![]() Overall, all currently available survey techniques are biased and combining multiple methods to reduce the effects of biases (which is a common practice) increases cost and time requirements. use of acoustic telemetry) are often unable to deliver direct evidence of spawning and non-invasive methods are sensitive to observer biases and taxonomic misidentification (Caswell et al. On the other hand, injurious methods (i.e. ![]() The extra mortality rate imposed by destructive sampling methods makes them undesirable for monitoring reproduction in rare and threatened species (Tsukamoto 2006 Wei et al. most fishes and frogs) monitoring reproductive activity can be achieved by destructive, injurious or non-invasive methods (Table 1) (Lefort et al. For aquatic vertebrates relying on external fertilizations (e.g. 2014) determine population establishment for both invasive and translocated native species (Pearce 2013) and design and evaluate management actions (Koenig et al. 1984 Rose 1993 Grant, Chadwick & Halliday 2009) evaluate the reproductive output of populations (Levitan et al. Determining the timing and location of spawning events is important to: increase our understanding of the species’ biology (Harrison et al. the mass release of reproductive cells (oocytes and spermatozoa) into the water column, allowing external fertilization (Harrison et al. Many aquatic organisms reproduce sexually through a process called spawning, i.e. DNA-based methods provide promising opportunities to overcome these challenges through the monitoring of environmental DNA (eDNA) signals that are correlated with reproductive activity in aquatic organisms. Individual monitoring methods suffer from biases, do not provide direct evidence for reproduction or are unable to distinguish between reproductive failure and high mortality rates of early life-history stages. Monitoring reproduction in aquatic organisms is important for the conservation and management of species and/or populations (Koenig et al. Our method is likely to be transferrable to other aquatic species and can be particularly useful to increase our understanding of the spawning biology of cryptic, rare or threatened species as well as design and evaluate environmental management actions and determine species establishment. We have shown that changes in the relative abundance of nuclear and mitochondrial eDNA can be used to monitor spawning activity of the endangered Macquarie perch.Outside of the reproductive period, we find that nuclear and mitochondrial DNA fragments are equally abundant in environmental water samples. The data from the experimental study and the field survey supported our hypothesis that spawning events are characterized by higher concentrations of nuclear relative to mitochondrial eDNA.Using a quantitative PCR approach we monitored changes in nuclear and mitochondrial eDNA concentrations over time. We conducted an experimental and field study to determine the influence of spawning, and the mass release of spermatozoa in particular, on environmental DNA (eDNA) concentrations. ![]() Hence, developing a non-invasive sampling method to accurately determine the timing and location of reproduction for aquatic species would be extremely valuable. However, methods currently used for aquatic species are costly, time intensive, biased and often require destructive or injurious sampling.
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