
Science 4:337–345.
USASAC (U.S. Atlantic Salmon Assessment Committee). 2014. Annual report of the U.S. Atlantic Salmon Assessment Committee
to North Atlantic Salmon Conservation Organization. U.S. Atlantic Salmon Assessment Committee, Report No. 26-2013, Old
Lyme, Connecticut.
Waldman, J. 2013. Running silver: restoring Atlantic rivers and their
great fish migrations. Lyons Press, Guilford, Connecticut.
Waldman, J. R., D. J. Dunning, Q. E. Ross, and M. T. Mattson. 1990.
Range dynamics of Hudson River Striped Bass along the Atlantic coast. Transactions of the American Fisheries Society
119(5):910–919.
Walker, B., and D. Salt. 2006. Resilience thinking: sustaining ecosystems and people in a changing world. Island Press, Washington,
D.C.
———. 2012. Resilience practice: building capacity to absorb disturbance and maintain function. Island Press, Washington, D.C.
Walter, R. C., and D. J. Merritts. 2008. Natural streams and the legacy
of water-powered mills. Science 5861:299–304.
Zlokovitz, E. R., D. H. Secor, and P. M. Piccoli. 2003. Patterns of migration in Hudson River Striped Bass as determined by otolith
microchemistry. Fisheries Research 63:245–259.