Posted on Thursday, February 11, 2021
Pet fish dumped in local waterways have become the scourge of Hamilton’s marshes and harbour
Goldfish flourish in Hamilton Harbour’s low-oxygen conditions, growing up to 40 cm long by feeding on algae blooms that other fish species can’t eat (Fisheries and Oceans Canada)
Goldfish flourish in Hamilton Harbour’s low-oxygen conditions, growing up to 40 cm long by feeding on algae blooms that other fish species can’t eat (Fisheries and Oceans Canada)
Tys Theysmeyer remembers standing on the trail by Cootes Paradise marsh, looking out at the pond-like expanse that is linked by a narrow channel to Hamilton Harbour. Below the surface, he could make out a shifting mass he figured to be 100 feet long and 20 feet wide—a sea of goldfish. When it gets cold, they “school up,” he explains: “Fish that were dispersed over all of Cootes Paradise were suddenly in this tight ball, the kind of thing you’d imagine in the ocean.”
That November day in 2014 was when it hit home for Theysmeyer, head of natural lands at Hamilton’s Royal Botanical Gardens. What had been a few discarded pets had multiplied to millions, and the problem reached far beyond the marsh. Theysmeyer’s job entails conserving and restoring anything in the area that isn’t a manicured landscape—Cootes Paradise and Hamilton Harbour included. In 12 years in the position, he has witnessed an explosion in the goldfish population that has further imbalanced the area’s already stressed ecosystem.
The invasion isn’t unique to the Great Lakes, or North America. But Hamilton Harbour has proven an ideal home for the unnervingly resilient and destructive Carassius auratus, a cousin of the common carp that can grow from carnival-prize sized to a whopping 40 cm long. The water body has been used and abused over the decades, as sewage water and industrial by-products have flowed into the port since the 1800s with devastating consequences for the harbour’s flora and fauna. Today, treated sewage water, which isn’t fully cleansed of algae-causing nutrients, is still released into the harbour, along with occasional sewage overflow. The water has little to no oxygen, making survival a struggle for native fish species like walleye and yellow perch.
The goldfish, meanwhile, is the ultimate survivor of difficult conditions. Not only can you “stick it in a fishbowl in a kid’s room and not really worry,” says Theysmeyer, it can feed on blue-green algae blooms that native species cannot—blooms that appear with increasing frequency in Hamilton Harbour, due to pollution and warming water. What’s more, the creature’s bottom-grazing uproots vegetation and increases the water’s murkiness, both of which make life still tougher for other inhabitants. The goldfish, meanwhile, are rapidly reproducing. Without management, experts say, they’ll squeeze out their native competitors and take over.
The irony is, the goldfish explosion has coincided with a successful effort to bring down the number of common carp in Cootes Paradise and Hamilton Harbour, notes Christine Boston, an aquatic research biologist with Fisheries and Oceans Canada. Since 1997, the Royal Botanical Gardens’ fishway—a mechanism that filters out common carp trying to enter Cootes Paradise, an important spawning spot for indigenous fish species—has significantly reduced the number of the invasive species in the harbour. But in a classic case of unintended consequences, that resulted in less competition for goldfish.
Boston, who has worked on fish population monitoring at Hamilton Harbour for 21 years, often walks along the waterfront, from where she frequently spots vivid goldfish. “The fact that we’re still seeing brightly coloured fish in our catches means they’re still being introduced into the system,” she says. “Because nature will [eventually] select against them.”
Boston urges people who no longer want their goldfish to return them to the pet store, find them a new home or humanely end their lives (for those with the stomach, a large stone will work). Flushing them down the toilet is not recommended; it can send them into the ecosystem if sewage overflows before treatment—and that’s if they don’t die from cold-water shock.
But it’s not exactly a range of convenient and pleasant options, which might explain why people resort to dumping their fish tanks into harbours, creeks or neighbourhood stormwater retention ponds. Brook Schryer, who specializes in aquatic species at the Invading Species Awareness Program (ISAP) at the Ontario Federation of Anglers and Hunters, remembers a citizen calling about a pond in Kitchener, Ont., teeming with goldfish. He looked up the area on Google Maps and found satellite imagery of the pond in question: “You could see specks of gold. I could not believe the amount of orange in that water.” Stormwater ponds slowly empty into larger waterways, Hamilton Harbour being one of them. Schryer’s program does what it can to educate the public with presentations and social media messaging on why they shouldn’t dump their pets in the water. But “once a species is established, they’re almost impossible to eradicate,” he says. “At that point, it becomes about management and mitigation.”
Officials in Hamilton have been working toward that for a while. Last year, Boston’s team implanted tags in some larger goldfish to track their movements. They learned the fish aggregate in shallow waters in spring and summer, meaning crews will know where to find them if they want to remove them. In 2021, the team plans to implement smaller tags that can be scanned when the fish are re-caught; the ratio of tagged to untagged goldfish they catch will give them an idea of the overall number in the harbour.
The viability of removing the fish is something Boston expects to discuss this year with officials from the province, the Royal Botanical Gardens and Environment and Climate Change Canada. For now, she’s pushing for signs to be installed on the harbourfront trail reminding pet owners to not dump their scaly friends in the water.
But the ultimate solution, says Theysmeyer, “is fixing the water.” Local treatment plants are undergoing upgrades that should make a difference: in cleaner water, indigenous fish species can make a comeback and even prey on the invaders. And from a purely scientific perspective, the fact that conditions in the harbour have improved enough to support any kind of fish is encouraging, Theysmeyer says. “But it’s not the right kind of fish,” he adds. “That’s for sure.”
Feb 03, 2021 Prajakta Dhopade
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Posted on Wednesday, February 10, 2021
PORT CLINTON – Even as fishing in the “Walleye Capital of World” has certainly been living up to its name over the past two years, experts are projecting it could be on the verge of getting even better.
That capital, of course, is none other than Lake Erie, or even more specifically, its western basin, where the walleye population is reaching what scientists have described as “unprecedented” heights and is leading to incredible catch rates for anglers.
“Walleye fishing has never been better,” said Travis Hartman, a biologist with the Ohio Department of Natural Resources’ Division of Wildlife, about western Lake Erie.
Hartman serves as the Lake Erie fisheries program administrator, which monitors fish populations, along with production and harvest rates, aiming to establish appropriate and sustainable daily catch limits for sport fish such as walleye in partnership with other neighboring state agencies, including Ontario, Canada.
“Interagency management is the key to sustainability,” Hartman said. “We’re fortunate to have such cooperative partners around the lake.”
As part of that partnership, researchers conduct fish surveys in Ohio’s and Ontario’s territories in Lake Erie and combine their data to estimate the lake’s total populations, measure their ongoing rate of production and make projections for upcoming years.
Researchers use trawl nets, similar to the one pictured here, to measure the annual walleye hatch by catching “young-of-year” fish, meaning newly hatched walleye that are less than a year old.
The annual walleye hatch surveys are performed with trawl nets, which are used to catch “young-of-year” walleye, meaning newly hatched walleye that are less than a year old.
Hartman explained that up until very recently, 2003 had been talked about as having the biggest hatch ever seen, which was described as “the hatch that saved the fishery” and carried it for over 10 years.
“We were really fortunate to get it. It was kind of our anchor point to compare things against,” he said.
Now, however, the last few years have apparently kicked off a whole “new era” of walleye production.
Trawl surveys in western Lake Erie have documented enormous walleye hatches in 2015, 2018, 2019 and 2020.
Although 2020 is the smallest of those four examples, it is still considered another great hatch.
“Prior to 2015, I’d have been doing jumping jacks over our catches this year for young-of-year walleyes,” Hartman said. “We are in an incredible period of production.”
While the young-of-year walleye hatch in 2020 was lower than the previous two in 2018 and 2019, it is still considered a very productive hatch. Together, the recent hatches are leading to the highest walleye population estimates ever for Lake Erie in 2021.
While Lake Erie’s record high water levels in recent years have plagued some communities along the western coast, such as the city of Port Clinton, with frequent flooding — it also appears to be one of the most significant contributing factors to the booming walleye production.
“It’s becoming clear to me that high water is very helpful in producing walleye,” Hartman said. “If you look at the ‘80s, we had very high water. If you look right now, we’re in that same type of high water scenario, actually higher.”
He said he does not yet know precisely what dynamics associated with the lake’s high water levels cause the increase in walleye production, but speculated about the possibility of more sustained plankton blooms that walleye larvae need to eat or, perhaps, currents bringing larvae inshore, potentially putting them in nursery habitats and a better chance of surviving.
“The bottom line is, when we have high water, we’re producing a lot of walleye,” he said.
Another likely contributing factor is preceding hard winter seasons, meaning late ice coverage and a delayed spawning season for walleye.
“But these last years have shown, we don’t have to have a hard winter,” Hartman said. “When you look at the west and you look at production, high water trumps everything.”
Biologists are predicting Lake Erie’s walleye population to reach a record high of 151 million in 2021.
Given the high water levels of the past couple of year, with how many walleye that are in the lake now and with how many young walleye that are going to be coming in, Hartman described the fishery as in a “phenomenal” state and that it is going to be for years to come.
Using 2003 again as a point of comparison, that year’s hatch helped the lake’s walleye population top 120 million in 2005, which Hartman said was comparable to the population level at their best during the 1980s.
Lake Erie then entered somewhat of a period of decline for walleye. According to Hartman, the lake simply did not get hatches like that of 2003. That is until recently.
The walleye population estimate for 2020 was 116 million, the most since 2005.“Now, with 2019 coming in next year as 2-year-olds in 2021, the first look estimate has it at 151 million, by far the highest we’ve ever seen in the lake,” he said. “It’s going to be up for quite some time.”
The walleye harvest rates in Lake Erie have reached record highs in 2019 and 2020, according to the Ohio Department of Natural Resources Division of Wildlife.
That high population is also manifesting in high harvest rates for walleye, a statistic that has been tracked in Lake Erie for around 40 years.
“Things were as good as we could’ve ever hoped for back in the ‘80s, when we were at a half a fish per hour as far as the targeted walleye harvest rate,” Hartman said.
After that period, as populations changed and the fishery changed, catch rates were generally lower.
It was not until 2006 and 2007 that catch rates rose to high levels again, when walleye from the big 2003 hatch were so abundant, Hartman explained. The rates then declined again until skyrocketing recently.
“We’re at a point now where our harvest rates are approaching double what they were in the ‘80s,” he said.
Hartman can remember experiencing how great of a fishing period it was as a kid at that time.
“For a long time, we looked at the ‘80s as something we might never achieve again from a fishery perspective, but it is this good right now — these are the good old days,” he said. “We really have something special right now for a walleye fishery and I encourage everyone to experience it and enjoy it.”
Jon Stinchcomb-Port Clinton News Herald
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