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eDNA Sampling Results

Summary of eDNA results for October (Spring) 2023

In October 2023, “Creeks and Critters” citizen scientists collected 82 eDNA water samples from 41 sampling site locations across Hornsby Shire.

Analysis of the eDNA from these samples revealed 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.

Six frog, 25 fish, six reptile, 36 bird, and 24 mammal taxa were detected from the eDNA in this Spring sampling event.

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

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. 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.

Our Creeks and Critters citizen scientists are getting prepared to sample the eDNA in our local waterways again in April (Autumn) 2024.

A significant number of new species were recorded for the very first time within Hornsby Shire. Please note that when we refer to "first, new, and/or previous records" we are basing these assertions on the current species lists for Hornsby Shire documented within the Atlas of Living Australia (ALA). The ALA serves as our nation's primary biodiversity database, offering the most comprehensive and accessible dataset on Australia's biodiversity ever compiled.

Some of the more interesting findings of the eDNA sampling include:

  • 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.
Mammals
  • Grey-headed Flying Fox (Pteropus poliocephalus): Vulnerable species in NSW, recorded at 7 sampling sites.
  • Large-footed Bat (Myotis macropus): Vulnerable species in NSW, detected at Colah Creek, a known habitat for these bats.
  • Southeastern Free-tailed Bat (Ozimops planiceps): New record for Fiddletown Creek, with only two previous records in Hornsby Shire.
  • Rakali (Hydromys chrysogaster): Positive detection at Seymours Creek & Fiddletown Creek, with very few records within Hornsby Shire.
Birds

Spiny-cheeked Honeyeater (Acanthagenys rufogularis): New record for Laughtondale Gully, uncommon in Hornsby Shire.

Reptiles

3 different species of Skinks were detected – Eastern water skink (Eulamprus quoyii) at 6 sites, Weasel skink (Saproscincus mustelinus) at 3 sites, and Barred-sided skink (Concinnia tenuis) at 2 sites.

Many of our citizen scientists were anticipating the detection of Australian Water Dragons and expressed surprise when the results returned negative. 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. 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.

Amphibians

Leaf Green Creek Frog (Litoria ranoidea) and Common Froglet (Crinia signifera): Third and fourth most commonly detected species across 25 and 22 sampling sites, respectively.

Fish
  • Longfin Eels (Anguilla reinhardtii): Most commonly detected species across 35 sampling sites. 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.
  • Cox’s Gudgeon (Gobiomorphus coxii): Second most commonly detected species across 30 sampling sites, expanding beyond previously recorded locations.
  • 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, expanding its known range.
  • Australian Bass (Percalates novemaculeata): First record for Hornsby Shire, detected at 8 sampling sites.
  • Bullrout (Notesthes robusta): First record for Hornsby Shire at Berowra Creek.
  • Flatback Mangrove Goby (Mugilogobius platynotus): Detected at Seymours Creek, expanding its limited occurrence records.
  • Flathead Gudgeon (Philypnodon grandiceps): New records for Hornsby Shire, expanding beyond previous locations.
  • Striped Gudgeon (Gobiomorphus australis): Recorded at 13 sampling sites, with new records within Hornsby Shire.
  • Dwarf Flathead Gudgeon (Philypnodon macrostomus): First record for Hornsby Shire at Sams Creek.
  • Flat-tail Mullet (Liza argentea): New records for Hornsby Shire, expanding beyond previous locations.
Introduced Species

Thirteen introduced critters were detected - 10 species and 3 genus - raising concerns for local biodiversity. These included: Black rat (Rattus rattus), Brown rat (Rattus norvegicus), Common starling (Sturnus vulgaris), Domestic pigeon (Columba livia), European carp (Cyprinus carpio), European rabbit (Oryctolagus cuniculus), Goldfish (Carassius auratus), House mouse (Mus musculus), Saw-shelled turtle (Myuchelys latisternum), Song thrush (Turdus philomelos), Genus of mosquitofish, Genus of rainbowfish, Genus of salmon and trout.

Saw-shelled Turtle (Myuchelys latisternum): Detected at Joe Crafts Creek, posing a potential threat to native turtle species.

Song Thrush (Turdus philomelos): New record for Hornsby Shire, detected along Colah Creek.

European Carp (Cyprinus carpio): Limited presence in lower Berowra Creek and Colah Creek, raising concerns for competition with native species.

Pig, Sheep, Cattle: possible explanations of the presence in the urban creeks could be run-off from garden manure or dog poo.

Salmon/Trout: detected at Georges Creek – possibly contaminated eDNA? Or maybe someone has thrown their fish lunch into the creek?

View the Data Dashboard

View an additional Data Dashboard from EnviroDNA Laboratories and their written report.