Risk factors and management strategies associated with summer mortality in Australian abalone

In 2018, the Australian farmed and wild-fished abalone industry was valued at ~$220 million, which is forecasted to expand (Mobsby, 2020). In Australian abalone aquaculture, higher-than-normal mortality rates have been reported to coincide with warm water temperatures. Abalone mortality
during warm water temperatures has been termed summer mortality and is a research priority for the Australian abalone industry (AAGA, 2020).
Summer mortality is often used as an umbrella term and lacks a true definition for what constitutes a summer mortality event and their associated risk factors. Mortalities attributed to summer mortality can accumulate into large stock losses. Mortality rates of up to 50% reported farmed in 3-year-old Greenlip Abalone (Haliotis laevigata) have been attributed to summer mortality (Vandepeer, 2006). Since 2010, eight of the ten warmest years on record were documented for Australia’s ocean surface temperatures (CSIRO, 2018). As the frequency of marine heatwaves is forecast to increase (Roberts et al., 2019), it is important to determine what factors increase the risk of summer mortality in abalone farms and identify any causative agents. Prior to this project, there was no case definition for summer mortality. Identifying what management practices could reduce stock loss and prevent summer mortality was therefore difficult.