On the topic of fish

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.

We started 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.

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:

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.

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.