Release the “Super Males”: Female Invasive Trout Wiped Out in World-First US Eradication

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The story

A research team at the Idaho Department of Fish and Game (IDFG) in the US kept releasing “super males” (YY males, which can only father sons) into two rivers infested with invasive brook trout — and after six years, females had vanished completely. With no poison and no nets, this is being called the world’s first case of eradicating an invasive fish purely by manipulating its genetic sex ratio. On 5ch’s science news board, the result drew plenty of surprise, along with calls to try the same trick on Japan’s own invasive species like largemouth bass, and questions about whether it could ever be applied to the human Y chromosome.

Six years after the “super male” releases began, females have been wiped out entirely — a world-first success in eliminating an invasive trout

Research from Idaho’s Department of Fish and Game (IDFG) and others has confirmed that female invasive brook trout have completely disappeared from two rivers where “super males” (YY males, which only sire male offspring) were continually released.

Fish released to boost numbers ended up wiping out the very fish they targeted.

Source: nazology.kusuguru.co.jp / Original article here

What people said

3AnonymousSep 2, 2026 22:44
This probably wouldn't work on crayfish.
4AnonymousSep 2, 2026 22:45
Re: #3
What about humans, though?
6AnonymousSep 2, 2026 22:52
Do it to the bears too, please.
8AnonymousSep 2, 2026 22:55
Did they release tiger trout or something?
9AnonymousSep 2, 2026 22:57
>Of course, this success story only applies to a small stream that outside fish can't get into.

Hmm…
10AnonymousSep 2, 2026 22:59
Professor Yoko Tajima! These are the guys you've been looking for!! (a Japanese feminist TV commentator often invoked in jokes as the poster child of "anti-male")
11AnonymousSep 2, 2026 23:05
I'd love to see this tried on largemouth bass and bluegill, but with bass anglers and tackle shops constantly restocking them themselves, it'll never fly in Japan.
12AnonymousSep 2, 2026 23:16
Hurry up with the pollen-free cedar trees already (a jab at Japan's notorious cedar-pollen allergy epidemic).
13AnonymousSep 3, 2026 01:13
So basically the trout ended up as nothing but males and super-males before dying out, huh. That's a grim way to go extinct.
14AnonymousSep 3, 2026 01:25
'Sup, fellas! 'Sup!
15AnonymousSep 3, 2026 01:33
Everyone but me is the opposite sex!!! (a parody of the old saying "everyone but me is my teacher")
17AnonymousSep 3, 2026 02:02
Well, color me stunned…
18AnonymousSep 3, 2026 02:02
A world with absolutely nothing but males, no matter where you looked, must've been hell.
21AnonymousSep 3, 2026 04:04
Re: #18
It's a world with nothing but "Aniki" and "Super Aniki" (macho-meme slang for hyper-manly, admirable dudes).
No distortion there at all (a catchphrase from that same meme, meaning something's the real deal).
19AnonymousSep 3, 2026 02:18
I see, so this is a different approach from the sterile insect technique used on screwworm flies.
By the way, in humans a YY chromosome combo is lethal, so the same trick won't work (the X chromosome carries a lot of genes essential to staying alive).
20AnonymousSep 3, 2026 03:58
It says they can interbreed, so this would wipe out native species too, wouldn't it?
22AnonymousSep 3, 2026 06:20
In human terms, it's like releasing a ton of cute "otokonoko" (feminine-presenting boys), huh?
24AnonymousSep 3, 2026 06:43
Nothing but males being born…
Haplogroups. (a nod to Y-chromosome lineage tracking)
37AnonymousSep 3, 2026 07:58
Pretty useful technique.
Seems like it could be repurposed for all kinds of other things too.
39AnonymousSep 3, 2026 08:04
Re: #37
This was actually done before with destructive fly species.
They discovered that zapping male flies with radiation could sterilize them, and periodically releasing those irradiated flies knocked down the fly population over time.
38AnonymousSep 3, 2026 07:59
The "women are the problem" crowd on 5ch (a derisive nickname for chronic anti-women posters) is basically dreaming of a world with nothing but super-males and males, after all.
Something like technology that lets men give birth to sons only.

Background and key points of the discussion

The technique exploits the fact that any male carrying a Y chromosome can only father sons; by continually releasing YY males, the female share of the population shrinks generation after generation until it hits zero. What makes it novel is that it wipes out the invasive species without herbicides or poison, hitting only the target fish. That said, as commenters in the thread noted, this success story was limited to a small, isolated stream that outside fish can’t swim into — it’s easy to mistakenly read this as a method ready to use in connected river systems, but it isn’t. A similar concept was previously used against flies via the sterile insect technique (irradiating males to destroy their fertility), so the YY-male method can be seen as a fish version of that same idea. Some posters asked whether the approach could work on humans, but since a Y chromosome alone lacks the X-chromosome genes required to sustain life, no individual could actually develop that way, so the method doesn’t carry over. Others hoped to see it applied to Japan’s own invasive species like largemouth bass, but pointed out that as long as anglers keep restocking them in the wild, putting it into practice would be tough — suggesting the real obstacle isn’t the science itself but how it would actually be carried out.

*This article excerpts and summarizes the 5ch (Science News+) thread “[Nazology] Six years after “super male” (YY male) releases began, females have been eradicated — world-first success in eliminating invasive trout, US“.

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