The Uninvited


Stormwater ponds in Ontario have some unexpected, and unwanted, guests: goldfish. Thousands and thousands of them. And they’re stirring up trouble—or at least sediment.

The goldfish are a species of carp, native to Asia and considered invasive in North America. Unlike other species of Asian carp that threaten the Great Lakes, which originally escaped from fish farms in the region, these goldfish are believed to be descendants of pets that people have released into the wild. They’re not as harmless as they might sound, though; given enough space to swim, they can grow up to 16 inches or so long, and they produce a lot of waste, polluting the water.

Local conservation authorities that monitor the manmade stormwater ponds for pollutants like nitrogen, phosphorus, and metals have discovered that the increasing numbers—and size—of the goldfish are a significant contributor of pollutants in the ponds and, ultimately, in Lake Erie. The first clue, one environmental manager explains in this article, was increased turbidity in the stormwater ponds; officials eventually discovered that the bottom-feeding fish were stirring up sediment rather than letting it settle. In fact, the tremendous amount of silt and sediment in the water column is keeping them from getting an accurate estimate of just how bad the problem might be.

Officials aren’t quite sure what to do about it, either. One proposed solution is “electrofishing” in the ponds during regularly scheduled maintenance.

In the US, different states in the Great Lakes region are considering a number of strategies to deter or kill Asian carp, including electric barriers, dikes, chemicals, noise-making systems to chase the fish from certain areas, and even spraying boats with jets of water to remove any “hitchhiking” fish as they pass certain points. Some of these efforts are still in the drawing-board stage, but the federal government has spent more than $300 million to try to prevent a wholesale invasion of the Great Lakes. The danger is that the carp could outcompete native species like walleye and rainbow trout, with devastating effects on the commercial and sport fishing industries.

Western Water Summit Call for Speakers Is Open

The Western Water Summit will take place February 6–7, 2019, in San Diego, CA. It focuses on all facets of water management: groundwater, surface water, wastewater, drinking water, irrigation, water law, reuse, generation, restoration, conservation and efficiency, and erosion and sedimentation. The Call for Speakers is open until November 1. Find more information about the conference tracks and registration at SW_bug_web

  • Rainbow trout are not native to any water east of the Mississippi; they’re an introduced species. Throw a few northern pike (native species) in those storm water ponds and you won’t have a carp or siltation problem.

  • Realist has a point. Sometimes engineering our way out of a problem just leads to more problems. If ‘slough sharks’ don’t do the trick or are also problematic as a non-native fish species for a given area I believe this problem is actually solved by making our communities more responsible for costs associated with damage members of that community cause.
    Plan B. Drain the ponds. Explicitly expense the community on a household basis for costs associated with draining the ponds. When the ponds refill the goldfish will be gone. Undoubtedly the community will be concerned enough that anyone observed going near the ponds will draw the ire henceforth.


Leave a Reply

Enter Your Log In Credentials