An aging communist armed with oxygenated fish tanks in his car roamed New Zealand's countryside for decades in a bizarre crime spree that forever changed our environment. It led him to be called one of the country's worst environmental criminals; but to some, his legacy is much more complicated.

Stewart Smith is an old man, propped up on a zimmer frame in the morning darkness.

He is delicate on his feet, re-learning how to walk after surgery on one hip and both legs, watching in silence as they raid his workshop, the product of his life's work.

It was 5am, and they numbered around 30. They broke the chains on the fence surrounding the building. They quietly moved past a giant concrete tank sucking water through a bore and feeding it through the building.

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Many decades earlier, the old man earned the nickname Shotgun Smith for how aggressively he defended his West Auckland garage from thieves. Now he is 92-years-old, living alone in his West Auckland lair, pondering what to say when they discover what he has in his tanks.

KATHRYN GEORGE/STUFF Stewart Smith has been called an 'arch environmental criminal' in New Zealand.

It happened by pure coincidence. A few weeks earlier, a boy was alone and wandering the streets in Massey. He came across a Caltex petrol station; next to it, he saw a crumbling old garage, paint peeling from the exterior.

Something catches his eye. Near the petrol station forecourt, a creature is wriggling in the gutter. It looks like a kōura, but larger; most strikingly, it has a steely dark shell.

The boy goes home and tells his dad. When they return, dad wraps the creature in a sweatshirt, and they bring it home to their fish tank.

He rings the Department of Conservation, which sends someone out to investigate. The official immediately recognises what he's looking at; a West Australian smooth Marron, a species not found in New Zealand.

Word gets around, and several agencies discuss next steps. They know that, based on where the marron was found, there were likely to be more.

A biosecurity report prepared two months later said marron "have the ability to become widespread throughout New Zealand, invade many habitats, affect ecosystems and all levels of the food chain".

They needed to move quickly, so the raid happens 16 days later, early on a Monday.

For most of the day, Smith watches. At first, he says nothing. Then they figure out what he's up to, and he knows the jig is up.

CHRIS MCKEEN/STUFF Stewar Smith's commercial garage in Massey, where he bred exotic fish to illegally release into waterways.

POMMIE BASTARD

About a decade ago, a writer named Bryan Winters was told about a communist who loved to fish.

It caught his interest

"He'd left quite a lot of money, and part of his last will and testament was he wanted a book published telling his story," Winters says.

Stewart Smith had even suggested a title: That Pommie Bastard.

The life of J. Stewart Smith was long, colourful, and driven by an uncommonly strong sense of purpose.

By the time he died in 2008, aged 95, Smith had left a permanent legacy in his adopted country's bloodstream – its network of ponds, rivers and lakes.

This account of Smith's life and legacy is based on official documents and hundreds of pages of Smith's personal notes obtained by Stuff, as well as interviews with people who knew him. several of whom requested anonymity.

They reveal an enigmatic figure largely forgotten in New Zealand's recent history, but one who has had an outsized, and permanent, impact on the country's environment.

"Imagine if one guy was responsible for the introduction of rats, possums, rabbits, stoats and pigs to New Zealand," one former official familiar with Smith's activities says.

"Stewart Smith was pretty much that guy, but he just did it to freshwater ecosystems around the country."

KATHRYN GEORGE/STUFF Stewart Smith dedicated his life to introducing pest fish to New Zealand waterways.

Over the course of four decades, Smith released many thousands of fish into rivers, lakes and ponds. The vast majority of his liberations were illegal.

He was prosecuted at least twice, but Smith continued his releases well into old age. Age made him bolder, more audacious, culminating in the 2005 raid on his home, which likely stopped what Smith planned to be his last, and most significant, liberation.

"He's had more impact on freshwater than any other single human being," another former official who pursued Smith says.

"He was really one of New Zealand's arch environmental criminals."

For much of his adult life, Smith would breed exotic fish in a network of tanks behind his Massey workshop and release them into waterways.

He outfitted his car – initially a Ford Zephyr, and then a Lada Niva – with oxygenated fish tanks that could keep fish alive for days.

He would liberate the fish wherever he could, with or without the permission of land-owners. He would recruit accomplices – sometimes adults, sometimes children – in raids on farms, dams, and public waterways.

Smith diligently chronicled his activities.

According to his own records, Smith was personally responsible for liberating more than 15,000 fish between 1964 and 1987, in hundreds of distinct locations. The vast majority were in the upper North Island, between Rotorua and Kerikeri, but extend as far south as Christchurch.

He liberated fish in small farm ponds and major rivers; pristine dune lakes and city water supplies. His address book bulged with people who had asked him for fish, which he always supplied, sometimes as far away as Wellington.

He would smuggle fish eggs into the country by hiding them in his pocket while going through customs, and once, in the vegetable pantry of a passenger ship. He established a new species in New Zealand from a handful of fish eggs an associate sent to him in the post.

"He was clearly a hugely resourceful and tenacious man, with an incredible amount of passion and drive," one of the former officials said. "It's such a shame when you think how that energy could have used towards something positive."

The fish he liberated, generally speaking, flourished.

Much like New Zealand's native land birds, its freshwater fish had evolved in an environment with few natural predators. New species can shake up an ecosystem that evolved in a delicate equilibrium - and in New Zealand, the result has been chaotic.

KATHRYN GEORGE A map showing many of Stewart Smith's liberations.

A COARSE HOBBY

To understand why Smith did what he did, it pays to understand the long-simmering battle over who gets to fish what.

New Zealand has several dozen native freshwater fish, most of which are nocturnal, discrete, and tucked away in streams far from civilisation. Few of them grow larger than 10cm; they don't make for great angling.

Recognising this, early European settlers decided to bring their favourite sports fish with them: Trout. Trout flourished in New Zealand's cooler waters, with limited competition from native species. The trout fishery is now so prosperous it attracts anglers from around the world.

Some immigrants, including Smith, did not grow up trout fishing, which in England was a sport reserved for the elite. They fished for the so-called "coarse fish" – among them rudd, perch, tench and carp, named for their rough skin.

This class divide bled into New Zealand. While trout soon followed the immigrants, attempts to bring in coarse fish were rebuffed, largely because they would compete with trout.

And so Smith, who paid dues to New Zealand's communist party for much of his life and had a pathological dislike for social hierarchy, sought to equalise the playing field.

Smith's liberations began in the early 1960s, work he did concurrently with running his commercial garage on Triangle Road in Massey.

He started with one of the most damaging coarse fish: Perch.

Perch were already in New Zealand, having been brought from Tasmania in the 1860s, and were predominantly found in Canterbury and Otago. They were not widespread, for good reason – perch are carnivorous and have a ravenous appetite. Not only do they eat other fish, they also eat each other.

Smith likely started with perch because he had easy access to them. In 1905, a population had been legally introduced to Lake Rotoroa in Hamilton city, and had survived. Smith, with the help of two local boys, took perch from the lake and spread them around Auckland.

DOMINICO ZAPATA/STUFF Hundreds of perch were legally introduced to Lake Rotoroa in Hamilton city in 1905.

His notes show he introduced hundreds of perch to Auckland lakes in the 1960s, primarily in Western Springs and Lake Pupuke. In 1965, Smith broadened his liberations to include tench which he obtained from a contact in Waimate. He started with four, which was enough to establish a breeding stock at what he called his "office pond", behind his garage.

As his operation ramped up, Smith started breeding goldfish (a type of carp, not the type commonly kept as a pet), koi carp, gambusia, and golden orfe.

But it was another fish that became Smith's signature - Rudd. Rudd are a stocky freshwater fish with coarse skin and ruby-red fins; They are prolific breeders, releasing thousands of eggs at a time.

They primarily eat aquatic plants, preferring natives over exotics, meaning they share a diet with native freshwater species. For that reason, rudd are sometimes called 'the possums of waterways'. There had been no rudd in the Southern Hemisphere until Smith liberated them into a pond at Wainui school, north of Auckland, in 1969.

Over the course of 20 years, Smith released more than 10,000 rudd, 2300 tench, 1000 perch, and hundreds of koi, goldfish, and orfe.

He had his favourite spots; Among them was Waikato's Waihou River, where he once released 2000 rudd in one go at the Te Aroha boat ramp.

PETER DRURY Waikato's Waihou River was a favourite spot of Smith's.

Although he typically avoided major waterways, likely because it increased the odds he would be seen, he still managed to populate them with fish. One strategy was to liberate fish into a nearby drain or stream, which, upon the next flood, would sweep fish into the river.

Smith was so prolific it became difficult to keep track of where the fish were ending up.

"He was always moving around," says one former Smith associate.

"He would say I've done this, I've done that, places all around the country... He even told me he put a whole lot of stuff in the South Island, that he'd moved koi carp to a particular lake on the West Coast. You don't know whether it's true or if he was making it up."

Authorities noticed the sudden appearance of rudd, a species never before seen in New Zealand. They knew who was responsible - Smith regularly bragged about his liberations. He was even profiled in the Auckland Star, under the headline 'Rudd doing well – now for gudgeon', complete with a photo of Smith.

Not long afterwards, in 1974, Smith was prosecuted for the first time. His fish were destroyed, his tanks were poisoned, and his car was confiscated, a setback which stopped his liberations for four years.

"Fascism is a long way from dead," he bitterly wrote in his diary.

That period, however, came with vindication. In 1975, rudd was declared acclimatised in Auckland and Waikato, essentially recognising that it was here to stay. To this day, Auckland/Waikato is the only region where rudd is established to the extent it is not considered "noxious", a feat entirely due to Smith.

KATHRYN GEORGE/STUFF Stewart Smith with two friends being caught by a farmer on a tractor while releasing fish into a waterway.

Smith's fish continued to spread, even though his liberations had paused.

When he started up again, he realised his fish had been too prosperous. He decided to start releasing perch again, under the logic they would predate on rudd and tench.

It was at this point he started falling afoul of his few allies. Not only had he returned to spreading perch, he was also releasing koi carp, a bottom feeder notorious for damaging waterways. He was talking about importing gudgeon, and even flirted with bringing in pike, a ferocious carnivore likely to dominate any freshwater body it could find.

Smith's notes end in 1988, when he was prosecuted once again, this time by the Auckland Acclimatisation Society. His fish were destroyed, and his equipment and notes were seized; He was fined $4950, and his beloved Lada Niva was confiscated.

Although he had stopped taking notes, there were numerous sightings of Smith around rivers and lakes in the early 2000s. He was hard to miss: He was an octogenarian, roaring about the countryside in his new, $40,000 off road vehicle.

A 2003 report produced internally for the Department of Conservation and seen by Stuff notes several of these sightings. The report was ostensibly about threats to Auckland's freshwater ecosystems; a major one of those threats, it concluded, was Stewart Smith, who was referenced by name dozens of times.

BRYNDLEFLY/CREATIVE COMMONS Lake Rototoa, Auckland's largest lake, was transformed by Stewart Smith's liberations.

There's a pristine lake near the Kaipara Harbour, at the northern edges of the Auckland Region, called Lake Rototoa.

It is one of a group of dune lakes, dotting the western coastline. Rototoa is the best of them; it is the largest, deepest lake in Auckland, and for a while, the only one dominated by native fish. Among its population were dwarf inanaga and dune lake galaxias, both of which are highly rare and on the brink of extinction.

Then Smith started his liberations.

In 1970, his notes show, he liberated more than 100 rudd into Rototoa. They prospered. So much so that, 30 years later, Smith returned with perch, in an effort to control the rudd he had unleashed.

It proved to be a near fatal blow for the lake.

Rudd, which feed on native macrophytes, reduced the lake's water quality. Then the perch started dominating the native species. Between 2003 and 2011, monitoring showed dwarf inanga numbers had dropped by more than 99 per cent, and the species is now functionally extinct in the lake. Kōura numbers had dropped by 90 per cent, and common bullies by 80 per cent.

The lake had also been a popular rainbow trout fishery, but almost immediately after perch were introduced, the fishery collapsed.

It's a common story when exotic fish are introduced; just like rats and possums on land, they tend to dominate whatever ecosystem they end up in.

"Competition between native species is very balanced in an ecosystem," says Dr Cindy Baker, a freshwater fish scientist at NIWA.

"They tend to have different niches and it all works together well. Once you put these introduced fish in, you have more overlap in niches for certain species, and that's where you have more competition for food resources."

Introduced fish have a significant effect on New Zealand's freshwater biodiversity, Baker says, particularly in lakes, from which they are hard to remove.

SIMON MAUDE/STUFF Stewart Smith released hundreds of perch into Auckland waterways in the 1960s, including Lake Pupuke.

He was an old man, now, but Stewart Smith had a plan.

He could no longer roam the countryside, but he could still breed fish. Which is why he dreaded what the authorities would do when they looked inside his tanks: He knew they would find 600 gudgeon, a species never seen before in New Zealand, which he was planning to release in Lake Taupō as his final act.

Smith had talked about this plan for a long time. He first mentioned it off-handedly in a 1972 news article in the Auckland Star, then again in a 1988 news article. But it wasn't clear how serious he was. In the twilight of his life, he had wanted to breed enough gudgeon, approximately 10,000, to fill the lake.

"It would have been horrific," one of the former officials, who had knowledge of Smith's plans, said.

It's not entirely clear how Smith smuggled gudgeon into the country. An investigation concluded Smith had likely received them from an associate who had since died. Due to a lack of evidence he had imported them himself, Smith was not prosecuted.

An internal biosecurity report said gudgeon "were considered likely to become widespread throughout New Zealand in all lowland freshwater systems, and were ranked as having potentially high impacts on both native and introduced fish species that inhabit these environments".

Over the course of 20 years, Smith released more than 1000 perch.

The day after the raid, gudgeon was declared a pest species, allowing them to be destroyed. Smith's tanks were cleansed, leaving him with nothing.

Gudgeon were also found in a pond near Helensville, and exterminated there, too. Smith had told one associate he released gudgeon in potentially dozens of other waterways, including the Hikutaia Cut, which would have been devastating; it is connected to the Waihou River, which, as the biosecurity report said, "would mean the feasibility of eradication from these waterways is extremely low".

A sweep of those waterways found no sign of gudgeon, although no extensive search was undertaken in the Hikutaia Cut or the Waihou. To this day, it is unclear if gudgeon were ever released.

Following Smith's death in 2008, authorities returned to his lair to destroy whatever he had left in his tanks. They were let in by Smith's nephew, his closest relative, who was not in any sense close to his uncle.

They expected to find more gudgeon, but didn't; just a few schools of rudd. Nevertheless, the tanks were drenched with a lime solution to destroy any trace of life, and a sucker truck dealt with the contaminated water, ending the complicated legacy of Stewart Smith.

"Like us all, I think he was an inconsistent personality," Bryan Winters says.

"He enjoyed fishing, and genuinely felt that spreading these fish around was going to benefit people. I don't think he approached it like some evil ogre, thinking 'I'm going to do harm to New Zealand by doing this'."

In his writing, Smith often talked about the joy of fishing, particularly for children. He believed New Zealand was deficient in this sense - apart from eels, which he believed were too scary and snakelike for kids, there was no way for a child to grow up fishing in the way he did.

Curiously, Smith himself was not a regular angler, even though an entire coarse fishing subculture had emerged in his wake.

"He came to some of our meetings - he was very well-read and he didn't suffer fools gladly," said John Jossevel, a founding member of the West Auckland coarse fishing club, which began in the early 1980s.

"He didn't do a lot of fishing himself, for enjoyment or pleasure."

Smith is still advancing his cause beyond the grave. Every couple of years, several coarse fishing clubs receive a $5000 donation from the 'S Smith Trust', financial documents show. Last year, the West Auckland club received $10,000. It pays for trophies and catering and stationery and other things that keep the club going.

KATHRYN GEORGE/STUFF Stewart Smith fished in London canals as a child.

Stewart Smith is a boy, roaming the streets of East London with his fishing rod.

He often fishes alone, in the Lea canal, while the other boys play rugby after school. He sometimes finds little ponds, where he fishes for perch, pike, and best of all, gudgeon; When he hooks a gudgeon, he sells it to other fishermen to use as bait.

He loved his parents, even when money issues ruined things. His father was a gambler, he wrote, and once loudly abused his mother while Smith listened in the next room.

But there was always fishing: "My childhood in England was happy, largely due to those hours spent fishing," he later wrote.

Smith was only 15 when his father told the boy that he and his brother would be going to New Zealand, alone. His coarse fishing days, and his childhood, was over. But it didn't have to be for the next generation.

"He said to me once, the greatest pleasure a boy can have is fishing," one person who knew Smith said.

"He was always yearning for that boyhood pleasure he had fishing in the canals as a boy. He wanted to replicate that here."