Etude de la variation spatiale et interannuelle de la diversité des proies des poissons associés aux herbiers marins, par l’étude des contenus digestifs et de l’isotope stable (dans la baie de Toliara)

Abstract

Seagrass beds are characterized by the important resources that are targeted by small-scale
fishing in Madagascar. The pressures under which these resources undergo can lead to changes
in species ecology as well as their diet. The study aims at knowing the diet variation of two fish
species associated with seagrass beds, the rabbitfish Siganus sutor and the spinecheek goby
Oplopomus oplopomus. The populations of the both sites (Ankilibe and Sarodrano) that were
collected over two years (December 2017 and December 2018) were compared. Gut contents
analysis (consumed prey just before their capture) combined with carbon and nitrogen isotopic
analyses (long-term food source) allowed to establish the feeding behaviour of these two
species. The results reveal a variation in the trophic niche of the two species between sites and
years. Fishes diet also changes according to their size, particularly for rabbitfish. This variation
is not observed on the type of food consumed but on the frequency and abundance of prey. So
this may be linked to species adaptation on the food sources available in their environment