Monitoring Sensitive Fish Species on Seaton Development Lands

The Seaton development lands are home to important local populations of the provincially endangered Redside Dace (Clinostomus elongatus) as well as the sensitive Brook Trout (Salvelinus fontinalis), which is the only remaining native Salmonid fish species naturally occurring in Toronto and Region Conservation (TRCA) tributaries.

In early November, field staff from Toronto and Region Conservation’s environmental monitoring team visited the Seaton development lands to conduct visual surveys of Brook Trout redds during their fall spawning period. Monitoring crews were pleased to report 20 Brook Trout redds in the shallow headwater streams located near groundwater upwellings.

TRCA environmental monitoring team member studies sensitive fish species in the Seaton Development Lands

Brook Trout are known to prefer streams that have a year-round supply of cold, clear, well-oxygenated waters (less than 20 degrees Celsius) that are protected by overhanging branches, logs and rocks (Freshwater Fishes of Canada, 1988). For these reasons, Brook Trout are often used as indicators of excellent habitat and water quality conditions.

These habitat specialists are greatly impacted by an increase in impervious surfaces (e.g. roads, parking lots) in urbanizing areas because there is less opportunity for groundwater recharge, resulting in reduced baseflows and warmer stream temperatures.

Redside Dace

The provincially endangered Redside Dace is another important fish species found within the Seaton development lands. Their presence has been confirmed during routine Regional Watershed Monitoring Program (RWMP) fish community and habitat surveys, which have been conducted every three years in the Duffins watershed since 2003.

In addition, targeted sampling for Redside Dace was conducted in 2015 to help determine the extent of their range within the Seaton development lands. Due to its sensitive nature, TRCA used underwater cameras to confirm their presence at some locations.

This is an important fish species to monitor because it is a habitat specialist, preferring coolwater habitat conditions with overhanging vegetation. Its absence will signal that urban development activities are significantly altering the physical habitat as well as the cool, clear, flowing water conditions that Redside Dace depend on (Freshwater Fishes of Canada, 1988).

Beyond the Seaton development lands, limited populations of Redside Dace persist in the Carruthers Creek, Don River, Duffins Creek, Humber River and Rouge River.

Seaton Development Lands

The Seaton Community will be located within a large 2,785 ha parcel of land in the Duffins Creek Watershed in the City of Pickering, Ontario. The Central Pickering Development Plan outlines the blueprint for a new urban community of up to 70,000 people and 35,000 jobs, along with a designated agricultural preserve on the west side of Duffins Creek.

The Seaton project is unique because 53% or 1,520 ha of the planning area is designated as a Natural Heritage System (NHS) and will be retained in public ownership. The Ontario Ministry of Natural Resources and Forestry in cooperation with TRCA identified the NHS for Seaton, and this includes wetlands, forest blocks, valleys, floodplains, meadows, headwater streams and much of the Lake Iroquois shoreline, along with generous buffers and wildlife corridors to protect those features.

The urban development portion of the Seaton Community will incorporate advanced water management techniques such as Low Impact Development (LID) strategies to help mitigate the impacts of urbanization on the natural environment.

Due to the size and scale of this development, its sustainability aspects and the sensitivity of the nearby ecosystems, TRCA initiated a large-scale monitoring program in 2014 to evaluate the natural heritage of the Seaton development lands.

TRCA will be monitoring both the aquatic and terrestrial ecosystem (pre, during, and post development) to determine if the sustainability practices and the large NHS are sufficient to protect the ecological integrity of the sensitive natural heritage features within the project boundaries.

Currently there are long-term monitoring plots set-up to track changes in vegetation and bird communities, as well as aquatic sites to monitor fish and benthic macroinvertebrate communities. Conductivity loggers, used to estimate chloride concentrations, as well as year-round temperature and water quality monitoring stations are also in place.

Results from this monitoring program are expected to largely influence future planning decisions regarding the Seaton development lands and potentially future development activities in other TRCA watersheds.

Redside Dace is a sensitive fish species found in the Seaton Development lands area

Did you know? Redside Dace is the only minnow species to hunt flying insects by leaping out of the water. Their distinctive large mouth allows them to snatch small flying insects that hover about the stream surface, such as gnats, midges, mayflies and black flies (On the Don newsletter, Spring 2010).

More than 80 percent of the Redside Dace found in Canada occur in the Greater Toronto Area of southern Ontario, making urban development the most serious threat to the species (Fisheries and Oceans Canada, 2013).

Not only has the Redside Dace been designated as Endangered provincially, it is also been identified as a Species of Special Concern federally under the Species at Risk Act (2002). If it gains an official ‘at risk’ designation under the Species at Risk Act, critical habitat needed to recover the Redside Dace will be afforded protection and a federal recovery strategy and action plan will be developed.

The Redside Dace is also protected under the Ontario Fishery Regulations Act (2007) and the habitat section of the Federal Fisheries Act (1985). Read about its recovery strategy prepared under the Ontario Endangered Species Act, 2007.


Monitoring Matters! Through scientific data collection, TRCA’s Environmental Monitoring and Data Management team tell the stories about the changes affecting the natural areas and watercourses within our regions.  For more information, please visit our website, follow us on Twitter, subscribe to our Monitoring Matters e-newsletter, or visit our YouTube playlist.