Why You Couldn’t See Salmon Spawning in Toronto’s Don River 20 Years Ago

Salmon in the water

If you’ve been lucky enough to spot salmon swimming up the Don River, you may be surprised to discover that 20 years ago fish such as chinook salmon and migratory rainbow trout were only able to access the lower 3 km of the Don due to in-stream barriers. These lower 3 km provided unsuitable environmental conditions for these fish species, and as a result spawning was unsuccessful.

Today we can see chinook salmon in the East Don River as far as 20 km upstream from Lake Ontario.

So what happened over the past 20 years?

Since 1996, TRCA has been instrumental in removing six significant barriers in the Don River. These efforts to re-instate aquatic habitat connectivity in the Don River was done with the support of the City of Toronto and York Region and its municipalities.

In-stream barrier removal was originally carried out as part of the 1994 Don Watershed Management Plan implementation, which identified in-stream barriers such as mill dams, weirs and in some cases roads and culverts as limiting the movement of fish and other aquatic species.

River flowing over rocks

River flowing over wier
Upper weir reconstruction May 1998 north of Pottery Road before (above) and after (below). Photo: Lost Rivers.

So what does this mean for the fish?

As a direct result of barrier mitigation projects, migratory chinook salmon, which are stocked in Lake Ontario, were found attempting to spawn in the Upper East Don River for the first time in 2005.

Not only does successful spawning promote self-sustaining fish populations, but being able to determine the presence or absence of juvenile trout and salmon is a useful indicator to assess the health of a watershed.

Want to learn more?

Read more about the work TRCA does in fish barrier mitigation, or for a detailed look at the work done in the Don, check out the Don River Watershed Plan. You can also read about the work done on the Pottery Road Weirs (pictured above) on the Lost Rivers website.