Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

The acute and legacy impacts of marine heatwaves on fish growth in the Pacific Ocean (#146)

Jessica R Randall 1 , Stephen Swearer 1 , Emily Fobert 1 , Bryan Black 2 , John Morrongiello 1
  1. University of Melbourne, Melbourne, VIC, Australia
  2. University of Arizona, Tucson, Arizona, United States of America

The increased frequency and intensity of global marine heatwaves in the past century has led to greater awareness of how extreme events can shape ecosystems. While these acute warming events cause a wide range of impacts, the most common observations are often the lethal effects on marine life, as a result of starvation or exceeding a species’ thermal tolerance or changes in distribution. However, few studies have assessed the sub-lethal impacts of heatwaves on fish such as growth. I aim to assess the impact of marine heatwaves on Pacific fisheries by examining the immediate and legacy effects on fish growth. Specifically, I have 1) identified patterns in fish growth responses to heatwaves among species groups and/or regions and 2) if growth was impacted, examined how long growth was altered by heatwaves both during and after the event. I calculated a suite of annual heatwave parameters from satellite-derived daily sea surface temperatures from 1981-present. Additionally, I used otolith-based growth biochronologies from commercially-harvested species to generate models to partition observed changes in growth to heatwaves, as well as determine which event and species life-history attributes have the best explanatory power. Preliminary results from five species in Southeast Australia show a range of responses to heatwaves with growth best predicted by different event attributes. The frequency, rate of onset, and event intensity of heatwaves were the best explanatory parameters for growth in species positively impacted by heatwaves. Other responses included no effect on growth and variation in growth between life stages in response to heatwaves. Our ability to anticipate fish growth sensitivity to heatwaves is not only important for predicting responses under future climate events but is also essential for understanding the legacy effects of these events which may alter food webs and assemblages well after the event subsides.