International Joint Commission
Lake Ontario – St. Lawrence Water Regulation Study
Year 2 Report - March 2003
Fish Sub-group ETWG – Burlington Report (DFO)
Part II
C.K. Minns, Susan Doka, Carolyn Bakelaar, Cindy Chu1
1
Great Lakes Laboratory for Fisheries and Aquatic Science, Fisheries & Oceans Canada
867 Lakeshore Rd., Burlington, Ontario L7R 4A6
During the second half of Year 2 we focussed on 3 areas:
1) Developing a plan and detailing the fish indicator assessment framework and its
integration across the complete area of study from Lake Ontario down through the St.
Lawrence River.
2) Expanding the Pike Population model
3) Wetland temperature and larval fish community monitoring and assessment.
This report will address progress within these three areas, building on the Year 2 interim report
submitted to the Study Board in November.
1. Fish Indicator Integration Modelling and Coordination
During the latter part of Year 2, considerable effort has gone into scoping and detailing
how the fish indicator assessment framework will be integrated across the complete area of study
from Lake Ontario down through the St. Lawrence River to beyond Trois Rivières. The fish subgroup (FSG) will need to generate consistent habitat and population assessment models for
application across all sub-areas of the LO-SL system. The fish group is currently working out the
details of how the habitat and population assessment models will be selected and which fish
guilds and species will be represented in the analyses. A more detailed analysis of how this
whole framework will be structured is contained in a recent MS Powerpoint presentation given at
both ETWG and Fish Sub-group workshops (February 2003)
Burlington FSG Year 2 Report (March 2003)
1
The development and analysis of the fish indicators integration framework has been of
great assistance in two additional areas: a) integration with other elements of the ETWG and
with other WGs, and b) linkage to the PFEG’s Shared Vision Model (SVM). For the former, it is
fairly clear how all the pieces fit together though it is still not apparent who will actually bring all
the necessary elements together in a format that is interoperable with the assessment models
developed within the ETWG; whether for wetland vegetation, birds and reptiles, or fish habitats
and populations. There will be a suite of GIS and simulation models necessary for the ETWG to
be able to evaluate and provide indicator measures for comparing alternate regulation schemes.
There is also continuing concern about how the required thermal characterization of the various
parts of the LO-SL system will be realized. This is an essential input for the fish sub-group as so
many life history events in fish are keyed to thermal regime. On the latter, it has become
increasingly clear that there is a disconnect between how elements of the ETWG will generate
metrics for comparing alternate regulation schemes and how the PFEG envisions integrating
various WG indicators in the form of interest satisfaction curves (ISCs) as functions of simple
hydrologic attributes. For the fish sub-group at least, it is clear that the results from the
assessment models are unlikely to be condensable into simple ISCs. Instead, it will be necessary
for separate models to be run for each component, generating output for different regime
schemes which can then be fed into the SVM.
A more detailed discussion of the indicators framework is available on a MS Powerpoint
presentation archived on the IJC ftp site:
ftp://ijcstudy@wtoftpa.on.ec.gc.ca/ijcstudy/ environment/meetings/
Fish PerformanceIndicators Framework Feb03 -97.ppt (see also attached CD ROM).
Burlington FSG Year 2 Report (March 2003)
2
2. Population dynamics of northern pike in response to habitat supply changes in the
Bay of Quinte, 1956-1999.
2.1. Objective

Link previous water level analyses and species-specific population model.

Compare population dynamics of northern pike under regulated and unregulated
water level regimes with and without egg stranding effects
2.2. Introduction
This study links two separate projects examining habitat dynamics in the Bay of Quinte,
Lake Ontario. The first examined the impacts of water level changes on the weighted suitable
area available for fishes in the upper and middle bays of the Bay of Quinte (Year 1 report). This
study improved the prototype model designed by Minns et al. (2002) to include GIS land
measurements of habitat area and habitat classifications when water levels rise above the
shoreline (74.2 m).
The second project involved the development of a Visual Basic application to estimate
the impact of habitat supply changes on the recruitment, growth and survival of a northern pike
population within a lake. The paper by Minns et al. (1996), describes a model simulating the
impact of habitat supply on northern pike, Esox lucius, in Hamilton Harbour, Lake Ontario, and
provided the basis for this work. This model uses dynamic changes in habitat supply through
time, such as water level changes, to produce several outputs of hatchling, fry, juvenile and adult
densities, as well as mean length at age and production to biomass ratios. Catastrophic stranding
events were included in the model where decreases in water levels during the egg/hatchling
period cause high egg/hatchling mortality because the eggs are exposed.
2.3. Methods
2.3.1. Linking of water levels and northern pike models
A water levels model was used to calculate weighted suitable areas (WSA) for spawning,
YOY and adult northern pike using a species classification of SPP10HI (a species that spawns at
10C and has a high preference for vegetated habitat) from 1956 to 1999. For each year, WSA at
10C, temperature and water level at which spawning occurs, was divided by the WSA at 20C,
Burlington FSG Year 2 Report (March 2003)
3
the upper limit of temperature at which hatching occurs, to produce estimates of water level
change during the egg development period. Hatchling survival was then multiplied by this value
to produce the impact of receding water levels on hatchling survival. In the model, this impact is
reflected in the number of fry at the beginning of the YOY stage. If there is no water level
change the hatchling survival is multiplied by one (no additional mortality is associated with
catastrophic stranding events).
A baseline simulation with no water level change was used to determine the
demographics of the equilibrium population in the Bay. To do this, the water levels model was
used to calculate the WSA for spawning, YOY and adult northern pike with no water level
changes, that is the elevation was set to 74.2m (IGLD85 for Kingston). These WSAs were
entered into a static version of the model and run for 100 years to produce an equilibrium
population. This population represented the starting population for the regulated and unregulated
scenarios.
The regulated water level data spanning 1956-1999 were available from a Canadian
Hydrographic Services (CHS) gauging station in Kingston. Unregulated data were available for
1956-1995 from David Fay (H&H TWG). The two water level scenarios were entered into the
model to produce WSAs for spawning, YOY and adult northern pike from 1956-1999. Two
simulations of the pike model using the calculated WSAs and the catastrophic stranding events
were then performed to determine the response of the northern pike population to water level
changes. The impacts of stranding events on the population were examined by running two
simulations with and without stranding events.
2.4. Results
The results described here represent a preliminary analysis of our work. They indicate
that the regulated scenario led to less variability in population recruitment (Figure 1). The
stranding events were clearly evident when hatch and fry densities were compared. Under the
unregulated regime the northern pike population severely declined in the mid-70’s (Figure 2).
Years with stranding events were also consistent with years of low P:B ratios. There was a
decrease in population size with water levels above 75.5 m. Stranding events caused more
variation and a decrease in the population size through time (Figure 3).
Burlington FSG Year 2 Report (March 2003)
4
8
a)
79.5
Hatchling density (#/m2)
7
78.5
6
77.5
5
4
76.5
3
75.5
2
74.5
1
0
1950
b)
1960
1970
1980
1990
2000
4
73.5
2010
79.5
78.5
3
Fry (#/m2)
77.5
2
76.5
75.5
1
74.5
0
1950
1960
1970
1980
1990
2000
73.5
2010
Year
Figure 1: a) Hatchling and b) fry densities (no./m2) of northern pike in the Bay of Quinte under regulated
() and unregulated () regimes. The circles represent regulated (●) and unregulated (○) water levels.
Burlington FSG Year 2 Report (March 2003)
5
Number of fish
Juvenile and Adult Density
79.5
160000
78.5
140000
120000
77.5
100000
76.5
80000
60000
75.5
40000
74.5
20000
0
1950
Age 1 and older/ha
Fish age 1 and older
180000
73.5
1960
1970
1980
1990
2000
2010
10.00
9.00
8.00
7.00
6.00
79.50
5.00
4.00
76.50
3.00
2.00
1.00
0.00
1950
78.50
77.50
75.50
74.50
1960
1970
1990
2000
73.50
2010
Year
Year
Biomass density
Production/Biomass
5.00
79.50
1.40
79.5
78.50
1.20
78.5
4.50
4.00
3.50
1.00
77.50
P/B
kg/ha
1980
3.00
2.50
76.50
2.00
1.50
1.00
77.5
0.80
76.5
0.60
75.50
0.40
74.50
0.20
75.5
74.5
0.50
0.00
1950
1960
1970
1980
1990
2000
73.50
2010
0.00
1950
1960
1970
1980
1990
2000
73.5
2010
Year
Year
Figure 2: Population dynamics of juvenile and adult northern pike in the Bay of Quinte under regulated () and unregulated () regimes with
stranding events. The circles represent regulated (●) and unregulated (○) water levels.
Burlington FSG Year 2 Report (March 2003)
6
a)
200000
80
79
160000
78
120000
77
80000
76
40000
b)
75
0
74
200000
80
79
160000
78
120000
77
80000
76
40000
75
0
1950
1960
1970
1980
1990
2000
74
2010
Year
Figure 3: Water level impacts on northern pike population size (age 1+) in the Bay of Quinte under
regulated () and unregulated () regimes. The circles represent regulated (●) and unregulated (○) water
levels. a) without catastrophic stranding events b) with catastrophic stranding events.
Burlington FSG Year 2 Report (March 2003)
7
3. An assessment of the temperature regime and larval fish communities in wetlands of
Lake Ontario, Canada
3.1. Introduction
Wetlands are considered to be important spawning and nursery areas for many Great
Lakes and St. Lawrence fish species. The Great Lakes Lab (Fisheries and Oceans in Burlington)
water levels and fisheries work, focussed on the Bay of Quinte, and its surrounding wetlands, as
an indicator of whole lake changes in fish population dynamics and fish community responses.
In the second year of the IJC-funded study, we have taken a field and empirically-based
approach to assessing four different types of wetlands and the associations between temperature
and habitat type with larval fish growth, abundance, diversity and timing of habitat usage. This
information is important to evaluating and validating the habitat supply-based approach we have
undertaken as a group in modelling efforts.
3.2. Methods
The hypotheses being tested by the field study centred around the larval fish community
and its characteristics, such as timing of spawning, larval growth rates, as well as selective
habitat use by species. The experimental design was constructed to test whether these
characteristics vary by:
1) wetland type (barrier beaches, drowned rivers, sheltered bays, exposed bays)
2) habitat type (emergent, submergent and open water)
3) time in late spring / early summer (May, June, July)
4) thermal regime
To test the latter hypothesis, a temperature survey of near shore, offshore and wetlands
(by habitat type) was also conducted in 2002. The map in Figure 1 shows the various larval and
thermal sampling sites. These wetlands belong to the suite of wetland sites in Lake Ontario that
were chosen by the ETWG for IJC study sites. Each wetland was divided into three different
habitat types based on aerial photography and the maximum vegetation coverage expected for
each embayment.
Burlington FSG Year 2 Report (March 2003)
8
Four temperature loggers were deployed from April until November in eight wetlands to
monitor thermal structure by habitat type. The loggers were arranged along a gradient of
vegetation: one in emergent vegetation, one in submergent vegetation, and two at shallow “openwater” sites (one open water logger was set as close as possible to the outflow or barrier to Lake
Ontario or the Bay of Quinte). Dataloggers were shaded with white PVC tubing and attached to
anchors at a maximum of 1 m water depth.
Larval fish were sampled once a month from May until July using a variety of gear types:
beach seine nets, gill nets and dip nets, depending on the appropriateness for the habitat.
Consistency of effort was attempted so that results were comparable between habitat types and
wetlands. All fish were counted and preserved in 95% ethanol. A maximum of 20 fish from
each species and habitat type were measured for tail length on each sampling date, depending on
the total number of fish captured. The otoliths from 10 of these fish were dissected and slidemounted for ageing and growth ring analysis to back-calculate hatch dates and average growth
rates.
Figure 1: Map of the Bay of Quinte and surrounding area, showing temperature logger sites (offshore
sites are green, near shore sites are purple, wetland sites are orange) and larval survey sites (orange
with black circles).
Burlington FSG Year 2 Report (March 2003)
9
3.3. Preliminary Results
Preliminary offshore thermal regimes for 2001 and larval fish community, species
richness, and use of wetland types and habitat types were presented in the interim report
provided to the IJC in October 2002. The findings presented here are data and analyses that have
been collected or analysed since the previous report.
3.3.1.
Larval Hatch Dates and Growth Rates
Hatch dates for different species for which otolith analysis was possible were slightly
overlapping but usually followed a temporal pattern (Figure 2). White suckers hatched first in
April. Yellow perch hatch dates varied the greatest from March until May, but mainly the latter
two months. Bluntnose minnows hatched from early May until early June, followed closely by
largemouth bass (mid May to mid June) and brook silversides (throughout June). Hatch dates
between wetlands did not vary much for most species with the exception of white suckers and
bluntnose minnows. White suckers in a barrier beach wetland (Huyck’s Bay) were hatched later
than white suckers in many different habitat types in a drowned river wetland (Hay Bay).
Bluntnose minnows were hatched earlier in Presqu’ile than in Huyck’s Bay.
White Sucker Silverside LMB
(May)
(July) (July)
PI-O2
HU-E
RC-S
RC-O1
PI-S
Yellow Perch
(May, *June)
RC-E
PI-O2
HU-S
*HU-O1
HU-O1
HU-E
HB-O1
PI-S
PI-S
HU-S
HU-O1
HU-O1
HB-O2
HB-O1
180
170
160
150
140
130
120
110
100
90
80
HB-E
Julian Date
Hatch Dates 2002
Bluntnose
(July/June)
Figure 2: Median hatch dates in Julian days; (error bars are ranges) for five different fish species plotted
by month of capture in 2002 and wetland/ habitat type.
Burlington FSG Year 2 Report (March 2003)
10
Hatch dates for species that were present in more than one habitat type within a wetland
were relatively consistent. However, hatch dates of yellow perch in different habitat types and
sampling times in Huyck’s Bay were quite variable. [Site Codes: HB = Hay Bay, HU = Huyck’s
Bay, PI = Presqu’ile Bay, RC = Robinson’s Cove; Habitat Codes: E = emergent vegetation, S =
submergent vegetation, O1 = open water close to vegetation, O2 = open water close to mouth.]
Results for the growth rates of the fish species were different than hatch dates results
(Figure 3). Growth rates increased from yellow perch, with the lowest growth rates, to bluntnose
minnow, white sucker, largemouth bass, and finally brook silversides, with the highest growth
rates. Growth rates between habitats were fairly consistent but some differences occurred
between wetlands. Relationships between wetland type and average daily growth rates may be
confounded by a correlation between hatch date and the predicted exponential growth rates.
However, the bias between hatch date and growth rate may just reflect species differences and
Exponential Growth Constants
0.14
0.12
0.10
0.08
0.06
0.04
White Sucker Silverside LMB
(May)
(July) (July)
Yellow Perch
(May + 1 June)
PI-O2
HU-E
RC-S
RC-O1
RC-E
PI-S
PI-O2
HU-S
HU-O1
HU-O1
HU-E
HB-O1
PI-S
PI-S
HU-S
HU-O1
HU-O1
HB-O2
0
HB-O1
0.02
HB-E
Growth Constant (`mm/mm/day)
not within species variability.
Bluntnose
(July/June)
Figure 3: Median growth rate constants (error bars are ranges) based on exponential growth curves. Data
was derived from otolith daily growth measurements for five different fish species plotted by month of
capture and wetland/habitat type.
Burlington FSG Year 2 Report (March 2003)
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3.3.2.
Thermal Regimes
Daily temperature averages were calculated from 30-min time series data. Comparisons
were made at different spatial scales: habitat zones (near shore, offshore, and wetland), wetland
and habitat types. A comparison of habitat zones revealed that offshore, 1m temperatures were
less variable, and slower to warm and cool throughout the ice free season than near shore or
wetland temperatures (Figure 4). Maximum temperatures in the offshore reached 23 C and 2728 C in near shore and wetland areas.
30
Temperature (C)
25
20
15
10
5
0
4-Apr
24-May
13-Jul
1-Sep
21-Oct
10-Dec
Date (2002)
Big Bay Nearshore
Conway Offshore Buoy
Big Sand Bay Barrier Beach
Figure 4: Daily temperature averages for three sites in the Bay of Quinte area.. All temperatures were
recorded at approximately 1 m water depths. Representative sites were chosen from near shore, offshore
and wetland habitat types.
Surprisingly, the barrier beach wetland was more variable and cooler than the near shore
exposed area. Therefore, the barrier beach may be more susceptible to lake temperatures than
the near shore area in the upper Bay of Quinte. A comparison of wetland types (open water
habitat only) revealed that temperatures were fairly consistent between wetlands in the spring
and fall, however summer thermal regimes differed (Figure 5). Most of the wetlands were quite
variable however there was a hierarchy of temperatures that was consistent. The barrier beach
wetland tended to be cooler on average with summer ranges of 20 – 27 C. The sheltered bay
Burlington FSG Year 2 Report (March 2003)
12
was slightly warmer and ranged from 21 – 27.5 C. The exposed wetland ranged from 22 – 27.5
C, while the warmest wetland, the drowned river, ranged from 22.5 – 29 C. At one point
during the summer a difference of approximately 7 C occurred between wetland locations.
Statistical analysis needs to determine whether these differences are due to wetland type or other
factors.
30
Temperature (C)
25
20
15
10
5
0
4-Apr
24-May
13-Jul
1-Sep
21-Oct
10-Dec
Date (2002)
Big Sand Bay Barrier Beach Open
Presqu’ile Bay Sheltered Bay Open
Hay Bay Drowned River Open
Robinson’s Cove Exposed Bay Open
Figure 5: Daily temperature averages for four wetland types in the Bay of Quinte area. All temperatures
were recorded at approximately 1 m water depths in open water habitat types. Representative wetlands
were chosen from barrier beach, sheltered bay, drowned river and exposed bay wetland types.
A comparison of habitat types within one wetland revealed subtle thermal differences in
vegetated areas (Figure 6). Emergent areas tended to be slightly warmer in spring and slightly
cooler than other areas in the summer and fall; up to a 3 C difference in August and September.
Differences between submergent areas, and open water areas, whether close to vegetation or
close to the mouth of the wetland, did not vary significantly. However, there was a gradient
from submergent vegetation to open water close to vegetation to open water close to the outlet
(i.e. submergent vegetation was either slightly warmer or cooler during peaks in warming or
Burlington FSG Year 2 Report (March 2003)
13
cooling trends). These trends may have more to do with the overall water depth in these areas
and statistical analysis is required to investigate these effects.
30
Temperature (C)
25
20
15
10
5
0
4-Apr
24-May
13-Jul
1-Sep
Date (2002)
Presquile Sheltered Emergent
Presquile Sheltered Open1
21-Oct
10-Dec
Presquile Sheltered Submergent
Presquile Sheltered Open2
Figure 6: Daily temperature averages for four habitat types in the Presqu’ile Bay wetland. All
temperatures were recorded at approximately 0.5 - 1 m water depths. Habitat types represent a gradient
from emergent vegetation, submergent vegetation, open water close to vegetation (Open1) and open water
close to the mouth or barrier of the wetland (Open2).
Burlington FSG Year 2 Report (March 2003)
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