La pêche au crabe girafe : l'expérience des Seychelles = The ... - IRD
La pêche au crabe girafe : l'expérience des Seychelles = The ... - IRD
La pêche au crabe girafe : l'expérience des Seychelles = The ... - IRD
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IA ECHE AU CRABE GIRAFE - L'WERIENCE ES SEYCHELLES<br />
THE "A CRAB FISHERY - THE. SEYCHELLES EXPERIENCE<br />
Guy de Moussac et Michel de San<br />
Assistants techniques CEE <strong>au</strong>pres de la SFA<br />
Le <strong>crabe</strong> <strong>girafe</strong> íRanina ranina) est prdrent<br />
dans tout 1 'octrn tropical, pacifique<br />
(H<strong>au</strong>aii, Japon, Forrose, Philippines.-.),<br />
ainsi que dans l'ocean Indien. Les 2<br />
gran<strong>des</strong> pecheries .<strong>au</strong> monde sont celles<br />
d'Hawaii qui a debut6 avant 1950 et cel,le du<br />
Queensland en Australie dont l'exploitation<br />
remonte a 1970.<br />
Daas . .l'oc,rn Indien occidental, <strong>au</strong>cuns.<br />
granda pCcherie cormerciale n'existe, seules<br />
2 petites exploitations sont prCsentes a la<br />
RCunion et l'fle H<strong>au</strong>rice Cstatistiques non<br />
disponibles). Hais il est probable que le<br />
<strong>crabe</strong> <strong>girafe</strong> soit prtsent dans les captures<br />
annexes de certaines pecherics <strong>au</strong> chalut,<br />
notairent <strong>au</strong> chalut a crevettes.<br />
Cet article ,se propose de dtcrire le<br />
dCVe2OppeRent de cette nouvelle 'FCcherie eu<br />
<strong>Seychelles</strong>, ses techniques et ses captures. ,<br />
Quelques Clhents de biologie seront<br />
proposes.<br />
Les rxe?pIes Hawaïen et Australien seront<br />
f rbqucmmen t cites.<br />
1. HISTORIQUE DE LA PECHERIE SEYCHELLOISE<br />
Le <strong>crabe</strong> <strong>girafe</strong> et signal& pour le pre8i)t-e<br />
fois <strong>au</strong>x <strong>Seychelles</strong> par Ratcliffe (1976) qui<br />
avec la Division <strong>des</strong> pechcs seychelloise<br />
captura en 1974 et 1975 <strong>au</strong> filet raillant<br />
les premiers individuç.<br />
Plu#+ de 10 annes aprbs, l'Autorit8 de5<br />
Peches seychelloise CSFA) m i t en place yn<br />
programme de prospection de cette ressource<br />
<strong>au</strong>ec l'assistance technique de la CEE, Les<br />
resultats d'octobre 1986 a f4vrier 1987 .<br />
furent trts emcourahjeants et dBs mars 1987, .<br />
2 bate<strong>au</strong>x correrci<strong>au</strong>x se consacraient P<br />
cette peche.<br />
Les dbbarquements d'octobre 1986 O Rai 1987<br />
s'kl&vent P ?,t dont ?,t proviennent de<br />
capturer commerciales (tabl. 1 J . <strong>La</strong><br />
majorit4 der <strong>crabe</strong>s est vendue k une sOCi4te<br />
paraltatique de distribution de p[QduitSr 1.<br />
<strong>Seychelles</strong> Harketing Board, fish Division, k<br />
enuiron'30 RS le ki;lo (6RS I. 1 USI). Face A<br />
un important afflux de ce nouve<strong>au</strong> produit,<br />
quelques problhes de comuercialisation se<br />
posent, et le SHE n'achbte plus de <strong>crabe</strong>s<br />
avant d',couler une partie de ses stocks,<br />
Un march4 d'exportation est h l'ltudr re 3<br />
tonnes ont deja et¿ exportCeo vers la<br />
RCunion où le produit est dcie connu et se<br />
vend & un prix dlevc).<br />
<strong>The</strong> Kona crab (Ranina ranina) ir found<br />
throughout the tropical Pacific Ocean<br />
(Hawaii, Japan, Taiwan, Phillipineo.. .) a5<br />
well as in the Indian Ocean. <strong>The</strong> two major<br />
fisheries are those of Hawaii, which started<br />
prior to 1950, and of Queensland in<br />
Australia which has operated since 1970-<br />
In the western Indian Ocean, there are Only<br />
two small fisheries, in M<strong>au</strong>ritius and<br />
Reunion, for which no statistics are<br />
available. <strong>The</strong>se crabs may however exist in<br />
the bycatch of shrimp trawlers.<br />
This article will <strong>des</strong>cribe the development<br />
of a fishery in <strong>Seychelles</strong>, the fishing<br />
techniques and landings, as well as some<br />
biological parameters. Comparison wi 11 be<br />
made with the Hawaiian and Australian<br />
* f3gheries.<br />
I. HISTORY OF THE SEYCHELLES FISHERY<br />
<strong>The</strong> .Kona crab was first reported in<br />
Seychelies by Ratciiffe (1976) who, with the<br />
<strong>Seychelles</strong> Fisheries Division, c<strong>au</strong>ght the<br />
first specimens with gill nets in 1974 a*<br />
1975. More than 10 years later, tk<br />
<strong>Seychelles</strong> Fishing Authority (SFA), in tf&<br />
context of an -EEC techn<br />
programme, started to search<br />
Between October 1986 and<br />
results were very encourag<br />
March 1987, two commercial<br />
the fishery.<br />
W<br />
<<br />
cal assi stance<br />
for them again.<br />
February 1987,<br />
ng, and as of<br />
vessels entered<br />
Between October 1986 and May 1987, landings<br />
totalled 9.4t, of which 7.2t were from the<br />
commercial fishery (Tab1.e 1). Most of the<br />
crabs.are sold through a parastatal company,<br />
.the <strong>Seychelles</strong>; Marketing Board, Fish<br />
"Division (SMB), at a producer price of about<br />
Rs.30/kg (Rs.6 = $1). <strong>The</strong> SMB has had<br />
problems selling 50 much of a new product<br />
and now only purchases crab after having<br />
sold some of its stock. Export marketing<br />
trials are afoot, and 2t have already been<br />
exported to RBunion where the kona crab is<br />
'known and is sold for a high prsce.<br />
II. FISHING TECHNIQUES<br />
Kona crabs are commonly c<strong>au</strong>ght with hoopnets<br />
which are made up of an iron ring about Im<br />
in diametre, hung loosely with a double<br />
layer of netting (usually 5cm stretched<br />
mesh); 10 to 20 hoopnets are strung at 1O'tto<br />
20m intervals on a longline. <strong>The</strong> nets are<br />
baited, preferably with - fresh bonito, %d<br />
each set lasts 40 minutes on average. <strong>The</strong><br />
crabs, which are carnivorous, are meshed by<br />
the legs. Up to 50 crabs have been c<strong>au</strong>ght ~<br />
on a single net, but average catches are 1<br />
to 4.<br />
,,<br />
t<br />
i<br />
h<br />
9<br />
a<br />
5<br />
3<br />
P<br />
5<br />
(<br />
P<br />
I<br />
U,<br />
i.<br />
n<br />
LE<br />
di
._ .J<br />
2. LA..TECHHIQUE VE FECHE<br />
captufCs avec <strong>des</strong><br />
11 s'aoit d'un<br />
~~ercle de fer d'environ 1 &tre de diaretre<br />
recouvert d'une double nappe de filet<br />
maillant (naille etirte d'environ SC.); 10 P<br />
20 balances sont æontCcs, espacCes de 10 P<br />
20m, sur une filibre principale, <strong>La</strong> balance<br />
est;rappatCe, prefCrentielIemcnt avec de la<br />
bonite fraiche, et IaissCc en peche environ<br />
une quarrntainc de minutes. Le <strong>crabe</strong><br />
<strong>girafe</strong>, chrnivore, vient railler ses pattes<br />
dans le filet sans pouvoir ~'Cchapper. Les<br />
t<strong>au</strong>x de capture peuvent ateindre jusqua& 30<br />
<strong>crabe</strong>s par balance, mais varient en gCnOr.1<br />
entre 1 & 4 <strong>crabe</strong>s par carrelet. ,<br />
Les bate<strong>au</strong>x iæpliquts dans cette peche <strong>au</strong>x<br />
<strong>Seychelles</strong> sont de tailles tr&s variables:<br />
6,. A i4a selon les zones de peche et<br />
utilisent en -moyenne 4 filibres de 15<br />
balances. <strong>La</strong> duree de la rarCe varie entre<br />
1 et 4 ìours et .les <strong>crabe</strong>s sont conservCs<br />
sur grace.<br />
f<br />
3. LES zuws VE PECHE<br />
Le <strong>crabe</strong> <strong>girafe</strong> est un <strong>crabe</strong> fouisseur dont<br />
l'hsbitat est constitu¿ de vastes zones de<br />
sable dont la fraction ffne est importante.<br />
On le trouve surtout dans ¿es fondsde 30 P<br />
50r. En. Australie, (Br<strong>au</strong>n, 1986) il est<br />
signal4 de.0 A 80. de profondeur et B H<strong>au</strong>eii<br />
(YANSANT, i9782 de 2 d 200~. Il sewblerait<br />
qu'<strong>au</strong>x SeychrJJes, il soit present Fur<br />
l'enserb1e du plate<strong>au</strong> 'de Hahe, 18 o& le<br />
substrat est adCquate, nais avec <strong>des</strong><br />
densites parfois tres variables,<br />
4. ETUDES EH COURS ET PREHIERS RESULTATS<br />
<strong>La</strong> section recherche de Ia SFA est<br />
responsable de statistiques de peche<br />
ícaptures, effort en nombre de balances<br />
pos4esJ et a m i s en.place un programme de<br />
bioloaie pour connaitre les caractCristiques<br />
de la population:<br />
Le table<strong>au</strong> 2 donne les rCsultats<br />
preliminaires de cette Ctude et Its compare<br />
A ceux d'Hawaii et d'Australie.<br />
5. LES AUTRES PECHERIES :<br />
LES EXEtfPLES HAWAIEN ET AUSTRALIEH<br />
H<strong>au</strong>eii exploite depuis longteaps le <strong>crabe</strong><br />
<strong>girafe</strong>, les preiiPres statistiques remontent<br />
a 1950, les captures annuelles maximales<br />
s'CICvent A 18,8t en 1968 et 29,Zt en 1972.<br />
3 A 4 bate<strong>au</strong>x sont ConCernCs, a temps<br />
partiel, par cette pecherie. Les <strong>crabe</strong>s<br />
sont conservCs et vendus vivants en viviers<br />
(t<strong>au</strong>x de mortalit4 infCrieur d 5%) B <strong>des</strong><br />
prix de 7 & 10 US$ par kg (prix 1985)- Les<br />
Stocks ne semblent pas surexploites rralgre<br />
une peche rCcr4ative non controllCe tres<br />
importante: Suerdloff (1979) propose un<br />
M.S.Y. de 70t/an.<br />
Les pecherìes <strong>au</strong>straliennes du Queensland et<br />
du Neu South Uales sont be<strong>au</strong>coup plus<br />
rkcntes (1970) et d'envergures PIUS<br />
Boats 'of different sizes are used in this<br />
fishery in <strong>Seychelles</strong>: 6-5 to 14m (with a<br />
catcher boat), depending on the area firhed.<br />
<strong>The</strong> usually use 4 linea of 13 nets. Fiahing<br />
trips last 1 to 4 days, and the crabs are<br />
kept on ice.<br />
III. FISHING<br />
<<br />
<strong>The</strong> Kona crab normally lises buried in thi;<br />
sand, %o that extensive fine sand areas arcs<br />
its h8bitat. In <strong>Seychelles</strong> it is fbund<br />
mainly at depths of 30 to Som, Wtrile in<br />
fiustrrlia the range i5 O to 8Om (Bronn,<br />
1986) and 2 to 200m in Hawaii (Vanunt,<br />
1978). <strong>The</strong> <strong>crabe</strong> seem to exist all over the<br />
nah& plate<strong>au</strong> whære the substrate ir<br />
appropriate, but at varying densities.<br />
IV. [XIRENT RESEARCH AND FSRST RESUtTS<br />
Catch md d+wt (number of hoopnet acts)<br />
are kept by the SFA, which ir also<br />
conducting a biological sampling progrman<br />
in order to determine the population<br />
charactwistlcr. fable 2 gives prclfninary<br />
results, comparad to those obtaained in<br />
Austral i a and Hawai i.<br />
V. THE AUSTRALICHJ AND HMAIICUJ FISHERIES<br />
F.? Stætictical sampling of the Uduriisn fishery<br />
strrtd in 1950. Maximum -annual catches<br />
m œ ' recorded in 1968 (18.8t) and 1972<br />
(29.2tJ. 3 to 4 boats are engaged part time<br />
in t'he +irhuy. <strong>The</strong> crabs are kept alive in<br />
*11a (mortality rate under W.), and sold at<br />
prices ranging from $7 to *lO/kg (1985)Qz<br />
Stocks do not æpptar overexploited <strong>des</strong>pite a<<br />
large warts fishery; Snrrdloff (1979%<br />
suggests an PtSY of 70t/year. , .--<br />
T h Austrrl i en ti aheri es of Queenal and and<br />
New South Maler are more recent (1970) and<br />
much largw, &th annual catches of the<br />
order of SOOt (Bronn, 1986). Pricer range<br />
from USS4 - S/kg. <strong>The</strong> fleet is compared of<br />
6 - 7171 outboard-propelled craft, using<br />
several lines of 20 traps. <strong>The</strong> fishery is<br />
not seasanal and catch rates are high,<br />
averaging 4.3 saleable crabs per net set-<br />
Export of crabs to Hawaii is envisaged at<br />
thi,s time. .<br />
. z<br />
IRecmendati ais - 1 egi 81 ati on and its<br />
results in the 2 cwntries:<br />
CI minimum size l i m i t is applied both in<br />
Hawaii (95", posterior carapace margin to<br />
right æye stalk) and in Australia (100mm).<br />
Versant (1978) suggests a close season for<br />
females during the reproductive period<br />
(summer), rather than limiting fishing<br />
ef f art. In both countries, as in<br />
<strong>Seychelles</strong>, fishing berried females is<br />
prohibited. No attcmpt is made to control<br />
mesh sirca, as trials have demonstrated that<br />
there is little relationship between meaty"<br />
size and the size o+ crabs c<strong>au</strong>ght.<br />
w<br />
Jn Hawaii, the high mortality among crab,<br />
releasee if legs are broken off uhile<br />
unmeshing them (70% mbrtality for one broken<br />
leg - Onizuka, 1972) we5 publicised among<br />
fishermen.<br />
t<br />
u1<br />
Co
Saison de ponte: et& (dec-janv)<br />
Reproductive seasoni summer ,I<br />
Poids moyen d'un <strong>crabe</strong>: O. 45 kg,<br />
*an weight per crab:<br />
Taille moyenne mile: 103mm I<br />
Mean size, male:<br />
Tai 11 e cayenne f emel 1 e:<br />
Mean size, female: . 88"<br />
I<br />
Tai 1 le h maturi th' sexuel 1 e:<br />
Size at sexual maturityi<br />
tndl elmal e: -<br />
femelle/female: -<br />
BIBLIOGRAPHIE<br />
&te<br />
summer<br />
-<br />
&t& (nov-f ev)<br />
summmer<br />
BSmm 105"<br />
ao"<br />
99"<br />
75mm<br />
89"<br />
-<br />
70mm<br />
mWN, I. U., 1985. <strong>The</strong> Hawaian kona crab fishery. Study tour report (mimeo),<br />
Pueensland Dpt of primary ind. Brisbane.<br />
BROWN, I- W., 1986. South Queensland's spanner crabs - a growing fishery.<br />
Austrlian fisharias - Oct 86.<br />
ONIZWA, E. W., 1972. Management and deveropment investigations of, the kona crab,<br />
Ranina canina, Linnaeus, .final Report, Division of Fish and<br />
game, Department of <strong>La</strong>nd and Natural ressources, State of<br />
Hawaii, Honolulu, 2Bpp. .<br />
RATCLIFFE, C., 1976. A report on the results of preliminary fishing investigations<br />
West Coast Mahe, <strong>Seychelles</strong> 1973/1976. ' Hinistry for<br />
Agri cul ture. Seychel 1 es<br />
SWERM-OFF, S. N.,197?. Hawaii Fisheries Development Plan. Dapt <strong>La</strong>nd 7 Nat. Res.<br />
(Hawaii) publn, 297pp.<br />
VANSANT. J.P., 1978. A survey. of the hawaim kana crab fishery unpubl: tl. SC.<br />
thesis, Univ. Hawaii 52PP.<br />
. i
moyenne est<br />
19861. Les<br />
USS/kg- <strong>La</strong><br />
puisque la production annuelle<br />
d'environ 500 tonnes (Brown,<br />
prix pratiques sont de 4 a 5<br />
flottille est constituCe de<br />
petites unites de 6 A 7. equipeas de moteur<br />
hors-bord, utilisant plusieurs filibres de<br />
20 balances. Les captures sont peu<br />
saisonnieres et les t<strong>au</strong>x de captures eleves:<br />
4,3 <strong>crabe</strong>s commercialisables par balance.<br />
Un marche d'exploitation vers Hawaii est a<br />
1 'etude.<br />
Reco o a an dati on - legislation et<br />
resultats obenus dans ces 2 Pays<br />
Une taille limite est appliquee Hawaii<br />
(95Rm) Comme tn Australie (100~~ : longueur<br />
bord posterieur de la czrapace - cavitt!<br />
orbitale droite). Versant (1978) pr'oposc<br />
une interdiction de peche <strong>des</strong> femelles<br />
pendant la periode de reproduction tetel<br />
plutfit que de. controler l'effort de phche<br />
pour proteger la population. Dans ces deux<br />
Pays, ainsi qu'<strong>au</strong>x <strong>Seychelles</strong>, la peche <strong>des</strong><br />
femelles grainees est interdite. Il<br />
n'c'xistc pas de- rPglementation precise quant<br />
d la taille minimale <strong>des</strong> eaillrs de filets,<br />
<strong>des</strong> essais ayant ~0ritr8 que la taille <strong>des</strong><br />
les t<strong>au</strong>x- de<br />
les <strong>des</strong> <strong>crabe</strong>s<br />
railles ;I SinflucnGait pis<br />
capture et. trPs peu les tai<br />
capturbs.<br />
Une campagne d'inforration<br />
. H<strong>au</strong>üii pour sensibiiiser les<br />
fait que la aortalit4 <strong>des</strong><br />
acgmente . tres fortewent si<br />
a t!tB menee a<br />
pechectrs sur le<br />
<strong>crabe</strong>s relacht5s<br />
les pattes du<br />
<strong>crabe</strong> sont alimecs ou cassers lors du<br />
dewaillage (cortalitc! de 70% po.ur 2 patte<br />
entiere casseel ION;'ZUKA, 19721,<br />
ONlZUkA (1972) a montre que les aigrations<br />
de ce <strong>crabe</strong> scnt nulles et qu'il n'existe<br />
pas de melange de populations d l'agc<br />
adulte. Les metho<strong>des</strong> d'evaluation de ¡'age<br />
par progression Rodale ont toute dchoubes,<br />
seul le marquage a donRe les resultats<br />
Suivants: croissance de 9-3. par mue pour<br />
un male adulte et de 7.5.~ pour une femelle.<br />
CONCLUSIONS<br />
Des ressources en <strong>crabe</strong>s <strong>girafe</strong> sont<br />
prbbablement prpsentes dans de nombreux pays<br />
de 1 'ocean Indien Uccidental. <strong>La</strong> simplacite<br />
de la techniquede peche et la h<strong>au</strong>te valeur<br />
commerciale de ce crustace sont <strong>au</strong>tant de<br />
motifs pour la prospection de cette<br />
ressource que d 'atobts pour son<br />
de v e 1 o p pe m en t.<br />
VI. CONCLUSIONS<br />
Kona crab resources are most probably<br />
present in the waters of many western Indian<br />
Ocean countries. <strong>The</strong> ease of fishing and<br />
high commercial value of this crustacean are<br />
strong motivations for prospecting this<br />
resource aand developing fisheries.<br />
Onizuka (1972) demonstrated that this;<br />
species does not migrate, and there is'<br />
little intermixing in adult poplations. ' All<br />
attempts to date at age determination from<br />
modal size progression have failed, the only<br />
stock size estimates coming from tagging<br />
studies. . T,hese have. eqtabl *shed a_ gronth<br />
per mpult of 9.9". for males and 7.5m for<br />
f emal es.<br />
. .<br />
. . .<br />
Chabe Gihn& maieet? Kona Crab meshed<br />
danb Cahhetd / meshed in a hoopnet<br />
Tab. 1 : Captures mensuelles de <strong>crabe</strong>s <strong>girafe</strong> (R. ranina) <strong>au</strong>x<br />
<strong>Seychelles</strong> - Prospution et essais romrnerci<strong>au</strong>x (en tonnes)<br />
Monthly catches of Kona ceab' in <strong>Seychelles</strong> - research and<br />
commercial fishing (in tonnes)<br />
4<br />
3<br />
Mi<br />
-.<br />
_.
os .<br />
Saison de ponte: et& (dec-janv)<br />
Reproductive season: <strong>au</strong>mer<br />
Poids moyen d'un <strong>crabe</strong>s<br />
ban weight per crab:<br />
Tai 11 e moyenne male:<br />
Mean size, male:<br />
Tai 11 e moyenne f emel 1 e:<br />
Mean size, female:<br />
L.<br />
Taille h maturit&. sexuelle:<br />
Size at sexual maturity8<br />
mal elmal e:<br />
f emel le/f emal e:<br />
¡+te<br />
summer<br />
0.45 kg. -<br />
103mm<br />
BIBLIOGRAPHIE<br />
&te (nov-f ev)<br />
eummmec<br />
8Smm 105mm<br />
80"<br />
99"<br />
75mm<br />
8?mm<br />
-<br />
70mm<br />
E@3WJN, I. W., 1985. <strong>The</strong> Hawaian kana crab fishery. Study tour report (mimeo),<br />
Queensland Dpt of primary ind. Brisbane.<br />
BROWN, I. W., 1986. South Queensland's spanner crabs - a growing fishery.<br />
Austrlian fisheries - Oct 86.<br />
. !<br />
ONIZUKA, E. W., 1972. Management and devdopment investigations of the kona crab,<br />
Ranina raninr, Linnaeus, !Final Report, Division of Fish and<br />
game, Department of <strong>La</strong>nd and Natural ressources, State of<br />
Hawaii, Honolulu, 28pp. .<br />
RATCLIFFE, C., 1976. A repart on the results of preliminary fishing investigations<br />
West Coast Plah&, <strong>Seychelles</strong> 1973/1976. Ministry for<br />
Agri cul ture. Scychel les<br />
SWERDLOFF, S. N., 1979. Hawaii Fisheries Development Plan. Dept <strong>La</strong>nd 7 Nat. Res.<br />
(Hanaiil publn, 297pp-<br />
VANSANT, J.P., 1978. A survey, of the hawaian kona crab fishery unpubl.' M. SC.<br />
thesis, Univ. Hawaii 52PP-<br />
w<br />
V<br />
r)
COMORES- KENYA-MADAGASCAR-MAUR IT1 US-MOZAMB I QUE-SEYCHELLES- SOMALI A-TANZAN I A<br />
SWIO Fisheries<br />
TRAINI BATEAU ECOLE 'my'<br />
A quarterly publication of the Project for the<br />
Development and Management of Fisheries in the<br />
Southwest Indian Ocean, P.O.- Box 487, VICTORIA<br />
Mahé, <strong>Seychelles</strong><br />
JUNE 1987 JUIN<br />
RAF/79/065<br />
e<br />
W<br />
-:a<br />
. r: h<br />
w<br />
. m<br />
N