Introduced predatory fish species have caused small-bodied fish to decline worldwide. Some native fish now exist only in headwater streams where they are protected from invasive introduced species by barriers such as waterfalls. We explored the use of remote-sensing technology to improve processes to find and characterise these barriers and assist with future freshwater fish conservation.

The grey nurse shark (Carcharias taurus) is a Critically Endangered species with two genetically distinct Australian populations. An individual caught outside the species’ known distribution range off the Northern Territory of Australia was found to be genetically compatible with the western Australian population and not with the more highly endangered eastern Australian population. Our results imply a possible extension of the western Australian population and are useful baseline information for the development of conservation strategies for grey nurse shark in northern Australian waters.

We propose and cost nine priority actions to repair inland river and groundwater systems in Australia, including riparian revegetation, surface and groundwater recovery and management of barriers to flow and fish movement. Our estimates suggest approximate annual investment from 2025 to 2054 of A$3.1 billion (2022 dollar values). Revenue generated through the carbon market through riparian restoration could cover between 37 and 72% of the costs, reducing investment needed to between A$0.9 billion and A$2.0 billion. We highlight opportunities for Indigenous nations to implement associated on-ground works.