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
Lexile

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."

Filed Under:  
Assigned 75 times
CRITICAL THINKING QUESTION
How do the goldfish interfere with the existing habitat?
Write your answers in the comments section below


COMMENTS (27)
  • benjaminc-bla
    9/15/2016 - 09:19 a.m.

    They interfere because they are used to being in a tank, and when they feed, they get so crazy, they cause mud and debris to fly up. This causes the river to degrade faster. They often consume other fish eggs or invertebrates, which lower the amount of other animals in the river. Scientists also think the goldfish often spread the diseases the other fish can't cope with.

  • lukel-bla
    9/15/2016 - 09:37 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!

  • kirins-bla
    9/15/2016 - 09:38 a.m.

    I thought this article was very interesting. I never knew that goldfish could grow so big. The goldfish steal other fishes eggs and their eating spree causes mud to rise which can further hurt the river. We have to spread the word so people don't release their goldfish anymore.

  • andrewt1-pav
    9/15/2016 - 10:01 a.m.

    The fish could be a problem, but they could help the animals that prey on the fish like bears could grow and that could help potential predators that are endangered.

  • adamk-pav
    9/15/2016 - 10:04 a.m.

    That is interesting. It is wild that the goldfishes are so big and colorful. I think the bears in the park will eat all of them tough, witch it good because then they have a lot of food.

  • liamf-pav
    9/15/2016 - 10:07 a.m.

    These fish will help the habitat grow as they are now another food source for the bears that live in it

  • genm-pav
    9/15/2016 - 10:11 a.m.

    I think that these over sized goldfish are cute but could cause problems with the population by either harming other animals or overfeeding the bears

  • nicholasf1-bla
    9/15/2016 - 10:18 a.m.

    The Giant Goldfish in Australian rivers are taking a toll on the environment. Theses normally quiet, small, fish have transformed into huge monsters! the warm nutrient rich environment has lead to huge gold fish and a lot of them. The gold fish interfere with the environment because they stir up the rivers and allow plant life to excel. this will mess up the fragile food chain. If the food chain becomes corrupt it could put animal species at risk of extinction.

  • alexandere-bla
    9/15/2016 - 10:33 a.m.

    What I think on how goldfish interfere with the existing habitat is that they eat other fresh water creature's eggs. that lowers the amount of animals in the river. They cause debris to rise up and that causes aquatic plants to grow faster. Also this causes the river to degrade faster. Scientists also think that goldfish spread diseases that other animals can't live with. I like this article because it gives a lot of facts about the goldfish and how they are changing the rivers environment.

  • audreyj-bla
    9/15/2016 - 11:48 a.m.

    Goldfish are taking over the Australian rivers. The goldfish are pretty big and they are eating all the food in the rivers. That means the other fish and animals don't have a stable food supply, which could possibly lead is a large decrease in other species. They are eating fish eggs and invertebrates. When they feed on these things they cause debris to fly up and that fuels the growth of aquatic plants and will degrade the river more and more. I believe that is more people go fishing in these rivers for meals, it will balance out the food chain, that meaning more species could flourish and have enough food for them to survive.

Take the Quiz Leave a comment
ADVERTISEMENT