The Mekong River Commission (MRC) set up the Joint Environment Monitoring (JEM) Programme to monitor potential impacts from Mekong mainstream hydropower projects. The Australian Water Partnership through the Australia Mekong Water Facility and Charles Sturt University is providing expertise to support the design and trialing of fish passage monitoring as part of JEM. This pilot project aims are to guide and provide recommendations for sustainable fish pass monitoring methodologies in the future JEM.
The pilot study using acoustic tags commenced in February 2022 in the Mekong River in “the 4000 islands” region of southern Laos. The study location includes Khone falls, the largest waterfall in the world (10.9 km across), a 260 MW hydro power station and a strongly braided river network with considerable variation in substrates and river discharge between wet and dry seasons. The acoustic system includes a 34-receiver network, approximately 130 tagged fish from 11 species and an international collaboration with a team working on the Wonders of the Mekong (WOM) project in neighboring Cambodia. Early results highlight the value of using tag retention trials to assess local fish species and the importance understanding rainfall, water level variation and river discharge effects on the read range and detection probabilities associated with different receiver deployment methods and tag types. The project has been extremely successful in capacity building in our in-country partners and played a particularly important role in empowering women in fisheries sciences in Lao PDR and other member countries.