On the topic of fish

Department of Conservation —  03/10/2019
Estuarine triplefin . 📷: Vincent Zintzen

It’s DOC’s job to care for nature

And nature covers a lot. Fish, birds, reptiles, bats, marine mammals and invertebrates; plus 8.7 million hectares of land.

If you’re a numbers-type person, you might be interested to know this land includes three World Heritage Sites, 13 National Parks, 44 Marine Reserves, 326 campsites, 967 huts, and 13,429 km of tracks. In total, it’s 30% of the country.

If you’re not a numbers-y person, let’s just say we do a lot.

Everyone is talking about ….

In the past few years, there has been a spike in the public’s interest in one of the predator control tools we use to protect our most vulnerable native species.

[Edit 08/10: New Zealand was] using biodegradable 1080 in the 1960s. And since then, we’ve been researching it, improving methods of application, communicating about our use and monitoring the effects.

We also get harassed about it. A lot.

We get things like this:

For achieving things like:

Of the hundreds of thousands of private messages or comments we get, about 40% of them have to be hidden because they’re explicit or threatening (we have firm rules for what we do and don’t hide; we don’t hide things just because they’re not positive).

Some of these comments we report to the police because they threaten the safety of our staff, our contractors, and their families. They’re really horrible, graphic threats, but this post isn’t about that.

This post is about fish

Among the messages of harassment and/or spam, there are people who are earnestly worried about 1080.

Their reasons vary, (and the majority of them we’ve addressed or otherwise corrected), but we haven’t spoken enough about fish. Specifically, trout.

Rainbow Trout. 📷 DOC

1080 operations have no effect on trout, nymphs and native fish, or the water in the streams, rivers and lakes where they live.

Research in laboratories and in natural waterways has tested the effect of artificially high doses of 1080 on trout and the environment. No effects on trout or the ecology of the test area were found. The research also demonstrated that trout were safe to eat after a 1080 operation (more on this later).

Essentially, fish aren’t nearly as at-risk of ingesting 1080 as the fear mongering posts on social media could lead someone to believe.

The key to understanding this is a two-parter:

☝️ The bait pellets are not one hundred percent 1080
✌️ Trout don’t like bait pellets anyway

Bait breakdown

Contrary to opinion, the green pellet things you see in the news are not large chunks of 1080. They’re cereal bait pellets:

📷: DOC

They’re a mix of cereal, sugar and dye designed to entice predators to eat them (and to deter non-target species).

These pellets themselves are not 1080 – but most of them do contain a little bit of 1080. 0.15%, in fact.

This is a critical point: while these pellets are not 1080, they’re the edible house that the 1080 lives in.

And just like houses, sometimes you’re home and sometimes you’re not. 

If a cereal bait pellet doesn’t have any 1080 in it, it could be for one of two reasons. Firstly, it could be because it was a pre-feed pellet to get predators used to the idea of this type of bait (these can be brown or white).

Secondly, it could be because the 1080 that was once in the pellet has leached out and biodegraded, which it is designed to do if uneaten. More on this soon.

Fish don’t like 1080 baits

Trout don’t like the cereal-based pellets because they’re designed to appeal to animals with quite different tastes. Rats and possums are drawn to them because they deliberately taste like plant or cereal grains, and seeds like wheat.

Trout have a different diet – they eat other fish, insects and nymphs not cereals. And occasionally mice, but we’ll get to that.  Trout also swallow their food whole and would be unlikely to be able to swallow a fresh, hard 1080 bait.

There’s no evidence, anecdotal or otherwise, of a 1080 pellet ever being found in trout guts. But even if (if!) a trout did eat a bait pellet, studies show it wouldn’t harm them.

Mice are one of the rodents affected by 1080 and anglers expressed concern that eating poisoned mice might be very bad for trout. To check this, we commissioned the Cawthron Institute to carry out a risk assessment.

In their 2014 laboratory study, the effect of trout eating a large number of poisoned mice was simulated by dosing them with the toxin at levels many times higher than would occur in the wild.

No fish died and no changes in their behaviour were observed during the research. This study demonstrated that trout are resistant to the 1080 toxin, probably because they have a different metabolism.

If you’re curious, set some time aside and dig into the research on this, it’s fascinating stuff.

The Ministry for Primary Industries (MPI) is responsible for food safety in New Zealand. In 2016, we asked them to update their risk assessment for trout eating a 1080 pellet directly, rather than from poisoned mice. MPI found the possibility of a small food safety risk but noted that it was highly unlikely to occur in trout in the wild, because trout are unlikely to swallow a bait and because 1080 washes out of baits pellets quickly.

But as a precaution, MPI advises anglers to avoid eating trout from waterways in a 1080 operation area within 7 days of the bait being dropped. You can read more about food safety on MPI’s website and we also list our operations online.

But what about the water?

1080 is a natural compound that’s found in several species of plants – it’s their defence to stop animals eating them. Because it’s a natural compound, it breaks down rapidly in the environment.

If a pellet containing 1080 enters a stream or soil, the 1080 exits the bait pellet and very quickly dilutes to harmless levels, particularly in flowing water.

While the cereal pellet might linger, the 1080 doesn’t. This is because 1080 is water soluble and there’s only a small amount per pellet.

Microorganisms and plants then break the 1080 down into other harmless compounds very rapidly.

📷: DOC

The fact that 1080 degrades quickly is one of the reasons it’s used for landscape scale predator control in New Zealand.

Unfortunately, people who don’t know this (or don’t get it) are worried about trout. While the conclusions they arrive at are incorrect, it’s possible to see how they got there.

We’re back to social media

Social media is a breeding ground for misinformation. Inaccuracy takes the form of emotive posts and unverified ‘proof’, which thrives in echo chambers as algorithms deliver you stuff you want to see, reinforcing your beliefs.

It’s been researched, and there’s no scientific evidence that 1080 operations affect trout.

At the end of the day, 1080 isn’t perfect, but it does protect native species by efficiently controlling predator numbers.

When it’s used carefully by licensed operators, and the public are educated about the facts and follow expert advice (like keeping dogs out of treated areas, following MPI’s fishing instructions, and adhering to signage), it’s low risk.

We’re doing our part by carefully managing the application and use of 1080, but we need all members of the public to keep their end up too.

We also need people to check their sources and verify what they see online. It’s important to look for legit sources — not strangers on the internet with unverifiable empirical evidence, propaganda, or experts from unrelated fields.

You can help by sharing this blog, and by trying your best to correct any 1080 misinformation within your communities.

Circulating science is the way to go.

12 responses to On the topic of fish


    Very sad that the Doc feels the need to publish this. So many inaccuracies and half truths presented as facts. The Doc has not been using 1080 since the 1960s, it wasn’t in existence then. So that’s a lie right there.
    I worked for the Forest Service and was involved in 1080 operations in the 70s. I then transferred to Doc in 1987 and 1080 use by the Doc was virtually non-existent. Now it’s a department claiming links back to the 60s with 1080 use.
    When you use poison randomly thrown from aerial death machines you are communicating with nature in the cruelest way possible so don’t be cry baby about it. Man-up to what you are doing. Fly the skull and cross bones from your highest flag pole. Be proud to use such a horrible weapon of mass destruction.
    Go out sometime and watch an animal die from it, as I have. Sit there contemplating that one single death in the millions that you cause and wonder: is it worth getting paid to support one of the world’s deadliest poisons?
    For most people with any empathy and compassion the answer is simply:it isn’t.
    The rhetoric of 1080 and Pests has long since taken over from any rational thinking.
    I am sad for NZ. Sad for Doc that its arrived at such a terrible place. The whole of NZ is going to experience the horror of 1080 before pfnz 2050 finds out how wrong it is.


      Hi Andy – within the context of that sentence, the ‘we’ was New Zealand. However we’ve clarified this now to avoid any other possible confusion; you’ll see that edit there now, dated and identified. DOC was formed on 1 April 1987 and staff were drawn from agencies including the New Zealand Forest Service; which was using aerial 1080 in the 1960s. DOC’s passion and determination to save our precious native species, which are at serious threat of extinction due to predators, has not waned over the years and our knowledge has grown. You can read more about DOC’s use of 1080 and the native species growth achieved through this use on our website.


        Changes nothing really. Playing with the wording doesn’t change the fact: Using poison to communicate with Nature demonstrates a huge lack of understanding and incredible ignorance. There is actually no deep philosophical and absolutely no moral justification for its use.
        The jargon, propaganda and the slogans, “save our precious native species”, adinfinitum, have replaced any pretext of honest enquiry into what is actually being done to NZ.
        And the nightmare that is to come.
        The closer you get to Nature the less likely you are to want to do any harm. To any living thing. All life is precious because all life is one life. Even science says that.
        Just keep in mind.
        “Nature always bats last.”

        Alan Rennie 24/10/2019 at 3:27 pm

        Muppet DOC stop the lies,From Landcare scientist Charles Eason, “1080 is not safe. I have never and will never say that.” 1080 is classed as a “super poison” by the US EPA.
        And on the issue of 1080 being naturally-occurring, plants produce fluoroacetic acid, but manufactured 1080 is sodium monofluoroacetate. Mr Eason stated in April 2002 that “Anyone comparing 1080 poison with the naturally-occurring substance is stupid.” When water is added to sodium monofluoroacetate it “dissolves” but does not lose its integrity. It is diluted as the molecules are spread out in water, but the molecules remain as sodium monofluoroacetate molecules.


        Very funny Doc ,do some research instead of making little stories which mean nothing ,research will show just exactly what you are playing God with ,long term effects are going to destroy what we have now ,.1080 poison is making money for thousands of losers ,and its certainly not about helping our wildlife ,the sooner we change Government’s and ban this shit like every other country the better,but just maybe because of the team of morons running and employing the mentally challenged,you lot have already lit the fuse ,for which we may not be able to put out


    Your post is so shot full of misinformation that it’s hard to know where to begin.

    So I’ll start with this; 1080 isn’t poisonous.

    It isn’t. Eat a big spoonful of sodium monofluoroacetate, and the fluoroacetate won’t kill you.

    What will kill you, however, is fluorocitrate – which is the first metabolite of fluoroacetate, produced in the gut of air-breathing organisms.

    That is how fluoroacetate works as a poison. And it affects all living organisms that breathe air.

    Compound 1080 was first registered as an insecticide, and then as a rodenticide. It remains very effective in both roles.

    Fish, however, do not metabolise fluoroacetate in the same way as do birds, mammals, insects, and other things that breathe air. They do not produce fluorocitrate as a metabolite at anything within a couple of orders of magnitude of the rate that air-breathing creatures do.

    The problem is not with trout eating 1080 poison baits. It never was. The problem is with trout eating mice that have eaten 1080 baits. And the Cawthron Institute DID NOT test this parameter – even after I pulled Maggie Barry up about it in Parliament.

    They fed trout directly with 1080 baits. They did not feed them mice (or any other air breathing creature) that had eaten 1080 baits.

    And a mouse can eat about 10 times the amount of 1080 that a rat can, before succumbing to the poison. That’s 10 times the amount of 1080, not 10 times per unit of bodyweight, BTW.

    So a trout that’s full of poisoned mice contains one hell of a lot of metabolised fluorocitrate, and eating that trout will kill you.

    You’re all Doctors commenting here, or scientists, or both. We can safely presume that, from your clear knowledge. And I respect your training and your understanding of biochemistry.

    So I can only presume that you weren’t aware that Cawthron very deliberately didn’t test for the one thing that they should have been looking for.

    I imagine you will now want to investigate this particular factor in further detail.


    Excellent commentary and very well presented. I will differ on your claim that trout “…would be unlikely to be able to swallow a fresh, hard 1080 bait.” I probably know a little bit about this. But that doesn’t change your conclusion that “…even if (if!) a trout did eat a bait pellet, studies show it wouldn’t harm them.”

    Martin Nicholls 03/10/2019 at 6:10 pm

    This is a well-reasoned and well expressed commentary on 1080 by DOC. There is also the point to be made that 1080 (sodium fluoroacetate) is a derivative of an entirely natural product that breaks down to CO2 and fluoride salts.

    However, whatever we say, the opinions of those opposed to 1080 will never be swayed. They come from the issue of animal rights and cruelty or from vested interest perspectives, such as those wanting to trap possums or shoot game. For these opponents to give up their belief system would mean either having to admit they are wrong or having to give up their cherished pursuits that take them into the DOC estate. People might’ve entered the Cats to Go website started by Gareth Morgan. Cat lovers were shrill and threatening when their cherished assertions were challenged. They weren’t swayed at all, even by the most reasoned of arguments.

    For me, believe me when I tell you I hate killing things too, even the 122 rats I trapped in two days in Bushy Park before it was fenced. Sometimes the FENN traps I used failed to kill the rat outright and the poor thing suffered in terror knowing I was about to kill it. To try to overcome the profound sense of sorrow I felt I had to chant a mantra: “four more robins, four more robins” in deference to the number of robins expected to be saved from predation by removing these rats.

    I don’t think there is a soul in the predator control field (one who isn’t a psychopath) who takes any delight in killing things but what gives us a real buzz is seeing the increase in native animal numbers over the season as a measure of success. We can also empathise with those native, especially endemic, species (that belong here and nowhere else in the world) that are no longer being persecuted by relentless predation by rats, stoats and cats. I remember the video from Sarah Cross on Country Calendar where the camera had captured and recorded to killing of two defenseless falcon chicks by a feral cat. The mother looked on helpless.

    Imagine what a campaign against feral cats might’ve achieved, maybe from secondary poisoning from 1080. We can also think of all those young kiwi that could survive to adulthood free from facing certain death from these furry killers. And we can think of a time when otherwise rare and threatened native species can be seen in our own gardens with kiwi wandering from backyard to backyard, while kokako, tieke and robin delight us with their morning song. Currently this is not possible, but may become a routine experience in the future if only we can come to embrace those technologies that inevitably mean the deaths of those introduced species that threaten their existence.

    Hats off to DOC for their efforts and I hope they come to be appreciated in our communities for what they are doing for our native species (including our aquatic ones) rather than being vilified and threatened for their war against those putting them at risk. 1080 will be here to stay until something better comes along, and this may be more urgent than we think because of the explosion in dama and Bennett’s wallaby numbers throughout the country, some probably deliberately released by those seeking to hunt them in their areas, and probably the same group of people who so hate 1080. “There are none so queer as folk”.

      Joylene Steicke 03/10/2019 at 8:33 pm

      Yes Martin, I do know where you are coming from, I was a trapper for DOC for 10 years in the 90’s, in a yellow-eyed penguin colony and hour north of Dunedin, so I am not against culling of introduced predators, but I still cannot come to terms with the use of 1080 as I have seen them dying from it. Not pretty. Lost count of the ferrets, stoats, cats and weasels that I caught over the years. Also not a pretty site, but not quite so bad, used Tims and cage traps which worked really well. Over those years we never lost a penguin in the reserve I trapped in.

    Joylene Steicke 03/10/2019 at 2:56 pm

    I know introduced species have to be controlled but the problem my family has with 1080 is the time and way the animal has to die. Also non-target species eating the bates or the poisoned species.

      Stephen Hurley 03/10/2019 at 10:32 pm

      Just think about the estimated 26 million birds eaten alive every year by pests and you will feel better.


    Clear explanation, science backed. Well done.