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Goldfish Can Now Survive Saltwater, Which Is Very, Very Bad

One of the most insidious threats to underwater ecosystems is here, and it isn't a scary shark or dangerous jelly. It's a goldfish that can survive in saltwater.

One of the most insidious threats to underwater ecosystems is back with a new weapon that makes it more dangerous than ever. No, it's not a shark with an extra layer of teeth, or even a jellyfish with a super-charged toxin. It's — you guessed it — a goldfish that may be able to live in saltwater.

OK, you probably didn't guess it, and this also may sound really mundane, but we promise this is dangerous and you should care about it.

Here's why: Goldfish are one of the world's most prevalent invasive species, partly because people keep releasing them when they get too big for their aquariums.

And goldfish, which are basically carp, can survive just fine out in the real world of rivers and lakes.

Then they eat a lot and grow into giant goldfish that go viral in photos like this.

And this.

Goldfish in home aquariums generally live in water with a salinity of zero, which is tap water, according to Mashable. The ocean has a salinity of 35, which feels like far too salty for a goldfish who's only ever known freshwater to ever live in. But boy, do goldfish have some tricks up their sleeve — or at least they would if they had sleeves.

Some goldfish released into freshwater rivers in Australia have made their way into estuaries, which are bodies of water between rivers and the ocean. It's kind of like the meeting point between salt and freshwater, and scientists call it a saltbridge.

Because if goldfish can survive swimming in these salty waters, they can make the swim from one river to another river.

That means they could eventually take over the entire American freshwater river system, killing off all native fish and colonizing lakes and ponds as we know it.

Sounds drastic, right? It's not a far-off possibility. So if you find yourself, either in Australia or literally anywhere else in the world, with a goldfish you don't want, don't flush it down the toilet or release it in a local river.

Return it to a local pet shop or, if worst comes to worst, euthanize it by putting it in the freezer. You might just help save the fate of freshwater systems as we know it.

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