Smaller adult fish size in warmer water is not explained by elevated metabolism. (9th March 2022)

• Record Type: Journal Article
• Authors: Wootton, Henry F.; Morrongiello, John R.; Schmitt, Thomas; Audzijonyte, Asta
• Editors: Marshall, Dustin
• Is Part Of: Ecology letters. Volume 25:Number 5(2022)
• Page Start: 1177
• Page End: 1188
• Publication Date: 2022-03-09
• Subjects: climate change -- fish -- life history -- metabolism -- temperature size rule -- trade‐off -- warming; Ecology -- Periodicals; 577
• DOI: 10.1111/ele.13989
• Languages: English
• ISSNs: 1461-023X

Abstract

Abstract: Fish and other ectotherms living in warmer waters often grow faster as juveniles, mature earlier, but become smaller adults. Known as the temperature‐size rule (TSR), this pattern is commonly attributed to higher metabolism in warmer waters, leaving fewer resources for growth. An alternative explanation focuses on growth and reproduction trade‐offs across temperatures. We tested these hypotheses by measuring growth, maturation, metabolism and reproductive allocation from zebrafish populations kept at 26 and 30°C across six generations. Zebrafish growth and maturation followed TSR expectations but were not explained by baseline metabolic rate, which converged between temperature treatments after a few generations. Rather, we found that females at 30°C allocated more to reproduction, especially when maturing at the smallest sizes. We show that elevated temperatures do not necessarily increase baseline metabolism if sufficient acclimation is allowed and call for an urgent revision of modelling assumptions used to predict population and ecosystem responses to warming. Abstract : Fish and other ectotherms living in warmer waters often grow faster as juveniles, mature earlier, but end up smaller as adults. Known as the temperature‐size rule (TSR), this pattern is commonly attributed to higher metabolism in warmer waters leaving less energy or oxygen for growth, but could also be explained by adaptive shifts to earlier reproduction. We tested these hypotheses by measuring growth, maturation, metabolism, and reproductive allocation in zebrafish, and found that warmed populations acclimated their metabolic rates in later generations, suggesting that the TSR could be explained by shifts to earlier reproduction.