Who’s splashing in Mermaid Pools?
The Manly Warringah War Memorial Park, over the years, has witnessed various kinds of stress related to the pressures of development being so close to the heart of Sydney. In recent times, having observed run-off and sediment in the Mermaid Pools, which is downstream from the park got us thinking about the well-being of the aquatic fauna in the area.
In an effort to hold despair at bay, we took action to find out what creatures are splashing about in the Mermaid pools in our backyard as well as assess the quality of water through the Northern Beaches Council and Greater Sydney Landcare’s Streamwatch initiative.
Lauren MacRae, Ecohydrologist & Volunteer at Mermaid Pools, does exciting research to ensure that science-based decision-making is used to manage surface and groundwater water environments.
Image © Mal Fisher
Lauren led the monitoring effort at Mermaid Pools to capture footage of aquatic fauna using Baited Remote Underwater Videos (BRUV), which is a non-invasive way to observe species and behaviours in aquatic ecosystems. An underwater videocamera directed at a bait is used to observe fauna, how they interact with each other, and how they interact with the bait. In the adjacent photo Lauren is explaining the deployment of the equipment, which was left in the water for an hour for monitoring in late September.
What we found
A Long Finned Eel and a Long Necked Turtle interacts with the Baited Remote Camera at Mermaid Pools
The main observations were as follows:
We noticed, three individual Long Necked Turtles (Chelodina Longicollis) - each characterised by the algal load on their shell and their size
A Long Finned Eel (Anguilla reinhardtii) was fascinating to watch
Many Gudgeons darting in and out at various times - some of these we were not able to ID to species level due to the water clarity, but there were definitely some Striped Gudegon (Gobiomorphus australis) like the one in the video with the turtle
Unfortunately we also noticed a couple of introduced mosquito fish (Gambusia affinins), but these didn't seem to be dominating
The Manly Dam region did witness rain in the days leading up to the filming and this may have naturally washed some sediment into the system causing the water to appear rather murky, which does not necessarily indicate poor water quality. However, to be certain in the week following, we conducted basic water quality testing to be certain.
Water sample was collected at the same location where the Baited Remote Underwater Cameras were deployed and tested for - pH, electrical conductivity, presence of phosphates and nitrates, turbidity and more.
The full results are awaited, but at a cursory level, the water was not found to be turbid and no presence of phosphates or nitrates were detected.
Image © Mal Fisher
It is exciting to see the turtles, eel and other aquatic fauna thrive in the waters despite the brief testing period, we hope to continue to conduct quarterly testing to keep the waters healthy as well as maintain the bushland that surrounds it.
Mermaid Pools with the Crimson Bottlebrush (Melaleuca citrina) in bloom. (Image © Aditi Das Patnaik)