Coral Reef Sanctuaries for Trochus Shells

GERALD A. HESLINGA, OBICHANG ORAK, and MARCUS NGIRAMENGIOR

Introduction

Economically, the coral reef snailTrochus niloticus (Fig. 1) is the mostimportant gastropod mollusk in thetropical Indo-West Pacific (Heslingaand Hillmann, 1981; Heslinga, 1981a).Commercial trochus fisheries exist inNew Caledonia, Indonesia, PapuaNew Guinea, Australia, Vanuatu, Fiji,French Polynesia, the Philippines, andin the Marshall, Mariana, Caroline,and Solomon Islands (Wells, 1981a).Subsistence fisheries for trochus shellsand meat exist in many other islandareas.

The meat is edible and is dried,cooked, or occasionally canned forlocal consumption. The aragonite

shells, primary raw material formother-of-pearl buttons, are exportedto Asia and Europe. The annual worldharvest is about 5,000 t (Heslinga andHillmann, 1981) with a dockside valueof about $4 million (at $0.88/kg,Palau's 1982 price). The retail value ofthe finished product is many timeshigher, since an individual trochus

The authors are with the MicronesianMariculture Demonstration Center, Box 359,Koror, Republic of Palau 96940. Views oropinions expressed or implied are those of theauthors and do not necessarily represent the posi­tion of the National Marine Fisheries Service,NOAA.

shell worth $0.15 ex-vessel will make35 buttons worth about $0.30 each atretail (Udui and Van den Andel, 1981).

Contrary to popular opinion, thewidespread use of plastic buttons andother fastening devices has notdepressed the world trochus market.Annual demand has been estimated at6,000 t worldwide (Bouchet and Bour,1980), and the dockside price oftrochus shell has increased 500 percentduring the last decade (Heslinga andHillmann, 1981). The Pacific Islandtrochus industry remains a principalsource of foreign exchange for ar­tisanal fishermen, particularly in

ABSTRACT- Trochus niloticus is ex­ploited throughout the tropical Indo- WestPacific as a source offood and mother-of­pearl. In the Republic of Palau, trochussanctuaries were established in 1960 to serveas centers ofbreeding and planktonic larvaldistribution. However, 1982 field surveysindicated that Koror State sanctuariesaveraged only halfas many trochus as adja­cent exploited areas. In addition, sanc­tuaries were too numerous and widely scat­tered to be effectively patrolled. Recom­mendations to consolidate and relocate thesanctuaries in superior trochus habitatswere approved and implemented by KororState officials before the 1982 trochusseason opened.

We conclude that marine sanctuaries cancontribute to trochus conservation effortsand are of potential economic benefit ifproperly sited and patrolled. Guidelines aresuggestedfor sanctuary selection and assess­ment of trochus distribution and abun­dance. Population densities are shown to beinfluenced by reeforientation, degree ofex­posure to surf, substrate type, and waterdepth.

46(4),1984

Figure 1. - Adult commercial topsheU, Trochus niloticus, 10.2 cm basediameter.

73

remote areas. According toGlucksman and Lindholm (1982), whostudied the commercial shell industryof Papua New Guinea:

"The importance of the shell tradeto the coastal villager or to the nationcannot be measured solely in terms ofcash earnings or Gross National Prod­uct. It is an industry ideally suited tocoastal villages in that: The harvest ofthe shell does not require investmentin expensive equipment or vessels; thereefs on which it is found are oftencontiguous with small population cen­tres (a villager need not leave home toenter the cash economy); the saleableproduct requires no preservation andis easily packed and stored; and themeat (foot) of the snail is easily pro­cessed (salted and/or smoked) to pro­vide a source of locally produced andpreserved high quality protein."

Trochus depletion through unregu­lated or poorly regulated harvesting isof increasing concern in the Indo­West Pacific. Heslinga and Hillmann(1981) cite many cases where localstocks have been fished nearly to eco­nomic extinction, often in spite ofregulatory measures. And, the Inter­national Union for the Conservationof Nature has recently added T. ni/o­ticus to its list of "commerciallythreatened invertebrates" (lUCN, Inpress).

Factors contributing to such de­clines include the large size, accessiblehabitat, and sedentary habit of T.ni/oticus. Complicating factors in­clude a suite of problems commonlyassociated with resource managementin developing countries. Examinationof trochus management in the Repub­lic of Palau, and documentation of asuccessful review and policy change inthis paper is therefore both timely andrelevant.

Since 1960, Palau's trochus man­agement policy has included fourcomponents: I) Size limit (7.6 cm basediameter); 2) restricted season (1month/year, usually June); 3) a sanc­tuary system to protect designatedareas; and 4) a moratorium system inwhich states or villages voluntarily

74

stop collecting shells for one or moreyears. The moratorium system was in­voked by Kyangle State in 1979, An­gaur and Ngeremlengui States in 1980,and Koror, Kyangle, and PeleliuStates in 1983.

The size limit and the seasonal re­striction were originally implementedin the 1920's and 1930's during theJapanese occupation of Palau (Gailand Devambez, 1958). The sanctuarysystem was established under theAmerican administration following a2.5-year investigation by McGowan(1956, 1958, 1959).

McGowan (1956, 1958) presenteddata to support his position that "therehas been a constant decline in the sizeof the catch from almost all of thetrochus producing areas of the Pa­cific." He maintained that these de­clines occurred despite existing regula­tions on harvest and size. As for thedecline in trochus harvests reported atvarious times from New Caledonia,the Philippines, the Andaman Islands,Yap, and Palau, McGowan (1959)concluded that "without a doubt,overfishing was the cause for thesepopulation declines, thus implyingthat the existing conservation prac­tices were ineffective."

A trochus sanctuary system pro­posed by McGowan (1958), and laterimplemented in Palau, Truk, Ponape,and Yap, was based on the assump­tion that the protected areas wouldserve as spawning centers from whichplanktonic larvae would be distributedby currents up and down the reef. Al­though the early life history stages ofT. ni/oticus had not been describedduring McGowan's studies, he hypo­thesized that trochus larvae mustspend a short time in the plankton(days, as opposed to weeks or months)before settlement and metamorphosis(McGowan, 1958). Subsequent stud­ies (Heslinga, 1981a,b; Heslinga andHillmann, 1981) have corroboratedMcGowan's thesis.

T. ni/oticus larvae are now knownto be of the short term lecithotropictype which, under favorable condi­tions, spend only a few days in theplankton. There is a high probabilitythat trochus larvae which recruit suc-

cessfully to the benthic environmentdo so within a few days drift of theirpoint of origin. From a practicalstandpoint, this means that larvaeproduced in trochus sanctuaries prob­ably do help populate nearby reefs.One would not necessarily expect thesame to be true for gastropods withlong-term planktotrophic larvae. Inretrospect, the trochus sanctuary con­cept appears to have had a sound bio­logical basis, in addition to obviousintuitive appeal.

At the outset of Palau's trochussanctuary program, McGowan (1958)recommended establishing one sanc­tuary per 5 miles of barrier reef. Thiswas evidently an arbitrary decision. Itwas stressed that to be effective, thesanctuaries must be "well made," i.e.,placed in appropriate habitats forTrochus ni/oticus, and they must bepatrolled regularly during the harvestseason to discourage poaching. Subse­quently, trochus sanctuaries wereestablished in Palau by members ofthe local Conservation Division. I InKoror, the most populous state andthe largest in terms of barrier reefperimeter, seven trochus sanctuarieswere designated: Five on the east coastand two on the west coast (Fig. 2, 3).

At the request of the Palau MarineResources Division, and with financialsupport from the Pacific FisheriesDevelopment Foundation, we studiedthe original seven Koror State trochussanctuaries in March-April 1982 to seeif they were fulfilling their intendedfunction. Underwater surveys provid­ed a quantitative assessment of thedistribution and abundance of har­vestable trochus in sanctuary areasand in adjacent exploited areas.Another goal was to train PalauanMarine Resources Division personnel(Orak and Ngiramengior) to conductand interpret quantitative fieldassessments of local trochus popula­tions. The sampling techniques, meth­ods of data analysis, and report for­mat used for the Koror State trochussurvey thus represent an attempt to

'Madraisau, B. 1981. Micronesian MaricultureDemonstration Center, Koror, Palau. Pers.commun.

Marine Fisheries Review

Figure 3. - Koror State eastern barrier reef complex, with numberedTrochus niloticus survey sites. A, Koror Island; B, Malakal Island,site of the MMDC Laboratory; C, Auluptagel Island; D, NgederrakReef, site of present trochus sanctuary; E, Augupelu Reef; F, Koror­Airai State boundary; G, Urukthapel Island; H, Ikedelukes Reef, siteof present trochus sanctuary; J, Ell Malk Island; K, Denges passage(marks Koror-Peleliu State boundary). Sites 2, 7, 8, 9, and 15 areformer trochus sanctuaries.

~ PHILIPPINES ~~

.:l\lI ';to EJ PALAU

Kayangell.!{) N

I"-

AUSTRALIA

V

~N

j14

Figure 2. - The Palau archipelago, showingthe 16 sites on the Koror State barrier reefsurveyed for Trochus ni/oticus. Sites II and14 on the western barrier reef are formertrochus sanctuaries.

15 'I'9

'"'tf-''\'"2

KOROR STATE

develop a pragmatic model that can beused for future surveys of this kind,both in Koror and elsewhere.

Methods

We surveyed 16 outer reef sites, 7within existing trochus sanctuariesand 9 in exploited areas, generallywithin 2 km of the sanctuaries (Fig. 2,

46(4),1984

3). At each site a 100 m lead coretransect line was placed on thesubstrate (approximately parallel tothe reef margin) along four depthcontours at 7, 5, 3, and 1 m. Thesedepths were chosen because theycover the ranges commonly accessibleto free diving trochus fishermen. InPalau and elsewhere, most trochus

are harvested between I and 5 mdepth.

Two scuba divers carefully searchedthe substrate along each depth con­tour and recorded all T. niloticuswithin 2 m of each side of the transectline. About 400 m2 of substrate weresurveyed at each depth contour and1,600 m2 were covered at each of the

75

Figure 4. - Relationship betweendepth and mean density ofTrochus niloticus on the seawardbarrier reefs of Koror State. Asignificant negative correlation (r= -0.99; p < 0.01) betweendepth and density was found be­tween 1 and 7 m depth in ex­ploited area. A, exploited areas;8, sanctuaries.

U.S. Geological Survey Maps (Re­public of Palau; scale I: 10,(00).

Results

Trochus niloticus abundance anddistribution data at 16 Koror Statesites are presented in Table I. Den­sities ranged from 0 to 750animals/hectare, with an overallmean of 119.

Table 2 compares trochus densitiesin sanctuary and exploited areas.Although there was high within­contour variance in both categories,sanctuary sites had significantly lowertrochus densities than exploited areasat the I and 3 m contours. Onaverage, sanctuary sites had only halfas many trochus as exploited sites.

Figure 4 indicates the existence of asignificant negative correlation be­tween water depth and trochus densi­ty in exploited sites. Shallow sites hadlarger numbers of relatively smallanimals. As depth increased fewertrochus were found but their meansize was larger. A similar trend in size

MODE

DEPTH 7M

'0

o 2 4 6 8 10 12SIZE (eMl

Figure 5. - Size-frequency distribu­tions of Trochus niloticus at fourdepth contours on the seaward bar­rier reefs of Koror State, 1982. Datawere pooled from 16 sites covering25,600 m2 • Modal size (arrows) in­creased with depth while densitydecreased with depth. Sample sizesat the 7,5,3, and 1 m contours were19, 70, 91, and 136, respectively.

zonation has been reported fortrochus populations at Guam (Smith,1979) and elsewhere (Moorhouse,1932; Rao, 1937); however, the depth­density correlation found in Palau hasnot been reported previously. In NewCaledonia, maximum trochus den­sities are said to occur in the boulderzone of shallow reef flats (Bour andGohin, 1982).

Despite considerable searching wefound no small (< 20 mm) T.niloticus juveniles in the subtidal con­tours surveyed. Young T. niloticusappear to settle exclusively in outerreef flat intertidal areas and migrateinto deeper water as they grow (Hesl­inga, 1981b).

The relationship between depth andsize of T. niloticus is evident whensize-frequency histograms are plottedfor subpopulations at successivedepth contours (Fig. 5). Clearly, deep­water populations have higher percen-

A

1 357DEPTH (Ml

o

300

100>­t:V)zwo

wcz::<l:I­UW

I 200

"cz::Wm~::JZ

sites shown in Figure 2. Divers usedmeasuring boards fitted with under­water paper to record the number andsize of specimens in the followingcategories:

Data on dead T. niloticus shells,hermit crabs, and T. pyramis werecollected for an ancillary study onpredation and competition. The de­sign of this study thus allows quanti­tative data to be collected simultane­ously on a variety of species or phe­nomena.

The time required for searchingeach 100 m transect was about 15minutes/diver, and about 2 man­hours of underwater search effortwere expended at each site. The sur­veys were deliberately conducted dur­ing Palau's calmest months to takeadvantage of the lull between north­east trade winds and southwest mon­soons. We doubt that transect-typetrochus surveys can be conducted ac­curately or safely in shallow water ifsurf heights exceed I m. Nash (1981)reached a similar conclusion. Al­though surveys in our study were con­ducted on different days of the lunarmonth (hence at different tidal levels),the effect on accuracy of the stateddepth contours is minimal since themean tidal range in Palau is only I m.

Locations of the surveyed sites weredetermined from U.S. Defense Map­ping Agency Chart No. 8841 (PalauIslands; scale I:I65,(00) and from

I) Depth,2) compass orientation of reef mar-

gin (N, S, E, W, etc.),3) degree of wave exposure,4) bottom slope, and5) substrate type and composition.

I) Live T. niloticus,2) dead T. niloticus with empty

shells,3) dead T. niloticus occupied by the

hermit crab Dardanus megistos,4) dead T. niloticus occupied by the

crab D. lagopodes, and5) live T. pyramis.

In addition, notes were made re­garding the following habitat charac­teristics:

76 Marine Fisheries Review

Table 1.-Commercial Trochus nilolicus stock densilies in Korar Stale survey areas, March·ApriI1982.

tages of relatively large specimens.The modal size of T. ni/oticus in the 7

m and 5 m contours was 86-90 mm,and this decreased to 76-80 mm at the

Numberof trochus Maximumper quadrat size (mm)

No

Yes (p<0.1)

Yes (p<O.05)

Significantdifference?

153

25785

200 379

255

Depth Densitycontour(m) Sanctuary Exploited

3

Table 2.-Comparison 01 commercial TlOChus nilolicusdensities in sanctuaries and exploited areas, Koror Slale,1982. Densities alll expmssed in mean number per heclalll.Exploited alllas had significantly higher (T·lest of means)trochus densities than sanctuaries al lhe 1 and 3 m con·tours. Sites wIlelll no trochus weill found weill excludedfrom the analysis.

I m contour. If it is assumed thatthe depth-density correlation inFigure 4a is roughly linear, we canpredict that trochus density would ap­proach zero at about 8 m. Thisprediction agrees well with our fieldobservations, and supports the posi­tion of McGowan (1958) that thereare no "large, untapped reserves oftrochus in deeper water."

In addition to being correlated withdepth, trochus densities in the areassurveyed were dependent on reeforientation (Fig. 6). On individualeast-coast reefs (Ngederrak,Ikedelukes, and Pelugauar) there wasa general trend of decreasing densityalong a gradient running clockwisefrom northeast to south. In nearly allcases the south and southeast facingreef sections supported fewer trochusthan nearby east or northeast facingsections. The south and southeast fac­ing reef sections were calmer sites,consistently characterized by a sand­ier, more heterogeneous substratethan the exposed north and northeastfacing sections. These latter areaswere high energy zones whichdisplayed a more consolidated sub­strate with broad patches of pave­ment, coralline algae, and lowfilamentous algae. Live coral coverwas uniformly lower in the shallowcontours of the high energy sites.

Spot checks of shallow subtidalzones on the lagoonward (west­facing) side of the surveyed reefsrevealed broad sandy patches, occa­sional live coral heads, and a totalabsence of T. ni/oticus. All these

19

o

81

31

o

44

13

89

231

400

131

256

119

150

312

325

150175150

50

50225

50150

25350500725

o325225750

o50

500375

257550

175

100375175375

25o

25225

25100

50o

5025ooooo

50

257525ooooooooo

257525oo

50350200

248085

82737164

92868083

78

898883

858880

7271

938781

8682

101

1011069264

96868776

100938781

78

8682

101

85101

Density byMean size depth (no. Mean site

(mm) per hectare) density

7286

859183

109103106

116119101

79

1031029586

100106101113

10310298

82

8695

101

8695

101

24101110

82777482

103100103100

78

89101

131oo2

148

142o21ooooo2

131ooooooooo

6762

2926

1142029

o139

30

o1

2015

1327

415

715

1o19

7531

7531

7531

7531

7531

7531

7531

7531

7531

7531

7531

7531

7531

7531

7531

Depth(m)

S

S

E

W

SE

SE

SE

NE

ESE

SSE

SSE

ENE

ENE

SSW

WNW

WNW

Exposure

4/19

4/02

3118

4/06

4/13

4122

4/20

4/13

4/06

3118

3130

3130

4122

4108

4/08

4/19

Datesurveyed

7'

2'

4

5

3

6

9'

8'

11'

16

15'

14'

10

13

12

Site

I Former sanctuary site. 45 55 No

46(4),1984 77

400

300

W0:::<{I­U

~ 200"'­0:::WCD~~

z 100>-l-V>ZWo

oN E SREEF ORIENTATION

observations are consistent with thegeneralization that, in Palau, thisspecies is virtually restricted to hardsubstrates on seaward reefs.McGowan (1958), however, lists ex­amples of other islands in Micronesiawhere substantial trochus populationswere found on lagoonward reefslopes.

Discussion

Our survey results provide a quant­itative picture of commercial trochuspopulations inside and outside marinesanctuaries that have existed for over20 years in Koror State. Three ques­tions must now be addressed.

I) Was the sanctuary system work­ing as originally intended?

2) If not, why?3) What constitutes an appropriate

habitat for a trochus sanctuary?

Koror State survey data indicatethat, on average, the seven surveyedsanctuary sites had only half as manytrochus as nearby exploited areas.Had the system been working asoriginally planned, higher trochusdensities should have been found in-

78

Figure 6. - Relationship betweenreef orientation and mean densi­ty of Trochus ni/oticus atsurveyed sites in Koror State,1982. Density was positively cor­related with degree of exposureto surf, and generally declinealong a NE, E, S, W gradient.

w

side the sanctuaries. Thus, the sanc­tuary system was only marginally ef­fective at the time of the survey.

The two sanctuaries located onKoror's western barrier reef (sites I1and 14) had such low numbers oftrochus that they were essentially use­less. These sites appear to have beenchosen arbitrarily. Because most ofKoror's western barrier reef drops offsteeply, minimal intertidal andshallow subtidal habitats are availablefor trochus. Moreover, the outer reefflats are generally submerged at lowtide and lack the boulder and rubble­strewn intertidal zone that seemsfavorable to the recruitment ofjuvenile trochus (Heslinga, 1981 b).Our census data support the positionthat Koror's west coast barrier reef ismarginal-to-poor trochus habitat.Not surprisingly, this area is seldomvisited by trochus harvesters.

Of the five remaining trochus sanc­tuaries in Koror State, four (sites 2, 8,9, and 15) were located on the southor southeast facing sections of theirrespective reefs. As noted, these wererelatively calm sites with sand and livecoral dominating the surveyed depthcontours. These substrate types offer

numerous hazards to T. ni/oticus ofall ages and are probably activelyavoided. Settling larvae and post­larvae can be consumed by live coralsor buried under shifting sand.Juvenile and adult trochus probablyavoid sand because it inhibits locomo­tion and adhesion of the foot.Locomotion across live coral isundesirable because it would exposethe foot to stinging nematocysts. Wehave never observed T. niloticuscrawling on or adhering to live coralin nature. Perhaps most important,live coral and loose sand do not pro­mote growth of the low filamentousalgal species which form a principalpart of the T. niloticus diet.

Based on this line of reasoning, weconcluded that four of the fivetrochus sanctuaries on Koror's eastcoast had been placed in marginal orpoor habitats. Only one of the east­coast sanctuaries (site 7), located onan east-northeast facing reef, had asuitable substrate composition(dominated by pavement and cor­alline algae) and a high density oftrochus relative to nearby areas.

Of the areas surveyed, the one withthe most favorable conditions for T.niloticus was Ikedelukes, an exposedbarrier reef segment about 5 km southof the Malakal Lighthouse (Fig. 7).Ikedelukes embodies a number ofphysical and biotic characteristicswhich we believe are ideal for trochussanctuaries. These include an un­obstructed exposure to surf generatedby northeast trades, a gently slopingbottom, a wide reef flat that is expos­ed at spring low tides, a subtidal sub­strate that is predominantly pavement(especially in shallow contours), andan abundance of coralline algae andlow filamentous algae at 1-3 m.

Ikedelukes supports an immensenumber of grazing herbivorous fishes,with acanthurids and scarcids beingparticularly abundant. The bluelinesurgeonfish, Acanthurus lineatus, isespecially conspicuous at Ikedelukesand may be a useful "indicator"organism for superior T. niloticushabitats. Similarly, the presence ofother herbivorous archaeogastropodsat Ikedelukes, including T. pyramis,

Marine Fisheries Review

Figure 7. - Aerial view of Ikedelukes Reef in Korar State, presently a sanctuaryfor commercial trochus. Photograph courtesy of and copyright by DouglasFaulkner, N.Y.

T. incrassatus, T. macu/atus, andTurbo argyrostoma, implies that thisreef is particularly favorable forgrazers.

Ikedelukes is far enough from thecommercial port of Palau (35 minutesby speedboat) to make pollution aminimal concern; however, the reef isclose enough to allow surveillance andexperimental work. Most important,Ikedelukes had high numbers ofmature Trochus ni/oticus relative toother nearby sites. All of these con­siderations figured in our eventualdecision to recommend Ikedelukes asa permanent trochus sanctuary forKoror State.

We emphasize that trochus sanc­tuaries must be placed near enough todistrict centers to allow periodicsurveillance. In the case of KororState's western barrier reef sanc­tuaries, it is unlikely that they wereever visited by conservation personnelsimply because of their great distancefrom Koror Island. Similarly, thenumber of reefs designated as sanc­tuaries should not place an excessiveburden on the surveillance capabilitiesof local authorities. In retrospect, thiswas certainly the case in the KororState system.

Ecologically and economically, theoptimum number and size of trochussanctuaries for a given locale are un­known and open to debate (Bradburyand Reichelt, 1981). Thus, in manyrespects the sanctuary concept muststill be regarded as an experimentalmanagement policy. A scientific ap­proach to the questions involved ishighly desirable but would undoubt­edly demand far more time and ex­pense than are likely to be available.In any event, it is clear that in mosttrochus producing countries theamount of reef area devoted topreservation is likely to depend moreon political and economic realitiesthan on the persuasiveness oftheoretical arguments. Until more isknown about coral reef ecology andabout reef ecosystem management,the best that can be achieved is someform of compromise between ex­ploitation and conservation, based onas much quantitative information as

46(4),1984

possible and an appreciation for localconditions and customs.

Following the completion of thetrochus surveys in Koror State, werecommended to government officialsthat the trochus sanctuaries be reduc­ed and consolidated into twomoderately sized, centrally locatedreefs near enough to Koror to bevisited frequently by conservationpersonnel. Ikedelukes Reef andNgederrak Reef (Fig. 7) were selectedas sanctuaries because they fulfilledthe necessary physical, biotic, andgeographic requirements reasonablywell.

We also recommended that wholereefs (from channel to channel) bedesignated as sanctuaries because thiswould eliminate the time-consumingannual task of placing markers on thereefs to delineate sanctuaries. It seemspractical, where possible, to treatwhole reefs rather than portions ofreefs as management units.

The proposed revisions to theKoror State trochus sanctuary systemwere approved in May 1982 by theMayor and Chief, Ibedul Yutaka Gib­bons (Heslinga, 1982). The harvestseason opened the following month

and lasted 4 weeks. The new sanc­tuary regulations were broadcast overlocal radio in the weeks beforeharvesting began. During the seasonthe new trochus sanctuaries werepatrolled regularly by MarineResources Division personnel, in­cluding the authors. A few sporadicincidents of sanctuary poaching wereobserved; the fishermen involvedclaimed ignorance of the radio broad­casts and willingly moved out of thesanctuaries when informed of the newregulations. In 1983 Koror State of­ficials declared a moratorium ontrochus harvesting, and no violationswere observed during routine checksof the sanctuary reefs. We believe thatfuture trochus poaching incidents inKoror State will be negligible ifsurveillance is maintained during theharvest season.

The need to establish coral reefsanctuaries and other conservationmeasures in the nations of the tropicalPacific is widely recognized (Johan­nes, 1978, 1982; Salvat, 1981; Stod­dart, 1981; Wells, 1981b; Kelleher andKenchington, 1982), especially inareas where traditional forms of reeftenure and resource protection have

79

been eroded by urbanization and theeffects of Western contact. Our studyis instructive because it illustrates acase in which quantitative data wereused successfully to lobby for theimprovement of a coral reef manage­ment program. We assembledevidence showing that a 20-year-oldtrochus sanctuary system would likelybe improved by some simplemodifications, specifically, consolida­tion and relocation to superiorhabitats. Local Marine ResourcesDivision personnel were trained toevaluate the problem and subsequent­ly participated in proposing a solu­tion. The assistance and approval ofthe Koror State Mayor and Chiefwere actively sought and proved in­strumental in achieving an acceptablemodification of policy. It is signifi­cant, too, that baseline data wereestablished and practical methodsdeveloped to serve as a model forfuture comparative analyses.

Acknowledgments

Financial support for this work wasprovided by the Pacific FisheriesDevelopment Foundation (PFDF)and the Division of MarineResources, Republic of Palau. We aregrateful to the staffs of PFDF, theNational Marine Fisheries Service atHonolulu, Hawaii, and LivingMarine Resources, Inc., of SanDiego, Calif., for their cooperation.Invaluable logistical assistance in

80

Palau was provided by Ibedul Gib­bons, Alan Seid, Koichi Wong,Toshiro Paulis, and the entire staff ofMicronesian Mariculture Demonstra­tion Center. We thank DouglasFaulkner for permitting us to use hisaerial photograph of Ikedelukes Reeffor Figure 7.

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_,----_. 1981b. Larval development, set­tlement and metamorphosis of the tropicalgastropod Trochus niloticus. Malacologia20:349-357.

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___, and A. Hillmann. 1981. Hatch­ery culture of the commercial top snailTrochus niloticus in Palau, Caroline Islands.Aquaculture 22:35-43.

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Johannes, R. E. 1978. Traditional marineconservation methods in Oceania and theirdemise. Annu. Rev. Eco\. Syst. 9:349-364.

1982. Traditional conservationmethods and protected marine areas inOceania. Ambio 5:258-261.

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