Review of potential

ecological impacts from winter drawdown scenarios

in Lake St. Lawrence

April 24, 2020

Report prepared for:

International Joint Commission Lake Ontario – St. Lawrence River Board and Great Lakes – St. Lawrence River Adaptive Management Committee

ACKNOWLEDGEMENTS

The authors wish to thank the members of the IJC’s International Lake Ontario-St. Lawrence River Board and Great Lakes – St. Lawrence River Adaptive Management (GLAM) Committee for their input and guidance for this report. Bathymetry data for Lake St. Lawrence was provided by the National Hydrological Service of Environment and Climate Change Canada. Subject matter experts at the NYSDEC, OMNRF, DFO, and SRMT are thanks for their input on fish occurrences for Lake St. Lawrence. Staff at the River Institute are thanked for project support and management. Funding for this project was provided by the IJC’s International Watersheds Initiative (IWI) and the River Institute

CONTRACTOR AUTHORS

Matt Windle, M. Sc. – River Institute – Lead Author Louis Savard, C. Tech, PMP – River Institute – Project Manager Mark MacDougall, M. Sc., C.E.T. – River Institute Mary Ann Perron, Ph. D. – River Institute Matthew MacMillan – River Institute

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Contents

ACKNOWLEDGEMENTS ...... ii LIST OF TABLES ...... iv LIST OF FIGURES ...... v LIST OF APPENDICES ...... vi EXECUTIVE SUMMARY ...... 1 INTRODUCTION ...... 2 METHODS ...... 3 Study area ...... 3 Literature review ...... 4 GIS analyses of water level scenarios ...... 5 RESULTS & DISCUSSION ...... 6 Literature review ...... 6 Benthic invertebrates ...... 7 Fish ...... 8 Herpetofauna ...... 8 Aquatic mammals ...... 9 GIS analyses ...... 10 Assessment of ecological vulnerability ...... 11 CONCLUSIONS AND RECOMMENDATIONS ...... 12 REFERENCES ...... 14 TABLES ...... 20 FIGURES ...... 25 APPENDIX A ...... 34 APPENDIX B ...... 37 APPENDIX C ...... 39 APPENDIX D ...... 42 APPENDIX E ...... 49 APPENDIX F ...... 50 APPENDIX G ...... 53 APPENDIX H ...... 54

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LIST OF TABLES

Table 1. Context of modelled winter water level stage scenarios.

Table 2. Coordinates of water gauge stations in Lake St. Lawrence, with corresponding water stage levels (elevation, m) under six different scenarios.

Table 3. Modelled predictions of the amount of riverbed in Lake St. Lawrence (LSL) that would be inundated or exposed under six different winter water level scenarios.

Table 4. The areas of contiguous river (km2) and isolated pools of water (km2), and the number of isolated pools predicted under six modelled scenarios of water levels in Lake St. Lawrence.

Table 5. List of taxa that may be vulnerable to extreme winter drawdown scenarios in LSL.

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LIST OF FIGURES

Figure 1. Study area with locations of water level gauges in Lake St. Lawrence.

Figure 2. Historical seasonal water levels fluctuations in Lake St. Lawrence.

Figure 3. Bathymetric digital elevation model of Lake St. Lawrence.

Figure 4. Modelled output of Lake St. Lawrence under six winter water level scenarios.

Figure 5. Example of modelled output of inundated and exposed areas of Lake St. Lawrence under Scenario 4 water levels.

Figure 6. Modelled output of Lake St. Lawrence water level scenarios near Ingleside, Ontario.

Figure 7. Predicted number of isolated pools of water of various size classes created under six different winter water level scenarios.

Figure 8. Predicted depth (m) of isolated pools created under six different winter water level scenarios.

Figure 9. Cross-validation of modelled output of Scenario 1 water levels with remotely sensed UAV imagery capture at the equivalent water level on October 1, 2018.

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LIST OF APPENDICES

APPENDIX A. List of benthic invertebrates occurring in Lake St. Lawrence, with references.

APPENDIX B. Overwintering habitat requirements of benthic invertebrates inhabiting Lake St. Lawrence, with references.

APPENDIX C. List of fish species occurring in Lake St. Lawrence. See Methods section for a description of data sources.

APPENDIX D. Overwintering habitat requirements of fish species inhabiting Lake St. Lawrence, with references.

APPENDIX E. List of reptile and amphibian species occurring in Lake St. Lawrence.

APPENDIX F. Overwintering habitat requirements of adult reptile and amphibian species inhabiting Lake St. Lawrence, with references.

APPENDIX G. List of aquatic mammals occurring in Lake St. Lawrence, with references.

APPENDIX H. Overwintering habitat requirements of aquatic mammal species inhabiting Lake St. Lawrence, with references.

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EXECUTIVE SUMMARY

Ice effects and winter operations of the Moses-Saunders Dam (St. Lawrence River), in accordance with direction from the IJC’s International Lake Ontario – St. Lawrence River Board (ILOSLRB), have historically resulted in a large drawdown in water levels on Lake St. Lawrence (LSL; the forebay for the hydropower structures) during winter months. Given ongoing high water levels on Lake Ontario and the upper St. Lawrence River through much of 2019 and into early 2020, the ILOSLRB was granted extended deviation authority by the IJC to further increase outflows during the winter months in 2020 in an effort to reduce the flood risk in 2020. Such an increase in outflows could result in further water level drawdown on LSL during the winter months. A similar strategy may be considered in future high water years in an effort to maximize Lake Ontario outflows. The goal of this project was to fill a knowledge gap regarding the potential ecological impacts of greater than normal winter drawdown through a literature review, to conduct a GIS-based analysis of lower water level scenarios in LSL, and to identify vulnerable species.

A GIS analysis of 6 winter drawdown scenarios was completed, representing a gradient of moderate to extreme water level decreases for LSL (up to 2.33 m). Comparisons were made between typical winter drawdown levels from scenarios 1 to 3 and hypothetical extreme drawdown levels from scenarios 4 to 6. Modelled outputs suggested an increase in exposed riverbed of 16% to 80% from scenarios 4 to 6 compared to the typical minimum winter baseline of Scenario 3, with the majority of exposed riverbed occurring in large shallow embayments of LSL. The GIS analysis also predicted the number of isolated pools that would be formed under drawdown scenarios, which could result in strandings of aquatic biota. Small to moderate increases (6-17%) in the number of isolated pools were predicted from scenarios 4 to 6 compared to the Scenario 3 baseline, with a maximum of 238 isolated pools predicted for Scenario 5. Almost all isolated pools were predicted to have depths less than 20 cm. Cross- validation of predicted exposed riverbed areas with UAV imagery collected at matching water stage levels revealed a close match, supporting modelled outputs.

A compilation of known aquatic species inhabiting LSL revealed a diverse assemblage of benthic invertebrates, fishes, amphibians, reptiles, and aquatic mammals. At least 47 fish species, 3 frog species, 1 salamander species, 5 turtles species, and 4 aquatic mammal species could be vulnerable to greater than normal winter drawdown scenarios, based on their winter habitat use of shallow margins of LSL that could become exposed during drawdowns. Other ecological impacts would possibly include declines in the abundance and diversity of benthic invertebrate and macrophyte assemblages, with consequential impacts to the overall food web of LSL. Further work including monitoring and field studies are recommended to validate the modelled output and the assessments of species vulnerabilities to winter drawdown scenarios.

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INTRODUCTION

In January 2017, the International Joint Commission (IJC) implemented a new regulation plan for the outflows of Lake Ontario known as Plan 2014. This plan was agreed to by the United States and Canada in December 2016 in an effort to improve environmental performance while maintaining most of the benefits provided to other interests by the previous Plan 1958-D, which was in use since 1963. In determining outflows, the International Lake Ontario St. Lawrence River Board (ILOSLRB, the Board), in conjunction with its staff, pays close attention to water levels in the Lake Ontario-St. Lawrence River system and on the Great Lakes upstream, and to the effects on stakeholders within the basin. Coincident with the implementation of the new regulation plan, increased water supplies in the Lake Ontario - St. Lawrence River system and Ottawa River Basin have resulted in record high water levels on Lake Ontario and the St. Lawrence River in 2017 and again in 2019, and consequent record-low water levels on LSL in 2018.

In its ongoing response to the continuing high water conditions in the Lake Ontario – St. Lawrence River system and particularly on Lake Ontario, the IJC, through its ILOSLRB and Great Lakes – St. Lawrence River Adaptive Management (GLAM) Committee, is investigating all possible options for maximizing the amount of water removed from Lake Ontario to reduce the possibility of a significant flood event again in 2020. One of the options is maximizing the water released through the Moses-Saunders dam during the winter months. Ice effects and winter operations of the Moses-Saunders Dam in accordance with direction from the IJC’s ILOSLRB have historically resulted in a large drawdown in water levels on Lake St. Lawrence (LSL, the forebay for the hydropower structures) during winter months. Further incremental increases in releases during the winter could result in further water level drawdown on LSL during the winter months.

There is uncertainty regarding the possible ecological implications of substantially increased winter drawdown in LSL. The goal of this project is to fill a knowledge gap regarding the potential ecological impacts of atypical winter drawdown scenarios on LSL. This report summarizes an initial assessment to identify potential incremental ecological impacts from extreme drawdowns contemplated by the ILOSLRB, conducted through a current literature review of the potential ecological effects of winter drawdowns associated with hydroelectric dam operations, and a geographic information systems (GIS)

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analysis to estimate the sensitivity of aquatic species to low water level scenarios in LSL. This initial effort also identifies topics to be considered for future field investigations.

The primary deliverables of this study were the following: Task 1 Coordination with members of the ILOSLRB and GLAM Committee to discuss project objectives and timelines. Task 2 Literature review and coordination of input from subject matter experts, documented in draft report submitted for Task 5. Task 3 GIS assessment of habitat change under potential water drawdown scenarios, documented in draft report submitted for Task 5. Task 4 Assessment of the potential for impacts to vulnerable species in Lake St. Lawrence based on information gathered in Task 2 and Task 3, documented in draft report submitted for Task 5. Task 5 A draft report summarizing work in Task 2-4 and a presentation to IJC project authority and representatives of the GLAM Committee. Task 6 A final report summarizing the findings of this study.

METHODS

Study area

LSL is a 50 km long section of the Upper St. Lawrence River (USLR) located between the Iroquois Control Dam and the Moses-Saunders (M-S) Power Dam near Cornwall, Ontario (Figure 1). This fluvial lake is an impoundment that was created with the construction of St. Lawrence hydropower and seaway projects, which effectively flooded the former Long Sault Rapids above the M-S Power Dam and increased the immediate upstream river surface area by over 200% and the nearshore aquatic habitat by 20% (Lapan et al., 2002). Much of the flooded areas are former agricultural fields and villages, and are characterized by shallow flat areas that are subject to frequent water level fluctuations (R.E. Grant & Associates, 1999b). As a consequence of seasonal water level fluctuations, submerged and emergent aquatic plants are relatively sparse above drawdown zones, and mudflats frequently form during lower water level periods. The overall bathymetry of LSL is characterized by deep channels with steep gradients in the immediate forebay of the M-S Power Dam, and shallow, gently sloping shorelines in flooded embayments.

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LSL is the forebay of the M-S Power Dam and, as such, is subject to significant water level fluctuations, especially during the winter months when ice effects and significant flow changes often are experienced. Spring to fall (March to November inclusive) water levels on LSL fluctuate an average of 1.14 m each year, within a minimum/maximum range of 2.95 m recorded between 1960 and 2019 (Figure 2). Winter water levels on LSL fluctuate an average of 0.76 m (December to February inclusive), although wider fluctuations in excess of 2 m have been recorded during a single season (e.g. 2019; Figure 2). Water levels for the 2019/2020 winter season fluctuated 1.87 m, with near-historical minimum levels reached in January 2020 (Figure 2).

The aquatic ecosystems of this section of the river were significantly impacted by the construction of the St. Lawrence Seaway. Prior to the 1950s, what is now LSL was relatively narrow and fast-flowing river, with aquatic biota that were adapted to cooler, fast flowing water, coarser bottom substrates, biologically diverse wetlands, and frequent ice jamming and scouring events (Lapan et al., 2002). A number of habitat types were lost or heavily modified after the LSL reservoir was created, including the Long Sault Rapids and wetlands associated with tributaries. Significant shifts in the fish community have occurred due to the loss of white water spawning habitat and an increase in shallow, warm water habitat (Lapan et al., 2002; NYSDEC, 2018; R.E. Grant & Associates, 1999a). Introductions of aquatic invasive species, including Dreissenid mussels, Eurasian milfoil (Myriophyllum spicatum), and round goby (Neogobius melanostomus), continue to influence the ecology of the system. It is within this context that we examine the ecological impacts of winter drawdown operations of the M-S Power Dam under historical and hypothetical scenarios.

Literature review

A review was undertaken to: 1) identify aquatic and semi-aquatic species known to overwinter in the LSL portion of the St. Lawrence River; 2) synthesize extant literature on the overwintering habitat requirements of aquatic species known to inhabit LSL; and 3) to summarize relevant studies of the ecological impacts of winter drawdowns on lake and river reservoirs. The review included peer- reviewed articles, books, online resources, and grey literature sources. Peer-reviewed articles were searched using the ISI Web of Science and Google Scholar databases.

Occurrence data for LSL aquatic biota were derived from several sources. Data for benthic invertebrates, reptiles and amphibians, and aquatic mammals were sourced from published literature and online species distribution maps published by the Ontario provincial government and Ontario 4

Nature. Data on fish species occurrences in LSL were derived from several sources, including: 1) the gill net assessment program in LSL jointly administered by the New York State Department of Environmental Conservation (NYSDEC) and the Ontario Ministry of Natural Resources and Forestry (OMNRF) (NYSDEC, 2018); 2) the New York State Fisheries Database (v. 61), which summarizes fish survey data from multiple organizations including the NYSDEC, the U.S. Geological Survey (USGS), the U.S. Fish and Wildlife Service (USFWS), and the St. Regis Mohawk Tribe (SRMT); 3) Fisheries and Oceans Canada (DFO); and 4) nearshore seine surveys conducted in the Canadian waters of LSL by the River Institute (2015-2019). In addition to consultations with subject matter experts (SMEs) at the River Institute, experts at the NYSDEC, OMNRF, DFO, and SRMT were consulted to ensure comprehensive inclusion of all available datasets.

The review generated a summary of available information on the overwintering habitat requirements of benthic invertebrates, fish, reptiles and amphibians, and aquatic mammals in LSL, including timing of winter habitat usage, depth ranges, temperature and oxygen tolerances, and bottom substrate associations (summarized in the Appendices). This information was used to inform an analysis of possible ecological impacts that may occur under various winter water drawdown scenarios in LSL. The results of the literature review were related to modelled GIS water level scenarios to identify potentially vulnerable species (including species at risk).

GIS analyses of water level scenarios

The purpose of the GIS analyses was to reveal the extent of river bottom exposed under incremental water level drawdowns, and to qualitatively relate this to winter habitat requirements of known aquatic species in the area. Modelled bathymetry for LSL was provided by the National Hydrological Service of Environment and Climate Change Canada (ECCC), and is based on depth soundings from the Canadian Hydrographic Service (CHS), the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Army Corps of Engineers (USACE). The data were vertically referenced as elevations (m) on the International Great Lakes Datum 1985 (IGLD85), and were provided in a projected coordinate system (NAD 1983, UTM Zone 18N). The accuracy (95% confidence level) of CHS depth soundings varies from 2- 5 m horizontally and 0.15-0.5 m vertically (Canadian Hydrographic Service, 2013). Bathymetry data were provided as a point grid with an average neighbour distance of 18 m. Using a GIS (ArcGIS Pro 2.4, ESRI 2020), point data were interpolated using a spline function to maintain original bathymetry values, and a bathymetric digital elevation model was created with a spatial resolution of 5 m (Figure 3). This

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bathymetry model was subsequently used as a template for modelling riverbed exposure under various water level scenarios.

Six winter water level scenarios for LSL were provided by Environment and Climate Change Canada and the International Joint Commission (Tables 1 & 2), and are based on historical and hypothetical data from five stationary water gauges in LSL (Figure 1). Scenarios 1 to 3 represent the average range of winter operating conditions for LSL, while Scenarios 4 to 6 represent more extreme hypothetical drawdown conditions (Table 1). Normal low water levels for LSL during winter are bounded by Scenario 1, which represents the typical minimum water levels during the navigation season (L Limit), and Scenario 3, which is determined by the maximum allowable outflows during the winter months to ensure the safe formation of an ice cover (I Limit). A gradient of increasingly lower water levels are represented by Scenario 4 (recorded low water level event during the 2020 winter season), Scenario 5 (lowest recorded winter water level on record at the Long Sault gauge), and Scenario 6 (hypothetical extreme low level at the Long Sault gauge). In terms of interpreting these scenarios and the results of the water level modelling exercises, comparisons were made between typical winter drawdown levels from Scenarios 1 to 3 and hypothetical extreme drawdown levels from Scenarios 4 to 6.

Water gauge levels were interpolated using a spline function to create a digital water surface layer (elevation, m) for each scenario, with a spatial resolution of 5 m. Using Image Analyst tools in ArcGIS Pro, the water layer for each scenario was subtracted from the bathymetry model of LSL to produce estimates of the amount of riverbed that would be inundated or exposed. Spatial Analyst tools in ArcGIS Pro were used to estimate the number of isolated pools created under each scenario, as well as the area of each pool. Previously collected UAV imagery of LSL by the River Institute was used to cross-validate modelled water level stages.

RESULTS & DISCUSSION

Literature review

Overall impacts of dams and water control structures on aquatic ecosystems have been studied extensively, including the impacts of hydro peaking, ponding, unrestricted flows, drawdowns, and comparisons with non-regulated and pre-construction conditions (Baxter & Glaude, 1980; Bain et al., 1988; Rosenburg et al., 1997; Haxton & Findlay, 2009; Macnaughton et al., 2016). The impacts of winter drawdown on freshwater aquatic species appears to be largely dependent on the magnitude of the 6

drawdown as well as the duration of the drawdown period (Carmignani & Roy, 2017). Typically, reservoirs become dominated by tolerant taxa over time. However, shallow nearshore habitats created by reservoirs are the most vulnerable to water level fluctuations. Potential impacts of winter drawdowns are reviewed for LSL taxa. Detailed information on species assemblages and winter habitat requirements for LSL are provided in the Appendices.

Benthic invertebrates

LSL is home to a rich diversity of benthic invertebrate taxa (Appendix A). Habitat requirements and timing of overwintering habitat use of these taxa are detailed in Appendix B. A review of studies examining the effects of drawdowns on benthic invertebrates found a general consensus of negative outcomes for macroinvertebrate communities within winter drawdown zones (Danks, 1971; Paterson & Fernando 1969; McEwen & Butler, 2010; Carmignani & Roy, 2017; Trottier et al., 2019). Nearshore habitats tend to have a greater concentration of insect invertebrates, and therefore may be impacted by water levels to a greater degree. Macroinvertebrates have been found to have stronger negative responses to winter drawdowns compared to macrophytes and fish assemblages in the littoral zones of regulated lakes (Sutela et al., 2013). Oswood (1991) suggested that larger-bodied insects may be at greater risk, as well as non-burrowing taxa. However, these impacts would be somewhat mitigated by relatively warm winter conditions and intermittent refilling.

Invertebrates have three fundamental strategies when facing cold stress: 1) remain in a habitat that will freeze; 2) move (either vertically or horizontally) to an unfrozen habitat; or 3) remain in a habitat not subject to freezing (deep waters of large lakes/rivers) over their entire lifecycle (Oswood et al. 1991). Studies of direct freezing demonstrate variable survivability of a range of taxa, however comparisons of freezing survival of taxa in laboratory and field studies often find much lower survival rates in lab studies (Olsson 1982). This is likely a result of rapid freezing in experimental setups, as well as the duration of the freeze cycle. Several studies (e.g. Andrews and Rigler 1985; Danks 1971; Salt 1963) suggest that many insects have the ability to supercool their bodies through physical freeze protections or chemical freeze protection, allowing them to withstand temperatures between -3C and -11C. Many taxa exposed to freezing conditions have been found with special structures such as coverings (gastropods) and cysts (oligochaets) designed to help combat freeze conditions (Oswood et al., 1991). A laboratory experiment by Oswood et al. 1991 demonstrated that chironomids will actively migrate deeper into substrates when exposed to freezing temperatures.

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Fish

Over 70 species of fish have been documented in LSL from surveys dating back to the early 1980s, including six species at risk (Appendix C). Many of these species may inhabit shallow depths during winter (Appendix D) and therefore have the potential to become impacted by low water levels. Studies of winter drawdown effects on fish communities have generally noted that the most significant impacts occur within the littoral zones, including changes to species assemblages and reduced abundance that are linked to loss of habitat, lower dissolved oxygen, and food web disturbances (Carmignani & Roy, 2017; Cott et al., 2008; Haxton & Findlay, 2009; Tapio Sutela & Vehanen, 2008; Weber et al., 2013). Early and rapid winter drawdowns have been linked to significant fish winterkills (Gaboury & Patalas, 1984; Hurst, 2007) and altered predator movements (Rogers & Bergersen, 1995). The likelihood of fish stranding events in freshwater systems has been positively linked to factors such as low water flow, gradually sloped shorelines, complex structure in littoral zones, cooler water temperatures, rapid water level changes, ice dams, and poor water quality (e.g. hypoxic conditions; see review by Nagrodski et al. (2012) and references therein). LSL may be particularly sensitive to fish stranding events from rapid water level changes, given the gradual slope of many of the larger bays, which also lack complex structure and have reduced flow during the winter. Rapid water level fluctuations during winter drawdowns may result in the formation of isolated pools or even complete dewatering of occupied fish habitat, with both lethal and sub-lethal consequences.

Herpetofauna

Eight species of frogs and toads, six species of turtles, and one species of aquatic salamander have been documented in LSL (Appendix E). Although many toads and frogs in the region overwinter as adults, they can also overwinter as tadpoles. We recommend that both life stages be considered for potential effects of water drawdowns in LSL. In general, tadpoles can be more tolerant than adults (e.g. can withstand more prolonged hypoxia compared to adults; Tattersall and Ultsch 2008). Tadpoles do however require ice-free water to avoid freezing and to respire. Amphibian species that overwinter on land as adults, including the American toad, the wood frog, the Western chorus frog, the spring peeper and the gray treefrog, were excluded from this analysis. Frogs that do overwinter in aquatic habitats require ice-free water to avoid freezing and for respiration (Appendix F). Frogs can burrow in mud during times of low water, but will lack oxygen within a few days (Tattersall and Ultsch 2008). All species of turtles in LSL are considered species at risk. Turtles normally retreat to hibernaculum in October,

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which is generally in mid- to shallow waters (i.e. <3 m, except for the northern map turtle) and either burrow in mud or rest on top of the substratum. Oxygen requirements for turtles vary from low to high depending on species (Appendix F). Mudpuppies are active during the winter and require some depth of ice-free water to facilitate movement.

There is a general lack of literature examining the effects of winter drawdowns on amphibians and reptiles. However, based on the life history of the frog and turtle species in Eastern Ontario, drawdowns should be conducted ideally prior to September before individuals seek hibernaculum. In one study by Hall and Cuthbert (2000), sites affected by winter drawdowns were found to have mass mortalities for Blanding’s turtles. Many species of frogs and turtles require ice-free water to successfully overwinter, thus if drawdowns are after individuals settle in hibernaculum, individuals would be exposed to a high risk of anoxia, desiccation, freezing and predation. Movement into hibernacula refuges begins in September and October for most species of amphibians and reptiles, and varies according to water temperature, water levels and latitudinal climate gradients (Appendix F). Given the historical ranges of winter water level fluctuations in LSL (Figure 2), it is likely that shallow marginal habitats for herpetofauna have been of relatively poor quality since the 1960s. Recommendations to improve the habitat quality of these areas include conducting drawdowns prior to fall and also to conduct further research to better understand the effects of winter drawdowns on aquatic and semi-aquatic herpetofauna.

Aquatic mammals

Aquatic mammal species that are known to occur in LSL include the beaver, the muskrat, the mink and the otter (Appendix G). All of these semi-aquatic species are active throughout the winter months and therefore have dynamic winter habitat requirements (Appendix H). The beaver and the muskrat create lodges in the water from plant material to store resources for the winter months and for shelter. Otters and minks opportunistically inhabit dens created by other mammals (e.g. foxes, muskrats, etc.) in or near water and forage in/near aquatic habitats throughout the winter. Winter drawdowns could have substantial consequences on the fitness of semi-aquatic mammals inhabiting LSL. Beavers and muskrats, in particular, are vulnerable to drawdowns as they depend on permanent water bodies for overwintering success. Both beavers and muskrats are active during winter months and depend on their lodges (created from plant material) for resources (i.e. shelter, food). Drawdowns can affect body mass of both beavers and muskrats, as resources are likely to become inaccessible if water levels are too low.

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Beavers reproduce and gestate during the winter months (Boonstra 2013), thus, drawdowns can affect the body mass of beaver kits particularly (Smith and Peterson 1991). It is recommended that winter drawdowns do not exceed 0.7 m to minimize the negative effects on beaver populations (Smith and Peterson 1991). While muskrats require less water depth than beavers, permanent water is essential for winter foraging and water levels are directly linked to muskrat abundance (Perry 1982). The effects of winter drawdowns on minks and otters require further research, however, drawdowns are expected to reduce habitat and resource availability for all semi-aquatic mammals similarly (Carmignani and Roy 2017; Wlosinski and Koljord 1996).

GIS analyses

Using a bathymetric digital elevation model and water level scenarios provided by ECCC and the IJC, this study was able to model the impacts of drawdowns in terms of the area of exposed and inundated riverbed in Lake St. Lawrence along a gradient of typical (scenarios 1 to 3) to severe (scenarios 4 to 6) drawdown conditions (Figure 4). The drawdown range for scenarios 1 to 3 was 0.84 m, while scenarios 4 to 6 represented an additional drawdown of 1.49 m, for a total range of 2.33 m across all scenarios. While the amplitude of drawdown is commonly used as a measure of disturbance, other metrics such as areal loss of habitat or the proportion of exposed lake bed have been recommended (Carmignani & Roy, 2017). Area of bed exposure is particularly relevant for shallow littoral areas that are more sensitive to water level fluctuations (Coops et al., 2003), as is the case with LSL. In the current study, typical winter drawdowns from scenarios 1 to 3 result in a 170% predicted increase in exposed riverbed (Table 3). Using Scenario 3 as a typical winter low water level baseline, there were moderate to large predicted increases in exposed riverbed moving from the hypothetical extremes of Scenario 4 (16%), Scenario 5 (53%), and Scenario 6 (80%). The majority of exposed riverbed occurred in the immediate forebay of LSL, within 20 km of the M-S Power Dam (Figure 4). The percentage of exposed riverbed under winter drawdown scenarios ranged from 5.5% in Scenario 1 to 26.6% in Scenario 6 (Figure 4). In particular, the bays along the north shore of the river near the Long Sault Parkway and Ingleside, and the south shore to the east of Massena were significantly dewatered under Scenarios 4 to 6 (Figure 5). A closer view of the exposed riverbed near Ingleside is shown in Figure 6, to illustrate how trenches and pools become increasingly isolated as water levels decline from Scenario 1 to Scenario 6.

Modelling of winter drawdowns for LSL suggested small to moderate increases (6-17%) in the number of isolated pools when comparing scenarios 4 to 6 to the typical minimum winter baseline of Scenario 3

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(Table 4). A maximum of 238 isolated pools were predicted for Scenario 5. Variations in the predicted number and area of isolated pools from scenarios 4 to 6 were due to how lowering water levels affected the connectivity the remaining water body. For example, declining water levels from scenarios 5 to 6 resulted in large sections of embayments becoming completely exposed, causing a reduction in the number of isolated pools for these areas (see Figure 6 for visual example). Large increases in the percent of exposed riverbed in Scenarios 5 and 6 also resulted in a reduced area of isolated pools compared to Scenario 3 (Table 4). While the overall area of isolated pools under all scenarios was less than 1% of the total LSL area, the simulated drawdowns in scenarios 4 to 6 revealed increasing numbers of isolated pools due to the shallow slope of many of the embayments. This suggests that the ecological risk of species becoming trapped in pools increases with drawdowns below the typical winter baseline of

Scenario 3. The number of small isolated pools (less than 25 m2) was greatest in Scenario 5, although Scenarios 2 and 3 also had similar results for small pools (Figure 7). For all scenarios, the majority of isolated pools were over 100 m2. The average predicted depth of isolated pools across all area sizes was less than 20 cm (Figure 8). Aquatic species that become trapped in small, shallow pools would be predicted to suffer from a more rapid rate of oxygen depletion and thermal cooling compared to species trapped in larger, deeper pools. It is unlikely but possible that larger fish could become trapped in these shallow pools if drawdown occurred too rapidly and ice formation inhibited connectivity with the main river body.

As a cross-validation exercise, modelled water levels and exposed riverbed for Scenario 1 were compared to UAV imagery collected by the River Institute on October 1, 2018 (Figure 9). Recorded water levels on the date of the UAV survey were 72.65 m at the Long Sault water gauge, compared to the level of 72.6 m at the same gauge that was used to model Scenario 1. Delineations of inundated and exposed river sections from the Scenario 1 model matched very closely with the UAV imagery (Figure 9), suggesting that the GIS outputs were providing relatively accurate predictions of scenario conditions. It is recommended that additional UAV surveys be conducted during future winter drawdown periods and covering a greater geographic distribution to provide a more accurate and detailed cross-validation of the GIS model outputs.

Assessment of ecological vulnerability

A comprehensive species inventory was compiled for LSL, including known winter habitat requirements for benthic invertebrates, fish, amphibians, reptiles, and aquatic mammals (See Appendices). This

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inventory was assessed to identify taxa/species that may be vulnerable to acute stress and mortality from extreme winter drawdown levels (Table 5). Vulnerability was assessed by cross-referencing the winter habitat requirements with modelled drawdown scenarios, and identifying species that may be found within the exposure zone of the shallowest areas. A total of 47 fish species were identified that may be found in shallow (0-1 m) habitats during winter, of which four are listed as species-at-risk (SAR) in Ontario (Table 5). The majority of vulnerable fish species were minnows. The potential for stranding of larger fish is relatively low given the average shallow depths of most isolated pools (< 20 cm) and the ability of larger fish to move with declining water levels. However, there could still be a risk of stranding of larger fish in some isolated, deeper pools. In terms of amphibians, three frog species and one salamander may be impacted by winter drawdowns, although none are listed as SAR. Six species of turtle were found to be vulnerable to winter drawdown scenarios, all of which are either SAR or currently under consideration for being listed as SAR (Table 5). The four most common aquatic mammals that make use of LSL may show varying degrees of vulnerability to winter drawdown, which depends mainly on the duration of the drawdown rather than the decline in water levels. None of the mammal species are listed as SAR (Table 5).

CONCLUSIONS AND RECOMMENDATIONS

The combined results of the literature review, species inventory, and modelling of water level scenarios suggest that significant ecosystem impacts could result from extreme winter drawdown scenarios for Lake St. Lawrence, under certain conditions. Substantial areas of the river have likely been exposed repeatedly under historical drawdown levels, with the most exposed areas occurring in bays along the northern inside shore of the Long Sault Parkway, near Ingleside, and the south shore west of Massena. Hypothetical drawdown levels occurring at the most extreme limits (Scenario 6) could result in up to 25% of LSL having exposed riverbed, with hundreds of isolated pools of water that could strand aquatic life with the potential to result in visible impacts in these areas.

A review of relevant literature indicates that most aquatic taxa respond negatively to extreme winter drawdowns that occur at a rapid rate, and that generally, taxa are able to survive if drawdowns do not occur for prolonged durations. Many taxa begin choosing overwintering habitats in the fall (September- October), where they may remain stationary until the spring. Amphibians, reptiles, and small fish species may be particularly vulnerable to exposure given that many inhabit shallow depths and have limited movement capabilities during the winter. For such taxa, it is recommended that winter 12

drawdown levels do not exceed the lowest fall water stage levels. For scenarios where this would not be possible, it is recommended that winter drawdowns occur at a slower rate and for a limited duration to increase the opportunity for species to relocate and recover from low oxygen availability, temperature fluctuations, and potential stranding in isolated pools. Further study of the ecological and physiological effects of winter stranding on LSL vulnerable biota, from either field observations or mesocosm experiments, is recommended.

The study represents a modelling exercise, and should therefore be interpreted with due caution. Aquatic biota of LSL have had 60 years to adapt to nearshore environments that have historically experienced significant and frequent water level fluctuations due to the operations of the Moses- Saunders Power Dam. These conditions have likely shaped aquatic communities such that they are composed of species that are tolerant of drawdown conditions in winter. However, practical data on winter habitat use is lacking for LSL and would need to be collected to confirm such assumptions. It is recommended that a follow-up study be conducted to confirm the modelled winter water level stages using comprehensive UAV surveys. It is also recommended that monitoring and surveys of winter habitat quality and species occurrences be conducted, with a focus on bays of LSL that were predicted to have significant riverbed exposure and isolated pools under all likely water stage scenarios.

13

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TABLES

Table 1. Context of modelled winter water level stage scenarios.

Scenario Context 1 Typical minimum L Limit during navigation season 2 Hypothetical with Long Sault at 72 m 3 Typical minimum I Limit level for ice formation 4 Recorded low Long Sault level event during Winter 2020 5 Lowest daily level at Long Sault on record 6 Estimated profile with Long Sault at 70.5 m

Table 2. Coordinates of water gauge stations in Lake St. Lawrence, with corresponding water stage levels (elevation, m) under six different scenarios (refer to Table 1 for context).

Scenario Scenario Scenario Scenario Scenario Scenario Gauge Name Latitude Longitude 1 2 3 4 5 6 Iroquois TW 44.8346 -75.3087 73.26 73.09 72.96 72.8 72.67 72.3 Waddington 44.8648 -75.2085 72.96 72.6 72.43 72.26 - 71.4 Morrisburg 44.8905 -75.1908 72.93 72.54 72.36 72.2 71.6 71.3 Long Sault South Shore 44.9978 -74.8632 72.6 72 71.8 71.55 71.06 70.5 Saunders HW 45.0091 -74.7903 72.53 71.93 71.69 71.46 70.91 70.2

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Table 3. Modelled predictions of the amount of riverbed in Lake St. Lawrence (LSL) that would be inundated or exposed under six different winter water level scenarios. The Saunders headwater (HW) gauge level for each scenario is provided for context. Scenarios 1 to 3 show typical winter conditions (green highlighted) while Scenarios 4 to 6 show hypothetical extreme low drawdown scenarios (red highlighted). The percent change from the minimum typical winter low water level conditions (Scenario 3) is shown.

% increase Saunders Water level LSL LSL LSL % in exposed HW gauge decrease from inundated exposed exposed area from Scenario level Scenario 3 (m) area (km2) area (km2) area Scenario 3 1 72.53 - 117.117 6.790 5.5 - 2 71.93 - 108.604 15.303 12.4 - 3 71.69 - 105.637 18.270 14.7 - 4 71.46 0.23 102.735 21.173 17.1 15.9 5 70.91 0.78 95.978 27.929 22.5 52.9 6 70.2 1.49 90.993 32.914 26.6 80.2

Table 4. The area (km2) and number of isolated pools of water predicted under six modelled scenarios of winter water levels in Lake St. Lawrence. Scenarios 1 to 3 show typical winter conditions (green highlighted) while Scenarios 4 to 6 show hypothetical extreme low drawdown scenarios (red highlighted). The percent change from the minimum typical winter low water level conditions (Scenario 3) is shown.

% increase in % increase in # area of isolated of isolated pools from pools from Scenario Area of Isolated pools (km2) Scenario 3 # isolated pools Scenario 3 1 0.055 - 52 - 2 0.508 - 165 - 3 0.434 - 203 - 4 0.478 10.1 216 6.4 5 0.246 -43.2 238 17.2 6 0.245 -43.6 221 8.9

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Table 5. A list of aquatic taxa (fish, amphibians, reptiles, mammals) that may be vulnerable to acute stress and mortality from extreme winter drawdown levels in Lake St. Lawrence. Vulnerability was assessed by identifying species that may be found within the exposure zones across all modelled drawdown scenarios.

Conservation Taxa guild Family Common name Scientific name status Fish Amiidae Bowfin Amia calva None Esocidae Northern pike Esox lucius None Muskellunge Esox masquinongy None Umbridae Central mudminnow Umbra limi None Catostomus Catostomidae White sucker None commersonii Moxostoma Silver redhorse None anisurum Moxostoma Shorthead redhorse None macrolepidotum Moxostoma Greater redhorse None valenciennesi Cyprinidae Common carp Cyprinus carpio Non-native Exoglossum Cutlip minnow Threatened maxillingua Notemigonus Golden shiner None crysoleucas Pugnose shiner Notropis anogenus Threatened Bridle shiner Notropis bifrenatus Special concern Common shiner Luxilus cornutus None Blackchin shiner Notropis heterodon None Blacknose shiner Notropis heterolepis None Eastern silvery minnow Hybognathus regius None Rhinichthys Longnose dace None cataractae Spottail shiner Notropis hudsonius None Rosyface shiner Notropis rubellus None Spotfin shiner Cyprinella spiloptera None Sand shiner Notropis stramineus None Mimic shiner Notropis volucellus None Bluntnose minnow Pimephales notatus None Pimephales Fathead minnow None promelas Semotilus Creek chub None atromaculatus Fallfish Semotilus corporalis None Ictaluridae Yellow bullhead Ameiurus natalis None 22

Conservation Taxa guild Family Common name Scientific name status Brown bullhead Ameiurus nebulosus None Channel catfish Ictalurus punctatus None Tadpole madtom Noturus gyrinus None Fundulidae Banded killifish Fundulus diaphanus None Anguillidae American eel Anguilla rostrata Endangered Ambloplites Centrarchidae Rock bass None rupestris Pumpkinseed Lepomis gibbosus None Lepomis Bluegill None macrochirus Micropterus Largemouth bass None salmoides Pomoxis Black crappie None nigromaculatus Percidae Yellow perch Perca flavescens None Walleye Sander vitreus None Iowa darter Etheostoma exile None Etheostoma Fantail darter None flabellare Logperch Percina caprodes None Etheostoma Tessellated darter None olmstedi Atherinopsidae Brook silverside Labidesthes sicculus None Cottidae Mottled sculpin Cottus bairdii None Neogobius Gobiidae Round goby Non-native melanostomus Lithobates Amphibians Ranidae American bullfrog None catesbeianus Lithobates Green frog None clamitans melanota Northern leopard frog Lithobates pipiens None Proteidae Common mudpuppy Necturus maculosus None Reptiles Chelydridae Snapping Turtle Chelydra serpentina Special Concern Emydoidea Emydidae Blanding’s Turtle Threatened blandingii Wood Turtle Glyptemys insculpta Endangered Graptemys Northern Map Turtle Special Concern geographica Under Chrysemys picta Midland Painted Turtle consideration for marginata addition

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Conservation Taxa guild Family Common name Scientific name status Sternotherus Kinosternidae Eastern Musk Turtle Special Concern odoratus Mammals Castoridae North American beaver Castor canadensis None Cricetidae Muskrat Ondatra zibethicus None Mustelidae American mink Neovison vison None North American river Mustelidae Lontra canadensis None otter

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FIGURES

Figure 1. Lake St. Lawrence (LSL) section of the St. Lawrence River for which bathymetry data is available (highlighted), with locations of water level gauges (TW = tail water/downstream of dam); HW = head water/upstream of dam). The upper and lower geographic limits of LSL are defined by the Iroquois Control Dam (Iroquois TW) and the Moses-Saunders Power Dam (Saunders HW).

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Figure 2. Seasonal water level fluctuations for Lake St. Lawrence, showing historical averages (1960-2019) and min/max ranges as well as recent yearly data from 2017-2020.

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A

D B

C

Figure 3. Bathymetric digital elevation model (A) of Lake St. Lawrence (LSL), based on soundings from the Canadian Hydrographic Service (CHS), the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Army Corps of Engineers (USACE). Linked inset panels show increasing detail for the forebay of LSL upstream of the Moses-Saunders Power Dam (B), Hoople Bay (C), and the southwestern area of Hoople Bay (D).

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Figure 4. Modelled output of the Lake St. Lawrence portion of the St. Lawrence River under six winter water level scenarios. See Tables 1 and 2 for modelled water stage details.

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A

D B

C

Figure 5. Example of modelled output of inundated and exposed areas of Lake St. Lawrence (LSL; Panel A) under Scenario 4 water levels (refer to Tables 1 and 2 for details). Linked inset panels show increasing detail for the forebay of LSL upstream of the Moses-Saunders Power Dam (B), Hoople Bay (C), and the southwestern area of Hoople Bay (D).

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Figure 6. Modelled output of Lake St. Lawrence water level scenarios near Ingleside, Ontario (spatial reference shown in inset map, highlighted yellow extent indicates larger view). See Tables 1 and 2 for modelled water stage details. The spatial extent of riverbed exposure is evident with increasing drawdown levels, resulting in increasingly isolated pools of water in some areas. 30

Figure 7. Predicted number of isolated pools of water of various size classes (area, m2) created under six different winter water level scenarios. See Tables 1 and 2 for modelled water stage details.

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Figure 8. Boxplot of predicted depths for various size classes of isolated pools of water (area, m2) created under six different winter water level scenarios. Outlier values are represented by circles (o) and extreme values are represented by asterisks (*). See Tables 1 and 2 for modelled water stage details.

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Figure 9. Cross-validation of modelled output of Scenario 1 water levels (Long Sault water gauge = 72.6 m) with remotely sensed UAV imagery capture at the equivalent water level on October 1, 2018 (Long Sault water gauge = 72.65 m) at the Hoople Bay causeway. The top panel shows the high-resolution UAV imagery superimposed on a lower resolution satellite background, with exposed river bottom delineated by a polygon. The lower panel shows the UAV imagery superimposed on the modelled Scenario 1 output predicting inundated and exposed areas of the river.

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APPENDIX A

List of benthic invertebrates occurring in Lake St. Lawrence, with references.

Order Family Genus Reference Odonata Aeshnidae Nilo et al. 2006 Coenagrionidae Nilo et al. 2006 Gomphidae Nilo et al. 2006 Trichoptera Brachycentridae Nilo et al. 2006 Hydropsychidae Nilo et al. 2006 Hydroptilidae Nilo et al. 2006 Leptoceridae Nilo et al. 2006 Philoptamidae Nilo et al. 2006 Psychomyiidae Nilo et al. 2006 Polycentropodidae Nilo et al. 2006 Sericostomatidae Nilo et al. 2006 Phylocentropus Griffiths 1988 Ephemeroptera Caenidae Caenis Kipp and Ricciardi (2012) Baetidae Nilo et al. 2006 Ephemeridae Nilo et al. 2006 Heptageniidae Nilo et al. 2006 Neoephermeridae Nilo et al. 2006 Polymitarcidae Nilo et al. 2006 Siphlonuridae Nilo et al. 2006 Diptera Chironomidae Pseudochironomus Haynes & Makarewicz 1982 Chironomidae Stictochironomus Haynes & Makarewicz 1982 Chironomidae Clinotanypus Haynes & Makarewicz 1982 Chironomidae Procladius Haynes & Makarewicz 1982 Chironomidae Chironomus Haynes & Makarewicz 1982 Chironomidae Paratendipes Haynes & Makarewicz 1982 Chironomidae Cryptochironomus Griffiths 1988

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Order Family Genus Reference Chironomidae Dicrotendipes Griffiths 1988 Chironomidae Harnischia Griffiths 1988 Chironomidae Parachironomus Griffiths 1988 Chironomidae Paralauterborniella Griffiths 1988 Chironomidae Paratanytarsus Griffiths 1988 Chironomidae Phaenopsectra Griffiths 1988 Chironomidae Polypedilum Griffiths 1988 Chironomidae Rheotanytarsus Griffiths 1988 Chironomidae Tanytarsus Griffiths 1988 Chironomidae Tribelos Griffiths 1988 Chironomidae Orthocladus Griffiths 1988 Chironomidae Nanocladius Griffiths 1988 Chironomidae Psectrocladius Griffiths 1988 Chironomidae Ablabesmyia Griffiths 1988 Chironomidae Clinotanypus Griffiths 1988 Ceratopogonidae Mills et al. 1981 Simuliidae Nilo et al. 2006 Tipulidae Nilo et al. 2006 Isopoda Windle (Unpublished) Coleoptera Haliplidae Mills et al. 1981 Emlidae Griffiths 1988 Gyrinidae Griffiths 1988 Hemiptera Corixidae Nilo et al. 2006 Belostomatidae Nilo et al. 2006 Gastropoda Bithyniidae Bithynia Haynes & Makarewicz 1982 Ancylidae Mills et al. 1981 Physidae Mills et al. 1981 Valvatidae Mills et al. 1981 Hydrobiidae Mills et al. 1981

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Order Family Genus Reference Planorbidae Mills et al. 1981 Pleuroceridae Elimina Kipp and Ricciardi (2012) Lymnaeidae Nilo et al. 2006 Amphipoda Gammaridae Gammarus Haynes & Makarewicz 1982 Bivalvia* Sphaeidae Sphaerium Haynes & Makarewicz 1982 Sphaeidae Musculium Haynes & Makarewicz 1982 Sphaeidae Pisidium Griffiths 1988 Unionidae Lampsilis Haynes & Makarewicz 1982 Dreissenidae Dreissena Kipp and Ricciardi (2012) Oligochaeta** Tubificidae Potamothrix Haynes & Makarewicz 1982 Tubificidae Aulodrilus Haynes & Makarewicz 1982 Tubificidae Limnodrilus Haynes & Makarewicz 1982 Lumbricidae Nilo et al. 2006 Aelosomatidae Nilo et al. 2006 Enchytraeidae Nilo et al. 2006 Megaloptera Sialidae Nilo et al. 2006 Lepidoptera Pyralidae Griffiths 1988 Nematoda Mills et al. 1981

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APPENDIX B

Overwintering habitat requirements of benthic invertebrates inhabiting Lake St. Lawrence, with references. Species/ genera/ Depth Temperature Bottom Oxygen Timing of overwintering habitat References taxa substrate requirements use No winter habitat, may bury Brown et al. Oligochaeta (Aquatic Various -0.7C - -2.2C Soft substrates Low themselves in response to 1953 Worms) thermal change Duffy & Liston Various strategies including Fine sand to 1985; Odonata supercooling, overwintering as <2 m >-1.0C - -6C rocky substrate, Moderate Sawchyn and (Dragon/Damselflies) adults in warmer climates, or plants Gillott 1975; migration to deer water Danks 2007 Patterson and Supercool, some migrate to -3C - -7C Fernando Trichoptera Fine gravel to terrestrial environments or to <2 m (wet) High 1969; Olsson (Caddisflies) rocky substrate deeper waters in response to >0 (dry) 1981; Danks cold 2007 Moore (unpublished); -3.3C (wet) May bury themselves (e.g. Salt 1963; Ephemeroptera Fine gravel to <5 m >0C (dry) High burrowing mayflies), or migrate, Danks 1971; (Mayflies) rocky substrate some demonstrate supercooling Andrews and Rigler 1985; Grimas 1961 Moore (unpublished); Salt 1963; Coleoptera (Beetles) <2 m -7.4C Various Various November – Ice On Danks 1971; Andrews and Rigler 1985;

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Unknown, but does have Danks 2007 Amphipoda (Scuds) <5 m -6C - -7C Various Low supercooling abilities Various, but Danks 2007 Isopoda (Sow Bugs) <5 m Unknown often high in Low Unknown organics Various Typically Mihalicz 2015 strategies associate with Hemiptera (True including plants. May be <2 m Various November – Ice On Bugs) terrestrial found dormant hibernation, within the ice migration itself >-11.0C Danks 1971 No winter habitat, may bury Chironomidae (Non- (when dry) Various Various Low themselves in response to biting Midges) -1.7 – -2.8C thermal change (when wet) Typically soft Oswood et al. No winter habitat, may bury Misc. Diptera (Other -5C - -10C or substrates, 1991 <2 m Various themselves in response to True Flies) lower higher organics, thermal change plants No winter habitat, may bury Danks 2007 Bivalvia (Bivalves, Various <0C Sand to rocks Unknown themselves in response to clams, mussels) thermal change Plants, rocks, Loomis 1991 Gastropoda (Snails) <5 m -13C Low November – Ice On boulders

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APPENDIX C

List of fish species occurring in Lake St. Lawrence. See Methods section for a description of data sources. Conservation status defined by the Endangered Species Act (2007) of Ontario.

Order Family Scientific name Common name Conservation status

Petromyzontiformes Petromyzontidae Ichthyomyzon unicuspis Silver lamprey None Acipenseriformes Acipenseridae Acipenser fulvescens Lake sturgeon Endangered Lepisosteiformes Lepisosteidae Lepisosteus osseus Longnose gar None Amiiformes Amiidae Amia calva Bowfin None Clupeiformes Clupeidae Alosa pseudoharengus Alewife Non-native Alosa sapidissima American shad Non-native Dorosoma cepedianum Gizzard shad Non-native Salmoniformes Salmonidae Oncorhynchus tshawytscha Chinook salmon Non-native Oncorhynchus mykiss Rainbow trout Non-native Salmo trutta Brown trout Non-native Salvelinus namaycush Lake Trout None Osmeriformes Osmeridae Osmerus mordax Rainbow smelt Non-native Esociformes Esocidae Esox lucius Northern pike None Esox masquinongy Muskellunge None Esox americanus vermiculatus Grass Pickerel Special Concern Esox niger Chain pickerel Non-native Umbridae Umbra limi Central mudminnow None Cypriniformes Catostomidae Catostomus commersonii White sucker None Moxostoma anisurum Silver redhorse None Moxostoma macrolepidotum Shorthead redhorse None Moxostoma valenciennesi Greater redhorse None Cyprinidae Chrosomus neogaeus Finescale dace None Couesius plumbeus Lake chub None

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Order Family Scientific name Common name Conservation status

Cyprinus carpio Common carp Non-native Exoglossum maxillingua Cutlip minnow Threatened Hybognathus hankinsoni Brassy minnow None Hybognathus regius Eastern silvery minnow None Notemigonus crysoleucas Golden shiner None Notropis anogenus Pugnose shiner Threatened Notropis atherinoides Emerald shiner None Notropis bifrenatus Bridle shiner Special concern Luxilus cornutus Common shiner None Notropis heterodon Blackchin shiner None Notropis heterolepis Blacknose shiner None Notropis hudsonius Spottail shiner None Notropis rubellus Rosyface shiner None Cyprinella spiloptera Spotfin shiner None Notropis stramineus Sand shiner None Notropis volucellus Mimic shiner None Pimephales notatus Bluntnose minnow None Pimephales promelas Fathead minnow None Rhinichthys cataractae Longnose dace None Semotilus atromaculatus Creek chub None Semotilus corporalis Fallfish None Siluriformes Ictaluridae Ameiurus natalis Yellow bullhead None Ameiurus nebulosus Brown bullhead None Ictalurus punctatus Channel catfish None Noturus flavus Stonecat None Noturus gyrinus Tadpole madtom None Anguilliformes Anguillidae Anguilla rostrata American eel Endangered

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Order Family Scientific name Common name Conservation status

Cyprinodontiformes Fundulidae Fundulus diaphanus Banded killifish None Gasterosteiformes Gasterosteidae Culaea inconstans Brook stickleback None Percopsiformes Percopsidae Percopsis omiscomaycus Trout-perch None Perciformes Moronidae Morone americana White perch Non-native Morone chrysops White bass None Sciaenidae Aplodinotus grunniens Freshwater drum None Centrarchidae Ambloplites rupestris Rock bass None Lepomis gibbosus Pumpkinseed None Lepomis macrochirus Bluegill None Micropterus dolomieu Smallmouth bass None Micropterus salmoides Largemouth bass None Pomoxis nigromaculatus Black crappie None Percidae Perca flavescens Yellow perch None Sander vitreus Walleye (Yellow Pickerel) None Etheostoma exile Iowa darter None Etheostoma flabellare Fantail darter None Etheostoma nigrum Johnny darter None Percina caprodes Logperch None Etheostoma olmstedi Tessellated darter None Atheriniformes Atherinopsidae Labidesthes sicculus Brook silverside None Gobiiformes Gobiidae Neogobius melanostomus Round goby Non-native Scorpaeniformes Cottidae Cottus bairdii Mottled sculpin None

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APPENDIX D

Overwintering habitat requirements of fish species inhabiting Lake St. Lawrence (Coker et al., 2001; Lane et al., 1996a, 1996b, 1996c; Hasnain et al., 2010; Scott & Crossman, 1973). Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class Silver lamprey 1-5+ Cool Gravel, sand, silt - Intermediate

Lake sturgeon 2-5+ Cool Boulder, cobble, rubble, gravel, sand, silt, clay - Intermediate

Longnose gar 2-5+ Warm Gravel, sand, silt, clay - Tolerant

Bowfin 0-5 Warm Gravel, sand, silt - Intermediate

Northern pike 0-5 Cool Rubble, gravel, sand, silt 1.57 Intermediate

Muskellunge 0-5+ Cool Gravel, sand, silt, clay - Intermediate

Central mudminnow 0-2 Cool Gravel, sand, silt - Tolerant

White sucker 0-5+ Cool Bedrock, boulder, cobble, rubble, gravel, sand, silt 2 Tolerant

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Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class

Silver redhorse 0-2 Cool Cobble, rubble, gravel, sand, silt, clay - Intermediate

Shorthead redhorse 0-2 Warm Cobble, rubble, gravel, sand, silt - Intermediate

Greater redhorse 0-2 Warm Bedrock, boulder, rubble, gravel, sand - Intolerant

Common carp 0-2 Warm Rubble, gravel, sand, silt, clay 1.19 Tolerant

Cutlip minnow 0-2 Warm Cobble, rubble, gravel, sand - Intolerant

Golden shiner 0-5 Warm Gravel, sand, silt - Intermediate

Pugnose shiner 0-2 Cool Gravel, sand, silt, clay - Intolerant

Emerald shiner 1-5 Cool Boulder, cobble, rubble, gravel, sand, silt, clay 1.2 Intermediate

Bridle shiner 0-2 Cool Gravel, sand, silt - Intolerant

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Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class

Common shiner 0-2 Cool Rubble, gravel, sand, silt 1.08 Intermediate

Blackchin shiner 0-2 Cool Gravel, sand, silt - Intolerant

Blacknose shiner 0-2 Cool Gravel, sand, silt, clay - Intolerant

Eastern silvery 0-2 Warm Gravel, sand, silt - Intolerant minnow

Longnose dace 0-2 Cool Boulder, cobble, rubble, gravel, sand, silt - Intermediate

Spottail shiner 0-5+ Cool Cobble, rubble, gravel, sand, silt - Intermediate

Rosyface shiner 0-2 Warm Cobble, rubble, gravel, sand, silt, clay - Intermediate

Spotfin shiner 0-2 Warm Gravel, sand, silt - Intermediate

Sand shiner 0-5+ Warm Gravel, sand, silt - Intermediate

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Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class

Mimic shiner 0-5 Warm Gravel, sand, silt, clay - Intermediate

Bluntnose minnow 0-2 Warm Boulder, cobble, rubble, gravel, sand, silt 1.05 Intermediate

Fathead minnow 0-2 Warm Cobble, rubble, gravel, sand, silt 2 Tolerant

Creek chub 0-2 Cool Rubble, gravel, sand, silt 2 Intermediate

Fallfish 0-2 Cool Rubble, gravel, sand, silt - Intermediate

Yellow bullhead 0-2 Warm Gravel, sand, silt - Tolerant

Brown bullhead 0-2 Warm Rubble, gravel, sand, silt, clay 1 Intermediate

Channel catfish 0-2 Warm Cobble, rubble, gravel, sand, silt, clay 1.17 Tolerant

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Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class

Tadpole madtom 0-5+ Warm - - Intermediate

Banded killifish 0-5 Cool Rubble, gravel, sand, silt 0.9 Tolerant

American eel 0-5+ Cool Sand, silt - Intermediate

Brook stickleback 1-5+ Cool Gravel, sand, silt 2 Intermediate

White perch 2-5+ Warm Bedrock, boulder, cobble, rubble, gravel, sand, silt, clay - Intermediate

White bass 2-5 Warm Bedrock, boulder, cobble, rubble, gravel, sand, silt, clay - Tolerant

Rock bass 0-5 Warm Bedrock, boulder, cobble, rubble, gravel, sand, silt, clay 2.3 Intermediate

Pumpkinseed 0-2 Warm Rubble, gravel, sand, silt, clay 1.66 Intermediate

Bluegill 0-2 Warm Gravel, sand, silt 1.15 Intermediate

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Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class

Smallmouth bass 1-5 Warm Bedrock, boulder, cobble, rubble, gravel, sand, silt 2 Intermediate

Largemouth bass 0-5 Warm Rubble, gravel, sand, silt, clay 1.92 Tolerant

Black crappie 0-5 Warm Rubble, gravel, sand, silt 2.23 Tolerant

Yellow perch 0-5+ Cool Bedrock, boulder, cobble, rubble, gravel, sand, silt, clay 1.67 Intermediate

Walleye 0-5 Cool Bedrock, boulder, cobble, rubble, gravel, sand, silt - Intermediate

Iowa darter 0-5 Cool Rubble, gravel, sand, silt - Intermediate

Fantail darter 0-2 Cool Boulder, cobble, rubble, gravel, sand, silt - Intolerant

Logperch 0-5+ Warm Boulder, cobble, rubble, gravel, sand, silt, clay - Intolerant

Tessellated darter 0-5 Cool Rubble, gravel, sand, silt - Intermediate

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Depth Thermal DO (mg/L) Tolerance Common name Bottom Substrate (m) guild 50% lethal class

Brook silverside 0-2 Warm Rubble, gravel, sand, silt, clay - Intermediate

Freshwater drum 1-5+ Warm Bedrock, boulder, cobble, rubble, gravel, sand, silt, clay 4.3 Tolerant

Mottled sculpin 0-5+ Cool Boulder, cobble, rubble, gravel, sand, silt - Intermediate

Round goby 0-5+ Cool Boulder, cobble, rubble, gravel, sand, clay - Intermediate

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APPENDIX E

List of reptile and amphibian species occurring in Lake St. Lawrence. Occurrence status sourced from the Ontario Reptile & Amphibian Atlas (Ontario Nature, 2020). Conservation status defined by the Endangered Species Act (2007) of Ontario. Order Family Scientific name Common name Conservation status Anura Bufonidae Anaxyrus americanus American toad Least Concern Hylidae Dryophytes versicolor Gray treefrog Least Concern Hylidae Pseudacris crucifer Spring peeper Least Concern Hylidae Pseudacris triseriata Western Chorus Frog Threatened Ranidae Lithobates catesbeianus American bullfrog Least Concern Ranidae Lithobates clamitans melanota Green frog Least Concern Ranidae Lithobates pipiens Northern leopard frog Least Concern Ranidae Lithobates sylvaticus Wood frog Least Concern Testudines Chelydridae Chelydra serpentina Snapping turtle Special Concern Emydidae Emydoidea blandingii Blanding’s turtle Threatened Emydidae Glyptemys insculpta Wood turtle Threatened Emydidae Graptemys geographica Northern map turtle Special Concern Emydidae Chrysemys picta marginata Painted turtle Under consideration for addition Kinosternidae Sternotherus odoratus Eastern musk turtle Special Concern Urodela Proteidae Necturus maculosus Common mudpuppy Least Concern

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APPENDIX F

Overwintering habitat requirements of adult reptile and amphibian species inhabiting Lake St. Lawrence, with references. Species/ Bottom Oxygen Timing of overwintering Depth Temperature References genera/ taxa substrate requirements habitat use

American toad N/A N/A N/A N/A Adults hibernate on land Miller 1909

Adults hibernate on Gray treefrog N/A N/A N/A N/A Johnson et al. (2008) land, Freeze tolerant Adults hibernate on Spring peeper N/A N/A N/A N/A Layne and Rice (2003) land, Freeze tolerant Western chorus Adults hibernate on N/A N/A N/A N/A Swanson et al (1996) frog land, Freeze tolerant As temperatures get cold More adults will retreat to commonly surface of the sediments American Moderate (can Tattersall and Ultsch found in >0-5oC N/A in shallow water (will not bullfrog tolerate hypoxic) (2008) shallow burrow in sediments). (<0.5 m) Tadpoles are more likely to survive anoxia. As temperatures get cold adults will retreat to surface of the sediments Require ice- Moderate (can Tattersall and Ultsch Green frog >0-5oC N/A in shallow water (will not free water tolerate hypoxic) (2008) burrow in sediments). Tadpoles are more likely to survive anoxia.

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Species/ Bottom Oxygen Timing of overwintering Depth Temperature References genera/ taxa substrate requirements habitat use As temperatures get cold adults will retreat and form small pits in the Northern Moderate (can Tattersall and Ultsch <~3 m >3-5oC N/A sediments where they leopard frog tolerate hypoxic) (2008) will rest. Tadpoles are more likely to survive anoxia. Adults hibernate on Wood frog N/A N/A N/A N/A Layne and Rice (2003) land, freeze tolerant October-Seek out Meeks and Ultsch, 1990; Low shallow waters and Ultsch 2006 Mud (Anoxia-tolerant hibernate in mud at a Obbard and Brooks Snapping Turtle <1m ~0-4oC (clay and but fare better in depth in which they can (1981) silt) well oxygenated breathe during periods Brown and Brooks waters) of ice thaw (1994) In Algonquin Park, turtles start hibernating Blanding’s in October. May bury in Ultsch 2006 .>20-30 cm .>1-2oC Mud Low Turtle mud entirely, or partially Edge et al. (2009) or may rest on the bottom Commence hibernation in late September- Greaves and Litzgus October. Exposed on Northern Wood Muck 2008 0.6-1 m ~0-5oC High river bottom, slowly Turtle and sand Harding and Bloomer exposed by lighter (1979) particles such as silt or clay

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Species/ Bottom Oxygen Timing of overwintering Depth Temperature References genera/ taxa substrate requirements habitat use Ultsch 2006 Hibernate on bottom or Crocker et al. (2000) High wedged among rocks Bernier and Rouleau Northern Map Mud or 0.3-11.3 m >1oC (Anoxia- above the substratum (2010) Turtle Rocky intolerant) could also burrow in Harrison (2011) mud Rouleau and Bernier (2011) Mud Midland Painted Low Ultsch 2006 0.2-0.48m ~3-6oC (clay and Hibernate in mud Turtle (Anoxia-tolerant) Taylor and Nol (1989) silt) Eastern Musk Mud High Various Hibernate on top of Ultsch 2006 Turtle ~3oC (Clay and (Anoxia- (Nearshore) substratum or in mud silt) intolerant) Various Common Ice-free Moderate (can 1.2-2.4 m (prefer Active during the winter Eycleshymer 1906 mudpuppy water tolerate hypoxic) sandy)

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APPENDIX G

List of aquatic mammals occurring in Lake St. Lawrence, with references. Order Family Scientific name Common name Reference Rodentia Castoridae Castor canadensis North American beaver Thorp et al. 2005 Cricetidae Ondatra zibethicus Muskrat Thorp et al. 2005 Carnivora Mustelidae Neovison vison American mink Thorp et al. 2005 Mustelidae Lontra canadensis North American river otter Thorp et al. 2005

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APPENDIX H

Overwintering habitat requirements of aquatic mammal species inhabiting Lake St. Lawrence, with references. Species/ Depth Temperature Bottom Oxygen Timing of overwintering References genera/ substrate requirements habitat use taxa Castor - Water must be <-20C limit for N/A N/A - Beavers forage through Smith and Peterson (1991) canadensis deep enough to above-ice warmer months to store food Ontario Parks (2020) (North store resources activity; underwater to be able to Semyonoff (1953) MacArthur American underwater to thermoneutra have resources for the winter (1989) Beaver) prevent freezing l range 0-28C - Stay put in river, lake or Graf et al. (2018) but shallow pond in lodges (made of enough to mud, sticks and logs); chew support lodge underwater entrance into dry part of lodge to stay warm and dry throughout winter, swim underneath the ice Ondatra - Vegetation 32.1C was N/A N/A - Mounds are constructed in Kangas and Hannan (1985) zibethicus mounds (used average body late summer, early autumn Sherer and Wunder (1979) (Muskrat) as lodges) 30 cm temperature - Feed on plant material MacArthur (1979) or more above for muskrats under the ice in winter water surface exposed to months - Most mounds waters of 5C – - Builds a lodge; typically are found in 0.2- which begins enough room for only one 1m of water onset of high muskrat; chews through ice hypothermia ; to create ‘push-ups’ Muskrats with body temperature of <30C began to show

54

clumsiness and slowed movements; <25C showed immobilizatio n and stiffness – however these individuals would recover Neovison N/A Relatively N/A N/A - Minks dig burrows or use Saunders (1988) vison poor dens (opportunistic) along Bagniewska et al. (2015) (American insulation banks mink) makes mink - Often found den sites of more other animals and is susceptible to associated with muskrats; heat loss; It’s dens underneath abandoned possible that beaver lodges, brush, rocks, there is a hollow logs; during winter lower critical may move away from shore temperature and occupy dens/burrows of where other animals foraging temporarily halts; temperature may also affect diving behavior on a temporal

55

scale (e.g. time of day)

Lontra - Require open Normal body N/A N/A - Otters live in dens McTaggart-Cowan (2007) canadensis water for temperature (opportunistic) along banks American Rivers (2019) Dronkert- (North foraging of 37.5-40C - Live in dens along river that Egnew (1991) American (Upper end are accessible underneath river otter) considered ice; have been known to use pathologic if it beaver lodges and continues. sometimes breach them thus Stress and reducing water levels for capture might easier foraging; make holes also increase in ice and hunt for fish and body temp to crustaceans (e.g. Crayfish) upper range.)

56