Caractérisation de l’impact de la coupe de forêt de mangrove sur la ressource en crabe Scylla serrata : cas de la baie de Bombetoka (Nord-Ouest de Madagascar)

Abstract

This study was conducted between March 2021 and July 2022 to identify the relationship
between mangrove afforestation quality and the establishment of mangrove crab Scylla serrata
burrows in Bombetoka Bay. Remote sensing allowed the vegetation dynamics classification
from 2018 to 2021 into three types: gains, loss and stability of chlorophyll activity. Field
surveys of ecological parameters and S. serrata burrows counting were conducted within 100
m2 quadrats distributed at each dynamic. The results showed that "Gain" class vegetation is
significantly denser; containing 21 244 mangrove trees / ha ± 25 581 against 7 686 ± 6 414 et
6 544 mangrove trees / ha ± 5 690 respectively within the "Stable" and "Loss" areas. In addition,
the “Gain” zones are always reached by the upper limit of the high tide. The consistency of
their soil is more malleable; it is "neither too dry nor too wet" facilitating burrowing. All these
conditions are favorable to the establishment of S. serrata burrows. Indeed, burrows are
abundant within the "Gain" zones; they number 336 / ha ± 186 compared to 264 ± 280 and 169
burrows / ha ± 109 respectively within the "Stable" and "Loss" zones. Thus, this study
demonstrated that S. serrata abundance is influenced by the state of the mangrove forest.
Keywords: Bombetoka, mangrove, Scylla serrata, burrow