Spiny rock lobster (Jasus edwardsii) responses to marine heatwave conditions in southern New Zealand

Abstract

Globally, marine heatwaves (MHW) are predicted to increase in intensity, duration and frequency but the impacts of these extreme temperature events remain unassessed for a large number of valuable fisheries worldwide. During 2021–2023, southwest New Zealand experienced back-to-back summer MHWs, including the strongest and longest MHW during the 40-year satellite-era. These MHWs were linked to reports of southern rock lobster (Jasus edwardsii) being caught in unusually poor condition. Jasus edwardsii supports one of the most economically valuable fisheries in New Zealand, and also has significant ecological, cultural, and recreational value. By simulating multi-week strong and extreme MHWs in the laboratory and sampling lobsters in the wild, we quantified the effects of thermal stress on J. edwardsii physiology and survival. In addition, we assessed whether lobsters could recover from any declines in health induced by the MHWs following a return to average temperatures. Methods included respirometry and metabolomic analyses of haemolymph pre-, peak- and post-MHW and assessments of haemolymph serum protein and visual stress scores every two weeks. Lobsters that experienced extreme MHW conditions displayed significant declines in haemolymph serum protein and increases in maximum metabolic rate and aerobic scope but these changes were not observed in the strong MHW or control treatments. Likewise metabolomics only identified differences between extreme MHW and control lobsters, including a number of acyl carnitines. Following a return to average summer temperatures, the only difference still apparent was elevated oxygen consumption for lobsters that experienced extreme MHW conditions. The results of this study highlight MHWs can have detrimental effects on species of fisheries value but that recovery may also be possible.