The trophic niche is an aspect of species biology that is foundational to understanding many biological processes. In coastal marine ecosystems, small schooling fishes have a large influence on food web dynamics and structure, but despite their importance, the trophic niches of many of these fishes are either completely unknown or only preliminarily described. We assembled a diet dataset for 12 species of small, coastal Indo-Pacific clupeoids (herrings, sardines, and anchovies) containing measurements of 12,401 prey items from 619 individual fish predators to address four objectives: (1) assign species to trophic guilds based upon prey-type and -size consumption, (2) identify ontogenetic shifts in prey-type and -size consumption, (3) test the hypotheses that niche breadth, measured as the range of prey sizes consumed, and relative niche breadth (ratio of niche breadth to predator size) are positively correlated with predator size, and (4) test the hypotheses that maximum prey-size consumption and relative maximum prey-size consumption (ratio of maximum prey size to predator size) are positively correlated with predator size. We identified three and five trophic guilds based upon prey types and prey sizes, respectively. Diets changed through ontogeny in nearly every species. Linear regression revealed positive correlations between niche breadth, maximum prey width, and relative maximum prey width and predator size, but did not find a statistically significant correlation between relative niche breadth and predator size. This study shows that measuring prey size in addition to prey type can offer additional, higher resolution information about fish trophic ecology. The dataset presented here will be useful for future ecological and evolutionary research and fisheries management.