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Michel Dedual – the man behind the most studied fishery in the world

by Sue Hoffart for Stuff.co.nz

After three decades of intense trout study, Taupō scientist Michel Dedual has theoretically reached the end of the line in his working life. However, the world-renowned researcher will continue to fish for answers and share his knowledge.

This story has been republished with permission from the author.

He might be retiring after decades of trout study, but Taupō scientist Michel Dedual says “I cherish the fishery too much to just ignore it”. Photo Credit: Christel Yardley/Stuff

This is among the most studied fisheries in the world,” the Department of Conservation (DOC) trout expert says on the eve of his retirement. “I cherish the fishery too much to just ignore it, I will keep trying to help as much as I can.”

Michel arrived in Taupō in 1991 with a master’s degree in zoology and a doctorate in ichthyology – the study of fish – as well as a deep love of fishing and hunting.

Growing up in the Swiss-French medieval lakeside town of Estavayer-le-Lac, he lived with four generations of his family and a grandfather bought his first rod. Young Michel slept with that fishing rod when he wasn’t roaming the lakeshore with other children, casting for carp and bream, pike and the very occasional trout.

Swiss-born Dedual has never forgotten the wow factor the first time he saw Lake Taupō. Photo Credit: Christel Yardley/Stuff

Epic-sized trout

Michel’s daughter was two when he and his wife Colette moved to New Zealand so he could complete a post-doctorate fellowship at Leigh Marine Reserve, north of Auckland. The couple’s son was born in New Zealand and the family was contentedly living beside the sea when Colette showed her husband a job advertisement over lunch one day.

“It was for a fishery scientist for DOC in Taupō and the description of the job was basically what I had done for my PhD. I thought this is unbelievable. It’s something made for me.

I’d been dreaming, reading those fishing magazines that show fabulous pictures of epic-sized trout in Taupō. I thought those pictures are fake.

He recalls the first time he saw the lake.

“I remember that my whole life, driving from Auckland, arriving at the top of the hill, and seeing Taupō moana. Wow. I couldn’t believe it.”

The gin-clear rivers were even better than he expected and standing in Tongariro River felt like a kind of pilgrimage.

“I’d seen so many pictures and I thought, now I’m in the middle of the grail. I went for the interview, then went fishing that night. Yes, I did catch a trout.”

He also nabbed the job, which compelled him to study trout and its habitat in order to guide management of the fishery.

As a child, Michel Dedual slept with his first fishing rod, which his grandfather bought him. Photo Credit: Photo Credit: Christel Yardley/Stuff/Waikaito Times

Envy of the world

On arrival, in autumn 1992, the multilingual scientist – he speaks four languages - found vast amounts of data. Fish size had been monitored and recorded as far back as 1896 when rainbow trout were first introduced to the region.

He could see which years fish numbers dropped away when trout health waxed or waned and even gauge the disruptive effects of Ruapehu’s 1995 volcanic eruption. Michel has pored over lake water quality records and historical photographs to help understand which factors most affect trout health.

He has led experiments that tracked fish in the rivers and lakes, noting survival rates after trout have been caught and released or travelled through a turbine.

More recently, his work has focussed on the human side of the equation, including the ways farming intensification or regulation or fishing licence sales affected the trout population. He has also spoken with anglers who have been visiting the region for decades, noting their observations and concerns.

“All that helped us tremendously, to understand the fishery so we can look after it.

We’re very lucky. Because Taupō is small in geographic terms, we can study it intensively. The reality is, not many places around the world have studied such a small system over such a long period of time. When I’m talking to colleagues in California, Australia, Canada, France, Switzerland, they envy us.”

From Taupō to the world

Michel has addressed international fishery conferences and co-authored a book, Understanding Recreational Fishers, alongside fellow scientists from around the world. The United Nations placed him on an expert panel and he has received plenty of calls from professionals who have read his published studies and yearned to know more.

Some have contributed their own expertise, like the economist who helped calculate the financial benefits of fishing. Or the Canadian mathematician who helped sift through spawning run data and marry it with the effects of trophy fishing on Lake Otamangakau in the Taupō district. The latter collaboration is helping to guide the way that particular lake’s fishery is managed.

We can show the effects of human interaction, show at what level of pressure you start to lose fish numbers and size. Then we can turn to the anglers and say, tell us what you want. Do you want lots of fish? Or fewer fish but big ones?

He views this kind of management process as his legacy. Thanks to all those decades of research and science, it is now far more feasible to predict the outcome of a particular decision.

“The fish have taught me nature does the best job ever and that managing the fishery is mainly about managing anglers, not the fish.

“The fish have taught me nature does the best job ever and that managing the fishery is mainly about managing anglers, not the fish.” Photo Credit: LoveTaupō

So much knowledge

Our job is to maintain a sustainable fishery. We want the best for everybody.

We involve all the stakeholders – Ngāti Tuwharetoa, DOC, the fishery advisory committee that represents all the fishing guides, shops, moteliers – and we’re putting the responsibility back to anglers.

“Personally, my deep wish is to show my children that I have been doing my best to slow down the degradation of the environment. Probably the ultimate reward for me is that they both have an interest in ecology, fishing and fishing management.”

The scientist will continue to stalk trout in his retirement, which kicks off in early May. But he will be selective about what he takes home.

“I have changed my view about fishing a lot. When I first started working in Taupō, I’d fish before work, at lunch break, after work and during the night. But I have measured the stress levels in fish, how they are emotionally affected by capture, how they recover from it. I know it’s not a picnic to be taken so I don’t want to annoy them and put them back in the water.

Now, I only fish for the table, for the fish I need to eat. These days, I spend far more time watching fish or talking to other anglers than I do fishing.

He also expects to field a few phone calls from colleagues in Taupō and around the world.

“I’m proud of what we have achieved here and I still want to be involved. We have built up so much valuable knowledge that hopefully will not be lost.”

" It is a very easily accessible fishery, half way between the North Island’s two main centres" Photo Credit: LoveTaupō

What makes the Taupō fishery exceptional?

Many reasons.

1. It is a self-sustained fishery - no trout are being released in the waterways - set against a majestic backdrop of mountains and forests.

2. The mainly-pristine lake catchment is situated within Tongariro National Park and the recreation parks of Kaimanawa and Pureora, which protect water quality.

3. A large number of streams provide the fish with plenty of premium spawning access while the lake offers good growing conditions; the trout are healthy and they have plenty to eat.

4. It is a very easily accessible fishery, halfway between the North Island’s two main centres, yet there are not enough anglers around to dangerously affect the perennialism of the population.

5. Finally, we now understand this trout population well so we can be confident about the fishery’s future and the measures we must take to protect it.

-Michel Dedual

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