Anger over dry spawning grounds
Rainbow trout stocks in one of Southland's most productive and heavily fished rivers are set to take a dive, Fish & Game says.
It has accused Meridian Energy of poor management of water flows in the upper Waiau River, which has left trout spawning grounds high and dry.
However, Meridian Energy says it has met the statutory guidelines for water levels in Lake Te Anau and Lake Manapouri.
The energy company uses water from the two lakes , which are linked by the upper Waiau River, to power its Manapouri hydro station.
Te Anau Fish & Game ranger Bill Jarvie said anglers from the region are concerned about the dewatering of rainbow redds in the upper Waiau River.
This was because Meridian maintained relatively high flows leading into the start of the rainbow trout spawning season despite a National Institute of Water and Atmospheric Research of New Zealand (Niwa) forecast of low rain this year, he said.
Meridian had allowed flow rates over 250 cumecs, Mr Jarvie said.
That was unsustainable, given the continually decreasing in- flows to Lake Te Anau, which were now only about 40 cumecs, he said.
The high flows encouraged trout to spawn along the shallower edges, but now that the flow has been dropped the eggs and newly hatched fry would die buried within the exposed gravel redds, Mr Jarvie said.
Anglers would notice the loss of so many young fish in two to three years, he said.
The reduction of flows could hardly have come at a worse time. Hundreds of redds were now dewatered and further reduction in flow rates would greatly increase the magnitude of the destruction, especially during the July to September spawning season, he said.
Meridian corporate communications manager Claire Shaw said the company closely monitored the levels of the lakes and met the statutory Guidelines for Lakes Te Anau and Manapouri.
"Meridian only has a limited capability to manage the water and simply uses what comes in via rainfall, which varies with the weather patterns that can be sporadic and extreme," Ms Shaw said.
Inflows had been at an all time low during the past months and that had posed several issues for the whole community, she said.
Meridian Energy had to manage its operations so it could make the most of the water it got, especially in a year when the local and the wider South Island hydro inflows had been at an historic low, she said.
The company would continue to speak with Mr Jarvie and take an active interest in the spawning along with other local impacts the company had to manage as part of its operations, she said.
Te Anau angler Richard Jackson said he was angry a lot of fish would be lost.
"The most disappointing thing is that it is too late to do anything about it now," he said.
"Normally, only about 5 per cent of the eggs become fully grown fish; now we have 5 per cent of f... all," he said.
''If a poor old dairy farmer spilled effluent into a stream he would be fined. I think Meridian Energy should face the same punishment if they mismanaged their flow rates,'' Mr Jackson said.
Redd: The gravel nest where trout deposit and cover their fertilised eggs.
The redd is excavated progressively by the female, each pocket of fertilised eggs is covered by the next gravel she excavates as she moves very slightly upstream.
At the water temperature of the Upper Waiau, the time from "deposition" of the eggs to "emergence" of the "fry" is about 65 days.
- © Fairfax NZ News
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