FIVE THINGS ABOUT GOLDFISH THE SIZE OF A FOOTBALL

1 FROM PET TO PEST

The invasion begins innocently enough: A goldfish paddles the secluded waters of an at-home aquarium, minding its own business, disturbing no native habitats. The real trouble comes later, when the human who put it there decides it’s time for a change. Not wanting to hurt the fish, but not wanting to keep it either, the pet’s owner decides to release it into a local lake, pond or waterway.

That decision, experts say, is well-meaning but misguided — and potentially harmful.

2 BIG WARNING SIGN

Officials in Burnsville, a city about 24 kilometres south of Minneapolis, demonstrated why late last week, when they shared photographs of several massive goldfish that were recovered from a local lake. The discarded pets can swell and wreak havoc, the city warned. “Please don’t release your pet goldfish into ponds and lakes!”

the city wrote in a Twitter post, which had been liked and retweeted more than 15,000 times Sunday night.

3 ‘THE SIZE OF A FOOTBALL’

Burnsville, along with neighbouring Apple Valley, began surveying the lake’s goldfish population after residents complained of a possible infestation. Working with the company Carp Solutions, which specializes in controlling water pests, the cities sent a team to investigate, and even it was surprised by the size of the fish it found. “You see goldfish in the store and they’re these small little fish,” Caleb Ashling, Burnsville’s natural resources specialist, said in an interview.

“When you pull a goldfish about the size of a football out of the lake, it makes you wonder how this can even be the same type of animal.”

4 INVASIVE SPECIES

Far from being an innocuous domestic animal, a goldfish freed in fresh water is an invasive species, an organism that is introduced to an environment, can quickly reproduce, out-compete native species and destroy a habitat. And even though they get less attention than invasive organisms such as Asian carp or zebra mussels, goldfish appear to be a growing problem in bodies of water around the world.

5 TOUGH CUSTOMERS

Goldfish can live to be 25 years old, weigh as much as four pounds and measure well over a foot long. They’re also surprisingly resilient: They can survive in severe conditions and can weather winters in bodies of water that have frozen over, living for months without oxygen.

CITY OF BURNSVILLE One of several large goldfish pulled from a lake near Minneapolis. Officials in the U.S. are warning that the pets are dangerously invasive when released into the wild as they can quickly reproduce and harm native fish populations.