ATOLL RESEARCH BULLETIN NO. 169
INVESTIGATIONS OF ACANTlfASTER PLANCI IN SOUTHEASTERN POLYNESIA DURING
1970-1971
b y Dennis M. Devaney ancl John E. Randall
Isanecl by
THE SMITITSONIAN INSTlTUTION
I n t r o d u c t i o n
Duke o f G l o u c e s t e r G r o u p , ' r u a m o l u A r c h i p e l a g o A n u a n ~ ~ r a r o A t o l l
C a m b i e r o r M a n e a r e v a G r o u p , T u a m o t u A r c h i p e l a g o P i t c a i r n G r o u p
Ocno A t o l ~ l . P:i-t c a i r n I s l . a n d H e n d e r s o n I s l a n d D u c i e Ato1.l.
R a p a anci l l l l o t s cic B a s s T h e A u s t r a l I s ].and s S o ~ l t l : ~ . c ~ n Cools I s l a n d s
M a n u r ~ c (11c:rvcy) A i t u t a l c i
R a r o t o n @ S o c S ~ e L y : I s l a n d s
U o r a B o r a Hua11i.n.e T a h i t i
N o r i ; l ? e r n T u a i l ~ o t u A r c h j c l a g o R a n g i r o a
Mailih i A t o l l T a l c a r o a h-l;oll.
I ~ l a r q u e s a s 7:s l a n d s h t n c r i . c a ~ i Samoa
'1,'utu.i 3.a Rcsuioi:
F l p r r c ? s (:l?ol..30rcini: 1,.
23 )
-L-
Iloui;e of t h e " W c s t ~ : a r c i U iiri Soul.:i?oas ierl-1 O c e a n i a A i ~ u a n u : r a r o AIL o:l.3.
,
l'uamo tu. hrcl-lSipc:l.agoCanibi.or :is1 a n d s , F r c n c i . ~ P o 1 ~ y n e s . i . a Pfo:~~f;a:reva :Is l a n d
'I'hc :i.s l.antls o:S 0c:no
,
1~1cntlci:soil,
a n tl Tluc i.c":i L c a i i r n 1:s l and 'I.'hc :i.sl.anri o:S R a p
R.
, u ~ v a v a e , ' . AusL:ra:l~ 1s:l;inrlsi\:i t u l . a k S . 1:s l a n d a n d ?.lamlac (11c:rv c?),
:I:s
I :lntJ s)
Cool< Is 3.ai)ds
I?, ~ 1 . ~ . .. , o ~' i ; o . i ~ g a , Cook :ii.,:l~ands l t a o r Soc:ici.y :l:sl.antis I i u a h i r i c , Soc:i.cL), :I:s:l;i.n~is l'a!:i
C S ,
S o c i c - l ; y ? s l a i i c I sP l a t e I , : f i g u r e A . AcanLhasLer G a n c i u p o n A c r o p o r a n c o r a l a f t e r f e e d i n g . F r e s h l y e a t e n a r e a on l e f t . Mangareva I s l a n d ,
S t a - t i o n
3 ,
d e p t h m , Dec. 1 2 , 1 9 7 0 . P h o t o by D . M . D e v a n e y .P l a t e I, f i g u r e
B.
A c r o p o r a n c o r a l s h o w i n g f r e s hfeed in^
s c a r ( u p p e r l e f t ) , p r e v i o u s l y e a t e n , a l ~ g a l c o v e r e d a r e a ( l o w e r r i g h t ) , ancl l i v i n g p a r t ( c e n t e r l e f t )
.
Fiangareva I s l a n d , S t a t i o n3 ,
d e p t h 2 rn, Dee. 1 2 , 1 9 7 0 . P h o t o byD.M.
Devaney.P l a t e T I , f i g u r e A .
-
A c a n t h a s t c r p l a n c i . o n u n d e r s i d e of r e c e n t l y e a t e n . Acrolsoran c o r a l .Mangareva :[sl.and, S t a t i o n
3 ,
d e p t h 2 in, Dec. 1 2 , 1 3 7 0 . P h o t o byD.M.
Devaney.P l a t e 11, f i g u r e B. A c a n t h a s t e r
--
p l a n c i among b r a n c h e s o:f A c r o p o r a n c o r a l . O l d e r d e a d a l g a lc o v e r e d p o r t i o n s ( r i g h t ) a n d l i v e c o r a l ( f ore(;rountl, l e f t
) .
Mangarcva I s l a n d , S t a t i o n3 ,
d e p t h3
i n , Dec. 1 2 , 1 9 7 0 P h o t o b y D . M . Devaney.P l a - t e T:l:C, :Ti.gure A . F r c s h :feetli.ng s c a r o n P o r i . t e s c o r a l a n d surroulldiLng d e a d b r a n c h i . n g c c o r a l s . R a r o t o n g a , Cook I s l a n d s , d e p t h 30 in, M a r . 1 1 , 1971. P h o t o by D . M . Devaney.
INVESTIGATIONS OF ACANTHASTER PLANCI IN SOUTlllEASTERN POLY.
NESIA DURING 2970-1911
1
/
by Dennis M. DevaneyL' anti John E. Randall-
INTRODUCTIOK
In recent years considerable interest has been aroused by the damage -to reefs in the tropical Pacific caused. by large populations of the crown-of-thorns starfish (~canthaster planci), a coral predator. Survey teams have made starfish counts and assessed the damage to reefs at a number of islands. Most of this activity has taken place in the western Pacific, partic- ularly the Trust Territory and Grea-t Barrier Reef. Very little information has been obtained on the relative abundance of this starfish and -the condition of the coral reefs i.n southeast
Oceania.
The opportunity to visit a number of islands in this
remote part of the Pacific was provided by a marine biological expedition carried out during the period December 1 , 1970 to May 20, 1971 on the 99-foot schooner "Westward" owned and
operated at that time by the Oceanic Foundation. During the expediti.on, Bishop Museum marine bi.ologists Dennis M. Devaney and John
E .Randall conducted a reconnaissance for the crown- of-thori~s starfish at the various islands visited. When the starfish were present in rlurnber-s, an assessment was made of their damage .to the coral reefs. At several places, measure- ments, gonad samples, and color notes were -taken of +. planci
(Table
1 ) .The expedition was Cinanccd by a grant to tlie Bishop Museulri f rorn the National Geographic Society, augmented by
funds from the Oceanic Foundation for operation of the vcssel.
Support for the surveys of A. planci was provided hy the Sca Grant Program of tlie University o:f liawai.i.
Surveys for the starfi.sl-1 weye carried out
atthe foll.owin~
groups o:f is1.aud.s (number of islands vis:i.l;ed wi-thin groups
S~IOLV-II i . 1 ~
parentheses)
:Tuanlotu Arc1,:ipelago
(11) , Ganibi.cr
Group ([I ) , Pi-tcai.m Group ().I), Rapa
( 2 ), Austral ( 3 ) , sou-Lhcrn Cook (3), Society (3), and the Marquesas (6). In additi.011, Devaney visited two islands in American Samoa. The itinerary of tlre "l\'cstward" is shown :in l!igure
1. Names of the isl.ands vi~sited are underlined.
L'Rcrnice P. Bishop Muscum, P.O. I3ox 6037, 1-Ionolulu, IIawai~
9681 8.
T e x t f i g u r e s :i.:n -th.i.s r e p o r t o:f t h e :i.slarrds a t r.jklich s u r v e y s f o r A c a n t h a s . t e r p l a n c i ruere c a r r j . e d o u t a r e b a s e d o n maps i n P a c i C i c 1 s l . a n t i s Volume I T , E a s - t e r n 1 3 a c i ? i c , 1 9 4 3 G e o g r a p h i c a l Handboolc S e r i e s , N a v a l : L n t e l . l i g e n c e llivJ.s:iorr, C a l n b r i d g e .
I)UISI? O'B' GS.,OUCES1'I3H GROUP
,
TIJAMOTU IZIIC;TI:I:.PJ~T,AGO017 Uecelnber
6 ,
1 9 7 0 - t h e "T!'estwa:rdV a r ~ c h o r e d o f f t h e n o : r l h - w e s t s i d e o:f A n u a n u r a r o (20' 2 5 ' S ; 1 1 ~ 3 ~ 33l I ? ) , a sma:L.l ui1i.n- h a h i t e d a t o l l which. 1-acks a p a s s ( ~ i g . 2). A b o a t was c a r r i e d :frorn t h e s e a w a r d s i d e , a c r o s s t;he r e e f f l a t -to t h e 1.agoon. A s e a r c h . : f o r A c a n t h a s t e r was c a r r i e d ou-t i.a t h e ~ i e s t e r - I ? . lagoon^( p i g . 2 , A ) - w i ~ h SCUBA a n d by s1c:i.n d i v i n g . C o n s i d e r a b 1 . e l i . v e c o r a l was p r c s e : n t a l o n g t h e s i d e s a n d - l o p o f c o r a l . l a 3 o l l s as wel.1 as i:n i s o l a t e d p a t c h e s o n t h e s a n d y l a g o o n hot-tom (maxi.mu111 clep-lh, 11.0 f e e . t ) . A t o n e linol.1, e x t e n d i n g f r o m a dc]>th. o f
a p p r o x i m a t e l y 3 0 f e e - t t o n e a r t b e s u r f a c e , a l a r g e Acan-i;h.asCer w a s c o l l e c t e d i n m i d - a f t e r n o o n a l o n g t h e sj.de o f - t h e k n o l l a t a clep-th o f 20 f e e t . C o l o r n o t e s - t a k e n a - t t h e ti.me o f c a p t u r e r e v e a l e d t h e s t a r f i s h t o h a v e t h e a b o r a - 1 s i d e g r e y i s h -to t a n w i t h t h e s p i n e s r e d d i s h . No r e c e n t f e e d i n g s c a r s w e r e s e e n , a n d t b e a n i m a l w a s n o t f e e d i n g when t a k e n . F u r t h e r s u r v e y o:f - t h e l m o l l a n d a d j a c e n t k n o 1 . l ~ f a i l e d -to r e v e a l a d d i t i o l i a l . A c a n t h a s t e r . Measurement d a % a c o n c e r n i n g t h i s s p e c i m e n a r e p r e s e n t e d i n T a b l e 1 .
Two SCUBA d i v e s w e r e made by R a n d a l l a n d t h e "Westward"
c r e w o f f t h e s e a w a r d s i d e o f t h e r e e f a l ~ o n g t h e n o r t h w e s t e r n s i d e o f t h e a - t o l l . The :l'i.rst d i v e ( ~ i g . 2 ,
R)
r e v e a l e d a r a t h e r s t e e p s l o p e w i t h l i v e c o r a l a n d c o r a l r u b b l ~ e ; n oA c a n t h a s t e r -was s e e n n o r v a s t h e r e a n y s i g n o:T feed:iLng b y s t a r -
--
f i . s h . . The s e c o n d d i v e , ( p i g . 2 , C ) w h i c h was made f a r l : h e r s o u - t h . , r e v e a l e d e v e n r i c h e r c o r a l growkh and more v a r i . e d . t o p o g r a p h y w i t h c a v e s , e t c . ; a g a i n , t h e r e was no s i g n of A c a n t h a s - t e r n o r e v i d e n c e o f , c o r a l prcda-t:i.on.GAMUTER OR MANGARRVA GROUP, TUAMOTU hRCHIPl:,l,AGO On December
9 ,
" 1 i e s t ~ ~ a r d . " ancho:~:::ed a t 7'o:r.t Ri.kiAea 0x1 Manf.?arcva ( ~ i ~ g s .3
and I-I.), t h e p r i n c i p a l sett:l.cmcn.t o f t l r c Gamhier G r o u p . On Decembcr 1 1 o u r s u r v e y .?or-
h c a n t ; i l a s l c rcolnrncuced. O b s e r v e r s i.ncl.uded Devanc?y, llandal~l..
,
i k a n TI. Canuioy, a n d J c a n - P i e r r e E a b l e L , f : i . s h e r y b i o l o g i . s t w i t h Cen-t:t:::c?d Ex.l>Fr:~melitat:i.ons du P a c i l ' i q u e
( c .
13. I?.) .
P r i . o r t o o u r a r r i v a l . we h a d b e e n :i.~?forrncd. by personnel a:? S e r v i c e clc 1.a P c c h e e a n d t h e k . s t ~ - ~ u t d e R e c h e r c h c s MFdj.cales i n Papeelie l h a - t nulnerous A .--
p l a n c i h.ad b e e n f o u n d a l o n g - t h e s o u t l ~ ~ . j c s l e r n s i d e o fMangareva I s l a n d ( a p : p a r e n t l y : f i r s t n o t e d i n O c t o b e r , .I 9 6 9 ) .
Our : f i r s t s t a t i o n
( . I
o fFig.
3 ) was c a r r i e d o u t i n . t h e l.agooii a few h u n d r e d y a r d s sou1;heas-t of 1:l.e Tenoko (23'4 '
3 0 "S ; 1 2 I ) . Patcl-r r e e f s w e r c i n v e s t i g a t e d wi.th t h e u s e of SCUBA a n d b y s k i ~ n d i . v i n g . The o i a j o r i t y o f t h e c o r a l . w a s a l . i . v e ; t h e r e w a s n o e v i t l e n c e o f & c a n t l r a s t ~ .
On t;hc af-l;e.rnoon o f t l i e same d a y Che s e c o n d s t a t i o n ( 2 of F i g . 3 ) was r u n o u t s i ~ d e t h e b a r : r i e r r e e f j u s l ; s o u L h w c s t o:f l l . e Tenolco a.t a d c p t h of 20 t o
6 0
f e e t . Sonie t o w i n g was c a r r i . c d ou-t i n t h e vi.cin:iA.y. C o r a l g r o w t h was l.usli, No s t a r - fishes w e r e s e e n .On December 1 2 a ser::i.es of s e v e n tows w e r e made ( a - l t e r - n a t i n g o b s e r v e r s ) a l o n g t h e soul;h.wes-t s h o r e o f Mangareva
Is:L.and. T h e s e c o n s t i . t u t e d S t a t i . o n
3 .
The f i r s t two b e g a n a t A t i t u i ~ t i . a n d t h e 1 . a s t e n d e d t h r e e m i l e s beyond n e a r t h e ~ i e s t e r s send o f t h e :i.s:Land. No A c a n L h a s t e r w e r c s i i g h t e d u n t i l t h e end o f Lhe f i . f - t h tow rvlrcn
several
w e r e s e e n . Two speci.mens w e r e c o l l e c t e d , as w e r e t h e c o r a l s ( ~ c r o ~ o r a )--
on. which t h e y w e r e f e e d i n g . W i t h t h e s i . x t h tow t h e n u m b e r s o f s t a r f i s h i n c r e a s e d , a n d t h e c o r a l damage as w e l l . We h a d f o u n d t h e A . p1an.c;c o n c e n t r a - t i o n t h a t h a d been. r e p o r t e d t o u s
(X
o f - ~ i g s .3
a n dL b ) , I t i.s a r e l a t i v e l y r e s t r i c t e d a r e a c e n - t e r e d o n 23'
7 '
20''S ; 1 3 5 O 0 ' 3 0 " li' b e t w e e n P t e . d e Ganoa and P t e . T e r i n l u r o a a t a n a v e r a g e d e p t h . o f 20 f e e t . Tho d i v e r s c o l l . e c t e d 2 3 s - t a r f i s h
i i i
95
m i n u t e s . Wbiile t o w i n g i n t h e area o f g r e a t e s t d e n s i t y , a b o u t o n e s t a r f i s h . w a s s e e n p e r m i n u t e . T h i s c e r t a i n l y d o e s no-t q u a l i f y as a n i n f e s t a t i o n , b u t t h i s number o f s t a r f i s h i s w e l l a b o v e t h e n o r m a l o c c u r r e n c e . T l ~ e c o r a l g r o w t h i n t h i i s a r e a i s r i c h ; i t i s d o m i n a t e d b y t a b l e and b r a n c h i n g A c r o p o r a . I ~ ; s l . i n i a t e s o f t h e p c : r c e n . t a g e o:f l i . v e c o r a l by t h e o b s e r v e r sr a n g e d f r o m 6 5 t o 80% ( m o s t o:f t h e d e a d c o r a l . a p p e a r e d t o h a v e b e e n k i l l e d r o c e n t l . y , p r o b a b l y by
A .
p l a n c i . ) . About h a l f of t h e s t a r f i . s : h w e r e a c t i v c l ~ y feeding d u r i n g t h i ~ s t i o ~ e ( 1 300- 1 4 3 5 h o u r s ) , m a i n l y o n s p e c i e s of k c r o p o r a . S a m p l e s o f t h e c o r a l b e i n g e a t e n w e r e s a v e d . The d o m i n a n t t a b l e a c r o p o r a n w a s i t l e n t i . f i ~ e d asA.
& c u . l a - t arook)
by D r J o h nW.
We1Ll.s a t Corne1.l Uni.versiAy. M e a s u r e m e n t s a n d d e t e r m i n a t i o n s of s e x w e r e made o f t l i e s a m p l e of A . - p l a n c iable
1) .
The s t a r - f i . s h w e r e b l u i s h - g r e y a b o r a l . l y , t h e - t i p s o f t h e s p i . n e s o r a n g e - r e d .D u r i n g Lhe s e v e n t h tow t h e rrumbers o f s - t a r f i s h d i . m i n i s h e d ( e i , $ l t c o u n t e d i.n 13 m i n u t e s ) . By t h e t i m e P t e . T e r i ~ l l u r o a w a s r e a c h e d , n o more
A.
p l a n c i o r w h i - t e f e e d i n g s c a r s o n t h e c o r a l w e r c s e e n .On t h e f o : l l o w i n g d a y a t 1500-1600 h o u r s we r e t u r n e d t o t h e s i t e o f c o n c e n t r a t i o n m a i n l y f o r u n d e r w a t e r p h o t o g r a p h y ( p l a t e s 1-11). A s t r o n g c u r r e n t ( a b o u t 2 k n o t s ) w a s f l o w i n g i n a SF d i r e c t i o n , a g a i n s t t h e p r e v a i l i n g w i n d .
On December 1 4 Devaney a n d Cannoy i n v e s t i g a t e d t h e l a g o o n
a r e a by t o w i n g between I l e T a r a v a i and I l e Agalsauitai (Lt of F i g . 3 ) . L i v e c o r a l was found t h r o u g h o u t t h e a r e a b u t no A c a n t h a s t e r was n o t e d .
I n a c o n f e r e n c e w i t h D r Raymond Bagnis of t h e I n s t i t u t d e Recherches M Q d i c a l e s on March 20,
1971
we l e a r n e d t h a t s u r v e y s f o r s t a r f i s h were made i n 1969 a l o n g t h e l a g o o n o f f I l eT o t e g e g i e where t h e a i r s t r i p h a s been completed and o f f I l e Kamaka. No s i g n i : f ' i c a n t numbers of
--
A c a n t h a s t e r were s e e n .PITCAIRN GROUP 1 . Oeno A t o l l
On December 18-20, 1970 "Westward" a n c h o r e d o f f t h e n o r t h s h o r e of -the u n i n h a b i t e d a t o l l of Oeno (23'
55l
S ; 130°Lr51
W )( ~ i g .
5 ) .
Two d a y s of i n t e n s i v e s n o r k e l i n g , d i v i n g , and some t o w i n g f a i l e d t o r e v e a l any A c a n t h a s t e r o r any s i g n of r e c e n t c o r a l damage t h a t might b e a t t r i b u t e d t o i t . The l a g o o n i s s h a l l o w ( n e a r l y a l l l e s s t h a n 10 f e e t d e e p ) and dominated by s a n d and c o r a l r u b b l e . The o c c a s i o n a l p a t c h e s of c o r a l r o c k d i d n o t have a heavy c o v e r of l i v e c o r a l . The o n l y a r e a o u t - s i d e t h e r e e f which was e x p l o r e d was i n t h e v i c i n i t y of t h e s m a l l b o a t p a s s a g e on t h e n o r t h s h o r e ( t h i s p a s s a g e , by t h e way, i s s h a l l o w and would n o t be s a f e w i t h even a moderate s w e l l r u n n i n g from t h e n o r t h ) . Although t h e r e were more r e e f a r e a s o u t s i d e t h e r e e f t h a n i n t11.e l a g o o n , t h e b o t t o m was s t i l l donlinated by sand--even t o t h e o u t e r edge of t h e s h e l f a t 100 f e e t o r more where t h e s l o p e of t h e bottom s t e e p e n e d . Dives on o u t e r r e e f a r e a s wcre made t o d e p t h s of 120 f e e t . C o r a l growth was r i c h e r t h a n i n t h e l a g o o n , b u t s t i l l s p a r s e by u s u a l a - t o l l s t a n d a r d s .2. P i t c a i r n I s l a n d
A t o t a l of 23 d a y s were s p e n t d i v i n g and towing around P i t c a i r n I s l a n d (25O 01-1.' S ; 130'
0 6 ' W)
duri.ng t h e p e r i o dDecember 21, 1970 t o J a n u a r y 2 1 , 1 9 7 1 . T h i s rugged h i g h i s l a n d i s o n l y a b o u t 2 m j ~ l e s 1-ong and 1 m i l e w i d e ; c o n s e q u e n t l y , i t was n o t d i f f i c u l t t o e x p l o r e i t s marine environment t h o r o u g h l y
i n t h e -time a v a i l a b l e . I n s h o r e , t h e b o t t o m i s dominated by b o u l d e r s , o f t e n of l a r g e s i z e , h e a v i l y c a r p e t e d w i t h brown a l g a e ( p a r t i c u l a r l y ~ a r g a s s u r n ) . Very l i t t l e l i v e c o r a l may be found i n - t h i s zone. I n t h e d e e p e r s e c t o r s (below a b o u t 40 f e e t ) , s a n d o r l o w - p r o f i l e r o c k , e i t h e r covered. w i t h brown
a l g a e o r a t h i n v e n e e r of s a n d , a c c o u n t f o r most of t h e bottom.
T\iith t h e h e l p of I ' i t c a i r n f:i.shermen t h e :few w e l l d e v e l o p e d r e e f a r e a s were l o c a t e d . These were f o u n d m a i n l y a t clepths g r e a - t c r
t h a n 80 f e e t . The most l u x u r i a n t p a t c h r e e f , lsnown t o t h e i s l a n d e r s a s "The B e a r " , o c c u r s o f f Gannet Rj.dge on t h e n o r t h s i d e of t h e i s l a n d . I t i s a b o u t 400 s q u a r e m e t e r s i n a r e a and r i s e s from a s a n d bo-ltom w i t h a l i . t t l e r u b b l e i n 7/15 f e e t t o a
height of about 30 feet above the base level. It is almost completely live coral. A more extensive reef (about
100meters in length and about 1/3 this in average width) may be found off Adamstown on the north side i n 70 to
100feet of water. In contrast, this reef is composed of dead coral rock about half covered with colonies of live coral (usually no more than 18" i n diameter and mostly Porites). In six dives on this reef, (X in Fig. 6) two adult Acanthaster were found at 90 feet one of which was preserved and data taken (Table 1).
The bottom temperature when one starfish was collected was 211.8' C. Later the same area was subject to a thermocline effect. The water at 90 to
100feet was roily and at least 2 to 3 degrees C cooler (no thermometer was on hand at this time and when one was brought the following day, the water no longer felt as cool at the 100-foot depth). Very little coral damage was apparent on the reef off Adamstown. One of the two starfi-sh had been feeding, and a sample of the coral on which it fed was taken. No other Acanthaster was seen at Pitcairn.
3. Henderson Island
On January 1 1 and January 17-1 8
atotal of two days were spent on the north and west side of Henderson Island (240 %0' S ; 128' 20'
W ) ( ~ i g .5). The island is elevated coral lime- stone, with cliffs along most shores 50 feet or more in height, the central region of the island being at most
100feet high and relatively flat. Henderson is 5 miles long and nearly 3
miles wide. It is uninhabited except during rare visits by Pitcairn islanders seeking miro wood (xhespesia ~opulnea).
The shelf region offshore is relatively narrow, but the reefs are more extensive than those of either Oeno or Pitcairn.
Dives were made to depths of 160 feet. No Acanthas-ter was seen nor was any damage noted to the coral which might be attributed to this asteroid.
4. Ducie Atoll
For a period of 2-1/2 days beginning January 13, 1971 a marine biological survey was made of Ducie (24O 40' S; 124'
47' 10, the easternmost atoll of Oceania. It is snzall
( 1 . 3miles in greatest diameter) and uninhabited. It is certainly one of the least visi-ted islands of the globe. There is a shallow channel on the SW side to the lagoon which can be
negotiated by a ship's boat, except during low tide, providing one is alert for the numerous small coral heads. This small channel is the main exchange for the lagoon, although some water passes over at high tide between two islcts on the east side. The deeper part of the lagoon is about 50 feet in depth
(53 feet at deepest sounding). The lagoon is interlaced with
irregular coral heads, many interconnected at their bases, and
many reaching nearly to the surface. The coral on these coral
heads is nearly all completely dead. The water of the lagoon
had a dark greenish cast, and the visibility was only about
75 feet at the maximum, probably reflecting a low level of flushing. Eight hours were spent i n towing, snorkeling, and diving in criss-cross pattern throughout the lagoon. Only one adult Acanthaster was seen, on the SW side of the lagoon just north of the small boat passage, i.n about
10feet (pig. 5 , x).
This was preserved in formalin able
1for data). Temperature in -the lagoon at the bottom and surface was 26.5O C and the salinity 38 o/oo.
In contrast to the lagoon, a moderate amount of live coral was seen in the small boat passage--nearly all as small colonies.
Outside the reef from the small boat passage to the
hqicorner of the atoll, from the reef edge to at least 100 feet, the bottom was predominantly dead coral encrusLed with
coralline red algae. It was evident that all of this coral had been killed at approximately the same time. Without a knowledge of the succession of benthic life on dead coral, it is difficult to guess how long the coral had been dead, but it would seem to be at least a year. The nullipores had nearly bridged the gap between adjacent terminal branches of some
heads of closely branched Acropora. No Acanthaster was seen outside the reef (dives were made to 180 feet). Time did not permit investigation of the northern or eastern sides of the atoll, but the almost complete disolation of corals i n the areas examined. did not suggest that the pic%ure would be different elsewhere. Concomitant with the paucity of corals was the dearth of fishes, both in number and individuals;
this was all. the more evident in view of the total lack of fishing pressure.
In view of the level of devastation of coral by Acanthaster in certain areas such as Guam and the Great Barrier Reef, it would seem plausible that the starfish could be responsible for Ducic's mass mortality of corals. The lack of starfish could be explained by their mortality following decimation of the food supply. Possibly there is some other reason, such as mortality due to intrusion of cold water from more southern latitudes. At almost 25O S, Ducie is near the southern 1-imit of distribution of reef corals. However, reconnaissance at Rapa and Ilots de Bass (see below) even farther south, revealed a proliferation of coral, including acroporans, without evident thermal destruction.
The presence of Acanthaster planci at Ducie extends the
known eas-tern limit of this species and together with the
specimens found at Pitcairn represent new distributional
records.
RAPA AND ILOTS
IIEBASS
A period of 25 days between January 26 and February 21,
1971 was spent at the island of Rapa (27' 35l S ; 144' 2 0 1
W )(Fig. 7) during which time a number of diving stations were worked all around the island. Several sea surface temperatures were taken; they ranged from 23.5 to 25O.C. On no occasion was Acanthaster found nor was there any indication of coral predation by the starfish. Although the local residents were familiar wi-th the crown-of-thorns (known throughout the French Polynesian area as ~ a r a m e a ) via radio descriptions from Tahiti and most recognized this starfish from our photographs, all denied its existence in their waters.
Around most of Rapa coral growth is poor, at least in depths less than about 50 feet. There are, however, well developed fringing reefs in Haurei ( ~ h u r e i ) Bay and luxuriant patch reefs off the entrance to the bay. Table and branched acroporan as well as many other scleractinian corals were noted and collected. For the most part, the corals are vigorously growing and well developed in this area.
On February 20 a visit of one day was made to Ilots de Bass (~arotiri) (27' 5 7 ? S ; 143O 26' w), about 50 miles S B of Rapa. Short survey dives were made between NE and S B Rocks in depths froin
0to 150 feet. The deeper areas showed a bottom covered with lush, vigorously growing acroporan and other corals, interspersed with sandy areas. No Acanthaster was noted.
TI-IE AUSTRAL ISLANDS
Three of the Austral Islands were visited between February 25 and February 28, 1971 . A.t Raivavae (23' 52 ' S ; 1 4 . 7 ~ 401 W ) we heard from a school teacher that the crown-of-thorns had been seen within the lagoon on the SW side but not in great numbers. On February 25, together with this man, Devaney, Randall, and two inenibers of the "Westruard" crew examined the area where Acanthaster had been noted (Fig. 8 , 1). Over a n hour's survey i n the shallow part of the lagoon failed to
reveal any Acanthaster or evidence of coral damage which might be attributed Lo this starfish. SCUBA diving outside the
lagoon beyond Motu Haa ( ~ a h a ) and off the southern boat passage in depths from 2 0 to 175 feet revealed considerable live coral but no Acanthaster.
Dives at selected sites around the islands of Tubuai and
Rurutu failed to demonstrate any Acanthaster or evidence of
coral depredation. At Tubuai, the dives were made within the
lagoon near the
NWside and off Motu Moturoa by Devaney and
out beyond the barrier reef on the north side, west of the boat
passage by Randall during the afternoon of February 26. At
Rurutu, diving was conducted off Avera Bay and more extensively off Moerai Bay on the
h%side of the island during February 27 and 28. Local residents and officials of the French government at both of these islands had not seen or heard of the crown-of- thorns i n their waters.
SOUTHERN COOK ISLANDS 1 . Manuae ( ~ e r v e ~ )
On March 6, 1971 between noon and
1800hours, Devaney examined the lagoon and one seaward site of Manuae (Fig. 9 , insert) for Acanthaster. A small boat was dragged through the shallow channel along the h E side of Manuae Islet (l9O 21' S ; 158O 58l w). The lagoon was crossed between Manuae and Te Au
0T u Islets. Very little coral appeared in the shallow parts of the lagoon (depths 2-6 feet). Many black sea cucumbers, primarily golothuria -, were seen on the white sand bottom.
Later in the afternoon a dive was made in the deeper portion of the lagoon near the south central part where the bottom depth is 16 feet. Several coral knolls rise very near the surface. The coral was alive and extensive, especially along the upper margins of the knolls. Several underwater photographs were taken of coral along such edges. No bvidence of Acanthas-
ter nor coral damage from the starfish was noted.
--
In the late afternoon, on the seaward side of Manuae Islet just S E of the small boat channel ( ~ u r a k i n a Passage) (Fig. 9,
x), Devaney and Rhett McNair made a SCUBA dive from 40 to 180 feet. The deeper zone from 120 to 180 feet is nearly vertical.
The bottom here was dominated by large sheetlike terraced colonies of live Porites. Very few other live corals were present, but there was considerable dead coral covered with coralline algae. Leading into this steep sector is a canyon which appears to be an erosion channel. This was examined from a depth of 40 to
100feet. The bottom of the canyon, which averages about
20feet in width, is clean sand and boulders, some cemented by nullipores. The walls are between
10and 1 5 feet in hei.ght. Above the walls, o n the south side, 80 to 90%
of the bottom was covered with dead coral. Most of this coral, especially the branching forms of - Acropora and Pocillopora, was cemented in place by nullipores. In some areas a scum of blue- green algae covered much of the surface. Although there was no sign of Acanthaster in this area, the high percentage of dead coral condition of the bottom was reminiscent of the reefs killed by the starfish in Guam. Possibly the dead coral was a result of a n infestation of A. planci. - --
2. Aitutaki
Beginning at noon on March 7, 1971 the lagoon of Aitutaki
(1 8O 53' S ; 159' 47' W) was surveyed by Devaney, Rich Costello,
and James Haywoocl. The path of the survey is shown by the dotted line of Fig. 9 beginning just south of the main village of Arutanga. Numerous coral knolls (most about 15 to 30 feet in diameter) occur i n the zone between A and
E3Fig. 9. Ten of these lcnolls were examined completely by two or more divers.
U p to 90% or more of the branching corals (mostly Acropora and
~ocillopora) were dead. Much of the dead coral was covered with brown, green, and coralline red algae. Soft corals and the blue starfish Linckia Laevigata were common (3 to 8 star- fish per knoll). Approximately at point
E3the first coral heads with live branching acroporan corals were noted. The depth. to the sand bottom here is
10to
12feet. Each of these knolls had several adult Acanthaster on them. Most of the starfish were concealed near the lower part of the knolls (one of six starfish on a knoll was on the sand bottom beneath a ledge). None of the starfish were feeding, but fresh feeding scars were evident on the corals.
Moving toward Maina Islet from point B the knolls had a higher percentage of live coral and f e w e r . planci. On these heads with more live coral Linckia laevigata was not common.
The ,direction of survey was then altered toward Tekuotu Point, and random lcnolls were investigated. The greatest concentration of A. - -- planci was noted on knolls near Tekou-tu Point. Here
several of the starfish were seen actively feeding on coral.
along the edges of knolls near the surface. Underwater photo- graphs were taken i n this area and. starfish were collected from three of the knolls.
Towing over the sandy bottom between knolls there arc small heads of Acropora (probably formosa) which were mainly dead, with indication of not having died too recently. Only a few had the usual commensal invertebrates and the pomacentrid fish
--Dascyllus aruanus associated with them.
Proceeding SSE from Tekoutu point we entered an area so shallow with numerous coral heads (pig. 9 , D) that it was impossible to continue towing. The coral here was alive, and there was no evidence of Acanthaster.
We conclude from this survey that there was an active zone of predation. by A. planci in the lagoon of Aitutaki.
between the wreck of the Alexander and Tekoutu Point (approx- imately B-C of Fig. 9). We believe that the starfish have advanced in a souther1.y direction from Aru-banga and are
responsible for the dead coral. Tha-t they have crossed areas of bare sand is suggested by the high percentage of dead stands of Acropora between the knolls. The absence of small or even medium-sized starfish is also indication that a single rela- tively small population of A. planci has moved as a progressive front in the Aitutaki lagoon.
Mr Val Hinds, the Fi-sheries Officer of the South Pacific
Comn1i.ssiol1, matle a b r i e f s u r v e y f o r A c a n t h a s t e r i n t h e lagoon of A i t u t a l i i . i n t h e summer of 1970. He f a i l e d t o fi.nd any s t a r f i . s h a t t h a t t i m e . I o p a Ma]-slers, a Rarotongan f i s h e r m a n
~ h . 0 accompanied M r Hjnds d u r i n g h i s s u r v e y , was a l s o w i t 1 1 o u r -team a t A i t u t a k i . ITe d o e s n o t r e c a l l s e e i n g t h e many l i n o l l ~ s of dead c o r a l d u r i ~ n g t h e 1970 i n v e s - t i ~ a t i o n s . He s t a t e d . , however, tha-l: t h e s u r v e y g r o u p had 1.i.tLlc e x p e r i e l i c e w i t h A c a n t h a s t e r and i t s damage t o cora:ls
.
On March 8 between t h e h o u r s of 0830 and 1105 a s u r v e y was made of t h e seaward s i d e of A i t u t a k i from Arutanga P a s s a g e
sout:h t o l f a i n a I s l e t ( t h e dot-Led l i n e of
E-F,
F % g . 9 ) , a d i s t a n c e of a b o u t 11. mi.les. An o b s e r v e r was towed behind a s m a l l b o a t and s p o t c h e c k s were made by slcin and SCUBA di.ving.Devaney was a s s i s t e d i n t h i s s u r v e y by Haywood and David Bryant of t h e "Westward" crew.
Tl3.e seaward s h e l f of t h i s a r e a , f r o m a dep-th of 10 t o 100 f e e l , c o n s i s - t e d m a i n l y of dead c o r a l . A few e n c r u s t j - n g c o r a l s were a l i v e a s were o c c a s i o n a l s m a l l h e a d s of Acropora and
P o c i l l o p o r a , and t h e r e was l j . v e M i l l e p o r a and-soft Z c y o n a r i a n c o r a l s . Approximately 80 t o 90% of t h e s c l e r a c t i n i a n c o r a l s , i n c l . u d i n g massive 'eads of P o r j - t e s , were dead. No e v i d e n c e of A c a n t h a s t e r was n o t e d . u n d e r w a t e r p h o t o s were t a k e n and samples
-
of d e a d c o r a l t a k e n . The samples r e v e a l e d much e n c r u s t a t i o n by c o r a l l i . n e r e d a l g a e ( u p t o 1 inm i n t h i c k n e s s ) . L t i s v e r y p o s s i b l e t h a t A c a n t h a s t e r i s r e s p o n s i b l e f o r t h e e x t e n s i v e c o r a l m o r t a l i t y of t h i s s e c t o r of A i t u t a k i .Cook I s l a n d government o f f i c i a l s informed u s t h a t t h e r e h a s b e e n heavy u s e of c h l o r i n a t e d h y d r o c a r b o n i n s e c t i c i d e s a t A i - t u t a k i i n recen.t y e a r s . They a l s o men-tioiled t h a t s e v e r a l 55-gal-lon drums of DDT had b c c n dumped i n o r j u s t o u - t s i d e A r u t a n g a P a s s a g e a f t e r World War I T .
3 . -
R a r o t o n g aWhen Devaney went on "Westward" t o Manuae and A i t u t a k i , Randal.] rernained al: Rarotonga (21 1 3 '
S; 159' 1.1.6.
j 1 W ) w i t h Dean B. Cannoy f o r a s u r v e y of A c a n t h a s t e r t h e r e . Ilevaney r e t u r n e d f o r t h e i n v e s t i g a t i ~ o n s on Rarotonga on March 1 0 .On March
6 , 1971
Randall, was towed from Avaavaroa P a s s on t h e s o u t h s i d e of RaroLonga f o r a d i s t a n c e of 300 m e t e r s t o t h e e a s t o v e r a n a v e r a g e d e p t h of Ll-0 f e e t ( ~ i g . 1 0 , A ) . Away from t h e p a s s t h e w a t e r was c l e a r enough t o r e v e a l a bottom n e a r l y c o m p l e % e l y c o v e r e d w i t h l i v e c o r a l w i t h no t r a c e ofA c a n t h a s t e r . A d i v e was t h e n made i n 50 f e e t w i t h SCUBA i n t h e company o f W a l t e r Hambuechen, t h e A g r i c u l t u r e O f f i c e r of t h e Cook I s l a n d s . Toward t h e end of t h e d i v e , t h e d e e p e r p o r t i o n of t h e r e e f was i n v e s t i g a t e d . A t a b o u t 80 t o 90 f e e t some dead c o r a l was o b s e r v e d . A t 100 t o 1 2 5 f e e t f r e s h f e e d i n g s c a r s from A c a n t h a s t e r were s e e n ; t h e c o r a l h e r e was 90$ d e a d . Two
a d u l t A c a n t h a s t e r were o b s e r v e d i n t h i s a r e a , one of which was b r o u g h t t o t h e b o a t (398 mm i n d i a m e t e r , 1315 gms; s e e T a b l e 1 ) , a l o n g w i t h two k i n d s of c o r a l on which i t was f e e d i n g . A f t e r a r e t u r n t o s h o r e f o r f r e s h t a n k s , a second d i v e was made ( w i t h Dean B. cannoy) i n a n a t t e m p t t o f i n d t h e same d e e p a r e a of heavy c o r a l d e s t r u c t i o n . The e x a c t a r e a w a s n o t l o c - a t e d , f o r no f r e s h f e e d i n g s c a r s and no A c a n t h a s t e r were s e e n , b u t t h e c o r a l was a t l e a s t 90% d e a d a t 100 f e e t and below, w i t h some d e a d c o r a l a p p a r e n t a t t h e 80- t o 90-foot l e v e l .
The s o u t h s h o r e of R a r o t o n g a i s s u b j e c t t o c o n s i s t e n t heavy s w e l l . On o n l y a few d a y s of t h e y e a r i s i t calm enough
t o v e n t u r e t h r o u g h t h e p a s s i n a s m a l l b o a t f o r d i v i n g a s we d i d on March
6 .
We b e l i e v e t h a t t h e heavy s u r g e may be r e s p o n - s i b l e f o r A c a n t h a s t e r a v o i d i n g c o r a l i n t h e s h a l l o w e r s e c t o r s of t h e s o u t h e r n Rarotongan r e e f .On March
7
two d i v e s were made o f f t h e o i l t a n k e r buoys n e a r t h e h a r b o r e n t r a n c e on t h e n o r t h s h o r e of Rarotonga (J?ig.1 0 , B ) . I n one h a l f h o u r , a t a d e p t h of 50 t o 80 f e e t , R a n d a l l c o u n t e d
26
A c a n t h a s t e r . Of t h e s e , 1 8 were f e e d i n g , nrostly on P o r i t e s . The bottom i n t h i s a r e a i s abou-t3/4
c o r a l , a s viewed-
f r o m a b o v e . O f t h i s , 60 t o70$
was d e a d . Most of t h e s u r v i v i n g c o r a l i s P o r i t e g , some o f which s t a n d s <.n l a r g e h e a d s 1 0 t o 1 5 f e e t above t h e b a s e l e v e l of t h e b o t t o m . One c a n n o t h e l p b u t f e e l t h a t t h e s t a r f i s h have a v o i d e d--
P o r i t e s i n i t i a l l y , b u t now a r e f o r c e d t o f e e d on i t i n view of t h e p a u c i t y of more f a v o r e d k i n d s . Samples were t a k e n of t h r e e s p e c i e s of c o r a l on whicht h e s t a r f i s h were f e e d i n g .
The s e c o n d d i v e began a t t h e e a s t e r n m o s t of t h e two buoys ( d e p t h
4 5
f e e t ) , and moved toward s h o r e t o a d e p t h of 30 f e e t . T h e r e was more l i v e c o r a l i n t h i s z o n e , b u t s t i l l a b o u t h a l f w a s d e a d . I n t e n m i n u t e s no A c a n t h a s t e r were found and. no v e r y r e c e n % c o r a l damage w a s s e e n . However, we b e l i e v e t h e o l d e r damage was due t o t h e s t a r f i s h , p a r t i c u l a r l y s i n c e i t i n v o l v e d mainly s p e c i e s o t h e r t h a n P o r i t e s .A t h i r d d i v e on March
7
was rnade o f f t h e l a u n d r y , 1 k i l o - m e t e r west of t h e o i l t a n k e r buoys ( ~ i g . 1 0 , C ) . The d e p t h was45
t o 80 f e e t . I n a d i v e of 30 m i n u t e s t h r e e a d u l t k a n t h a s t e r were c o u n t e d , one of which was f e e d i n g on c o r a l ( s a m p l e t a k e n T T h i s a r e a had more s a n d bottom t h a n t h e p r e v i o u s a r e a s ( a b o u t h a l f s a n d and r u b b l e , and h a l f c o r a l ) . Half of t h e c o r a l a tt h i s l o c a l i t y was d e a d , s e e m i n g l y from A c a n t h w . Most of t h e s u r v i v i n g c o r a l w a s P o r i t e s . No towing was p o s s i b l e from t h i s a r e a t o t h e h a r b o r b e c a u s e of t u r b i d i t y of t h e w a t e r .
An a-t-tempt was made on t h e morning of March 8 t o launch.
t h e s m a l l g r e e n f i b e r g l - a s s s k i f f t h r o u g h a n a l l - e g e d b o a t p a s s a g e n e a r B l a c k Rock,
mi
I i a r o t o n g a . T h i s proved i m p o s s i b l e ancl t h e morning was l o s t . I n t h e a f t e r n o o n towing was a t t e m p t e dd i r e c t l y o f f t h e wreck of "Yankee" on t h e r e e f of Avarua ( ~ i g .
1 0 , D ) . I t was n o t p o s s i b l e t o s e e t h e bottom w e l l enough b e c a u s e of d i r t y w a t e r , s o a d i v e was made i n
45
t o 55 f e e t . I n 30 m i n u t e s 38 a d u l t A c a n t h a s t e r were c o u n t e d . Of t h e s e , 1 8 were f e e d i n g , s e v e n on P o r i t e s . Samples were s a v e d of f o u rc o r a l s p e c i e s o t h e r t h a n P o r i t e s on which t h e s t a r f i s h were
f e e d i n g . I n t h i s a r e a t h e bottom is a b o u t
85%
c o r a l , a b o u t h a l f of which i s d e a d . Again, most of -the s u r v i ~ v i n g c o r a l i s P o r i . - t e s .-
The s t a r f i s h were d e t a c h e d frorn t h e bot?;om t o d e t e r m i n e w h e t h e r t h e y were f e e d i n g o r n o t . When d e t a c h e d , t h e y f o l d t h e i r arms v e n t r a l l y , t h u s f o r m i n g a n e a r l y c o m p l e t e s p i n o u s b a l l which t e n d s t o r o l l i n sand c h a n n e l s w i t h s u r g e . One s u c h d e t a c h e d s t a r f i s h r o l l e d back w i t h t h e s u r g e t o s t r i k e R a n d a l l ' s w r i s t and one f i n g e r a,nd i n f l i c t s e v e n d e e p s p i n e wounds.
A s e c o n d d i v e w a s made on March 8 o f f Pue, 1 . 3 k i l o m e t e r s e a s t of t h e wreck of "Yanlcee" ( F i g .
.lo,
E ) . The d i v e covered a d e p t h r a n g e of 30 t o 100 f e e t i n a n a r e a where t h e bottom was a b o u t 50% c o r a l . C o r a l damage w a s n e a r l y a s heavy a s o f f"Yankee" b u t o n l y e i g h t A c a n t h a s t e r werc s i g h t e d i n 30 m i n u t e s ; a l l b u t one of t h e s e were i n % h e d e p t h r a n g e of 80 t o 100 f e e t . Because of d i s c o n c e r t i n g p a i n from -the s p i n e wounds, R a n d a l l was p r o b a b l y n o t a s a l e r t i.n c o u n t i n g a s he would o t h e r w i s e have b e e n .
l'hat e v e n i n g t h e pai.n was s t i ~ l l m a i n l y c o n f i n e d t o 'the r % % - i s t and h a n d , a l t h o u g h t h e r e was some r a d i a t i o n up t h e arm.
The n e x t morn:i.ng p a i n had s u b s i d e d i n t h e l i m b b u t an o v e r a l l :i~:Llness p r e v a i ~ l e d which n e c e s s i t a t e d bed r e s t . Among t,he
symptorns .were b a c k a c h e , h e a d a c h e , j o i n - t p a i n , m a l a i s e , and l o s s of a p p e t i t e .
The wounds were slow t o h e a l , p a r t i . c u l a i - l y t h r e e of them a r o u n d which n e c r o t i c t i s s u e d e v e l o p e d t o a r a d i u s of a b o u t
3
mm. A week l a t e r t h e r e was s t i l l s o r e n e s s around t h e s e t h r e e wounds and s e v e r e i t c h i n g of t h o s e more f u l l y h e a l e d .On March 1 0 , 19'71 Devaney was towed. a l o n g t h e northwesl, s i d e of Raro-tonga between Mbtu Toa and J3lack Hock f o r a p e r i o d of 10 m i n u t e s ( F i g . 1 0 , F ) . 13uring t l l i s p e r i o d 57 A c a n t h a s t e r were s i g h t e d o v e r a d i s t a n c e of a:pproximal;ely 500 y a r d s . I n d i v - i d u a l s t a r f i s h were s c a t t e r e d o v e r t h e bottom i n d e p t h s from
30
t o
55
f e e t . It was n o t e d t h a t i n s e v e r a l c a s e s more a n i m a l s a g g r e g a t e d a l o n g e d g e s of c o r a l r i d g e s n e x t t o s h a l l o w sand g r o o v e s . A check d i v e i n t h i s a r e a showed c o n s i d e r a b l e dead b r a n c h i n g c o r a l b u t w i t h .the l a r g e s c a t t e r e d h e a d s of P o r i - t e s s t i l l m a i n l y a l i v e . h few f r e s h w h i t e f e e d i n g s c a r s weree v i d e n t . A t t h e end o:T -the tow t h e w a t e r was becoming t u r b i d , b u t t h e r e rjas no sign t h a t t h e number of
--
A c a n k h a s t e r hadd e c r e a s e d .
L a t e r i n -the morning o f March l o t h , Devaney, R a n d a l l , and Hambuechen niade a SCUBA d i v e j u s t s o u t h o:? B l a c k Rock ( F i g . 1 0 ,
G ) a t a d e p t h of 90 t o 100 f e e t . Our l o c d i o n was a p p r o x i m a - t e l y
3/4
m i l e S W of t h e end of t h e e a r l i e r tow ( p i g . 1 0 , 17'). We n o t e d t h a t most of -the b r a n c h i n g Acropora and, P o c ; i l l o p o r a c o r a l was d e a d , w e l l coveTed w i t h low a l g a e and i n some c a s e s had ac o v e r i n g of c o r a l l i n e a l g a e . L i v e h e a d s of P o r i t e s remained.
No A c a n t h a s t e r was n o t e d i n t h e s m a l l a r e a c i r c u m s c r i b e d duri.ng t h i s d i v e ( a p p r o x i m a t e l y 100 y a r d s i n d i - a m e t e r ) .
h
t h e a f t e r n o o n of t h e same day a SCUBA d i v e was made between t h e t w o o i l l i n e buoys a b o u t 200 m e t e r s w e s t of A v a t i u Harbor a t a d e p t h of 40 t o 50 f e e t ( ~ i g . 1 0 , D ) . Massive l i v e P o r i - t e s h e a d s with. r u b b l e and sand p a t c h e s dominaLe t h e a r e a---
w i t h s n i a l l e r l e s s a b u n d a n t h e a d s of b r a n c h 1 . n ~ c o r a l s p r e s e n - t . These branch:i.ng c o r a l - s , m o s t l y Acropora s p p . and P o c i l l o p o r as p p . were found t o b e dead and overgrown. No A c a n t h a s - t e r was s i g h t e d ; however, a d i v e t o t h e same a r e a two d a y s l a t e r r e s u l t e d i n t h e s i g h t : i n g of t h r e e a d u l t s t a r f i - s h , one of whi.ch was f e e d i n g on P o r i t e s .
On Marc11 1 1
,
1971 Uevaney,
accompanj-ed by M r IIdmhuecl3en, s u r v e y e d t h e nor-th. s i d e of R a r o t o n g a , e a s t of Avarua 1-Iarbor.Towing colnmencecl w e s t o:f t h e wreck of t h e "Yanlcee" a t a d e p t h of 50 f e e t and p r o c e e d e d p a r a l l e l t o t h e c o a s t f o r 100 y a r d s ; no A c a n t h a s t e r was e v i d e n t a l t h o u g h t h e bottom a p p e a r e d t o be d e a d c o r a l . We t u r n e d seaward i n t o d e e p e r w a t e r . A t a d e p t h of 100 f e e t we noted. t h e f i r s t Acantbastel: t r a v e l i n g o v e r sand
---
be-tween c o r a l r i d g e s ; immediately t h e r e a f t e r a l a r g e number of s t a r f 1 . s h was o b s e r v e d i n a c o n c e n t r a t e d band a b o u t 50 y a r d s wide e x t e n d i n g e a s t w a r d . A SCUBA d i v e at: a d e p t h between 100 and 120 f e e t was made. 'We counted
23
a d u l t i n d i v i d u a l s coveri.11,y a n a r e a abou-t 50 y a r d s i n d i a m e t e r n e x t t o a sand g r o o v e .S e v e r a l s t a r f i s h were f e e d i n g on P o r i t e s . Only a sma:L.l percen- t a g e of t h e b r a n c h i n g c o r a l s were o b s e r v e t i t o bc a l ~ i v e ; t h e r e s t were c o v e r e d w i t h low a l g a e and nul.S.i.pores, t h e l a t t e r f i l . l ~ i . n g i.n -the c r - e v i c e s between b r a n c h e s . Unrierwater photo- graplig were Lalceli w i t h Nfikolios and fl.as11.. Seven of ikrc small.er Acai~.thas= were c o l l ~ e c t c d f o r s i z e and s e x mcasurernents ( s e e
m,
and gonad sarnples -talcen.. A p o r t i o n of -two i n d i ~ v : i ~ t i u a l s col.lec-bed was r e t a i n e d f o r l . a t e r exami.na-lion. (one which wasy e l l o r v i s h c o l o r e d wit11 numerous pedicel.:l.ari.a)
.
The c o l o r of most of t h e s p e c i m e n s a p p e a r e d g r e e n i . s h , g r e y i ~ s b . , o r bl.u:i~sh. a-I;1 0 0 - f o o t d e p t h b u t wcre r e d i n . t h e f l a s h p i c t u r e s and r e d upor1 b r i n g i n g tlie star:f'islies t o th.e s u r f a c e , t h e d i f : f e r e n c e i n c o l ~ o r b e i n g due t o t h e e x t i n c t i . o n of r e d c o l o r w i t h dep-th.
I n . t h e time a v a i l a b 3 . e we wcre u n a b l e t o s u r v e y t h e eiil;:i.re c o a s t a l a r e a of R a r o t o n g a , b u t tihe numerous
4.
planc:ii ande x t e n s i v e c o r a l damage o b s e r v e d a t 7ij.dely s e p a r a t e d a r e a s
s u g g e s k s - t h a t -the s t a r f i s l i mi.ght be e x p e c t e d i n a b m d a n c o aS~l.
around t h e i s l a n d .
l i a r o t o n g a w i t h a b o u t 1 3 , 0 0 0 p e o p l e i.s t h e mos-Lt p o p l ~ l o u s of t h e Cook : I s l a n d s . A g r i c u l t u r e i s i m p o r - t a n t , arid t h e u s e o f
c h l o r i n a t e d h y d r o c a r b o n i n s e c t i c i d e s - - f i r s t DDT and now mainly d i e l d r i n and l i n d a n e - - i s e x c e s s i v e (Hambuechen, p e r s o n a l
c o m m u n i c a t i o n ) .
SOCIETY ISLANDS 1 . Bora Bora
On March 1 8 ,
1971
two teams of d i v e r s examined t h e c o r a l and b o t t o m environment on b o t h s i d e s of Teavanui P a s s on t h e west s i d e of Bora Bora (16' 3 0 ' S ; 151° 145'w)
( F i g . 1 1 ) . Oneteam ( ~ e v a n e ~ , McNair and B r y a n t ) worked a l o n g t h e n o r t h e r n r i m of t h e p a s s and seaward a s f a r a s t h e n o r t h e r n end of I l e
T e v e i r o a . With t h e e x c e p t i o n of a s m a l l a r e a o f f t h e m i d d l e of I l e T e v e i r o a which r e v e a l e d dead c o r a l , t h e p a s s and seaward
r e g i o n . a p p e a r s t o s u p p o r t considerable l i v e c o r a l . No A c a n t h a s t e r was o b s e r v e d . The one s r n a l l a r e a w i t h dead c o r a l shows a ruest- ward p r o j e c t i o n of t h e r c e f and. a p p e a r s t o recei.ve heavy s u r f . The d e a d c o r a l p r o b a b l y r e s u l - t e d from wave a c t i o n . A t a dep-th of 110 f e e t , and d e e p e r o f f t h i s a r e a , l i v e c o r a l w a s abundan-t.
The second team of d i v e r s
anda all
and. Cannoy) was towed a l o i i g t h e s o u t h s i d e of t h e T e a v a n u i P a s s and s o u t h a s : f a r a s t h e m i d d l e of I l e Tupua ('Toopun) a b o u t 1 .2 m i l e s from t h e p a s s on t h e seaward s i d e . No s i g n s of c o r a l damage due t o t h e crown- o f - t h o r n s c o u l d b e d e - t e c t e d . l'he b o t t o m was inostly l i v e c o r a l . A few h e a d s of Acropora w i t h w h i t e a r e a s were n o t e d , b u t d i v i n g f a i l e d t o r e v e a y any s t a r f i s h .A SCUBA d i v e i n c l u d i n g b o t h Devaney and. Randall on t h e seaward s i d e o u t s i d e t h e r e e f ( F i g . 1 1 , X ) showed a m o d e r a t e l y s t e e p d r o p from 60 t o
155
f e e t . A c o n s i d e r a b l e amount of l i v e c o r a l was s e e n on t h i s s l o p e . The b o t t o m was mainly s a n dbetween
155
and175
f e e t . T h e r e was no e v i d e n c e of A c a n t h a s t c r a c t i v i t y .A c c o r d i n g t o a n i n f o r m a n t i n Bora Bora, Erwin C h r i s t i a n , who o p e r a - t e s a glass-bo-ttom b o a t and h a s a SCUBA f a c i l i t y , t h e r e h a s b e e n no e v i d e n c e of an i n c r e a s e i n t h e number of A c a n t l l a s t e r a t - t h i s i s l a n d . Only a n o c c a s i o n a l i n d i v i d u a l i s s i g h t e d . He menti-oned h a v i n g r e c e n t l y s e e n one o r two in. t h e s o u t h w e s t e r n p a r t of t h e l a g o o n s o u t h of I l e 'S'upuaiti. We towed a n o b s e r v e r i n t h i s s e c t o r of t h e l a g o o n d u r i n g t h e a f t e r n o o n of March 1 8 b u t f a i l . e d -to : f i n d any
-
A . p l a n c i o r cora:L damage.2.
--
HuahineOn March
1 9 ,
1971 s e v e r a l h o u r s were s p e n t a l o n g t h e n o r t h w e s t s i d e of T1uahi.ne ( 1 6 O 1.15'S ;
1 5 1 0w ) .
A tow was made from i n s i d e Avamoa P a s s t o A v a p e i h i P a s s a l o n g t h e seaward s i d e ( ~ 1 1 2 , A ) . ~ . T h e r e were no s i g g s of
A c a n t h a s t e r ; t h e mouth of t h e Avamoa P a s s on t h e s o u t h s i d e i s a s c o u r e d pavement bottom w i t h i s o l a t e d heads of l i v e
P o r i t e s and P o c i l l o p o r a c o r a l . Along t h e seaward s i d e between
--
t h e 'wo p a s s e s , t h e bottom i s a l s o h a r d w i t h a few s h a l l o w s a n d g r o o v e s and p o c k e t s . It i s m o s t l y c o v e r e d w i t h l i v e c o r a l , i n c l u d i n g-
P o c i l l o p o r a-
e y d o u x i ,2.
nleandrina and A c r o p o sw .
A s e c o n d tow was made on t h e s e a w a r d s i d e s o u t h of A v a p e i h i P a s s f o r a d i s t a n c e of 200 y a r d s t o a p o i n t j u s t o p p o s i t e M-t. Tavahi ( ~ i g . 1 2 , B )
.
Some dead c o r a l and r u b b l e was n o t e d and a SCUBA di.ve by R h e t t PlcNair o f f a s t e e p s l o p e t o 80 f e e t r e v e a l e d a c o n s i d e r a b l e amount of dead c o r a l ; however, no--
A e a n t h a s t e r was o b s e r v e d n o r were t h e r e any f r e s h f e e d i n gs c a r s .
SCUBA d i v e s were made n o r t h of Avamoa P a s s ( F i g . 1 2 , C ) . L i v e c o r a l banlcs s e p a r a t e d by s h a l l o w r u b b l e and s a n d g r o o v e s were n o t e d i n d e p t h s from 20 t o 100 f e e t . There was no s i g n of A c a n t h a s t e r .
--
S e v e r a l p e r s o n s f a m i l i a r w i t h t h e w a t e r s of Huahine, b o t h a t t h e i s l a n d and i n T a h i t i . , informed u s t h a t t h e y knew of no i n d i . c a t i o n of a n abundance of A . p l a n c i t h e r e .
-
3. --
T a h i t iAs e a r l y a s May 1 9 6 9 , e v i d e n c e of A c a n % b a s t e r
--
p r e d a t i o n on T a h i t i a n c o r a l r e c f s was k11oru.n. B y October 1969 t h e S e r v i c e de l a Pgche i n Papee.te w i t h v o l u n t e e r he1.p began a c o n t r o lprogram i n t h e l a g o o n a r e a s a t P u n a a u i a and P a e a ,
1 7
and 21k i l o m e t e r s SW of P a p e e t e , r e s p e c t i v e l y . A resume of t h e c o n t r o l program t h r o u g h O c t o b e r 1970 i s a v a i l a b l e i n a 9-page mimeo- g r a p h e d r e p o r t of t h e S e r v i c e d e l a ~ " c h e , d a , t e d llecember 1970-
Through t h e Icindness of D r Raymond Bag;~n%s of t h e I l 1 s t i ( ; u t de R e c h e r c h e s M Q d i c a l e s a t P a p e e t e and D r S . S t e i n , Chef du S e r v i c e de l a Pgche, we were a b l e t o examine s e v e r a l of t h e most affec-Led a r e a s , e s p e c i a l l y P u n a a u i a and Faone.
O n Plarch 2 2 , 1971 t h e l a g o o n of t h e d i s t r i c t o f P u n a a u i a was v i s i t e d ( F i g . 13, A ) . The d e v a s t a t i n g e f f e c t on t h e l a g o o n
c o r a l s , p a r t i c u l a r l y n e a r t h e b a r r i e r r e e f , was n o t e d . Over 1 0 , 0 0 0 A . p l a n c i had been removed from t h i s s e c - t o r . lire were a b l e t o - f i n d o n l y I 2 a d u l t s p e c i m e n s i n a peri.od of t h r e e h o u r s . A s p e c i a l e f f o r t was made t o f i n d j u v e n i l e s t a r f i s h . , b u t none were s e e n . A few small. w h i t e f e e d i n g s c a r s were
observed. n e a r b a s a l p o r t i o n s of s t a g h o r n Acropora, b u t d i l i g e n t s e a r c h i n g f o r young
-
A . p l a n c i i n t h e v i c i n i t y of t h e s e s c a r s f a i l e d t o y i e l d any s p e c i m e n s . Our s m a l l e s t specimen from t h e a r e a was of n~ediunr s i z e ( 1 100 g r a m s ) .On March 2 3 , 1971 Devaney j o i n e d M r F r a n c i s Nanai from -the I n s t i - t u t e de Recherches Mkdicales and M r Phi.ll.ip Tsu and t h r e e
o t h e r d i v e r s from t h e S e r v i c e de l a Pgche f o r a s t a r f i s h c o n t r o l m i s s i o n i n t h e l a g o o n of Faone on t h e e a s t e r n s i d e of T a h i t i ( 4 0 k i l o m e t r e s from P a p e e t e ) . We were informed by Tsu
t h a t a s r e c e n t l y a s March
9 ,
1971 s e v e r a l hundred A c a n t h a s - t e r had been removed from t h i s a r e a . F o u r d i v e r s of o u r g r o u p c o l l e c t e d 40 specimen.^ of A . p l a n c i i n about, two h o u r s . The s t a r f i s h were thrown i n t oa
s m a l l o a t , t a k e n t o s h o r e , and p l a c e d on l a n d f o r48
h o u r s b e f o r e b e i n g dumped. No cheniical i n j e c t i o n o r o t h e r methods of e r a d i c a t i o n have b e e n employed i n T a h i t i .On t h e o u t s i d e of t h e f r i n g i n g r e e f a n e x a m i n a t i o n was made of t h e bottom p a r a l l e l t o t h e r e e f edge a l o n g a t r a n s e c t o f 200 y a r d s . Dives were made from t h e r e e f edge .to d e p t h s of 50 f e e t a-t a di.s-tance of a b o u t 100 y a r d s Crorn t h e r e e f e d g e . T h e r e i s a heavy c e m e n t a t i o n of t h e c o r a l a n d r u b b l e w i t h
c o r a l l i n e a l g a e . T h i s o f t e n o b l i t e r a t e s t h e b r a n c h e s of t h g c o r a l s , making i t d i f f i c u l t t o d e t e r m i n e t h e amount of p r e v i o u s l i v e c o r a l c o v e r . T b e r e i s p a r t i a l c o r a l r e c o l o n i z a t i o n o v e r t h e cemented s u b s t r a t u m a t Faone. No s m a l l A . p l - a n c i were
- --
f o u n d , i n s p i t e of c a r e f u l s e a r c h .
On March 28 and 29 SCUBA d i v e s were made by R a n d a l l and Cannoy on t h e o u t e r r e e f o u t s i d e P a p e e t e Harbor o f f t h e middle of t h e c o n c r e t e b r e a k w a t e r i n t h e v i . c i n i t y of a wreck of a l a r g e i r o n - h u l l e d s a i l i n g v e s s e l . Depths ranged from 20 t o 250 f e e t . The c o r a l grow-th was good. A few w h i k i s h p a t c h e s on t h e c o r a l s u g g e s t i v e of A c a n t h a s t e r damage were s e e n i n t h e d e p t h r a n g e of 60 t o 100 f e e - t , b u t n o s t a r f i . s h c o u l d be f o u n d . The w a t e r was t o o t u r b i d f o r towing; a l s o - t h e r e was a n o i l
s l i c k on t h e s u r f a c e .
On March 29, t h e s e a was m o d e r a t e l y c l e a r N E from t h e end of t h e b r e a k w a t e r , and i-l; was p o s s i b l e t o s e e t h e bottom i n 30 t o 40 f e e t . A t o w was made f o r 1
.5
m i l e s o v e r t h i s d e p t h from -the NE end of t h e b r e a k r i a - t e r -toward Tau-noa P a s s . The botl:om was dominated by s m a l l h e a d s of P o c i l l o p o r a meandri.na. No A c a n t h a s t e r were s e e n .--
:I:t i s p e r h a p s no c o i n c i d e n c e t h a t T a b i t i and Raro-tonga, t h e o n l y i s l a n d s of heavy i n f e s t a - L i o n s of A c a n t h a s t e r p l a n c i of t h e 27 we v i s i - t e d i n
SE
O c e a n i a , a r e t h e ones of t h e g r e a t e s t human h a b i t a t i o n and h e a v i e s t a g r i c u l t u r e . One of u s h a sa l r e a d y s u g g e s t e d t h a t t h e r e may be a c o n n e c t i o n between t h e u s e of c h e m i c a l p e s t i c i d e s and t h e o u t b r e a k s of t h e crown-of-
t h o r n s s t a r f i s h ( R a n d a l l , B i o t r o p i c a ,
4 ,
1 9 7 2 , 132-14 4 ) .
NORTHERN 'SUAMOTU ARCIIII'ELAGO 1 . R a n g i r o a
R a n g i r o a i s t h e l a r g e s t a t o l l i n t h e Tuamotus. I t s e a s t e r n
end l i e s a t
15'
1 7 ' S ; 143O 1 3 ' It'. There a r e two p a s s e s , both on t h e n o r t h s i d e , a b o u t5
m i l e s a p a r - t . I n 1957 t h c r e were 700 i n h a b i t a n t s , m o s t l y in. two v i l l - a g e s , one a t t h e e a s t e r n s i d e of e a c h p a s s .O n A p r i l
6 ,
a d i v e was made from 4.0 t o 100 f e e t on t h e o u t e r r e e f 200 y a r d s e a s t of T i p u t a P a s s , t h e e a s % e r n m o s t of t h e two p a s s e s . The c o r a l growth was e x t r e m e l y r i c h . NoA c a n t h a s t e r were s e e n , n o r was any damage t o t h ~ e c o r a l s u g g e s t - i v e of t b e s t a r f i s h n o t e d .
On A p r i l
7
and 8 , d i v e s from 20 t o 60 f e e t were made on g r o u p s of c o r a l h e a d s in. t h e l a g o o n of R a n g i r o a a b o u t 1 m i l e e a s t of Ava-toru P a s s . L e s s t h a n 50$ o f t h e h a r d b o t t o mc o n s i s t e d of l i v e c o r a l . T h e r e was no s i g n of A c a n - t h ~ t e r . On A p r i l 8 , a tow was made from t h e w e s t e r n s i d e of t h e p a s s 1 / 2 m i l e t o t h e w e s t , t h e Low commencing a t t h e o u t e r h a l f of t h e p a s s . A t t h e edge of t h e p a s s i n 1 5 t o 40 f e e t
t h e r e was c o n s i d e r a b l e d e a d and b r o k e n c o r a l , b u t n o t sugges-t- i.ve of A c a n t h a s - t e r damage. On -the o u t e r r e e f i n t h e r e g i o n of t h e tow
( 3 0
t o 40 f e e t ) t h e bottom was monotonously f l a t c o r a l r o c k s t u d d e d wi-th s m a l l h e a d s of P o c i l l o ~ o r a , P o r i t e s , andM i l l e p o r a ( c o r a l a b o u t 1 / 3 of b o t t o m a r e a r The w a t e r was sorne- wl:~al; u r b i d by a t o l l s t a n d a r d s ( e v i d e n t 1 . y t h e d i s c h a r g e froin
t h e p a s s moves m a i n l y w e s t w a r d ) . A t t h e o u t e r edge of t h e r e e f t h e s l o p e s t e e p e n s and -the c o r a l growth i s r i c h e r . No Acan-
-
t h a s t e r were s e e n .
---
A tow was t h e n made from t h e o u t e r p a r t of t h e p a s s on t h e e a s t e r n s i d e f o r one m i l e i n tlse e a s t e r l y d i r e c t i o n , a t an.
a v e r a g e d e p t h of 50 f e e t . Because t h e w a t e r was v e r y c l e a r , i t was p o s s i b l e t o s e e o v e r a d e p t h r a n g e of a t l e a s t 20 t o 80 f e e t . Except a t t h e o u t e r p a r t of t h e p a s s anti t h e f i ~ s - t 200 y a r d s o r s o -to -the w e s t , whicll was f l a t c o r a l r o c k bottom ~ \ i j ~ t h s c a t t e r e d s n i a l l h e a d s of c o r a l , t h e b o t t o m was a l m o s t t o t a l ~ 1 . y c o v c r e d w i t h c o r a l j.n t h e 20 t o 80 f o o t d e y t h r a n g e . A di.ve was made t o 150 f e e t a-t t h e end oE t h e tow. Tbc f o l l . o w i n g clay s p o r a d i c bri.ef -tows were made from one m i l e t o s l i g h t l y inore t h a n two m i l e s t o t h e e a s - t of t h e p a s s , w i t 1 1 ilo change i n bottom -type. TIYO d i v e s were made from a r a n g e i n depl:h of
1 5
t o
1 4 0
f e e t . T h e r e i s a s t e e p d r o p - o f f of 6 0 t o70
d e g r e e s w i t h s a n d , c o r a l r o c k , and some l i v e c o r a l b e g i n n i n g a t abou-l 70 t o 80 f e e t . Only a v e r y few small w11.ite dead a r e a s on c o r a l were n o t e d , and no A c a n t h a s t e r were s e e n . The dominant c o r a li.s P o c i l l o p o r a . I n s e v e r a l broad a r e a s 3.n t h e depth. r a n g e of abou-t 3 O -to 70 f e e t i n . t h e v i c j ~ n i t y o f one t o two m i l e s e a s t o:f Avarua P a s s , dbout one t h i r d of t h e Pocj.l.lopora i s dead and v e r y h e a v i l y e n c r u s t e d w i t h c o r a l l i n e a l g a e and o t h e r marine g r o w t h . I f s u c h damage were c a u s e d by A c a n t h a s t e l - i n abundance, one c a n o n l y wonder why no s t a r f i s h c o u l d b e foursd a t t h i s -time i n t h e a r e a of p a r t i a l l y dead c o r a l .
