Geoff Thomas: Plumbing depths of Te Anau

Like all trout, Te Anau fish live in a beautiful place and like the same lures. Photo / Geoff Thomas

It was called a hydrology study weekend, and I guess a full understanding of water and how it works is pretty important for those in the plumbing industry when it comes to doing the job.

When the invitation arrived, it sounded quite daunting. The object was: "To further studies in the effects of stratification of different water temperatures, the turbulence and opaqueness effects of water at altitude, and their resulting effect on the durability of various types of plastics, alloys, man-made and natural fibres. Past studies have shown various inconclusive results using coloured and shaped objects being dragged at various depths by a portable mobile laboratory platform. Further research is justified as these objects have been known to snag on various types of water life."

But there are some clues hidden there and when 40 plumbers get together for a weekend away at a place such as Te Anau it is a safe bet that trout fishing might be high on the agenda.

So you fly to Queenstown, pick up a rental and drive to Te Anau. It's a lovely drive, around the Devil's Staircase, which follows the precipice that skirts Lake Wakatipu, then across the plains where five rivers converge at a town called, quite appropriately, Five Rivers. For those into trout fishing, and more so the classic dry-fly approach, this is as close to heaven as you can get in this country. And that is saying a lot in what is regarded as a mecca for fly-rod aficionados.

Then, when you pass a roadside store in a tiny place called Athol and the signs all proclaim you are at Stu's World Famous Fly Shop - which offers everything from fly-casting lessons to tackle, to guided fishing to hand-made trout flies, tackle and every type of fly fishing accoutrement - then you know you are indeed in the heart of trout country.

So you continue to Te Anau, another 45 minutes down the road, secure in the belief that you are heading into what will certainly be a serious angling experience. Well, in terms of the location anyway. The jury is still out on the definition of a hydrology study.

A gaggle of utes connected to trailer boats at the campground in the middle of the town is an encouraging sign. And the pre-study briefing at the big hotel is more promising. Teams are assigned to boats and a table covered with prizes suggest fishing is an important part of the study. The prizes are all caps, rods and reels. "As the star guest, we will pick you up every half hour and put you on different boats - they all want to know how to catch fish," the MC suggests. Hopefully, the trout that inhabit Lake Te Anau have similar tastes to those swimming around in Lake Tarawera or Taupo. Or the hopeful participants might be a little disappointed at the advice coming their way.

Some probing questions are aimed at the skipper of the first boat as it skims across the lake, which has to be one of the most picturesque in the country. The mountains that signal the start of Fiordland are reflected in the still water and the bush that crowds the shore promises a glimpse of deer. A helicopter winging high overhead with an animal hanging on a long strop confirms this is the heartland of the venison recovery business. Yes, the trout take the same lures. In fact, a black-and-gold toby is one of the most consistent. And he gets most strikes on a harling line made from one colour of lead-core line spliced to a long floating line.

Five colours of lead also get hit, so the trout are all in the top 10m, which is not surprising when the water temperature stays a constant 8C. Like other snow-fed or alpine lakes, the environment is basically sterile below the influence of sunlight, which is the key to weed and insect life, which in turn support the small forage fish like bullies. But these lakes are far less fertile than North Island lakes so the fish won't grow as quickly. Sure enough, the first strike is a little brown trout of about a kilo, long and slim; testament to the meagre dining available.

Ray comes alongside and we move to the next boat. These are novices, eager for information, so the tips are well received. "That trace is too short. The water is so clear that the trout can see your heavy line. Speed is a bit fast. The cobras and tobies should wobble from side to side, not revolve like a propeller."

It sounds impressive. And, later that night back at the weigh-in, they are smiling as they proudly show off their two little trout.

Some of the boats didn't catch a fish. Some boated five, and the winning trout was caught by a happy 10-year-old who wound it in after his dad told him to grab the rod when it bent. He took home an expensive rod and reel, which really earned a smile.

At a kilo-and-a-half, the brown trout wouldn't have earned a second glance in Rotorua. But then you don't go to Te Anau for the quality of the fishing. You go to study hydrology.