Fish Passage Action Team Blog
Stories, updates, and insights from the field — tracking progress, sharing wins, and supporting better fish passage around the world.
Comparing Baffle Types in Round Culvert
Hi everyone,
We hope you are staying safe and well.
As shared a short while back, we have started using Computation Fluid Dynamics (CFD) to solidify what we already knew about culvert/weir baffles and their fish passage improvement features.
CFD is a powerful engineering tool used to simulate the action of fluids in a structure at a resolution not normally visible to the human eye.
It is well known that fish prefer deep water, complex flows and lower velocity, so it is exciting to see just how much of an impact different types of baffles have on the flow dynamics.
The independent CFD simulation was able to demonstrate the depth, and changes to velocity, with and without baffles installed.
The baffles included in this study were, Type 1 Spoiler Baffles, Type 3 Spoiler Baffles and Flexi-Baffles.
Below is a link to a Glide-show and we hope you find it as interesting as we did!
Contact the Fish Passage Action Team if you want to know more, and perhaps run a simulation on a structure that you are planning to remediate.
Mini-Hydro Intake Weir
Hi everyone
Below is a photo showing modifications to a back-country mini-hydro intake weir.
The original fish pass and minimum residual flow devices were not functioning.
The new design successfully allows expected species, all of which are climbers – longfin eels, and some migratory galaxiid along with invertebrates, to migrate upstream.
The fish passes comprise a flexible rubber channel (2 x Flexi-baffles) lined with looped mussel-rope. The rope is only attached at the upstream end to avoid debris jams.
The Minimum residual flow is controlled by another flexible baffle that pushes water to sides before overtopping.
Please contact the Fish Passage Action Team for more detailed information.
Video From OZ
Hi everyone
Below is a YouTube link to a video sent to us from Greg Wallis in Australia.
It shows common galaxiid/inanga (Galaxias maculatus) trying to navigate a vertical wall at a large box culvert.
Despite these fish showing amazing burst-swimming abilities to scale parts of the vertical wall, very few were successful.
Sadly (for the fish), many were picked off by an opportunistic heron.
Simple solutions such as baffles and ramps could vastly improve fish
passage at this culvert.
Enjoy
Wetland habitat improvement
Hi everyone
Following the restoration of fish passage into the Pongakawa Wetland (Bay of Plenty, NZ), the upstream habitat has been further enhanced by deploying Floating Nurseries that provide shade and refuge for aquatic and terrestrial species while also improving water quality. Click on the link to the Glide-show – Enjoy!
Link to glide-show: https://spark.adobe.com/page/U2jng2H1a7oXB/
Hot off the press
Tim’s short video showing a family of grey teal ducks (pārera)
using a Floating Nursery – literally! https://www.youtube.com/watch?v=KvV2W0n2tHo
Eels Swimming Cross-Country
Hi everyone
It is widely believed that eels can cross land between water bodies however little is understood as to how or why.
This rare footage captured by Tim Olley shows a medium-sized NZ Longfin eel taking advantage of a flood event to migrate upstream across what is normally dry land.
Much is known and documented about juvenile eel migration, but less so for adults.
Note how the eel is using burst swimming between long rest periods as they do in natural settings.
Less vegetation and an unnatural stream bed means that eels have to work harder when migrating in such situations.
Also, due to a lack of cover, eels are very susceptible to predation from birds at these times, as we have witnessed.
Do older shortfin eels have this upstream migratory urge like longfins?
Enjoy:)
Pongakawa Wetland Reconnection
Hi all,
Some of the Fish Passage Action Team were recently involved in a very satisfying restoration project.
It is rare that we get the opportunity to completely remove culverts in an effort to restore fish passage so we wanted to share this with you.
See what two workers and a small excavator can manage in a day.
Alex put together this short “Glide-Show” so you can scroll through it at your own pace.
Favourite Video Revamped
Hi everyone,
During the lockdown, we have revamped one of our favourite videos that has been enjoyed by ecologists, engineers, and many others in helping to understand why migrating fish need complex flows.
The video highlights the importance of complex flows and how baffles can help to achieve this.
We have lots more interesting fish passage videos in the wings, so watch this space!
Stay Safe,
Fish Passage Action Team
CFD Modelling
Hi everyone
Many of you will be aware that observing, measuring and understanding the complex flows in which fish move is very challenging.
Below are a few interesting images that have been created by the Fish Passage Action Team using CFD modelling.
There are many options for displaying the results, but the fantastic thing is having the ability to see the velocity and direction of the flow down through the water column.
We are currently building a library with models using different flow rates, culvert types, baffle configurations etc.
If you have a particular project that would benefit from this type of simulation, don’t hesitate to get in touch with the team directly.
Note: A table with the model’s parameters is in the top right corner of each image.
Eel climbing 3 surfaces
Tim Olley has shared this video showing the same juvenile eel climbing up three different surfaces, including mussel-rope.
Access to Spawning Sites
| Hi everyone Fish need to have access to spawning sites. Here is a link to a really nice video showing stage-one of a manmade spawning and nurturing site for inanga (galaxiid maculatus) though many other species with make this place home. The pools will soon be planted and connected to the main canals leading to the Little Waihi estuary. Twice daily tides will flush the ponds and provide the potential for spawning each autumn. This project is being led and funded by the Bay of Plenty Regional Council. Enjoy |
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“99% of barriers in Rangitaiki fixed with simple solutions under $200”
– RNZ on ATS Environmental initiative
“Installed flexible baffles in culvert—juvenile galaxiid seen migrating days later.”
– Nelson City Council Trial Update
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