Etude des caractéristiques bioécologique et de d’algue rouge Halymenia durvillei (Bory de Saint-Vincent, 1828) et de préfaisabilité socio-technique de sa culture aux environs de Toliara (Sud-Ouest de Madagascar)

Abstract

The seaweed farming in Madagascar is based until now on the culture of two species:
Kappaphycus alvarezii and Eucheuma spinosum which are red algae. This sector faces a big
problem which is the EFA disease which until now is still a problem to control. This feasibility
study social and technical on the culture of Halymenia durvillei was begin from March to
September 2021 in bays of Toliara and Ranobe with an aim, on the one hand, of diversifying the
species of algae aquacultivables and on the other hand, to improve the incomes of the families of
the fishermen.
Socio-economic investigations were carried out into fishermen in order to draw up the
current assessment into seaweed farming in the area of Toliara. Prospections at sea by diving were
then carried out to identify the natural sites of H. durvillei and for studying the characteristics of
bio-ecological of this specie.
Tests of culture of this alga were carried out in order to know its daily growth.
Work of prospection on 14 stations located in the two bays (Toliara and Ranobe) made it possible
to deduce that the natural habitat of the red alga H. durvillei is in abundance arround of the coral
ecosystems of Toliara bay between 6 and 9m. Concerning the test of culture, the technique longline was adopted. Three classes of weight of cutting were tested (CL1 ≤50g, 50g80g) in order to choose the ideal weight of the cuttings to be cultivated. The cultures are
carried out in water of depth of 3m with sandy bottom.
The results of growth of the cuttings showed that at the end of one month, the class > 80g has the
best profit of daily average weight of 3,92g, while the two others (CL1 <50g, 50g< CL2 ≤ 80g)
with respectively 1,84g and 3,04g. So, the ideal weight suggested for the cuttings is in the
neighbourhoods of 80g.
This study, though preliminary, made it possible to have an idea on the possibility of the culture
of H. durvillei in the area of Toliara, and even in Madagascar.