The Walpole-Nornalup Estuary is one of the few estuarine systems on the south coast of Western Australia that is permanently-open to the sea and is of considerable cultural, recreational and ecological significance. The estuary is largely unmodified and surrounded by native vegetation and national parks and has been closed to all commercial fishing and netting since the early 20th century to preserve recreational fishing amenity. Despite this, the system faces increasing threats from rapid climate change and population growth. To better understand and sustain this valuable ecosystem and its fish fauna, annual fishery-independent monitoring has been undertaken since 2014, providing more than a decade of continuous data.
This program has examined changes in the structure and function of fish fauna (e.g. relative abundance, species richness, species composition and guild composition), biological attributes of key species (e.g. size structure, age and growth, diets), and broader ecosystem health (using a fish-based multi metric index) at various temporal scales (e.g. diel, seasonal, interannual and interdecadal). Findings have highlighted ecological changes due to short- and long-term climate variation and other stressors (e.g. fishing). The use of standardised fishery-independent sampling techniques has also allowed this system to be directly compared with others in the region, providing insight into local vs regional stressors on estuaries. Over time, the sampling program has been modified and refined to improve efficiency, including the development of less invasive sampling techniques. Key lessons, challenges and future directions will be discussed.