Fish Passage Action Team Blog
Stories, updates, and insights from the field — tracking progress, sharing wins, and supporting better fish passage around the world.
Keep Up The Good Work
Shane Scott has put together this short video showing some low cost fish passage remediation projects across North America.
Note the different configurations used to suit each site.
Also enjoy the great commentary with the Johnson Creek segment.
Contact Shane directly for more info – ph number at end of video.
RIPRAP
Stop this disaster!
It is now common practice to use large, similar sized, rip-rap (boulders) to manage downstream erosion at structures.
Above is typical example of a recent culvert upgrade where extensive rock armouring has caused water to be sub-surface and spread over a wide area during most flows, making upstream migration almost impossible for most fish.
The rubber strip and rope were added afterwards to try to help with fish passage.
We need your help to share ideas on how to better provide fish passage while still meeting erosion control requirements.
– Discussion Paper-
The challenge – maintaining fish passage through rock armouring, especially during low lows.
Below is a concept that may provide passage for small fish, while still achieving erosion control.
A series of precast channels maintain a flow path that may be completely covered with large rocks, providing gaps remain between individual rocks.
Installation process
- Excavation as part of structure installation
- Suitable geo-textile laid
- Precast channel fitted to apron at outlet. Also baffles fitted on apron
- Rock rip-rap placed either side of ramp
- Channel covered with rock rip-rap
Points to consider:
– Channel design
– Installation
– Cost
– Durability
– Effectiveness (short and long-term)
– Planting
Brook Channel
Restoring fish passage is great, but don’t forget about the habitat!
In natural environments, overhanging vegetation is important for shade, refuge and a food supply, but also helps fish migrate up along the edges of waterways.
This video shows a trial project funded by Nelson City Council, where PlanterPods and Flexi-baffles are working together to provide habitat and passage, along a section of heavily modified urban stream in New Zealand.
Box Culvert Remediation For Fish Passage
Please take a minute to watch this short video showing the effects of flexible baffles fitted to the invert of a box culvert.
This is a newly installed culvert (replacing an old smaller round one) under a public road in the Bay of Plenty, New Zealand.
It is hoped that over time, smaller bed-material will accumulate among the large rip-rap and between the baffles, creating a more natural habitat.
Also watch out for the juvenile galaxiid (whitebait) that were seen, just a few days after the installation, making use of the baffles to migrate upstream. Enjoy!
Mass Migration
We hope you are all still healthy and making the most of the lock-down. The Fish Passage Action Team are taking the time to put together more resources to share with our growing audience.
Below is a link to a short video showing the challenges migrating elvers meet, even from their own species, when obstructed by man-made barriers such as perched culverts.
In nature, migrating fish will encounter delays due to natural features, however many have evolved to make mass migrations to ensure that at least some will get through to continue the breeding cycle.
Man-made structures and/or barriers interfere with this process and upset the natural balance of freshwater species.
It is not uncommon for other species, such as birds or rodents, to also take advantage of any delay in upstream migration. To grab and easy meal.
Enjoy.
Fish Passage Remediation
Below is a link to a very interesting article posted by the NZ Dept of Conservation that discusses the importance of restoring fish passage to benefit all aquatic species.
Enjoy.
Click here for article
Natural Barriers
This is an important positive message about fish passage.
We are seeing an increase in the use of the term “natural barrier”, particularly when prioritizing remediation of man-made structures/barriers.
As it happens, many species of fish have evolved to navigate what humans might think are impossible features.
There are now a number of effective fixes that are very low cost, thereby eliminating the need to prioritize in the first place.
All structures in waterways need to allow for fish passage regardless of what is above or below them.
Please watch and share this short video
Amazing Climbing Koaro
This is a short video by Tim Olley showing larger bodied koaro (Galaxias brevipinnis) “climbing” up a natural feature.
Larger bodied fish tend to use a burst swimming action unlike the juveniles that typically “flip-flop” further out at the edges of the splash zone.
Smaller fish tend to be able to climb steeper slopes.
Climbing Eels
This rare footage shows both small and larger eels trying to navigate a natural feature.
You will see that larger bodied specimens are unable to utilise the wet margins or splash zones.
Remediation techniques should offer a range of options to give migrating fish choices to best suit their needs.
How Fish Swim – Video Showing How Fish Utilize Small Eddies And Boundary Layers
When designing new structures or considering remediation for existing ones, it is important to consider the swimming ability of the fish likely to pass through or over the structure.
This short video shows that small or juvenile fish operate at a very fine resolution not able to be easily measured or observed.
You will see in the video fish riding very subtle pressure waves within complex or nature-like flows that can have a different velocity and/or direction in the same location.
It also shows fish climbing vertically when the conditions allow.
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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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