UC Freshwater Ecology Research Group

The People’s Choice segment of the university Visualize Your Thesis competition started on Monday, and voting is open until the 4th of August!

You can vote for your favorite video by liking it on YouTube. We hope that will be Lauren's! Link to the video here:

https://youtu.be/Eod5uFYzOjU?si=cfmdabmO2X07nG_h

Happy watching!

Additionally, if you are curious, you can access the rest of the submissions on the University of Canterbury Library YouTube page here:

https://youtube.com/?si=P1qaI4WRv95Epvop

The Braided River Aid 2025 Braided Rivers Seminar was held at Lincoln University last week, bringing together the inspiring work being done around the country to support our precious braided river ecosystems.

Prof Angus McIntosh gave a comprehensive presentation on the research that FERG and many other collaborators have undertaken on the Te Awa-o-Takatamira/Cass River (pictured), highlighting how the highly variable physical environment of braided rivers influences species and their interactions.

Both the recordings and PDFs of all presentations from this and previous years are freely available to view using the link below:

https://braidedrivers.org/2025-seminar/

📸Angus McIntosh

What’s in your Waterway Wednesday?

Although they may not be the most charismatic freshwater residents, we think that diving beetles in the family Dytiscidae deserve a moment in the spotlight!

There are 16 native dysticid species in New Zealand. Both the larvae and adults of these species spend most of their time in freshwater, preferring slow-flowing streams and weedy ponds, and can even be found in troughs. Adults can fly once they dry themselves out, allowing them to disperse to new habitats, a strategy that can ensure their survival through periods of drought.

Diving beetles live up to their name, diving deep underwater to hunt for prey. However, both adults and larvae need oxygen, and each life stage gets this in a different way. Larvae have gills, meaning they can breathe underwater. They can also get oxygen more efficiently by popping up to the water's surface and taking up oxygen over their cuticle (analogous to skin). Adults navigate this problem in a different way, trapping air under the hardened cover over their wings, allowing them to dive down for longer. Like dolphins, adult dysticids must return to the surface to replenish their oxygen before diving back down again.

FERG PhD candidate Martha features in the latest episode of Our Changing World! Listen to learn all about the conservation and research efforts involved in the protection New Zealand rarest freshwater fish, 'Jaws'. 🦈

📑 NEW STUDY: Jolly et al. assessed in-stream barriers in for their successful exclusion of invasive trout.

🐟 Species studied

River-resident galaxiids and non-native trout

🌏 Location

South Island, locations with known presence of threatened galaxiid species

🤔 The issue

Invasions by non-native fish species are a key driver of change in freshwater systems, impacting biodiversity and economies. The use of in-stream barriers to prevent or mitigate such invasions and protect native fish populations, known as isolation management (IM), has been increasingly reported.

However, despite the need to secure vulnerable populations, trade-offs between isolation and invasion are likely, and it is unclear if our current knowledge supports optimal long-term outcomes.

Aotearoa New Zealand has a history of using exclusion barriers to prevent incursions of introduced sports fish (such as trout) into native river-resident galaxiid (RRG) refuges, predominantly within the South Island.

👩🏽‍🔬 What did the researchers do?

The team assessed 37 natural and built in-stream barrier structures and predicted successful exclusion would be due to a combination of barrier parameters and habitat.

Additionally, they assessed global exclusion knowledge, conducting a systematic review and meta-analysis of peer-reviewed studies of trout barriers to examine the prevalence of quantitative barrier parameters in the literature.

💡 What did they find?

Drop height had the strongest relationship with exclusion in both the field survey and meta-analysis, and downstream pool depth was also negatively correlated with exclusion in the field data.

Less than a third (27%) of trout barrier studies identified by systematic review reported quantitative barrier parameters, and barrier height was the only parameter found to have a relationship with exclusion.

Only six (11%) of the quantitative studies described deliberate exclusion of fish for ecological gain.

👍 Any recommendations?

Trout barriers had successful outcomes in New Zealand, with galaxiid densities higher above successful barriers than any other position; therefore, there is evidence supporting barrier use in conservation.

👀 Read the full study: https://doi.org/10.1002/rra.4447

Modified waterways, otherwise known as drains, are a common feature embedded in New Zealand's agricultural and urban landscapes. Though unassuming, these waterways serve as both home and highway for a great diversity of freshwater life. Maintenance intended to keep these drains clear and flowing can harm taonga species and their habitats.

Te Wai Māori and Kitson Consulting have produced a brochure which highlights the importance of drains to freshwater biodiversity and summarizes good management practices which can reduce the impact of mechanical drain clearance on this biodiversity.

The PDF version of the brochure can be accessed freely using this link:

waimaori.maori.nz

Swim! Don't walk! to vote for your favourite (freshwater 😉) fish to win Fish of the Year 2025, before voting closes this Sunday at 5pm!

There are more freshwater contenders than ever. Let's make it the first year a freshwater fish takes the crown! Halfway through the competition tuna (longfin eel) were sitting third on the leaderboard and the fascinating piharau/kanakana (pouched lamprey) had made it to tenth place!

Whether you like to back a winner or an underdog, there are many stellar options to choose from! Click the link below to learn more about the contenders and vote while you still can!

Vote | Fish of the Year | Mountains to Sea Conservation Trust Cast your vote in Fish of the Year and show some love for our watery friends!

Introducing MSc student Liam Taylor!

Freshwater species have life cycles that are strongly coupled to natural flow conditions and are reliant on multiple connected habitat types. Freshwater ecosystems are becoming increasingly degraded, with altered flow regimes and reduced habitat connectivity. Species with complex life cycles are likely to be most affected by these changes, and populations living in altered environments may develop novel strategies to cope with these changes. For example, some migratory fish populations have become landlocked due to extensive anthropogenic dams and are no longer able to reach the ocean for their larval development stage. It is important to understand the dynamics of these more novel populations, as well as their vulnerability to climate change, in order to inform conservation measures to protect them.

Liam's project is focused on investigating the temporal and spatial dynamics of a landlocked kōaro population in the Te Awa-a-Takatamira / Cass River. Specifically, he aims to determine how kōaro use the braided river system throughout their life cycle, including how size classes differ in their lateral and longitudinal use of the river, and the environmental cues that drive movement throughout the system.

Liam's MSc project is funded by Fish Futures.

What’s in your Waterway Wednesday?

Though they may be confused for snails upon viewing their spiral “shell", these little guys are larvae of the caddisfly genus Helicopsyche. The spiral “shell” is actually a case made out of sand-sized particles similar to those of the larvae of other cased caddisflies; however, the spiral shape of this case is very unique and is only made by Helicopsychidae species!

These little critters are highly sensitive to aquatic pollutants, so they are typically found in bush-covered streams with superb water quality. Cased caddisfly larvae, including Helicopsyche, are an important diet item for our last Waterway Wednesday feature, whio!

Today we are resharing one of our earlier posts as we have an exciting update—this research conducted by former MSc student Olivia, supervised by Profs. Jono Tonkin and Angus McIntosh from UC and Dr. Nixie Boddy from DOC, has recently been published!

Native galaxiids are threatened by predation pressure from non-native trout and are also negatively impacted by low stream flows. Olivia investigated the interaction between these two pressures and found that the effect of trout on galaxiids is dependent on flow conditions, with galaxiids in drying streams experiencing less predation pressure from trout. However, the healthiest populations of galaxiids are found in trout-free streams with consistent year-round flow.

This research article is open access, meaning you can read it by clicking on this link: https://doi.org/10.1002/rra.4428

Additionally, you can check out the original post below for a 2-page summary of the research findings!