[URBAN NOTE] "Discarded goldfish are taking over Hamilton's harbour"

[rfmcdonald]

The descendants of abandoned goldfish, CBC's Samantha Craggs notes, are populating Hamilton's harbor.

Researchers at the Royal Botanical Gardens (RBG) have counted as many as two million large and small goldfish this year, fish that are likely descendants of people dropping unwanted pets in the water.

Now there are so many that they're throwing another wrench into attempts to rehabilitate the bay.

This year, the RBG team has counted as many as 2,500 large goldfish and two million young, said Tys Theysmeyer, head of natural lands with the Royal Botanical Gardens (RBG). They seem to be thriving thanks to climate change, and poor water conditions that have discouraged native species from flourishing.

RBG spotted handfuls of them dating back to the 1990s, Theysmeyer said. But lately, the problem has worsened.

"People used to actively release goldfish into the bay a lot," he said. "In the last five years, their numbers have been rising and rising."

[. . .]

In Hamilton, the numbers are rising from a perfect storm of water conditions. Warmer water temperatures mean that new fish species such as the goldfish can survive, where decades ago it might not have. Theysmeyer says pressures on water quality in the bay, such as contaminated overflow from the city, have also caused a decline in native fish species, leaving more room for goldfish.

Native fish such as northern pike, freshwater drum and several sunfish and minnow species are in short supply, Theysmeyer said. He estimates that only two species — namely yellow perch and blue gill — are showing up in greater numbers.