RDR Fish screen update.

The following note has been compiled by Alan Brooks who is working closely, along with Paul Hodson, with RDR Management to confirm that the return stream from the fish screen, is fit for purpose and will return small migrating fish safely back to the river.

Fish Screen RDR.
You will be aware that the Project has been switched over with the Fish screens and bypass
operational.
We were invited to a workshop in 6/2022 by RDR in which this was the first time that we received plans for the actual bypass.
We had a critical look at all sections and made our views known to them.
There are a number of concerns that we have expressed.

• RDR have designed  a new weir / fish trap and are unable to replicate the BAFF trap calibration from the Angler requested Pilot for the new RDR weir. Anglers will recall that the data from the BAFF fish trap triggered the noncompliance that in turn removed the BAFF. There is no point stalling a world best practice fish screen with a poorly designed fish bypass. Worse still is that with the current verification process as it stands it will not be possible to verify the quantity of fish that are being returned to the river unharmed. Anglers will also recall that 98% of the fish used in the RSL fish screen trials were unaccounted for when their rock bund fish screen was evaluated for effectiveness. The fish bypass trap requirements remain that you release 1000 fish, trap 10%of the water and recover 100 fish in the box. The fish released  in the pilot were latter observed exactly where you would expect them to be and trap avoidance was also observed in the pilot.  The trapping process needs to work for both small and large fish. These requirements are detailed in the Fish Screen Verification Monitoring Plan as part of the settlement  for the Angler Appeal. The innovative design of the fish bypass did not consider preventing adult fish from migrating up its which is a consent issue. Ruff surfaces were found on the concrete of the fish bypass. Anglers have gone back with a detailed list of questions are still waiting for a response.

 

• The Drop bridge at the end of the screen structure, that controls water pressure and flows, creates a major drop into a shallow catchment area. It is our belief that the pool area should be significant to ensure fish safety and security to minimize damage.

       -     The bypass stream is extremely fast and violent, but the experts consider that is required to pass              the smolt back to the river quickly. We will review from test results.

• The Fish Trap for testing is of major concern. The experts have decided currently not to model the highly efficient prior trap. Preliminary test of their new model resulted in very few smolt being captured.

            Mc Kinnon`s Creek Salmon Farm has helped, so we are waiting an RDR update to understand any                  changes. 

• We have a major difference in opinion as to requirements of testing. RDR are only interested in capture of a significant quantity of smolt whereas we believe a statistical sample is best practice. That a good statistical sample would hold universal acceptance and approval for good business practice for future Fish screen applications.

 

• Predation is also of concern, and we will review as we proceed. So still some work to do.

      Will keep you posted. ***
 
                                             *****************************************
 
And now for the Great News - Salmon Legacy for Future Generation 
 
Please refer to the attached table which I believe establishes a Conservative Estimate of Smolt to Sea in Year 2022.
 
I believe this the best news we have heard for years and will start our Legacy that we have cried out for and all but given up on.
 
Mark these dates down on your Diary and tell all you fellow anglers to get ready.
 
Year  2022, this year  1.5million smolt will get to sea from the Rangitata.
 
Fishing season Year2022/23 we should see and increase year1 precocious Males
 
Fishing season Year2023/24 an increase in 2 years old fish
 
Fishing season Year2024/25 we are could get up to 10,000 but le us assume  4,000+ or more Adult returns
 
Logically the majority will return to the Rangitata, but it will also support the Opihi and Orari Rivers.
 
So, mark those dates and watch this space.
See table below for our calculations.
Rangitata River
Projected River Hatch and Smolt to Sea, Year 2022
Alan Brooks
Dated 8/21/2022
Totals
[1] Adult Salmon to Headwaters CSIFG 1800
[2] Females Run Mix 60% 1080
[3] Egg count
Conservative 3000 per Female 3240000
[4] Headwaters Hatch 50% 1620000
[5] Estimated loss to sea 10% 1458000
****RDR now clear***
[6] Say 1.5Million
**************************************
Rangitata Prior 3 Years
[1] Adult Maximum 500
[2] Females Run Mix 60% 300
[3] Egg count
Conservative 3000 per Female 900000
[4] Headwaters Hatch 50% 450000
[5] RDR Losses 50% min 225000
[5] Estimated loss to sea 10% 202500
[6] Say 203000
**************************************
Summary to Sea
Year  2022 1500000
Prior 3 year average 203000
Increase 7.389162562 Times

Return stream from RDR fish screen.