Fish Passage Action Team Blog
Stories, updates, and insights from the field — tracking progress, sharing wins, and supporting better fish passage around the world.
Nelson City Fish Passage Restoration Program
Here in NZ it was Conservation Week last week.
Barriers to Fish Passage, is certainly making the headlines, particularly with the announcement of the National Policy Statement Freshwater Management (NPS-FM 2020).
Nelson City, NZ has been ahead of the game, with a region-wide program well underway, remediating a range of structures with effective, robust, and low-cost fixes.
The city council has posted this excellent short video highlighting some of the work completed so far.
The NCC fish passage program is very simple – see below:
1. Locate structures in the waterway
2. Survey of structures in waterways and give a “Current Status”
3. Identify barriers to fish
4. Consider desired and undesired fish species
5. Propose mitigation and costs
6. Propose some form of prioritisation for remedial works
7. Undertake remedial works
8. Reporting and data management
9. Ongoing monitoring
Another YouTube version of the video below.
Field Day
I had a great day out in the field with a bunch of folk keen to do some learning with gumboots on.
Kelsey Tills of Rayonier kindly organised the day with representatives from Forestry (Rayonier and PF Olsen), local government (Waikato Regional Council), contactors and a community care group.
Despite the rain, we manged to visit a number of culverts and discussed both new installations and remediation of existing structures, with a view to improving fish passage.
The Fish Passage Action Team are happy to assist and or lead workshops or training days.
Photo – Glenda Betts
Note: This culvert is under a road that crosses a wetland – there is no stream as such, just what was excavated during the installation.
Focus On Maintaining Fish Passage During Low Flows
It is worth remembering that lows flows and shallow water are challenges to migrating fish.
The video below represents remediation to an upgraded urban storm water pipe serving a small tributary of the Maitai River near Nelson, NZ.
The upgrade involved upsizing the pipe and removing the perch at the outlet.
– Base flows of the tributary are approximately 1L/S
– Pipe length 300M
– Pipe gradients range from 2%-12%
You will see an increase in the depth and width of the water along with bed-material beginning to accumulate.
Climbing Redfin
Tim Olley captured this rare footage of a juvenile redfin bully (Gobiomorphus huttoni) climbing up a retro-fitted mussel-rope with backing, into an overhanging culvert.
It reminds us that, given half a chance, many fish will navigate challenging obstacles.
What is not well understood, is what precise factors cause a fish to transition from a swimming to a climbing mode of locomotion.
Reservoir Video
Below is one of Tim’s videos featuring the culvert remediation project in the recently published “Lessons Learnt 8”.
There is some great underwater footage showing how fish navigate upstream utilizing the back-eddies and rest pools created by the flexible baffles.
For those that missed the write-up check it out here
https://www.doc.govt.nz/globalassets/documents/conservation/native-animals/fish/fish-passage/lessons-learnt-case-studies/lessons-learnt-008-installation-of-flexi-baffles.pdf
GIS Project
Jordie McDonald has completed a desktop GIS project highlighting the huge number of potential barriers to fish passage in the Northland Region of New Zealand.
The extent of the potential barriers is probably typical around NZ the rest of the world.
https://northtec.maps.arcgis.com/apps/MapJournal/index.html?appid=4342b312ac164e0aa83c9793936fa0b1
We will soon share a report on a large catchment where each site is visited and assessed. A “current status” is assigned to each in order to give a better picture of what is out there and what needs to be done to remediate. Enjoy!
Lessons Learnt 8
The NZ Dept Conservation Fish Passage Advisory Group website has a number of Lessons Learnt describing different fish passage remediation projects.
Tim Olley spent over a year researching and putting together this comprehensive report highlighting the effectiveness of flexible baffles in a long, steep culvert.
We are planning to make a PowerPoint and/or video of this report at some point.
Enjoy.
Click here to view Lessons Learnt 8
RIPRAP Followup
We received heaps of thoughtful feedback from engineers and ecologists regarding the last mail-out, so we have summarized the comments below. The projects in question are typically the often steep outfalls from culverts or other structures, as opposed to stream restorations or realignments.
Treatment of rock armoring feedback:
- Ideally surface-flow should be maintained with nature-like meanders.
- There is some evidence that small fish can make their way up through the gaps between the rocks but it is not ideal.
- Finer material may need to be added if it is unlikely to be transported and deposited by natural processes.
- Appropriate geo-textiles may need to be used. These may need to be impermeable.
- Adding of finer material will need to be managed to ensure large rocks still interlock.
- Armoring may need to extend further as velocities may be higher when all water is at the surface and the suface is less rough.
- Provision should be made to include vegetation within and overhanging.
- Precast channels can be designed to meander.
- If precast channels are used then the joints would need to be flexible and water-tight similar to the floating ramps.
- Precast channels would need to be anchored to ensure they do not tip and spill water over the sides.
This useful link to a very comprehensive Urban Storm Drainage Criteria Manual was shared by Iain Smith
https://udfcd.org/wpcontent/uploads/uploads/vol1%20criteria%20manual/08_Open%20Channels.pdf
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
Join our mail-out!
“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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