eDNA Sampling Results

Summary of eDNA results for October (Spring) 2023

In October 2023, “creeks & critters” citizen scientists collected 82 eDNA water samples from 41 sampling site locations across Hornsby Shire.

From these 82 samples, eDNA analysis detected a total of 97 vertebrate taxa. In layman’s terms, that equates to 97 different groupings of distinct backboned critters living in and around our local waterways.

In a nutshell, our Spring sampling event detected eDNA from 6 frog, 25 fish, 6 reptile, 36 bird, and 24 mammal taxa. Whilst no platypus were detected, 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. 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.

67% of our eDNA detections (i.e. 65 of the 97 taxa) were analysed down to the species and common name level. This means that the remaining 32 of the 97 taxa couldn’t be resolved down to a particular species. This shortcoming is likely due to the fact that we’re utilising an innovative yet developing scientific field sampling technique that currently has inadequate eDNA reference data for our particular regional location.

A significant number of new species were recorded for the very first time within Hornsby Shire. Some of the more interesting findings of the eDNA sampling include:


  • Grey-headed flying fox - vulnerable species in NSW - recorded at 7 sampling site locations.
  • Large-footed bat - vulnerable species in NSW - recorded at a Colah Creek sampling site which is a known habitat location for these bats, so a good result to know their eDNA was detected.
  • Southeastern free-tailed bat (Ozimops planiceps) - new record for Fiddletown Creek, only two existing records within Hornsby Shire - one from Ku-ring-gai Chase NP and one from Berowra Heights.
  • Rakali - very few records within Hornsby Shire so positive result to identify their presence at Seymours Creek & Fiddletown Creek.


  • Spiny-cheeked honeyeater - Laughtondale Gully - new record for this area, not many records of this bird in Hornsby Shire.


  • Leaf Green Tree Frog and the Common Froglet were the third and fourth most common species detected at 25 and 22 of the 41 sampling sites.


  • Longfin Eels were the most common detected species at 35 of the 41 sampling sites. Eels are considered one of the most tolerant fish species and 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.
  • Cox’s Gudgeon was the second most common species detected at 30 of the 41 sampling sites – previously only records were from Galston Gorge, Fishponds and Cowan Creek.
  • Eel tailed catfish (Tandanus tandanus) - first record for Hornsby Shire at Berowra Creek.
  • Sea Mullet (Mugil cephalus) - First record in Berowra Creek - previously only recorded at Cowan Creek.
  • Australian Smelt (Retropinna semoni) - first record for Colah Creek - previously only record was in Berowra Creek.
  • Australian Bass - first record for Hornsby Shire - recorded at 8 sampling site locations.
  • Bullrout (Notesthes robusta) - first record for Hornsby Shire - Berowra Creek.
  • Flatback Mangrove Goby (Mugilogobius platynotus) – detected at Seymours Creek - previously only record was from Cowan Creek with only 133 occurrence records across Australia.
  • Flathead Gudgeon (Philypnodon grandiceps) - new records for Hornsby Shire at Colah Creek, Marramarra Creek and Berowra Creek - previously only recorded at Cowan Creek and Old Mans Creek.
  • Striped Gudgeon (Gobiomorphus australis) - recorded at 13 sampling sites but previously only records for Hornsby Shire were at Galston Gorge and Cowan Creek.
  • Dwarf Flathead Gudgeon (Philypnodon macrostomus) - first record for Hornsby Shire - Sams Creek.
  • Flat-tail Mullet (Liza argentea) new records for Hornsby Shire – detected at Berowra Creek, Colah Creek, Marramarra Creek and Seymours Creek - previously only record was from Cowan Creek.
  • Sea Mullet (Mugil cephalus) - new record for Berowra Creek - previously only records were at Cowan Creek & Brooklyn.

Introduced species

  • 13 introduced critters (i.e. not native) were detected – 10 were identified down to a species level and 3 to a genus.
  • Saw-shelled turtle - native species to Australia but introduced to Sydney, it was detected at Joe Crafts Creek. There are concerns that in the future it could prove to be a threat to the local Eastern Longnecked turtle.
  • Song Thrush (Turdus philomelos) - new record for Hornsby Shire, detected at 2 locations along Colah Creek. This bird’s normal distribution is around Melbourne.
  • European Carp - surprisingly it was only present in the lower part of Berowra Creek (before it goes saline) and along Colah Creek where the platypus was previously sighted. There is some evidence that carp could compete with platypus for the same food source.