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A Fish Die-Off in High Park’s Grenadier Pond Perplexes Officials

Officials don't know why hundreds of fish died in High Park's Grenadier Pond earlier this week.

Dead fish in Grenadier Pond on Wednesday.

The stench was noticeable within twenty metres of the shoreline. Earlier this week, there were hundreds of dead fish in groupings of dozens along the southeast side of High Park’s Grenadier Pond, some floating, some half-eaten, others bloated with decomposition. The die-off happened days ago, but officials still aren’t sure what caused it.

“I found out about it on Monday morning,” explained Lenka Holubec, a volunteer with the High Park’s natural environment committee. “I come down here to check on the pond, and I walk the trail usually twice a day, because of the lines that some fishermen leave behind.”

“As I walked, I noticed that after the pier there were dead fish,” she said. “It wasn’t until I saw all these juvenile fish, of various species, in layers lying on the shoreline, being eaten by the birds around, that I became horrified by the sight.”

“I was just walking and breathing,” she explained. “[My reaction] was delayed because at first it was a few dead fish, but then it was a lot of dead fish, and the smell was so intense that day because it was sunny and hot. It was extremely strong.”

Rick Portiss, the supervisor for environmental monitoring at the Toronto and Region Conservation Authority, also found out about the occurrence on Monday.

“It was passed on to my boss,” he said. “He came to me saying that we should go down to Grenadier Pond because there’s been a fish kill.”

“It looks like species that use the shallow water areas are the ones affected,” Portiss said. “We just went for a little tour to look around Monday and saw the pan fish lying along the eastern shoreline.”

Among the dead fish were the usual “pan fish,” such as pumpkinseed fish. There were some small bass, rock bass, perch, and a juvenile pike. “We haven’t seen a fish kill of this size in a while,” Portiss said.


TRCA’s team used a HydroLab—a piece of portable testing equipment—to take measurements of the water’s temperature and amount of dissolved oxygen. They suspected that a lack of oxygen in the water, possibly caused by an algal bloom or water stagnation in hot weather, was the culprit. This turned out not to be the case. “Everything seemed to be fine and we’ve ruled out anoxia,” Portiss said. “The next step is a chemistry test by the MoE [Ontario's Ministry of the Environment] and MNR [the Ministry of Natural Resources]. We’ve handed over the investigation, because we’ve gotten as far as we can.”

“What we know at this point is that various species were killed in Grenadier pond,” explained Jolanta Kowalski, a spokesperson for the Ministry of Natural Resources. “So we are sending water and fish samples to the University of Guelph for analysis.”

However, according to Kowalski, the analysis will take time.

“Water samples can take a couple of weeks,” she said. “Depending on how busy the lab is. But the fish samples, I’m not sure how long it could take.”

According to Kowalski, the ministry has encountered situations similar to this before, although there are usually stand-out circumstances, like a recent storm or extreme temperatures. This time is different because of the variety of species affected. Ministry officials don’t have any specific concerns about contaminants, and haven’t said the pond water poses a risk to public health.

Even so, Kowalski recommends that locals keep their pets away from fish carcasses, “as we would normally tell the public not to let their dogs eat dead and decaying things.”

Park patrons can breathe easy, and deeply, because the City will be taking on the cleanup project, according to the acting supervisor of High Park, Dave Chapman.

“We don’t get our feet wet,” said Chapman, referring to the water in the pond, which falls under the Toronto and Region Conservation Authority’s jurisdiction. “But we are going out and guiding some of the long-handled pool skimmers to clean up the fish as they get close enough to the shore that we can reach them. We’re just waiting for them to come into shore, but as they come in, we will be cleaning them up.”

Photos by Giordano Ciampini/Torontoist


  • HotDang

    The most obvious explanation is that they drowned because of all the extra water from the flooding a few weeks back.

  • Steve j

    Last year I taken photos of similar event around same time if year but smaller number of fish and reported it.

  • glenn_storey

    i’m betting it’s all the goose shit.

    • wklis

      More likely storm runoff from the streets or upstream (dog, geese, raccoon, etc.). I still see leftovers from the dumping of toxins, such as paint, down the sewer grates on the streets.

      The good news is the city is attempting to separate sewage and rain storm sewers. The bad news is that people continue to use the sewer grates as disposal sites.

  • John Norton

    Much of the area around High Park was used as a large municipal landfill many years ago. In fact the pond was much larger and there were a few smaller ponds and steams in the area towards lakeshore and windermere. It was common back in the early 1900′s and late 1800′s to fill in these areas for development and as a way of dealing with trash. It would not shock me to learn that years later leaching from these long forgotten trash piles has caused a toxic effect with the pond.

    • wklis

      Rennie Park, near the foot of Runnymede Avenue, was such a dump.

      BTW. Back when there was the garbage strike, it actually turned some parks back to their original use.

  • Mike Robinson

    It was the excess rain that washed a lot of top soil and pollution etc. into the water .I also noticed no fish in the legendary Humber river etienne brule Park .

  • Real Life

    Shame and scary, until people start to drop like in … then we will wake up. The time is coming. They are finding gulls in the middle of the ocean with 2lbs of plastic caps in their bellies. Watch… so many people simply do not understand the whole concept of a food chain , cause & effect, and finally, consequences.

  • Functionalist

    To see something on this scale suggests that either something extraordinary happened to an otherwise clean aquatic environment like a spill, a large scale application of illegal pesticides or dumping, or that the water was already polluted and excess polluted water from a storm simply brought the water quality down to a level that could no longer support life for these species.