Black Summer Blackfish - rain is not enough.
As climate change impacts the waterflow and fire regimes of upland areas, extreme environmental conditions and catastrophic events are likely to become more frequent. In January and February 2020, the Orroral Valley Fire in impacted approximately 60% of the range of the threatened Two-spined Blackfish, Gadopsis bispinosus, within the ACT water supply catchment area in Namadgi National Park. This resulted in a reduction of 80-90% in the blackfish population. This wasn’t the first time this population has been impacted by fire and drought. Monitoring has shown rapid declines in the Blackfish populations from at least four events in the last two decades the 2003 fires, the millennium drought, a prescription burn and the most recent 2020 fire and drought. Recovery from the pre 2020 impacts was reasonably rapid however, recovery from the 2020 bushfires has been very slow. Despite abundant river flows there has been a loss of juvenile and small adult fish from the river directly after the fire and limited successful breeding in the seasons since the fires.
Repeated population declines have the potential to impact genetic health. Managing recovery from these events and promoting resilience will require understanding of the genetic health and habitat to enable timely effective active management. Habitat assessment pre and post fire have highlighted the impact that sedimentation from the burn has had on blackfish habitat. Additional research is looking at genetic change spatially and temporally and the potential for assisting recovery through both artificial habitat structures and assisted translocation.