Ginormous goldfish are invading Australian rivers A man holds one of the giant goldfish. (Murdoch University/AP Photo/Martin Mejia)
Ginormous goldfish are invading Australian rivers
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There's nothing cuter than a goldfish. Diminutive, bright and distinctly cheerful-looking, they're a staple of fish tanks around the world. But Australian scientists are not so enamored with the little darlings, reports Johnny Lieu for Mashable. Not only are they invading Australian rivers, but they're also growing to gargantuan sizes.
 
The huge goldfish of Western Australia are anything but adorable. Over the last 15 years, Lieu reports, they've taken to freshwater rivers in ever-greater numbers along with a host of other aquarium fish.
 
In a new study published in the journal Ecology of Freshwater Fish, researchers reveal how the fish have spread throughout Australian waterways. The fish have grown ever larger as they go.
 
The fish are not just big, the study found, they're incredibly mobile. In just five days, they can travel an average of one mile in the river. One intrepid fish went a whopping 3.35 miles in a mere 24 hours.
 
Over a year-long period, researchers tracked the movements of goldfish in the lower Vasse River. The researchers used acoustic testing and tagging to determine what fish were doing. The goldfish studied didn't just swim around. They appear to have spawned in what ecologists call a "spawning migration," a pattern in which fish breed in areas far away from their normal hangouts.

That's bad news, Stephen Beatty, a senior research fellow at Murdoch University's Centre for Fish & Fisheries Research who led the study, tells Smithsonian.com.
 
"The fact that they're so big is really symptomatic of the other impacts in the river," says Beatty. The river, he explains, is warm and stagnant. Those are perfect conditions for pet goldfish who make their way into waterways after being released by their owners.
 
"The goldfish have really capitalized on that," he says. Not only do the goldfish disturb the habitat and potentially consume invertebrates and fish eggs, his team suspects that they are also disease vectors.
 
Carassius auratus originated in Asia and are kept as pets the world over. But when they're released into the wild, the well-behaved fish tank friend becomes a foe to other wildlife. Not only do they grow without the constraints of a tank and commercial fish food, but their feeding frenzy also causes mud and debris to rise from the bottom of the river. That fuels the growth of aquatic plants, which can degrade the river even further.
 
And while splashing around in the warm, nutrient-rich environment they love, they breed like crazy.
 
It's become an issue throughout the world. A Boulder, Colorado lake teems with the fish and in Alberta, Canada, the problem has become so bad that officials pleaded with the public not to release them.
 
For Beatty, all that press is a good thing: "They're a bit of a flagship because they do get that media attention," he concedes. But their star status has a downside - a misconception that if your goldfish is tiny, it won't hurt to drop it in a lake or river.
 
"Introduced species can have really unpredictable impacts, even cute and fuzzy ones," he says. "Please don't release anything into rivers or wetlands that are not native there."

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CRITICAL THINKING QUESTION
How do the goldfish interfere with the existing habitat?
Write your answers in the comments section below


COMMENTS (27)
  • chloeo1-bla
    9/16/2016 - 08:24 a.m.

    According to the article, goldfish are invading rivers everywhere. They are growing in size and population, they are "breeding like crazy" says Erin Blakemore. People are releasing their pet goldfish into the wild, even the smallest ones, and it's backfiring. The smallest goldfish are eventually turning into the big fish that's invading mostly Australian waters. Some of the goldfish are going 1 mile in 5 days, and one goldfish went 3.35 miles in about 24 hours! I think this over population is getting out of control and it is good scientists are studying it and telling people to stop releasing their goldfish into the wild. These goldfish could get bigger.

  • lydiao-bla
    9/16/2016 - 09:37 a.m.

    Gold fish interfere with the existing habitat by causing disease to other animals fro example like bears. Bears eat fish, what if the fish was one of the that got disease from animals and that mean the bear would get disease from the fish the bear ate. But now the bear got disease. Another example is that what if the bear was a mama bear and it had babies so that means the babies have the disease also if the mama bear ate the disease fish. "Introduced species can have really unpredictable impacts, even cute and fuzzy ones," he says. "Please don't release anything into rivers or wetlands that are not native there." Like what the narrator said, it very hard to tell with species have disease and which don't.

  • mthor-wim5
    9/16/2016 - 01:15 p.m.

    I think the goldfish interfere with the existing habitat by breeding so much that they take up room in the fresh water lakes and rivers. People might want to swim there, but get scared because of the big goldfish, and the goldfish taking up so much room with their size and population. They also stir up the sand, dirt, and mud at the bottom of the lakes and rivers, which fuels the growth of the aquatic plants, degrading the lakes and rivers even more! Including the feeding problem, they eat eggs of other fish and aquatic animals, decreasing their population.

  • genm-pav
    9/20/2016 - 10:02 a.m.

    This could create very big population issues, but they could also help feed more animals.

  • smatthew-dav
    9/20/2016 - 04:21 p.m.

    In response to "Gigantic Goldfish Invading Australian rivers," I agree that It could be good for the environment. One reason I agree is that more animals such as bears, have a larger food supply at their disposal. Another reason is that the fish are finding a new habitat. It says in the article that they are in many rivers. A third reason is that they can adapt to the new waters that they are inhabiting. The fish could be good for the environment. Even though there is a large abundance of the fish, I think
    that it could be good for the environment.

  • wjake-dav
    9/21/2016 - 03:05 p.m.

    I think they should shorten down the population of the giant gold fish. One reason that I think the population should be lowered because they are messing around the food web in that river. Another reason I think they should be lower is they are eating invertebrates and eggs and it says in the text "potentially consume invertebrates and fish eggs". One more reason they should be lowerd is the have disease, it says in the texts "they also are disease vectors. Tough's are my reasons that the population of the giant gold fish show get brought down.

  • bjenna-dav
    9/22/2016 - 06:31 p.m.


    In response to "Ginormous goldfish are invading Australian rivers," I disagree that _they say not to release any goldfish into the rivers because I had a goldfish and when it got too big, I had to put it in a lake or pond and nothing happened that was a problem. One reason I agree is that _they can spread disease to other animals. Another reason is that they can breed a lot. It says in the article that they breed like crazy in a warm environment that they love. A third reason I agree is that they are so big, it impacts the other living things in the water. Even though nothing happened in my pond, I think that it will happen in other ponds and lakes.
    _______________________.

  • smartina-dav
    9/22/2016 - 07:21 p.m.

    In response to "Ginormous goldfish are invading Australian rivers",I agree that over sized goldfish should not be realest into the wild. One reason I agree is because these goldfish are used to being in aquariums with friendly fish and being fed by humans, they have no experiences on the wild whatsoever. Another reason I disagree is that the river itself will be significantly effected by the unknown specie, "The fact that they're so big is really symptomatic of the other impacts in the river," Beatty said. It also says in the article that this has become such a big issue that a Boulder, Colorado lake teemed with the fish and in Alberta, Canada, and pleaded the pubic not to release them. A third reason is that because they are used to being fed with commercial pet food, their diet also effects the river, "their feeding frenzy also causes mud and debris A Boulder, Colorado lake teems with the fish and in Alberta, Canada,to rise from the bottom of the river. That fuels the growth of aquatic plants, which can degrade the river even further". this means that it not only effects the goldfish themselves but also the other species that live in the river. Even though some people can't effort or don't have time to take care of a pet any longer, I think people should really think about how much it really effects the rivers and the consequences of it.

  • lukeh-orv
    9/30/2016 - 11:38 a.m.

    I think goldfish interfere with the existing habitat because they consume invertebrates and fish eggs, they are disease vectors, and degrade the river by helping the growth of aquatic plants. When they consume the fish eggs they are destroying the next generation of fish for a species which can affect the environment. The article says," but their feeding frenzy also causes mud and debris to rise from the bottom of the river. That fuels the growth of aquatic plants, which can degrade the river even further." I believe these reasons are how goldfish interfere with the existing habitats. I enjoyed this article because I liked learning about how this tiny friendly goldfish can turn in a river monster!

  • gracef-ver
    10/07/2016 - 12:09 p.m.

    I personally believe that they aren't doing anymore harm than other fish in the rivers. I also believe that them growing bigger is a good thing. As weird as it sounds, with our population growing I think they may be used as a food source for people in the future.

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