Central South Island News

Drought means a Tough time for Trout.
Graeme Hughes, Fish and Game Officer.

The long spell without significant rainfall has caused river levels to drop and Central South Island staff have been busy salvaging fish from drying rivers and streams.

The worst effected so far is the Hakataramea River, the largest tributary of the Waitaki River and an important trout fishery. The Hakataramea River attracts many  anglers from the region and a greater number of non-resident anglers.

While the mean flow is recorded at 5.25 cumecs it seldom flows at anywhere near this volume during the fishing season. Irrigation restrictions begin at 1.0 cumecs and at 500 litres per second all irrigation from the river is prohibited. While irrigation restrictions are in place not all takes have any form of gauging therefore monitoring of take is not possible. Alarmed at the rate of decline and the sight of many irrigation schemes still operating, a call to have the flow gauge rated, was made to Environment Canterbury by Fish and Game. The flows recorded at this gauge dictate the irrigation restrictions in the Haka Valley. Results showed that the recorded flow was within acceptable limits.

 Presently the Hakataramea River is flowing at a pitiful 674 litres per second and irrigation will continue until a further decrease in volume of 174 litres per second.  This will mean further drying and loss of habitat and mortalities of fish species numbering millions, in the main indigenous species, bullies galaxids and eels and all species of sports fish, rainbow and brown trout fingerlings and salmon smolts trapped on their downstream migration to the  ocean. The state of the Hakataramea River demonstrates the woefully inadequate minimum low flow and is only one of several rivers similarly affected.

 Readers may think that millions of fish lost to be complete exaggeration and if there are that many why is Fish and Game not saving these vast numbers. Many thousands are but my guess is many more are lost. For example in these drought periods large numbers of White-faced Herons, one flock consisting of 27 individuals, patrol the shallows, these conditions suit them admirably. Their long legs, neck and bill fish particularly well in the receding pools and shallows runs, and their appetite appears insatiable. I received a lesson in their fishing prowess when late in the evening I decided a pool containing some 300 fingerlings  could  wait until the following day. When I returned to the pool the next morning I thought I was mistaken as no fish could be seen. I searched further for the pool containing the 300 fingerlings. After days salvaging many pools look the same. I eventually returned to the first pool visited and came to the conclusion after seeing feathers and footprints that while I was having my breakfast the herons were having theirs! I may have expected the herons to take a percentage but to take the very last fish indicates to me that flocks of herons have skills and infinite patience to account for the lot. Little Shags, Terns and Harriers take their share but herons are the most numerous of the pisciverous species.

It is always surprising in times of drought how many adult fish are captured and the size and condition factor of the  fish caught. In the Hakataramea River Rainbow and Brown Trout appear to be common in the 1 to 2.5 kg with a 3 kg specimen taken quite regularly. The condition factor are high with “rainbows” invariably being better than “browns”. While the declining flows account for the crowding of adults it can be estimated from the numbers netted, fish per kilometre of river during times of adequate flow and it becomes obvious despite the river being small, anglers see only a fraction of the population.
 
Fish salvage has not been required on this scale for about 5 years. To date approximately 4000 to 5000 juveniles salmonids have been captured, 80% brown trout, 20% rainbow trout and 20% Chinook salmon.  3 km of river bed has produced 50 to 60 adult trout,  60% “brown” 40% “rainbow”. Eels number about 30 from 300mmm to a metre in length, bullies, Upland and Common bullies have been rescued in their hundreds with only a handful of galaxids, Common River galaxid, caught.

Conditions in remaining flows and deeper pools are not conducive to the salvage of fish. Netting is not possible due to didymo, filamentous algae and prolific growths of Water Buttercup and Curly Pond Weed. Electro fishing with a back pack unit is the only effective method of capture. It is a very slow process, fish are captured one by one, when compared with dragging a fine mesh seine net through a pool and catching hundreds at a time. All fish captured have been released into permanent water of the lower Hakataramea or into the Waitaki River.

Didymo Extends its Range but suffers on the way.
Graeme Hughes , Fish and Game Officer.

I visited a stream, where I was told a prolific growth of algae had appeared and that it might be didymo. I assumed it would be Gomphoneis the native look alike. The Otiake River is a small tributary of the Waitaki River but seldom reaches it excepting after a very heavy rain event and there hasn’t been one of those for many  months.  It is not a sport fishery, it’s only a metre and a half wide and has perhaps an average depth of 100mm  deep. The only vehicles that cross it are 2 farm trucks which don’t go anywhere near water with didymo. As the crow flies it is 7 kilometres of dry riverbed to the Waitaki.

I was wrong! It was not an indigenous algae, the stream was choked with didymo. It was the rapid rate of growth which attracted the attention of the landowner and although he had not seen didymo before the speed at which it grew made him suspicious resulting in his call to the author. How did it get there? No fish migration, no trout , no anglers, no boats. Birds appear to be the most logical vector. Although the water is not deep enough to encourage shags, perhaps another web footed species, shelduck ,occasional visitors on the property, are responsible.

Didymo was identified in the Maerewhenua River in the latter part of 2007. The proprietor of the Danseys Pass Holiday Park which is located on the banks of the Maerewhenua River has been monitoring its progress. A keen angler, he first observed didymo in the Maerewhenua River close to his Holiday Park the second week in October. Interestingly enough he has a theory how didymo arrived in the upper river. He blames  shags as where they land, the same place every morning, is where he first discovered the didymo growing He called me recently to inform me that the didymo is all dead!  I asked him how dead was dead. He said it had turned white and you can just wipe it off the stones with your hand. He said there has been no further movement of didymo since a fresh in December and he believes the die off began after the increase in flow. My fishing report river levels  show that the level of the Maerewhenua was at 4.5 cumecs, (a high flow), mid October 07. This flow decreased every week until it reached a low of 731 litres per second about 13th December followed by a slight in crease of 151 litres per second measured on  the 14th December 07.  After a short but heavy rainfall the flow increased to 6.5 cumecs a few days prior to 21st December 07. The following week it had dropped to 1.0 cumec.

In the Hakataramea River, didymo  in its early stages, small tufts about 20mm in diameter, is dying off as well. This die off occurred before the river stopped running in the Wrights Crossing area therefore low flow and increased water temperature is probably not a cause.

While the demise of local didymo infestations is great news, the die off poses more questions than answers.

Lake Camp Stocked
Hamish Stevens, Fish and Game Officer.

Lake Camp in the Ashburton lakes area was recently stocked with 2,500 eighteen month old rainbow trout. The trout reared at the Montrose hatchery were surplus to North Canterbury Fish and Games stocking programme and were kindly donated to the Central South Island region. Recent electric fishing operations in the spawning stream (Balmacaan Stream) have shown that the production of the stream is high with over 500 juveniles and fry caught in a 400m reach. Balmacaan’s tendency to lose connection with the lake as fry migrate downstream in summer is likely to be limiting the lake’s trout population.  The fish released will boost numbers and provide some easy to catch trout for young anglers who regularly fish the lake.

Salmon Fever!
Hamish Stevens. Fish and Game Officer.

Salmon fever has struck in South Canterbury with a large number of the elusive silver speedsters turning up in local rivers. Rivers such as the Orari, Opihi and Ashburton have been producing large feisty salmon however not in the same numbers as the Rangitata. Local tackle shops have been busy with anglers restocking and updating their salmon gear in the hope of landing the big one.

The season started well at the Rangitata with good catches of spring run fish in November/December and has continued on into January with both the number and size of fish surprising anglers. Fish weighing up to 13.6kg or 30 pound have been confirmed with reports of larger fish landed as well. Anglers have also commented on the excellent condition these fish seem to be in suggesting that conditions and food supply have been favourable at sea for the past three years. Around 380 salmon have been landed at the mouth with last week yielding 44 fish for one day! Mouth anglers have not been the only ones to have increased catch rates with river fishermen regularly taking limit bags as well. Salmon are well spread throughout the river now, allowing anglers who prefer quieter waters to fish away from the crowds. It has been about seven years since we have seen a run of fish like this and with just over two months to the end of the season it is likely that a few more will be added to the tally.

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