eDNA sampling & study

Eco-detectives at work: water sampling & eDNA.

In March 2022, the Waipu Waters team, part of the Piroa Conservation Trust, took a deep dive into the mysteries of the Waipu River catchment using Wilderlab Environmental DNA (eDNA) testing. Their mission? To get an idea of the state of five waterways and establish a baseline for future comparisons.

With just a cup of water, eDNA allows the identification of a wide range of species, ranging from fish and macroinvertebrates to birds, mammals, reptiles, amphibians, plants, fungi, bacteria and other organisms. This cost-effective method offers valuable insights into species distribution across time and space, aiding in monitoring biosecurity threats and understanding fluctuations in ecosystem health.

The team conducted the tests after a 10-day dry spell following heavy rain weeks prior. Each site was reasonably clear, except for the North River site, which was quite turbid. Eels were observed at all sites except Noth River. Notably, during a subsequent visit to the Millbrook Stream test site, a Parore was spotted feeding off algae on rocks, even though its DNA wasn’t detected in the eDNA samples.

Image: Biodiversity Wheel of Life – a visual representation of identified species, ordered according to their closest genetic ancestors.

Here are some key eDNA results from Waipu River catchment:
- DNA from various fish species were found in all of the sites, including Inanga, Redfin Bully, Common Bully, Giant Bully, Common Smelt, Long and Shortfin Eel, Banded Kokopu and, Torrent Fish.
- Snapper DNA was found in the Waionehu stream sample.
- Invasive species such as Koi Carp, Rudd, and Tench were not detected in our catchments.
- Diverse invertebrates and snails were identified, along with the DNA from introduced species like Peacock, Cattle, Rats and Possum.

Water quality was assessed using a Stream Health indicator called the Taxon-Independent Community Index (TICI). This index ranges from 60 to 140, with higher scores indicating better stream health. Results indicated that four of the waterways had a poor rating, and North River received a very poor rating.

Despite poor or very poor water quality in the Waipu River catchment, the eDNA tests revealed an ecosystem with a mix of native and introduced species. These findings establish a crucial baseline for monitoring waterways in the coming decades, with the hope that as catchment groups form and grow, and land use practices consider freshwater ecosystems, water quality, and biodiversity profile will improve.
To view the test sites and results, visit the Wilderlab interactive map and enter the job number.603734.

Image: Jon Hampson from NZ Landcare Trust taking a water sample for e-DNA testing from the Waihoihoi River, March 2022