‘Super invader’ monster goldfish are taking over Hamilton stormwater ponds by the thousands

Lurking in the depths of an Ancaster stormwater pond is a bloated, football-sized, probably abandoned pet goldfish named Chunks - and it's not even the scariest part of this story.

Scientists with Fisheries and Oceans Canada spurred an online furor this week by posting photos of the nearly four-pound fish, who at 35 centimetres from nose to tail is longer than an NFL football, but similarly shaped.

A two-handed scientist grip is required to encompass Chunks' swollen tummy - a protuberant pot belly likely due to kidney failure, rather than, say, devouring other escaped pets.

Chunks looks scary, the internet agrees - but far more terrifying is the fact it is just one big fish in a small pond stuffed with tens of thousands of other goldfish.

It's becoming quite a problem ... we're finding them everywhere," said Christine Boston, a federal aquatic science biologist who is studying invasive goldfish in Hamilton's stormwater ponds as well as the harbour. The fish are getting into these ponds somehow, most likely with help from people."

One goal of the three-year project is to study what, if anything, can be done to control the exploding pond populations - and by extension, prevent the ecologically damaging super invader" from escaping into ditches, creeks and eventually, Lake Ontario.

So far, Boston's team has found more than 40,000 goldfish squeezed into stormwater ponds the size of a suburban backyard in Ancaster and Stoney Creek. Another pond, behind the Walmart in Waterdown, appears to be home to thousands of the abandoned pets and their progeny, too.

Now do the math. Hamilton has 70 storm ponds - the human-made lagoons that suck up stormwater and run-off from roads, often around new housing developments - that have water in them year-round. Many larger cities in the GTA have between 60 and 85 similar ponds.

In theory, hundreds of thousands of the decorative carp cousins could be lurking in local ponds - maybe twice as many as the number of actual human Hamiltonians!

So where do they all come from?

It starts with that goldfish you never really wanted. Maybe you didn't have the heart to flush Goldie and decided it would be kinder to let him or her live out life in the stormwater pond near your home.

Unlike Chunks, not all abandoned fish grow to the size of the pet cat you actually wanted. But female goldfish can lay up to 10,000 eggs at a time - and the popular aquarium pets are among the most pollution tolerant of invasive fish troubling the Great Lakes.

That's why the outdoor goldfish bowls are a potential environmental nightmare, rather than just a creepy oddity.

Hamilton storm ponds drain excess water into local ditches or creeks, said Dave Alberton, the city's wastewater collection manager. For example, the pet-infested ponds in Ancaster and Stoney Creek feed into the Grand River and a tiny creek that dumps out into Lake Ontario, respectively.

They're going to find that local watercourse and sooner or later they're going to make it to a lake," said Alberton.

Abandoned pet goldfish are a long-standing Great Lakes problem - but ironically, they only swam onto the most unwanted list in Hamilton Harbour when we finally started winning the battle against invasive carp.

Boston said researchers are using high-tech tags to track goldfish movement in the harbour and have found the species is muscling out native fish like pike by targeting breeding sites.

Aquarium escapees also pose a unique problem" for recovering Cootes Paradise marsh at the west end of the harbour, said Tys Theijsmeijer, a longtime champion of restoration efforts in the natural fish nursery owned by the Royal Botanical Gardens.

A special barrier wall prevents most carp from entering the marsh - but smaller goldfish are still free to roam, stirring up sediment and uprooting native plantings.

Boston said the goldfish research project, which includes the city as a partner, aims to make it easier to identify and control problem populations in stormwater ponds. To start, the city is working on new signs warning visitors against releasing pets in storm ponds.

It's possible the study will result in a recommendation to kill goldfish in some ponds - although it's not an easy or cheap option. You can't empty a storm pond without first mounting a rescue" mission for native fish and wildlife, noted Alberton.

Long-term, the solution to the goldfish conundrum is twofold, said Theijsmeijer. First, we need to clean up the harbour to the point native fish populations can recover and thrive," he said. Second, we need people to stop dumping their pets in the water."

Matthew Van Dongen is a transportation and environment reporter at for The Spectator. mvandongen@thespec.com