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The study and implementation of no-take marine reserves have increased rapidly over the past decade, providing ample data on the biological effects of reserve protection for a wide range of geographic locations and organisms. The plethora of new studies affords the opportunity to re- evaluate previous findings and address formerly unanswered questions with extensive data synthe- ses. Our results show, on average, positive effects of reserve protection on the biomass, numerical density, species richness, and size of organisms within their boundaries which are remarkably simi- lar to those of past syntheses despite a near doubling of data. New analyses indicate that (1) these results do not appear to be an artifact of reserves being sited in better locations; (2) results do not appear to be driven by displaced fishing effort outside of reserves; (3) contrary to often-made asser- tions, reserves have similar if not greater positive effects in temperate settings, at least for reef ecosystems; (4) even small reserves can produce significant biological responses irrespective of lati- tude, although more data are needed to test whether reserve effects scale with reserve size; and (5) effects of reserves vary for different taxonomic groups and for taxa with various characteristics, and not all species increase in response to reserve protection. There is considerable variation in the responses documented across all the reserves in our data set — variability which cannot be entirely explained by which species were studied. We suggest that reserve characteristics and context, par- ticularly the intensity of fishing outside the reserve and inside the reserve before implementation, play key roles in determining the direction and magnitude of the reserve response. However, despite considerable variability, positive responses are far more common than no differences or negative responses, validating the potential for well designed and enforced reserves to serve as globally important conservation and management tools.
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Mar Ecol Prog Ser
Vol. 384: 3346, 2009
doi: 10.3354/meps08029
Published May 29
The world’s oceans face an increasing number and
severity of threats, including overexploitation of living
marine resources, habitat degradation and destruction,
pollution, and climate change impacts (Harley et al.
2006, UNEP 2006, Halpern et al. 2008, Jackson 2008).
These various stressors in turn lead to depleted popula-
tions of economically and culturally important species,
altered community structure, and compromised eco-
© Inter-Research 2009 ·*Email:
Biological effects within no-take marine reserves:
a global synthesis
Sarah E. Lester
, Benjamin S. Halpern
, Kirsten Grorud-Colvert
, Jane Lubchenco
Benjamin I. Ruttenberg
, Steven D. Gaines
, Satie Airamé
, Robert R. Warner
Marine Science Institute, University of California, Santa Barbara, California 93106-6150, USA
National Center for Ecological Analysis and Synthesis, 735 State Street, Suite 300, Santa Barbara, California 93101, USA
Department of Zoology, 3029 Cordley Hall, Oregon State University, Corvallis, Oregon 97331-2914, USA
National Marine Fisheries Service, Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, Florida 33149, USA
Department of Ecology, Evolution, and Marine Biology and Marine Science Institute, University of California,
Santa Barbara, California 93106-9610, USA
ABSTRACT: The study and implementation of no-take marine reserves have increased rapidly over
the past decade, providing ample data on the biological effects of reserve protection for a wide range
of geographic locations and organisms. The plethora of new studies affords the opportunity to re-
evaluate previous findings and address formerly unanswered questions with extensive data synthe-
ses. Our results show, on average, positive effects of reserve protection on the biomass, numerical
density, species richness, and size of organisms within their boundaries which are remarkably simi-
lar to those of past syntheses despite a near doubling of data. New analyses indicate that (1) these
results do not appear to be an artifact of reserves being sited in better locations; (2) results do not
appear to be driven by displaced fishing effort outside of reserves; (3) contrary to often-made asser-
tions, reserves have similar if not greater positive effects in temperate settings, at least for reef
ecosystems; (4) even small reserves can produce significant biological responses irrespective of lati-
tude, although more data are needed to test whether reserve effects scale with reserve size; and
(5) effects of reserves vary for different taxonomic groups and for taxa with various characteristics,
and not all species increase in response to reserve protection. There is considerable variation in the
responses documented across all the reserves in our data set variability which cannot be entirely
explained by which species were studied. We suggest that reserve characteristics and context, par-
ticularly the intensity of fishing outside the reserve and inside the reserve before implementation,
play key roles in determining the direction and magnitude of the reserve response. However, despite
considerable variability, positive responses are far more common than no differences or negative
responses, validating the potential for well designed and enforced reserves to serve as globally
important conservation and management tools.
KEY WORDS: Marine reserves · Temperate · Tropical · Fishes · Invertebrates · Algae · Marine
Protected Area · Conservation
Resale or republication not permitted without written consent of the publisher
Mar Ecol Prog Ser 384: 3346, 2009
system functioning and delivery of services. The scope of
these changes spans many habitats, species, and dif-
ferent trophic levels, and thus may require more
holistic, ecosystem-based management approaches
(Lubchenco et al. 2003, Browman & Stergiou 2004,
UNEP 2006). Because marine reserves protect all species
and habitats in an area from extractive activities, they
are a central tool for ecosystem-based management and
offer hope for mitigating some of the threats affecting
coastal and marine systems (Worm et al. 2006).
Marine reserves are defined here as ‘areas of the
ocean completely protected from all extractive and
destructive activities… except as necessary for moni-
toring or research’ (Lubchenco et al. 2003, p. S3).
Marine reserves are an important subset of Marine
Protected Areas (MPAs). MPAs vary greatly in their
regulations and their utility for conservation likely
varies considerably based on the level of protection
afforded, making it difficult to generalize about the
benefits of MPAs (Mora et al. 2006, Lester & Halpern
2008). Although MPAs with less restrictive regulations
are undoubtedly important management tools, no-take
marine reserves offer the greatest protection for
marine resources and ecosystems and thus are the sole
focus of the present study. Marine reserves have
received increasing attention over the last few decades
as an important management strategy for both conser-
vation and fisheries management goals (Halpern 2003,
Halpern & Warner 2003, Palumbi et al. 2003, Leslie
2005, Claudet et al. 2008, White et al. 2008).
Numerous syntheses of monitoring studies have
documented how population numbers and biomass, or-
ganism size, species richness, reproductive potential,
and/or community structure are affected by reserve
protection (Halpern & Warner 2002, Palumbi 2002, Gell
& Roberts 2003, Halpern 2003, Micheli et al. 2004).
Many of these studies suggest that beneficial effects of
reserve protection are common. This is particularly ev-
ident when comparing numerical density and biomass
of exploited species inside and outside reserves and/or
before and after reserve protection (Côté et al. 2001,
Gell & Roberts 2003, Halpern 2003). On the other hand,
some authors have suggested that the impacts of re-
serves may be idiosyncratic, varying with the goal(s) set
by the body or institution establishing the reserve,
whether the reserve is part of a network of reserves, the
location, size, and protection duration of the reserve,
and the characteristics of the species under considera-
tion (Jennings 2000, Mosqueira et al. 2000, Côté et al.
2001, Micheli et al. 2004, Kaiser 2005, Claudet et al.
2008). Therefore, although there is encouraging evi-
dence that reserves are an effective management
option for restoring and sustaining marine ecosystems
within their boundaries, some important questions
about the utility of reserves remain unresolved.
In particular, contention exists about whether
reserve effects will be different in temperate versus
tropical regions (Blyth-Skyrme et al. 2006). A number
of authors have suggested that temperate reserves
might result in smaller or no changes in exploited spe-
cies because of 2 primary reasons. (1) Exploited spe-
cies in temperate regions tend to be more mobile and
are thus less likely to benefit from a reserve (Shipp
2003, Kaiser 2004). If most individuals stray beyond
reserve borders, their populations will not be effec-
tively protected. (2) Temperate species and popula-
tions tend to have longer larval durations and thus
greater larval dispersal potential and gene flow than
their tropical counterparts (Laurel & Bradbury 2006,
O’Connor et al. 2006).
Given potentially higher rates of adult movement
and larval export, it has been suggested that reserves
in temperate systems may need to be larger than tropi-
cal reserves to achieve comparable results (Laurel &
Bradbury 2006). Comparisons across reserves in differ-
ent locations suggest that changes in biological metrics
do not vary appreciably with reserve size (Côté et al.
2001, Halpern 2003, Micheli et al. 2004, Guidetti &
Sala 2007, but see Claudet et al. 2008). However,
reserve size has not been examined with respect to
geographical differences among reserves. Addition-
ally, there is a perception that most of the positive
effects of marine reserves have been documented in
tropical systems or that tropical reserves have received
more attention in scientific studies (Blyth-Skyrme et al.
2006, Laurel & Bradbury 2006). In fact, there are many
scientific studies of temperate reserves, with peer-
reviewed publications from a variety of regions (see
Fig. 1) such as Australia, New Zealand, the Mediter-
ranean, North America, South America, and South
Africa (e.g. Paddack & Estes 2000, Manriquez &
Castilla 2001, Shears & Babcock 2003, Mayfield et al.
2005, Micheli et al. 2005). However, the present study
is the first meta-analysis explicitly comparing the
results from tropical and temperate reserves.
Marine reserve protection is also likely to affect indi-
vidual species differently, based on whether they are
exploited or otherwise affected by activities outside
the reserve; biological characteristics such as mobility,
dispersal ability, longevity, and fecundity; the nature of
density dependence; and indirect effects resulting
from interactions with other species that are directly
affected by reserve protection (Mosqueira et al. 2000,
Fisher & Frank 2002, Gaines et al. 2003, Micheli et al.
2004, Gaylord et al. 2005, Gerber et al. 2005, Kaiser
2005). Although different responses may be expected
for different taxonomic groups, this issue has primarily
been investigated for fish species (e.g. Micheli et al.
2004). However, there is a growing body of data not
only for fishes, but also for invertebrates and algae
Lester et al.: Biological effects within marine reserves
from a range of geographic locations. In the present
study, we investigate differences among broad taxo-
nomic groupings and among invertebrate and algal
functional groups in both tropical and temperate
Impacts of marine reserves generally fall into 2
broad categories: changes occurring inside versus
those occurring outside the reserve. The latter includes
both spillover of individuals from the reserve to the
outside (Gell & Roberts 2003, Sale et al. 2005,
B. S. Halpern et al. unpubl. data) and export of larvae
from the reserve (Botsford et al. 2001, Palumbi 2003).
Because it is more straightforward to assess effects
inside reserves and data are therefore more compara-
ble and more readily available, this review will focus
exclusively on effects within reserves by expanding
the global assessment of reserve effects on basic bio-
logical measures. Specifically, we evaluate (1) the bio-
logical effects of marine reserves and whether these
effects are likely an artifact from using primarily inside
versus outside reserve comparisons, (2) whether
reserves in temperate waters perform similarly to
reserves in tropical systems, and (3) the magnitude of
the biological effects of marine reserves on different
taxonomic and functional groups.
We conducted a comprehensive survey of the peer-
reviewed scientific literature to compile a database of
studies that document biological effects of marine
reserves (Table S1, available in MEPS Supple-
mentary Material at
m384p033_app.pdf). We included only peer-reviewed
studies of fully-protected, no-take marine reserves and
only those studies for which effects were measured for
individual reserves. Studies must have measured at
least 1 of 4 key biological variables (numerical density
or biomass/area of organisms, individual organism
size, or species richness/area) and must have quanti-
fied the variable(s) either (1) inside and outside the
reserve, (2) before and after reserve implementation,
or (3) inside and outside the reserve both before and
after implementation. Throughout the text, tables, and
figures, density refers to numerical density, not other
density measures such as biomass.
The resulting database contains 149 peer-reviewed
scientific publications published between 1977 and
2006 of 124 different marine reserves located in 29
countries (Fig. 1). Because some reserves were studied
in more than one publication and some publications
studied multiple reserves, the database includes 221
‘studies.’ For most of the reserves in the database (n =
108), we were able to find a reliable estimate of its area
). We classified each reserve as being located in
either a temperate (n = 53) or tropical (n = 71) ecosys-
tem based on latitude, region, and habitat.
For each study, we extracted quantitative data from
text, tables, and figures for the 4 biological variables
inside and outside the reserve, before and after imple-
mentation, or inside and outside the reserve before
and after implementation. Data were extracted at the
most aggregated taxonomic level available, even if the
Fig. 1. Marine reserves (
, n = 124) for which peer-reviewed scientific data are available (comment callouts indicate the number
of reserves studied in different areas)
Mar Ecol Prog Ser 384: 3346, 2009
level of taxonomic resolution differed within or among
studies. For example, if a study reported data for par-
ticular fish families in addition to species level data for
other fish families, all of these data were extracted (but
species-level data for a fish family for which family-
level data were reported would not be extracted). If a
study reported data in categories for both the reserve
and control area (e.g. by depth, habitat type, or organ-
ism size classes), these values were averaged into sin-
gle values. If multiple time steps of data were reported
for an Outside/Inside comparison, we used the most
recent data because they represent the longest dura-
tion of protection. In order to be used as a before/after
or Before/After/Inside/Outside comparison, ‘before’
data must have been collected no later than 3 mo after
reserve establishment. If data were collected at multi-
ple times before reserve implementation, the data from
the ‘before’ time steps were averaged unless there was
an obvious trend prior to implementation (in which
case the most recent data prior to implementation were
extracted). We always used the most recent ‘after’ data
to represent the longest duration of protection.
For algae and invertebrates, in addition to extracting
data at the most aggregated taxonomic level, we also ex-
tracted data at the least aggregated taxonomic level
available (i.e. ideally at the species level, but genera
level or higher if species data were not reported). We as-
signed each algal datum to a morphological functional
group, using a modified version of the categories devel-
oped by Steneck & Dethier (1994): crustose algae, fila-
mentous algae, articulated calcareous algae, corticated
foliose algae, corticated macrophytes, and leathery
macrophytes. For the invertebrate data, we assigned
each datum to a phylum and a lower taxonomic group
(Table 1). We also classified the invertebrates based on
characteristics that might influence the effect of reserve
protection on biological metrics, including target status,
trophic level, larval dispersal potential, and adult mobil-
ity (Table S2, available at
suppl/m384p033_app.pdf). These data were examined
in algae-only and invertebrate-only analyses to deter-
mine characteristics of these taxa that may mediate a re-
serve effect.
To quantify the effect of reserve protection using a
comparable metric across studies, we calculated res-
ponse ratios of the 4 biological variables as (1) the ratio
of Inside to Outside, (2) the ratio of After to Before, or
(3) the ratio of After to Before within the reserve, con-
trolling for temporal changes outside the reserve
Outside]). Using the extracted data, we calculated
response ratios within each study for each biological
variable. When data were extracted for multiple taxa
in a given study, we then averaged these response
ratios to determine the overall (study) ratio for all taxa
examined, regardless of how many species/taxa were
studied. Overall (study) ratios represent from one to
several hundred species depending on the study. Fur-
thermore, if a study reported data separately for more
than one of our broad taxonomic groups (fishes, inver-
tebrates, and algae), we calculated an average for each
group first and then averaged these group values to
determine the overall ratio. This was done to give the
best estimates of community-level responses; although
in very few cases did this procedure yield a different
value than the value obtained by averaging all data
without calculating taxonomic group averages first.
Some reserves have been the subject of numerous
published studies. We did not want to bias our analyses
in favor of the most frequently studied reserves, so we
calculated the average reserve ratio from all of the
study ratios (and again for taxonomic group, algae-
only, and invertebrate-only study ratios) for reserves
that were the subject of more than one study. We chose
to calculate a reserve average rather than using the
most recent study because often different studies of the
same reserve varied in the taxa measured, the survey
methods used, or in the investigators conducting the
research. For reserves that were the subject of a single
study, the reserve ratio is equivalent to the study ratio.
We converted the ratios to percentage increases or
decreases to facilitate interpretation ([response ratio –
1] × 100; e.g. a density response ratio of 2.5 is equal to
a 150% increase). These procedures were repeated for
each of the 4 biological response variables.
The vast majority of the studies in our database
(>90%) compared data from inside versus outside the
reserve. Because reserves can have effects outside
their boundaries, using Inside versus Outside compar-
isons could potentially mask (because of larval export
or adult spillover) or exaggerate (because of displace-
Table 1. Taxonomic classifications used for invertebrate-only
Phylum Taxonomic group
Mollusca Gastropods
Echinodermata Urchins
Sea cucumbers
Arthropoda Barnacles
Hermit crabs
Cnidaria Hard corals
Soft corals
Anthozoa (hard and soft corals)
Porifera Sponges
Annelida Polychaetes
Lester et al.: Biological effects within marine reserves
ment of fishing effort or being placed in areas with bet-
ter habitat) a true positive reserve effect. To address
these issues, we examined the 23 studies in our data-
base with data inside and outside of the reserve, before
and after reserve implementation. For these studies,
we calculated response ratios of (1) Inside-Before ver-
sus Outside-Before to test whether reserves are placed
in ‘better’ locations, and (2) Outside-Before versus
Outside-After to assess whether we might be under- or
overestimating a reserve effect due to changes outside
of the reserve (Halpern et al. 2004).
For all statistical analyses, we used the log of each ra-
tio (Hedges et al. 1999) and the log of reserve size to
meet statistical criteria and conducted all statistical tests
using JMP 6.0 or SAS 9.1 (SAS Institute). We analyzed
these data to answer 3 primary questions: (1) Are den-
sity, biomass, individual size, or species richness signif-
icantly and consistently affected by reserve protection?
(2) Do changes in biomass, density, size, or richness in-
side a reserve differ in temperate versus tropical regions?
and (3) Do the effects of reserves vary by taxonomic
group or characteristics of the taxa under consideration?
Biological effects within marine reserves
Examining the global data set, reserve protection re-
sulted in statistically significant increases of all 4 of the
key biological variables that we examined (Fig. 2). The
most dramatic increases occurred in biomass and den-
sity of organisms within reserves (respectively, 446 and
166% average increases, 194 and 61% median in-
creases). Individual size and species richness both
showed positive but more moderate responses to re-
serve protection (respectively, 28 and 21% average in-
creases, 17 and 15% median increases), a noteworthy
result given that both of these parameters have much
lower scope for change relative to density or biomass
(the product of increases in individual size and den-
sity). For example, a 20% increase in the average size
of individuals (reported as linear measurements, e.g.
total length or carapace width) is equivalent to a much
larger increase in individual biomass given the expo-
nential relationship between length and weight. Fur-
thermore, in addition to species richness having lower
scope for change than density or biomass, reserve
studies tend to quantify richness using species counts
over a relatively small sample area (e.g. transect) and
thus may often underestimate total species richness.
The global reserve effects presented here are consis-
tent with previous analyses of fewer reserves (Halpern
& Warner 2002, Palumbi 2002, Gell & Roberts 2003,
Micheli et al. 2004). Our average reserve mean res-
ponses are very similar to those of Halpern’s (2003)
smaller data set (present study vs. Halpern’s [2003]
biomass: 446 vs. 352%; density: 166 vs. 151%;
organism size: 28 vs. 29%; species richness: 21 vs.
25%; Halpern 2003 percentages were calculated using
mean reserve responses and excluding the few studies
that did not meet the criteria used here, e.g. gray liter-
ature). Our substantially expanded data set illustrates
that these biological impacts are robust. However, it is
important to note the reserves in our data set may be
better enforced than most. Many existing reserves
have inadequate enforcement and high levels of
poaching and as a result will show smaller or no
responses to protection (e.g. Guidetti et al. 2008).
Although the vast majority of response ratios for all
metrics indicated positive changes in reserves, the
magnitude of the response varied enormously (Fig. 2).
This variability is not surprising given that there are a
host of factors that can affect both the magnitude and
direction of an individual reserve response, including
the species studied, characteristics of the reserve, and
activities occurring outside the reserve or inside the
reserve prior to protection. Furthermore, the distribu-
tion of responses had a pronounced skew for both bio-
mass and density, with a few very large positive val-
ues. For these 2 metrics, the average response was
substantially higher than the median response. Given
the large variance in all metrics and the skew in some,
the average response may be a poor predictor of the
Biomass Density Size Richness
Change in biological measures (%)
N = 55 N = 118 N = 51 N = 39
Fig. 2. Average (gray bars) and median (
) percent change in
biomass, density, organism size, and species richness calcu-
lated from reserve response ratios. All 4 biological variables
show statistically significant increases (1-sample 2-tailed
t-tests, p < 0.0001 for biomass, density, and organism size and
p = 0.002 for species richness). (
) Individual reserve respon-
ses. N: number of reserves for which each biological variable
was measured
Mar Ecol Prog Ser 384: 3346, 2009
expected magnitude of response for any individual
species, group of species, or an entire community
within any particular reserve.
There was considerable variation in the number of
species examined among the studies in our database,
and studies examining more species might be expec-
ted to show lower responses because they average
across species with positive and negative responses.
However, there is no indication that our results are
biased by the inclusion of studies investigating only a
single or small number of species. We examined
response ratios as a function of the number of species
measured in each study; while there tends to be a
wider range of responses (higher variance) for studies
looking at a single or small number of species, the
mean response ratio for each biological measure is rel-
atively constant for studies looking at one or a few spe-
cies compared to studies measuring an increasing
number of species (p > 0.1 for all 4 biological variables)
(Fig. 3). Thus, given the consistency of positive res-
ponse ratios in this broad synthesis and their large
median and average values, there is strong evidence
that marine reserves have important positive biological
effects within their boundaries.
A more detailed examination of some of the higher
values in our data set illustrates some of the factors
that influence reserve responses, drawing particular
attention to how intense fishing and subsequently ex-
tremely low levels of studied species outside the
reserve can lead to exceptional positive responses. The
highest density datum (+2210%) is the Las Cruces
Reserve in Chile, which represents the average of 5
studies measuring a variety of taxa including intertidal
fishes, gastropods, and algae. Of these studies, the 2
with the highest values both quantified the density
of an economically important gastropod species,
Conchelepas conchelepas (loco), which was incredibly
rare everywhere prior to reserve implementation and
Organism size
No. species studied
Log (response ratio)
Species richness
Fig. 3. Average study response ratios by number of species studied. Study response ratios were calculated using those studies for
which we could determine the number of species measured within the following ranges: 15, 610, 1120, 2150, 51100, and
>100 species. Linear regression models were constructed for each biological variable using the mean study ratio in each bin
(y-variable) and the midpoint of each bin (x-variable). Error bars: ±SD. Numbers above error bars: number of studies included in
each data point. All regressions are non-significant (biomass: R
= 0.028, p = 0.751; density: R
= 0.259, p = 0.302; organism size:
= 0.105, p = 0.521; richness: R
= 0.027, p = 0.790)
Lester et al.: Biological effects within marine reserves
outside the reserve after protection (Castilla & Duran
1985, Manriquez & Castilla 2001). The highest biomass
datum (+2800%) is the Bongalonan Reserve in the
Philippines, the subject of a single study measuring
large predatory fishes in the families Serranidae, Lut-
janidae, and Lethrinidae (Russ et al. 2005). As a third
example, the second highest biomass datum is the sub-
ject of a study that examined a single economically
important species; in the Governor Island reserve in
Australia, rock lobster biomass was documented to be
2300% higher inside the reserve, due to very low bio-
mass levels of lobster outside the reserve (Edgar & Bar-
rett 1999). While such extreme positive responses are
rare, half of the reserve sites show biomass changes
exceeding a 200% increase and density changes
exceeding a 60% increase.
Some reserves show decreases in key biological vari-
ables. Several of the decreases in density are from a
study in which percent cover of live hard coral was
quantified for numerous reserves in the Philippines
(Russ et al. 2005), with some reserves showing higher
coral cover outside the reserve. For example, live coral
cover was 64% lower inside the Canlucani Reserve
after 2 yr of protection. Given the slow growth rates of
hard corals, they may be slow to recover inside re-
serves. Although we did not examine the effect of
duration of protection in the present study, it has been
shown to be an important factor in explaining recovery
of previously overfished ecosystems, particularly for
slower growing species (e.g. Russ & Alcala 2004).
Species richness decreased in a number of reserves,
several of which are South African intertidal reserves
in the Transkei region (Hockey & Bosman 1986).
Hockey & Bosman (1986) found that intense human
collecting acts as a source of disturbance, promoting
coexistence among otherwise competing prey species,
thereby increasing intertidal richness in unprotected
areas. Whether we would predict an increase or de-
crease in species diversity in response to reserve pro-
tection likely depends on the level of human distur-
bance (i.e. fishing pressure) and predation in the
system. As expected from the intermediate distur-
bance hypothesis and community succession theory
(Connell 1978), diversity is likely to increase in re-
serves when fishing outside is more intense but may
decrease in reserves when fishing is moderate to light
outside the reserve. This is corroborated by studies
examining reef fish biomass, density, and diversity
over a gradient of human disturbance; with decreasing
human disturbance, biomass increases consistently
while density and diversity increase until top predators
accumulate a threshold fraction of the total biomass in
the system, leading to a decline in their prey (e.g.
Sandin et al. 2008). This suggests that biomass may
often be the best indicator of reserve performance.
Lastly, most of the data used in these analyses are
from inside versus outside comparisons, as is true of
other marine reserve meta-analyses. Thus, a general
positive reserve effect may be an artifact of reserves
being placed in better habitat or areas otherwise better
able to support larger numbers and sizes of organisms.
Alternatively, a positive reserve effect could be caused
by the reserve displacing fishing effort to areas out-
side. In other words, if the outside ‘control’ area is
faced with increasing fishing pressure due to reserve
establishment, decreasing numbers or biomass of tar-
get species in these fished areas would lead to a posi-
tive response ratio even if there has been no change
within the reserve.
Reserves do not appear to be placed in fundamen-
tally better locations based on a comparison of biologi-
cal measurements taken inside and outside of future
Difference in biological variables (%)
p = 0.51 p = 0.21 p = 0.06 p = 0.25
Biomass Density Size Richness
N = 6 N = 19 N = 6 N = 7
p = 0.02* p = 0.15 p = 0.73 p = 0.14
Fig. 4. Average (gray bars) percent difference in biomass,
density, organism size, and species richness calculated from
the ratios Inside-Before:Outside-Before (top panel) or Out-
side-After:Outside-Before (bottom panel). (
) Individual
study responses. None of the biological variables show
responses that are statistically different from zero, with the
exception of biomass for the Outside-After:Outside-Before
comparison (1-sample, 2-tailed t-tests). N: number of studies
for which each biological variable was measured
Mar Ecol Prog Ser 384: 3346, 2009
reserves before they are established (Fig. 4, top panel).
While these response ratios are positive, they are not
statistically significant (1-sample, 2-tailed t-tests,
hypothesis mean log response ratios significantly dif-
ferent than zero, p > 0.2 for biomass, density, and
organism size and p = 0.06 for species richness). Fur-
thermore, if the large increases in biological measures
observed in the global data set (Fig. 2) were only a
result of reserve placement, we would expect a signif-
icant effect in the Inside-Before:Outside-Before analy-
ses at a power of 0.95 for density and 0.84 for biomass
given their sample sizes (power analysis using error SD
from the global analysis).
Areas outside reserves did not show declines in bio-
logical measures following reserve establishment. In
fact, outside areas either exhibited no change or, in the
case of biomass, a significant increase after the reserve
was in place (Fig. 4, bottom panel; p = 0.02 for biomass
and p > 0.1 for density, organism size, and species rich-
ness). This increase suggests that reserves may benefit
outside areas, possibly through the spillover of adults
or the export of larvae over the long term. Thus, the
global synthesis results may actually be underestimat-
ing the reserve effect given the large number of inside
versus outside comparisons and their potential to show
no change or slight increases outside reserves through
adult spillover or larval export. Of course, these results
must be interpreted with caution given that the sample
sizes for these Before-After-Inside-Outside compar-
isons are much smaller than those for the global data
Marine reserves in temperate versus tropical
Despite the perception that many of the important
fished species in temperate waters are too mobile or
long-lived to be effectively protected by reserves
(Shipp 2003, Blyth-Skyrme et al. 2006), we found that
reserves in temperate environments tend to show
effects that are as large, and in some cases larger, than
those documented for reserves in the tropics (Fig. 5).
The effects of marine reserve protection on individual
size and species richness were similar across geo-
graphical regions (2-tailed t-tests, size: p = 0.759; rich-
ness: p = 0.133). For biomass and density, there was a
slight trend towards greater positive responses in tem-
perate systems (biomass: p = 0.076; density: p = 0.097).
Given the tendency for temperate species to have
higher adult mobility and longer larval dispersal rela-
tive to tropical species, it has been suggested that tem-
perate reserves need to be far larger than is politically,
socially, or economically feasible to meet stated man-
agement goals (Shipp 2003, Laurel & Bradbury 2006).
In our database, however, temperate reserves did not
differ from the tropical reserves in average area or in
their distribution of areas (t-test, p = 0.80; Kolmogorov-
Biomass Density
Change in biological variables (%)
Organism size Species richness
Mean of temperate reserves
Mean of tropical reserves
N = 23 N = 32 N = 51 N = 67
N = 29 N = 22 N = 21 N = 18
Fig. 5. Average (gray bars) and median (
) percent change in
biomass, density, organism size, and species richness, calcu-
lated from reserve response ratios, with data plotted sepa-
rately for reserves in temperate versus tropical environments.
(d) Individual reserve responses. Percent increases by envi-
ronment are statistically significant in all cases except species
richness in temperate reserves (1-sample, 2-tailed t-tests, tem-
perate reserves: p < 0.0001 for biomass, density, and size and
p = 0.166 for richness; tropical reserves: p < 0.0001 for biomass
and density, p = 0.0002 for size, and p = 0.003 for richness)
Lester et al.: Biological effects within marine reserves
Smirnov test, p = 0.376; n = 108). When we examined
the studies for which a reliable estimate of reserve area
was available, we found that reserve size does not
appear to influence the relative magnitude of the
reserve protection response for any of the 4 key biolog-
ical variables, controlling for tropical versus temperate
environment (Fig. 6). In fact, all relationships between
reserve size and a response variable were non-
significant with the exception of organism size (p =
0.034), and this relationship was negative in both tem-
perate and tropical environments. Ecologically, a neg-
ative relationship between reserve size and biological
variables is counterintuitive. However, these negative
relationships are influenced by single outlier points
(the smallest reserve in both analyses), which exert
considerable leverage on the regressions (Cook’s D =
0.34 and 0.57; all other points, Cook’s D < 0.1). Both of
these points are reserves represented by a single
invertebrate species: a relatively fast-growing branch-
ing coral in a tropical Israeli reserve (Coral Beach
Reserve, 6 yr of protection at time of study) and an
exploited gastropod species in a temperate Chilean
reserve (Las Cruces Reserve, 11 yr). These data de-
monstrate that in some cases even small reserves can
result in dramatic increases in average individual size,
particularly when studies examine fast growing,
largely immobile species that are heavily impacted
outside the reserve. If these 2 points are removed, the
relationship between reserve size and organism size
response becomes non-significant (R
= 0.032, p =
0.729, n = 43; effect tests, reserve size: p = 0.263, eco-
system: p = 0.702, interaction term: p = 0.722).
The finding that reserve responses are not mediated
by the size of the protected area is generally consistent
with prior reviews (Gell & Roberts 2003, Halpern 2003,
Micheli et al. 2004). However, the marine reserves in
our database (median size = 3.3 km
) and those of prior
studies tend to be relatively small, potentially limiting
Log(response ratio)
Organism size
Reserve size (km
0.001 0.01 0.1 1 10 100 1000
0.001 0.01 0.1 1 10 100 1000 0.001 0.01 0.1 1 10 100 1000
0.001 0.01 0.1 1 10 100 1000
Species richness
p = 0.125
p = 0.034
p = 0.094
p = 0.277
Fig. 6. Overall temperate and tropical marine reserve response ratios by reserve size and ecosystem. Linear regression models
constructed with log(reserve size), ecosystem, and the reserve size × ecosystem interaction predicting log(response ratio) were fit
separately for each metric. Non-significant regression lines (p > 0.05) are shown by dotted (tropical) or dashed (temperate) lines
and significant regression lines (p < .05) are shown by solid lines (each line drawn along the x-axis over the range of the data).
The significant relationships for organism size are both driven by single outlier points (see ‘Results and discussion’ for more
details (biomass: n = 53, R
= 0.075, p = 0.277; interaction term: p = 0.399; density: n = 103, R
= 0.062, p = 0.094; interaction term:
p = 0.638; organism size: n = 45, R
= 0.189, p = 0.034; effect tests, reserve size: p = 0.004, ecosystem: p = 0.500, interaction term:
p = 0.757; species richness: n = 37, R
= 0.157, p = 0.125; interaction term: p = 0.05)
Mar Ecol Prog Ser 384: 3346, 2009
any meaningful tests of the effect of
reserve size on biological responses. Our
database also contains comparatively few
studies examining highly mobile or
migratory species for which reserve size
may be a more critical factor. Lastly,
given all the sources of variation influ-
encing the reserve response (e.g. charac-
teristics of the species studied, intensity
of exploitation outside the reserve), it
may also be difficult to detect an effect of
reserve size across such a wide range of
studies. Neither the present study nor
most of the prior reviews were able to
examine how the same suite of species
responds to reserves of different sizes, an
analysis that would provide a more defin-
itive answer. Edgar & Barrett (1997) stud-
ied 4 Tasmanian reserves and Claudet et
al. (2008) studied 12 reserves in the
Mediterranean and northeast Atlantic
and both found evidence that biological
responses may in fact scale with reserve
size. Importantly, our results, for which
the per unit area biological measures
scale linearly with reserve size, do not
suggest that reserve size is unimportant;
for example, a doubling of per unit area
biomass results in far more total biomass
in a large versus small reserve.
Differential effects of reserve protection
among taxonomic groups
Because reserve responses are likely to
vary for different types of organisms, we
examined reserve responses by broad
taxonomic groupings (e.g. algae, inverte-
brates, and fishes) as well as different
types of functional groups. Algal data did
not have adequate sample sizes for any of
the variables except density, for which
there was no significant overall effect of
reserves (Fig. 7). However, there was a tendency for
temperate reserves to show higher density response
ratios than tropical reserves (t-test, p = 0.089), with
tropical reserves actually showing an average de-
crease in algal cover. This difference in the effect of
reserve protection on algae in tropical versus temper-
ate reserves matches typical expectations of reserve
performance. Most tropical reserves include coral
reefs, where a decline in algal abundance can lead to
an increase in coral cover due to decreased spatial
competition between algae and corals. In this situation,
reserves can protect the herbivorous fishes that are fre-
quently targeted by fishing, which reduce algal cover
on the reef (Williams & Polunin 2001, Mumby et al.
2006). In contrast, temperate reserves, particularly
those in rocky reef habitats, often protect species that
prey on urchins (the dominant herbivore in these sys-
tems), leading to an increase in algal cover.
Invertebrates and fishes showed significant positive
average responses across all reserves for all 4 biologi-
cal measures, with the exception of invertebrate spe-
cies richness (Fig. 7). In comparison to fishes, inverte-
Algae Invertebrates Fish
Change in biological variables (%)
Mean of temperate reserves
Mean of tropical reserves
Algae Invertebrates Fish
Organism size
Algae Invertebrates Fish Algae Invertebrates Fish
N = 0, N = 22, N = 15, N = 4, N = 5, N = 17,
N = 0 N = 11 N = 14 N = 0 N = 0 N = 18
Species richness
Mean of all reserves
N = 2, N = 11, N = 15, N = 17, N = 33, N = 35,
N = 0 N = 1 N = 31 N = 5 N = 38 N = 46
Fig. 7. Average (gray bars) and median (
) percent change in biomass, density,
organism size, and species richness calculated from marine reserve response
ratios by taxonomic groupings. Average responses were significantly greater
than no change (1-sample, 2-tailed t-tests, p < 0.01) with the exception of algal
responses (density: p = 0.538; biomass: n = 2; size: no data; richness: p = 0.420)
and invertebrate richness (p = 0.469). Averages are plotted for all reserves and
for temperate and tropical reserves separately. (d) Individual reserve re-
sponses by environment. N: number of reserves (temperate, tropical) for which
each biological variable was measured
Lester et al.: Biological effects within marine reserves
brates tended to show higher but non-significant
responses for organism biomass and density (t-tests,
density: p = 0.119, biomass: p = 0.069). Invertebrate
densities showed negative responses in some reserves
in addition to strong positive effects in many others,
which may be the result of indirect effects and/or
trophic dynamics (e.g. Shears & Babcock 2003, Micheli
et al. 2005).
To investigate the combined influence of environ-
ment and taxonomic group on the effects of reserve
protection for density and organism size (biomass and
richness lacked adequate sample sizes), we included
environment (tropical versus temperate), taxonomic
group (algae, invertebrates, and fishes for density; in-
vertebrates and fishes for organism size), and the inter-
action term as predictor variables in a 2-way ANOVA.
The overall model for density was significant (p =
0.004), as were the individual effects of environment
and taxonomic group (effect tests; p = 0.005 and 0.003,
respectively). This result reflects 2 trends: (1) within
each taxonomic group, there was a tendency for den-
sity responses to be higher in temperate versus tropical
reserves (t-tests, algae: p = 0.089, n = 22; fishes: p =
0.191, n = 81; invertebrates: p = 0.063, n = 71); and (2) ir-
respective of latitude, the density response was signifi-
cantly different across taxonomic groups (ANOVA, p =
0.017), with invertebrates and fishes showing higher
positive mean responses than algae. In contrast, the en-
vironment taxonomic group model was not significant
for organism size (p = 0.999), suggesting that increases
in individual size are consistent for fishes and inverte-
brates across reserves in different geographic locations
compared to the variation in responses that we docu-
mented for density. Lastly, there was no effect of lati-
tude on biomass and richness of fish (t-tests, biomass:
p = 0.332; richness: p = 0.272), which parallels our re-
sults for overall reserve response ratios.
Beyond the differences we document for these broad
taxonomic groups, individual species or groups of spe-
cies are likely to respond differently to reserve protection
based on a range of factors. For example, reserves are
more likely to lead to large positive effects for species
that are fished, intentionally or incidentally, or that are
otherwise harmed by activities occurring in unprotected
waters (Mosqueira et al. 2000, Cote et al. 2001, Micheli et
al. 2004). Other characteristics that have been shown to
mediate a reserve effect include trophic level (Micheli et
al. 2004) and body size (Mosqueira et al. 2000). These
more detailed analyses of species characteristics have
only been conducted for fish, revealing a need for simi-
lar investigations for algae and invertebrates. However,
it should be noted that species characteristics tend to ex-
plain a relatively low percentage of the variance in re-
serve responses (e.g. Micheli et al. 2004).
To assess the influence of algal and invertebrate
characteristics, we conducted algae-only and inverte-
brate-only analyses using data extracted at the finest
taxonomic resolution available. For algal functional
groups, no group showed a statistically significant
response to reserve protection (Table S3, available at
and functional group was not a significant predictor of
algal response (Table 2). The most dramatic response,
albeit non-significant, was a ~500% average increase
in leathery macrophytes (Table S3). The lack of signif-
icant responses is likely due in part to the relatively
small sample sizes for algae, although it is also possible
that algae respond idiosyncratically to reserve protec-
tion. Lastly, algae are more commonly measured in
temperate reserves, particularly with adequate taxo-
nomic resolution to allow for functional group classifi-
cation. The only functional group for which there were
data from both tropical and temperate reserves was
corticated foliose algae, which increased in temperate
Table 2. ANOVA for algal functional groups and invertebrate characteristics predicting mean reserve response (using log re-
sponse ratios). Pair-wise comparisons of target status categories for density indicated that ‘high’ and ‘not targeted’ are signifi-
cantly different, but neither of those differ from ‘low’ (Tukey’s HSD test). None of the trophic level categories for density are sig-
nificantly different in pair-wise comparisons (Tukey’s HSD test)
Characteristic Categories Biomass Density Organism size
pN pN pN
Algal functional groups Crustose algae; filamentous algae; 0.763 41
articulated calcareous algae; corticated
foliose algae; corticated macrophytes;
leathery macrophytes
Adult mobility Sessile; limited mobility; mobile 0.663 16 0.578 96 0.372 39
Target status High; low; not targeted 0.190 17 0.008 86 0.495 36
Trophic level Herbivore; primary producer/filter 0.066 23 0.022 107 0.414 42
feeder; filter feeder; detritivore; omnivore;
Larval dispersal potential Little/none; short distance; longer distance 0.351 63 0.139 36
Mar Ecol Prog Ser 384: 3346, 2009
reserves (49% increase, n = 5 reserves) and decreased
in tropical reserves (15% decrease, n = 3 reserves),
although again these changes were not statistically
In the invertebrate-only analyses, mollusks and
arthropods showed significant increases as a result of
reserve protection (Table S4, available at; for density
and size for mollusks and for biomass, density, and size
for arthropods). Examining finer taxonomic groupings,
gastropods showed a significant increase in density
and size, crabs showed an increase in density, and lob-
sters increased significantly in biomass, density, and
size (Table S4). The dramatic increases documented
for species like lobster are not surprising given that
they are often heavily exploited and have relatively
high population growth rates, allowing them to
respond quickly to protection. In contrast, slow grow-
ing taxa such as hard corals did not show significant
responses. Some taxonomic groupings, such as cepha-
lopods and soft corals, had very small sample sizes and
thus we could not adequately evaluate the effect of
reserve protection for these groups.
When examining the effect of invertebrate charac-
teristics on reserve response, we found that target sta-
tus and trophic level were both significant predictors of
density responses (Table 2). As expected, highly tar-
geted species showed the largest response, and these
responses were relatively similar across tropical and
temperate reserves (Fig. 8). For trophic level, pre-
datory invertivores showed the largest increases
(Table S2). These results are consistent with those for
fish, where higher trophic levels tend to show greater
responses to protection, likely because higher preda-
tors tend to be targeted by fisheries. Importantly, while
these characteristics were significant predictors of
density responses, they explain a relatively small per-
centage of the variance (ANOVA, R
= 0.111 and 0.120
for target status and trophic level, respectively). Adult
mobility and larval dispersal potential were not related
to reserve responses for any of the biological measures
(Table 2), although some of the movement and disper-
sal categories showed a significant effect of protection
(Table S2). These significant responses are likely due
to covarying characteristics that do influence a reserve
response. For example, many of the species in the data
set with longer distance dispersal are lobsters and
crabs, which are heavily fished species with high pop-
ulation growth rates. This makes them ideal candi-
dates for reserve protection irrespective of their disper-
sal characteristics.
The algal and invertebrate characteristics we inves-
tigated either were unrelated to a reserve response or
explained only a relatively small portion of the vari-
ance in responses (Table 2), with similar results found
previously for fishes (e.g. Micheli et al. 2004). There-
fore, it is possible that variation in reserve responses
for these species-level traits is driven by characteristics
of the reserve (e.g. age, size) and the context of where
the reserve is located, including intensity of fishing
before reserve establishment and outside of the re-
serve, enforcement, and the management regime out-
side of the reserve. It is also possible that the species-
level traits we were able to examine in this synthesis
do not adequately capture the ecological or life-history
traits that truly influence how these species respond to
reserves. Both reserve characteristics and species traits
are unfortunately difficult to assess but merit addi-
tional investigation.
Using a comprehensive global synthesis of ecologi-
cal effects within no-take marine reserves, we demon-
strate that reserve protection results in significant
average increases in density, biomass, organism size,
and species richness of the communities within reserve
boundaries. However, it is important to note that
Invertebrate target status
High Low Not
Change in density (%)
Grand mean
Temperate reserves
Tropical reserves
Fig. 8. Average (gray bars) percent change in density calculated
from invertebrate-only mean reserve responses, by target sta-
tus. (d, s) Individual temperate and tropical reserve responses,
respectively. There is a significant relationship for target status
predicting reserve response (ANOVA, p = 0.008, n = 86). Pair-
wise comparisons of target status categories indicated that
‘high’ and ‘not targeted’ are significantly different, but
neither of those differ from ‘low’ (Tukey’s HSD test, p 0.05).
See Table S4 (available at
m384p033_app.pdf) for additional information
Lester et al.: Biological effects within marine reserves
reserves will not result in significant increases in all
species, as demonstrated by the average decrease in
algal density in tropical systems and the numerous
negative invertebrate density data points. Addition-
ally, our synthetic analysis demonstrates that these
biological increases remain consistent as more scien-
tific information about the impacts of marine reserves
becomes available. Despite a perception that reserves
are more likely to be effective in tropical regions, our
results suggest that reserves result in positive effects at
all latitudes and regions. Thus, reserves are likely to
serve as globally important conservation and manage-
ment tools when management goals include at least
one of the biological responses reviewed in the present
Our analysis also revealed numerous critical infor-
mation gaps. First, we note a general lack of peer-
reviewed reserve publications from certain regions of
the world. Reserves exist in these locations, but it is dif-
ficult to assess whether implementation and enforce-
ment are effective or whether these reserves can only
be considered ‘paper reserves.’ Coordinated efforts to
promote better dissemination of marine reserve sci-
ence will greatly increase our understanding of the
benefits and limitations of no-take marine reserves as
an effective means of conservation and management.
Similarly, the vast majority of reserves in our data set
protect nearshore rocky or coral reef habitat, indicat-
ing a lack of marine reserve studies (and potentially
marine reserves) in certain habitat types (e.g. soft sedi-
ment). This is particularly important for the interpreta-
tion of our comparison of tropical versus temperate
reserve effects while we have strong evidence that
tropical and temperate reserves are similarly effective
for reef ecosystems, we do not know whether this
result holds for less structured habitat types.
For reserves that have been studied, there is a need
for increasingly rigorous data collection. (1) Studies in
which the reserve area is studied prior to and after
implementation both outside and inside reserve
boundaries are relatively rare. Such studies are critical
because they effectively control for natural ecosystem
dynamics and ecological variability on a regional scale
and can help detect spurious reserve effects (Fig. 4).
(2) Studies examining the same suite of species at
reserves of different sizes within a region will be
essential for better understanding how reserve effects
scale with reserve size. Recent reviews have not com-
pared data explicitly designed to investigate the effect
of reserve area, and thus it is not surprising that they
have found reserve effects to be constant across a
range of reserve sizes (but see Claudet et al. 2008).
(3) There is a need for accurate data and methods for
quantifying the intensity of fishing and other exploitive
activities outside of the reserve, management and reg-
ulations outside of the reserve, and intensity of fishing
inside the reserve prior to establishment, all of which
may affect the response documented within a
particular reserve, and which could thus help to
explain the large amount of variation in reserve res-
ponses globally. The strong positive biological res-
ponses that we have documented around the world
indicate that we can move past questions of reserve
impacts across latitudes and taxonomic groups, and
shift the focus to increasingly complex questions about
the effects of marine reserves, both within and beyond
their borders.
Acknowledgements. This work was supported by the Partner-
ship for Interdisciplinary Studies of Coastal Oceans (PISCO),
funded by the David and Lucile Packard Foundation and the
Gordon and Betty Moore Foundation (contribution no. 335).
This analysis contributed to The Science of Marine Reserves,
an educational booklet funded by the David and Lucile
Packard Foundation. S.E.L. was also supported by a NOAA
Dr. Nancy Foster Scholarship. We thank S. Palumbi and
P. Guarderas for discussions about the data set, W. McClin-
tock for the global marine reserve map, A. Rassweiler for help
with some analyses, and several anonymous reviewers for
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Submitted: November 20, 2008; Accepted: March 21, 2009
Proofs received from author(s): May 18, 2009
... Global evidence indicates that MPAs that are well-designed and enforced for fisher compliance do rebuild populations of exploited species (Edgar et al., 2014) (Appendix S3). A well-known syntheses of 124 fully protected MPAs from 29 different countries found that fish, invertebrates and seaweeds combined had, on average, 4.5 times more biomass, 66% greater density, 28% larger sizes and 21% higher species diversity inside MPAs than in fished areas (Lester et al., 2009). That synthesis was published 13 years ago. ...
... The expected benefits of MPAs to fisheries build on three key concepts: (1) Bigger fish are disproportionately more fecund than smaller fish (Barneche et al., 2018;Dick et al., 2017); (2) fisheries remove the largest individuals, but MPAs restore higher densities of larger and more fecund individuals Willis et al., 2003), and overall greater abundances (Lester et al., 2009), which (3) leads to the spillover, or export, of larvae and adults from protected into fished areas (Barceló et al., 2021;Di Lorenzo et al., 2020). Similar concepts apply to commercially harvested invertebrates, which also grow larger and more fecund inside MPAs (Micheli et al., 2012;Pelc et al., 2009). ...
... MPAs (Bosch et al., 2022;Keller et al., 2019;Lester et al., 2009;Willis et al., 2003), and their increased larval production (Thompson et al., 2017) boosts recruitment into fished areas (Le Port et al., 2017). ...
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We, the Haíłzaqv, Kitasoo Xai'xais, Nuxalk and Wuikinuxv First Nations, are the traditional stewards of our territories in the Central Coast of British Columbia, Canada. Our traditional laws obligate us to manage and protect our territories for current and future generations. Spatial management is inherent to our cultures through the Hereditary Chief governance system, in which specific people within a lineage inherit the rights and responsibilities for stewarding specific areas. Since the 19th century, we have been experiencing cultural disruptions caused by settler colonialism, which are now worsened by the declines of marine species vital to our cultures. These declines reflect fishery impacts exacerbated by climate change. Western fisheries management focuses on maximum sustained yields (MSY), ignoring body size declines that disrupt food webs and diminish population productivity for vertebrate and invertebrate taxa, thereby eroding resilience to climate change. The worldview encompassed by the MSY framework—take the most that you can without compromising future exploitation while assuming no environmental change—is the antithesis of ours—take only what you need and leave lots for the ecosystem. Furthermore, standard stock assessments do not account for uncertainties inherent to climate change effects on distributions and productivity, and many by‐catch species are unassessed. Consistent with our traditional knowledge, scientific evidence indicates that marine protected areas (MPAs), coupled with other measures to reduce fishing mortality, can restore exploited species, safeguard biodiversity and contribute to fisheries sustainability. In the 2000s, we paired Indigenous knowledge and Western science to develop marine spatial plans. These plans are foundational in our contribution to the ongoing development of the Marine Protected Area Network for Canada's Northern Shelf Bioregion (MPAN‐NSB), for which we are co‐governance partners with 14 other First Nations and the governments of Canada and British Columbia. Our proposed spatial protections for the MPAN‐NSB encompass areas important to many exploited taxa and to corals, sponges, eelgrass beds and other carbon stores. Their implementation would fill conservation gaps which have persisted under current fishery management. Given our history of spatial management through the Hereditary Chief governance system, the MPAN‐NSB is a culturally appropriate way forward for marine conservation in our territories. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.
... The use of marine protected areas (MPAs) as a tool to protect habitats and species is increasing globally (Edgar and Stuart-Smith 2014;Lubchenco and Grorud-Colvert 2015;Sala and Giakoumi 2018). ...
... MPAs have been shown to recover benthic ecosystems (Sheehan et al. 2013a), including increased species' biomass, catch per unit effort, diversity, density and community stability (Lester et al. 2009;Sciberras et al. 2013;Sheehan et al. 2013b;Mellin et al. 2016) and predicted benefits for carbon sequestration and climate change mitigation (Sala et al. 2021). MPAs are widely advocated by the Convention of Biological Diversity (CBD), the International Union for the Conservation of Nature (IUCN) and European Union (EU), with a current target set by the Global Ocean Alliance to protect 30% of marine areas by 2030 (O'Leary et al. 2016;Brander et al. 2020;Rees et al. 2020;Waldron et al. 2020). ...
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Globally, nations are designating marine protected areas to recover and protect habitats and species. With targets to protect 30% of marine areas by 2030, the effectiveness of MPAs to protect designated space is important. In Lyme Bay (south‐west UK), two co‐located MPAs have each adopted different management styles to exclude mobile demersal fishing: a Special Area of Conservation (SAC) protecting the known extent of sensitive reef habitat and an area including a mosaic of reef and sedimentary habitats where the whole site is protected from mobile demersal fishing under a statutory instrument (SI). Underwater videography, both towed (individuals m−2) and baited (MaxN), was used to enumerate change over time of reef species (number of taxa, total abundance, functional richness and functional redundancy) in the MPAs and nearby control areas (2008–2019). Total abundance and functional redundancy of sessile taxa and functional richness of mobile taxa increased, while the number of sessile or mobile taxa, functional richness of sessile taxa, total abundance of mobile taxa or functional redundancy of mobile taxa did not differ from nearby control sites. Over time, both management styles did result in increases in sessile and sedentary taxa diversity relative to open controls, with increases in total abundance of 15% and 95% in the “feature‐based” and whole‐site MPAs, respectively, alongside increases in the number of sessile taxa of 44% over time in the “feature‐based” MPA. However, the mobile taxa in the whole‐site MPA showed levels of functional redundancy 7% higher than the “feature‐based” MPA, indicative of a higher community resilience inside the whole‐site MPA to perturbations, such as storms or biological invasions. Increases seen in the diversity of sessile taxa were expected only in areas where mobile demersal fishing was excluded (~46.8% of its areas). Therefore, if the whole “feature‐based” MPA was consistently protected, we expected to see similar levels of increase in the functional extent of reef. While the “feature‐based” MPA showed similar results over time to that of the “whole site,” the “whole site” showed higher levels of diversity, both taxonomical and functional.
... MPAs are generally considered effective in protecting species with limited movements 33,34 , but recent evidence pointed out their potential to conserve mobile and long-lived predators, including elasmobranchs 25,35 . Several very large FPAs have been established worldwide and are being promoted as a tool for conservation and recovery of pelagic species (including elasmobranchs) 36,37 . The recent designation of large FPAs has greatly helped in achieving global protection targets 38 . ...
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Elasmobranchs are heavily impacted by fishing. Catch statistics are grossly underestimated due to missing data from various fishery sectors such as smallscale fisheries. Marine Protected Areas are proposed as a tool to protect elasmobranchs and counter their ongoing depletion. We assess elasmobranchs caught in 1,256 fishing operations with fixed nets carried out in partially protected areas within Marine Protected Areas and unprotected areas beyond Marine Protected Areas borders at 11 locations in 6 Mediterranean countries. Twenty-four elasmobranch species were recorded, more than onethird belonging to the IUCN threatened categories (Vulnerable, Endangered, or Critically Endangered). Catches per unit of effort of threatened and data deficient species were higher (with more immature individuals being caught) in partially protected areas than in unprotected areas. Our study suggests that despite partially protected areas having the potential to deliver ecological benefits for threatened elasmobranchs, poor small-scale fisheries management inside Marine Protected Areas could hinder them from achieving this important conservation objective.
... Among them, Marine Protected Areas (MPAs) are a primary management tool for mitigating threats to marine ecosystems and increasing their resilience to climate change effects [Edgar et al., 2014;Lester et al., 2009;O'Leary et al., 2016;Roberts et al., 2017;Davies et al., 2017, e.g.] Figure 1.3). ...
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Bottom-up forces control a large fraction of marine ecosystem variability. In the Southern Ocean, intense contrasts in the distribution of pelagic ecosystems are driven by the iron limitation of biological productivity and the vigorous Antarctic Circumpolar Current. Massive phytoplankton blooms stemming from islands support large trophic chains. By comparison, the impact of deep nutrient sources on the pelagic production appears negligible. Conservation efforts in the Antarctic Circumpolar Current are in line with this description, with Marine Protected Areas only occurring around islands. By combining multi-satellite data, in-situ observations, animal telemetry data and model outputs, this thesis revaluates the ecological role of deep nutrient sources. Lagrangian analyses of altimetry-derived velocity fields link vast phytoplankton blooms to hydrothermal vents or seamounts. The studies contained in this thesis demonstrate that bottom-up forcings driven by deep nutrient sources shape the pelagic seascape at basin scale (O(103 km)) from primary producers up to megafauna species. These findings underline the ecological importance of the open Southern Ocean waters and advocate for a connected vision of future conservation actions along the Antarctic Circumpolar Current. The analyses of bottom-up forcings are consequentially considered within the CCAMLR’s effort for developing a representative system of Marine Protected Areas and within the ongoing extension project of the French Saint Paul and Amsterdam islands’ Marine Protected Areas.
... Well-managed MPAs (particularly no-take MPAs) deliver effective conservation within their boundaries in many regions (e.g., Fenberg et al, 2012;Lester et al., 2009;Giakoumi et al., 2017;Topor et al., 2019), strengthening calls and advocacy for MPAs to be the principal method for conserving marine biodiversity (O'Leary et al., 2016). Yet, others have highlighted their shortcomings, with MPAs receiving criticism for frequent poor placement, design or management, and risks to vulnerable coastal populations reliant on the oceans for food and livelihoods (Agardy et al., 2011;Rife et al., 2013;Bennett and Dearden, 2014;Sowman & Sunde, 2018;Álvarez-Fernández et al., 2020). ...
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In 2010, the Parties to the Convention on Biological Diversity (CBD) adopted the Aichi Biodiversity Target 11, calling for conserving 10% of the ocean through marine protected areas (MPAs) and “other effective area-based conservation measures” (OECMs), explicitly recognizing that other types of spatial conservation measures beyond areas designated as MPAs may also achieve biodiversity gains. Eight years later, CBD Parties adopted a definition and criteria for OECMs, and by early 2022, only a few OECMs had been reported. The OECM definition clearly requires that the measures be area-based and likely to contribute to conservation. However, conservation need not be their primary objective. Guidance on the extent and limits of what these “area measures” might include is needed. Clarity would assist countries in delivering on the CBD’s Post-2020 Global Biodiversity Framework, with decadal goals incorporating an area-based conservation target, in which OECMs will play a crucial role. To achieve greater recognition of OECMs, countries require sector-specific guidance to guide recognition, listing, and ongoing implementation of OECMs. Here, we evaluate how well area-based fisheries management measures meet the OECM criteria as well as sustainable use principles, broader ecosystem management objectives, and more general biodiversity conservation goals. We systematically review case studies across a broad range of spatial management approaches to provide evidence of correspondence with the OECM criteria, arguing that many with primary objectives related to fisheries sustainability provide co-benefits for biodiversity, and hence biodiversity conservation and sustainable development. This review highlights how fisheries measures can help achieve a number of Sustainable Development Goals alongside the global targets for biodiversity of CBD.
... Overall, no-take reserves have a positive effect on biomass and species richness ). However, Lester et al. (2009) found that for algae and invertebrates, this is not always the case. This makes sense, since most of the MPAs were implemented to sustain fisheries . ...
To give sound management advice, the connectivity in coastal areas must be thoroughly understood. The red thread throughout this PhD is analysing the uncertainty of the SYMPHONIE2015 model and its effect on larval dispersal simulations. In the first chapter, the robustness of the model to assumption violation was tested. This was done by calculating six relative and absolute statistical indicators during and outside of wind, wave and stratification events. The results showed that the model’s performance is not affected by these events. In the second chapter, the instant error was calculated. Then, the cumulative error distributions were compared to each other in space and time. In time, the intraseasonal differences in error distributions were smaller than the interseasonal ones. In space, eight groups of error distributions could be formed. No link was found between the model’s performance and stratification, water depth, resolution and bathymetry slope. However, a strong correlation between the current speed and the error distributions was found. In chapter three, the instant error was added as noise to the Lagrangian dispersal simulations and compared to the original run to assess the effect of the models’ error on connectivity. The median difference in transfer rate between the runs with and without noise around zero. However, the relative difference in transfer rate can vary from -100% to 100%. Knowing the uncertainties in dispersal simulations can aid in using them for management advice.
... While MPAs that are well-managed can help to mitigate non-climate-related threats, such as fishing, habitat loss, and pollution (Jackson et al. 2001;Lester et al. 2009;Edgar et al. 2014;Bruno et al. 2018), impacts from climate-induced ocean warming are likely to continue to disrupt ecosystems within MPAs (Bruno et al. 2018). Historically, MPAs have been developed on an individual basis to address local impacts and stressors with more recent implementation of MPA networks to achieve larger scale conservation objectives and protecting broader scale ecological communities and habitats. ...
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Climate change and related ocean warming have affected marine ecological and socioeconomic systems worldwide. Therefore, it is critically important to assess the performance of conservation mechanisms, particularly marine protected areas (MPAs) to moderate the risks of climate-related impacts. In this study, sea surface temperature trends of Australian Commonwealth MPAs are assessed against climate change management criteria, as defined in Adapting to Climate Change: Guidance for Protected Area Managers and Planners. Monthly sea surface temperature trends between 1993 and 2017 were statistically assessed using the Mann–Kendall trend test and management plans were subject to a thematic analysis. Temperature trends showed variable SST changes among the regions, with the northern reserves all showing statistically significant increases in temperature, and the Southwest Network having the least number of reserves with statistically significant increases in temperature. The thematic analysis shows that management plans address approximately half of the climate change adaptation criteria. Several management strategies, such as dynamic MPAs, replication, and translocations, are currently absent and have been suggested as necessary tools in supporting the climate readiness of Australian MPAs. This study is significant because it helps to identify and synthesize regions most vulnerable to the impacts of ocean warming and provides management suggestions make MPAs “climate ready.”
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Management of fisheries by preventing commercial, whilst allowing recreational-only fishing in some areas, is intended to increase stocks so that sustainable recreational fishing is conserved or enhanced. This study examined whether the relative abundances and length and age characteristics of five harvested species of fish differed between recreational-only fished (ROF) estuaries, and those open to both recreational and commercial fishing (non-ROF) in southeastern Australia. Specific predictions based on absolute and ranked values of a range of parameters were made so that conclusions could be reached about the effects of management. Fish were sampled using multimesh gillnets in a standard and stratified manner across two ROF and two non-ROF estuaries over three years, six to eight years post ROF implementation. Abundances of each species fluctuated among individual estuaries and sampling times with no indication of greater abundances in ROF estuaries. For four species (Sillago ciliata, Mugil cephalus, Acanthopagrus spp. and Girella tricuspidata), the mean lengths and the proportions of individuals of legal length, were mostly greater in the ROF compared to the non-ROF estuaries. However, for Platycephalus fuscus there were no discernible patterns. Three species (P. fuscus, S. ciliata and Acanthopagrus spp.) had a significantly greater proportion of older fish in the ROF estuaries, but for M. cephalus and G. tricuspidata this was only evident in one ROF estuary. It is hypothesised that the cessation of commercial fishing and subsequent reduction in fishing pressure in the ROF estuaries allowed a greater proportion of individuals of each species to survive to become larger and older. This study provides correlative evidence that ROF estuaries can protect some harvested species at the local scale of estuary. Examination of lengths and ages of fish, rather than simply their abundances, was necessary to identify the effects of removing commercial fishing. Further research is required to determine the potential broader-scale and long-term sustainability benefits on species as well as any spill-over effects on other organisms and estuarine ecosystems.
The dispersal of larvae by ocean currents is likely to represent an increasingly important driver of marine population dynamics across fragmented habitats. A boost in availability of larval dispersal data from biophysical simulations has therefore led to routine calculations of population connectivity metrics that are used for area-based management decision support, including the placement of Marine Protected Areas (MPAs). However, connectivity-based decision support for area-based management is often complex, highly uncertain, and the associated conservation impact rarely if ever evaluated. In combination, these challenges risk stakeholder engagement, compliance, and overall management effectiveness. Here we use a case study representing multiple key fishery species on coral reefs in Indonesia to demonstrate that consideration of larval dispersal for MPA placement decision support could be critical to recover both fish populations and fisheries from depletion, thereby mitigating potentially severe impacts on coastal communities. Importantly, we further show that MPA placement decisions can be effective even if based on comparatively simple and empirically measurable dispersal characteristics. Maximizing larval export, expressed as the contribution of larvae from MPA candidate sites to total larval settlement in surrounding areas, for example, was found to be a broadly beneficial MPA placement prioritization approach. Across investigated fish families with diverse life histories, this strategy resulted in MPA network designs that increased catches by a factor of 1.3 ± 0.3 (mean ± SD) and total fish biomass by a factor of 3.2 ± 0.3 (9.7 ± 1.2 in no-fishing areas and 1.4 ± 0.3 in fished areas) compared to conditions without effectively managed or protected areas. Our findings are relevant for both the implementation and impact evaluation of global marine conservation policies, specifically in tropical biodiversity hotspots, such as Indonesia, where coral reefs are often overfished and increasingly threatened but local communities highly dependent on sustainable fisheries.
Marine reserves are essential spatial conservation tools that have been shown to work alongside fishery management strategies to provide benefits to ecosystems and communities. Reserves often incentivize local tourism, which can provide the impetus for reserve creation but may have negative impacts on the ecosystem. The COVID‐19 pandemic paused global travel and provided an unprecedented opportunity to compare short‐term changes in exploited populations, during the reprieve from visitation provided by this ‘anthropause’, with the results of long‐term conservation management. Repeated surveys of Caribbean spiny lobster and Nassau grouper were conducted at popular dive and snorkel locations within a Bahamian no‐take reserve and surrounding areas during peak visitation prior to travel restrictions and immediately after restrictions were lifted. Repeated survey results were referenced against surveys over a broader area, including another Bahamian Bank, to examine the consistency of effects and how the ease of access for fishers impacted abundance. In the reserve, lobsters were encountered in significantly greater abundances, and significantly greater sizes of both lobster and grouper were observed in repeated surveys. Significantly more grouper were encountered during the repeated survey within the reserve after travel restrictions, but lobster abundances did not change significantly. Over a broader scale, lobster abundance was significantly greater further from population centres. Observed lobster abundance was affected by habitat and inferred fishing pressure, whereas observed grouper abundance was affected by survey depth, effort, and habitat. Marine reserves had clear benefits for both species and likely facilitated an increase in grouper abundance during the anthropause. Lobsters are a sustainably managed stock in The Bahamas, whereas grouper are a threatened species that appear to have benefited from an unplanned fishery restriction. Well‐managed marine reserves enhance populations long term and can have additive effects with fisheries management over short timescales.
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We suggest that relatively few species attributes are of overriding importance to the structure of benthic marine algal communities and that these are often shared among taxonomically distant species. Data from the western North Atlantic, eastern North Pacific and Caribbean suggest that patterns in algal biomass, diversity and dominance are strikingly convergent when examined at a functional group level relative to the productivity and herbivore-induced disturbance potentials of the environment. We present a simple graphical model that provides a way to predict algal community composition based on these two environmental axes. This predictability stems from algal functional groups having characteristic rates of mass-specific productivity, thallus longevity and canopy height that cause them to ''behave'' in similar ways. Further, herbivore-induced disturbances have functionally similar impacts on most morphologically and anatomically similar algae regardless of their taxonomic or geographic affinities. Strategies identified for marine algae parallel those of a terrestrial scheme with the addition of disturbance-tolerant plants that characteristically coexist with and even thrive under high levels of disturbance. Algal-dominated communities, when examined at the functional group level, appear to be much more temporally stable and predictable than when examined at the species level.
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Marine Protected Areas (MPAs) are a common tool for conserving and managing marine and coastal ecosystems. MPAs encompass a range of protection levels, from fully protected no-take reserves to restriction of only particular activities, gear types, user groups, target species, or extraction periods. There is a growing body of scientific evidence supporting the ecological benefits of full reserve protection, but it is more difficult to generalize about the effects of other types of MPAs, in part because they include a range of actual protection levels. However, it is critical to determine whether partial protection and no-take reserves provide similar ecological benefits given potential economic costs of lost fishing grounds in no-take areas, common sociopolitical opposition to full protection, and promotion of partially protected areas as a compromise solution in ocean zoning disputes. Here we synthesize all empirical studies comparing biological measures (biomass, density, species richness, and size of organisms) in no-take marine reserves and adjacent partially protected and unprotected areas across a range of geographic locations worldwide. We demonstrate that while partially protected areas may confer some benefits over open access areas, no-take reserves generally show greater benefits and yield significantly higher densities of organisms within their boundaries relative to partially protected sites nearby.
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Can rates of biomass recovery of fished species be inferred reliably from once-only spatial comparisons of no-take marine reserves of different ages and fished areas? We used underwater visual census at 15 no-take marine reserves in the Philippines to both infer and measure such rates. We made a single estimate of the biomass of large predatory fishes (Serranidae, Lutjanidae, Lethrinidae) targeted heavily by fisheries in each of 13 well protected no-take reserves (age range 0.5 to 13 yr), and in nearby nonreserve (fished) sites. We also measured rates of biomass buildup of these fish regularly for 18 yr (1983 to 2001) in 2 no-take reserves (Sumilon, Apo) and nonreserve sites. The duration of protection required to detect significantly higher reserve biomass was similar, but lower for temporal monitoring (3 to 4 yr) than for spatial comparisons (6 yr). The reserve:nonreserve biomass ratios at maximum duration of reserve protection were similar for inferred (9.0) and measured (6.3 to 9.8) estimates. Thus, results of long-term monitoring of 2 reserves may have regional generality. The inferred rate of change of a reserve effect index (log 10 [Reserve biomass + 1 / Nonreserve biomass + 11) with duration of protection did not differ significantly from the measured rate at Sumilon, but was higher than that measured at Apo. A habitat complexity index did not affect estimates of 'reserve effects' significantly in this study, and reserve protection was generally effective. Thus, using similar methods of reserve protection and census on the same target group in similar areas, one can make useful inferences about rates of recovery in no-take marine reserves.
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Between 1978 and 1996 benthic communities in the Leigh Marine Reserve shifted from being dominated by sea urchins to being dominated by macroalgae. This was a result of a trophic cascade thought to be an indirect effect of increased predator abundance. We assessed further changes in communities from 1996 to 2000, differences in benthic communities between reserve and adjacent unprotected sites, and the stability of these patterns from 1999 to 2001. Since 1996, densities of sea urchins Evechinus chloroticus have continued to decline in shallow areas of the reserve (< 8 m), and all sites classified as urchin barrens in 1978. are now dominated by large brown algae. Comparisons between reserve and non-reserve sites revealed differences consistent with a trophic cascade at reserve sites. The greatest differences in algal communities between reserve and non-reserve sites occurred at depths where E. chloroticus was most abundant (4 to 6 m). Reserve sites had lower urchin densities and reduced extent of urchin barrens habitat with higher biomass of the 2 dominant algal species (Ecklonia radiata and Caipophyllum maschalocarpum). At reserve sites densities of exposed E. chloroticus (openly grazing the substratum) declined so that urchin barrens were completely absent by 2001. Lower density of the limpet Cellana stellifera and higher densities of the turbinid gastropod Cookia sulcata at reserve sites are thought to be responses to changes in habitat structure, representing additional indirect effects of increased predators. The overall difference in community types between reserve and non-reserve sites remained stab le between 1999 and 2001. Localised urchin mortality events due to an unknown agent were recorded at some sites adjacent to the marine reserve. Only at 1 of these sites did exposed urchins decline below the critical density of 1 m(-2), which resulted in the total replacement of urchin barrens with macroalgae-dominated habitats. At other sites urchin barrens have remained stable. Declines in the limpet C. stellifera occurred across all sites between 1999 and 2001 and may be indirectly associated with urchin declines. Long-term changes in benthic communities in the Leigh reserve and the stability of differences between reserve and non-reserve sites over time are consistent with gradual declines in urchin densities due to increased predation on urchins, thus providing further evidence for a trophic cascade in this system. The rapid declines in urchin numbers at some unprotected sites, however, demonstrate how short-term disturbances, such as disease, may result in shifts in community types over much shorter time frames.
The indigenous peoples of Transkei, South Africa, remove shellfish from the shore to supplement their diet. Paired exploited and protected rocky shores were compared in terms of community structure and of the size structures of component species. Relative abundance of algae and sessile, inedible invertebrates is greater, and modal and mean sizes of exploited species are smaller at exploited sites than at protected sites. Disturbance through selective predation increases species richness, in line with the "intermediate disturbance hypothesis", and also leads to community convergence towards a common state. The recovery potential of these systems is high and the resource could best be managed on a "rotational cropping" basis. /// Туземцы Транскеи (Южн. Африка) собирают раковинных моллюсков на побережье для пополнения своего рациона. Эксплоатируемые и охраняемые участки скалистого берега сравнивали попарно по показателям структуры сообществ и размерной структуры участвующих в них видов. Относительное обилие водорослей и прикрепленных несьедобных боеспозвоночных выше, а модальные и средние размеры зксплоатируемых видов меньше на промысловых участках, по сравнению с охраняемыми. Нарушения вследствие селективного хищничества повышают видовое богатство в соответствии с гипотезой "промежутосного нарушения", а также приводят к конвергенции сообществ, находящихся в сходном состоянии. Потенциальные возможности восстановления зтих систем высоки, и ресурсы могут лучше всего регулироваться на базе "потационного сбора урожая".
The ecological role played by man as a top predator in a rocky intertidal environment of central Chile was studied. Human exclusion from a rocky intertidal stretch of coast (non-harvested area) at Punta El Lacho, for nearly two years, resulted in a substantial density increase of the economically important high trophic level predator muricid Concholepas concholepas. This was followed by a dramatic decline in the cover of the competitive dominant intertidal mussel Perumytilus purpuratus. According to current ecological theory the removal of the competitively superior primary space dominant species led to a pattern of increasing species diversity. We conclude that in the absence of human interference C. concholepas plays the role of a key species in central Chile rocky intertidal environments. We suggest that the interpretation of the structure and dynamics of intertidal landscapes should include the key role played by man. Comparison of monitoring programs between intertidal areas with and without human interference will prove critical to our understanding of such environments. /// Исследовали экологическую роль человека как высшего хишника в скалистой ли-торальной зоне центрального Чили. Исключение деятельности человека с опреде-ленного отрезка береговой линии (непромысловая территория) в Пунта эль Лахо примерно на 2 года привело к существенному повьшению плотности популяции экономически важного вида мирицид Concholepas concholepas - высшего хищинка. Это сопроваждалось драматическим снижением численности конкурирующего доми-нанта моллюска Perumytilus purpuratus. Согласно современной экологической теории удаление более конкурентоспособного первичного доминирующего вида приводит к повышению видового разнообразия. Мх делаем вывод, что при отсут-ствии антропогенного пресса C. concholepas итрает роль ключевого вида в со-обществах склистой литорали центрального Чили. Мы полагаем, что интерпре-тация структуры и динамики литоральных ландшафтов должна была бы включать и ключевую роль человеческой деятельности. Сравнение программ монторинта разных литоральных зон с антропогенным прессом и без него должно быть кри-тически пересмотрено для нашего понимания таких сообществ.
Marine reserves affect areas outside reserve boundaries via the displacement of fishing effort and the export of production. Here we focus on how these key factors interact to influence the results seen once reserves are created. For a settlement-limited fishery, export of increased production from within reserves can offset the effects of dis- placed fishing effort. We develop simple mathematical models that indicate net fisheries benefits can accrue at closures up to and perhaps beyond 50% of total stock area through the export of production, given documented average increases in biomass within reserves. However, reserve monitoring programs face problems identifying independent control sites because the spatial extent of export is unknown. Efforts to monitor reserve impacts on recruitment are further complicated by the fact that large reserve closures are likely nec- essary before significant changes in recruitment can be detected above normal interannual fluctuations. Resolving these limitations requires comprehensive monitoring data before reserves are implemented. Fortunately, studies of reserves that used Before-After, Control- Impact (BACI) experimental designs show that control and reserve sites were equivalent prior to protection, and that control sites improved after reserves were in place. Conse- quently, any bias in our current perception of reserve impacts likely underestimates their effect. Key words: BACI experimental designs of marine reserves; export of fish production; fishing effort; marine protected areas; marine reserves; recruitment; reserve design; reserve monitoring.
Genetic analyses of marine population structure often find only slight geo- graphic differentiation in species with high dispersal potential. Interpreting the significance of this slight genetic signal has been difficult because even mild genetic structure implies very limited demographic exchange between populations, but slight differentiation could also be due to sampling error. Examination of genetic isolation by distance, in which close populations are more similar than distant ones, has the potential to increase confidence in the significance of slight genetic differentiation. Simulations of one-dimensional stepping stone populations with particular larval dispersal regimes shows that isolation by distance is most obvious when comparing populations separated by 2-5 times the mean larval dispersal distance. Available data on fish and invertebrates can be calibrated with this simulation approach and suggest mean dispersal distances of 25-150 km. Design of marine reserve systems requires an understanding of larval transport in and out of reserves, whether reserves will be self-seeding, whether they will accumulate recruits from surrounding exploited areas, and whether reserve networks can exchange recruits. Direct measurements of mean larval dispersal are needed to understand connectivity in a reserve system, but such measurements are extremely difficult. Genetic patterns of isolation by distance have the potential to add to direct measurement of larval dispersal distance and can help set the appropriate geographic scales on which marine reserve systems will function well.
In 1987 a large area (similar to 13 700 km(2)) associated with 2 offshore banks on the Scotian Shelf (Nova Scotia, Canada) was closed to commercial trawling for groundfish in order to protect the juvenile stages of haddock Melanogrammus aeglefinus from discarding. We assessed possible changes in the finfish community structure before and after the closure. Species abundance data collected annually since 1970 were subjected to multivariate analyses such as cluster analysis and a randomization/permutation test. Finfish community composition was significantly different after the implementation of the closure, and several species contributed to the post-closure difference including herring Clupea harengus, winter flounder Pseudopleuronectes americanus and redfish Sebastes sp., which showed dramatic increases in abundance. Haddock was the dominant species throughout the entire period. These findings suggest that several members of the finfish community benefited from the area closure. However, community structure in a reference area that has never been closed to fishing (Browns Bank) became more similar to the community structure in the closed area, contrary to our expectations. We provide support for the hypothesis that the dynamics of the Browns Bank area finfish community are coupled to the closed area through spillover based on several lines of inquiry, including positive relationships between abundance and area occupied of the dominant species and non-contemporaneous increases in species abundance between the closed area and the Browns Bank area with lags ranging from 1 to 3 yr. This study argues that establishment of fishery closures is likely to have positive benefits to the component species at both local and regional scales; however, the time-scale for such changes appears to be relatively long in comparison to tropical systems.
The importance of non-harvested areas, marine protected areas, and management and exploitation areas (= harvest-controlled) as seeding areas of Concholepas concholepas (Bruguiere, 1789) larvae was quantitatively evaluated at intertidal and subtidal sites at Las Cruces, central Chile. Egg capsules of C, concholepas were sampled along both intertidal and subtidal strip-transects monthly in harvested, harvest-controlled and non-harvested areas from September 1990 to December 1993. Additionally, egg capsules of C, concholepas were sampled at subtidal sites in the 3 categories of areas during 1993 and 1994. Spawning activity of C, concholepas was consistently concentrated between February and July in both the intertidal and the subtidal zones. The total area occupied by egg capsules of C, concholepas was larger in non-harvested than in harvested areas; moreover, larger capsules were found in non-harvested areas. These differences in total surface occupied by egg capsules and their sizes have an important impact on the estimated number of C. concholepas larvae that would be released from harvested and non-harvested areas. We conclude that protected areas may play an important role in the natural replenishment of C. concholepas stocks.