eDNA Sampling Results

Summary of eDNA Results for Spring 2023 and Autumn 2024

As part of the Community, Creeks & Critters project, 82 eDNA samples were collected from 41 sites throughout Hornsby Shire during Spring 2023 and Autumn 2024. Using vertebrate and decapod eDNA metabarcoding assays, these samples provided a baseline biodiversity assessment of vertebrate and decapod species across two seasonal events.

Citizen scientists were instrumental in collecting water samples at each location, significantly enhancing our understanding of local biodiversity.

Key Highlights:

Spring 2023

• Vertebrate Detections:
  A total of 97 vertebrate taxa were identified, including:
  • 6 frog species
  • 25 fish species
  • 6 reptile species
  • 36 bird species
  • 24 mammal species

These taxa represent the diverse range of backboned animals living in and around our local waterways.

• Decapod Detections:
  5 decapod taxa were identified, including:
  • Riffle Shrimp (Australatya striolata)
  • Australian Glass Shrimp (Paratya australiensis)
  • Sydney Spiny Crayfish (Euastacus australasiensis)
  • Giant Spiny Crayfish (Euastacus spinifer)
  • A Genus of Australian Freshwater Crayfish (Euastacus)
• Notable Detections:
  • 2 threatened species:
    • Grey-headed Flying Fox (Pteropus poliocephalus)
    • Large-footed Bat (Myotis macropus)
  • 13 introduced species:
    • Saw-shelled turtle (Myuchelys latisternum), European carp (Cyprinus carpio), Goldfish (Carassius auratus), Genus of mosquitofish, Genus of rainbowfish, Genus of salmon & trout, Black rat (Rattus rattus), Brown rat (Rattus norvegicus), Common starling (Sturnus vulgaris), Domestic pigeon (Columba livia), European rabbit (Oryctolagus cuniculus), House mouse (Mus musculus), Song thrush (Turdus philomelos).
• Taxa Resolution:
  • 67% of vertebrate taxa (65 of 97) and 80% of decapod taxa were identified down to the species and common name level.
  • 32 taxa could not be resolved to species level, likely due to limited reference data available for this region in the growing field of eDNA analysis.
• Common Detections:
  • The Longfin Eel (Anguilla reinhardtii) was the most frequently detected vertebrate species.
  • Sydney Spiny Crayfish (Euastacus australasiensis) was the most common decapod detected.

Autumn 2024

• Vertebrate Detections:
  A total of 79 vertebrate taxa were identified, including:
  • 3 frog species
  • 19 fish species
  • 4 reptile species
  • 34 bird species
  • 19 mammal species

These figures represent the distinct backboned species identified from local waterways during Autumn.

• Decapod Detections:
  5 decapod taxa were identified, including:
  • Riffle Shrimp (Australatya striolata)
  • Common Yabby (Cherax destructor)
  • Sydney Spiny Crayfish (Euastacus australasiensis)
  • Giant Spiny Crayfish (Euastacus spinifer)
  • A Genus of Australian Freshwater Crayfish (Euastacus)
• Notable Detections:
  • 3 threatened species:
    • Powerful Owl (Ninox strenua)
    • Grey-headed Flying Fox (Pteropus poliocephalus)
    • Pilotbird (Pycnoptilus floccosus)
  • 9 introduced species:
    • Saw-shelled turtle (Myuchelys latisternum), European carp (Cyprinus carpio), Goldfish (Carassius auratus), Eastern gambusia (Gambusia holbrooki), Red fox (Vulpes vulpes), Black rat (Rattus rattus), Brown rat (Rattus norvegicus), Domestic pigeon (Columba livia), House mouse (Mus musculus).
• Taxa Resolution:
  • 78% of vertebrate taxa (62 of 79) and 80% of decapod taxa were identified down to the species and common name level.
  • 17 taxa could not be resolved to species level, likely due to the current limitations of regional eDNA reference data.
• Common Detections:
  • The Longfin Eel (Anguilla reinhardtii) remained the most frequently detected vertebrate species.
  • Sydney Spiny Crayfish (Euastacus australasiensis) was again the most common decapod detected.

Points of Interest:

Rakali (Hydromys chrysogaster) were only detected at 2 sampling sites during the Spring sampling. Anecdotal reports suggest that they were once regularly seen swimming around places like Berowra Waters, but there are very few records documented within Hornsby Shire.

Longfin Eels (Anguilla reinhardtii) were the most commonly detected species. Known for their environmental resilience, they can survive environmental hazards like high water temperatures or low dissolved oxygen concentrations. That means they can generally live in habitats where other species cannot survive.

There were several fish species detected for the first time in Hornsby Shire such as the Eel-tailed Catfish, Australian Bass and a few species of Gudgeon. Introduced species such as the Saw-shelled Turtle and European Carp could pose a potential threat to native species.

Many of our citizen scientists were anticipating the detection of Australian water dragons and Red-bellied black snakes and expressed surprise when results returned negative detections for these species. This experience highlighted the importance of comprehensive and accessible reference databases in the success of eDNA analysis. Regrettably, the current reference database being utilized does not encompass Water dragons and Red bellies. Additionally, it's worth noting that the unique physiological characteristics of reptiles, such as their hard exterior skin, may result in comparatively fewer eDNA fragments being shed, adding further complexity to their detection.

Whilst no platypus were detected in either Spring or Autumn, we need to remember that a negative result does not necessarily mean they are not there, just they were not around our sample locations at that time. Absence of evidence is not evidence of absence! eDNA is just one tool in our scientific toolkit. We remain hopeful that platypus still reside in Colah Creek, if not other Hornsby Shire creeks.

Based on current local species lists documented within the Atlas of Living Australia (ALA) there were a significant number of new species recorded for the very first time within Hornsby Shire. The ALA serves as our nation's primary biodiversity database, offering the most comprehensive and accessible dataset on Australia's biodiversity ever compiled.

View the Data Dashboard

View an additional Data Dashboard from EnviroDNA Laboratories - Spring 2023 and Autumn 2024 and their written report.