Fish Habitat and Communities

Fish are excellent indicators of stream health because they are sensitive to changes in their environment.

What Are We Monitoring?


Toronto and Region Conservation Authority (TRCA) surveys fish communities and their aquatic habitats as part of the Regional Watershed Monitoring Program (RWMP). The sampling occurs on a three-year cycle, with three watersheds sampled each year.

In 2022, TRCA sampled the Rouge River, Duffins Creek, and Carruthers Creek watersheds. This is the seventh time the RWMP has completed sampling in these watersheds.

TRCA team members use stream electrofishing to monitor fish species
TRCA monitoring team member conducts fish species identification and measurement

Monitoring follows the Ontario Stream Assessment Protocol (OSAP) and uses back-pack electrofishing methodology.

Each fish is identified to species, measured for length and weight, and released back into the water. More than 9,000 individual fish records were collected in 2022.

Aquatic habitat conditions are also assessed. This includes measurements for stream width and depth, water temperature, and sediment type.

Visit TRCA’s Open Data Portal to view the most recent fish data collected in the Toronto region’s nine watersheds.



TRCA actively surveys fish communities along the regional waterfront each year. Fish survey methods include boat electrofishing, nets, and underwater photography.

These surveys are used to track the success of restoration projects and Remedial Action Plan (RAP) measures for the Toronto and Region Area of Concern.

A boat with staff electrofishing
TRCA monitoring team member uses seine to conduct nearshore fisheries monitoring on Scarborough waterfront

Nearshore fisheries surveys have been underway in the Toronto Harbour since 1989. More than 50,000 individual fish records from approximately 500 sites have been collected over the last three decades.

Inland and lake fish and habitat assessments, as well as fish rescues, are also carried out within the Toronto region in support of various habitat restoration projects, environmental assessments, and research studies.

Read About Fish Communities on the Toronto Waterfront

TRCA also coordinates Aquatic Habitat Toronto (AHT).

AHT is a group of agencies – municipal, provincial, and federal – sharing a common interest in improving the aquatic habitat along the Toronto Waterfront. AHT focuses on fulfilling the goals of the Toronto Waterfront Aquatic Habitat Restoration Strategy (TWAHRS).

Read About Fish Habitat Restoration

You can view an interactive storymap to learn more about the TWAHRS techniques used in waterfront aquatic habitat restoration.

Select the image below to open the storymap.

Toronto Waterfront Aquatic Habitat Restoration Strategy storymap

What Are The Data Telling Us?

TRCA monitoring team members measure sampled fish for length and weight

TRCA’s fisheries and aquatic habitat data provide a picture of the health and condition of the region’s aquatic ecosystem and how it responds to changes in land use and climate.

The decades of scientific data that TRCA has collected help to inform:

  • Watershed-based planning
  • Decisions related to land use changes
  • Restoration opportunities
  • Various development permit requirements
  • Legislation or policy change initiatives

TRCA shares the data with regional municipalities, consultants, research institutions, and other organizations at the federal and provincial levels.

Current Conditions: STREAMS

Based on current data, the health of fish communities in streams are considered in “fair condition” in seven of TRCA’s watersheds, and in “poor condition” in three watersheds. This is determined using the Index of Biotic Integrity (IBI).

Select the image below to view the Fish Communities in Streams dashboard.

TRCA Watershed Reporting Hub Fish Communities in Streams dashboard

Current Conditions: WATERFRONT

TRCA uses the percent piscivore biomass (PPB) to assess fish community health in the Lake Ontario nearshore. Piscivores are defined as fish-eating fish.

Data from 2014-2018 show that resident piscivores account for an average of 25% of biomass in sheltered embayments on the waterfront. This meets the target set by RAP for the Toronto and Region Area of Concern (AOC).

Select the image below to view the Nearshore Fish Communities dashboard.

TRCA Watershed Reporting Hub Nearshore Fish Communities dashboard

Continued aquatic habitat restoration efforts by TRCA and its partners — including those in support of the Don Mouth Naturalization and Port Lands Flood Protection Project — will continue to improve habitat conditions for local fish communities.

Visit TRCA’s Watershed & Ecosystems Reporting Hub


TRCA Watershed Planning and Ecosystem Science: