Duffins Creek - Toronto and Region Conservation Authority

Duffins Creek
State of the Watershed Report
Aquatic Habitat and Species
June 2002
Other topics in this series for both the Duffins Creek and the Carruthers Creek include:
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Introduction
Study Area
Human Heritage
Greenspace, Trails and Recreation
Land Use
Air Quality
Climate
Surface Water Quality
Surface Water Quantity
Stormwater Management
Fluvial Geomorphology
Hydrogeology
Terrestrial Natural Heritage
Cover image: Rainbow trout.
Image credit: Bowen, Rae
This document is intended to be shared for non-commercial use.
We are promoting the electronic use of this document
to minimize the consumption of paper resources.
Toronto and Region Conservation, 5 Shoreham Drive, Downsview, Ontario M3N 1S4
Telephone: (416) 661-6600 • Fax: (416) 661-6898 • www.trca.on.ca
Table of Contents
Introduction to Aquatic Habitat and Species . . . . . . . . . . . . . . . . . . . .2
Riverine Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Lacustrine Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Estuarine Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Data Gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Tables and Figures
Table 1: Duffins Creek Cumulative Species List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Table 2: Duffins Creek Estuarine Marsh Cumulative Species List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Figure 1: An Index of Biological Integrity (IBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Figure 2: The 2000 Survey of 32 Sites in the Duffins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
1
Introduction to Aquatic
Habitat and Species
The health of the aquatic environment and the condition of the Duffins
Creek watershed are interconnected. This is because the aquatic
environment is directly affected by the quality and quantity of water
that flows over or through the land. The health of the aquatic habitat,
therefore, is an indicator of the health of the watershed.
The aquatic ecosystem is most often described as fish habitat since fish
communities are important resources, and as such, have a long history
of being used as indicators of aquatic ecosystem health. Aquatic habitat
is an integral part of the watershed’s ecosystem as it provides feeding,
breeding and rearing areas for resident and migratory fish and
invertebrate species. Within the watershed, aquatic habitats can be
divided into several different habitat categories, on the basis of
suitability for differentiating aquatic communities. These habitat
categories fall into three broad groups: riverine habitat (creeks and
rivers), lacustrine habitat (ponds and lakes) and estuarine habitat
(coastal marsh). In the following sections each habitat category is
identified and its significance, condition and any changes in condition
over time are described.
In 2000, a survey of fish communities and habitat was conducted to
provide a benchmark of our current knowledge of the watershed,
allowing for the identification of significant management issues as well
as gaps in our knowledge. A comprehensive analysis of the fish
community, aquatic habitat and a management plan for the aquatic
ecosystem will be completed early in 2002.
2
Riverine Habitat
Riverine habitat is found in rivers and creeks and
can be divided into coldwater and warmwater
habitat categories. The determinants of which
type of habitat exists in a particular location is a
result of a number of watershed and more local
level characteristics that affect fundamental
components of the habitat such as flow regime
and water temperature. The underlying geology,
in conjunction with riparian vegetation (i.e.
vegetation adjacent to streams) and land use,
produce the flow, water temperature, water quality
and associated aquatic community that we see
today. To understand the current health of fish
communities and their potential, it is necessary
to interpret these communities in the context of
these three factors.
Duffins Creek begins on the extensive sand and
gravel deposits of the Oak Ridges Moraine, which
forms the height of land in the northern part of
the watershed. To the south, the river crosses the
silt and clay till plains of glacial Lake Markham
and the slightly sandier Halton Till. Even farther
downstream, the creek crosses the sands and
gravels of the Lake Iroquois Shoreline and then
the silt and clay deposits of the old lake bed.
Below the deposits at the surface, the geology
alternates between the layers of lacustrine silt
and clay and fluvial deposits (i.e. associated with
streams or rivers) of sand and gravel. Many of
these deeper deposits reach the surface within the
deep valleys in the lower part of the watershed.
Each of the geologic deposits the creek drains
from or crosses, influences the characteristics of
the creek and thus the conditions that support
the aquatic communities. For further details refer
to the Hydrogeology chapter in this series.
The principal way in which the geology of the
watershed influences the fish community is by
moderating flow and water temperature. The
coarse surficial deposits encourage infiltration of
surface water across the landscape on which they
occur and thus reduce overland surface flows to
local streams. As a result, streams draining from
areas with coarse soils such as the Oak Ridges
Moraine or the Iroquois Shoreline tend to have less
frequent storm flow conditions and a significant
baseflow component due to groundwater
discharge. This combination results in an overall
more stable flow regime, which is characteristic
of streams in the Duffins Creek watershed.
Groundwater, a characteristic related to geology,
is another important factor that determines the
type of habitat and associated fish community
that can be sustained. Groundwater seeps or
flows into the creek where the aquifers (the
subsurface water-bearing deposits) are exposed.
The more groundwater discharge into the
watercourse, the greater the potential for
coldwater habitat. At 8-10°C year round,
groundwater is the source of cold water to
watercourses. The addition of warm flow from
parking lots or streets moderates the cold water
and reduces the area of coldwater habitat.
A good way to understand and measure whether
groundwater inputs are significant for aquatic
habitat is to examine the ratio of baseflow, a
measure of groundwater input, relative to the
annual flow. Research indicates that a ratio of
greater than 20 per cent groundwater discharge
to average annual flow is required to support
trout species. This occurs when roughly 20 per
cent of the total average annual flow is derived
from groundwater discharge into the creek.
Current estimates of base flows in the watershed
range from 50 per cent for Duffins Creek south
of Highway 2, to 37 per cent for the West
Duffins at Green River, 61 per cent for the East
Duffins above Pickering, and up to 50-60 per
cent for Ganatsekiagon Creek and Urfe Creek
(Eyles et al., 1997; Sibul et al., 1977).
Currently, Duffins Creek contains 380 kilometres
of watercourses. They are in relatively good
condition and are dominated by cold water
aquatic communities that include sculpin, trout
and numerous other fish species. Based on the
database of fish collections at the Royal Ontario
Museum’s Ichthyology Department, there have
been 45 riverine species of fish found in the
3
Duffins watershed (Table 1). Included in this list
are nine non-native species: sea lamprey, rainbow
trout, brown trout, coho salmon, chinook
salmon, alewife, goldfish, white perch and
common carp. Although non-native, the trout
and salmon species are considered by some to be
desirable from a recreation standpoint. At one
time trout and salmon were stocked in the creek;
presently only brown trout are still being
stocked. Atlantic salmon is the only known
extirpated species once found in Duffins Creek
(ODPD, 1956). The creek is currently being used
by the Ministry of Natural Resources to research
the habitat requirements and to evaluate the
feasibility of restoring Atlantic salmon to Lake
Ontario tributaries.
In the 2000 survey of the Duffins fish community,
28 species were encountered (Table 1). This
included three non-native species: chinook
salmon, rainbow trout and brown trout. The
fewer species found in the 2000 survey is likely a
reflection of the decreased extent of sampling,
the sites selected for sampling and possibly some
species losses. Coldwater streams in the upper
and middle reaches of the Duffins Creek
watershed provide habitat for species such as
brook trout, and slimy and mottled sculpin.
They also provide habitat for species at risk such
as redside dace (Clinostomus elongatus). In the
lower reaches of the west and east Duffins Creek
there is coldwater habitat that supports a
healthy, self-sustaining, rainbow trout population.
It is also likely that chinook and coho salmon
spawn successfully in the lower reaches. These
species of salmon and trout are separated from
the native brook trout populations by several instream barriers that prevent the upstream
movement of migratory species. Previous studies
have shown that the non-native salmon and
trout would out-compete the native brook trout
if their distributions were allowed to overlap.
4
According to the MNR District Fisheries
Management Plan 1989-2000, the Duffins
Creek watershed supports primarily brook and
brown trout in the headwaters and migratory
salmonids below Highway 7. Most of the
watershed is considered coldwater habitat with
the exception of Stouffville Creek, and the lower
Duffins below Highway 401. Stouffville Creek
once was coldwater habitat, but now it is
warmwater because of the presence of the
Stouffville reservoir, an online pond, and a lack of
woody riparian vegetation to shade the stream.
Conversely, the lower Duffins Creek is a natural
warmwater reach. This a consequence of the size
of the creek and the low quantities of
groundwater input into the creek at this location
in the watershed. The lower Duffins and
associated marsh provide good habitat for a
number of warmwater species such as smallmouth bass, northern pike and pumpkinseed.
The ecological health of a fish community can be
quantified through the calculation of an index of
biological integrity (IBI). The IBI figures
quantifies the ‘health’ of the fish community by
incorporating species richness, trophic balance,
the abundance of fish, and the presence of
indicator species into one index. This method was
first proposed by Karr (1981) and was further
modified and calibrated for southern Ontario
streams by Steedman (1988). Interestingly,
fisheries information from the Duffins watershed
was used by Steedman to calibrate the IBI for
southern Ontario streams. More importantly, he
found that many (77 per cent) locations in the
watershed had good to excellent fish
communities (Figure 1).
Surveys from the 1990s found similar conditions,
which is expected, because there have been few
changes in the watershed that would impact the
fish community. Overall, analysis of the watershed
from the 1950s to the 1990s has demonstrated a
general increase in the number of species and the
distribution of trout species (Jones and Guy,
1997). The 2000 survey of 32 sites in the Duffins
resulted in IBI scores from fair to excellent, with
a median score of good (Figure 2). This is a good
result given that a high percentage of the sites
scored good (53 per cent), three were excellent (9
per cent) and no sites were in poor condition or
had no fish present (Figure 2).
Table 1: Duffins Creek Cumulative Species List
COMMON NAME
LAMPREY FAMILY
American brook lamprey
northern brook lamprey5
sea lamprey1, 4
SALMON FAMILY
chinook salmon1
coho salmon1
rainbow trout1
Atlantic salmon3
brown trout6
brook trout
SUCKER FAMILY
white sucker
northern hog sucker
MINNOW FAMILY
goldfish2
northern redbelly dace
finescale dace
redside dace5
common carp2
brassy minnow
hornyhead chub
river chub
common shiner
spotfin shiner
sand shiner
common shiner x
creek chub
bluntnose minnow
fathead minnow
blacknose dace
longnose dace
creek chub
pearl dace
central stoneroller
SCIENTIFIC NAME
PRESENT IN 2000 SURVEY
Lampetra appendix
Ichthyomyzon fossor
Petromyzon marinus
ü
ü
Oncorhynchus tshawytscha
Oncorhynchus kisutch
Oncorhynchus mykiss
Salmo salar
Salmo trutta
Salvelinus fontinalis
ü
Catostomus commersoni
Hypentelium nigricans
ü
Carassius auratus
Phoxinus eos
Phoxinus neogaeus
Clinostomus elongatus
Cyprinus carpio
Hybognathus hankinsoni
Nocomis biguttatus
Nocomis micropogon
Notropis cornutus
Cyprinella spilopterus
Notropis stramineus
Luxilus cornutus x
Semotilus atromaculatus
Pimephales notatus
Pimephales promelas
Rhinichthys atratulus
Rhinichthys cataractae
Semotilus atromaculatus
Margariscus margarita
Campostoma anomalum
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
Continues on page six.
5
Table 1: Continued from page five
COMMON NAME
SCIENTIFIC NAME
CATFISH FAMILY
yellow bullhead
Ameiurus natalis
brown bullhead
Ictalurus nebulosus
4
channel catfish
Ictalurus punctatus
stonecat
Noturus flavus
FRESHWATER EEL FAMILY
American eel4
Anguilla rostra
STICKLEBACK FAMILY
brook stickleback
Culea inconstans
three-spine stickleback
Gosterosteus aculeatus
TEMPERATE BASS FAMILY
white perch1, 2
Morone americana
SUNFISH FAMILY
rock bass
Ambloplites rupestris
pumpkinseed
Lepomis gibbosus
smallmouth bass
Micropterus dolomieui
largemouth bass
Micropterus salmoides
PERCH FAMILY
yellow perch
Perca flavescens
rainbow darter
Etheostoma caeruleum
Iowa darter
Etheostoma exile
johnny darter
Etheostoma nigrum
4
logperch
Percina caproides
least darter
Etheostoma microperca
SCULPIN FAMILY
mottled sculpin
Cottus bairdi
slimy sculpin
Cottus cognatus
PRESENT IN 2000 SURVEY
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
1 introduced species; 2 naturalized species; 3 extirpated species; 4 found only in estuarine habitat;
5 Species at Risk, classified as “special concern” COSEWIC;
6 resident brown trout are naturalized while migratory brown trout are introduced.
6
Invertebrate samples are also used to assess
habitat condition and water quality because they
are a food source for many fish species and respond
quickly to environmental perturbations. In
general, mayflies (Ephemeroptera) and stoneflies
(Plecoptera) are considered the most sensitive
benthic taxa because they depend on clean and
well-oxygenated water. An overview of the
invertebrate communities in the Seaton lands
(Ganatsekiagon, Urfe, Whitevale and West Duffins
creeks) found that most sampling stations were
characterized as having a high proportion of
pollution-sensitive species (HBT AGRA, 1994).
The only sites where pollution-tolerant groups were
Figure 1:
An index of biological integrity (IBI), figures quantifies the ‘health’ of the fish community by incorporating
species richness, trophic balance and the abundance of fish, and the presence of indicator species. Data from
Steedman’s 1988 study.
7
found were in West Duffins Creek at the Brock
landfill and at Whitevale, yet in these samples there
were still many pollution-sensitive species. Recent
studies from headwater areas in the West Duffins
and East Duffins subwatersheds similarly found
high proportion of sensitive species (TRCA, 1999).
These results are a strong indicator that Duffins
Creek has a healthy invertebrate community.
The Duffins Creek watershed has experienced a
number of changes over the years. Historically the
watershed was dominated by vast forests that had
a tremendous influence on the hydrology of the
watershed. With settlement came deforestation
and a variety of agricultural practices that impacted
the system but, due in part to the large amounts
of groundwater discharging to the stream, the
sensitive species such as brook trout were not
lost. Other changes, such as transportation,
urbanization, water taking, barriers and ponds,
have impacted the watershed, however, their
extent within the watershed is limited and as
such the impact to aquatic habitat and species
has not been substantive.
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In the past 50 or so years the condition within
some areas of the watershed has been improving.
For example, in some of the headwater areas
where the glacial soils are poor for agriculture
and in the provincial Seaton and federal airport
lands, there has been significant amounts of
regeneration of table land and riparian forests.
This increase in forest cover has led to a
reduction in surface flows and a stabilization of
the overall flow regime, better aquatic habitat
and an overall improvement in the condition of
some fish communities. In fact, the fish community
in the West Duffins Creek has improved since
the 1950s. In the 1950s first extensive fish
survey of the Duffins Creek watershed, sensitive
species such as brook trout and sculpin were
largely restricted to the headwater areas. Since
the 1950s the conditions have improved and
these species have extended their range to other
areas (Jones and Guy, 1997). With many areas
still requiring woody riparian vegetation, there is
room for further improvements in the fish
community and the aquatic system in general.
Improvements have not occurred with respect to
the mitigation or removal of in-stream barriers.
Structures that act as barriers include dams,
weirs, level crossings and some culverts. Many of
the large structures were created historically to
produce power for grist or saw mills. In more
recent years they were built to create recreational
ponds. Other barriers may include structures that
increase water velocities. These velocity barriers
may be created through incorrectly sized culverts
that increase water velocities to the point where
they do not allow for fish passage. Generally
these structures serve as barriers to migratory
fish movement upstream and may bar fish access
to important spawning or rearing areas. Barriers
also fragment resident fish populations by
limiting their movement within the watershed.
The presence of barriers in the watershed can
have a positive or negative effect. In the Duffins,
some of these barriers are helping to protect
native brook trout populations from migratory
salmonids or prevent sea lamprey from accessing
potential areas. Other barriers fragment brook
trout habitat, limiting access to summer refugia
or fall spawning habitat. Managing the effects of
instream barriers is an important issue that must
be addressed in the development of a watershed
fisheries management plan.
Future land use activities and developments
within the watershed should address the
decreased ability of urbanized areas to infiltrate
water and their ability to speed up the movement
of water towards the creek. These alter the
hydrologic cycle toward less groundwater
infiltration and greater surface runoff. If the
changes in the surface and groundwater regimes
are large enough, they can significantly impact
both coldwater and warmwater habitat, making
preservation of the current regime important.
Figure 2:
The 2000 survey of 32 sites in the Duffins resulted in IBI scores from fair to excellent, with a median
score of good.
9
Lacustrine
Habitat
Lacustrine habitat is characterized by the
presence of standing water. Two types of
lacustrine habitat found in the Duffins Creek
watershed are online and offline ponds and lakes.
In total, these ponds and lakes cover an area of
more than 2.5 km2 in the watershed. There are
approximately 172 online ponds in the watershed
averaging 0.5 ha in size. These ponds are directly
connected to the creek with the creek passing
directly through the waterbody. Offline ponds
may be completely isolated from the creek with
little or no connection, or indirectly connected
through a pipe that directs some flow from the
creek to the pond. There are approximately 746
offline ponds in the watershed.
Ponds can also be created through a variety of
acts of nature. Many ponds are created as a result
of beaver building dams with wood and other
debris. These structures are generally not a
concern as they are natural and tend to be
transient in nature. Ponds may also be formed
through the normal migration of the creek, which
can create oxbow lakes or ponds. Kettle lakes
were also formed by nature through the melting
of trapped ice on the Oak Ridges Moraine during
the last ice age. Kettle lakes are common in the
headwater areas, with the greatest density found
in the Township of Uxbridge.
10
There are a large number of human-made ponds
in the watershed that were created to power mills,
water livestock or to provide aesthetic or recreational
values. Many of these and other ponds are capable
of supporting small populations of brook trout.
Some ponds were created to enhance brook trout
populations. One such pond is the 8 ha Secord
Pond located in the upper west Duffins Creek
southeast of Goodwood. Although there was
recreational benefit from the creation of this pond,
it also prevented trout from accessing spawning
habitat on significant groundwater discharge zones
upstream/downstream of the pond. Most of the
kettle lakes and ponds in the watershed are much
smaller and support correspondingly smaller fish
and fish communities.
Online ponds are depositional areas that
accumulate sediments and tend to evolve into
wetlands and eventually uplands over time. The
accumulated sediments can pose a risk to
downstream fish communities if released from
the pond or reservoir. Online ponds may also
contribute to warming of the creek because large
ponds and lakes, such as the Stouffville Reservoir,
slow the water and allow the surface temperatures
to rise. This results in increased temperatures
downstream and may make the habitat less
suitable for coldwater species. In some cases this
warming effect can be mitigated if the water is
released from the bottom of the pond where it is
usually cooler.
Estuarine Habitat
The coastal marsh located at the confluence of
Duffins Creek and Lake Ontario covers 41 ha.
This area is of critical importance to many fish
species. A total of 27 species have been recorded
from the marsh area (Table 2). Species found here
include creek species, but also typically lake
resident species such as northern pike, yellow
perch, gizzard shad, alewife, white bass and
white perch. Of importance is that the area
provides spawning and rearing habitat for 18 of
these species. In total, 81 per cent of the 27
species found in the marsh area use it for either
spawning or rearing purposes (Stephenson, 1988).
Four species found in the marsh – the common
carp, alewife, rainbow trout and white perch –
are introduced species.
This area is designated as an environmentally
significant area (ESA), an area of natural and
scientific interest (ANSI), as well as a provincially
significant wetland because of its importance to
fish, plants and other wildlife species. There are
several attributes that make the marsh an
important area for fish. First, this area serves as a
transition zone between the creek and lake. The
marsh is affected by changes in the watershed as
well as the water levels that occur in the lake.
This transition provides ideal spawning and
rearing conditions. Second, the marsh is a very
productive area. This occurs because of the low
gradient that serves as a depositional area for
upstream sediments. The low gradient in this
part of the watershed and sediments create a
wide flood plain that is seasonally inundated
with water. The sediments also provide nutrients
to the system, while the nutrients support a
dense weed growth that provide excellent cover
for growing fish and also provide a resource base/
food source for the growing fish and prey.
These estuarine marshes are under threat
throughout the Great Lakes region (Stephenson,
1988). Given the marsh’s importance to the fish
population in the creek as well as to lake fish species,
it is of critical importance to protect this area.
Data gaps
One non-specific management concern is to fill
data gaps. The current aquatic information on
Duffins Creek is by no means complete and there
are a number of data gaps that will influence our
ability to effectively manage the fisheries
resources and track changes over time. These
gaps include the following:
• A lack of a good hydrology model for baseflow
and frequent flows in the watershed.
Management of the flow regime within the
watershed is critical to the protection of its
resources, especially the aquatic ecosystem.
Creation of a continuous simulation model to
allow prediction of baseflows and frequent flows
is critical to developing an understanding of
what will be necessary to protect the watershed.
• Understanding and managing angling
pressure to determine if it is impacting fish
communities is critical. To answer this question,
spring and summer creek surveys are needed
to quantify angling pressure.
Table 2: Duffins Creek Estuarine
Marsh Cumulative Species List
COMMON NAME
alewife
gizzard shad
rainbow trout
rainbow smelt
northern pike
white sucker
carp
golden shiner
emerald shiner
common shiner
spottail shiner
spotfin shiner
bluntnose minnow
fathead minnow
blacknose dace
longnose dace
creek chub
brown bullhead
white perch
white bass
rock bass
pumpkinseed
smallmouth bass
largemouth bass
yellow perch
johnny darter
logperch
Source: TRCA, OMNR
SCIENTIFIC NAME
Alosa pseudoharengus
Dorosoma cepedianum
Oncorhynchus mykiss
Osmerus mordax
Esox lucius
Catostomus commersoni
Cyprinus carpio
Notemigonus crysoleucas
Notropis antherinoides
Luxilus cornutus
Notropis hudsonius
Notropis spilopterus
Pimephales notatus
Pimephales promelas
Rhinichthys atratulus
Rhinichthys cataractae
Semotilus atromaculatus
Ameiurus nebulosus
Moreone americana
Morone chrysops
Ambloplites rupestris
Lepomis gibbosus
Micopterus dolomieui
Micropterus salmoides
Perca flaveseens
Etheostoma nigrum
Percina caprodes
11
Summary
Of all the watersheds within the TRCA jurisdiction, Duffins
Creek has one of the most intact fish communities and may have
the potential for successful reintroduction of Atlantic salmon.
Since initial settlement, many riparian areas that were once
deforested have been left to regenerate. Much of this
regeneration was not planned but occurred ostensibly because
many areas in the watershed were unsuitable for agriculture and
were subsequently abandoned. Now, because there has been
little development in the mid- to upper reaches, the stream
community is in relatively good condition. Nevertheless, there
are several measures that can be implemented to better manage
the aquatic ecosystem including improving fish passage where
appropriate, planting woody riparian vegetation and
reforestation of table lands.
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References
Eyles, N., J. Boyce and R. Gerber, 1997. Hydrogeological Study of the North
Pickering Development Corporation Lands and the Duffins Creek Watershed.
Prepared for the North Pickering Development Corporation. (CD Rom
available from TRCA)
HBT AGRA Ltd., 1994. Seaton Lands as a Natural Ecosystem. Report to the
Seaton Interim Planning Team. 139pp and Appendix.
Jones, M. and M. Guy, 1997. Seaton Lands Stream Assessment: Aquatic Habitat
and Fisheries. Prepared for the North Pickering Development
Corporation. (CD Rom available from TRCA)
Karr, J.R., 1981. Assessment of Biotic Integrity Using Fish Communities.
Fisheries 6:21-27.
Ontario Department of Planning and Development (ODPD), 1956. Rouge,
Duffin, Highland, Petticoat Valley Conservation Report. Toronto, Ontario.
Sibul, U., K.T. Wong and D. Vallery, 1977. Groundwater Resources of the
Duffins Creek-Rouge River Drainage Basins. Water Resources Report: 8.
Ministry of the Environment, Water Resources Branch. Toronto,
Ontario.
Steedman, R.J., 1988. Modification and Assessment of an Index of Biotic
Integrity to Quantify Streams in Southern Ontario. Canadian Journal of
Fisheries and Aquatic Science 54: 492- 501.
Stephenson, T., 1988. Fish Utilization of Toronto Area Costal Marsh Areas.
M.Sc. Thesis, Department of Zoology, University of Toronto, Toronto
ON, Canada. 222p.
Toronto and Region Conservation Authority (TRCA), 1999. Glen Major
Complex Management Plan: Phase 1-Background Report. Downsview,
Ontario.
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