Aquatic Life History Trajectories Are Shaped by Selection, Not Oxygen Limitation

Pauly [ 1 Pauly D. Female fish grow bigger–let’s deal with it. Trends Ecol Evol. 2019; 34 : 181 Google Scholar ] argues that, as espoused in the gill-oxygen limitation theory (GOLT), growth slows as size increases because oxygen supply via the gills is unable to keep up with the oxygen demands of an increasingly large body. Thus, according to GOLT, growth determines the timing of reproduction, and fish reproduce when they become oxygen limited and growth starts to decline. GOLT has been critiqued on physiological grounds [ 2 Lefevre S. et al. Models projecting the fate of fish populations under climate change need to be based on valid physiological mechanisms. Glob. Change Biol. 2017; 23 : 3449-3459 Crossref PubMed Scopus (16) Google Scholar , 3 Lefevre S. et al. In modelling effects of global warming, invalid assumptions lead to unrealistic projections. Glob. Change Biol. 2018; 24 : 553-556 Crossref PubMed Scopus (3) Google Scholar ], and we agree with those critiques. Large fish are no more oxygen limited than small fish, primarily because their respiratory surface area matches their metabolic demand for oxygen over a large size range (see Table 1 in [ 4 Nilsson G.E. ？stlund-Nilsson S. Does size matter for hypoxia tolerance in fish?. Biol. Rev. 2008; 83 : 173-189 Crossref PubMed Scopus (97) Google Scholar ])