Central South Island Region News Round-up, October 2006

Graeme Hughes, Fish and Game Officer

Opening day wet but productive.
After a lengthy dry spell and most of the smaller rivers receding, opening day in the Central South Island Region was subjected to rain and cool temperatures. The rain continued though out the day and from my analysis of anglers fishing in the upper river. above the Kurow Bridges, those who stuck at it hooked their limit (4 trout) with about half of the catch making good their escape. It seemed to be one of those days where as many fish were lost as were landed. Down river in the Duntroon area it appears the fishing may have been more productive, i.e. they caught more fish in a shorter time frame, illustrating the advantage of using a jet boat. The fish landed, predominantly “browns”, were in excellent condition according to one jet boater I spoke to.  However there was a down side to fishing the river below Kurow and that is the rampant growth of “didymo”.

Didymosphenia geminata
Some anglers were so fed up with “didymo” they went home early. Lines and hooks collected “didymo” as it drifted downstream in the water column. If your hooks touched bottom they collected “didymo” and, if you snagged on a submerged branch or rock your line quickly became festooned with “didymo”, grills on jet units blocked with “didymo”. In a big Waitaki River with many large and unforgiving willows a blocked grill at the wrong time in the wrong place could be fatal.

There have been several calls from the public reporting sightings of “didymo”. The locations include Hakataramea and Maerewhenua, Rivers and their tributaries. To date these sightings have all been indigenous “look alikes”
In the Waitaki River “didymo” has continued to grow and increase its range. At the end of last fishing season “didymo” extended from a point about 2 km above the Otiake River to the sea. Remembering that it was only discovered here in January of this year, this diatom has demonstrated an extraordinary rate of colonisation, invading some 50 km of river in less than 12 months!  During the winter it has moved slowly upstream from its last known location and has extended its range a further 5 kms. The upper Waitaki River is closed to angling during the winter months however there are other likely carriers.  Waterfowl hunters and jet boats use the river during the off-season, it is possible that birds and even fish may carry cells short distances along the river. Wherever I disembarked from the jet boat to check the shallows and likely riffles for the presence of “didymo”, cattle hoof marks were prevalent. Cattle wander across braids to access islands and grazing. This has been made easier during low flows which have been experienced in the Waitaki River recently. It’s not unreasonable to assume therefore that on the Waitaki River cattle could also be vectors.

With “didymo” in the Ahuriri and taking hold in the Twizel and Lower Ohau, this downstream drift will meet the upstream colonisation and by next fishing season it is probable that Didymosphenia geminata will have colonised the entire Waitaki River.

In the mean time “Didymo” will increase the angling pressure on those areas not yet affected. In the Waitaki River fishing without "Didymo" is only available from the Waitaki Dam downstream to a point midway between Kurow Creek and Kurow township, a distance of 7.5 kilometres.

“Didymo” in the Ahuriri River. 
In the Ahuriri River “didymo” extends from a point just above the Ahuriri North Branch confluence downstream to Lake Benmore.  As in the Waitaki River “didymo” has moved upstream to a point just below the “Native Cutting” a distance of about 3 kms from its upper most location during last summer. In the Ahuriri River unaffected fishing water remains in the upper reaches  downstream to a point below “Native Cutting”, about 26 kilometres of fishing water.

Check, dry and clean!
With many river users now aware that Didymosphenia geminata is a permanent fixture in their favourite fishing spot the check, clean and dry message has hit home, perhaps too late for some.  There is nothing like seeing this invasive diatom in full bloom to convince river users that you wouldn’t want to be responsible for spreading it further. After speaking to two anglers who arrived in the upper lower Waitaki River having fished unsuccessfully mid river I noted that they had been wading wet, no waders, just boots socks and long trousers. Had they disinfected their clothing and boots? No but they had made sure there was no obvious strands of “didymo” hanging on their boots. What about the water contained in their boots, their socks and trousers? After a good soaking in an approved household cleaner they proceeded on their way assuring an unbelieving Fish and Game Officer they would not be getting wet again as it was too cold to wade any more.

“Didymo” expert to speak at Annual Meeting.
If you want to know more about “didymo”, the work being carried out and the opinions of those involved with the task of finding a way to eradicate “didymo”, Dr Barry Biggs from NIWA will be a guest speaker at the Central South Island Regions Annual Meeting on 23rd November. The venue is the Alpine Stadium on Domain Ave in Temuka.  Barry, considered a world authority on the diatom, is an excellent speaker and his presentations are top class and always well received. Keep Thursday 23rd free and find out if there is a future for “didymo” affected trout streams in New Zealand. 

Late Rainbow Trout Spawning.

Something to consider while gearing up for the opening of High Country waters, it is highly likely known spawning tributaries will hold good numbers of “rainbows”  however if very recent observations are any indication many of these will be still spawning. While it is difficult to assess if this “lateness” is a gradual process and has been occurring , and many anglers will say it is, or, just a late  season, these fish are providing the next few years fish stocks and one has to ask, should they be disturbed, let alone fished for? The decision is a personal choice for each angler. Be aware however that only 10 days out from the new season spawning trout are still schooling and not yet paired up and many of the fish you will come across have still to excavate a redd and lay  their ova.

Hydro Lakes maintain enviable reputation.
The lakes of the Waitaki Valley are open all year and when the weather is appropriate there are often one or two boats and one or two shore based anglers fishing them. A town resident passes Lakes Waitaki, Aviemore and Benmore every day going to and returning from his work place. An angler of considerable enthusiasm, again when the weather was conducive to fish catching, he will stop for “half an hour”, in anglers’ terms that’s probably over one hour, and it is a rare day when he is not successful. Surprisingly the angler traffic begins in earnest from October the first. The traditional opening day is still a big day despite the lake not having a closed season. The preparation for such an event is an important part of the trout anglers’ culture and from a personal viewpoint the introduction of all year angling removed this pre-season anticipation. However, I’m informed that the trout “switch on” in October, or is it because there are more lines in the water?  The word is that Lakes Benmore and Waitaki are the top providers so far this month. Undoubtedly Lake Aviemore adherents have had similar results, they may be more secretive about their success.

Surface feeders begin to show.
Despite the scruffy weather we have endured, what occurs underwater is not necessarily affected by conditions up top. Although I cannot speak with authority on the subject, I have seen the results, there have been mayfly hatches during the day and caddis activity at night on the Waitaki River. After a day on the river a few hours spent after the evening meal could be to the anglers advantage.

Senior Fish and Game Officer Retires.
There will be few anglers and hunters in the central South Island region who are not familiar with the name of Graham McClintock. Graham has amassed almost 40 years of Fish and Game management, first with the South Canterbury Acclimatisation Society and latterly with Fish and Game New Zealand Central South Island Region. It is doubtful if there is a single fishery in the region he is not totally familiar with, a wetland where waterfowl are abundant he doesn’t know about, and if there is scrub filled gully or shale face where quail, and for the more energetic, chukor reside, Graham will have probably successfully hunted there at some stage of his career. It is said that no man is indispensable, but what word does one use to describe the huge gap left in our ranks with his departure.

Graham’s replacement, Hamish Stevens, began work with the Central South Island Region in October. Hamish supplied the following information to introduce himself to anglers and hunters of the region. 

“I was brought up on a farm in Northern Southland where I grew to love the outdoors and everything in it. It was this passion that led me to pursue a career in the outdoors, starting a degree in Zoology at Otago University in 2002. During my University years I worked on various farms in both the Northern Southland and Dunedin area as a farm labourer. 
In 2001 I assisted Fish and Game Otago with some voluntary work including trout surveys, data processing and licence checks. 
After the completion of my degree in 2004 I was employed by the Department Of Conservation (Coastal Otago Area). My work with the Department involved the maintenance of a trapping programme in the Catlins Costal Rainforest Park designed to protect the Mohua, a rare endemic passerine.

I have a wide range of interests the majority of which are in the outdoors. I particularly enjoy fly fishing, deer stalking, game bird shooting, tramping, cricket, water sports and just being in the outdoors.”