One of Australia’s most comprehensive assessments of endemic, rare or threatened freshwater fish has found numerous species were severely at risk of extinction due to multiple threats including habitat loss, invasive species and warmer waters.
The species facing the highest risk was the diminutive Daintree rainbowfish (Cairnsichthys bitaeniatus), found only in small rainforest streams in the Daintree region in Far North Queensland, with up to 10 unique threats to its population.
“These freshwater fish species are unique,” lead author Dr Kaitlyn O’Mara said.
“Many are found nowhere else on Earth.
“If they are lost from the Wet Tropics, they become globally extinct.
“Freshwater fish are also important components of stream ecosystems and are indicators of ecosystem health.
“Their decline signals broader environmental deterioration.”
The study of 22 freshwater fish species across the entire Wet Tropics region was led by Griffith University’s Australian Rivers Institute and funded by Commonwealth-State Disaster Recovery Funding Arrangements and the Australian Government under the National Environmental Science Program’s Resilient Landscapes Hub.
The team of 18 experts representing Australian universities, government agencies, consultancies and regional natural resource management organisations, assessed published and grey literature, and conservation listings as well as previous research on species biology, distribution and threats to identify the species most at risk and the actions needed to save them.
They assessed 24 separate threats ranging from climate change and invasive species to water extraction, habitat degradation and hybridisation, and for every species they considered not only the threat itself but its likelihood, consequence, extent, timing, trend and confidence level before assigning risk ratings.
“You can’t save what you can’t see, so understanding the risk of impacts of historical, emerging, and intensifying threats to these species is a critical knowledge gap that has hindered conservation planning,” Dr O’Mara said.
“Extreme climate events, altered river flows, habitat clearing, poor water quality, invasive fish, and hybridisation with introduced native fish are a high-risk threat to many species, but the species with smallest ranges or lowest numbers were the most vulnerable.”
Highest risk species
- Daintree rainbowfish (Cairnsichthys bitaeniatus)
- Cairns rainbowfish (Cairnsichthys rhombosomoides)
- Malanda rainbowfish (Melanotaenia sp. nov. ‘Malanda‘)
- Lake Eacham rainbowfish (Melanotaenia eachamensis)
- Utchee rainbowfish (Melanotaenia utcheensis)
Other highly threatened species
- Bloomfield River cod (Guyu wujalwujalensis)
- Mulgrave goby (Glossogobius bellendenensis)
- Several cling gobies, including:
- Opal cling goby
- Emerald cling goby
- Black Stiphodon
- Orange cling goby
- Discord goby
- Fehlmann’s Sicyopus
- Frog goby
The assessment identified invasive species, climate‑driven changes to temperature and hydrology, habitat and water quality degradation, and hybridisation with translocated native fishes as among the most severe threats, particularly for narrowly distributed rainbowfishes and migratory cling gobies.
The research team called for urgent conservation planning and recovery actions such as habitat restoration, invasive species control, improved riparian management, and captive breeding.
“We hope our study can inform the development of a multi-species recovery action plan to guide on-ground management to reverse declines and help recover these unique fish species,” said project leader Professor Mark Kennard.
The study ‘Expert risk assessment and recovery actions for rare and threatened freshwater fishes in the Wet Tropics of Australia’ has been published in Pacific Conservation Biology.
