Asymmetric thermal risks across Malagasy macrotidal reef zones threaten socioeconomic outcomes for local fisheries

Fishery management and climate adaptation in the coastal zone often overlook how marine microclimates vary through space. In tropical macrotidal systems, gleaning fisheries are an important source of nutrition among local communities and are restricted to intertidal habitats. Here, we report habitat temperature across subtidal and intertidal reef zones in southwest Madagascar using over a year of in situ temperature data and decadal tide cycle analysis, contextualized with fishery catch and species composition data. Temperatures on the intertidal reef flat reach 48.8°C, with peak heat occurring during shoulder seasons rather than peak summer, driven by midday low tides. Fishery data reveal that shallow, warm areas of the reef provide substantial biomass, effort, and much of the region's sea cucumber catch. Gleaning habitats experience thermal extremes that are both more intense and seasonally offset from subtidal boat-fishing zones, an important consideration for climate-adaptive management of spatially segregated and economically sensitive fisheries.