Uneven progress in tackling malnutrition has kept food and nutrition security high on the 53 development agenda globally 1,3. Micronutrients, such as iron and zinc, are a particular focus; it is estimated that nearly two billion people lack key micronutrients 7 , underlying nearly half of all deaths in children under the age of five years , and reducing GDP in Africa by estimates of up to 11% 2,3,7. Consequently, efforts to tackle malnutrition have shifted from a focus on 57 increasing energy and macronutrients (e.g. protein) towards ensuring sufficient consumption 58 of micronutrients 3. People gain nutrients from a mix of locally produced and imported food products. Fish, harvested widely and traded both domestically and internationally, are a rich source of bioavailable micronutrients, which are often deficient in diets that rely heavily on plant-based sources 6,8. Fish could therefore help address nutritional deficiencies if there are 62 sufficient quantities of fishery-derived nutrients accessible in places where deficiencies exist. 63 However, addressing this major food policy frontier has been elusive, in part because the 64 nutrient composition of fish varies significantly among species, and data remain sparse for most species 5. Here we determine the contribution marine fisheries can make to addressing micronutrient 68 deficiencies. First, using strict inclusion protocols (methods), we developed a database of 2,267 69 measures of nutritional composition, from 367 fish species, spanning 43 countries, for seven nutrients essential to human health: calcium, iron, selenium, zinc, vitamin A, omega-3 (n-3 71 fatty acids), and protein. We then gathered species-level environmental and ecological traits 72 that capture elements of diet, thermal regime, and energetic demand in fish 9,10 to develop a series of Bayesian hierarchical models that determine drivers of nutrient content (Methods).
