It was the best of times, it was the worst of times, the stream was filled with trout, the stream was empty of trout, the water was cool and gentle, the water was warm and severe, anglers were full of hope, anglers were laden with doubt (with apologies to Charles Dickens). The Millbrook Dam splits Baxter Creek into two distinct stream sections that differ in fish populations and habitat. Brook Trout, Brown Trout, and sculpins – all coldwater species – dominate upstream of the dam. Downstream we find Brown Trout and mix of coolwater and warmwater minnows and suckers. As we move downstream the Brown trout become fewer as the water becomes warmer.
Baxter Creek is born with the springs and groundwater of the Oak Ridges Moraine. These springs are the most critical feature of trout habitat in southern Ontario. Groundwater, here, is usually 8 to 10°C and keeps streams cool during summer. The best trout streams remain below 22°C on the warmest days. Trout spawn more successfully in the presence of groundwater, and moreover, Brook Trout seek out springs for spawning. They are rarely successful in areas without springs. The sand and gravel soils of the Oak Ridges Moraine contribute to high infiltration of rain and to high groundwater flows.
The geology changes at Millbrook, and finer soils in the watershed of downstream Baxter Creek lead to fewer springs. Brook trout cannot find suitable spawning habitat and are not found here. As well, the mill pond at Millbrook exposes Baxter Creek to the sun’s warming. In 2019 the Millbrook Chapter of Trout Unlimited and Sir Sandford Fleming College conducted temperature surveys of Baxter Creek, and we found that the mill pond warmed the creek from a maximum of 17°C upstream to 23°C. Two small cold tributaries in Millbrook may be the saviours of the Brown Trout population in downstream Baxter Creek. Not only do these cold tributaries slightly counteract the warming of the mill pond, these are Brown Trout nursery streams. Trout Unlimited found numerous juvenile Brown Trout during electrofishing (nonlethal) surveys of these streams this summer. Similar surveys by Fleming College found adult Brown Trout in Baxter Creek near Millbrook. Trout Unlimited found only one large Brown Trout below Cedar Valley in our electrofishing survey. We found water temperatures here – especially at night – were too high for trout, and their survival in this stream section may only be possible in pockets of cooler water formed by springs.
The Millbrook Chapter of Trout Unlimited hopes to rehabilitate trout habitat in downstream Baxter Creek through protection and enhancement of the nursery streams in Millbrook, and lowering the stream temperatures. We plan to work with landowners to plant trees for shading the creek, and work with Otanobee Conservation to find solutions to reduce the impact of the mill pond on stream temperatures.