Scaling the effects of size and temperature on animal consumption rates from individuals to populations in a subtropical reef fish

Abstract Measuring how temperature and body size drive individual consumption rates is fundamental to predict how climate change might shape population‐level consumption pressure. Yet, such measurements remain rare. Here we fill this gap by parametrizing a theoretical model inspired by the Metabolic Theory of Ecology with laboratory experiments using an abundant cryptobenthic herbivorous‐detritivorous fish, Scartella cristata . We derive corollaries of the theory at the population level, which allow researchers to quantify how population‐level consumption rates might change under alternative scenarios of thermal regime and size distribution. We simulate multiple future scenarios by combining our model parameter estimates with field surveys of S. cristata size structure at different years and thermal regimes. We find that while body size exhibits stronger effects across individuals of different sizes, small increments in average thermal regime are more likely to alter population‐level consumption pressure. Our study helps quantify and formalize how heterotrophic metabolism will further constrain primary production in a changing world. Read the free Plain Language Summary for this article on the Journal blog.