A project undertaken at Adelaide University, and supervised by Justin Brookes
Freshwater fish are highly threatened globally. Developing recovery plans for the most imperilled species necessitates precise information on critical habitats and distribution, which can traditionally only be obtained through direct observation and capture of individuals. However, rare and threatened freshwater species are inherently difficult to sample due to their low abundance and infrequent encounters. For example, the freshwater sawfish (Pristis pristis) is so seldom observed that it has been referred to as the “Ghost of the coast”, while the northern river shark (Glyphis garricki) is recognised as one of the world’s rarest shark species.
Abundance and distribution data for these and similarly rare species often requires intensive field efforts. While traditional trapping and tracking studies can yield valuable insights into habitat preferences and behaviour, such methods are labour-intensive, costly, and spatially limited. To address these challenges, molecular techniques are increasingly employed for the detection of rare species. These methods are now routinely applied for species detection and biodiversity assessment in freshwater ecosystems via the presence, location and abundance of environmental DNA (eDNA) collected from environmental samples.
In flowing freshwater ecosystems, however, the interpretation of eDNA data is complicated by the longitudinal transport of DNA downstream and the persistence of DNA in the environment, which can result in false-positive detections and introduce uncertainty as to the precise location of target organisms.
To resolve this uncertainty, our research aims to combine novel genomic technologies with cutting edge hydrodynamic modelling, providing a quantitative framework that incorporates the uncertainty and variability in the biological and hydrodynamic processes that govern the movement, degradation, and detectability of eDNA. The eventual goal of this work is to resolve the upstream distribution of rare and endangered freshwater species less invasively and for a fraction of the cost of traditional methods.
Globally this technology could be applied to identify critical habitat for endangered species such as the Adriatic Sturgeon (Acipenser maccarii) and Mekong giant catfish (Pangasianodon gigas), or for the early detection of invasive species such as sleepy cod (Oxyeleotris lineolata) in the river systems of the Lake Eyre Basin or tilapia (Oreochromis niloticus) in the freshwater ecosystems of many tropical and subtropical regions.