The fate of a popular fish found on the Great Barrier Reef could be in jeopardy, with a new James Cook University study highlighting the impact of marine heatwaves on the Spanish Flag Snapper.
JCU researchers have discovered that while the species, commonly known as 'Stripeys', can recover from the effects of sharp rises in water temperature, catch-and-release fishing during these events may significantly impact their health and survival rates.
The study, led by former JCU PhD student Shannon McMahon, collected mature adult Stripeys between Cairns and Cape Melville before transporting them to Townsville to simulate marine heatwaves (MHW) across twelve 2500L outdoor tanks.
"We all know that coral reefs are particularly susceptible to marine heatwaves, which cause mass coral bleaching and mortality, but there was a real knowledge gap in the effects of MHW on coral reef fish," Dr McMahon said.
"Our results show that marine heatwave conditions cause direct physiological demands on adult coral reef snapper and residual effects can last for at least two weeks post these events.
"During a heatwave the fish are under a lot more metabolic stress, and we found that producing more haemoglobin was one coping mechanism during these events."
Dr McMahon said the species energetic needs were shown to increase up to 37 per cent during MHW conditions.
"Climate change has led to the increasing frequency and intensity of MHWs, so there is an immediate need to understand the sensitivity of organisms both during and following these events," he said.
Dr McMahon, who is currently a Postdoctoral Scholar at Okinawa Institute of Science and Technology, said the increased demand for food from Stripeys could lead to increased predation of smaller reef organisms, which would have flow-on effects to wider reef ecosystems.
"If they can't keep up their food intake to meet these stresses, these increased energy demands could mean a trade-off by decreasing other activities like growth or reproduction, which might influence population dynamics,"
Dr McMahon said.
"Fishing or capture puts them under pressure and when they are more vulnerable and really heat stressed, they could die easier following a catch and release."
He went on to say that fishing restrictions during marine heatwaves or advancement in catch and release protocols should be considered to limit or alleviate the effects on Stripeys and similar species.
"Further research on other coral reef fishes would give us a better idea of the effects future marine heatwaves may impose on these vital ecosystems," he said.
The paper was co-authored by JCU's Marine Biology and Aquaculture Adjunct Professor Philip Munday and Associate Professor Dr Jennifer Donelson.
Associate Professor Donelson said the study would help researchers better understand how larger reef fish responded to climate change, especially as marine heatwaves continue to increase in frequency and intensity.
"Shannon's passion for working on larger species of fish really drove his PhD," she said.
"There hasn't really been much research like this done on these larger reef fish before as they need big, purpose-built tanks but despite the challenges we were able to achieve original results at JCU Marine and Aquaculture Research Facility."
