The MAHERY-Antongil study cohort was set up in September 2015 to assess the nutritional value of seafood for the coastal Malagasy population living along Antongil Bay in northeastern Madagascar. The study aimed to understand the relationships among different marine resource governance models, local people's fish catch, the consumption of seafood, and nutritional status. The initial pilot period (from September 2015 until April 2016) began with 225 households and a total of 1,031 individuals, during which time enrollment was finalized and preliminary baseline survey information was collected. Among the baseline participants, 49.4% were female, and the median age was 16 years.