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The impact of marine reserves: Do reserves work and does reserve size matter?

Ecological Applications

February 2003
13(sp1):117-137

DOI:10.1890/1051-0761(2003)013[0117:TIOMRD]2.0.CO;2

Authors:

Benjamin Halpern

University of California, Santa Barbara

Marine reserves are quickly gaining popularity as a management option for marine conservation, fisheries, and other human uses of the oceans. Despite the popularity of marine reserves as a management tool, few reserves appear to have been created or designed with an understanding of how reserves affect biological factors or how reserves can be designed to meet biological goals more effectively (e.g., attaining sustainable fish populations). This shortcoming occurs in part because the many studies that have examined the impacts of reserves on marine organisms remain isolated examples or anecdotes; the results of these many studies have not yet been synthesized. Here, I review the empirical work and discuss the theoretical literature to assess the impacts of marine reserves on several biological measures (density, biomass, size of organisms, and diversity), paying particular attention to the role reserve size has in determining those impacts. The results of 89 separate studies show that, on average, with the exception of invertebrate biomass and size, values for all four biological measures are significantly higher inside reserves compared to outside (or after reserve establishment vs. before) when evaluated for both the overall communities and by each functional group within these communities (carniv- orous fishes, herbivorous fishes, planktivorous fishes/invertebrate eaters, and invertebrates). Surprisingly, results also show that the relative impacts of reserves, such as the proportional differences in density or biomass, are independent of reserve size, suggesting that the effects of marine reserves increase directly rather than proportionally with the size of a reserve. However, equal relative differences in biological measures between small and large reserves nearly always translate into greater absolute differences for larger reserves, and so larger reserves may be necessary to meet the goals set for marine reserves. The quality of the data in the reviewed studies varied greatly. To improve data quality in the future, whenever possible, studies should take measurements before and after the creation of a reserve, replicate sampling, and include a suite of representative species. Despite the variable quality of the data, the results from this review suggest that nearly any marine habitat can benefit from the implementation of a reserve. Success of a marine reserve, however, will always be judged against the expectations for that reserve, and so we must keep in mind the goals of a reserve in its design, management, and evaluation.

Sizes of the reserves reviewed in this study. Reserve size is in square kilometers and is binned on a log scale. The range of reserve sizes is 0.002-846 km 2 .

…

Log difference ratios (inside a reserve vs. outside, or after a reserve vs. before) for each biological measure for overall values as a function of reserve size. Data are plotted as the log of the ratio vs. the log of reserve size. Because the ratio is log-transformed, lines drawn at log ratio 0 show where reserves had no effect. Points above this line represent values greater than zero for the biological measure; points below the line represent values less than zero. In all cases except invertebrate biomass, log ratio values were significantly different from zero (Table 2). The slopes of all regression lines are not significantly different from zero (P values for linear regression analyses are in the upper left corner of each plot), indicating that reserves of all sizes showed similar proportional differences to nonreserve areas.

…

Log difference ratio of each biological measure for planktivore/invertebrate eaters as a function of reserve size. See Fig. 3 legend for explanation of the graphs.

…

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S117

Ecological Applications,

13(1) Supplement, 2003, pp. S117–S137

2003 by the Ecological Society of America

THE IMPACT OF MARINE RESERVES: DO RESERVES WORK AND DOES

RESERVE SIZE MATTER?

ENJAMIN

S. H

ALPERN

Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106 USA

Abstract.

Marine reserves are quickly gaining popularity as a management option for

marine conservation, ﬁsheries, and other human uses of the oceans. Despite the popularity

of marine reserves as a management tool, few reserves appear to have been created or

designed with an understanding of how reserves affect biological factors or how reserves

can be designed to meet biological goals more effectively (e.g., attaining sustainable ﬁsh

populations). This shortcoming occurs in part because the many studies that have examined

the impacts of reserves on marine organisms remain isolated examples or anecdotes; the

results of these many studies have not yet been synthesized. Here, I review the empirical

work and discuss the theoretical literature to assess the impacts of marine reserves on

several biological measures (density, biomass, size of organisms, and diversity), paying

particular attention to the role reserve size has in determining those impacts. The results

of 89 separate studies show that, on average, with the exception of invertebrate biomass

and size, values for all four biological measures are signiﬁcantly higher inside reserves

compared to outside (or after reserve establishment vs. before) when evaluated for both

the overall communities and by each functional group within these communities (carniv-

orous ﬁshes, herbivorous ﬁshes, planktivorous ﬁshes/invertebrate eaters, and invertebrates).

Surprisingly, results also show that the relative impacts of reserves, such as the proportional

differences in density or biomass, are independent of reserve size, suggesting that the effects

of marine reserves increase directly rather than proportionally with the size of a reserve.

However, equal relative differences in biological measures between small and large reserves

nearly always translate into greater absolute differences for larger reserves, and so larger

reserves may be necessary to meet the goals set for marine reserves.

The quality of the data in the reviewed studies varied greatly. To improve data quality

in the future, whenever possible, studies should take measurements before and after the

creation of a reserve, replicate sampling, and include a suite of representative species.

Despite the variable quality of the data, the results from this review suggest that nearly

any marine habitat can beneﬁt from the implementation of a reserve. Success of a marine

reserve, however, will always be judged against the expectations for that reserve, and so

we must keep in mind the goals of a reserve in its design, management, and evaluation.

Key words: marine reserves; reserve design; reserve effect; reserve size; trophic cascades.

NTRODUCTION

Marine reserves (also called marine protected areas,

no-take zones, marine sanctuaries, etc.) have recently

become a major focus in marine ecology, ﬁsheries man-

agement, and conservation biology. Interest stems in

part from the realization that traditional forms of ﬁsh-

eries stock management are inadequate, as evidenced

by the historical and recent collapse of many ﬁsheries.

In addition, traditional management methods such as

maximum sustainable yield estimates are inadequate

for addressing the multiple types of anthropogenic im-

pacts on marine life such as over-ﬁshing, certain ﬁshing

methods, pollution, coastal development, and other hu-

man-derived impacts. Marine reserves have been pro-

posed as an efﬁcient and inexpensive way to maintain

and manage ﬁsheries while simultaneously preserving

Manuscript received 27 September 1999; revised 1 March

2001; accepted 30 March 2001; feature accepted 21 February

2002. For reprints of this Special Issue, see footnote 1, p. S3.

biodiversity and meeting other conservation objectives

as well as human needs (Plan Development Team

[PDT] 1990, Ballantine 1992, Dugan and Davis 1993,

Bohnsack 1996, Nowlis and Roberts 1997, Allison et

al. 1998, Lauck et al. 1998).

Despite the popularity of marine reserves as a man-

agement tool, decisions on the design and location of

most existing reserves have largely been the result of

political or social processes (Jones et al. 1992, Agardy

1994, McNeill 1994); until very recently, little work

has been done to understand or include biological con-

siderations in reserve placement or design. A fair

amount of recent work has attempted to try to under-

stand and quantify the biological impact of marine re-

serves. However, these efforts have been scattered

around the world and in the scientiﬁc literature, so the

results are often not easily accessible to people trying

to design marine reserves. Relatively little work has

been done to assess the success of reserves in general

(Roberts and Polunin 1991, 1993, Jones et al. 1992,

S118

BENJAMIN S. HALPERN

Ecological Applications

Special Issue

Dugan and Davis 1993), and all of it has been anecdotal

in nature. In an attempt to draw together all of these

results, I have reviewed and synthesized the ﬁndings

of marine reserve evaluations in order to assess the

effectiveness of marine reserves. In particular, I eval-

uated how marine reserves have affected four biolog-

ical measures (density, biomass, size, and diversity of

organisms) within the reserves, and examined if re-

serve size inﬂuences the magnitude of these reserve

effects. Speciﬁcally, I asked:

1) What are the impacts of marine reserves on the

above four biological measures?

2) Is the magnitude of the effect of a reserve on

biological measures related to the size of the reserve

(i.e., does size matter)?

3) Does trophic structure change with the imple-

mentation of a reserve?

4) Does the goal of a reserve (e.g., ﬁshery manage-

ment vs. biodiversity conservation) inﬂuence how large

a reserve needs to be?

5) What biases or problems exist in the current lit-

erature regarding reserve assessment and/or reserve de-

sign, and what can be done to remedy these problems?

Theoretical endeavors have produced some predic-

tions for a few of these questions. Modeling efforts

aimed at ﬁsheries management have suggested that bio-

mass of reproductively active ﬁsh (spawning stock bio-

mass) should generally increase as a result of reserve

protection (Polacheck 1990, DeMartini 1993, Quinn et

al. 1993, Attwood and Bennett 1995, Man et al. 1995).

Concomitantly, reserves are predicted to increase spill-

over of ﬁshes to areas outside of the reserve, an effect

that is likely to be positively correlated with higher

density of ﬁshes inside the reserve (Russ et al. 1992,

Hockey and Branch 1994). Organism size and diversity

are generally assumed to follow these trends as well,

since reserve protection should allow for individual

organisms to grow larger (i.e., not be ﬁshed out of the

system once they reach a certain size) and may also

provide protection for species that are normally ﬁshed

to local extinction. This review will help assess the

validity of these predictions.

No direct efforts have been made to evaluate how

reserve size itself affects the impact of reserves on any

of these biological measures, although it is usually as-

sumed that bigger reserves will always be ‘‘better.’’

The literature on the theory of island biogeography

(MacArthur and Wilson 1967; reviewed by Diamond

and May 1976) predicts that species diversity should

increase with area, and so larger reserves should con-

tain more species. However, the theory of island bio-

geography does not address how reserve protection

might inﬂuence species diversity at a particular loca-

tion, and so few predictions can be made about how

reserve size might affect the impact marine reserves

have on species diversity. This review in particular

addresses if reserve size affects the impact marine re-

serves might have on all four biological measures (den-

sity, biomass, size, and diversity).

Marine reserves are also predicted to lead to trophic

cascade effects, in that protection from ﬁshing may

allow top predators to become more abundant in a re-

serve, which may in turn reduce the abundance of prey,

releasing the subsequent trophic level from predation

pressure, etc. (Steneck 1998; see also Sala et al. 1998).

If this general pattern holds across reserves, then large

increases in carnivore abundance and/or size should be

associated with smaller differences or even reductions

in prey populations.

Independent of the many predictions of the above

models, most people simply assume that marine re-

serves provide the functions expected of them (such as

increasing numbers of ﬁsh within and outside a re-

serve). Reserve success stories end up serving as the

primary evidence for these assumptions, even though

many examples exist where reserves did not provide

the necessary functions. The main goal of this review

is to evaluate the success of marine reserves in a quan-

titative way, and to assess what role reserve size plays

in determining the magnitude of the reserve effect.

ETHODS

Source selection

This review addresses the biological impacts of ma-

rine reserves and the implications of these impacts for

reserve design. I limited my literature search, therefore,

primarily to ecological journals. Policy and manage-

ment journals, which deal with issues such as cost-

efﬁcient design, selection criteria, prioritization

schemes, etc., do not include biological data and so are

not relevant to this review.

I searched for empirical research in which reserves

were actually surveyed. Criteria for inclusion of a study

in this review were that (1) data from both before and

after the creation of the reserve or from inside and

outside of a reserve were reported, (2) no known har-

vesting occurred within the marine reserve, and (3) the

observations measured at least some of the biological

variables of interest. Studies examining processes only

inside a reserve were not included because they did

not have a control site. Similarly, I omitted surveys

concerning the impact of marine reserves on ﬁshing

effort because they did not address biological mea-

sures. Finally, I looked only at no-take reserves because

it allowed me to exclude ﬁshing effort as a possible

factor affecting the impact of reserves. I included work

from gray literature (e.g., conference proceedings, re-

ports, lab bulletins, etc.) if it met my criteria. Using

these criteria, I found 89 empirical studies of marine

reserve effect that made 112 independent measures of

marine reserves (i.e., some studies examined several

reserves, and some reserves were examined by several

different studies). Of these 89 studies, I was able to

February 2003 S119

IMPACT OF MARINE RESERVES

ABLE

1. Fish families and their functional group classiﬁ-

cations.

Herbivores

Planktivores/

invertebrate

eaters Carnivores

Acanthuridae

Kyphosidae

Pomacentridae

Scaridae

Siganidae

Zanclidae

Anthiidae

Apogonidae

Atherinidae

Balistidae

Belonidae

Caesionidae

Batrachoididae

Bothidae

Carangidae

Carcharhinidae

Centracanthidae

Centropomidae

Chaetodontidae

Clupeidae

Dasyatidae

Diodontidae

Gerreidae

Gobiidae

Holocentridae

Labridae

Coracinidae

Gadidae

Haemulidae

Letherinidae

Lutjanidae

Muraenidae

Pomatomidae

Sciaenidae

Lagocephalidae

Myliobatidae

Mullidae

Nemipteridae

Pomacanthidae

Syngnathidae

Tetraodontidae

Scombridae

Scorpaenidae

Serranidae

Soleidae

Sparidae

Sphyranidae

Notes:

These classiﬁcations are natural groupings based on

those made in the reviewed literature. Mugilidae, Elopidae,

Ariidae, Ephippidae, Cichlidae, and Blennidae, which were

observed in a few of the studies reviewed here, do not ﬁt well

into a single category and so are not included in functional

group analyses. They are included in overall values and anal-

yses.

use 81 for qualitative analyses and 69 for quantitative

analyses.

I also examined theoretical articles for predictions

about how biological measures should respond to re-

serve protection, but only if a signiﬁcant portion of the

article addressed biological issues of marine reserve

design. These articles often proposed models or offered

reviews of speciﬁc issues (many of these I discussed

Introduction

). Most management and policy litera-

ture addresses logistical, economic, or sociological as-

pects of marine reserves and was not included in this

review.

Data extraction and formatting

To determine the size of a reserve, I considered only

the part of the reserve that was fully protected (i.e., a

no-take zone; in two cases it was a zone of no spear-

ﬁshing). If the source paper did not mention the reserve

size speciﬁcally, I used the World Conservation Mon-

itoring Center’s web site,

McArdle (1997), or com-

munication with the authors of the studies to determine

reserve size. I was unable to ﬁnd sizes for ﬁve reserves

and therefore only include them in my analyses of gen-

eral reserve effect. The appendix lists the reserve sizes

I was able to ﬁnd.

Although the way in which data were reported varied

among the studies of reserve effect, the type of data

reported was fairly consistent. Studies examined the

effect of marine reserves on the density, biomass, mean

size, and diversity (measured as species richness) of

organisms within the reserves, although few studies

examined all four of these biological variables. The

effect of the marine reserves on these measures was

reported either as a qualitative trend (e.g., ‘‘ﬁsh density

was higher in the marine reserve’’) or a quantitative

difference (e.g., ‘‘lobster biomass increased 250%

since the date of inception of the marine reserve’’). I

recorded both of these types of data as a trend of the

reserve having higher values than nonreserve areas.

The latter example I also recorded as a numerical dif-

ference of 3.5 (i.e., 250% equals a 3.5-fold increase).

An overall trend and the mean for all numerical val-

ues were calculated for all species examined in a given

study, regardless of the number of species in each

study. In ﬁve cases (Moreno et al. 1984, 1986, Castilla

and Duran 1985, Cole et al. 1990, MacDiarmid and

Breen 1992), several species were examined but results

were presented for only one or a few species. Overall

values in these cases represent only the species with

reported data. Since many studies only examined a sin-

gle species, overall values can represent anywhere from

one to several hundred species.

In separate analyses, I examined data by functional

group when it was provided. The functional groups

were invertebrates, herbivorous ﬁshes, planktivorous/

URL:

http://www.wcmc.org.uk:80/marine/data/

invertebrate-eating ﬁshes, and carnivorous ﬁshes (see

Table 1 for ﬁsh family classiﬁcations). Data for families

or species that did not fall into one of these functional

groups (such as omnivores) were omitted since there

were too few of these data to allow for separate sta-

tistical analyses. I treated each family (or species if the

study only looked at a single or a few species) as a

separate data point for analysis. This method avoided

redundancy; many studies collected data for only one

functional group, and if I were to sum all data for a

functional group from a study and then calculate a

mean, the functional group results would look very

similar to the overall values. Calculating grand means

of the functional-group data allowed for a more ac-

curate picture of the effect reserve protection can have

on a particular family or species, since each family or

species value was recorded as a separate datum and

not summed across all organisms within the same func-

tional group within a study.

I extracted qualitative and quantitative data from the

text, tables, and bar graphs presented in the articles.

While data extraction from text and tables was straight-

forward, data extracted from graphs were slightly less

precise, since these values were estimated by measur-

ing the height of the bars against the

-axis. I tabulated

data regardless of the reported signiﬁcance values.

Overall values of differences between reserve and non-

reserve areas were often provided, or I calculated them

S120

BENJAMIN S. HALPERN

Ecological Applications

Special Issue

. 1. Sizes of the reserves reviewed inthis

study. Reserve size is in square kilometers and

is binned on a log scale. The range of reserve

sizes is 0.002–846 km

as the mean of the summed values for all groups or

species listed. For example, Roberts (1995) lists the

overall density and biomass for ﬁsh inside and outside

the marine reserve in Saba, Netherland Antilles, as well

as density values for several families of ﬁsh. I used the

overall totals to calculate differences in biological mea-

sures as a result of reserve protection, and then cal-

culated values for each family and averaged those to

give functional group differences.

Because overall values integrate across all species

studied, an extremely abundant species can dispropor-

tionately inﬂuence these overall values. For example,

Cole et al. (1990) report that all but one species had

higher density inside the reserve compared to outside.

The one species that was very abundant, however, was

much more numerous outside the reserve, and so the

mean overall value ends up indicating lower density

levels as a result of reserve protection. Analysis of the

data at the functional group level as well as for overall

values allowed this sort of ‘‘single-species’’ inﬂuence

to be isolated. Although total density for all ﬁsh was

lower inside the reserve (the entire community value),

functional group analysis showed that most species had

higher values inside the reserve.

Data from relevant work were occasionally described

in articles that I could not obtain (Ayling and Ayling

1986, as cited in Jones et al. 1992; Spanier 1984 and

Hunt et al. 1991, both cited in Childress 1997); I in-

cluded these data as separate entries in my database,

but only as trends (except for one datum). All studies

and data used in my analyses are listed in the appendix.

Most studies compared inside vs. outside a reserve

at a single point in time, and so I report these data as

the ratio of these values (inside divided by outside).

Several studies were able to survey an area before and

after a reserve was put in place; I present these data

as the ratio of after divided by before. A few studies

had both before/after and inside/outside (for reference)

data (Alcala 1988, Russ and Alcala 1989, 1996, 1998

, Alcala and Russ 1990, Bennett and Attwood 1991,

Dufour et al. 1995, Edgar and Barrett 1999). For these

cases, I report values as the ratio of after to before,

adjusted by the difference in the reference (outside)

values over the same time period. Occasionally data

were collected after protection of a marine reserve

broke down (Davis 1977, Russ and Alcala 1996,

1998

). To standardize these results with the rest of

the data, I report these values as if the effect were

reversed. In other words, if density of a ﬁsh dropped

with the loss of protection, I recorded the reserve as

increasing the density of that ﬁsh.

Ratios greater than 1 represent higher levels of a

biological measure within a reserve relative to non-

reserve areas, while ratios between zero and one rep-

resent lower levels. If a biological measure began at

or went to zero, I was unable to create a ratio and was

therefore unable to use these data. To normalize the

distribution of the ratios, I log-transformed the values.

I use these log ratios for all analyses. In the end I back

transformed ratios to aid in interpretation of the results.

A reported ratio of 2.5 means that the value inside a

reserve or after the establishment of a reserve was 2.5

times (or 150%) higher relative to outside (or before)

the reserve.

In a few cases the trend was reported as not statis-

tically signiﬁcant, but I still used the data provided to

calculate ratios. In these cases I recorded the trend as

no difference but used the ratio for calculations of re-

serve and size effects on biological measures. For the

majority of these cases the nonsigniﬁcant difference is

in a negative direction; therefore, using these values

can only add a slight bias against ﬁnding a positive

reserve effect.

In seven cases (see Appendix), data from several

noncontiguous reserves were presented as a single val-

ue. I treated these values as representing a single re-

serve of the summed sizes of the reserves. In only one

case was the total size

30 km

, and so this method

should not create a bias for large reserves in my anal-

yses of reserve size effects.

Several studies made multiple measurements in cat-

egories I did not consider in this review, such as by

season (

2), depth (

3), habitat (

2), size

classes (

1), or for several sites within a reserve (

6). In these cases, I averaged the values into a single

value. When data for multiple years were presented, I

February 2003 S121

IMPACT OF MARINE RESERVES

. 2. Differences in biological measures (density [no./

area], biomass [mass/area], mean size of organism, and di-

versity [total species richness]) between inside a reserve and

outside a reserve (or after vs. before) for all organisms (A)

and for each functional group (B–E). The numbers of inde-

pendent reserve measurements that were associated with each

trend are plotted for each biological measure: white bars rep-

resent lower values inside the reserve, gray bars represent no

difference between reserve and nonreserve areas, and dark

bars represent highervalues inside thereserve.

valuesabove

the bars are signiﬁcance values for chi-square tests values

←

for chi-square tests of differences between frequencies among

observations (null hypothesis: no difference in frequency);

, not signiﬁcant.

used only the data for the ﬁnal year to allow for the

longest time of protection and minimize the likelihood

of a time effect (see

Discussion

). If reserve protection

was initiated during the course of a study, then the data

were treated as a before/after case.

In a few cases I needed to make minor calculations

to make reported data congruent with the other studies.

For example, if only a range of differences in some value

was reported, I used the median of this range to ap-

proximate the mean difference. In two cases, only abun-

dance values were given, with no reference to the area

surveyed or the effort expended (Hunt et al. 1991; cited

in Childress 1997, and Grigg 1994). I used these data

to create ratio values, even though they might not ac-

curately reﬂect the actual density of ﬁsh within the re-

serves. All other density values are per area or per effort.

A ﬁnal difﬁculty arose in cases where only trends

were reported and some species or families showed one

trend while others showed a different trend. This oc-

curred only three times (Duran and Castilla 1989, Ben-

nett and Attwood 1991, Watson and Ormond 1994). In

these cases, I used the trend for the majority of the

species or families for overall values. For example,

Watson and Ormond (1994) reported that 15 species

had greater density inside the reserve, 34 showed no

difference, and two showed lower density. I recorded

this as a trend of no difference for overall density, even

though many species did have greater numbers inside

the reserve.

ESULTS

General descriptions of reserves studied

Reserve size varied over six orders of magnitude (see

Fig. 1). Mean reserve size was 44.1 km

, although half

of the reserves were between 1 and 10 km

and the

median reserve size was 4.0 km

. The largest reserve

(which was actually a collection of reserves) was 846

; the smallest reserve was 0.002 km

The number of species surveyed in each study also

varied widely, but the majority of studies fell into one

of two categories: almost half of the measurements

were of ﬁve or fewer species, and almost half were of

50 or more species.

The distribution between studies conducted in trop-

ical climates and those conducted in temperate climates

was fairly equal. Forty-one percent of studies were con-

ducted in temperate regions and the rest were con-

ducted in tropical areas. However, nearly all of the

studies looked at organisms associated with reefs—

coral reefs for tropical regions and rocky reefs and

intertidal zones for temperate areas (although other

S122

BENJAMIN S. HALPERN

Ecological Applications

Special Issue

ABLE

2. Mean squares and

ratios for one-way ANOVA tests of the association of mean reserve size and the three trend

categories (less than, no difference, greater than) for each biological measure in each functional group.

Effect

Density

Biomass

Organism size

Diversity

2, 97

2, 38

2, 49

2, 56

2528.1

204 465.0

594.8

3798.3

0.179

11.084

0.068

0.291

2, 116

2, 53

2, 24

2, 23

2821.9

610.8

1520

119.3

0.817

0.044

0.205

1.342

Notes: P

values for all cases are

0.07, except for overall biomass (

0.002), suggesting that there is no effect of

reserve size in qualitative changes associated with reserve establishment. Abbreviations: O

overall, C

carnivores, H

herbivores, P/I

planktivores/invertebrate eaters, and I

invertebrates.

†Only two trend categories were available for these tests.

habitats such as seagrass beds existed within these re-

serves).

Qualitative results

Effect of marine reserves on biological measures

.—

Overwhelmingly, reserves were associated with higher

values of density, biomass, organism size, and diversity

of species for overall trends and for all four functional

groups (Fig. 2). Invertebrate biomass and size were the

only exceptions. Moreover, few reserves showed lower

levels for any biological measure. This pattern is par-

ticularly striking for the analysis of all species com-

bined (overall group; Fig. 2A): 63% of reserves had

higher density (Chi-square test,

0.001), 90% of

reserves had higher biomass (

0.001), 80% of re-

serves had larger organisms (

0.001), and 59% of

reserves had higher diversity (

0.001). Only a small

minority of reserves had lower values for these bio-

logical measures (7%, 0%, 2%, and 10% of reserves

had lower density, biomass, organism size, and diver-

sity, respectively). Reserves in general, therefore, usu-

ally had higher values, less often had no effect, and

rarely were associated with lower values of the four

biological measures.

Results are similarly striking when analyzed by func-

tional group. For carnivorous ﬁshes (Fig. 2D), 66% of

reserves had higher density (

0.001), 84% of re-

serves had higher biomass (

0.001), 83% of re-

serves had larger organisms (

0.001), and 74% of

reserves had higher diversity (

0.05). Reserves rare-

ly were associated with lower values for any measure

for carnivores; lower values occurred in only 3–17%

of the cases (Fig. 2D). For planktivorous and inver-

tebrate-eating ﬁshes (Fig. 2C), 62% of reserves had

higher density (

0.001), 55% of reserves had higher

biomass (

0.025), 55% of reserves had higher di-

versity (

0.005), and 89% of reserves had larger

organisms (

0.066). Although the difference in the

trend for size of planktivorous ﬁshes is not quite sta-

tistically signiﬁcant, all but one of the reserves were

associated with larger such organisms. For the other

biological measures, only 5–18% of the reserves had

lower values (Fig. 2C).

Herbivorous ﬁshes showed similar patterns (Fig. 2B):

53% of reserves had higher density (

0.01) and 63%

of reserves had higher biomass (

0.05). No difference

existed between reserves and nonreserves for herbivore

size or diversity; however, there was only one case of

a lower value for both variables within reserves and six

of nine cases showed positive differences in herbivore

size. Therefore, herbivore size and diversity are usually

higher or unchanged as a result of reserve protection.

Herbivore density and biomass were lower in only 13%

and 11% of the reserves, respectively.

Finally, for the invertebrate functional group (Fig.

2E), 50% of the reserves had higher density (

0.05)

and 83% had larger organisms (

0.001), but biomass

and diversity were not statistically different between

reserve and nonreserve areas. Sample size for these

latter two categories was fairly small (

11 for bio-

mass and

12 for diversity), and so it is difﬁcult to

draw robust conclusions.

In summary, most of the biological measures were

higher inside reserves. The next most common result was

no difference from the non-reserve conditions. Rarely did

reserves have lower values for density, biomass, size, or

diversity, both overall and within functional groups.

The role of reserve size in determining reserve effect

I also used the qualitative data to investigate whether

reserve size inﬂuences the trends seen in the previous

section. For instance, were reserves that showed the

largest differences more likely to be larger reserves?

In all cases but one, the mean size of reserves for each

of the three trend categories (less than, no difference,

and greater than) for both overall and functional group

categories were statisticallyindistinguishable(one-way

ANOVA,

0.08 for all cases; see Table 2). This

result implies that the proportional effect of a reserve

is independent of reserve size.

The only case where reserve size appeared to have

an effect was for overall biomass. In this case, reserves

were never associated with lower biomass levels (a

trend of ‘‘less than’’). The mean size of a reserve in

the no difference category was larger than the average

reserve size in the ‘‘greater than’’ category (Tukey test,

0.05), but one of the three reserves in the no

February 2003 S123

IMPACT OF MARINE RESERVES

ABLE

2. Extended.

P/I

2, 81

1, 17

1, 9

2, 44

30.9

170

24.3

377.6

0.180

2.601†

1.193†

2.177

2, 51

2, 17

2, 9

2, 30

67.2

92.3

140.6

157.5

0.501

1.456

3.995

0.792

2, 53

1, 10

2, 28

2, 11

12327

360.3

256.3

14282

1.525

2.068†

1.156

0.733

. 3. Log difference ratios (inside a reserve vs. outside, or after a reserve vs. before) for each biological measure for

overall values as a function of reserve size. Data are plotted as the log of the ratio vs. the log of reserve size. Because the

ratio is log-transformed, lines drawn at log ratio

0 show where reserves had no effect. Points above this line represent

values greater than zero for the biological measure; points below the line represent values less than zero. In all cases except

invertebrate biomass, log ratio values were signiﬁcantly different from zero (Table 2). The slopes of all regression lines are

not signiﬁcantly different from zero (

values for linear regression analyses are in the upper left corner of each plot),indicating

that reserves of all sizes showed similar proportional differences to nonreserve areas.

difference category was nearly an order of magnitude

larger than all other reserve sizes.

Quantitative results

Functional group response to reserve establish-

ment

.—As expected, mean values of ratios for all bi-

ological measures in each functional group, except in-

vertebrate biomass and size, are signiﬁcantly greater

than zero (two-tailed Student’s

test,

0.025 for all

cases) indicating a consistently positive effect of re-

serve establishment on density, biomass, size of or-

ganism, and diversity (Table 3). This pervasive positive

effect can be seen clearly in Figs. 3–7, where results

for each reserve are plotted against reserve area. Nearly

all points in all ﬁgures lie above the log ratio

0 line,

indicating that values are almost always higher inside

of reserves (or after reserve protection).

The two exceptions to this are invertebrate size and

biomass. Invertebrate size inside reserves is signiﬁ-

cantly less than zero (two-tailed Student’s

test,

0.005), and invertebrate biomass is indistinguishable

from zero (two-tailed Student’s

test,

0.053), in-

dicating that reserves may lower invertebrate size and

have little effect on invertebrate biomass. However,

invertebrate biomass values were highly inﬂuenced by

extremely bimodal data and invertebrate size values

were skewed by a single low datum (see Fig. 7). Re-

moval of this single datum leads to higher mean size

values roughly equal to those for all other functional

groups,

;

20% (a 1.2-fold increase). I discuss these

factors in greater detail in the

Discussion.

To determine if marine reserves affect functional

groups differently, I tested if ratio values for density,

biomass, size of organism, and diversity were different

from each other. In all cases but two, ratio values of

the functional groups were not statistically different

from each other or from overall values (one-way AN-

OVA,

0.13 for all cases excluding the two excep-

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BENJAMIN S. HALPERN

Ecological Applications

Special Issue

ABLE

3. Mean ratios of each biological measure (value inside the reserve divided by the value outside of the reserve or

before the creation of the protected area), for each functional group and for all trophic groups together.

O C P/I H I

Density

Biomass

Organism size

Diversity

1.91

0.28***

2.92

0.92***

1.31

0.07***

1.23

0.07***

2.21

5.63*

3.12

1.23***

1.31

0.10***

2.40

0.43***

1.85

0.56***

2.38

2.19**

1.23

0.13***

1.35

0.37***

2.39

2.67**

3.33

4.82**

1.52

0.36**

1.39

0.27***

2.04

6.15*

0.25

2.23

0.80

0.17***

1.08

0.22**

Notes:

Values are presented as the mean (calculated from the log-transformed data, then back transformed), plus or minus

the standard error (calculated from the nontransformed data). Invertebrate biomass and organism size and herbivore organism

size all have six or fewer cases. Abbreviations: O

overall, C

carnivores, H

herbivores, P/I

planktivores/invertebrate

eaters, and I

invertebrates.

values for two-tailed Student’s

tests, testing if the mean values are equal to zero, are as

follows: *

0.05, **

0.025; ***

0.001. For invertebrate biomass,

0.053.

. 4. Log difference ratio of each biological measure for herbivores as a function of reserve size. See Fig. 3 legend

for explanation of the graphs. No

value is reported for organism size since there were too few data to perform a regression

analysis.

tions). The two exceptions are invertebrate biomass,

which had lower mean values inside (or after) reserves

(one-way ANOVA,

0.025), and carnivore diver-

sity, which had much higher values than other groups

(one-way ANOVA,

0.0001).

Interestingly, these results do not show a consistent

pattern indicative of trophic cascades, where higher

densities or biomass of carnivores would be matched

by decreases in prey functional groups. In the discus-

sion, I offer possible explanations for why trophic cas-

cades were not obviously present here.

Effects of reserve size

Figs. 3–7 show the log of the ratio for each biological

measure plotted against reserve size for overall values

and for each functional group. The slopes of the re-

gressions for all measures in all functional groups vs.

reserve size are not signiﬁcantly different from zero

(linear regression analysis,

0.12 for all cases; see

ﬁgures for exact

values), indicating that reserve size

has no apparent impact on proportional differences.

There were only four data points for herbivore size,

and so regression analysis was not possible for this

case. Thus, the relative impact of reserves on all bio-

logical measures in each functional group was signif-

icantly positive, and this relative impact appears to be

independent of reserve size. I discuss the implications

of this in the

Discussion.

ISCUSSION

These results demonstrate that reserves are associ-

ated with higher values of density, biomass, organism

size, and diversity for overall values as well as for all

functional groups. This is strong support for the many

claims made that marine reserves ‘‘work.’’ The results

of this study also support the predictions of many ﬁsh-

eries models; reserve protection should increase bio-

February 2003 S125

IMPACT OF MARINE RESERVES

. 5. Log difference ratio of each biological measure for planktivore/invertebrate eaters as a function of reserve size.

See Fig. 3 legend for explanation of the graphs.

. 6. Log difference ratio of each biological measure for carnivores as a function of reserve size. See Fig. 3 legend

for explanation of the graphs.

mass (Polacheck 1990, DeMartini 1993, Quinn et al.

1993, Man et al. 1995) and density (which is probably

correlated to the spillover of ﬁsh to nonreserve areas;

Russ et al. 1992, Hockey and Branch 1994) within a

reserve. This is an encouraging conclusion in that at

least some of the ﬁshery and conservation expectations

for current and future marine reserves have been met

and can be realized.

These results also provide some guidelines for the

magnitude of change in biological measures we can

expect as a result of marine reserve protection. On

average, creating a reserve appears to double density,

nearly triple biomass, and raises organism size and di-

versity by 20–30% relative to the values for unpro-

tected areas (see overall values in Table 3). It is im-

portant to remember, however, that these values have

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BENJAMIN S. HALPERN

Ecological Applications

Special Issue

. 7. Log difference ratio of each biological measure for invertebrates as a function of reserve size. See Fig. 3 legend

for explanation of the graphs.

considerable variance and cannot be used to predict

how a speciﬁc reserve will affect particular organisms

and communities.

The results for invertebrates are less clear than for

the other functional groups, but nevertheless do not

detract from the general results. Invertebrate density

trends and numerical values were predominantly pos-

itive, as was the case for the other functional groups.

The invertebrate size results might at ﬁrst glance appear

to be contradictory; qualitative results showed that a

vast majority of reserves held larger organisms while

quantitative data imply that invertebrates are generally

smaller in reserves. As was mentioned in the

Results,

however, the quantitative data were highly inﬂuenced

by a single datum; removal of that datum led to new

mean size values roughly equal to those for all other

functional groups, about 20% higher inside the re-

serves. For invertebrate diversity, analysis showed that

reserves were equally likely to be associated with low-

er, no difference, or higher trend values. However, sam-

ple size was small and the quantitative value was sig-

niﬁcantly positive, indicating that, on average, diver-

sity will be higher inside reserves. Invertebrate biomass

was lower within reserves, but as already described,

these data were extremely bimodal, with reserves lead-

ing to either much higher or much lower levels of bio-

mass. For the most part, the high values came from

studies on lobsters and exploited intertidal inverte-

brates, while the lower values were from measurements

of urchin biomass levels, which dropped within a re-

serve when numbers of urchin-feeding ﬁshes increased.

The implication here is that, for invertebrate biomass

in particular, the effect of reserve protection will de-

pend in part on the exploitation level of the invertebrate

and its position in the food chain. I discuss below other

ways in which the organisms being studied might im-

pact the way in which reserves are perceived to per-

form.

It is also important to distinguish between how di-

versity is affected by reserve protection as distinct from

the other three biological measures. Diversity in this

review is actually species richness, which is not mea-

sured per unit area or effort, as are density and biomass.

While it is quite possible for both small and large re-

serves to have the same initial values of density or

biomass (e.g., 2 ﬁsh/m

), larger reserves almost always

initially contain more species than smaller reserves.

Therefore, ﬁnding equal proportional increases in di-

versity for small and large reserves actually indicates

a greater absolute increase in species numbers for the

larger reserve. Furthermore, a single individual of a

new species has a large impact on species richness

measures, whereas a single individual has little impact

on overall density, biomass, or organism size. Larger

reserves are more likely to contain rare species simply

because they encompass a greater area. In addition,

diversity values will be somewhat dependent on the

effort used to measure them; a long search will more

likely produce a rare species than a short search. How-

ever, effort was not standardized in any way between

studies.

A surprising result of this review is that the relative

magnitude of the effect of a reserve on a biological

measure appears to be independent of reserve size. A

small reserve can double biomass per unit area just as

likely as a large reserve can. This result holds even for

February 2003 S127

IMPACT OF MARINE RESERVES

extremely small reserves; for example, reserves in both

St. Lucia (0.026 km

) and Chile (Las Cruces: 0.044

) were associated with signiﬁcantly larger values

in the biomass and size of the organisms within the

reserve compared to nonreserve areas (Castilla and

Bustamante 1989, Roberts and Hawkins 1997). The

reserve in St. Lucia is particularly noteworthy because

even large, mobile ﬁshes seemed to beneﬁt from the

small reserve, suggesting that small reserves can work

even for mobile organisms. Furthermore, many of the

small reserves were located haphazardly, yet still pos-

itively affected the organisms within them. If small

reserves are more strategically placed, for example on

spawning grounds or along migratory routes, their im-

pact may be even greater.

When considering the results of this review it is ex-

tremely important to keep in mind the distinction be-

tween absolute and relative effects of reserve protec-

tion. Even small reserves appear to be able to increase

density, biomass, size, and diversity of organisms, and

small and large reserves can show the same propor-

tional differences relative to nonreserve areas, but the

absolute impacts of small and large reserves will be

very different. For example, doubling ﬁsh numbers in

a small reserve from 10 to 20 ﬁsh is substantially dif-

ferent from doubling the ﬁsh numbers in a large reserve

from 1000 to 2000 ﬁsh, even though the relative change

in density might be the same for both reserves. The

goals of reserve and ﬁshery managers often include

some minimum beneﬁt level from reserves (e.g., total

catch outside the reserve, all species present and abun-

dant enough to be self-sustaining, etc.), goals that may

not be achieved if only proportional differences are

considered.

Small reserves may also be insufﬁcient for several

other reasons. Alone, small reserves may not be able

to provide signiﬁcant export functions. This review

does not examine the possibility that reserves serve as

sources for unprotected areas (sensu Pulliam 1988),

even though it is often assumed and expected that they

provide this service. Models have addressed how cur-

rent regimes might inﬂuence dispersal (e.g., Rough-

garden et al. 1988, Roberts 1997), but only a few stud-

ies have tried to infer or measure the impact of reserves

on reproductive output (Davis 1977, Davis and Dodrill

1980, Polacheck 1990, Stoner and Ray 1996, Sluka et

al. 1997, Edgar and Barrett 1999; all suggest that re-

productive output can be higher in reserves). An in-

crease in numbers or size of organisms in a reserve

will obviously increase reproductive output, but small

reserves will only be able to increase reproductive out-

put a small amount relative to target areas. For reserves

to serve as larval sources they must be large enough

to sustain themselves as well as supply the rest of the

target areas.

Another potential drawback of small reserves is their

susceptibility to catastrophic events. For example, if

an oil tanker runs aground near a small reserve, it is

likely that the entire reserve will be impacted by the

spill. If the accident occurred near part of a large re-

serve, on the other hand, it is possible that some of the

reserve would escape harm. The unaffected part of the

reserve could considerably, then, aid in the recovery

process of the damaged region.

It is also possible that very large reserves (e.g.,

500

) might provide proportionally larger values when

evaluated by density, biomass, etc. If ﬁsh within a re-

serve use several habitats throughout their life histo-

ries, it may require a very large reserve to encompass

and protect all life stages adequately. This review

would most likely not be able to detect a size threshold

effect such as this, since only seven of the reserves

studied covered

50 km

, and the only one

460 km

came from pooled data from a collection of seven

smaller reserves. Furthermore, nearly three quarters of

all the reserves studied covered

10 km

(see Fig. 1).

Such shortcomings in the data leave open the possi-

bility that large reserves affect biological measures in

a way not detectable here. While it would be desirable

to test how such a large reserve would affect such

measures, the logistics of such studies would be very

difﬁcult.

An important variable not analyzed here is the role

that the length of protection plays in determining the

magnitude of a reserve effect. Examples exist where

the magnitude of the reserve effect increased over time

(e.g., Watson et al. 1996, Russ and Alcala 1998

Conan (1986) described how lobster biomass initially

increased over several years but then receded to orig-

inal levels. In all of these cases, results would have

been different had population surveys been made at a

single point in time (or over a relatively brief period

of time), as they were in most of the studies I reviewed

here. It is difﬁcult to determine, therefore, if the pop-

ulations had actually reached equilibrium at the time

of measurement. Furthermore, the impact of a reserve

is certainly not instantaneous, but little is known about

how long it takes for a population to reach equilibrium,

or even if it ever does. I address in depth the role that

length of protection plays in determining the effect of

marine reserves elsewhere (Halpern and Warner 2002).

Many other variables could also inﬂuence the impact

of reserves on the biological resourcescontainedwithin

them. Species composition (PDT 1990, Carr and Reed

1993, Ballantine 1992, 1995, 1997, Dugan and Davis

1993, Tegner 1993, Rowley 1994), the ﬁshing intensity

around the reserve (Polacheck 1990, Russ et al. 1992,

Carr and Reed 1993, Rowley 1994, Nowlis and Roberts

1997), adult mobility or home range size of ﬁsh within

the reserve (Kramer and Chapman 1999), and the types

and quality of habitats both inside and outside the re-

serve (Salm and Clark 1989, Hockey and Branch 1994,

Agardy 1995, Nilsson 1998) have all been proposed as

variables that could be important in determining how

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BENJAMIN S. HALPERN

Ecological Applications

Special Issue

an organism responds to reserve protection. These sorts

of observations were usually not reported in the em-

pirical studies on marine reserves I used, and so I was

unable to evaluate them here. However, these other

factors should certainly be considered when setting

goals and expectations for marine reserves.

Despite that many empirical studies found trophic

cascade effects as a result of marine reserve protection

(Kenya: McClanahan and Muthiga 1988, McClanahan

and Shaﬁr 1990, McClanahan 1994, 1995, 1997, Wat-

son and Ormond 1994; Chile: Castilla and Duran 1985,

Duran and Castilla 1989; Mediterranean: Sala et al.

1998

), this pattern did not emerge from my large-scale

analyses. Instead, the densities of invertebrates, her-

bivorous ﬁshes, planktivorous/invertebrate eating ﬁsh-

es, and carnivorous ﬁshes all increased almost exactly

the same amount (see Table 3). A possible explanation

for this is that trophic cascades appear to be more likely

to occur when only a small subset of a community is

observed (Polis and Strong 1996). For example, in

Kenya (e.g., McClanahan and Shaﬁr 1990) the trophic

cascade occurred between humans, triggerﬁsh (Balis-

tidae) and a few species of sea urchins, and was not

evident in other families of ﬁsh and species of urchins

that were studied. Similarly, in Chile (Castilla and Dur-

an 1985, Duran and Castilla 1989) the cascade occurred

between humans, a single gastropod, a single mussel,

and algae. Thus trophic cascades may be masked when

entire communities are measured. In the study by

McClanahan and Shaﬁr (1990), total ﬁsh densities as

well as densities for four ﬁsh families (Labridae, Bal-

istidae, Diodontidae, and Lagocephalidae) and urchins

were measured. Urchin densities were nearly 200 times

higher outside the reserve, while Balistid density was

nearly 10-fold greater inside the reserve, exemplifying

a classic trophic cascade. When all four ﬁsh families

were considered (all are planktivorous ﬁshes/inverte-

brate eaters), ﬁsh densities dropped to only 28% higher

inside the reserve, obscuring the trophic cascade. When

family or species results are incorporated into an entire

functional group, as was the case here, trophic cascade

effects can often become muted.

Empirical tests of the effect of reserve size are need-

ed to test the robustness of the results suggested here.

To date, only one study (Edgar and Barrett 1999) has

tried to assess empirically the potential effects of ma-

rine reserve size on biological attributes of species con-

tained within the reserves. They studied four reserves

in Tasmania, three of which were

;

0.6 km

and a fourth

that was about 7 km

. The largest reserve showed many

signiﬁcant differences relative to nonreserve areas,

while the smaller reserves had only a few notable dif-

ferences. For example, in the large reserve, overall ﬁsh

size, density of large ﬁsh, abalone size, size of crayﬁsh,

mean plant cover, and species diversity of ﬁsh, inver-

tebrates, and algae all increased signiﬁcantly compared

to control sites. In the other three sites, signiﬁcant dif-

ferences were found only for density and diversity of

large ﬁsh in one reserve and density of algae in another.

Although the observations from the large reserve were

not replicated, these results offer some empirical evi-

dence suggesting that large reserves can provide bio-

logical functions not possible in small reserves. This

conclusion is in stark contrast to the results of this

review, in which even small reserves appeared to have

a positive impact on most biological measures. In order

to assess adequately the role of area in reserve function,

a real need exists for studies that make observations

in reserves of many sizes within the same biogeograph-

ic region.

Success in the design and function of a marine re-

serve is closely tied to the goals of the reserve. For

example, ﬁshery reserves need to increase abundance,

biomass, and organism size within the reserve in order

to sustain the reserve populations as well as supply the

harvested areas. Conservation reserves, on the other

hand, focus more exclusively on the maintenance of

diversity and abundance of organisms within the re-

serve itself. Fortunately, marine reserves appear to lead

to higher values of all of these biological measures,

implying that both goals can be met with the same

reserve.

The impact of marine reserves on the organisms con-

tained within them will never be completely predict-

able. Variation among reserves and a level of uncer-

tainty will always exist when examining how marine

reserves affect speciﬁc biological measures. Goals set

for marine reserves should account for this variation

(Walters and Holling 1990, Clark 1996, Hall 1998,

Lauck et al. 1998). Ultimately, though, it is encour-

aging to know that reserves of any size appear to func-

tion well, in terms of producing higher densities, sizes,

and diversity of organisms.

Inherent problems and necessary caveats

The enormous variation in type and quality of the

observations from marine reserves made it difﬁcult to

compare or analyze the results of the studies I reviewed

(see also Jones et al. 1992). The primary problems

include:

1) results are more likely to be reported for species

that are actually affected by reserves (either positively

or negatively) than for unaffected species, especially

for single-species studies;

2) methodologies often differ drastically among dif-

ferent observations and among scientists within a

study;

3) characteristics of reserves being studied (such as

location, habitat type, current regimes, temperatures,

etc.) are not the same;

4) observations are rarely replicated temporally or

spatially (usually because there is only one reserve

available for study);

February 2003 S129

IMPACT OF MARINE RESERVES

5) reserves are not always adequately protected from

poaching;

6) the length of protection varies among reserves;

7) numbers and types of organisms studied vary be-

tween experiments;

8) the intensity of ﬁshing outside of the reserve may

enhance or even create the perceived affect on biolog-

ical measures of reserve protection.

As many have argued, the intensity of ﬁshing oc-

curring outside a reserve (or where a reserve is before

it becomes a reserve) can have a large impact on the

perceived effects of reserve protection (Polacheck

1990, Russ et al. 1992, Carr and Reed 1993, Rowley

1994, Nowlis and Roberts 1997). If an area is nearly

completely ﬁshed out, the ratio of postprotection to

preprotection values of abundance, biomass, etc. will

be much higher than for an area that had been lightly

ﬁshed (assuming all else is equal, and that new ﬁsh can

be imported to the ﬁshed areas from elsewhere). It is

difﬁcult to compare ﬁshing intensities in different parts

of the world, and this can lead to inaccuracies when

combining data.

The conﬁdence in the results from any one study

depend on the quality and breadth of the sampling in-

volved, and thus can complicate comparisons across

studies. As an example, conclusions drawn when com-

paring results from a single-species study with results

from a study on 250 species suffer obvious comparison

problems. Furthermore, studies that looked at only one

or a few species may have missed how other species

responded to reserve protection; rarely do all species

respond in the same way. Future studies, therefore,

should include at least a few species from all trophic

levels in order to assess reserve effect accurately.

Another problem many studies face is the lack of

consistency in protection level for the reserves. Even

fully protected reserves often suffer some poaching

(e.g., Klima et al. 1986). This potential problem was

rarely quantiﬁed, largely due to difﬁculties in moni-

toring a clandestine act. Because information on actual

protection level is lacking, it is difﬁcult to know exactly

how long and to what degree a reserve has been pro-

tected. Reserve effects can change over time (see Russ

and Alcala 1998

for examples of this), so knowing

the length of time protection has been in place can be

a critical part of analysis. To be able to make more

accurate predictions of the effect of marine reserves,

actual ﬁshing effort within reserves must be measured

and accounted for (Polacheck 1990, Russ et al. 1992,

Carr and Reed 1993, Rowley 1994, Nowlis and Roberts

1997) and the length of complete protection identiﬁed.

The lack of temporal and spatial replication in many

of the studies further complicates interpretation of the

results. Snapshots in time and space can provide clues

to the effects of reserves, but it is very difﬁcult to

eliminate the possibility that observed effects were not

simply a result of spatial or temporal differences, es-

pecially with inside/outside reserve studies. Before/af-

ter studies offer a possible solution to these problems

and should be coupled with control observations in

non-reserve areas over the same time period, across

several spatial scales within a biogeographic region.

However, such studies are often logistically difﬁcult to

implement.

One of the largest problems with the empirical lit-

erature on marine reserve effects is that methodologies

used for different studies and the characteristics of re-

serves and control sites (such as substrate rugosity,

depth, current regime, etc.) differ dramatically. Few

people make efforts to accommodate the problems

mentioned above, let alone measure the same variables

in the same way. For example, sample sizes in many

studies were not large enough to draw statistically sig-

niﬁcant conclusions. Other studies did not report the

statistical signiﬁcance of their results, even though this

might have been possible. Empirical work on marine

reserves needs to reﬂect the rigorous standards of the

rest of the scientiﬁc literature.

Finally, results are often only reported when a re-

serve actually had an effect on an organism, whether

negatively or positively. This was unlikely to be a prob-

lem for studies that looked at entire communities, but

was potentially a large factor inﬂuencing single-species

studies. Single-species studies can often be useful, es-

pecially for ﬁsheries management, but it is important

to remember that not every species will respond to

reserve protection.

Despite these potential sources of error, my analyses

uncovered clear and signiﬁcant positive effects of re-

serve establishment on the organisms dwelling within

reserve boundaries. Even the inclusion of gray litera-

ture, where many of these interpretation problems dis-

cussed above are exacerbated, did not obscure these

results.

ONCLUSIONS

The most important lesson provided by this review

is that marine reserves, regardless of their size, and

with few exceptions, lead to increases in density, bio-

mass, individual size, and diversity in all functional

groups. The diversity of communities and the mean

size of the organisms within a reserve are between 20%

and 30% higher relative to unprotected areas. The den-

sity of organisms is roughly double in reserves, while

the biomass of organisms is nearly triple. These results

are robust despite the many potential sources of error

in the individual studies included in this review.

Equally important is that while small reserves show

positive effects, we cannot and should not rely solely

on small reserves to provide conservation and ﬁshery

services. Proportional increases occur at all reserve siz-

es, but absolute increases in numbers and diversity are

often the main concern. To supply ﬁsheries adequately

and to sustain viable populations of diverse groups of

S130

BENJAMIN S. HALPERN

Ecological Applications

Special Issue

organisms, it is likely that at least some large reserves

will be needed.

Finally, it is paramount that we explicitly state our

goals when creating marine reserves. These goals help

guide the design of reserves and are critical for as-

sessing whether or not a reserve has functioned suc-

cessfully.

CKNOWLEDGMENTS

I thank Bob Warner for the many insightful comments he

offered on drafts of this paper. Thanks also to George Branch,

Callum Roberts, Heather Leslie, Jenny Dugan, Kevin Laf-

ferty, Deborah McArdle, Rodrigo Bustamante, Kim Selkoe,

Kurt Anderson, Steve Palumbi, and two anonymousreviewers

for the helpful comments they provided. This is contribution

number 26 from the Working Group on the Science of Marine

Reserves of the National Center for Ecological Analysis and

Synthesis. NCEAS is funded by NSF, UC–Santa Barbara, and

the State of California.

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APPENDIX

This appendix includes a summary of the data extracted from the literature reviewed, and the sources from where the data came.

Reserve

Size

(km

) No. taxa

Functional group

C H P/I I

Biological measure

D B S Div Reference

Caribbean

St. Lucia 0.026

Roberts and

Hawkins

(1997)

Saba 0.9 40 species

1.9

Polunin and

Roberts

(1993)

Saba 0.9 26 species

1.09

ND ND

Roberts (1995)

Belize 2.6 45 species

1.9

Polunin and

Roberts

(1993)

Los Roques,

Venezuela

4 1 species

2.38

1.17 Weil and

Laughlin

(1984)

Barbados 2.3 89 species

1.16

1.07

1.06 Rakitin and

Kramer

(1996)

Barbados 2.3 7 species

2.15

1.53 Tupper and

Juanes (1999)

Hol Chan,

Belize

2.6

2.21

Roberts and

Polunin

(1993)

Hol Chan,

Belize

2.6 19 ﬁsh fami-

lies, 2 inverts

3333 1

2.1

1.1 Carter and Sed-

berry (1997)

Half Moon

Caye, Be-

lize

39.25 19 ﬁsh fami-

lies, 2 inverts

3333 1

2.07

Carter and Sed-

berry (1997)

Exhuma

Sound,

Bahamas

456 1 species

311

4.19

1.29 Sluka et al.

(1997)

Exhuma

Sound,

Bahamas

456 1 species

5.31 Stoner and Ray

(1996)

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Wallace, S. S. 1999. Evaluating the effects of three forms of

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H. Lessios and I. G.

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Aquatic Sciences 55:917–924.

S134

BENJAMIN S. HALPERN

Ecological Applications

Special Issue

PPENDIX

. Continued.

Reserve

Size

(km

) No. taxa

Functional group

C H P/I I

Biological measure

D B S Div Reference

Manuel An-

tonio,

Costa Rica

6.82 1 species

1.65

1.34 Ortega (1987)

SW Pedro

Bank Ja-

maica

13 families

333 1

1.22

1.76

Koslow et al.

(1998)

Philippines

Sumilon 0.125 102 species

333 1

1.56

1.3 Russ and Alca-

la (1989)

Sumilon 0.125 overall, 4 fami-

lies

2.6

1.73

Russ and Alca-

la (1996)

Sumilon 0.125 102 species

333 1

1.73

Russ (1985)

Sumilon 0.125

33 1

1.51

Alcala (1988)

Sumilon 0.125 178 species

1.4

1.39

1.31 Russ and Alca-

la (1998

)

Sumilon 0.125 178 species

333

Russ and Alca-

la (1998

)

Apo 0.11 overall, 4 fami-

lies

7.1

8.0 Russ and Alca-

la (1996)

Apo 0.11 126 species

333 1

2.73

1.4 White (1988)

Apo 0.11 178 species

1.54

Russ and Alca-

la (1998

)

Apo 0.11 178 species

333

Russ and Alca-

la (1998

)

Apo 0.11

2.73 Clark et al.

(1989)

Pamilican 0.14 126 species

333 1

1.89

1.25 White (1988)

Pamilican 0.14

1.89 Clark et al.

(1989)

Balicasag 0.08 126 species

333 1

1.45

1.03 White (1988)

Balicasag 0.08

1.45 Clark et al.

(1989)

Sumilon

‘‘outside’’

0.375 overall, 4 fami-

lies

5.2

4.1 Russ and Alca-

la (1996)

Sumilon

‘‘outside’’

0.375 178 species

1.8

Russ and Alca-

la (1998

)

Sumilon

‘‘outside’’

0.375 178 species

333

Russ and Alca-

la (1998

)

New Caledonia

Amedee 2.8

4.5

9.5

2.43 Wantiez et al.

(1997)

Signal 4.3

1.35

3.5

1.42 Wantiez et al.

(1997)

Laregnere 8.5

4.29

3.7

1.9 Wantiez et al.

(1997)

Maitre 9

2.71

3.21

1.5 Wantiez et al.

(1997)

Bailly 2.4

2.0

1.44

1.29 Wantiez et al.

(1997)

All ﬁve re-

serves

27 214 species

333 1

1.38

3.47

1.57 Wantiez et al.

(1997)

Fiji

Unnamed 9.4 83 species

333 1 1

Jennings and

Polunin

(1996)

Great Barrier Reef

Lizard Island 9.9 1 species

1.2 Zeller and Russ

(1998)

Boult Reef 3.42 33 species

311

Beinssen

(1989)

Glow and

Yankee

Reefs

25.15 1 species

2.58

Ferreira and

Russ (1995)

Heron Island 12 1 species

3.77

Craik (1981)

Unamed on

GBR

Ayling and

Ayling

(1986) (in

Jones et al.

1992)

February 2003 S135

IMPACT OF MARINE RESERVES

PPENDIX

. Continued.

Reserve

Size

(km

) No. taxa

Functional group

C H P/I I

Biological measure

D B S Div Reference

Red Sea

Ras Moha-

med, Sinai

21.1 45 species

333

(0.85)

(0.66)

ND ND

(0.93)

Roberts and

Polunin

(1992)

Ahkziv 1.5 1 species

Spanier (1994)

(in Childress

1997)

Kenya

Malindi

16.57

1.42 McClanahan

and Muthiga

(1998)

Malindi and

Watuma

333 1

3.58

McClanahan

and Shaﬁr

(1990)

Malindi and

Watuma

10 81 species

algae, coral

331

2.6

27.7 McClanahan

(1997)

Kisite 15 51 species

333

Watson and Or-

mond (1994)

Kisite 15

333 1

1.19

Watson et al.

(1996)

Kisite 15 23 species

Watson et al.

(1997)

Mombasa 10 10 families

others

333 1

2.0

15.5

2.04

2.0 McClanahan

and Kaunda-

Arara (1996)

Malindi, Wa-

tamu, and

Kisite

25 127 species

(0.91)

McClanahan

(1989)

Malindi, Wa-

tamu, and

Kisite

25 118 species

3333 1

2.27

1.92 McClanahan

(1994)

Malindi, Wa-

tamu, Kis-

ite, Mako

Kokwe,

Simam-

bya, Ar-

letts, and

Kiwaiyu

846 188 species

ND ND

Samoilys

(1998)

Southeastern Africa

Mayotte Is-

land

5.25 239 species

333

(0.83)

2.54

(1.01)

Letourneur

(1996)

Cousin Is-

land, Sey-

chelles

1.2 115 species

33 1

1.67

Jennings et al.

(1996)

Sainte Anne 10 115 species

33 1

2.5

Jennings et al.

(1996)

South Africa

De Hoop 230 10 species

3.64

Bennett and

Attwood

(1991)

Dwesa 39 8 species

0.73 Hockey and

Bosman

(1986)

Dwesa 39 1 species

32 1

1.16 Lasiak (1993)

Dwesa 39 1 species

4.5

8.5

1.28 Siegfriend et al.

(1985)

Hluleka 4

0.83 Hockey and

Bosman

(1986)

Isi Laka 7 species

0.74

0.63 Hockey and

Bosman

(1986)

Tsitsikamma 300 2 species

1.12 Buxton (1993)

Tsitsikamma 300 3 species

4.2

1.33 Buxton and

Smalle

(1989)

North America

Naranganset

Bay, RI

1.07 1 species

33 1

2.44

2.0 Rice et al.

(1989)

S136

BENJAMIN S. HALPERN

Ecological Applications

Special Issue

PPENDIX

. Continued.

Reserve

Size

(km

) No. taxa

Functional group

C H P/I I

Biological measure

D B S Div Reference

Hopkins, CA 2.75 10 species

(1.56)

1.21

Paddock and

Estes (

unpub-

lished data

)

Point Lobos,

3.14 10 species

(1.13)

1.26

Paddock and

Estes (

unpub-

lished data

)

Big Creek,

6.78 10 species

(1.23)

ND ND

Paddock and

Estes (

unpub-

lished data

)

Edmonds

Underwa-

ter Park,

0.002 3 species

311

Palsson and Pa-

cunski (1995)

Shady Cove,

1.71 3 species

1.76

Palsson and Pa-

cunski (1995)

Two re-

serves,

1.712 3 species

1.28 Palsson and Pa-

cunski (1995)

Manele, HI 1.25

1.06

1.24

0.96 Grigg (1994)

Kealakakua,

1.28

1.57

4.13

1.02 Grigg (1994)

Huanama,

Honolua,

Manale,

Molokini,

and Kea-

lakakua,

1.35

1.61

1.07 Grigg (1994)

Kennedy

Space

Center, FL

39.6 50 species

333 1

1.51

Johnson et al.

(1999)

Molasses

Reef, FL

0.9 132 species

6.1

0.93 Bohnsack

(1981)

French Reef,

0.37 132 species

1.65

0.93 Bohnsack

(1981)

Looe Key

Reef, FL

15.54 3 families

33 2

0.67

Clark et al.

(1989)

Looe Key

Reef, FL

15.54 1 species

Hunt et al.

(1991) (in

Childress

1997)

Dry Tortu-

gas, FL

190 1 species

4.5 Hunt et al.

(1991) (in

Childress

1997)

Fort Jeffer-

son, FL

19 1 species

1.55 Davis (1997)

‘‘Prison Re-

serve,’’

B.C.

1 species

1.22

1.15 Wallace (1999)

‘‘Ecological

Reserve,’’

B.C

1 species

1.11

(0.99)

Wallace (1999)

Chile

Las Cruces 0.044 2 species

10.63

Castilla and

Duran (1985)

Las Cruces 0.044 1 species

1.96

7.26

1.72 Castilla and

Bustamante

(1989)

Las Cruces 0.044 6 species

31 1

Duran and Cas-

tilla (1989)

Las Cruces 0.044 1 species

Bustamante and

Castilla

(1990)

Las Cruces 0.044 2 species

(0.8)

Oliva and Cas-

tilla (1986)

Las Cruces 0.044 3 species

4.67 Duran et al.

(1987)

Mehuin 0.006 6 species

9.56

Moreno et al.

(1986)

February 2003 S137

IMPACT OF MARINE RESERVES

PPENDIX

. Continued.

Reserve

Size

(km

) No. taxa

Functional group

C H P/I I

Biological measure

D B S Div Reference

Mehuin 0.006 4 species

31 1

Moreno et al.

(1984)

Montemar 0.025 1 species

Bustamante and

Castilla

(1990)

New Zealand

Leigh (Goat

Island)

5.18 12 species

332

0.73

1.41 Cole et al.

(1990)

Leigh (Goat

Island)

5.18 1 species

2.3

1.17 McCormick and

Choat (1987)

Leigh (Goat

Island)

0.55

11.25 Davis (1989)

Leigh (Goat

Island)

0.55 1 species

4.5

13.05

MacDiarmid

and Breen

(1993)

Tasmania

Maria Island 7 117 species

1.29 Edgar and Bar-

rett (1999)

Tinderbox 0.53 117 species

Edgar and Bar-

ret (1999)

Governor Is-

land

0.6 117 species

Edgar and Bar-

rett (1999)

Ninepin 0.59 117 species

Edgar and Bar-

rett (1999)

Spain

Isles Medes 4.18 51 species

333 2

0.55

Garcia-Rubies

and Zabala

(1990)

Isles Medes 4.18 1 species

0.26

0.89 Sala and Zabala

(1996)

Isles Medes 4.18 2 species

ND ND

Sala et al.

(1998

)

France

Banyuls-sur-

Mer

1.5 35 species

333 1

2.06

1.19

1.17 Bell (1983)

Banyuls-sur-

Mer

1.5 41 species

Dufour et al.

(1995)

Cerbere-

Banyuls

6 1 species

Sasal et al.

(1996)

Carry-le-

Rouet

0.85 54 species

33 1

1.78

1.16 Harmelin et al.

(1995)

Carry-le-

Rouet

0.85 47 species

Harmelin

(1992)

Scandola 0.72 26 species

33 1

1.6

2.14

1.8

Francour

(1994)

Scandola 0.72 18 species

33 1

1.37

2.51

1.24 Francour

(1996)

Scandola 0.72 25 species

1.71 Francour

(1991)

Unnamed in

Brittany

1 species

Conan (1986)

Notes:

The summarized information is organized by general region of the globe in which each reserve occurs.The ‘‘outside’’

reserve at Sumilon in the Phillipines refers to the area outside the reserve that received protection at various times (it is

distinct from, but adjacent to, the Sumilon reserve). Data were occasionally reported for groups of reserves; in these cases

the names of all the reserves measured are listed as one entry. The number of taxa studied in each reference gives a general

idea of the breadth of each study. Although the number of species was reported in many of the reviewed studies (and therefore

reported here), changes in biological measures were usually only reported at the taxonomic level of family. Functional group

information describes how I was able to categorize the taxa studied and includes carnivorous ﬁshes (C), herbivorous ﬁshes

(H), planktivorous ﬁshes/invertebrate eaters (P/I), and invertebrates (I). An ‘‘

’’ indicates that data for the functional group

were available from the reference. Overall values were recorded for all cases, when available, and are listed under the

appropriate biological measure column. Trends are reported as

, and

, corresponding to higher values, no difference

in values, or lower values of a measure inside the reserve compared to outside (or after compared to before the creation of

a reserve). In cases where trends were not signiﬁcantly different from each other (

) but ratio values could be calculated,

biological measures are reported as

with the ratio value in parentheses. The biological measures are density (D), biomass

(B), size of the organism (S), and diversity (Div). Blank species indicate that the information was not reported in the reference

and was therefore not available for analyses in this review.

Patterns in abundance, size and space-use of Giant Mud Crab (Scylla serrata) in a temperate marine protected area

Article

Full-text available

May 2024
AQUAT CONSERV

Marine Protected Areas limit fishing to protect a broad range of species and enhance biodiversity. Consequently, closures may not benefit species equally and species-specific assessments are required to determine the impact of closures. Relative abundance and size of Giant Mud Crab (Scylla serrata) was compared across no-take and fished zones in Port Stephens-Great Lakes Marine Park, on the temperate east coast of Australia (32.45°S). In addition, passive acoustic telemetry was used to estimate daily space-use areas. Similar abundances were observed between no-take and fished zones; however certain no-take sites had higher abundances than others. In addition, crabs were 9.9 mm larger in no-take zones on average. Daily crab space-use varied widely (~4 to 1000 m2), and generally increased with water temperature and conductivity. These patterns indicate that recruitment processes interact with marine park protection to shape crab abundances across estuaries. However no-take zoning appears to primarily limit fishing mortality on legal size crabs (i.e., carapace length >85 mm) resulting in larger crabs within no-take zones. This may mean no-take zones enhance reproductive output of crab populations since larger individuals are likely to be more fecund.

Evaluating the influence of marine protected areas on surf zone fish

Article

May 2024
CONSERV BIOL

Article impact statement: Marine protected area effects on surf zone fish vary by region, monitoring method, and taxa. Abstract Marine protected areas (MPAs) globally serve conservation and fisheries management goals, generating positive effects in some marine ecosystems. Surf zones and sandy beaches, critical ecotones bridging land and sea, play a pivotal role in the life cycles of numerous fish species and serve as prime areas for subsistence and recreational fishing. Despite their significance, these areas remain understudied when evaluating the effects of MPAs. We compared surf zone fish assemblages inside and outside MPAs across 3 bioregions in California (USA). Using seines and baited remote underwater videos (BRUVs), we found differences in surf zone fish inside and outside MPAs in one region. Inside south region MPAs, we observed higher abundance (Tukey's honest significant difference [HSD] = 0.83, p = 0.0001) and richness (HSD = 0.22, p = 0.0001) in BRUVs and greater biomass (HSD = 0.32, p = 0.0002) in seine surveys compared with reference sites. Selected live-bearing, fished taxa were positively affected by MPAs. Elasmobranchs displayed greater abundance in BRUV surveys and higher biomass in seine surveys inside south region MPAs (HSD = 0.35, p = 0.0003 and HSD = 0.23, p = 0.008, respectively). Although we observed no overall MPA signal for Embiotocidae, abundances of juvenile and large adult barred surfperch (Amphistichus argenteus), the most abundant fished species, were higher inside MPAs (K-S test D = 0.19, p < 0.0001). Influence of habitat characteristics on MPA performance indicated surf zone width was positively associated with fish abundance and biomass but negatively associated with richness. The south region had the largest positive effect size on all MPA performance metrics. Our findings underscored the variability in species richness and composition across regions and survey methods that significantly affected differences observed inside and outside MPAs. A comprehensive assessment of MPA performance should consider specific taxa, their distribution, and the effects of habitat factors and geography.

A diverse portfolio of marine protected areas can better advance global conservation and equity

Article

Full-text available

Feb 2024
P NATL ACAD SCI USA

Marine protected areas (MPAs) are widely used for ocean conservation, yet the relative impacts of various types of MPAs are poorly understood. We estimated impacts on fish biomass from no-take and multiple-use (fished) MPAs, employing a rigorous matched counterfactual design with a global dataset of >14,000 surveys in and around 216 MPAs. Both no-take and multiple-use MPAs generated positive conservation outcomes relative to no protection (58.2% and 12.6% fish biomass increases, respectively), with smaller estimated differences between the two MPA types when controlling for additional confounding factors (8.3% increase). Relative performance depended on context and management: no-take MPAs performed better in areas of high human pressure but similar to multiple-use in remote locations. Multiple-use MPA performance was low in high-pressure areas but improved significantly with better management, producing similar outcomes to no-take MPAs when adequately staffed and appropriate use regulations were applied. For priority conservation areas where no-take restrictions are not possible or ethical, our findings show that a portfolio of well-designed and well-managed multiple-use MPAs represents a viable and potentially equitable pathway to advance local and global conservation.

Marine protection enhances the resilience of biological communities on temperate rocky reefs

Article

Full-text available

Mar 2024
AQUAT CONSERV

Conservation science faces the urgent challenge of halting the biodiversity loss caused by the biological crisis of the present era. To achieve this, conservation science requires cutting‐edge tools to focus on vital properties of ecosystems, such as the resilience. Resilience informs about the cost of recovering biological communities. Here, we developed a metric to quantify the ecological assemblage recovery cost based on the dissimilarity between unprotected and partially protected communities compared with totally protected communities in Cabo de Gata Marine Reserve. Our results show that the biological assemblage composed of fish, macroinvertebrates and cryptic fish, and macroalgae species in unprotected zones requires a higher ecological recovery cost than in partially protected zones when moving towards a fully protected community. This research contributes to monitoring marine the effectiveness of marine protection from a resilience perspective, with the goal of promoting the use of the recovery cost metric for building resilient coastal ecosystems.

Intertidal gleaning fisheries: Recognising local-scale contributions and management scenarios

Article

Full-text available

Apr 2024
MAR POLICY

Intertidal gleaning is a widespread means through which women participate in the fishery harvest sector. However, the fishery is often under recognised in management and policy-making. Accordingly, there is a need to further our understanding of the fishery, and how local factors may help or hinder effective management. This study focuses on Zanzibar, Tanzania, using focus group discussions (FGDs) and interviews to investigate local-scale contributions from gleaning in seagrass dominated areas-which are particularly frequented gleaning grounds locally, and more widely in the Indo-Pacific region. The study also gathered insight into how gleaners perceived different management scenarios used elsewhere within the small-scale fishery sector. Despite being typically viewed as a sustenance means, gleaning was found to be primarily an economic activity, mainly through catching the bivalve, Anadara antiquata, and commercial gastropod species (Chicoreus ramosus and Pleuroploca spp). FGD respondents held positive preconceived ideas about rotating no-take zone scenarios as a management strategy, as well as indicating preferences for community-based measures. In order for no-take zones to have a higher chance of success, further investigation is needed to understand the life histories of commonly gleaned species in order to inform rotation periods, as well as developing means of cross-community cooperation due to the shared, open access nature of intertidal zones. These results demonstrate the economic importance of gleaning for coastal women in Zanzibar, who have invaluable insights, built on lived experience and local knowledge, which could enable and benefit a more inclusive management system.

A synthesis of socioeconomic and sociocultural indicators for assessing the impacts of offshore renewable energy on fishery participants and fishing communities

Article

Full-text available

Feb 2024
MAR POLICY

Offshore renewable energy, particularly wind farms, is rapidly expanding globally and has become an essential component of many coastal nations' decarbonization plans, including the United States. The addition of these physical structures to the marine space may impact fish production and may preclude fishers from traditional fishing grounds-both of which have the potential to affect fisheries outcomes. Understanding the socioeconomic and sociocultural impacts of implementing offshore wind is crucial to determining appropriate mitigation strategies and to developing data collection, monitoring, and adaptive management strategies. This review synthesizes quantitative and qualitative indicators that have been used to assess the impact of fisheries pre-clusion and shifts in fished species' biomass on fishery participants. By providing a description of the indicator, a list of the datasets required to calculate its value, and a list of studies that used the indicator, this review can serve as a guide to those designing monitoring plans to determine socioeconomic and sociocultural offshore wind impacts.

Is a recent large expansion of a no-take reserve sufficient to change the reef fish assemblage? A before-after assessment in Alcatrazes Wildlife Refuge, Southwestern Atlantic

Article

Apr 2024
OCEAN COAST MANAGE

Marine protected areas (MPAs) have been established with the aim of preserving and recovering marine envi- ronments, as well as managing fisheries activities. Some features of MPAs can enhance conservation goals, such as being completely no-take, well-enforced, large, old and isolated. The no-take area in the Alcatrazes Archi- pelago, southwestern Atlantic, was recently expanded from four separate small areas of 3 km2 (totalling 12.5 km2) established in 1987, to a large continuous no-take reserve (NTR) of 675 km2 established in August 2016, allowing tourism activities. In this study, the aim was to detect recent changes in the reef fish assemblage following the expansion of the NTR using visual census samples in specific sites around the main island. The surveys were conducted before (2015–2016; n = 230 censuses) and after (2019–2020; n = 320 censuses) the expansion of the NTR. Generalized additive mixed models were fitted to predict fish richness, functional richness, abundance and biomass, considering factors like depth, year and specific sites. The most parsimonious models for mean richness, functional richness, abundance and biomass all included a negative relationship with protection after the expansion, but with an increase of unique species and unique functional entities. Beta diversity values between sites decreased after the expansion with a smaller contribution of nestedness, which indicates a greater sharing of species among the reef areas around the main island. We raised the hypothesis that the decreases in fish fauna metrics could be attributed to several factors: (1) the recency of the NTR expansion, making it difficult to detect the benefits of protection in this short time frame (i.e., less than five years); (2) the type of habitat protected after the expansion, which included mostly sandy bottoms, possibly not promoting connectivity; and (3) the presence of recreational divers in the recently protected area hampering the detection of fish due to possible changes in fish behaviour (mainly for large species with commercial use). By studying one of the largest southwestern Atlantic no-take MPAs, we add evidence that area increment alone is not enough to optimize the protection of marine biodiversity within a short time scale and continuous ecological monitoring is essential for adaptive management, especially in the early stages of MPAs.

Are Differing Viewpoints Amongst Key Actors Influencing Implementation of Key Eu Marine Environmental Policies? Case Of Strictly Protected Areas

Article

Full-text available

Jan 2024

Sašo Gorjanc

The transboundary nature of marine ecosystems and their more difficult accessibility create challenges for the conceptualisation of effective marine conservation, because of the complexity of the marine functioning and often unclear competences. Marine conservation thus often relies on (international) policies. The EU environmental policies are known for their high ambition levels. However, their implementation has been subpar so far. This study investigates the viewpoints of marine nature, wilderness, and strict protection in the EU seas and whether those help explain why the implementation of EU marine environmental policies has been incoherent and uncoordinated so far. The viewpoints and nature imaginaries were investigated amongst key actors in policy implementation from national to the EU and Regional Sea Conventions levels, using policy analysis, diagramming, and Living Q workshops. The results show a variety of divergent viewpoints that frame marine issues in different ways, resulting in different interpretations of common policies and definitions, as well as a variety of policy implementation priorities. The variety of different values associated with marine nature, wilderness, and the role of EU policies is thus likely to influence the way common EU policies will be implemented in the future and by extension their effectiveness.

Experimental Investigation of a New Wake Monitoring Method Based on Underwater Thermal Tactile

Article

May 2024

The intrusions of unauthorized underwater vehicles and ships have a negative impact on marine protected areas. Therefore, it is necessary to develop monitoring methods to reduce the occurrence of illegal intrusions. This research creatively proposes a thermal tactile wake sensing method based on the micro-thermoelectric generator for monitoring the wake of underwater moving objects. The wake monitoring theory model based on the mechanism of the thermoelectric generator is established, and a sensor prototype is designed. Experimental studies are conducted in specific orientations to verify the feasibility of this method in identifying the orientation of underwater moving objects. The experimental results indicate that when the underwater propeller passes by the prototype, the conclusion drawn from comparing the output voltages of the thermal tactile units on different surfaces of the prototype aligns with the theoretical model. In addition, a comparative experiment between the propeller and fish is conducted. The experimental results show that when the propeller speed is 200 r/min and the forward velocity is 0.1 m/s, the prototype can distinguish between the wakes of the above two types of underwater moving objects within 20–30 s. By combining the results of both types of experiments, it is demonstrated that this method can identify the orientation of underwater moving objects by sensing their wakes while excluding interference from the wakes of fish. The thermotactic wake sensing method proposed in this research has great potential for application in marine protected areas.

An initial fish and megafauna biomass assessment from Tanjung Bira, a remote unprotected marine area

Article

Feb 2024

Indonesia is a part of the Coral Triangle, the global epicenter of marine biodiversity. As an island nation, fisheries are amongst the main sources of income for Indonesia’s economy, but overfishing has depleted fish stocks and degraded habitats, especially in unprotected marine areas. Tanjung Bira in South Sulawesi is an unprotected marine area that possesses understudied marine biodiversity and overlooked potential for sustainable tourism. Currently, research has only been done in a small area in Liukang Loe island, but we hypothesize that the habitats surrounding Bira East, Bira West, and Kambing Island also harbor significant levels of marine biodiversity. In this study, we utilized a standardized citizen science effort to investigate the occurrence and to quantify the biomass of specific fish families (Lutjanidae, Serranidae, Carangidae, Scombridae, Sphyraenidae, Lethrinidae, and Scaridae), key fish species (large and vulnerable piscivores), sea turtles, elasmobranchs, and other megafauna in Tanjung Bira and its surrounding area. We discuss the species assemblages, their potential ecological roles, threats, and proposed management strategies for each region to foster coexistence between conservation and community livelihood. Implementing a measure of protection is imperative to ensure the conservation of reef ecosystems, commercially important fishes, vulnerable elasmobranchs, charismatic megafauna and nationally protected species such as humphead wrasse and sea turtles.

Queen conch, Strombus gigas, in fished and unfished locations of the Bahamas: effects of a marine fishery reserve on adults, juveniles, and larval production

Article

Full-text available

Jan 1996
FISH B-NOAA

Marine fishery reserves (MFRs) have been set aside in coastal areas throughout the world with the hope of reversing population decreases commonly observed in many marine resources. In this study, a comparison of population structure of the commercially important gastropod Strombus gigas, queen conch, was made between a fished area and an MFR in the Exuma Cays, central Bahamas. There were 31 times more adult conch on the shallow (<5 m) Great Bahama Bank i n the MFR, and in a survey at 7 depth intervals (to 30 m) on the island shelf in the Exuma Sound, mean adult density was always higher in the MFR, by as much as 15 times. Shell length and lip-thick-n e w measurements indicated t h a t adults in the MFR migrate with age from bank nursery sites into deeper sound water, whereas those on the bank in the fished area were harvested before reaching water sufficiently deep to protect them from free-diving fisher-men. Although sparsely distributed juveniles in shallow-water (<15 m) habitats of the sound were the primary source of adults in the fished area, large juvenile aggregations on the bank also contributed to the deep-water adult stock in the MFR. Total larval densities in the MFR were frequently a n order of magnitude higher than those found in the fished area, and densities of late-stage larvae were 4 to 17 times higher. Because the surface current along the Exuma Cays shelf flows to the northwest, late-stage larvae found inside the reserve must have been spawned outside the reserve; thus the high densities of juvenile and adult conch are the result of natural accumulation of larvae in the area, as well as the result of protection from fishing. Although the fate of larvae dispersed from the reserve is uncertain, it is likely that high numbers of reproductive stock and larvae in the reserve have a significant positive effect on 3 4 * I populations in the northern Exuma Sound. Designs of reserves that consider ontogenetic requirements of the target species and strategic locations for larval production, import, export, and metapopulation dynamics will optimize fishery benefits for the many marine vertebrate and invertebrate species that possess pelagic larvae. I i)

Abundance and species richness of coral reef fish on the Kenyan coast: The effects of protective management and fishing

Article

Full-text available

Jan 1988

Melita Samoilys

Marine and Coastal Protected Areas: A Guide for Planners and Managers

Article

Full-text available

Jan 1984

Maintenance and recovery of reef fishery productivity

Chapter

Full-text available

Jan 1996

James A. Bohnsack

Non-conventional methods to maintain and restore reef fishery productivity include protecting fishery habitats, hatchery releases, artificial reefs, introduction of exotic species, habitat restoration and marine fishery reserves. I conclude that it is far better to prevent overfishing and stock collapse in the first place than to have to rebuild fishery productivity later. The most important strategies to prevent loss of fishery productivity are switching to less destructive fishing methods, preventing destruction of fishery habitats and protecting some areas by establishment of marine fishery reserves. If fisheries must be rebuilt, habitat restoration and marine reserves appear to be the more promising alternatives over the long term. Except for unique circumstances, deployment of artificial reefs and release of hatchery-raised organisms have less potential for retrieving lost fishery productivity. Because of unpredictable consequences and the general inability to correct mistakes, the introduction of exotic organisms is the least favoured alternative for rebuilding fishery productivity.

YEAR AROUND CLOSED AREAS AS A MANAGEMENT TOOL

Article

Jun 1990
NAT RESOUR MODEL

Tom Polacheck

Year around closed areas or refuges as management mechanisms for controlling fishing mortality are explored using a two‐component, spatial model with movement between areas. The model assesses the fate of a cohort when only a portion of it is vulnerable to fishing. The yield per recruit and spawning stock biomass per recruit are compared for equivalent amounts of fishing effort with and without a refuge. The results indicate that the institution of a closed area can lead to substantial increases in spawning stock biomass realized from a cohort and, as such, could be a viable short‐term management option to reduce overall fishing mortality on an overexploited stock. Yield per recruit with a refuge is a complex function of the size of the refuge, fishing mortality rates and movement rates. The results suggest that the proportional loss in yield per recruit will be less than the initial proportion of the cohort contained within the refuge. In some instances, the yield per recruit with a refuge can exceed the yield per recruit without one, but the net increases are usually small. The size of the refuge needed to achieve a specified gain in spawning biomass depends upon the mobility of the fish. Higher movement rates require a larger refuge to achieve the same increase, but any loss in yield per recruit will be less even though the refuge is larger. The assumptions underlying the model are discussed, and the importance of information on movement rates for assessing the possible effect of closed areas is stressed.

Effects of total fishing prohibition on the rocky fish assemblages of Medes Islands marine reserve (NW Mediterranean)

Article

Jan 1990

The Theory of Island Biogeography

Article

Jan 1967

This book had its origin when, about five years ago, an ecologist (MacArthur) and a taxonomist and zoogeographer (Wilson) began a dialogue about common interests in biogeography. The ideas and the language of the two specialties seemed initially so different as to cast doubt on the usefulness of the endeavor. But we had faith in the ultimate unity of population biology, and this book is the result. Now we both call ourselves biogeographers and are unable to see any real distinction between biogeography and ecology.

The Theory of Island Biogeography

Article

Jan 1967

Réponses des peuplements et populations de poissons aux réserves marines: Le cas de l'île de Mayotte, Océan Indien occidental

Article

Jan 1996

Yves Letourneur

This study investigates the effects of establishment of a marine reserve on the coral reef fish communities at Mayotte Island, Western Indian Ocean, after three years of protection. Both total species richness and global abundance did not differ significantly between protected and non-protected areas. Nevertheless, there were significant differences for numerous families and species. Most of the big carnivorous fishes (Serranidae, Lutjanidae, Lethrinidae) were more diverse and more abundant in the marine reserve. Conversely, other fishes, mainly in the families Pomacentridae, Scaridae and Acanthuridae, presented the opposite pattern. The mean biomass of commercial fish species was significantly higher in the reserve (202 g.m-2) than in non-protected areas (79 g.m-2). This pattern was also evident for carnivorous fishes, such as Epinephelus microdon, and semi-pelagic fishes, such as Caesionidae. In contrast, other commercial species, such as Scarus caudovittatus and Acanthurus nigricauda had higher biomass in non-protected areas. Despite this apparent contradiction, our results seem to be linked with the marine reserve protection. Cessation of fishing activities in the reserve may have caused increases in diversity, abundance and biomass of large carnivores. The decrease in the number of these fishes in non-protected areas due to fishing may favour development of other populations, dominated by potential prey for carnivorous fishes.

Underwater survey of coral trout Plectropomus leopardus (Serranidae) populations in the Capricornia section of the Great Barrier Reef Marine Park

Article

Jan 1981

G.J.S. Craik

The impact of marine reserves: Do reserves work and does reserve size matter?

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