Abstract

In coastal Madagascar, marine protected areas have emerged as a strategy to manage a coupled-human natural system shaped by both ecological and social factors. Macroinvertebrate fisheries have long played a significant socioeconomic role in Madagascar, contributing to local consumption, exports, and tourism-related ornament production. Multiple species on shallow coral reefs are targeted by coastal communities through gleaning. While this ecosystem has been included in conservation efforts through marine protected areas (MPAs) around the country, evaluations of the reserve's effect on macroinvertebrates have been concentrated on only a few species. This study evaluates the effects of MPAs on macroinvertebrate communities in shallow intertidal coral reef habitats across 20 villages corresponding to reserve and non-reserve sites across Southwest, Northeast, and Northwest Madagascar. The Shannon diversity index and abundance of macroinvertebrates were compared using quadrat sampling in reserve and non-reserve sites, while accounting for regional differences and substrate composition. Throughout Madagascar, beta regression analysis indicated no significant effect of reserve status on the Shannon diversity index. However, a negative binomial-GLM revealed a significant positive reserve effect on mean macroinvertebrate abundance. According to the model, areas outside reserves had 36.6% lower estimated mean macroinvertebrate abundance than inside reserves across Madagascar, with differences mostly driven by mollusks and echinoderms. Macroinvertebrate diversity decreased with increasing turf algae and hard coral cover. Abundance of macroinvertebrates was significantly negatively correlated with substrate coverage. For every 1% increase in macroalgae cover, macroinvertebrate abundance decreased by approximately 0.55%, while for every 1% increase in hard coral cover, abundance decreased by about 2.7%. In contrast, abundance was positively associated with dead coral cover. Multivariate analyses confirmed that reserve status significantly influenced substrate composition. Inside reserves, macroalgae cover was lower (10.9% vs 22.3%) and hard coral higher (2.85% vs. 0.28%) than outside. Regional differences in biodiversity metrics and substrate composition were also found. These results emphasize how reserve status and environmental factors interact to shape macroinvertebrate biodiversity, underscoring the necessity of region-specific management approaches to support sustainable gleaning fisheries in countries where community-managed MPAs are implemented.