Why Swedish scientists gave salmon cocaine

Summary

Podcast Summary: "Why Swedish Scientists Gave Salmon Cocaine"

Podcast: Short Wave (NPR)
Hosts: Regina Barber
Guest: Jack Brand (Aquatic Ecologist, Swedish University of Agricultural Sciences)
Date: May 12, 2026
Duration: ~11 minutes (excluding ads)

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Episode Overview

This episode digs into a fascinating and slightly wild scientific study: Swedish researchers exposed salmon to cocaine to explore how trace amounts of neuroactive drugs—now commonly found in aquatic environments—impact fish behavior. Guest Jack Brand joins host Regina Barber to explain the study’s surprising findings, the broader implications for aquatic ecosystems, and what this reveals about our environmental footprint.

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Key Discussion Points and Insights

1. Why Study Drugs in Fish?

• Environmentally, prescription and recreational drugs like anti-anxiety medications and cocaine end up in our waterways when excreted and pass through water treatment plants ill-equipped to filter them out.
• Past studies show human drugs can alter fish behavior, impeding survival (e.g., anti-anxiety drugs make fish too “relaxed”).

Quote:

"Fish become, as you'd expect on anti-anxiety drugs, sort of more relaxed, and that's not very good for a small fish."
— Jack Brand [01:20]

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2. Study Design: Dosing Fish with Cocaine

• Purpose: To see how both cocaine and its main human metabolite (breakdown product) affect fish in real-world, trace-level exposures.
• Method:
  • Used 105 genetically similar, same-aged hatchery salmon, split into three groups:
    1. Cocaine implant
    2. Cocaine metabolite implant
    3. Control (no drug)
  • Fish were sedated, received a tiny surgical implant slowly releasing the substance, plus an acoustic tracking tag.
  • Placed in a lake with hydrophones (underwater microphones) to track movement.

Quote:

"We make a small little incision on the underside of the fish and slowly inject the implant. Then we also implanted an acoustic tracker... so we know where a fish was and when."
— Jack Brand [04:01]

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3. Why Track the Metabolite?

• Both cocaine and its metabolite enter the environment, but most environmental monitoring focuses on the drug itself.
• The metabolite, often more abundant in water than cocaine, is considered inert in mammals—but its effects on fish were unknown.

Quote:

"One of the interesting parts of our study was we found that the metabolite actually had a greater effect on fish behavior than cocaine, which was not something that we expected."
— Jack Brand [05:54]

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4. What Did the Scientists Find?

• Salmon exposed to cocaine and its metabolite swam twice as far compared to controls by the study's end.
• This heightened movement means much higher energy use.
• Future questions: Are they eating more to make up for it or simply weakening over time? There could be complicated impacts on predator-prey relationships and food webs.

Quote:

“They were moving around twice as far... This is a massive increase in energy expenditure... There has to be a tradeoff, which can also have effects for if they need to eat more, perhaps they're putting themselves more at risk to predators.”
— Jack Brand [07:38]

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5. The Wider Ecological and Evolutionary Implications

• Drug targets in humans are "evolutionarily conserved": similar brain receptors exist across much of the animal kingdom, making wildlife susceptible.
• The real environment contains complex mixtures of drugs, not single exposures.
• The presence of these “invisible agents” could be a significant, overlooked driver of ecological change.

Quote:

“I think of these chemicals as sort of this invisible agent of global change because people can’t really see them and so they don’t get the recognition that I think they deserve. And I think they're probably having far wider impacts on our wildlife than people are actually aware.”
— Jack Brand [08:37]

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6. What Can We Do About Aquatic Drug Pollution?

• Advanced wastewater treatment techniques—such as activated carbon filtration and ozonation—can remove many of these chemicals but are costly and not widely implemented, especially in low-income regions.
• More affordable, accessible treatment and collective effort are needed globally to mitigate this issue.

Quote:

"The main issue there is these things are often a little bit costly and so they're not evenly distributed around the world... It requires collective effort making them more affordable and accessible."
— Jack Brand [09:55]

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Notable Quotes & Memorable Moments

• "I think they're probably having far wider impacts on our wildlife than people are actually aware. And so I think it's really great to raise the issue of this in the public domain."
  — Jack Brand [09:29]
• "I hope you do get that salmon fishing trip one of these days."
  — Regina Barber, joking at the end [10:44]
• "No worries. Thanks for having me. It's been fun."
  — Jack Brand [10:53]

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Important Timestamps

• 00:17 – Introduction, inspiration from "Cocaine Bear"
• 01:20 – Effects of pharmaceuticals on fish behavior
• 03:54 – Start of in-depth interview with Jack Brand
• 04:01 – Study methodology explained
• 05:54 – Surprising effect of cocaine metabolite
• 07:38 – Explanation of findings on salmon movement
• 08:30 – Open questions and ecological complexity
• 09:55 – What can be done: technological and global solutions

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Episode Tone & Style

• Accessible and Curious: The hosts and guest keep the discussion light and engaging, even while diving into complex science.
• A Touch of Humor: References to "Cocaine Bear" and funny asides about salmon fishing.
• Urgent but Hopeful: Emphasizes the silent, wide-reaching impacts of human pharmaceutical use but also outlines actionable solutions.

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Conclusion

This episode offers a surprising, eye-opening look at how human activities leak into the wild in unexpected ways—literally. By showing that even breakdown products of drugs can change animal behavior, Brand’s research underscores the urgent need to rethink our environmental policies on pharmaceutical pollution and invest in better water treatment worldwide.

Whether you are a science enthusiast or just curious why salmon would be subjected to a "cocaine Christmas," this episode makes complex environmental science both understandable and compelling.

Transcript

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[Regina Barber]

You're listening to Short Wave from npr. Maybe you've heard of the movie Cocaine Bear, which came out in 2023. It features a black bear going on a murderous rampage after eating 75 pounds of cocaine.

[Jack Brand]

Oh my God, he's gonna die. It's like cocaine Christmas.

[Regina Barber]

And I couldn't help but think about it when I read a recent study

[Jack Brand]

asking whether sort of trace amounts of these really potent neuroactive drugs that are in our environment can actually affect the movement and behavior of fish in the wild.

[Regina Barber]

That's Jack Brand, an aquatic ecologist at the Swedish University of Agricultural Sciences. And to answer that question, Jack and his team gave a bunch of salmon cocaine for science. Now researchers know that prescription drugs pollute aquatic environments when people use the bathroom. Past studies have shown even anti anxiety drugs can change how fish act.

[Jack Brand]

Fish become, as you'd expect on anti anxiety drugs, sort of more relaxed and that's not very good for a small fish.

[Regina Barber]

A chill pill is not ideal when you have a lot of predators to worry about. Beyond that, drugs people use can change how fish forage, how they mate and reproduce. And Jack says these drugs are everywhere. But scientists are just starting to understand the consequences for wildlife.

[Jack Brand]

It's definitely present in sort of most ecosystems on earth now, unfortunately, these sorts of issues of chemical pollution and pharmaceutical pollution, but we're only sort of really starting to scratch the surface into understanding the potential consequences of that.

[Regina Barber]

Today on the show Cocaine Salmon what happens when researchers get salmon high for science and why? One scientist hopes that will change how we treat water for the better. I'm Regina Barber and you're listening to Shortwave, the science podcast from npr.

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[Regina Barber]

okay, Jack, we're talking about your, like, recent study where you expose salmon to cocaine first. Can you explain how you did that?

[Jack Brand]

So basically what we did is we wanted to get fish of all the same age, genetic background, life history, and so that we could be sure that any changes in movement was caused by that drug administration, not some other confounding effect. What we did was we took 105 fish from a hatchery who were usually reared to be stocked into the lake, and we divided them up into three groups. One group received a slow release implant of containing cocaine. Another received a slow release implant containing its main metabolite, which basically is the breakdown product of cocaine in humans bodies, which then gets extracted, excreted into the wastewater. And one was a control group, so they received no drug. And to do that, we basically sedate the fish and perform a sort of minor surgery. We make a small little incision on the underside of the fish and slowly inject the implant. And then we also implanted an acoustic tracker. So this is just sort of a small little black pinging tag which emits a unique sound. And then in the lake we placed a number of underwater microphones or what are called hydrophones. And these can pick up, you know, when a fish passes by those microphones. So we know where a fish was and when.

[Regina Barber]

Oh, that's so cool. So you want to study both cocaine and this byproduct.

[Jack Brand]

So basically what happens when people take cocaine is that their bodies partly break it down into this byproduct. Not all the cocaine and this byproduct are absorbed into your body. And what happens is it ends up being excreted when people go to the toilet. And so you have both cocaine and this byproduct being excreted, and then this enters wastewater. And then subsequently, because our wastewater treatment plants aren't really designed to remove these substances, ends up in our aquatic environment.

[Regina Barber]

And you wanted to look at like, not just cocaine, but also this byproduct because they're both in there.

[Jack Brand]

That's Right. And often the byproduct, this metabolite is present at higher concentrations than cocaine itself. But largely in mammals, this chemical is thought to be more or less, you know, all this a little bit complicated, more or less biologically inert, so not very biologically active. And so we wanted to see whether that was also true in fish. But I think one of the interesting parts of our study was we found that the metabolite actually had a greater effect on fish behavior than cocaine, which was not something that we expected. And we think this is important because, you know, typically when people are doing environmental risk assessments for these types of compounds, they're mainly focusing on the parent compound. So that's cocaine itself.

[Regina Barber]

Right.

[Jack Brand]

And not really, you know, accounting for these byproducts. And so here we sort of showed that some of these byproducts may be having actually even greater effects than we originally thought.

[Regina Barber]

That's fascinating. Okay, and when you're talking to people, how do you explain why this work matters?

[Jack Brand]

The reason that we're often concerned about these chemicals is because they target receptors in people's brains that are also present in a wide variety of wildlife species. And so they're what we call evolutionarily conserved, meaning that the same biological systems that these drugs target endue are also present in fish and a wide variety of other vertebrates. And so that's what makes us particularly concerned about these sort of really potent neuroactive chemicals and how susceptible sort of the vertebrate tree of life may be to the effects of these chemicals on their nervous systems and their behavior.

[Regina Barber]

Okay, so you found salmon exposed to cocaine and this byproduct, this main metabolite, swam further than other salmon. Like what does swimming distance tell you about salmon behavior or their life?

[Jack Brand]

Yeah, so we basically found that they were moving around twice as far towards the end of the study. And basically, you know, this is a massive increase in energy expenditure. Animal behavior is fairly finely tuned, and to exert more energy, that energy has to come from somewhere. And so at this stage, we don't know if they're increasing their foraging behavior to compensate for this or if their condition just slowly deteriorates over time and they become in worse and worse health over time. We don't know. But definitely there has to be a trade off there. There has to be a trade off in the energy they're consuming as well, which can also then have flow on effects for if they need to eat more, perhaps they're putting themselves more at risk to predators because they're not hiding or they're moving into new areas, they're altering food webs and predator prey interactions and things like that.

[Regina Barber]

Now that you've done this experiment in salmon, what questions do you still want to answer?

[Jack Brand]

Many, many. So one of them that's, that interests me is we don't really know the mechanism that's driving this change. So we don't really understand what it is about this metabolite that's actually causing these increased movement rates in the wild and these fish. Another thing is, I'd like to understand, like I said, our study was only relatively short, a couple of months, but what the long term consequences of this are, we don't know. And of course ours is a pretty controlled situation. You know, we deliberately exposed a particular group of fish to a particular quantity of a chemical. But in reality what happens is there's sort of dilute cocktails of these drugs in the environment. There are many different types of chemicals that affect all different levels of the ecosystem. You know, predators, prey, et cetera. How that all interacts is very, very difficult to disentangle. And I think of these chemicals as sort of this invisible agent of global change is because people can't really see them and so they don't get the sort of recognition that I think they likely deserve. And I think they're probably having far wider impacts on our wildlife than people are actually aware. And so I think it's really great to sort of raise the issue of this in the public domain.

[Regina Barber]

What can be done? What can governments do, cities do to limit this?

[Jack Brand]

Yeah, there are advanced wastewater treatment techniques that can aid in this. So things like activated carbon filtration, ozonation, which sort of breaks down some of these chemicals. And so these can be implemented to remove a substantial portion of the chemicals being let out into the environment. The main issue there is these things are often a little bit costly and so they're not evenly distributed around the world. So you can imagine in places, especially low income countries, these things are often lacking or entirely absent. I see there are things we can do, but it requires sort of collective effort in treating this wastewater with these advanced treatment techniques and, you know, making them more affordable and accessible to countries around the world.

[Regina Barber]

Jack, thank you so much for bringing us. You know, your study about salmon and I hope you do get that salmon fishing trip one of these days.

[Jack Brand]

No worries. Thanks for having me. It's been fun.

[Regina Barber]

If you like this episode, please share it with a friend. And check out our episodes on what Chimpanzee Civil War tells us about humans and The Secret of Bees. This episode was produced by Rachel Carlson and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Jimmy Keeley was the audio engineer. I'm Regina Barber. Thank you for listening to Short Wave from npr. See you next time.

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