Existing Conditions – Fish

Fish

The Toronto and Region Conservation Authority has been monitoring waterfront fish communities since 1982, with continuous programs since 1989. Electrofishing is the principal method, supplemented by seine and index netting.

Over the past two decades, the monitoring program has demonstrated gradual improvements in the fish communities, as measured by the proportions of native and introduced species, the age structure of the populations, and the ratio of predators to forage species. For example there are downward trends in some of the introduced species, such as alewife and carp, and increases in many of the native species including the predatory northern pike and forage species like the common, spottail and emerald shiners and bluntnose minnow.A

Waterfront Fish Communities

The Toronto and Region Conservation Authority has been monitoring waterfront fish communities since 1982, with continuous programs since 1989. Electrofishing is the principal method, supplemented by seine and index netting. Insert one photo of a monitoring boat.

Over the past two decades, the monitoring program has demonstrated gradual improvements in the fish communities, as measured by the proportions of native and introduced species, the age structure of the populations, and the ratio of predators to forage species. For example there are downward trends in some of the introduced species, such as alewife and carp, and increases in many of the native species including the predatory northern pike and forage species like the common, spottail and emerald shiners and bluntnose minnow.

Table A: Toronto Waterfront fish communities by biomass and abundance sampled during July from 1998-2002

95% of catch by abundance 95% of catch by biomass
Alewife 45% White Sucker 38.7%
White Sucker 16.4% Common Carp 38.2%
Pumpkinseed 10% Gizzard Shad 4.5%
Spottail Shiner 5.2% Northern Pike 4.3%
Emerald Shiner 4.5% Freshwater Drum 2.8%
Rock Bass 2.4% Alewife 2.5%
Rainbow Smelt 2.1% Brown Bullhead 1.6%
Yellow Perch 1.8% Yellow Perch 1.3%
Common Shiner 1.7% Rock Bass 1.3%
Gizzard Shad 1.6%
Common Carp 1.6%
Bluntnose Minnow 1.3%
Brown Bullhead 1.2%

The high numbers of alewife reflect the eutrophic conditions that have existed over the last few decades. White sucker and carp dominate the biomass. White sucker are a good forage food for predator species, so it would be beneficial to shift the population to greater numbers of smaller fish.

Alewife

Species trends along the waterfront show a gradual decline in the abundance and biomass of alewife from 1989-2002, probably due to recent reductions in nutrient loadings to the Lake.


Carp

The abundance of carp is declining slowly, but their biomass is increasing, reflecting smaller numbers of larger, older fish and a probably decrease in spawning success. It would be beneficial to encourage this trend and reduce the carp population overall.


Pumpkinseed

The abundance of pumpkinseed is increasing, while biomass has decreased, reflecting a healthy trend towards a larger number of smaller fish.


Northern Pike

The abundance and biomass of northern pike have been increasing gradually, most likely because of increasing submerged vegetation and habitat restoration projects. However the age structure of the population is weighted towards larger, more mature individuals. It would be desirable to shift this structure to a greater variety of sizes and ages.


Largemouth Bass

Largemouth bass show a dramatic increase in both abundance and biomass, probably because they are supported by the increasing amounts of emergent vegetation along much of the waterfront providing shelter and sources of food for juvenile fish.


Estuaries

Estuaries are the lower reaches of a river or streams that are influenced by lake levels (eg the Rouge River from Lake Ontario to Highway 401). Their habitats are essential to the function of the entire waterfront. Healthy estuaries are typically very productive, because they hold nutrients from the watersheds and provide stable thermal conditions. Backwater lagoons are principal areas of production and provide a variety of habitats, including spawning. Estuaries also represent a physical connection between the lake and watershed for species that inhabit the open waters of the Lake as well as riverine habitats.

Don River

Humber River

 

Highland Creek

The environmental quality of the estuaries along the Toronto waterfront varies dramatically. The longer estuaries, such as the Rouge River and Highland Creek, still have functional estuarine habitats, albeit degraded. Mimico Creek estuary has benefited from restoration projects in recent years and is showing some signs of recovery. Etobicoke Creek estuary has been considerably shortened and degraded, with little bottom structure or vegetation. The Don River estuary is the most severely altered, with very limited aquatic habitat.

Estuary – Area influenced by lake levels

  • Estuary/Wetland Relationship
    • A conduit of nutrients
      The river provides a conduit of nutrients, stable thermal conditions and connection between the lake and the watershed.
    • Backwater lagoons
      Backwater lagoons are principal areas of biological production and provide a variety of essential habitats
    • River discharge
      River discharge areas are commonly very productive littoral
    • Essential habitat
      The wetland estuary complex is essential habitat for the entire waterfront

 

Waterfront Fish Communities revisited

Although the estuarine fish communities are dominated by alewife and white sucker, shiners (spottail and emerald) and other minnows provide an important forage base in the healthier estuaries. Northern pike, freshwater drum and smallmouth bass have fairly high biomass in the Toronto estuaries, despite the predominance of carp and white sucker.

Table B: Toronto Estuary fish communities by biomass and abundance sampled during July from 1998-2002

95% of catch by abundance 95% of catch by biomass
Alewife 44.8% Common Carp 66%
White Sucker 14.1% White Sucker 17.2%
Spottail Shiner 8% Northern Pike 2.7%
Emerald Shiner 6.1% Freshwater Drum 2.6%
Brown Bullhead 3.4% Smallmouth Bass 2.5%
Common Shiner 3.2% Alewife 2.5%
Pumpkinseed 3.1% Brown Bullhead 2.3%
Common Carp 2.9%
Gizzard Shad 2.8%
Smallmouth Bass 2.5%
Rainbow Smelt 2.1%
Bluntnose Minnow 2%
Yellow Perch 1.1%

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Coastal Wetlands

Coastal wetlands are found in many of the estuaries (notable exceptions are Etobicoke Creek and the Don River which have been channelized) and in sheltered embayments such as Tommy Thompson Park lagoons, the Inner Harbour and most of the lakefill parks.

Rouge River

Triangle Pond-Tommy Thompson Park

 

Mimico Creek

 

At present, approximately 51% of the coastal wetland fish community is comprised of alewife and emerald shiner (an important forage species). Carp and white sucker represent nearly 62% of the biomass. Largemouth bass represent only 1.6% of the abundance and 2.3% of the biomass, but show promising trends towards increases in both. Other notable species are northern pike and bowfin, indicating improvements in environmental quality.

Table C: Toronto Coastal Wetlands fish communities by biomass and abundance sampled during July from 1998-2002

95% of catch by abundance 95% of catch by biomass
Alewife 28.6% Common Carp 35.0%
Emerald Shiner 22.4% White Sucker 26.9%
Pumpkinseed 8.7% Gizzard Shad 10.9%
White Sucker 5.7% Northern Pike 8.1%
Common Shiner 5.7% Brown Bullhead 4.5%
Gizzard Shad 5.1% Bowfin 4.5%
Spottail Shiner 4.4% Largemouth Bass 2.3%
Brown Bullhead 4.2% Alewife 1.9%
Bluntnose Minnow 3.3% Freshwater Drum 1.4%
Rainbow Smelt 2.5%
Largemouth Bass 1.6%
Yellow Perch 1.6%
Common Carp 1.4%

Sheltered Embayments

Sheltered embayments in harbour areas, the Toronto Islands and lakefill parks provide thermal refuge as well as a variety of shoreline conditions and configurations with significant areas of aquatic vegetation. Water currents that occur between the sheltered embayments and the open waters of the lake attract and hold forage fish, providing a concentrated area for feeding by predators.

Bluffer’s Park

Spadina Quay – Toronto Inner Harbour

Embayment B Wetland – Tommy Thompson Park

  • Thermal Habitat
  • Significant areas of aquatic vegetation
  • Variety of shoreline conditions and configuration
  • Important centers of biological organization

Tommy Thompson Park

In the sheltered embayments, alewife is nearly 45% of the abundance, with fairly high numbers of white sucker and pumpkinseed. 74% of the biomass is white suckers and carp. There is a good forage component. The relatively small number of large carp suggests that there is little ongoing reproduction. The presence of largemouth bass is a reflection of abundant submerged aquatic plants. The sporadic occurrences of walleye are a good indicator of appropriate conditions for cool water fish including high primary productivity for the young to feed.

Table D: Toronto Sheltered Embayments fish communities by biomass and abundance sampled during July from 1998-2002

95% of catch by abundance 95% of catch by biomass
Alewife 44.7% White Sucker 43.7%
White Sucker 16.1% Common Carp 30.6%
Pumpkinseed 11.4% Northern Pike 5.5%
Spottail Shiner 5.3% Gizzard Shad 4.5%
Emerald Shiner 3.7% Alewife 2.7%
Rock Bass 3.2% Freshwater Drum 2.5%
Yellow Perch 2.4% Brown Bullhead 1.9%
Bluntnose Minnow 1.9% Rock Bass 1.5%
Rainbow Smelt 1.8% Yellow Perch 1.5%
Gizzard Shad 1.5% Pumpkinseed 1.3%
Brown Bullhead 1.4%
Common Carp 1.3%
Largemouth Bass 1.2%

Sheltered Embayments

Open coast habitats occur across most of the Toronto waterfront. In sharp contrast to the sheltered embayments, coastal wetlands and estuaries described above, the open coast has much colder water, and is exposed to extensive wind and wave action, resulting in a relatively hostile environment for littoral vegetation and animals. Hypolimnetic upwellings of cold sub-surface waters are common, resulting in temperature fluctuations of as much as 12 Celsius degrees that reduce survival of warmwater fish in these areas.

Port Union Shoreline

Western Beaches

Sylvan Ave/South Marine Drive

 

The open coast habitats with bedrock or cobble/boulder substrates and convex profiles are particularly suited to coldwater fish, since species such as lake trout and lake whitefish typically rely on these substrates with nearby steep drop-offs for successful reproduction. Headlands, where the greatest aggregations of boulders occur, probably provide the best quality coldwater spawning habitats. Open coast habitats associated with concave profiles (eg Scarborough Bluffs) and the shifting lakebeds associated with dynamic beaches are best suited to species which broadcast their eggs in water, such as lake herring, emerald shiner, alewife and smelt. These fish provide an important forage base for other species, including most sports fish. Many fish for example the salmon species; also use open coast habitats as travel corridors during their seasonal movements.

Open coast habitats can be classified into four types:

  1. River discharge areas/barrier beaches
  2. Headland/groyne beaches
  3. Unprotected shorelines
  4. Walls and revetments

Most of the open coast habitat along the Toronto waterfront has been degraded by human interventions. In recent years, the design of shoreline management works has evolved to incorporate more ecological functions. The open coast has the highest abundance of alewife at about 62% of the catch. American eel, salmon and trout are found in the cooler waters of the open coast. The occurrence of carp in the open coast will be reduced if measures can be successfully taken to reduce their reproduction in the wetlands and embayments. Nearshore benthos can be improved by modifying the substrate, for example by replacing some of the 1 million cu metres of rocky materials removed historically from the Toronto shoreline. Another important factor in the open coast is the general lack of debris such as large timbers and woody materials from the upstream watersheds. However the Highland and Rouge estuaries still have many logs that have washed down the rivers and are now embedded in the shoreline.

Table E: Toronto Open Coast fish communities by biomass and abundance sampled during July from 1998-2002

95% of catch by abundance 95% of catch by biomass
Alewife 61.7% White Sucker 45.7%
White Sucker 13% Common Carp 28.9%
Emerald Shiner 8.7% Alewife 7.3%
Spottail Shiner 5.2% Brown Trout 6%
Rainbow Smelt 3.5% Smallmouth Bass 2.1%
Threespine Stickleback 1.1% Freshwater Drum 1.6%
Smallmouth Bass 0.9% American Eel 1.5%
Pumpkinseed 0.6% Lake Trout 1.5%
Common Carp 0.6% Rainbow Trout 0.9%

Open Coast

Open coast habitats occur across most of the Toronto waterfront. In sharp contrast to the sheltered embayments, coastal wetlands and estuaries described above, the open coast has much colder water, and is exposed to extensive wind and wave action, resulting in a relatively hostile environment for littoral vegetation and animals. Hypolimnetic upwellings of cold sub-surface waters are common, resulting in temperature fluctuations of as much as 12 Celsius degrees that reduce survival of warmwater fish in these areas.

Port Union Shoreline

Western Beaches

Sylvan Ave/South Marine Drive

The open coast habitats with bedrock or cobble/boulder substrates and convex profiles are particularly suited to coldwater fish, since species such as lake trout and lake whitefish typically rely on these substrates with nearby steep drop-offs for successful reproduction. Headlands, where the greatest aggregations of boulders occur, probably provide the best quality coldwater spawning habitats. Open coast habitats associated with concave profiles (eg Scarborough Bluffs) and the shifting lakebeds associated with dynamic beaches are best suited to species which broadcast their eggs in water, such as lake herring, emerald shiner, alewife and smelt. These fish provide an important forage base for other species, including most sports fish. Many fish for example the salmon species; also use open coast habitats as travel corridors during their seasonal movements.

Monitoring Programs

The monitoring program also provides information about the fish that are commonly found during the summer months in the four major habitat types that occur on the Toronto waterfront. The coastal wetlands, estuaries and sheltered embayments have quite similar assemblages of species whereas the open coast has a somewhat different fish community.

These four habitat types, along with tributary streams, contain biophysical features that are essential for self-organization and provide special locales where the highest percentages of reproduction and predation occur. These locales are considered to be centres of ecological organization, in contrast to the open lake.

Whenever centres of organization are degraded or obliterated, more ecological damage occurs than just the loss of function at a specific site. Without adequate and sufficient habitat for reproduction, species and aquatic communities suffer because the transfer of genetic information is thwarted. When feeding sites are detrimentally affected, large species do not grow and mature, so that energy transfers are reduced to recycling in large populations of very small, short-lived animals usually associated with open water. The overall effect is a decrease in the self-regulatory capacity of the biotic systems, an effect that is ecologically and spatially manifested well beyond the location of the actual centre of ecological organization.

It is also important to recognize that many species of fish use different habitats depending on the season and/or weather conditions. For example; estuaries are used by coldwater species (such as rainbow and brown trout, white sucker and Atlantic salmon) when they move from the cold waters of the open lake to migrate upstream for spawning. Another example is the thermal corridors of warmer water that provide suitable conditions for many fish to migrate along the open coast between the estuaries, wetlands and sheltered embayments.

The following sections provide information about current fish communities in each of the four key waterfront habitat types: estuaries, coastal wetlands, sheltered embayments and open coast.