In modelling effects of global warming, invalid assumptions lead to unrealistic projections

In their recent Opinion, Pauly and Cheung ([Cheung, W. W. L., 2017]) provide new projections of future maximum fish weight (W ∞ ). Based on criticism by Lefevre et al. (2017) they changed the scaling exponent for anabolism, d G . Here we find that changing both d G and the scaling exponent for catabolism, b, leads to the projection that fish may even become 98% smaller with a 1°C increase in temperature. This unrealistic outcome indicates that the current W ∞ is unlikely to be explained by the Gill‐Oxygen Limitation Theory (GOLT) and, therefore, GOLT cannot be used as a mechanistic basis for model projections about fish size in a warmer world.