However, releasing these little guys into open water turns out to be a significant issue. They not only balloon in size but also multiply at an alarming rate. Their voracious appetite leads them to wreak havoc by tearing up and devouring anything in sight. Consequently, the water takes a turn for the worse, becoming dark and murky, posing a substantial challenge for the Great Lakes.
From Bridge Michigan:
Feral goldfish have been invading much of North America, including the Great Lakes, for decades and recently their numbers seem to be rising rapidly. The reason for the uptick is not clear, but it could be because invasive carp are being better controlled, and the goldfish are taking their place. New designs for stormwater ponds, where people often dump unwanted fish, that allow the ponds to overflow into nearby waterways could also be boosting the numbers.
While goldfish may seem small and vulnerable, they are actually very good invaders. They are hardy and adaptable, able to survive and thrive under a wide range of temperature and oxygen conditions that many native species can’t handle.
But little is known about how they live in the lakes, making it difficult to come up with effective management strategies. So Christine Boston, a biologist at Fisheries and Oceans Canada’s Great Lakes Laboratory for Fisheries and Aquatic Sciences in Burlington, Ontario, and her colleagues set out to learn more about the fish that have made their home in Hamilton Harbour on Lake Ontario.
They captured 19 large goldfish – each at least a foot long and weighing up to 3 pounds – and implanted them with acoustic tags that could be tracked by a sensor array originally installed to monitor stocked walleye. Over the course of two years they followed the fish, noting where they liked to spend their time. Interestingly, some very clear, and unexpected, patterns emerged.
It's almost mind-boggling to imagine a three-pound goldfish, especially when you consider that your average domestic goldie tips the scales at a mere 8 ounces.
