Opinion
TRENDS in Ecology and Evolution
Vol.20 No.2 February 2005
Critical science gaps impede use of
no-take fishery reserves
Peter F. Sale1, Robert K. Cowen2, Bret S. Danilowicz3, Geoffrey P. Jones4,
Jacob P. Kritzer5, Kenyon C. Lindeman6, Serge Planes7, Nicholas V.C. Polunin8,
Garry R. Russ4, Yvonne J. Sadovy9 and Robert S. Steneck10
1Biological Sciences, University of Windsor, Windsor, ON, Canada, N9B 3P4
2Rosensteil School of Marine & Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami,
FL 33149-1098, USA
3College of Science & Technology, Georgia Southern University, Statesboro, GA 30460, USA
4Marine Biology and Aquaculture, James Cook University, Townsville, QLD 4811, Australia
5Environmental Defense ­ Oceans Program, 257 Park Ave. S., New York, NY 10010, USA
6Environmental Defense ­ Oceans Program, 14630 Southwest 144 Terr., Miami, FL 33186-5617, USA
7Centre de Biologie et d'EŽcologie Tropicale et MeŽditerraneŽe, EPHE ESA 8046 CNRS, UniversiteŽ de Perpignan, Perpignan 66860,
France
8Marine Sciences & Coastal Management, University of Newcastle, Newcastle upon Tyne, UK, NE1 7RU
9Ecology & Biodiversity, The University of Hong Kong, Pok Fu Lam Rd, Hong Kong, China
10School of Marine Sciences & Darling Marine Center, University of Maine, Walpole, ME 04573, USA
As well as serving valuable biodiversity conservation
few well documented cases where they supplement fished
roles, functioning no-take fishery reserves protect a
stocks in surrounding areas [6,7]. However, it is prema-
portion of the fishery stock as insurance against future
ture to assume that no-take reserves are invariably
overfishing. So long as there is adequate compliance by
effective in fisheries management, because there are
the fishing community, it is likely that they will also
relatively few empirical studies, many of which are poorly
sustain and even enhance fishery yields in the surround-
ing area. However, there are significant gaps in scientific
Glossary
knowledge that must be filled if no-take reserves are to
be used effectively as fishery management tools.
Adaptive management: a resource management program in which manage-
Unfortunately, these gaps are being glossed over by
ment actions are deliberately used as experimental manipulations of the
managed system to test predictions of alternative models.
some uncritical advocacy. Here, we review the science,
BACIP: `before-after control-impact pairs'; a sampling design that enables the
identify the most crucial gaps, and suggest ways to fill
unambiguous testing of effects on an ecological system owing to a particular
impact, such as creation of a no-take reserve.
them, so that a promising management tool can help
Connectivity:
the demographic linking of local populations through the
meet the growing challenges faced by coastal marine
dispersal among them of individuals as larvae, juveniles, or adults. Successful
fisheries.
dispersal requires that individuals move between populations, and become
successfully incorporated into the recipient population.
Dispersal envelope: the probability distribution of dispersal distances around a
source location, such as a no-take reserve.
Groundfish: a broad array of demersal fishery species that are captured by
Introduction
towed gear, such as trawls, that travel across the substratum.
No-take fishery reserve:
a marine protected area within which extractive
Worldwide, coastal marine fisheries are under ever-
fishing activities are regulated (usually not permitted).
increasing threat of collapse. Effort increases, yields
Recruitment:
the addition of a cohort of young animals to a population.
remain stable or decline, and other anthropogenic impacts
Recruitment of marine species is measured at various stages in the lifetime: at
the age or size at which individuals become susceptible to the fishery, or at a
degrade habitats and ecological systems on which the
specific time of life such as when moving from the pelagic larval to the
fishery species depend [1­3].
demersal phase.
Recruitment subsidy: the enhancement of production of a fishery species,
Marine protected areas (MPAs) of various types are a
within the fished locations surrounding one or more no-take reserves, owing to
form of resource management that regulates human
the net export from the reserve of pelagic larvae.
activities in particular locations. Although there are
Spillover: the enhancement of production of a fishery species, within the fished
locations surrounding one or more no-take reserves, owing to the net
many types of MPA, we are concerned here with no-take
movement of juveniles and adults out of the reserve.
fishery reserves (see Glossary), also termed `closed areas'
Stock-recruit relationship: the relationship between the size of a population
or `harvest refugia' [4], and we focus on fishery benefits
(stock) and the rate of recruitment to it. In most marine organisms, these
relationships show such high variance in space and time that it has proved
while recognizing that no-take reserves also have import-
difficult to determine the nature of the underlying dynamics.
ant biodiversity conservation benefits. Such reserves
Trophic cascade: a change in the relative abundances of species comprising an
commonly increase the density, biomass and average size
ecological community caused by changes in abundance at one trophic level
leading to changes at other levels because of the feeding interactions that take
of target species within their borders [5], and there are a
place. In the context of no-take reserves, cessation of fishing large piscivores
might lead to declines in the abundance of their prey species, and the release of
Corresponding author: Sale, P.F. (sale@uwindsor.ca).
still lower trophic groups that then become more abundant.
Available online 25 November 2004
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0169-5347/$ - see front matter Q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2004.11.007
Opinion
TRENDS in Ecology and Evolution
Vol.20 No.2 February 2005
75
designed, and even the reported increases in density
individuals within their borders to grow larger and live
within reserve borders can be slight. Empirical studies of
longer, no-take reserves greatly enhance the fecundity of
no-take reserves published before 2002 were outnumbered
sedentary species; this increased fecundity tends to
by theoretical papers and reviews (44% versus 56% of 205
enhance fishery yields in surrounding populations
total), many of which were characterized as advocacy [8].
through two processes: spillover and recruitment subsidy
Halpern reviewed 89 empirical studies, and found that
[14]. Spillover and recruitment subsidies are likely to act
63% reported increases in density whereas 7% reported
at different spatial scales, and the design of reserves will
declines [5]. Using more rigorous standards for sampling
ideally use information about the rates and patterns of
design and magnitude of reported density difference,
exchange for all life-history stages of the target organisms.
Willis et al. report just five empirical studies that
To be fully effective, no-take reserves should display
demonstrate this simple effect unambiguously [8]. Well
sustained net export of target biomass that at least
documented effects outside reserve borders are even
compensates for the loss of the fishing area used to set
rarer [7].
up the reserves [14]. Theoretical studies have focused on
Similar to others [2,6­13], we anticipate that no-take
the mechanisms of spillover [24] and recruitment subsidy
reserves can become an effective fishery management tool.
[25­30]; however, empirical tests of the theory are rare [8].
However, we are concerned (as are some others [8,14]) that
Effective no-take reserves, or networks of these, must be
repeated, uncritical advocacy has the potential to:
both net exporters of propagules to sustain surrounding
(i) diminish recognition of the remaining gaps in our
fisheries, and largely self-sustaining systems [14,29].
knowledge and, therefore, diminish support for continued
Ideally, the level of sustained net export must be just
research and development of an important management
right, because there must be sufficient self-recruitment
tool; (ii) raise expectations in the fishing community and
(within a single reserve or a network of reserves) to ensure
in conservation circles that might prove unachievable [15];
sustainability when surrounding unprotected populations
(iii) lead to neglect of other effective techniques for
are fished down. The design of a network should entail a
managing fishing effort [14]; and (iv) result in expenditure
delicate balancing act involving correct choice of size,
of scarce financial and other resources in the creation and
number and placement of reserves. One might even expect
management of no-take reserves that are inappropriately
that protection of a specific proportion of habitat is
sized or sited. The overall result will be a continued
required for effectiveness (Box 1). One of the main
decline in coastal fisheries, and the erosion of the
scientific factors driving these design choices should be
credibility of marine science and scientists with respect
the extent of connectivity among local populations of the
to questions of resource management and conservation
target species, a feature of marine populations about
[16]. Here, we summarize the theory underlying the use of
which we know relatively little.
no-take reserves, identify gaps in knowledge and suggest
ways in which to fill them.
Size, placement, and spacing rules for no-take reserves
For biodiversity conservation, there are sound biological
Theory for design of no-take reserves
reasons to expect that larger reserves will be more
Reserves can insure against over-exploitation, and
effective. Larger reserves hold larger populations of
enhance surrounding fisheries
more species. These larger populations should be better
No-take reserves potentially achieve two things for fish-
protected from extinction, both because they are larger,
eries management: they provide insurance against unsus-
and because individuals should be able to complete their
tainable declines of species owing to overfishing, and they
life cycles within the reserve boundaries, making the
supplement the production of fishery species in the
populations largely self-sustaining [29,31,32].
surrounding fished area, thereby sustaining or enhancing
However, no-take reserves also have a fisheries man-
yields. These functions derive primarily from the recruit-
agement role. As well as being large enough to contain and
ment variation and connectivity that are characteristic of
protect a population of adequate size, they need to be small
marine populations.
enough to be able to supplement production effectively in
Recruitment to fishery populations is typically highly
surrounding fished populations [22,33]. Spillover alone,
variable in both space and time [17,18]. Consequently, a
which is a function of perimeter length rather than area of
strong recruitment event can persist for many years, and
the reserve, is likely to have only modest and local
be particularly important in long-term replenishment.
enhancing effects on fished populations, but recruitment
However, variable recruitment also means that small
subsidy, with the potential to supplement production of
(e.g. overfished) populations will be especially susceptible
fished populations over much greater areas, is negatively
to dramatic crashes, or even local extinction [19,20].
dependent on reserve area [33­35]. We recognize that,
Therefore, no-take reserves, which tend to maintain
because reserve sizes also will be dependent on the
population densities at higher levels, can provide an
mobility and demography of the target fishery species
effective buffer against overexploitation [21].
they are intended to assist, reserves cannot be simul-
Marine populations are interconnected, exchanging
taneously of optimum size for all contained species, and
individuals mainly through larval dispersal and thereby
widely ranging rare species might never be adequately
influencing the dynamics of each population. This connec-
conserved using reserves (Box 2).
tivity is key to the role of no-take reserves because it
Even the smallest no-take reserves (w1­5 km2) usually
provides the mechanism for reserves to enhance fish
provide conservation benefits in terms of enhanced bio-
production outside their borders [14,22,23]. By allowing
mass of sedentary target species within the boundaries [5].
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Opinion
TRENDS in Ecology and Evolution
Vol.20 No.2 February 2005
Box 1. Amount of area to be protected
Box 2. Mobility of the target species
The proportion of a coastal area to be protected is usually
Most no-take reserves are small (1­20 km2, median w16 km2) [13,57],
determined through a compromise between the desire by some to
and many coastal demersal fishes are relatively sedentary (living
protect all biodiversity and ecosystem function from human impact,
spaces of !1 km2 suit many coral reef species [37]). However, many
and the socioeconomically valid goal of providing for continued use
coastal fishery species, such as cod, snappers, or groupers, tend to
of the fishery and other resources in the area. Because no-take
be larger in size and often also more mobile. Such species also are
reserves have explicit fishery management goals, the question must
usually long lived and slow to mature; these characteristics correlate
be, what is the minimum proportion of area to place within reserves
with higher probability of depletion or extirpation owing to over-
to sustain or enhance the fishery?
fishing [13,58]. How well do reserves serve to sustain fisheries for
Unfortunately, the question of how much area is needed is not
these larger, economically more important species?
clarified by examining existing no-take reserves. These are pre-
Some fishery species are known to travel many kilometers
dominantly small, comprising only a tiny proportion of the
annually to specific spawning areas (e.g. certain snappers Lutjanus
surrounding area, and increases in density and biomass, a sign
spp. and groupers Epinephelus spp. [13,14]), seasonally in response
that the reserve provides protection, appear not to be related to
to temperature changes (e.g. sole Solea solea [59]), or while
reserve size over the range of sizes available [5]. No-take reserves
undergoing ontogenetic habitat shifts (e.g. American lobster
currently comprise 5% of Florida Keys National Marine Sanctuary
Homarus americanus [60]). Considerable interspecific variation is
and, until recently, !5% of the Great Barrier Reef Marine Park
evident among rocky- and coral reef fishery species in the timing and
(GBRMP), the two largest managed areas in the world. A broader
extent of spawning migrations, for example, and even within
range of examples will be available soon: the GBRMP was rezoned to
families trends might not be evident [61]. Among groupers, the
increase no-take reserves to 33.4% of its total area on July 1, 2004
coral trout Plectropomus leopardus is a `resident' spawner, moving
[54], and the recently designated Northwestern Hawaiian Islands
!2 km to spawning sites, and is well suited to current scales of
Coral Reef Ecosystem Reserve will have 20% of area within no-take
typical no-take reserves [62], yet the Nassau grouper Epinephelus
reserves [55].
striatus and the Gag grouper Mycteroperca microlepis migrate
Protecting 20% of the area has become a commonly cited target.
yearly 10 to O100 km from home reefs to reproduce at specific
This arbitrary target relies on the assumption that protecting 20% of
spawning sites [63]. Aggregations occur at highly predictable times
the area protects 20% of the original spawning stock, and on the
and sites, and are particularly vulnerable to fishing [64]. Yet although
argument that protecting 20% of the stock would prevent recruit-
protection of aggregations can effectively enhance spawning
ment overfishing [9,11]. More recent models suggest that O35% of
success [38], few no-take reserves have explicitly incorporated
the total area needs to be in no-take reserves to prevent recruitment
spawning sites [61].
overfishing of sedentary species, such as sea urchins or many reef
Mobility of continental shelf groundfish species is not well known.
fishes, and area requirements differ among species with differing
It is estimated, however, that the effectiveness of reserves for
biology [22,29,33]. If a demographic bottleneck in the form of limited
managing cod Gadus morhua or haddock Melanogrammus aegle-
essential habitat exists for a managed species (such as occurs for
finus on Georges Bank would depend crucially on reserve location
immediately post-settlement American lobster Homarus ameri-
that is relative to seasonal movement patterns of the fish [65]. North
canus) the total sea area protected becomes largely irrelevant for
Sea cod would require no-take areas O60 000 km2 for effective
management [56]. Even details of hydrodynamics could affect how
management [45]. The scale of reserves currently in place appears
much of the area should be protected and in how many pieces [48].
insufficient to accommodate the mobility of many such valuable
For now, efforts to prescribe the correct percentage of sea area to
groundfish species.
protect to sustain a fishery have limited scientific support. Attempts
In general, the larger economically valuable fish species do not
to specify a universal proportion for protection seem naišve.
necessarily mimic behavior of smaller species, and interspecific
differences mean that no-take reserves must be designed for specific
target species. There are many fishery species about which we need
Small reserves might also provide some spillover [5,7,34­37],
more basic ecological information before implementing no-take
and can have an important fishery management role if
fishery reserves to help manage them.
situated at crucial locations, such as spawning aggrega-
tion sites [38] (Box 2). Theory suggests that fishery value
process; however, significant gaps in our knowledge of
is enhanced in a network of small no-take reserves rather
the ecology of coastal marine systems make this a bigger
than in few, widely spaced large reserves, because the many
challenge than some seem to suggest [42]. We identify five
small reserves supplement production over a greater
crucial gaps in the ecological science of no-take reserves.
proportion of the surrounding fished area [22,33,39,40].
(i) When designing no-take reserve networks, the
In addition, whereas establishing a few large reserves
distance and direction in which marine larvae disperse
might have practical advantages in terms of designation
is a primary ecological issue because it directly
and compliance, large marine reserves can be impractical
determines three key things. These are whether: (i)
because they disadvantage some local communities whose
the size of a planned reserve will ensure rates of self-
fishing grounds become closed to fishing, and benefit
recruitment that are adequate for persistence of its
others whose fishing grounds remain open (Box 3).
target populations; (ii) the placement and spacing of a
network of reserves will promote persistence of their
The crucial gaps in scientific knowledge
target populations through dispersal among them;
The planning of MPA locations, sizes and spacing is
and (iii) the sizes, spacing and placement of reserves
currently decided, to a large degree, by the natural
will maximize potential fishery benefits on neigh-
geography of habitats, compromises among different
boring fishing grounds through recruitment subsidy
user groups, issues of compliance and governance, and
[6,10,23,29,33,43]. Knowledge of average effective dis-
much `educated' guesswork concerning ecological aspects
persal envelopes is limited, principally because pat-
of the task [4,13,41]. Few attempts have been made to
terns of larval dispersal are taxon-, site-, and probably
develop, and even fewer to test, ecological theory to help
also time-specific, and are driven by a complex of
guide this process [29]. Clearly, there is scope to develop
sensory capabilities, behavioral responses, and physi-
ecological criteria [32] to inform the decision-making
cal hydrodynamic processes [18]. Gaining information
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Opinion
TRENDS in Ecology and Evolution
Vol.20 No.2 February 2005
77
implement reserves of sufficient size to provide them
Box 3. Socio-economic factors and the design of no-take
with the level of protection required [13,45].
reserves
(iii) Knowledge of the ecosystem impacts of fishing is
Marine reserves are proposed, designed, legally codified,
also limited, but this becomes an important need when
implemented and managed through socioeconomically complex
implementing no-take reserves [3,46]. The lack of
and largely political processes. Too many of them fail to become
fishing inside the reserve might lead, through processes
effective management instruments. Ideally, no-take reserves should
be designed using the best available science. Their effects should be
such as trophic cascades, to changes in community
evaluated, and the results integrated into improved management
structure that cannot currently be predicted explicitly
practice [14]. This iterative process of adaptive management can
[5,13]. The rule that populations of fishery species will
only happen within a close collaboration of scientists, managers, the
be more abundant, larger, older and, therefore more
fishing community and other stakeholders, such as occurred in the
study of line-fishing effects on the Great Barrier Reef [66]. Building
fecund inside a reserve might not hold if such shifts in
political will, developing effective collaborations and securing
community structure occur. If establishment of a
adequate funding for stakeholder incentives and policing are as
reserve does not result in protected populations
vital for success of a science-based reserve program as are the
becoming more abundant and more fecund, there is
identification of hypotheses and the planning of specific manipula-
tions [16,51].
no possibility of recruitment subsidy and spillover.
Without attention to the underlying socioeconomic issues,
Some reported failures to see increased density within
science-based reserve development will be significantly con-
reserves [5,8] might be due to such ecosystem impacts.
strained, and is unlikely to serve scientific or other needs effectively
(iv) We lack adequate knowledge of the behavior of
[50]. Needed are a well-informed set of stakeholders, real capacity to
water masses in the vicinity of complex coastlines and,
enforce regulations and a design, management and monitoring
program that suits the current state of the fishery, provides
although our ability to model hydrodynamics is rapidly
alternative livelihood options and deals with the need to maintain
improving, there continue to be empirical reports that
quality of life of the citizens [49]. Enforcement should be consistent,
reveal ever greater complexity, particularly in the
and the extent and pattern of noncompliance documented [40].
temporal variability of hydrodynamic patterns [47].
Otherwise, the honest resource users will be disenfranchised,
community support for the reserve will whither and, concurrently,
This limits our ability to site reserves effectively,
the controls needed for scientific evaluation of results will be
because the pattern of water movement in a region
compromised or lost. In rare places where communities traditionally
might modify the effectiveness of any particular pattern
have depended on local marine resources, customary marine tenure
of reserve size and spacing [48]. It is also theoretically
provides pre-existing capacity and incentive to enforce protection,
and the concept of marine reserves is readily accepted [67]. Most
logical and enticing to place no-take reserves at sites
reserves, however, are in sites that lack prior community-driven
that function as sources of propagules, rather than at
management structures, and capacity and incentive to enforce
sites that serve as sinks for propagules from elsewhere
regulations must be built. Finally, it must be acknowledged that
[28]. However, current hydrodynamic knowledge does
incentives and stakeholder buy-in are necessary, but not
not enable us to identify source or sink locations
sufficient. Even with strong stakeholder buy-in, some no-take
reserves are well managed [7,67], whereas others are not. Local
without prior monitoring of hydrodynamics at each
management arrangements at the Soufriere Marine Management
location. Neither do we know if there are likely to be
Area [68], at Sumilon Island [69] and in the Fijian qoliqoli [70]
locations that function as permanent sources, as
have proved neither politically stable, nor responsive to exploi-
opposed to locations that are sources on one occasion,
tation pressure [13]. The socioeconomics of no-take reserve
introduction are not yet well understood [49,50], but they must
but not on others.
be married with the science if adaptive management procedures
(v) Finally, we have remarkably few well designed
are to be implemented.
studies of no-take reserves that can rigorously demon-
strate that they have sustained or enhanced fishery
yield in the surrounding region. Solid evidence of
about patterns of larval dispersal is a challenging
recruitment subsidy does not yet exist, and much of
multi-disciplinary task. This is true even for those
the evidence of spillover is equivocal [13,14]. The long-
species with the shortest larval lives, yet many of the
term study of the Apo Island (Philippines) reserve by
important fishery species have relatively long larval
Alcala, Russ and colleagues provides the best example
lives (weeks to months), and are behaviorally compe-
of a reserve-based management program that has
tent pelagic creatures for much of this time. Although
enhanced catches over decadal timescales because of
there is some localized recruitment in species with
spillover [7]. More such studies are needed.
broad geographical ranges [43,44], it is also likely that
Taken together, these gaps in our scientific knowledge
the variance in dispersal distances is high both within
need to be addressed because they prevent development of
and among locations, an important factor ecologically
an explicit science for reserve design, one that can
and evolutionarily.
generate quantitative criteria for use in planning of
(ii) We know more about the patterns of movement
no-take reserve networks. This does not obviate the fact
during the juvenile and adult phases of fishery species,
that criteria other than scientific ones are also important
but even here there are serious gaps in information
(Box 3), and we note that, in the socioeconomic arena,
(Box 2), and movement patterns at these life stages are
there are also gaps in understanding [49,50]. For example,
crucially important in determining the extent of spil-
what is the impact on a fishing community of the
lover from reserves. In addition, some species might be
establishment of a reserve network of particular design,
too mobile for management using reserves to be
and how does that community's response change fish-
practical. It might not be politically possible to
ing effort in the remaining fishable area? These gaps
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Opinion
TRENDS in Ecology and Evolution
Vol.20 No.2 February 2005
are outside the scope of this article, but also need to
test of stated hypotheses, and where the intervention is
be addressed.
intended to be modified on the basis of the results obtained
[52]. Such research should be carefully planned, using an
appropriate BACIP design, so that the results are explicit
How do we fill the gaps in our knowledge?
and powerful tests of hypotheses [14]. This is not the time
MPAs will only be successful if we set them up in the right
to waste opportunities with unreplicated, confounded, or
way and for the right reasons. Only 31% of MPAs
other inadequate experimental designs.
currently meet their management goals, because too
We already know something of the scales of movement
many are set up in the wrong places or with unrealistic
of adults of target species (Box 2), and can investigate how
expectations [51]. We do not advocate delay in the efforts
these lead to spillover from no-take reserves. The key
to improve the sustainability of fisheries, but we believe
issue needing attention is to specify the larval dispersal
that we must recognize the serious gaps in our knowledge
envelopes of target species, and how these determine
and take steps to fill them. The best way to do this is to use
connectivity among populations. New techniques to
the existing science in deliberately adaptive management
investigate this crucial issue are rapidly being developed
approaches for the design and implementation of net-
[53]. With explicit data on larval dispersal, it should be
works of no-take reserves.
possible to adjust reserve size, placement and spacing to
There is a need for targeted funding of research to gain
achieve particular management objectives [22,29,33]. For
the missing biological information for target species
example, if reserves are established at a scale that is
(e.g. mobility, life-history, rates and patterns of settlement
larger than average dispersal distances, they should
and recruitment, connectivity among neighboring popu-
function as marine sanctuaries for biodiversity conserva-
lations, and the status of these populations as either
tion (Figure 1a). No-take fishery reserves, however, should
sources or sinks); as well as physical information about
be sized and spaced within dispersal envelopes for selected
bathymetry, habitat and hydrodynamics at locations being
fishery species as part of the management of surrounding
considered for reserves. Research is also needed into
fisheries (Figure 1b). It should eventually be possible to
effective ways of using no-take reserves in combination
specify optimal number, sizes and specific locations of a
with established methods for controlling fishing effort.
network of no-take reserves to achieve enhancement of
Particularly useful will be cost­benefit approaches to
specific fisheries, while ensuring the sustainability of the
determine the situations under which particular manage-
network through self-recruitment [42]. This will require
ment tools are most effective. Simultaneously, we need to
information about local geography, bathymetry and
identify information bottlenecks and weaknesses in
hydrodynamics in addition to the data on dispersal
foundation principles (if they exist). For example, repro-
patterns [48]. We are not yet close to achieving this, and
duction is often assumed paramount in determining
deliberate use of adaptive management approaches using
demographics of populations, yet stock­recruit relation-
networks of no-take reserves to test hypotheses will be
ships are uncertain in fish, and other ecological factors,
essential if advances are to be made.
such as limits on available nursery habitat, or patterns of
Adaptive management requires the building of a much
connectivity, might be demographically limiting for par-
stronger collaboration between scientists, fishery man-
ticular populations [13,23]. Above all, there is a need for
agers and the fishing community, with all three groups
research manipulations that will empirically test the
recognizing that an effective management intervention
efficacy of no-take reserves as fishery management tools.
will be of benefit to all (Box 3). Research funding agencies,
Because these experiments must be performed at appro-
management agencies, and donor NGOs must recognize
priate spatial and temporal scales, this research should be
that adaptive management done to gain new scientific
done in the context of adaptive management, where the
knowledge is a legitimate activity for funding [16].
management intervention is deliberately varied in space
or time, so that the results can be used as an experimental
Conclusions
No-take reserves are potentially valuable fishery manage-
ment tools, but there are significant gaps in our biological
(a)
(b)
knowledge that currently preclude implementing them
Reserve
Open
with full confidence that they will sustain surrounding
Open
fisheries. These gaps can be filled, but first they must be
acknowledged. Filling them will require a significant
Reserve 1
Reserve 2
investment in targeted research, chiefly in the context of
No. of larvae
No. of larvae
adaptive management, and this will require the develop-
Dispersal distance
Dispersal distance
ment of strong collaborations among the scientific, the
TRENDS in Ecology & Evolution
management and the fishing communities. The most
Figure 1. The size and spacing of no-take reserves with respect to dispersal
crucial questions concern connectivity and the anticipated
distances of the species of interest. Reserves intended for conservation (a) should
recruitment subsidy that this should make possible.
be large enough to retain a substantial portion of larval dispersal to ensure
Answering these questions will enable the development
adequate self-recruitment. For fisheries enhancement (b), they should be sized and
spaced to enable a significant proportion of larvae to disperse to surrounding
of more explicit rules concerning size, placement and
fished areas. Distance is measured from the center of the reserve (at the origin) and
spacing of reserves, the amount of habitat that needs to be
the dispersal curve is drawn with respect to larvae produced there. [Shaded areas
protected, and the most appropriate ways of combining
are reserves; dotted lines, reserve boundaries. For simplicity in (b), the dispersal of
larvae produced in reserve no. 2 is not included].
no-take reserves with other management tools. There is
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Opinion
TRENDS in Ecology and Evolution
Vol.20 No.2 February 2005
79
risk in proceeding to implement no-take reserves without
22 Botsford, L.W. et al. (2001) Dependence of sustainability on the
simultaneously seeking to fill the knowledge gaps, yet
configuration of marine reserves and larval dispersal distance. Ecol.
Lett. 4, 144­150
there exists a great urgency to develop more effective tools
23 Kritzer, J.P. and Sale, P.F. (2004) Metapopulation ecology in the sea:
for the sustainable management of coastal fisheries.
from Levins' model to marine ecology and fisheries science. Fish Fish.
Building sustainable coastal fisheries has considerable
5, 131­140
benefits beyond those to the fishing community, but
24 DeMartini, E.E. (1993) Modelling the potential of fishery reserves for
achieving these benefits will be difficult and will require
managing Pacific coral reef fishes. Fish. Bull. 91, 414­427
25 Carr, M.H. and Reed, D.C. (1993) Conceptual issues relevant to
that we explore possible tools carefully and rigorously,
marine harvest refuges: examples from temperate reef fishes. Can.
while using them to the best of our current capability.
J. Fish. Aquat. Sci. 50, 2019­2028
Acknowledging the gaps in knowledge is the first step in
26 Quinn, J.F. et al. (1993) Harvest refugia in marine invertebrate
building a more effective science of no-take reserves.
fisheries: models and applications to the red sea urchin, Strongylo-
centros franciscanus. Am. Zool. 33, 537­550
27 Sladek Nowlis, J. and Roberts, C.M. (1999) Fisheries benefits and
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This article grew out of discussions among several members of the
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Connectivity Working Group, within the global research program Coral
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Reef Targeted Research for Capacity Building and Management (http://
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www.gefcoral.org). It benefited greatly from the comments of three
reserves. Ecol. Appl. 13, S25­S31
anonymous referees.
30 Gerber, L.R. et al. (2003) Population models for marine reserve design:
a retrospective and prospective synthesis. Ecol. Appl. 13, S47­S64
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