Powell, C.B.

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Occurrence of the Indo-Pacijic prawn 
Macrobrachium equidens in West Africa 
(Crustacea, Decapoda, Palaemonidae) 
c:. R. POWELL (1) 
Mac.rolmchium equidens is recded for the first time from dtlanfic waters. The species fkst nppewed il1 1981 
collections frotn ihe Bonny River (eastern Niger Delta, Gulf of Guinea) tohere it is nom abundant. If mas net found 
during similar collecting in 1980, and may be an erotic species introduced recetdby b!y shipping frafic. 
Thc knouts Nigerian disiribution of M. equidens is mapped. It has been found only in waters of aborri 1.5-30 ppi 
salinifrl. In east and soulhern Africa ii occurs ai lorver salinities, mhich in Nigeria are occrrpied by indigennus species 
of Macrobrachium. Interspecific competif ion maly be involved. 
I(EY WORDS : Shrimp - Macrobrachium - Introduction - Competition - Distribut-ion - Zoogeography - 
Salinity - Est.uary - INigeria. 
PRÉSENCE EN AFRIQUE DE L'OUEST DE LA CREVETTE INDO-PACIFIQUE 3Irc~robrachiurrl equidens 
(CRUHTACEA DECAPODA PALAEBIONIDES) 
La crevetfe Macrobrachium equidens, anférieuremenl inconnue dans l’dtlnntiqur, est signalée au Nigeria. 
Elle a fait sa premiPre apparition en 1981, parmi les récoltes faites depuis 1980 dans la rioiere Bonny (Delta du 
Niger, Golfe de Guinée); et elle y est devenue assez abondanfe. On considére qu’il s’agil d’une espdce exotique, intro- 
dutte récemment par le trafic maritime. 
Dans le delfa du Niger, M. equidens se trouve uniquement dans des eaux: de salinité très ilevèe (entre 15-30 g/l 
appro~itnativement). Mais en Afrique orientale et du sud, l’espèce habite des eaux: moins salles otu mètne douces. 
Au Nigeria ces eaux sont occupées par les espèces indigenes telles que M. vollenhovenii ef M. mac:robrachion. On 
se demande s’il y a exclusion compétitive. 
MOTS-CLÉ;S : Crevette - Afacrobrtrchium - Int.roduct.ion - Compét-it-ion - R+artit.ion - Zoogrégraphie - 
Salinité - Estxaire - Nigel,ia. 
1. INTRODUCTION showed the snecies to be common further inland. at 
In 198‘2 1 reported an apparently undescribed 
species of Macrobrachirrm from Bonny on the toast 
of t.he Niger Delta (POWELL, 1983). On seeing the 
manusc.ript of that paper, Prof. L. B. HOLTHUIS 
(in 1%. 17 Februarv 19821 t,entativelv identified the 
1 
sites from which it was previously unknown. 
Event,ually a fully developed male was obtained, 
which allowed Prof. ~OLTHUIM t.o confirrn Ilis 
ident,ification (in litf., 20 L)ec.ernber 1982). 
The information presented below indicates t,hat 
” Y 
species as the Indo-Pacifie Macrobrachiutn equidens the species is truly exot.ic, and colonized t.he eastern 
(DAN.~, 1853). Field work during the rest of 1982 Niger Delta nround 1980-81. 
(1) Depi of Zooloyy, University of Pori Hurcourf, PMB 5325, Porl liarcourt, Nigcrin. 
Res. Il!]drobiol. irop. 19 (2): 76-79 (19X6). 
2? C. B. POWELL 
PORT 6% 
HARCOURT 
., 
0 no Macrobrachium 
0 M. macrobrachion 
equidens 
a 
FIG. 1. - »istriboi.ion of Macrobrachium equidens and 121. macrobrachion in the Bonny River system in (a) 1980 and (fi) 1981-81. 
Inset shows other 1981-84 records for Al. equidens, mentioned in the text 
K6parfifion de Macrobracthium eyuidcns and $1. macrobrachion dans le sysfdme Bonny, pendant (a) 1980 ef (6) 1981-S& La pefife 
earfe prbenfe les aubes rttcolfes de 1981-83, cife’es dan8 le fexfa 
2. KEVIEW C)E’ THE SPECIES INDO-PXCIFIC: 
I~ISTHIBIJTION AND ECOLOGY 
2.1. Distribution 
.II. fvpidms is a tropical species, occurring natural- 
1y froru Aust.ralasia (New Britain and New Cale- 
donia: HOLTHUIS, 1980) west.wards through south- 
easf; Xsia and southrrn India to East, Africa. In 
East. Africa it. is known from Kenya (BAILEY and 
CRICHT~N, 1971) southwards to Natal (KENSLEY, 
1981). 
It bas net. been recorded from the relatively well- 
studied temperate wat.ers of sout,hern and sout.h- 
western Africa (cg. LIAY, 1981 and KENSLEY, 1981), 
or t.he Mediterranean. 
2.2. Habitat ecology 
The published literature implies geographic varia- 
tion in the habitat. and salinity preferences of M. 
eyzzidenx. The species appears to favor higher salin- 
ities in the east, and fresh wat,er in the West$ern parts 
of it,s range. 
JOHNSON (1965, 1973) indicates that in Malaysia 
it is primarily a species of polyhaline waters including 
mangrove creeks and prawn ponds. Ne comments 
(1965) that. it “... oc.curs in marine habitats, though 
relatively rare t,here ( HOLTHUIS, 1950; JOHNSON, 
1962a)“. JOHNSON does not list it under oligohaline 
fauna (1973) or freshwater fauna (1967). 
KURIAN and SEBASTIAN (1982) gives its Indian 
(Kerala) habitat. as “fresh and bracl~sh waters”. 
RFI!. Hydrobiol. frop. 19 (2) : 75-79 (1986). 
Alacrobrachinm equiderts IN WEST AFRICA 
i 
! N I G)E j? I A 
I 
1981- 4 
GULF OF GUINEA -cl i 
OE IÇIOE 1 1: 
L u 
In East Afric,a, BAILEP and CRICHTON (1971) 
writ.e: “An essentially brackish water species but 
extending into freshwater.” 
In southern Africa DAY (1951) and KENSLEY (1981) 
both list it, as a freshwat.er speçies. KENSLEY writes 
further that it “ . ..inhabits the lower reaches and 
esiuaries in Natal and southern Mozambique”. 
DAY (1969) stat,es t.hat it “lives among weeds in 
brack water and ascends rivers”, and later (1981) 
refers to it occurring at or tolerating low salinities. 
3. DISTRIBUTION AND ECOLOGY IN NIGERIA 
The salinity of the Bonny River is very stable 
because of the t-mal1 freshwater input. Most of the 
river is tidal; at Aluu the tidal range is 2. meters 
although the water is fresh. NEDECO (1961) records 
surface salinities of 18-20 ppt at Port Harc.ourt 
regardless of season or tide level. Persona1 un- 
FIG. 1. 
published data for the period 1980-86 suggest a 
distinct seasonal variation, but. confirm that, stations 
downstream of Port Harcourt will have salinities 
consistently above 15 ppt. The lowest available 
salinity-range values for Port Harcourt (13-17 ppt 
with one extreme value of 10 ppt) were obtained 
during the late wet season (August-September 1982). 
The dislribution of Macrobrachium in the Bonny 
River in 1980 when ifs shrimp fauna was surveyed 
in detail (POWELL, unpublished) is shown in Figure 
1 (a). Some of the stations for .M. macrobrachion also 
had M. uollenhouenii present. 
The absence of M. equidens cari be acc.epted wit,h 
a high level of confidence because of the number of 
stations, the int,ensit.y of collect,ing efforts, and the 
absence of any other lllarrobrctchium (with which 
M. eqlzidens might have been confused) in stations 
downstream of Port Harcourt. Al1 the c.ollect,ions 
were made at low t.ide, and many stat.ions were 
sampled on several occasions. Those stations which 
Rev. Hydrohiol. fsop. 19 (2) : 7’5-79 (1986). 
7x c. F3. 
later had ,If. equidem present, were sampled during 
t.he period 2. Rlay to 12 August 1980, mostly in May 
(start. of rainy ~eason) when seasonally high salinities 
would occur. The co!leat.ions included the same range 
of hiph-selinity palaemonid species (Palaemorz macrr- 
Irrfrr.s, Pnlaemon elqczns ant-1 Leai2der tenuicorr2is) ~1s 
was fo~md durin<t the 198%XJ collections at. the same 
sites. 
Fiylur 1 (1~) i;hows lhe distribution of l\I. eqzzidzws 
in IHtil-1984 made over the n’iger Delt,a. The records 
?are frorn three rivers: the Escravos, t,he Foreados 
(hoth rrccn~l~ shown on in& maps) and the Bonny. 
The first collection of 111. eyuiderzs was made in 
March 19X1 011 t,he east bank of the Bonny River 
br+ween Bonny Town and the SW. The specimens 
were takrn by hand net. from subtidal crevices in 
the peat bar& of the canal out for the Bonny Lique- 
flrd flatural C;M Projrct. at, Finima. The salinity of 
the nite woiild approximate that of sea water at. t.hr 
river rriouth. 
Al1 subsequrnt collect.ions of M. eyzzidrns bave bren 
from hiyh salinity w-at.ers (15 ppt cor more) and asso- 
ciatrc-l wit-h steep eroding peat. banks. The colleations 
us11ally aIso incluclrtl hi&salinity palaemonids 
suc11 :AS .Pnlww2oi2 muczzlaI7zs, Palaemoli elegflz2s and 
LwmEcr fenrrirorz2is. but net low-salinity forms surh 
ils Pnltr6wioizefrs czfi*icarizzs and Palnemozz sp. A (of 
PCWELL, 1 !Fa). 
-1. DISCUSSION 
I’l~e indigc~nous apecies AI. macrobrachior2 and 
-11. zrollrnhc)zrpr2ii bot,11 bave sa1init.y ranges from fresh 
POWELL 
water t,o 15 ppt. (Powixr~, 1983). ;II. ryzzidcr2s is not 
ltnown from such low salinities in the Bonny River, 
even though rrrost, of the Indo-Pac.iflc literature 
suggests it should occur there. 
Possibly M. eyzzidrrzs is excluded from the lower 
salinity zones by cornpetition from the morpho- 
logic.ally similar M. mncrobrachi»rz. Alt,ernatively, 
perhaps there is geographic variat.ion in the salinity 
preference of .flr. eyuiderzs in the Indo-Paciflc - hence 
the discrepaney in puhlished acxounts of ite salinit,y 
range - end the Nigerian populat.ion is derived from 
high-salinity stock. - 
One hopes t-bat. worlrers in other troyieal Atlantic 
areas Will watch for the appearance of M. eyzzidens, 
and for evidence of its competit.ive relations with 
indiqenous species. Its large size, and t,he striking 
yellow-to-red and black mot.tling on its chelipeds, 
makes it rather conspicuous. So far, no records are 
availnble outside the Niger Delta. Occasional samples 
of fl/lncrob2~achiunz submitted t.o me for identitlcat,ion 
from the Lagos and Calabar areas over tbe past 
5 years bave contained only indigenous species. 
M,~RI~C;HAE (19H2) reports only Al. volle~2hoveiiii and 
M. niucrobrachion from Lagos Lagoon. 
The mode of introduction cannot be t,raced, but 
there has been ample opportunity through shipping 
trafic t.o Port. Harcourt. and more especially through 
the ballast. wat.er of oil tanker t.rafYie to Bonny and 
other Niger-Ljrlta oil terminals. 
.IIunuscrit accepté pur le Comité dc Ridactitrn le 2.9 juillet 1.986 
B.&rr.e~ (Ft. G.) ami CRKHTON (X.), 1971. - Freshwatw 
prawns of the grnus dIztrcrobrachiun2 (Cïustac~s : 
P:~laemonitlwe) in East .\frica, with a key for t.heir 
identification and notes «II their exploitation. .JournaZ 
of ihc East =Ifrictr Nafurtrl Tfistorty S%cie$ and National 
.Iluncum, 28, No. 120, 8 p. 
Dau 1.1. Il.), 196!J. -- A gzzide to Atarine Lit@e on Soufh African 
Shores. Bnlkama, Rotterdam, 300 p. 
DAY (J. H.), 19Pl. - Estnarine Ecotogy urith parficular 
refcrfnce fo sonthcrn dfricn. Balkema, Rotterdam, 411 p. 
HOLTHWS (L. B.), 1980. - PAO Species Cat,alogue. Vol. 1. 
C;hrimps ami prawm of thc morld. An annobtrd 
catalogue of species of interest to fisheries. Fi-10 
Fishrries Stynopsis No. 12.i. Vol. 1 : 261 p. 
.TC)HNSCIN iD. S.), 1962. - A synopsis of the Decapoda Caridea 
and Stenopndidea of Singapore, with notes on their 
distrihlttion and a k~y t.o theçenera of Çoridea occurring 
Rerr. Hydrobiol. trop. 19 (2) : 7%79 (7986). 
in hlatayan ~vvaters. Bulletin of fhr Nufionnl A~Iuseum 
of Singapore, 30 : U-79, Pl. 2. 
JOHNSON (D. S.), 1965. - .I reviem of the Brackish ‘Ivatcr 
Prawns of Malaya. Bnllefin of thr Nafionnl Museum 
of Singapore IVe. 33, Part 2, p. 7-11. 
JOHNSOK (LJ. S.), 1967. - Some fact,ors influencing t,he 
distribution of freshnater prawns in Balaya. Pro- 
eeedings of fhe Symposizrm on Crustncea, Mnrine 
BioIogicnZ dssocinfion of India, V«l. 1 : 418-133. 
JOHNSOS (D. S.), 1973. - Brackish waters. Chapter 8 (p. 12% 
139) in Chimn~, S. H. (ed.1, Animal ILfe and Nafure 
in Singaporr. Singapore Dniversity Press. 
KENSLEY (B.j, 1981. - On t.he Zoogeography of Southern 
African Drcapod Crusbcea, with a Distributional 
Chccklist of the Species. Smithsonian Confribufions 
lo Zoologg, Number 338, p. iii + 64. 
Macrobraclrinm equidens IN WEST AFRICA 79 
KURIAN (C. V.) and SEBASTIAN (V. 0.). 1982. - Prawns 
and Prawn Fisheries of India. Second Edit.ion. Hin- 
dustan Publishing Corporation, Delhi, 286 p. 
NEDECO, 1961. - The Il*afers of fhe Niger Deffn. Second 
Revised Edition. Netherlands Engineering Consultants, 
The Hagbe, 31T p. 
BIARIOGHAE (1. E.), 1982. - Notes on the biology and 
dist.ribution of Macrobrachium vollenhovenii and 
Macrobrachium macrobrachion in the Lagos Lagoon 
(Crust.acea, Decapoda, Palaemonidae). Reoue de Zoo- 
fogie africaine, 96 (3) : 493-508. 
POWELL (C. B.j, 1983. - Fresh and hrackish water shrimps 
of economic importance in the Niger Delta, p. 254285 
in : Proreedings of fhe 2nd dnnual Conference of fhe 
Fisheries Sociefy of Niyerin. Kainji Lake Hesearch 
Instit.ute, NPW Bussa, Nigeria, vi + 295 p., ISBN 97% 
177-010-4. 
Heu. Hgdrohiol. trop. 19 (8) : 75-79 (1986). 


Occurrence of the Indo-Pacific prawn Macrobrachium equidens in West Africa (Crustacea, Decapoda, Palaemonidae)

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