Restoration of Atlantic Salmon to Lake Ontario: Past, Present and Future

The Atlantic salmon was once an important part of the fish community of Lake Ontario.  There are many colourful accounts of Atlantic salmon in the journals of early settlers.  Fish weighing up to 40 pounds were reported, but the average was probably around 10 pounds. One writer noted that "farms are reported to have been bought and paid for, and houses built, from the sale of salmon".

The Credit River was renowned as an Atlantic salmon stream, but salmon thrived in many other Lake Ontario tributaries including Wilmot Creek, Duffins Creek, Cobourg Brook, the Humber River and the Don River. However, in less than a century, a resource that seemed limitless had all but vanished from the lake.  Habitat loss and overfishing led to the extirpation of this important native species.

• Dams were constructed to provide waterpower for grist and saw mills.  These dams prevented adult salmon from migrating upstream to spawn.
• The removal of forest cover (which shaded stream banks) led to the warming of streams. This made the streams uninhabitable for salmon, which are a cold-water species.
• Runoff covered spawning gravel and nursery areas with silt.
• Overfishing also contributed to the decline of Atlantic salmon. Many, many salmon were taken for food and commerce using spears and nets.

One of the last observations of an Atlantic salmon in Ontario waters was from Wilmot Creek in 1896.

The Present

Research and experimental stocking have laid the groundwork for a major new partnership to bring back the Atlantic salmon to Lake Ontario. There are many reasons to tackle this ambitious restoration project.

Atlantics once played a key ecological role in the lake.  They were a top predator in the offshore fish community.  This native species was also a valued resource for First Nations communities and early settlers.  As such, Atlantic salmon are recognized as an important part Ontario’s natural and cultural heritage.  Atlantic salmon are a good barometer for watershed health.  They are also highly regarded by anglers.

The goal of our partnership is to restore wild (self-sustaining) populations of Atlantic salmon to Lake Ontario.  Research has shown that young Atlantic salmon can grow and survive well in Lake Ontario tributaries today.

Juveniles are most at home in the fast water (riffles) of coldwater streams.  They defend their territories vigorously and thrive in areas with an abundance of in-stream cover and clean gravel.

Currently, our efforts are focused on three “best-bet” streams: the Credit River, Duffins Creek and Cobourg Brook.

We are increasing stocking levels, to take advantage of good quality spawning and nursery habitat.  We are monitoring adult returns and production of wild juveniles.  We will compare the effectiveness of different stocking strategies and the performance of different strains.  We are working on habitat improvement projects with community groups and the cooperation of landowners.  We will study how Atlantic salmon fare in the lake, especially in light of ecological changes sparked by aquatic invaders.

The Future

Mark Donaldson (left) of Churchill Cellars, representing Banrock Station Wines, and biologist Warren May of MNR's Aurora District office, release fall fingerlings in Duffins Creek.  Photo credit:  Marion Daniels

Much has changed in Lake Ontario and its tributaries since the 1800s.  While there are many challenges to restoring Atlantic salmon, we are optimistic about our chances for success.

Bringing back a native species takes time.  But, our plan has laid out milestones against which we will measure and celebrate our success along the way.

To find out more about this exciting program, meet our partners and discover volunteer opportunities, please visit the Bring Back the Salmon website or contact MNR's Lake Ontario Management Unit at (705) 755-1345.