Spring Fish Migrations: A New Season of Hope

By Tys Theijsmeijer, Sr. Director Ecosystem Stewardship, Royal Botanical Gardens

April is the most intense month of activity at the Cootes Paradise Fishway as it’s spring spawning season for most of the fish species of the lake. To accommodate this period of fish migration extra operating days occur in the April operation schedule including Easter Monday. The Cootes Paradise Fishway enters its 28th year of operation and I have witnessed all of them firsthand. Early years of hope included both a positive transformation of marsh health, but also a big boast to the fishery. The Cootes Paradise Marsh – Spencer Creek system is a young fish producing supersized system and among the biggest on Lake Ontario. While the marsh is certainly transforming back to its historical self, the fishery rebirth has been slow, limited by setbacks as the inflowing urban pollution issues are more numerous than realized and the pace of repair while methodical is slow moving, while the urban area continues to grow.

Photos 1 &  2 courtesy of Brody White

For 2023 fish counts at the Fishway were some of the lowest of the last decade although still five times the first year, with the lower number perhaps the last echo of the 2018 Chedoke Creek sewage spill that killed much aquatic life. We look forward with new hope for 2024, and supported by 2023 young fish abundance, foresee rising fish counts for the future. In 2024 we will hopefully turn the page on the spills history and see spring spawning runs of fish increase. This March was positive with the first species in, the Rainbow Trout passing through in numbers more than double recent years.  Equally important is the Common Carp population, this sewage spill survivor has a dwindling pollution but still exceeds 10,000 large fish in the bay. In 2023 the fishway operations performed 690 cages lifts between March and October moving 13,200 fish into the marsh and 31 species including the ultra-rare and endangered status Spotted Gar – the second one ever caught over 28 years.

What about the water level? For fish, the question is whether the lake’s water level will be high or low in 2024. Currently, the water is trending below average, with this spring’s typically rising water level limited so far. With the warmer winter and no snowpack to melt, it seems likely we may only see another 15-20cm of water before it starts to decline in the heat of summer.