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LOW FLOWS
It usually happens once or twice each year, often not until March or sometime in February. This year we have very low flows in the rivers at the end of January. I hope this is not a sign of even lower flows to come.
Most anglers realize that low flows are a time of stress for trout. The water warms and places to hide diminish. Scientists have discovered that trout populations are limited by the amount of habitat that is available at low flows. That means the number of trout that can live in a river depends on the amount of cover or hiding places there are when the river is at its lowest annual flow.
Large rivers like the Mataura can hold more fish than rivers such as the Aparima because of this reason. Another problem at low flows is the increased effect of pollutants. Where discharges are diluted by river flows the volume of the flow is the factor that controls the effect on the fish that live in the river. The Mataura is a river that receives relatively large inputs of waste from factories, especially at Mataura. When the river shrinks from lack of rain the effect of the waste discharges grows, algae growth proliferates and the river looks less pure. Water temperatures increase too. This allows weed to grow more and adds to the risks that trout are faced with.
At temperatures of more than 19 degrees trout cease to grow but they can survive in temperatures in the mid-twenties. Temperatures around 12 are about right. At present most of the rivers' lower reaches temperatures will be closer to 20.
Despite this worrying trend at present conditions are no worse than they have been in the past. However, it will be a relief if we got some rain over the next few days to give the rivers a bit of a freshen up.
Trout are rising consistently in the Mataura. Lower reach fish can be caught with persistence and small emerger flies. Some experts can catch 30 - 40 fish per day but most of us should be happy with one or two. The lower Oreti is producing trout regularly to fly anglers during the day-time too; there are bound to be a few salmon lurking in deep pools for the threadline angler too. Don't expect to catch one when you go out but then again, don't be too surprised if you do catch one either.
The Oreti usually has a steep bank along one side of its pools and these often have collapsed clumps of grass and soil along them. Trout wait near these and can be caught on a small dry fly cast so that it drifts near them. Low flows bring good fishing conditions to places near to where most of us live. Catch some before the rains.
Maurice Rodway
Southland, New Zealand E-mail: fishgame@southnet.co.nz Article ©1998 Maurice Rodway, All Rights Reserved. |
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