A back-up plan is being put in place by a Waitaki River salmon hatchery after it lost about 40,000 fish it was raising for release later this year.
The Waitaki Riparian Enhancement Society, a volunteer organisation, has a hatchery at Welcome Stream, on the south side of the river, and a salmon raising race at Bell's Pond, on the north side, in a programme aimed at increasing salmon numbers in the Waitaki River.
On January 2, the society lost about 40,000 salmon smolt - virtually all of this year's release. Only about 4500 remain.
Secretary Linn Koevoet said yesterday the loss was the result of a combination of didymo, a low flow in the river and an alarm system at the race which failed to operate and notify members about the water level.
Because the alarm failed, the first the society heard about the water level was when a local farmer telephoned, but it was too late.
The didymo, when in quantity, could block the race intake, particularly during flooding and had to be raked away by volunteers.
The good news was the remaining fish were doing well and on target to be released at a similar weight as last year's smolt.
As a result of losing most of its stock, the society had applied to the Otago Regional Council to build a small raceway about 18m-20m long at the Welcome Stream hatchery site.
It would initially house about 20,000 fry, which would be released into Welcome Stream and down that to the Waitaki River in batches as they reached an appropriate size.
The final release would be about 2000 smolt about 70g in weight.
''We are doing this to avoid having all our eggs in one basket, so to speak. These will be our return brood stock back into Welcome Stream,'' he said.
The return stock would be captured and stripped of eggs to be fertilised to produce the next release of smolt.
This year, the society will again set up a fish trap in the Hakataramea River to capture salmon for stripping. It will set the trap later in April, which will remain in place during May.
This was ''a very large logistical operation'' needing at least 10 members to set up the trap and volunteers to man it for the next 24 hours.
