Project 1: Marine extremes: understanding how marine heatwaves impact on fishes and fisheries productivity
Marine environments are heating up and this is profoundly impacting on biota directly through the exceedance of thermal tolerances, and indirectly through changes to biological interactions and distributions. The vast majority of studies exploring marine warming do so in the context of directional change to the long-term average, with little attention paid to the impacts of extreme events such as marine heatwaves. Indeed, only recently have marine heatwaves been formerly defined and measures taken to describe their spatial and temporal extent. This is despite a broader appreciation of how extreme events can influence the structure of other ecosystems and their utility in providing analogies for how species might respond to future warming.
We do not have the tools to readily assess the biological impacts of marine heatwaves in areas where detailed monitoring is not yet in place. This is a major impediment to our understanding of these events that can cause major ecological and fisheries disturbance, and in turn limits out ability to make adequate predictions of how forecast increases in heatwave magnitude, frequency and duration affect marine ecosystems. Further, we need to understand how marine organisms have responded to extreme events in the past and quantify their capacity to adequately respond in the future if we are to ensure our predictions are meaningful. Here, we are employing two highly innovative techniques using information stored in otoliths to estimate levels of thermal tolerance and behavioural plasticity within and among individuals and populations, and assess whether there is adequate adaptive capacity to deal with extreme heatwave events. This work is funded by the Australian Academy of Sciences’ Thomas Davies Research Grant for Marine, Soil and Plant Biology.
Project 2: Assessing the sustainability of Venus Bay’s recreational and commercial pipi harvest
Pipis inhabit the intertidal zones of surf beaches where they are harvested for human consumption and bait. Victoria’s Venus Bay supports a major recreational pipi fishery, but due to their ease of collection, there have been growing concerns that they are vulnerable to overfishing. This project, funded through Victoria’s Recreational Fishing Grants Program, is investigating how the Venus Bay pipi population responds to natural environmental variation and harvesting. It will facilitate a meaningful appraisal of the fishery’s current status and help identify management options to ensure its future sustainability.
Project 3: Growth and productivity of fish populations in a changing world
Fishing activity and climate change are having major impacts on marine fish populations in the world’s oceans. However, it is difficult to determine just what impact each of these two factors is having, mainly because long-term observational data on the productivity of marine ecosystems is sparse.
We are working closely with colleagues at NIWA to determine how growth in selected culturally and commercially important New Zealand fishes (snapper, tarakihi, hoki and ling) has varied over the last 50+ years. We are linking this variation to past fluctuations in climate variables (e.g., sea surface temperature) and fishing activity (e.g., fish stock size, intensity of fishing). Determining what caused fish growth to vary in the past will provide insight to help predict fishery productivity under future regimes of climate and fishery exploitation. This predictive information can be incorporated in the scientific assessments of fish stocks, which are conducted regularly by the Ministry for Primary Industries, thus improving the quality of scientific advice and enhancing the management of New Zealand’s natural marine resources. We will use existing fish otolith (ear bone) collections to determine past growth. Growth histories of individual fish will be constructed by measuring the widths of increments laid down annually in their otoliths, similar to the formation of tree rings. A year when the fish experienced good growth is marked by a relatively broad otolith growth increment. The data from each fish will be combined to determine population-scale growth patterns. These will be analysed alongside population trajectories from stock assessment, and globally available environmental and climate data. This project is funded by New Zealand’s Ministry for Business, Innovation and Employment’s Smart Ideas grant scheme.
People involved: John Morrongiello (NCCC), Peter Horn, Phillip Sutton, Matthew Dunn and Caoimhghin Ó Maolagáin (NIWA)
Project 4: Impacts of current and future climate change on Victorian trout
Our climate is rapidly changing. Rainfall has declined across much of Victoria and this has led to significant reductions in stream flow. Air temperatures have increased, and we’re seeing a greater frequency and intensity of extreme weather events like heatwaves and climate phenomena like drought. These changing conditions pose challenges for our river trout that need cool, well oxygenated and flowing waters to thrive. It is essential that we understand how trout have responded to past climatic change so we can make meaningful predictions of how future declines in rainfall and increases in temperature will impact on trout. In turn, this knowledge will help managers make proactive decisions about where, when and on what, resources should be directed to mitigate climate threats to trout and facilitate fisheries adaptation. Likewise, anglers can be better informed about their fishery’s future, contribute to improving fishery quality, and even make decisions on where and when to fish to ensure they have a great day on the water.
We are working closely with the Victorian Fisheries Authority and recreational anglers to provide an appraisal of global management efforts to mitigate the impacts of climate change on wild trout fisheries, develop stream shading models to help prioritise on-ground management efforts; and communicate key messages around climate change impacts on trout, global management activities and tangible on-ground opportunities in Victoria.