Sevens Creek in central Victoria is one of the few remaining waterways in the state where the nationally endangered Trout Cod (Maccullochella macquariensis) and Macquarie Perch (Macquaria australasica) co-occur. One of the key threats to populations of these fish are exotic species such as Redfin and Carp. Redfin are highly voracious and predate on juvenile fish, and also compete for habitat and food resources. They also have the potential to spread the Epizootic Haematopoietic Necrosis Virus (EHNV) known to be lethal to many fish species including Trout Cod and Macquarie Perch. There is a risk that this virus could become established in Sevens Creek, posing a significant threat to populations.
ARI has monitored fish populations in Sevens Creek for many years and undertaken ad hoc exotic fish removal. In 2014 and 2015 ARI targeted the removal of Redfin and Carp to reduce the threat of predation, competition and the introduction of disease. In this removal program, 775 Redfin and 119 Carp individuals were removed. For Redfin in particular, this reduced their numbers substantially from those recorded prior to the removal. The abundance of Trout Cod and Macquarie Perch also increased over this period. Strong breeding contributed to population growth, which is a promising sign for the sustainability of these populations. This is particularly important for Sevens Creek because a natural barrier is present in the waterway which limits opportunities for recolonization.
Targeted exotic species removal complements the extensive riparian and instream habitat restoration conducted by the Goulburn Broken Catchment Management Authority and has greatly boosted Trout Cod and Macquarie Perch populations in Sevens Creek. This highlights that persistent and targeted exotic species removal in conjunction with integrated restoration benefits threatened fish species. This project was funded by the Victorian Government.
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