Étude de la bio-écologie des crabes vecteurs du virus White Spot en vue d’une application sur l’optimisation de la biosécurité d’une ferme aquacole : Cas de la ferme AQUALMA Mahajamba

Abstract

White Spot Syndrome Virus has emerged as the main pathogen of shrimp that has
caused epizootics and serious consequences for shrimp aquaculture around the world. In
Madagascar, this epidemic has led to the closure of many shrimp farms and the conversion of
shrimp farms into other activities.
Being vectors of WSSV, the abundance and composition of megabenthic fauna such
as crabs are recorded at four stations located at the five farms of AQUALMA. The sediment
was also studied to determine the correlation between fauna and their environment. Crab species
are distributed unevenly on the farm; characterized as dominant species with the Jolly,
Metopograpsus sp and Neosarmatium meinerti classification, cover more than half of the crabs
present in the Mahajamba farm with 36.73% and 17.88% respectively in terms of relative
abundance. Scylla seratta, Uca annulipes, Uca rapax, Uca spp1, Uca spp2 are only influential
species whose relative abundance varies from 5.88% to 13.88%. Some of these species correlate
with each other while others are not. Only Uca crabs have a negative correlation with their
environment, where their presence in the basins is strongly conditioned by a few parameters.
The results showed a higher risk of horizontal transmission of WSSV from wild
animals to the receptor ecosystem of the catchment area if the presence of the virus is detected
in the megabenthic fauna and if biosecurity measures faults in the introduction of these animals
into the breeding area.
Keywords: Crabs, WSSV, Pond, Shrimps, AQUALMA, Mahajamba