3-Pound Goldfish Found—How’d It Get So Big?

As an avid fisher for 20 years, Mike Martin has his fair share of stories. Many fishers can tell tales of the one that got away, but Martin’s latest yarn is all about the one he reeled in earlier this month on Lake St. Clair (map), just north of Detroit, Michigan.

“Basically, I was doing what I always do, trying to catch perch, and I thought I had a big perch on. Um, definitely not a perch,” Martin told WDIV News, the NBC affiliate in Detroit. (Watch a video of the giant goldfish on KSDK.com.)

A 15-inch goldfish named Bruce is lifted from the water at a fish farm in Dongguan, China, in 2002. Photograph by Bobby Yip/Reuters

Indeed not. On his hook was a 15-inch-long (38-centimeter-long) goldfish that tipped the scales at 3 pounds (1.4 kilograms). Compare that to an average aquarium goldfish that generally measures just a few inches—their breeds come in a wide variety of sizes—and it doesn’t take long to figure out that this whopper of a fish is going to need a bigger bowl. (See a picture of a see-through goldfish.)

That begs the question: What exactly is a goldfish, and how can they get so freakishly big?

Goldfish: Carp in Pretty Clothing

Goldfish are actually a type of domesticated carp. Almost 2,000 years ago, the ancient Chinese began to domesticate Prussian carp, Carassius gibelio, for food and as ornamental fish.

Over time, mutations creating orange, red, and yellow colors began to emerge in the dull-colored Prussian carp, creating the coloring we now associate with goldfish. The fish was transported to Europe in the 1600s and to the United States in the 1850s.

Although not naturally found in the wild, goldfish have occasionally been found in ponds, lakes, and streams. Most researchers believe that these goldfish were either dumped there or somehow escaped from the “porcelain express” after being flushed down the toilet.

Many of the unusually massive goldfish—like the one Martin caught—have been found in these outdoor settings, but goldfish experts say it’s a myth that a large tank will yield large goldfish. (See pictures of the world’s monster fish.)

Big Fish in a Small Pond

To grow a big goldfish in a small pond, breeders focus on two main factors: food and temperature, according to Tropical Fish Data, a database on tropical fish. A high-protein diet is generally thought to increase the body weight of a goldfish, as is being fed more food, more often.

Warm water also increases a goldfish’s size. Goldfish kept in outdoor ornamental ponds generally grow quickly in summer and little, if at all, over winter. Keeping goldfish in a heated aquarium allows them to maintain their summer growth spurt year-round.

The longest known goldfish, according to Guinness Book of World Records, measures 18.7 inches (47.4 centimeters) from nose to fin and belongs to Joris Gijsbers of the Netherlands. Guinness did not have any official recordings of the fish’s weight, so it’s unclear if the Dutch goldfish beat the new Lake St. Clair goldfish in bulk as well as length. (Also see Biggest Great White Shark Caught, Released.”)

Martin hasn’t purchased a swimming-pool-size fish tank for the goldfish he caught, nor is he hosting a neighborhood fish fry. Instead, he’s currently keeping the specimen in his freezer—he ultimately intends to mount it on his wall.

Carrie Arnold is a freelance science writer living in Virginia. When she’s not writing about cool critters, she’s spending time outside, drinking coffee, or knitting.

Carrie is a freelance science writer living in Virginia. When she's not writing about cool critters, she's spending time outside, drinking coffee, or knitting. You can visit her website at http://www.carriearnold.com
  • Mike Martin

    WOW…..Thank You for covering my story.

  • Jenny

    What a fascinating story! Now I can’t get the image out of my head of a very large fish popping out, fishlips first, from a teeny tiny fishbowl.

    Regarding the comments criticizing Mr. Martin for not releasing the fish: could ornamental carp become invasive in the upper midwest? Although a thing of beauty, it seems rather good that this non-native fish hasn’t been left to lay its eggs all over Lake Clair.


  • sydney

    i used to live in michigan

  • Markos

    Wow amazing

  • ryan

    HA! I’ve been keeping fish for 15 years and I always told people goldfish get huge, this is just more proof!

  • Joe Brown

    Goldfish in the mill dams at coats threadmills Paisley were easily 3lbs and more.

  • Suzanne Spittal

    I sincerely hope this fish was put back in the water immediately and not allowed to die just for the sake of taking some pictures.

  • Davie

    I am agree with @Marcos Uchoa,It is right that what did he say!

    we are exporting the best quality goldfish and good price in shanghai,china

  • Josh

    Donate that fish at GoldfishSwallowing.com. Their model won’t eat that kind af big fish.lol!

  • michael allen

    my pet goldfish was 5 pounds before it died.
    and this is shocking news?
    i thought that 3 pounds was average for a full grown goldfish

  • Pam

    He killed that gorgeous creature so he can mount it on his wall? That’s disgusting. I’m appalled at the lack of compassion people like this guy have for sentient creatures. He should not be celebrated, he should be condemned.

  • Nathan

    Yeah why not let the poor creature live. The worst it could do is find another goldfish, breed, become the parents of millions of goldfish that make their way through a ton of midwestern streams and lakes killing native fishes as it steals food and eats several smaller fish and destroying plantlife all along the way. But sure let it live just the same way as we should let asian carp live. Think before you speak people

  • Chelsea McCluer

    I love how people think the fish in the picture is the one that was caught. The fish in the photo is Bruce, the World’s largest Oranda. Mike didn’t catch that.

  • Thatguy

    He should have put it in a personal pond or tank. I have three goldfish in a 55 tank that WILL NOT STOP GROWING and they dont need to be stuck in my freezer.

  • Lilly

    How did it get so big? Because it’s a goldfish! Goldfish quite simply get big. That’s like asking how did an elephant get so big. And I find it hard to trust this article (from national geographic, no less!) after it said goldfish only “get a few inches” and “need a bowl.” Goldfish on average get 8-14 inches long and need 20 gallons per fish. A bowl is unnacceptable

  • James Dickson

    Very informative blog..I love to read the goldfish swallowing blogs and after that, I result up to website where similar kind of videos and information

  • Something

    I do not understand why people are angry that the fish was killed. Firstly the fish did not belong where it was living. Secondly if it were any other fish you probably wouldn’t care. Fish are killed all the time, the only time you should truly worry about someone killing a fish is if it is endangered.

  • Bill oFell

    Wow. We have at least a 3 to 5 pound goldfish swimming in the retention pond in front of our residence hall. I feed it bread and corn all the time!!!

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