Lake Trout Ecosystems in a Changing Environment - Chapter 17 (end) doc

Clark, B.J., Dillon, P.J., and Molot, L.A., 2003, Lake trout Salvelinus namaycush habitat volumes and boundaries in Canadian Shield lakes, in Boreal Shield Watersheds: Lake Trout Ecosyst

Synthesis

chapter seventeen

Boreal Shield waters: models

and management challenges*

The challenge of integrative ecosystem indicators

The challenge of ecosystem sustainability

Acknowledgments

References

This book was designed to address two important questions related to the waters of theBoreal Shield:* (1) Can we effectively manage human interactions with Boreal Shieldwaters and aquatic biota, at local-to-global spatial scales, now and in the future? and (2)Can lessons from Boreal Shield waters and watersheds serve as useful models for otherregions and ecosystems?

Although human behavior has had great influence on Boreal Shield waters, we havelimited ability to constructively affect these exquisitely complex and dynamic systems.Our influences, often harmful, have generally been through gross structural changesinvolving harvest or exploitation of ecological products and services such as fish, trees,hydraulic energy, and waste disposal Our development practices also cause the insidiouscontinued devastation of the shoreline ecotone, which serves as a center of attraction and

* We used the Boreal Shield ecozone, the largest of the 15 ecozones in Canada, as the geographic focus of this

book Boreal or northern forest refers to the mainly coniferous forest that covers most of the northern portion of the ecozone Shield refers to the exposed Precambrian Shield bedrock that extends across the entire ecozone

(Ecological Stratification Working Group, 1995).

to make choices from an array of potentially harmful actions, attempting to select the leastharmful one.

Glacial legacies

In earlier chapters we introduced the idea that Salvelinus namaycush is a northern species

pushed to southern latitudes by the glaciers, then stranded there in freshly gouged lakebasins when the glaciers retreated, water levels declined, and the land began to rebound

We may infer that over time natural forces subsequently eliminated lake trout populationsfrom some of those new habitats, particularly shallow, polymictic lakes; lakes with erodingshorelines and turbid waters; and lakes with high nutrient inputs, where competitors orpredators such as walleye, northern pike, and bass became dominant

Now, 8,000 to 12,000 years later, we see three general types of lake trout lakes on theShield The first is a southern group of very large lakes, including a large portion of theLaurentian Great Lakes In these massive, deep lakes, natural lake trout populations werevertically isolated from most competitors and predators, and were extremely abundant inall of these lakes until about 60 to 90 years ago Availability of deep-water habitats in theLaurentian Great Lakes may also have favored the development of distinctive sympatricstocks or morphotypes

The second type is a group of intermediate-latitude lakes (i.e., boundary watersbetween Minnesota and Ontario, central and northern Ontario and southern Quebec)consisting of relatively shallow dimictic lakes (10 to 100 m) that generally provide well-oxygenated hypolimnia in the summer The largest and deepest of these lakes oftensupport diverse fish communities In the shallowest of these lakes, lake trout populationsare generally small and in constant jeopardy of exclusion by competing species andoverharvesting by humans

The third type is a group of lakes north of the Boreal Shield ecozone (i.e., from northernQuebec and Labrador to Alaska) that includes several very large lakes, but also manysmall and shallow polymictic lakes where summer water temperatures are cool enough

to support lake trout Generally, fewer species exist in the most northerly lakes

A recent example of colonization

Although derived from a relatively small geographic area, the recent findings from bury, Ontario serve to recapitulate and illustrate some of the postglacial lake trout historyoutlined above

Sud-Acid deposition from the Sudbury nickel smelters, the largest point source of SO2 inthe world in 1960, exterminated lake trout and many associated biota from nearly 100lakes near Sudbury during the 1960s and early 1970s Fortunately SO2 emissions havebeen reduced by about 90% since 1960, resulting in water quality improvements in manyformer lake trout lakes (Gunn and Keller, 1990) Many lakes are still seriously damagedand further SO2 reductions are required, but fishery rehabilitation projects have begun;preliminary results are both encouraging and illuminating (Gunn and Mills, 1998) Forexample, reestablishment of reproducing lake trout populations has proven to be verydifficult in lakes with abundant competitors or predators (bass, walleye, whitefish, etc.),but almost routine in lakes with relatively simple fish communities (Hitchins and Samis,1986; Gunn et al., 1987; Evans and Olver, 1995) The availability of spawning sites does

not appear to be a limiting factor in these recovering lakes or for that matter in most otherShield lakes; newly established populations appear to quickly find enough suitable sub-strate sites for egg deposition (Gunn, 1995) When lake trout are restocked in very warmshallow lakes, the fish die in years with particularly warm summers (Gunn, 2002) Whenthe watersheds of former lake trout lakes are heavily urbanized and the lakes are polluted

by nutrient-rich stormwater runoff, oxygen levels decline in deep water habitats, spawningshoals are fouled with attached algae, reproduction is lost, and recolonization fails Whenangling harvest is uncontrolled and excessive, lake trout populations are jeopardized aswell (Gunn and Sein, 2000)

Modern threats

These histories and our recent observations suggest that lake trout face four major threats

in the 21st century (Loftus and Regier, 1972; Evans et al., 1991; Ryder and Orendorff, 1999):

1 Overexploitation (lakes are relatively unproductive; fish are easy to catch)

2 Cultural eutrophication (loss of suitable hypolimnetic and reproductive habitat)

3 Introduction of invasive species (often via bait buckets)

4 Climate warming (lake trout in small, shallow lakes in northern areas are able to increased summer water temperatures; warm-water competitors increase

vulner-in abundance)

The challenge of integrative ecosystem indicators

Lake trout become large, long-lived, and both ecologically and commercially valuable toppredators in healthy environments As such they have attracted great interest as integrativeindicators of the health of Shield catchments and atmospheric conditions (Maitland et al.,1981; Ryder and Edwards, 1985; Marshall et al., 1987) The existence of robust, high-qualitynative lake trout populations clearly tells us that something is right about the biosphere

in general and Boreal Shield waters in particular For example, where lake trout thrive wemay infer that the various physical, chemical, and cultural stressors identified in Table 17.1

and emphasized throughout this book are inactive, active at low levels, or active but recent.Where lake trout are declining or threatened, we may conclude that chronic or unsustain-able stresses are active

Human activity influences forests and waters directly and indirectly over large andsmall spatial scales (Table 17.1) There is considerable variation in the quality of scientificunderstanding about these influences, and as might be expected, large-scale impacts tend

to be associated with greater uncertainty Complex, multiscale threats to lake trout watersare difficult to identify, quantify, predict, and mitigate For this reason, managers andresearchers have explored integrative surrogate indicators, such as lake trout, capable ofproviding diagnostic, quantitative, advance warning of impending degradation of Shieldecosystems This evolution was spurred in part by regulatory guidelines that specifiedprotection of “biotic integrity” as required by the 1972 U.S Federal Water Pollution Control(“Clean Water”) Act, the 1978 Great Lakes Water Quality Agreement, and the CanadianNational Parks Act

Although a wide range of physical, chemical, and biotic indicators have been proposedfor ecosystems, few have been implemented by management agencies Unfortunately, theproblems associated with finding practical, affordable, and technically unambiguous indi-ces still appear rather intractable Nonetheless, the scientific studies and debates associatedwith these various initiatives have greatly increased our knowledge and our recognition

of the complexity of these ecosystems (Ryder and Orendorff, 1999)

of cool- and warm-water species

Weak to moderate

Refers to recent climate impacts caused by human activity

extinction of aquatic biota, bioaccumulation of mercury and persistent organic contaminants

Good

Strong potential interaction with Stressors 1 and 4 via dissolved organic carbon and water transparency

4 Non-point-source

land use and

forest disturbance

hypolimnetic oxygen depletion, contamination, biotic impairment

agriculture > forestry, wildfire

hypolimnetic oxygen depletion, contamination, behavioral changes, biotic impairment, local extinction

tailings ponds, municipal sewage treatment plants; includes discharge of heated water from thermal power plants

7 Impoundment,

dewatering, or

diversion

habitat, impaired reproduction, local mercury methylation

regime

8 Shoreline or basin

modification

nutrient loading, burial of lake or stream

Good For instance, road construction, mines or tailing ponds, cottage

development; includes impacts described in Stressor 4

local extinction

Source: After Regier (1979) and various chapters in this book.

For the last 50 to 80 years researchers have used Shield lakes as models in their studies

of aquatic ecosystem response to disruption by human activities As a result, many humaneffects on Shield waters are well documented and are at least partially predictable in anempirical or qualitative sense (Table 17.2) Many of these studies highlight the importance

of catchment morphology and disturbance regimes and confirm the importance of term monitoring, comparative studies, and ecosystem experiments A major challenge thatremains is the need to develop useful diagnostic information when confronted withmultiple stressor interactions We now recognize that ecosystems are typically influencedsimultaneously by multiple stressors, each potentially associated with quite similarresponses from lake trout populations (Rapport et al., 1985) Lake trout may for instance

long-be simultaneously subjected to harvest, habitat disruption, persistent contaminants, andintroduction of exotic aquatic species All of these stresses may contribute in part to areduction in lake trout reproductive success and ultimate population size (Evans et al.,1991)

The science summarized in Table 17.2 spans spatial scales from local to biospheric(global) Model outputs (e.g., descriptions such as those that deal with thermal structure,water chemistry, composition of biotic assemblages, and lake trout demographics are butfour examples) may be useful in some contexts as direct indicators of lake trophic status

or as surrogates of large-scale (e.g., ecozone or landscape) phenomena The most tative models tend to be regional in scope and relevant primarily to water yield and waterquality rather than to habitat and biota (Carignan and Steedman, 2000) Some of thesemodels (e.g., Ryder, 1965; Dillon and Rigler, 1975) have been used at various times asformal regulatory or assessment tools

quanti-Some recent findings suggest that lake trout lakes may be less responsive to certaintypes of watershed disturbances than previously thought Water renewal times for deepShield lakes, where lake volume is large relative to catchment area, may range from adecade or so for small headwater lakes, to a century or more in the case of Lake Superior.This combination of lake morphology and drainage position creates significant hydrologic,thermal, and chemical inertia that may protect lake trout lakes to some degree Forexample, temporary catchment disturbances that alter runoff hydrology or chemistrytypically exert only small annual influences on lake trout lakes, and these effects maydissipate before the lake responds significantly (Schindler et al., 1980; Carignan et al., 2000;Steedman, 2000) In contrast, the serious consequences of chronic watershed disturbancehave been repeatedly and thoroughly documented (in this volume, Legault et al [Chapter

5], Driscoll et al [Chapter 10], Krueger [Chapter 10], Steedman et al [Chapter 4]) Slowwater renewal rates may also delay the recovery of lakes from contaminant spills (alsoairborne contaminants) and can also increase the exposure and breakdown of DOC (dis-solved organic carbon), leading to increased clarity and deeper penetration of solar radi-ation, including ultraviolet (UV) radiation (Schindler et al., 1997)

Boreal Shield ecosystems are among the best-studied natural ecosystems on earth,especially from a hydrological and geochemical perspective However, there are still manychallenging research questions to pursue, particularly when we try to understand the linksbetween the physical and the biotic components For example, Boreal Shield ecosystemsare effective at collecting persistent organic pollutants (POPs) on the waxy surfaces ofconiferous trees (Wania and McLachlan, 2001) However, the chronic effects of these tracecontaminants on the biota are poorly understood So, too, and perhaps more surprising,

is the lack of quantitative information on the role of the littoral zone in the productivityand energy dynamics on Boreal Shield lakes In fact, ecologists are just beginning todescribe the community composition of some of the dominant species in the littoral zone,such as the species-rich microcrustaceans (Walseng et al., 2003) Important ecologicalevents such as the annual ice melt (Figure 17.1), which may trigger and structure much

long-Average annual temperature, land cover, precipitation

Various physical and biological attributes of lakes (ice cover duration, water renewal times, dissolved organic carbon, airborne contaminants in biota)

Magnuson et al (1990); Schindler et al (1990, 1996); Shuter and Meisner (1992); Yan et al (1996); Snucins and Gunn (1995); Schindler (1998, this volume)

biodiversity:

distribution of fish species

Lake area, latitude, biogeography

Fish species richness and community composition

Matuszek and Beggs (1988); Matuszek et al (1990); Minns (1989)

Lake morphometry, productivity, pH, alkalinity, conductivity

Lake trout presence Conlon et al (1992); Gunn and

Keller (1990); Ryan and Marshall (1994); Driscoll et al (Chapter 10, this volume); Mills et al (2000)

land (water, carbon, nutrients, forest litter, sediment)

Ontario Trophic Status and refinements

Lake P budget (from catchment geology and land use, aerial deposition, sedimentation)

Water clarity (chlorophyll and Secchi depth)

Dillon and Rigler (1975); Hutchinson et al (1991); Dillon et al (1991, Chapter 7, this volume); Beaty (1994); Bayley et al (1992); Snucins and Gunn (2000)

Water quality in lakes with burned and logged catchments

Catchment disturbance, lake morphology

Concentration of dissolved nutrients, carbon, cations

Carignan et al 2000; Steedman (2000); Knapp et al (2003); Lake morphometry, catchment

morphometry, and drainage patterns

Concentration of dissolved organic carbon

Rasmussen et al (1989); Schindler et al (1997); Molot and Dillon (1997)

Ontario summer oxygen profile

end-of-Lake morphometry, total phosphorus, dissolved oxygen

accumulation in aquatic biota

Watershed slope, forest disturbance, reservoir age, lake and watershed morphology, fish species and size, sediment characteristics

Mercury concentration in zooplankton and fish

Garcia and Carignan (1999, 2000); Bodaly et al (1984), Chapter 9, this volume; Jackson (1991); McMurtry et

al (1989); Legault et al (this volume)

Lake 1–100 Benchmark

expectations for fish production

Morphoedaphic index (MEI) and refinements

Mean lake depth, total dissolved solids, thermal habitat volume

Long-term commercial fishery harvest (large lakes)

Ryder (1965, 1982); Christie and Regier (1988); Shuter et

al (1998) Effects of angling,

introductions of exotic species

Lake morphometry, temperature profiles, angler effort and harvest, age-structured mortality and growth rates

Maximum sustained yield, allowable yield; production, structure, and dynamics of lake trout populations

Payne et al (1990); Shuter et al (1998); in this volume, Lester and Dunlop, Chapter 16, Vander Zanden et al.; Chapter 13, Gunn and Sein (2000)

Shoreline disturbance Shoreline disturbance by logging

Littoral sedimentation Steedman and France (2000) Littoral fish populations Steedman (2003)

The role of UV radiation and PAR (photosynthetically active radiation) in habitat use, theuse of thermal refuge areas, the impact of invasive species, the effect of climate warming

on lake productivity … the research challenges, both old and new, remain

The challenge of ecosystem sustainability

Given the high frequency of fire and insect outbreaks in the boreal forests and the glacialhistory of this region, Shield ecosystems may seem quite resilient It is not known whatthese ecosystems were like in the interglacial periods, but it is probably safe to assumethat each time the “slate was wiped clean” due to glacial action, functional ecosystemsreestablished themselves The individual Shield ecosystems seen today are therefore onlyone part of a temporal series of ecosystems that existed at this site, and the presentconditions are in fact quite young in geological time, from a few decades or centuries to

at most 12,000 years The soils are also young, an interesting feature that Wright (2001)considered important in the high resilience of glaciated areas from the impacts of airpollutants (SO2) In catchments lacking this glacial history, soils are older, and sulfur isstrongly absorbed to iron and aluminum sesquioxides, making these nonglaciated systemsslow to recover The terrestrial flora and fauna of Boreal Shield ecosystems have manywell-known adaptations to disturbances such as fire, but the aquatic biota also exhibitmany specialized adaptations to changing conditions For example, many zooplanktonhave resting stages that can remain dormant for decades or centuries until conditionsimprove (Hairston et al., 1995) Fish migration also occurs among connected lakes, oftenwith surprising ease for some species (Jackson et al., 2001)

Boreal Shield ecosystems may therefore prove to be more adaptable to changingconditions than we might have originally expected, but one aspect of their identity appearsunchangeable: they contain relatively low-productivity waters Attempts to increase laketrout production by modifying habitat features (such as creating or cleaning spawningsites) are therefore destined to fail Unfortunately, hundreds of these so-called enhance-ment projects have been conducted in lakes where the real management problem is

excessive lake trout harvest, cultural eutrophication, or the impact of introduced species.Some people may argue that such habitat enhancement projects are still useful becausethey encourage public involvement in fisheries management and conservation However,ineffective habitat enhancement projects more likely simply delay development of scienceand policy addressing the real problems and discourage the well-intentioned volunteerswhen they see that nothing comes of their efforts.

The inherently limited productivity of Shield waters also constrains the usefulness ofother management actions such as hatchery stocking Stocking may be necessary forrehabilitation purposes when a particular species has been extirpated from a lake, butwhen used in an attempt to supplement depressed natural populations it can often domore harm than good (Evans and Willox, 1991) For example, it can create highly unreal-istic public expectations and thus increase fishing pressure to the point that irreplaceableremnant stocks of native fish are lost along with the introduced fish Genetic introgressionand disease transmission may be additional undesirable side effects of inappropriatestocking efforts (Powell and Carl, Chapter 12, this volume)

Rather than focus on how more lake trout can be produced, our desire should be toraise the value of the lake trout we have (Figure 17.2) One way to do this is to celebratetheir role as environmental sentinels What we are suggesting here is that the lake troutcan be the “miner’s canary” of Boreal Shield lakes, a species with narrow environmentaltolerances (stenoecious species) that can serve as an early-warning signal for the ecosys-tem As the largest and longest lived of the salmonid fishes native to the Shield, the laketrout also provides a longer term record because it carries within its body a physical andchemical history of the Boreal Shield environment (Figure 17.3) One of the most compel-ling of these stored signals is mercury body burden (Figure 17.4), which in recent yearshas been recognized as significantly affected by long-range atmospheric transport anddeposition of fossil fuel emissions that originate far beyond Boreal Shield watersheds.Lake trout in many lakes exceed mercury consumption guidelines, even in the absence oflocal watershed disturbance Due to its preference for deep, clear lakes, the lake trout isnot always the most contaminated fish species (i.e., see walleye in Figure 17.4) in BorealShield waters However, this does not mitigate the fact that distant human activity haspolluted hundreds of lake trout lakes and other Boreal Shield lakes via this mechanism

If we look ahead 100 or perhaps 500 years into the future, there is no doubt that laketrout ecosystems of the Boreal Shield will still be highly valued by humans but perhapsfor different reasons In future centuries urbanization and other demographic changes(e.g., depopulation of many northern towns) will likely continue, and participation levels

in fishing and hunting may decline, but humans will no doubt still passionately valuethis landscape The value of Boreal Shield ecosystems as sources of nutritious food willlikely remain, and the importance of these ecosystems for clean drinking water, energy,and fiber will likely increase enormously, as will their value for recreation, art, and escapefrom the hectic urban life The fact that we cannot imagine what this future will be simplyreinforces the need to implement effective monitoring and conservation programs now tohelp protect this landscape

Finally, it needs to be recognized that the often-repeated comment that the “fishing

is not as good as it used to be” is not just a memory lapse Overfishing and habitatdegradation have occurred (Post et al., 2002), invading species (including humans) havearrived from all over the world, and climate changes are occurring with unknown effects(Schindler, 1998) Boreal Shield ecosystems are not static and in many ways may not beconsidered particularly fragile, but they need proactive and adaptive protection now Wecannot expect to “manage” these ecosystems in the same way or with the same controlthat we might try to manage a business However, new information about the mostimportant, tractable problems can be used to develop a healthier and more sustainable

relationship with Shield ecosystems The lake trout was an influential spiritual and

scien-tific icon during many years of public outcry to reduce acid rain We hope that Salvelinus namaycush will continue to rally new science and recovery efforts addressing overharvest,

pollution, harmful shoreline development, and other human activities that threaten theintegrity of Boreal Shield waters (Figure 17.5)

Figure 17.3 Age interpretation from an acetate replicate from a transverse section of an otolith from

an age 11+ lake trout (65.9 cm total length, 2600 g male) In addition to detailed information on ageand growth, new advances in chemical probe analyses are revealing much about the past environ-ment of the fish from the records stored in otoliths and other calcified tissues (Photo from

J Casselman.)

We thank Jake Vander Wal, Bill Keller, Ed Snucins, Nigel Lester, and Terry Marshall formany thoughtful discussions of the topics discussed in this chapter Al Hayton of theOntario Ministry of the Environment kindly provided the mercury data for Figure 17.4.Carissa Brown and Christine Brereton assisted with all aspects of the book production

Figure 17.4 Inland lakes in Ontario where some of the larger or older lake trout and walleye exceedthe Canadian marketing limit of 0.5 µg/g for mercury The percentage of sampled lakes with mercuryexceedances is indicated (Data from the Ontario Ministry of the Environment.)

Figure 17.5 Reproducing lake trout, an icon for ecosystem sustainability (Photo by S Skulason.)

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section VI

Long-term monitoring sites

on the Boreal Shield

Long-term monitoring programs are essential to identify the rate and direction of ronmental change in the Boreal Shield ecozone Canada’s Ecological Monitoring andAssessment Network (EMAN; www.eman-rese.ca) currently provides a coordinating ser-vice to support data sharing, communication, and training in environmental and ecologicalmonitoring and to assist in preparing state-of-the-resource assessment reports (e.g.,Urquizo et al., 2000) Brief descriptions and maps of some of the key monitoring sites inthe southern and southwestern Boreal Shield ecozone are given here For more information

envi-on menvi-onitoring sites in the eastern part of the ecozenvi-one see, http://eqb-dqu.cciw.ca/eman/network/borshque.htm

Experimental Lakes Area

The Experimental Lakes Area (ELA) (Figure A1.1) was established in 1968 and is located

in northwestern Ontario approximately 250 km from Winnipeg and 50 km east-southeast

of Kenora The ELA includes 58 small lakes (with areas 1 to 84 ha) and their drainagebasins, plus three additional stream segments set aside and managed through an agree-ment between the Canadian and Ontario governments For an additional description of

the site see the ELA special issue of the Journal of the Fisheries Research Board of Canada

[28(2), 1971] Descriptions of current projects and listings of research papers are availableonline at www.umanitoba.ca/institutes/fisheries/ELApubln.html

Turkey Lakes Watershed

The Turkey Lakes Watershed (TLW) Study was initiated in 1980 to evaluate anthropogenicperturbation of Canadian Shield ecosystems (e.g., the effects of acidic deposition) Thebasin is located in the Algoma District of central Ontario about 50 km north of Sault Ste.Marie It is an undeveloped and completely forested headwater basin with an area of10.5 km2; it contains a chain of four lakes (five distinct lake basins) that ultimately draininto Lake Superior via the Batchawana River (Figure A1.2) Comprehensive records ofmeteorological and surface water physical and chemical data have been maintained fromthe study’s inception with biological data collected since the mid-1980s For additionalinformation on the physical, chemical, and biological characteristics of the TLW andresearch activities, participants, databases, and the like plus a searchable list of the more

Figure A1.1 ExperimentalLakes Area (ELA).

than 280 associated publications, see the Turkey Lakes Watershed study Web site at

www.tlws.ca There have been three special volumes of TLW publications: Canadian Journal

of Fisheries and Aquatic Sciences [45(Suppl 1), 1988]; Ecosystems [4(6), 2001]; and Water, Air and Soil Pollution: Focus [2(1), 2002].

Killarney Park

A chemical and biological monitoring program of 21 remote lakes in Killarney Park(Figure A1.3) was established to study the interaction of major stressors such as acidifica-tion, climate change, and metal deposition Data records began in the 1970s, with someassociated university research projects beginning in 1967 Killarney Park contains some

of Canada’s clearest waters, which are highly sensitive to climate-driven drought effects.Information on recent studies conducted under the Canada/Norway Northern Lakes

Recovery Study at Killarney is provided in a special issue of Ambio [32(3), 2003].

North-Temperate Lakes Long Term Ecological Research

The North-Temperate Lakes Long Term Ecological Research (LTER) site, housed at theCenter of Limnology — Trout Lake Station (University of Wisconsin–Madison)(Figure A1.4), is 1 of 24 LTER sites across the United States Trout Lake Station wasestablished in 1925 by Birge and Juday, two of North America’s limnological pioneers.With long-term predictive regional ecology as the focus, intensive data collection began

on seven LTER lakes in 1981 and continues More information on the lakes, currentresearch, and online data catalogue is available at http://limnosun.limnology.wisc.edu/

Sudbury area lakes

Monitoring of lakes in the Sudbury, Ontario, area (Figure A1.5) began in the early 1970s,and additional study lakes were added in the 1980s Monitoring includes regular samplingfor chemistry, zooplankton, and phytoplankton on 15 lakes that vary in surface area from5.8 to 315.8 ha Studies of fish and benthic invertebrates are also completed periodically onsome of these lakes The lakes are within the (17,000 km2) area historically affected by theSudbury smelter emissions, but vary greatly in their initial degree of damage, ranging fromthe highly acidic, metal-contaminated lakes close to Sudbury to acidified, undevelopedlakes in more remote areas (e.g., within Lady-Evelyn Smoothwater Park) Studies haveprimarily focused on recovery processes as the lakes respond to about 90% reduction inatmospheric deposition of sulfur and metals since 1960 More recently other stressors,including climate change, exotic species, and depletion of base cations, have been empha-

sized The Canadian Journal of Fisheries and Aquatic Sciences [49(Suppl 1), 1992] and

http://laurentian.ca/biology/ecologyunit.html provide additional information

Dorset Environmental Science Centre

Eight lakes with 20 inflowing tributaries, 8 outflows, and 20 small catchments (10 to 200ha) in mixed deciduous-coniferous forests with extensive wetlands have been monitored

by the Dorset Environmental Science Centre (Figure A1.6) since 1975 to assess the effects

of environmental stresses (e.g., climate change, greenhouse gases, acid deposition, nutrientenrichment, mercury and other trace metals, ultraviolet radiation) on aquatic ecosystems.The lakes are located in south-central Ontario where the primary industry is tourism

Figure A1.4 North-Temperate Lakes Long Term Ecological Research (LTER) Trout Lake Station.

Figure A1.6 Dorset Environmental Science Centre.

Harkness Laboratory of Fisheries Research

Harness Laboratory of Fisheries Research is located on 5154.2-ha Lake Opeongo in quin Park, Ontario (Figure A1.7) It is Canada’s oldest freshwater research station with aprime focus on fish ecology Since 1936, an ongoing census of angler’s catch (lake troutand smallmouth bass) has been maintained continuously for Lake Opeongo The datasupport analyses of long-term trends in growth, production, and population dynamics oftwo species (Shuter et al., 1987) Other long-term data sets focus on reproductive timingand production of young and age and growth patterns in other species for the last 10 to

Algon-20 years

Figure A1.7 Harkness Laboratory of Fisheries Research.

cropterus dolomieu), 1963–83, Can J Fish Aquat Sci., 44(Suppl 2):229–238.

Urquizo, N., Bastedo, J., Brydges, T., and Shear, H., 2000, Ecological Assessment of the Boreal ShieldEcozone, Indicators and Assessment Office, Environment Canada, Ottawa Available online

at www.ec.gc.ca/soer-ree/english/default.cfm

appendix two

Lake trout lakes of the Boreal Shield

ecozone of North America

Lake trout lakes are listed alphabetically for the jurisdictions of Minnesota, New York(Adirondacks), Ontario (Northeastern, Northwestern, South Central) and Quebec TheLaurentian Great Lakes and 33 other large lakes (>10,000 ha), many of which cross juris-dictions, are not included Alternate names are listed in parentheses, and a separate entry

is given for each name Lakes with the same name are ordered by latitude This atlas isconsidered an accurate list of lake trout lakes in these jurisdictions at the time of publica-tion; however many other lake trout lakes may be discovered in the future, particularly

in parts of Quebec where less extensive surveys have been conducted In addition, otherlake trout lakes exist in the Shield bedrock regions of Alberta, Manitoba, Michigan,Saskatchewan, and Wisconsin These areas are part of the Boreal Shield ecozone, but theselakes are not yet included in the atlas

Lake names and descriptions were obtained from lake management agencies fromMinnesota, New York, Ontario, and Quebec (see acknowledgment section for contactnames) in 1998 The data was obtained from surveys conducted by government agenciesand universities over a period of several decades The most recent data was generallyused but with the sampling period duration and the wide variety of methods and datasources, the descriptions for parameters such as Secchi depth or specific conductanceshould be considered as approximations The current status (e.g origin, reproduction,abundance) of the lake trout populations in many of these lakes is also uncertain.With the large Ontario data set we attempted to update and verify the earlier data.Longitude and latitude of all Ontario lakes were checked by plotting each lake using 2000Softmap: Ontario Top50 software (Softmap Technology, Inc.) Calculated centroids wereused as the point of location of the lake Location points were manually moved to thelargest basin of the lake if the centroid missed the lake surface Because of the large number

of lakes with similar names, unique waterbody identification codes (OFIS codes) wereadded by adopting the codes assigned by Ontario Ministry of Natural Resources (OMNR)through their Ontario Fisheries Information System (OFIS) Blanks indicate that no OFIScode has yet been assigned Arcview GIS 3.2 software was used to calculate surface areasfor approximately 500 lakes with missing data from the OMNR Natural Resources ValuesInformation System (NRVIS) At the time of publication (June 2003) there were still about

100 Ontario lakes from previous lake trout lists where the locational data could not beverified and the lakes were excluded from this atlas

Bear Pond 44°24′06″ 74°17′11″ 21.9 18.3 6.8 24 11

Tupper 44°12′13″ 74°28′39″ 1713.6 27.4 38 5

ONTARIO (Northeastern Ontario)

Surface area (ha)

Maximum depth (m)

Mean depth (m)

Conductivity (µS/cm)

Secchi depth (m)