Genetic variation in wild populations 
and farmed stocks of Nile tilapia 
(Oreochromis niloticus) in Madagascar
Monique Ravakarivelo1,2  Elodie Pepey3,4  John A. H. Benzie5,6  
Noromalala Raminosoa1  Harentsoaniaina Rasamoelina1  
Olivier Mikolasek3,4  Hugues de Verdal3,4,6*
Keywords Summary
Oreochromis niloticus, fish, tilapia, Four farmed stocks and four wild populations of Nile tilapia (Oreochromis niloti-
animal population, genetic variation, cus), which was first introduced to Madagascar sixty years ago, were assayed 
genetic structures, Madagascar for genetic variation at nine microsatellite loci to determine levels of genetic 
diversity within populations and genetic relationships between them. Allelic 
Submitted: 7 June 2018 diversity overlapped with that found in previously sampled populations else-
Accepted: 5 September 2019 where in Africa. There was no evidence of deviations from allele frequencies 
Published: 30 September 2019 expected under conditions of Hardy-Weinberg equilibrium or of inbreeding in 
DOI: 10.19182/remvt.31780
studied populations. Three distinct clusters of genotypes provided evidence of 
three separate introductions (from Egypt and Mauritius in 1956, and from Japan 
in 2011), and the occurrence of genotypes from more than one cluster within 
a single population provided evidence of their mixing. There were significant 
differences between populations which were not from the same environment 
(wild or farmed) or were not geographically related. Wild populations may be a 
valuable resource to support further development of farmed stocks from the per-
spective of genetic diversity.
■ How to quote this article: Ravakarivelo M., Pepey E., Benzie J.A.H., Raminosoa N., Rasamoelina 
H., Mikolasek O., de Verdal H., 2019. Genetic variation in wild populations and farmed stocks of Nile 
tilapia (Oreochromis niloticus) in Madagascar. Rev. Elev. Med. Vet. Pays Trop., 72 (3): 101-106, doi: 
10.19182/remvt.31780
■ INTRODUCTION tilapia has become one of the major fish species consumed in the 
country. 
Nile tilapia, Oreochromis niloticus, is the second most frequently 
farmed fish worldwide after carps (FAO, 2014). World production is Although freshwater aquaculture in Madagascar is dominated by 
expected to attain 7.3 million tons a year in 2030 (FAO, 2014) with carps and tilapias, production has remained low (3763 tons, FAO, 
a market value of around 5 billion USD. Nile tilapia was introduced 2010-2019). One possible contributory factor to the low production 
to Madagascar in 1956 from Egypt and Mauritius (Kiener, 1963; is the potential low genetic variability and inbreeding in the wild 
Moreau, 1988). Wild populations of this species were rapidly estab- populations themselves or in the farmed stocks derived from them, 
lished and are now widely spread in natural lakes and rivers. Nile or both. In the past, although large numbers of fish may have been 
introduced, their genetic diversity was unknown and potentially 
limited. In addition, a small number of fish is used as breeders to 
develop the founder stock in individual farms in Madagascar. These 
1. FOFIFA, DRZVP, Ampandrianomby, Antananarivo, Madagascar.
2. Department of Animal Biology, University of Antananarivo, Antananarivo, practices are known to reduce genetic variability, increase inbreed-
Madagascar. ing and thus reduce fish growth performance (Chevassus, 1989; Fer-
3. CIRAD, UMR ISEM, TA B-116/16, 73 rue Jean-François Breton,  guson et al., 1985). 
34398 Montpellier Cedex 5, France.
4. SEM, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France. Rakotoambinima et al. (2009) noted the importance of estimating the 
5. School of Biological Earth and Environmental Sciences, University College genetic variability of this species about 50 years after its introduction 
Cork, Cork Ireland. and checking the relationships between wild and farmed fish. Esti-
6. Worldfish, Jalan Batu Maung, Bayan Lepas, Penang, Malaysia. mates of genetic diversity are essential to manage the biodiversity of 
* Corresponding author local resources (Beaumont and Hoare, 2003; Romana-Eguia et al., 
Tel.: +33 4 67 61 44 67; email: hugues.de_verdal@cirad.fr 2005) and are required to assess the soundness (sufficient variability 
and lack of inbreeding) of the stocks for the development of aqua-
  https://creativecommons.org/licenses/by/4.0/ culture (Desvignes et al., 2001; Thai et al., 2006). In the last decade 
101
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2019, 72 (3) : 101-106 ■ PRODUCTIONS ANIMALES ET PRODUITS ANIMAUX
Genetic variation in Nile tilapia in Madagascar
authorities and fish farmers increased genetic mixing through 
exchanges of breeders between farms and controlled restocking 
in different locations, in attempts to avoid diversity reduction and 
inbreeding. New strains of Nile tilapias were also introduced in 2011 
and 2013 from Japan and Thailand, respectively, with a production 
objective. To date, however, there has been no direct measurement of 
the genetic variability of wild and farmed stocks. 
The aims of the present study were 1) to assess the genetic structure 
of wild populations and farmed stocks of Nile tilapia using micro-
satellites to understand the present genetic diversity of Nile tilapia 
in Madagascar, and 2) to assess whether the inbreeding levels could 
affect fish farming development of this species in the country.
■ MATERIALS AND METHODS
Samples
A total of 306 samples from wild populations and farmed stocks 
were collected between 2011 and 2012 from eight locations in seven 
regions in Madagascar (ALA: Alaotra Mangoro; ANA: Analamanga; 
ATS: Atsimo-Andrefana; BOE: Boeny; BON: Bongolava; ITA: Itasy; 
VAK: Vakinankaratra) (Figure 1). Fish were sampled from four farms 
maintaining breeding stock, and from natural locations known to 
have wild populations. Although we aimed at sampling 50 fish per 
location, the low number of fish available at some sites and the dif-
ficulties met with in tissue preservation explained the lower sample 
sizes obtained for some populations (Table I). A small piece of dorsal 
fin was cut from each individual fish sampled, stored in 95% ethanol 
and exported to France for DNA analyses. 
DNA extraction Figure 1: Collection sites for 
wild (black background) and 
Genomic DNA extraction was performed at the French Agricultural farmed (white background) 
Research Centre for International Development (CIRAD), Montpel- populations in Madagascar 
regions. BOE: Boeny; ALA: 
lier, France, with two commercial kits. Genomic DNA from ALA, Alaotra Mangoro; ANA: Ana-
ITA wild (ITAw), ITA farmed (ITAf), VAK and ANA populations was lamanga; BON: Bongolava; 
extracted using Chelex 100 resin extraction kit (Bio-Rad, France) as a ITA: Itasy; VAK: Vakinankara-
rapid and simple technique for extracting DNA with a reduced potential tra; ATS: Atsimo-Andrefana.
Table I
Sample size (n), average number of alleles per locus (A), number of private alleles per population (pA), observed 
heterozygosity (H0), expected heterozygosity (HE) and inbreeding coefficient (FIS) based on the average of nine 
polymorphic microsatellite loci for eight Nile tilapia populations in Madagascar
Population n A pA H0 HE H0/HE FIS
Farmed
BOE 27 3.78   7 0.54 0.55 0.98 -0.16
ANA 25 5.22   1 0.67 0.70 0.95   0.07
BON 24 5.22   2 0.58 0.64 0.90   0.25
ITAf 50 8.78 17 0.69 0.74 0.93   0.05
Mean 31.5 5.75 6.75 0.62 0.66 0.94   0.05
Wild
ALA 50 5.44   4 0.49 0.49 0.99 -0.18
ITAw 50 8.89 29 0.66 0.77 0.86   0.03
VAK 50 3.33   1 0.55 0.54 1.02   0.04
ATS 30 4.56   4 0.59 0.59 1.00 -0.06
Mean 45 5.56      9.5 0.57 0.60 0.97 -0.04
Populations in each group are listed from the most northern to the most southern sites. BOE: Boeny; ANA: Analamanga; BON: Bongolava; ITA: Itasy; ALA: Alaotra Man-
goro; VAK: Vakinankaratra; ATS: Atsimo-Andrefana; w: wild; f: farmed; H0/HE and FIS are not significantly different from 1 and 0, respectively.
102
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2019, 72 (3) : 101-106 ■ PRODUCTIONS ANIMALES ET PRODUITS ANIMAUX
Variation génétique du tilapia du Nil à Madagascar
for contamination given the low number of steps and reagents added probability of K, the method developed by Evanno et al. (2005) was 
(Walsh et al., 1991; Musapa et al., 2013). Fin clip samples were placed in followed, plotting values of LnP(D) (the log probability of data) for each 
96 well plates with 150 µl of Chelex solution at 5% already prepared and K and estimating the delta K (ΔK) statistics, based on the rate of change 
stirred. Then 150 µl of TE buffer 1X (containing Tris EDTA) was added in LnP(D) between two successive K values. 
to each well followed by 10 µl of proteinase K at 10 mg.ml-1. Plates were 
incubated in a thermocycler for 2 h at 55°C, then 10 min at 96°C accord-
ing to the manufacturer’s instructions. However, the DNA in some sam- ■ RESULTS
ples was degraded and that from ATS, BON and BOE populations was 
extracted using Wizard Genomic DNA purification kit (Promega, USA) Genetic diversity
according to the manufacturer’s instructions. After extraction with 
either technique, the DNA was stored at -20°C until processing. Estimates of microsatellite variations in the eight Nile tilapia popula-
tions (n = 306) are presented in Table I. The average number of alleles 
per locus ranged from 3.33 to 8.89 and was not significantly different 
Microsatellite analyses between wild populations and farmed stocks. In the same way, the 
The polymerase chain reaction (PCR) was used to amplify DNA frag- number of private alleles was not significantly different between wild 
ments containing microsatellites that differed in number repetitions populations and farmed stocks. Wild populations and farmed stocks 
of the repeated motifs. The nine microsatellites used were developed from Itasy, ITAw and ITAf, respectively, showed a higher number of 
from the Oreochromis niloticus genomic DNA library produced by private alleles than the other populations. 
Lee and Kocher (1996) (Supplementary Material I). Among the eight populations collected, observed heterozygosity was 
Genotypes were obtained by PCR amplification with indirect fluores- the lowest in ALA (0.49) and the highest in ITAf (0.69). In every 
cent tagging (Schuelke, 2000; Bezault et al., 2011). With this approach, population, observed and expected heterozygosities were not sig-
for each locus the F primer was elongated in his 5’ extremity by a 19 nificantly different when the average across microsatellite loci was 
base-pair (bp) M13 sequence (5’-CACGACGTTGTAAAACGAC-3’) considered, which indicates general conformation to expectations of 
and a primer labeled with appropriate fluorescent dyes, specific to the Hardy-Weinberg equilibrium. Individual loci did not show deviation 
M13 sequence, was also incorporated to the PCR reaction. from Hardy-Weinberg equilibrium (data not shown). Globally, there 
were no significant differences between the observed heterozygos-
The PCR amplification was performed in a 20-µl reaction volume ities in wild populations and farmed stocks. F  estimated for each 
containing 25 ng of template DNA, 80 nM of F primer, 100 nM of IS
population was not significantly different from zero, indicating that 
R primer, 0.1 pM IRDye 700 or 8000-labeled universal M13 primer, none of the eight populations collected had significant inbreeding. 
2 mM of dNTPs, 0.5 U of Taq DNA polymerase, 2 µl of 10X reaction 
buffer (10 mM Tris-HCl pH 9, 50 mM KCl, 1.5 mM MgCl2, 0.1% 
Triton X100, 0.2 mg/ml BSA). The same composition of the PCR Population structure
mixture was used in amplification of all microsatellites investigated Significant population differentiation was observed at the global 
in the present study. level, with 17.7 % of overall genetic variation attributed to differences 
Thermal cycling conditions consisted of enzyme activation at 94°C for between populations (i.e. FST). Population pairwise FST ranged from 
5°C, followed by 10 cycles of touchdown starting at the annealing tem- 0.038 to 0.379 (Table II). BOE population showed high differentiation 
perature + 5°C with a decrease of 0.5°C at each cycle during 10 cycles. from all the other populations, with FST values ranging from 0.225 to 
Then 30 cycles of amplification were done with the annealing tem- 0.379. The wild ALA population was differentiated from the other 
perature, specific for each couple of primers. A final extension step three wild populations with FST values ranging from 0.201 to 0.335. 
was performed at 72°C for 10 min, followed by a final hold at 15°C. A moderate differentiation was estimated between the farmed BON 
stock and three of the wild populations (not ITAw).
Samples were run on 7% denaturing acrylamide gel using 4300 DNA 
Analyzer LI-COR (Li-color Bioscience, USA). Allele size was esti- There was no indication showing that the farmed stocks as a group 
mated using SAGA GT Client Software (Li-color Bioscience) by com- were more differentiated from the wild populations as a group than 
paring the samples to molecular weight standards (from 71 to 363 bp).
Data analyses Table II
The number of alleles, observed and expected heterozygosity (Nei, Pairwise genetic variation (FST) values between sites 
1987) were calculated for each population using GENEPOP soft- sampled for Nile tilapia in Madagascar
ware (version 4.1, Rousset 2008). The Hardy-Weinberg equilibrium 
was tested using GENEPOP. Alleles were classified as private alleles Farm Wild
when they were observed only in one population. The same software 
was used to determine the proportion of genetic variation partitioned ANA BON ITAf ALA ITAw VAK ATS
among populations (FST). Arlequin software (version 3.5, Excoffier and BOE 0.264 0.291 0.225 0.379 0.243 0.364 0.301
Lischer, 2010) was used to determine the proportion of genetic vari-
ation partitioned within populations (FIS). Mann-Whitney tests were ANA 0.040 0.038 0.168 0.033 0.108 0.105
used to compare the results of wild populations and farmed stocks. BON 0.068 0.188 0.085 0.168 0.161
ITAf 0.098 0.076 0.169 0.151
To identify different genetic subgroups and to infer the genetic ancestry 
of individual animals to a given population, multi-locus genotypes were ALA 0.201 0.335 0.316
analyzed by a model-based clustering algorithm with the Structure 2.3.4 ITAw 0.114 0.101
software (Pritchard and Donnelly, 2000; Falush et al., 2007). Twenty VAK 0.190
runs of Structure were performed for each K from 1 to 8 (the total num-
ber of populations sampled). We used 100,000 iterations of the Gibbs Populations in each group are listed from the most northern to the most southern 
sites. BOE: Boeny; ANA: Analamanga; BON: Bongolava; ITA: Itasy; ALA: Alaotra 
sampler after a burn-in of 50,000 iterations. To estimate the posterior Mangoro; VAK: Vakinankaratra; ATS: Atsimo-Andrefana; w: wild; f: farmed
103
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2019, 72 (3) : 101-106
Genetic variation in Nile tilapia in Madagascar
populations within each group. If anything, the wild populations same range as those of the present estimations, with on average 5.7 
showed more differentiation from each other than the farmed stocks. alleles per locus, 0.60 observed heterozygosity and -0.04 inbreeding. 
The graph of LnP(D) did not show a clear point of change in the slope Although neither the number of fish introduced at specific times nor 
for any specific K value although minor changes in the slope were details on their genetic constitution (e.g. number of families, number 
visible between K = 3 and K = 4 (Figure 2A). The distribution of ΔK of populations included in the transfer) were known, there were mul-
clearly detected one peak at K = 3, suggesting a higher level of hier- tiple introductions. This, and subsequent mixing of those populations, 
archy at this K (Figure 2B). The structure pattern analyzed for K = 3 including that deliberately undertaken in the last few years, may have 
showed that the BOE population was composed of genotypes from resulted in genetic diversity in individual wild populations not very 
one genetic group (light gray), differentiated from a second genetic far from what is found in other wild populations. 
group (gray) found in the majority of populations, and a third group 
of genotypes most commonly found in ALA and part of ITAf popu- The population structure analysis distinguished three clusters which may 
lations (dark gray) (Figure 3). Genotypes with other than 90% proba- reflect the three known introductions of Nile tilapia in Madagascar (two 
bility of being assigned to one genetic group may indicate a degree of in 1956 and one in 2011). Thai strains were introduced in 2013, after the 
introgression between the three genetic groups. sampling for this study was completed. There was evidence of mixing 
of the three different genetic groupings including that of the latest intro-
duction with the others (e.g. in ITAw and ITAf) and those populations 
■ DISCUSSION showed high allelic diversity. However, much of this high allelic diver-
Wild populations sity was associated with high diversity of private alleles. Other popula-
tions with less evidence of mixing showed measures of genetic diversity 
None of the individual populations showed a deviation from Har- equivalent to other stocks. This suggested that the original introductions 
dy-Weinberg equilibrium or evidence of inbreeding, suggesting the must have had a relatively adequate level of genetic diversity. 
wild populations had reached an equilibrium (if they ever departed 
from it). The introduction of Nile tilapia in 1956 also appears to have The relatively low differentiation between many of the wild popu-
resulted in wild populations, which today have comparable hetero- lations (estimated by the pairwise FST) could be hypothesized by a 
zygosities and allelic diversities as other wild African tilapia popu- potential origin of the Mauritius strain from Egypt. There is no avail-
lations (Bezault et al., 2011; Ndiwa et al., 2014). Mwanja et al. (2010) able data to our knowledge to assess this hypothesis. The differences 
and Angienda et al. (2011) on introduced Nile tilapia in Victoria between the wild populations did not appear to be related to the degree 
Lake, and Gu et al. (2014) on Chinese wild populations estimated the of geographical separation of the populations. For example, ITAw 
genetic structure and gene flow of wild Nile tilapia populations. They showed more differences with ALA although it was closer geograph-
found for O. niloticus a number of alleles per locus ranging from 3.8 ically than ATS, with which it had less differences. It is more likely 
to 8.4, an observed heterozygosity ranging from 0.31 to 0.80, and low that the levels of differentiation reflected the predominant origins of 
inbreeding (FIS) ranging from -0.10 to 0.28. These results are in the the source populations rather than the influence of any other factor. 
Figure 2: Uppermost hierarchical structure of Nile tilapia in Madagascar based on ΔK. A) Estimated likelihood, LnP(D) for values of K 
ranged from one to eight. The mean LnP(D) for each K over 20 runs were represented by a dark circle and each value of the 20 runs by 
a white circle. B) ΔK calculated as Evanno et al. (2005).
Figure 3: Clustering assignment of the eight Nile tilapia populations samples from Madagascar using STRUCTURE with K = 3. Each 
color (light gray, gray and dark gray) represents one cluster. Each vertical line represents one individual, and each color for each line 
represents the membership probability of an individual to a given cluster. 
104
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2019, 72 (3) : 101-106 ■ PRODUCTIONS ANIMALES ET PRODUITS ANIMAUX
Variation génétique du tilapia du Nil à Madagascar
Farmed stocks different from lowland sites. These trials may require a breeding pro-
gram including traits for cold tolerance, or another species of tilapia, 
According to Oswald et al. (2016), there are three main types of tila- e.g. O. mossambicus and O. macrochir have already been introduced 
pia farmers in Madagascar. The first type includes small scale farmers in Madagascar (Oswald et al., 2016). 
who represent the majority of tilapia farmers in the country. They have 
only one pond for reproduction and grow-out, and mainly use fish for 
personal consumption. There is generally no management of the strain, Acknowledgments
and exchanges between farmers are scant. Farmers harvest their fish The authors are most grateful to the Great Regional Technical Plat-
regularly, sell the biggest fish and stock the smallest back to the pond. form (GPTR) core facility for its technical support, especially to R. 
The second type includes farmers who have different ponds for repro- Rivallan (UMR AGAP, CIRAD) for his laboratory assistance during 
duction and grow-out. Fry are produced throughout the hot season and the experiments with the Li-Cor gel sequencer.
sold to grow-out farmers or kept in grow-out ponds. The third type 
includes farmers specializing in fry production. They have an agree- Author contributions statement
ment to produce 100% male fry by hormonal inversion. They produce 
most of the fry used in aquaculture, which are transported over long MR, NR, HR, OM, EP and HdV designed the experiment, MR, NR, 
distances to ponds and cages in lakes. These practices generate a high HR collected the samples, MR and EP analyzed the samples, MR, EP 
level of exchange between farms, and between farmed stocks and wild and HdV performed statistical analyses and drafted the article, JAHB 
populations. This is due to escapees but also to relatively frequent cap- and OM revised the article. All the authors approved the manuscript.
tures of wild populations to renew the breeders used on farms. 
It is important to note that only the biggest Nile tilapia farms were sam- REFERENCES
pled in the present study. None of the small-scale farms were collected Angienda P.O., Lee H.J., Elmer K.R., Abila R., Waindi E.N., Meyer A., 2011. 
because of logistical reasons. This could bias the conclusions but the Genetic structure and gene flow in an endangered native tilapia fish 
larger farms that maintain a separate broodstock population are more (Oreochromis esculentus) compared to invasive Nile tilapia (Oreochromis 
likely than either of the other two to show differentiation from wild niloticus) in Yala swamp, East Africa. Conserv. Genet., 12: 243-255, doi: 
populations, as they usually capture less wild fish for broodstock than 10.1007/s10592-010-0136-2
the other two types. It would be interesting to increase the number of Beaumont R.A., Hoare K., 2003. Biotechnology and genetics in fisheries 
sample locations to have a broader view of the genetic diversity of the and aquaculture. Blackwell Science, Oxford, UK, 202  p., doi: 
10.1002/9780470995198
Nile tilapia in different farming systems in Madagascar. 
Bezault E., Balaresque P., Toguyeni A., Fermon Y., Araki H., Baroiller J.-F., 
As a consequence of this sampling choices, the fish sampled from Rognon X., 2011. Spatial and temporal variation in population genetic 
the farms also showed no deviation of allele frequencies from that structure of wild Nile tilapia (Oreochromis niloticus) across Africa. BMC 
expected under conditions of Hardy-Weinberg Equilibrium or high Genet., 12: 102, doi: 10.1186/1471-2156-12-102
signs of inbreeding indicating that they were either adequately man- Chevassus B., 1989. Aspects génétiques de la constitution de populations 
aged or that insufficient time had elapsed for inbreeding to develop. d’élevage destinées au repeuplement. Bull. Fr. Pêche Piscic., 314  : 146-
These processes would explain the lack of significant genetic differ- 168, doi : 10.1051/kmae:1989010
ences between most farmed stocks and wild populations. Desvignes J.F., Laroche J., Durand J.D., Bouvet Y., 2001. Genetic variability 
in reared stocks of common carp (Cyprinus carpio L.) based on allozymes 
Fish sampled from BOE farm showed a marked differentiation from and microsatellites. Aquaculture, 194: 291-301, doi: 10.1016/s0044-
the other farmed stocks which reflects the recent introduction (2011) 8486(00)00534-2
of the population on that farm from Japan. Material has been sent from Evanno G., Regnaut S., Goudet J., 2005. Detecting the number of clusters of 
that farm to others and to the wild, which is reflected in individual fish individuals using the software STRUCTURE: a simulation study. Mol. Ecol., 
being allocated to the BOE genotype group in ITAf and ITAw. The 14: 2611-2620, doi: 10.1111/j.1365-294x.2005.02553.x
lack of differentiation between most of the farmed stocks and all the Excoffier L., Lischer H.E.L., 2010. Arlequin suite vers. 3.5: A new series of 
wild populations probably shows that farmers use wild populations for programs to perform population genetics analyses under Linux and Windows. 
their farms and exchange fish among themselves. It is interesting to Mol. Ecol. Resour., 10: 564-567, doi: 10.1111/j.1755-0998.2010.02847.x
note that in wild population ITAw (from Itasy Lake) some fish were Falush D., Stephens M., Pritchard J.K., 2007. Inference of population structure 
grouped in the same cluster as BOE, representing fish introduced from using multilocus genotype data: dominant markers and null alleles. Mol. 
Japan in 2011. These results point to the high probability that fish from Ecol. Notes, 7: 574-578, doi: 10.1111/j.1471-8286.2007.01758.x
BOE were stocked in cages in Itasy Lake, and that escapees occurred FAO, 2014. The state of world fisheries and aquaculture. FAO, Rome, Italy
or larvae from BOE hatcheries were used for restocking in Itasy Lake. FAO, 2010-2019. Fisheries Global Information System (FAO-FIGIS). FAO / 
Fisheries and Aquaculture Department, Rome, Italy (www.fao.org/fishery/)
Ferguson M.M., Danzmann R.G., Allendorf F.W., 1985. Developmental 
■ CONCLUSION divergence among hatchery strains of rainbow trout (Salmo gairdneri). I. 
Pure strains. Can. J. Genet. Cytol., 27: 289-297, doi: 10.1139/g85-043
A comprehensive assessment of the multiple impediments to aqua- Gu D., Mu X., Song H., Luo D., Xu M., Luo J., Hu Y., 2014. Genetic diversity 
culture growth and a comprehensive industry strategy are needed of invasive Oreochromis sp. (tilapia) populations in Guangdong province 
in order to fulfill the potential of this growing sector. The present of China using microsatellite markers. Biochem. Syst. Ecol., 55: 198-204, 
results highlight that wild and domestic populations are relatively doi: 10.1016/j.bse.2014.03.035
close genetically. As a consequence, the wild population could be Kiener A., 1963. Poissons, pêche et pisciculture à Madagascar. Centre technique 
a good resource for those facing diversity loss and/or inbreeding in forestier tropical, Nogent-sur-Marne, France, 160 p.
some domestic stocks. Lee W.-J., Kocher T.D., 1996. Microsatellites DNA markers for genetic 
The extent to which wild populations performance is satisfactory with mapping in Oreochromis niloticus. J. Fish Biol. 49: 169-171, doi: 10.1111/
j.1095-8649.1996.tb00014.x
respect to production traits such as growth remains to be evaluated. 
Growth trials should evaluate the performance of Nile tilapia in dif- Moreau J., 1988. Tilapia genetic resources for aquaculture. Madagascar. In: 
Proc. Workshop Tilapia Genetic Resources for Aquaculture (Ed. Pullin 
ferent rearing environments, given that relatively high-altitude sites in R.S.V.). International Center for Living Aquatic Resources Management, 
Madagascar, where temperatures can be cold in winter, are markedly Bangkok, Thailand, 29-32, doi: 10.1016/0044-8486(86)90236-x
105
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2019, 72 (3) : 101-106
Genetic variation in Nile tilapia in Madagascar
Musapa M., Kumwenda T., Mkulama M., Chrishimba S., Norris D.E., Tuma Pritchard M.J.K.S., Donnelly P., 2000. Inference of population structure using 
P.E., Mharakurwa S., 2013. A simple Chelex protocol for DNA extraction microlocus genotype data. Genetics, 155: 945-959
from Anopehles sp. J. Vis. Exp., 71: 3281, doi: 10.3791/3281 Rakotoambinima S., Desprez D., David D.G., Bosc P., Le Roux Y., 2009. 
Mwanja W.M., Kaufman L., Fuerst P.A., 2010. Comparison of the genetic Caractérisation des environnements écologiques et socio-économiques de 
and ecological diversity of the native to the introduced tilapiines la production piscicole continentale à Madagascar. Cah. Outre Mer, 248 : 
(Pisces: Cichlidae), and their population structures in the Lake Victoria 471-488, doi : 10.4000/com.5778
region, East Africa. Aquat. Ecosyst. Health Manag., 13: 442-450,doi: Romana-Eguia M.R.R., Ikeda M., Basiao Z.U., Taniguchi N., 2005. Genetic 
10.1080/14634988.2010.527268 changes during mass selection for growth in Nile tilapia, Oreochromis 
niloticus (L.), assessed by microsatellites. Aquac. Res., 36: 69-78, doi: 
Ndiwa T.C., Nyingi D.W., Agnese J.F., 2014. An important natural genetic 10.1111/j.1365-2109.2004.01185.x
resource of Oreochromis niloticus (Linnaeus, 1758) threatened by 
aquaculture activities in Loboi Drainage, Kenya. PLoS One, 9: e106972, Rousset F., 2008. GENEPOP’007: a complete re-implementation of the 
GENEPOP software for Windows and Linux. Mol. Ecol. Resour., 8: 103-
doi: 10.1371/journal.pone.0106972 106, doi: 10.1111/j.1471-8286.2007.01931.x
Nei M., 1987. Molecular evolutionary genetics. Columbia University Press, Schuelke M., 2000. An economic method for the fluorescent labelling of PCR 
New-York, USA, 512 p., doi: 10.7312/nei-92038 fragments. Nat. Biotechnol., 18: 233-234, doi: 10.1038/72708
Oswald M.R., Ravakarivelo M., Mikolasek O., Rasamoelina H., de Verdal H., Thai B.T., Pham T.A., Austin C.M., 2006. Genetic diversity of common carp in 
Bentz B., Pepey E., et al., 2016. Combining a comprehensive approach Vietnam using direct sequencing and SSCP analysis of the mitochondrial 
to fish-farming systems with assessment of their genetics - from planning DNA control region. Aquaculture, 258: 228-240, doi: 10.1016/j.
to realization. In: Actes projet FSP PARRUR, Recherche interdisciplinaire aquaculture.2006.03.025
pour le développement durable et la biodiversité des espaces ruraux Walsh P.S., Metzger D.A., Higuchi R., 1991. Chelex 100 as a medium for 
malgaches. Application à différentes thématiques de territoire (éds simple extraction of DNA for PCR-based typing from forensic material. 
Duchaufour H., et al.). MYE, Antananarivo, Madagascar, 219-267 Biotechniques, 10: 506-513, doi: 10.2144/000114018
Résumé Resumen
Ravakarivelo M., Pepey E., Benzie J.A.H., Raminosoa N., Ravakarivelo M., Pepey E., Benzie J.A.H., Raminosoa N., 
Rasamoelina H., Mikolasek O., de Verdal H. Variation géné- Rasamoelina H., Mikolasek O., de Verdal H. Variación gené-
tique des populations sauvages et des stocks issus d’élevage tica de las poblaciones silvestres y de los cultivos de tilapia 
de tilapia du Nil (Oreochromis niloticus) à Madagascar del Nilo (Oreochromis niloticus) en Madagascar
Quatre stocks issus de piscicultures et quatre populations La variación genética de cuatro poblaciones de cultivo y 
sauvages de tilapias du Nil (Oreochromis niloticus), espèce cuatro poblaciones silvestres de tilapia del Nilo (Oreochro-
qui a été introduite initialement à Madagascar il y a soixante mis niloticus, introducida en Madagascar hace 60 años) fue 
ans, ont été évalués pour leurs variations génétiques à partir evaluada con la análisis de 9 loci de microsatélites, con vis-
de l’analyse de neuf locus microsatellites pour déterminer les tas a determinar los niveles de variabilidad genética dentro 
niveaux de variabilité génétique au sein des populations et les de las poblaciones y las relaciones genéticas entre las mis-
relations génétiques entre ces populations. La diversité allé- mas. La diversidad alélica coincide con reportes referentes 
lique recoupait celle qui a été rapportée dans d’autres popu- a otras poblaciones africanas. No se encontró evidencia de 
lations africaines. Il n’y avait ni évidence d’écart dans les fré- discrepancia en las frecuencias alélicas esperadas en condi-
quences alléliques attendues dans les conditions d’équilibre ciones de equilibrio Hardy-Weinberg ni de consanguinidad 
de Hardy-Weinberg ni de consanguinité dans les populations en las poblaciones estudiadas. Tres grupos genotípicos dife-
étudiées. Trois groupes génotypiques distincts ont montré trois rentes mostraron tres introducciones separadas (provenientes 
introductions séparées (à partir d’Egypte et de l’île Maurice en de Egipto y de Islas Mauricio en 1956, así como de Japón en 
1956, et du Japon en 2011) et la présence de génotypes issus 2011). La presencia de genotipos provenientes de más de un 
de plus d’un groupe dans une même population a fourni la grupo en una misma población proporcionó la evidencia de 
preuve de mélanges. Il y avait des différences significatives mezclas genéticas. Se encontraron diferencias significativas 
entre les populations qui ne provenaient pas du même milieu entre las poblaciones que no provenían del mismo hábitat 
(sauvage ou d’élevage) ou qui n’étaient pas géographiquement (salvaje o de cultivo) o que no estaban geográficamente rela-
reliées. De par leur diversité génétique, les populations sau- cionadas. Debido a su diversidad genética, las poblaciones 
vages pourraient être des ressources intéressantes dans la pers- salvajes podrían representar un valioso recurso con vistas al 
pective d’un développement de la pisciculture du tilapia du desarrollo de la piscicultura de tilapia del Nilo en Madagas-
Nil à Madagascar. car.
Mots-clés  : Oreochromis niloticus, poisson, tilapia, population Palabras clave: Oreochromis niloticus, pescado, tilapia, pobla-
animale, variation génétique, structures génétiques, Madagascar ción animal, variación genética, estructura genética, Madagascar
106
Revue d’élevage et de médecine vétérinaire des pays tropicaux, 2019, 72 (3) : 101-106 ■ PRODUCTIONS ANIMALES ET PRODUITS ANIMAUX