AN ABSTRACT OF THE THESIS OF
Nicola L.Swets for the degree of Master of Science in
Fisheries Science presented on June 24, 1996.
Title: Age, Growth, and Diet of Fish in the Waldo Lake
Natural-Cultural S Redacted for Privacy
Abstract approved priam J.Liss
Waldo Lake, located in the Oregon Cascades, is considered to be one of the most dilute lakes in the world. Even with very low nutrient concentrations and sparse populations of zooplankton, introduced fish in the lake are large in size and in good condition when compared to fish from other lakes. Fish were originally stocked in Waldo Lake in the late 1800's. The Oregon Department of Fish and Wildlife began stocking in the late 1930's and continued stocking until 1991. Species existing in Waldo Lake today include brook trout, rainbow trout, and kokanee salmon. The overall objective of this thesis was to increase the understanding of the interrelationships that affect the age, growth, and diet of fish in Waldo Lake. The specific objectives were to summarize and synthesize available information on the substrate, climate, water, and biota of the Waldo Lake Basin; describe the cultural history and current cultural values of the Waldo Lake Basin; determine the age, growth, length, weight, condition, diet, and reproduction of introduced fish species in Waldo Lake; interrelate the above information to show how these components of the natural-cultural system are related. Fish were collected one week per month from early June through mid-October in 1992 and 1993. Variable mesh experimental gillnets set in nearshore areas were used to capture fish in 1992. During the 1993 sampling period, experimental gillnets and trapnets were set in the nearshore areas of the lake. Relative age specific growth rates of brook trout in Waldo Lake are comparable to brook trout growth rates in other lakes. Brook trout growth rates generally decreased with age, however, there were no significant differences in the growth rate of each age class between 1991 and 1993. The condition of brook trout in Waldo Lake is also comparable to brook trout in other lakes. The same is true for rainbow trout and kokanee salmon. Fish in Waldo Lake are large in size and in good condition due, in part, to the availability of benthic macroinvertebrates. Taxa found in stomach contents of fish captured in Waldo Lake consisted primarily of aquatic benthic macroinvertebrates, but terrestrial vertebrates and vertebrates, although infrequently consumed, were also part of the total diet. Rainbow trout in Waldo Lake consumed primarily chironomidae larvae and pupae although odonata larvae, ephemeroptera larvae, and amphipods were also consumed. Kokanee salmon fed almost exclusively on chironomid larvae although small numbers of ephemeroptera larvae, odonata larvae, and coleoptera were also consumed. The most important macroinvertebrate taxon consumed by Waldo Lake brook trout was chironomid larvae and pupae, although other species also were important. The diet of Waldo Lake brook trout varied in a complex way that appeared to be related to the relative abundance of macroinvertebrate taxa, feeding location in the lake, and time of year. Brook trout diet also varied by size class. The components of the Waldo Lake natural-cultural system are complexly interrelated and the nature of these relationships are constantly changing. Each component in some way affects and is, in turn, affected by each of the other components. Changes in some components, such as substrate, affect other components along geologic time scales. Other components, such human culture and biota, may change rapidly within a decade. The capacity of natural-cultural systems, such as Waldo Lake, to change over time makes it possible to view the present state of the system only as a snapshot in time. This dynamic nature of the Waldo Lake natural-cultural system is not unique to Waldo Lake, but is expressed in all natural- cultural systems. Age, Growth, and Diet of Fish In the Waldo Lake Natural-Cultural System
by
Nicola L. Swets
A THESIS
submitted to
Oregon State University
in partial fulfillment of the requirements for the degree of
Master of Science
Presented June 24, 1996 Commencement June, 1997 Master of Science thesis of Nicola Lyn Swets presented on June 24, 1996
APPROVED:
Redacted for Privacy sor, representing Fisheries Science Redacted for Privacy
Chair of Depar Fisheries and Wildlife
Redacted for Privacy
Dean of G ate School
I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request.
Redacted for Privacy
Nicol Lyn Swets ACKNOWLEDGEMENTS
I wish to express my sincere appreciation to Dr. Gary Larson and Dr. Courtland Smith for serving on my graduate committee and providing insight throughout this process. Special thanks go to Dr. William Liss for his help in the various iterations of the preparation of the thesis and for the encouragement to stay on course, even when others did not see things in the same way that I did. I also wish to thank the employees of the Willamette National Forest who were patient with me as I juggled working full time and completing this thesis. Without these individuals, this accomplishment would not have been possible. Finally, I am most indebted to my family, to my parents Roger and Ellen Swets who always told me that anything is possible with hard work (an idiom that is perhaps idealistic, but which I still, and forever will believe), and to my husband Brian, who provided unending support and the encouragement necessary for me to fulfill this dream. TABLE OF CONTENTS
Page INTRODUCTION 1
COMPONENTS OF THE WALDO LAKE NATURAL-CULTURAL SYSTEM 9
Substrate 9
Geologic History 9 Basin and Lake Morphometry 11 Basin Substrate 11 Lake Substrate 13
Climate 13
Precipitation 14 Air Temperature and Solar Radiation 14 Wind Speed and Direction 14
Water 14
Water Chemistry 15 Other Limnological Information 16
Biota 17
Phytoplankton 17 Zooplankton 18 Benthic Macroinvertebrates 19 Terrestrial Macroinvertebrates 23 Amphibians 26 Allochthonous Input 26 Autochthonous Organic Material 29
Human Culture 30
History of human Culture Component 30 The Introduction of Fish to Waldo Lake 34 Fishing Pressure 34 Conflicting Values 36 The Values 37 Protectionists and Naturalists 37 Multiple Use Advocates 38 TABLE OF CONTENTS (Continued)
AGE, GROWTH, AND DIET OF FISH IN WALDO LAKE 40
Methods 40
Fish Capture 40 Age and Growth 41 Condition 42 Diet 43 Reproduction 44
Results 45
Fish Capture 45 Age and Growth 45 Condition 49 Diet 53 Reproduction 63
Discussion 66
Waldo Lake: A Complex, Dynamic Natural- Cultural System 66 Age, Growth, and Condition of Fish in Waldo Lake 72 Diet of Fish in Waldo Lake 73 Reproduction of Fish in Waldo Lake 76
BIBLIOGRAPHY 78 LIST OF FIGURES
Figure, Page
1. A natural-cultural system symbolized in terms of its primary and secondary subsystems 6
2. The Waldo Lake Basin and the Waldo Lake Wilderness boundary 7
3. The natural-cultural system entailing compositional hierarchy of human culture, climate, biota, water, and substrate. The environment of the natural-cultural system 8
4. A bathymetric map of Waldo Lake 10
5. Fish sampling locations in Waldo Lake and its tributaries and outlet 12
6. Comparison of growth rates from recaptured fish of known age and from back-calculated age from otoliths of brook trout captured between 1991 and 1993 48
7. Average relative growth rate by year for Waldo Lake brook trout 50
8. Mean relative growth rates as determined from otolith analysis for Waldo Lake brook trout (1991-1993) compared to relative growth rates of brook trout from other lakes 51
9. Percent occurrence of taxa observed in the stomach contents of fish captured from Waldo Lake (1991-1993) 54
10. Location of prey items of Waldo Lake
brook trout, rainbow trout, and kokanee salmon . . 57
11. Percent of taxa observed in Waldo Lake brook trout stomach contents (1991-1993) 58
12. Location of prey items of Waldo Lake brook trout . 59 LIST OF FIGURES CONTINUED
Figure Page 13. The relative abundance of aquatic macroinvertebrate taxa collected from nearshore and offshore areas (1992-1993) 61,62
14. The percentage of taxa observed in the stomach contents of two size classes of brook trout (1991-1993) 64
15. Location of prey items of two sizes of Waldo Lake brook trout 65
16. A food web focusing on the biotic component of the Waldo Lake natural-cultural system 70 LIST OF TABLES
Table Page
1. Macroinvertebrate taxa collected from nearshore microhabitats and offshore areas of Waldo Lake, 1992-1993 21
2. The number of taxa and the percent of the total taxa collected in the nearshore microhabitats, 1992 and 1993 22
3. The presence of nearshore macroinvertebrates from late May through early October) 24,25
4. Visitor use days at Waldo Lake Campgrounds from 1969 to 1992 32
5. Waldo Lake recreation use data 33
6. Number of fish stocked by the Oregon Department of Fish and Wildlife in Waldo Lake, Oregon 35
7. Number of fish captured and the number of otoliths examined by species and year 46
8. Comparison of average growth rates and average relative growth rates between the marked 1988 cohort and the backcalculated length of fish captured in 1991-1993 47
9. Mean Fulton-type condition factor of fish in Waldo Lake compared to fish in other lakes .... 52
10. Taxa found in the stomach contents of fish collected from Waldo Lake in 1992 and 1993 55
11. A matrix for the Waldo Lake Basin showing the interrelationships between the components of the natural-cultural system 67,68 Age, Growth, and Diet of Fish in the Waldo Lake Natural-Cultural System
INTRODUCTION
"The lake stretches away to the north; crags and peaks tower above us. It is a splendid scene - this source of rivers and cities, hid away, like pure trains of thought from vulgar observation - in the bosom of the wilderness buried." Judge John Beckenridge Waldo(1890)
Waldo Lake is considered to be one of the most dilute (ultraoligotrophic) lakes in the world based on chemical and biological characteristics of the pelagic zone (Larson and Donaldson 1970, Larson 1972, Maleug et al. 1972). Oligotrophy implies that biological production in the lake is restricted by relatively low concentrations of dissolved nutrients (Goldman and Horne 1983). The concentrations of ions, conductivity, and alkalinity in the lake are within the range of those measured from snow samples taken from the basin (Maleug et al. 1972) and are similar in composition to rainwater in a pristine environment (Johnson et al. 1985). Larson (1970) compared the water chemistry of Waldo Lake to distilled water because of the low concentrations of nitrogen, phosphorous, and carbon. Inorganic nitrogen concentrations reported by Larson and Salinas (1995) were below the level of detection(1.0 p./1) during most sampling efforts. Ammonia concentrations were more variable (,1.0 to 19 11/1)(Larson and Salinas 1995). Both total and organic phosphorous concentrations are very low (<5 11/1)(Larson and Salinas 1995). Total carbon 2 concentrations range from 0.95 to 5.41 mg/1 (Larson and Salinas 1995). Maleug et al. (1972) reported total carbon concentrations to be less than 1 mg/l. In addition, both phytoplankton (Larson et al. 1991; Powers et al. 1975, Larson 1972) and zooplankton occur in low densities in Waldo Lake (Powers et al. 1975, Maleug et al. 1972, Malick et al. 1971.) Given the ultraoligotrophic nature of Waldo Lake, it is surprising that introduced fish in the lake are relatively large in size and in good condition. The productive capacity of lakes is often determined based on physical, chemical, and biological characteristics within the pelagic zone. Benthic productivity is not usually considered when determining the trophic status of lakes, but benthic organisms have been shown to be important components in the diet of fish in many oligotrophic lakes in the Cascade Mountains (Liss et al. 1995, Buktenica 1989). Due to the diverse values and changing expectations of society, there is a growing concern about the management of public lands. Because Waldo Lake is located on the Willamette National Forest, the United States Forest Service is responsible for the management of the Waldo Lake Basin, although other agencies such as the Department of Environmental Quality, the Oregon Department of Fish and Wildlife, the Environmental Protection Agency, and the State Parks and Recreation Department are also involved in decision-making processes. The U.S. Forest Service has responded to public concerns about resource management by adopting goals and objectives that recognize the importance of studying entire ecosystems, rather than focusing solely on one resource. Ecosystem management strategies have been adopted at regional and local levels. In 1993, the Willamette National Forest adopted an 3
Ecosystem Management Strategy to incorporate the principles of ecosystem management in its daily operations (Willamette National Forest, 1993). The goal of the ecosystem strategy is to manage using a holistic approach that takes into account people, natural resources and their interactions. A natural-cultural system conceptual framework is one example of an ecosystem management perspective. The natural-cultural system, as described by Gregor (1982) and Warren and Liss (1983), is broken into five components: water, substrate, climate, biota, and human culture (Figure 1). The basic premise is that all components are related and a change in one will affect others. Individual components can be studied in detail but cannot be removed completely from the context of the system as a whole. This contextualistic idea can be related to a tapestry. If one is interested in a particular thread within a tapestry, this thread can be raised in relief and studied closely, but if the thread is pulled out of the tapestry, not only does the tapestry unravel but the context within which the thread was woven is lost. All components of the natural-cultural system are interrelated and inseparable. To understand the interrelationships that affect the age, growth, and diet of fish in Waldo Lake, it is necessary to examine each of the components that contribute to the overall functioning of the Waldo Lake natural-cultural system. Fish ecology can be raised in relief, but cannot be removed from the context of the other components of the Waldo Lake natural-cultural system. The substrate and local climate of an aquatic system affects water chemistry and water temperature which, in turn, affects nutrient availability and nutrient mixing (Lomnicky, 1996). The availability of nutrients 4
determines the types of biota as well as their abundances (Liss et al. 1995). The cultural component, depending upon the values held for the particular resource, determine the overall management of the system. Natural-cultural systems can be described at different levels depending upon the question of interest. For purposes of this research, the ecology of fish in Waldo Lake, the natural-cultural system will be described at the Waldo Lake Basin level (Figure 2). However, the relationships between the Waldo Lake Basin and adjoining natural-cultural systems should not be forgotten because at a higher level of resolution, adjoining natural- cultural systems affect one another (Figure 3). The primary goal of this research is to increase the understanding of the ecological conditions that sustain fish growth and condition in Waldo Lake. Although there are emerging controversies in the basin, such as the effects of fish stocking and motor boat use on water quality, there have been very few attempts to review and synthesize the available data on Waldo Lake so that it exists in a single document. This is another goal of this thesis. The specific objectives are to:
1)summarize and synthesize available information on substrate, climate, water (water chemistry and other limnological information), and biota (phytoplankton, zooplankton, macroinvertebrates, amphibians, allochthonous and autochthonous input).
2)describe the cultural history and the current cultural values of the Waldo Lake Basin. 5
3)determine the age, growth, length, weight, condition, diet, and reproduction of introduced fish species in Waldo Lake.
4)interrelate the above information to show how these components of the natural-cultural system are related. NATURAL-CULTURAL SYSTEM
..... r
, ,,,
CULTURE SI, CLIMATE WATER kNk% SUBSTRATE BIOTA It
I I
psfp.104 Valp Wm) fi Rad Ilion Foundation 1 .,WAter.a Ills rhea Water th, UOAM0114 ,,. 4roinp.I01.1 Ilk, articles 1 Parent Material ;Informational 71 IN 14, Herq/urass.associated Gases N°11 -5°11 14 MirtiVis soerif id ! iiiiiriii14.0 622:dl:!rui....-2s6...... uL6.....atuaiati.lilk` RION real Water ;
Figure 1. A natural-cultural system symbolized in terms of its primary (1°) and secondary subsystems (2°). After Gregor (1982). 7
a
a :4 MILES 0 2 3 5 4, i as 0 2 4 6 8 KILOMETERS Rigdon Butte (1706 m)
.:-tfit5W1 Charlton Butte (2134 m)
N C
The Twins (2244 rn)
alaa - 13azixt Boundary
cam; Waldo Lake Wilderness
Mt Ray (2134 m)
Figure 2. The Waldo Lake Basin and the Waldo Lake Wilderness boundary. (A) (B)
NATURAL-CULTURAL SYSTEM
Figure 3. (A) The natural-cultural system entailing compositional hierarchy of human culture (C), climate (C1), biota (B), water (W), and substrate (S). (B) The environment of the natural-cultural system. After Gregor (1982). 03 9
COMPONENTS OF THE WALDO LAKE NATURAL-CULTURAL SYSTEM
SUBSTRATE
The substrate of a natural-cultural system depends upon the geologic history of the basin of interest. The geologic events that form the basin determine the substrate types of the basin and the lake. These substrate types are an important factor in determining nutrient availability in the lake environment.
Geologic History The geologic history of the Waldo Lake Basin is in part responsible for the ultra-oligotrophic nature of Waldo Lake. Basin formation is commonly attributed to glaciation (Larson and Donaldson 1970) yet after study of the geology of the basin and the bathymetry of Waldo Lake, Woller and Black (1982) suggest that the lake was formed by volcanic activity. The bathymetric map of Waldo Lake depicts a steeply sloping western shoreline and a more gradually sloping eastern shoreline (Figure 4). Glaciers typically form lake basins that are longest in the direction that the glacier is moving and steepest towards the source of the ice (Woller and Black, 1982). Glaciers are thought to have moved westward through this region, a direction opposite of that which would have been necessary to create a lake that is deepest on the western shoreline and longest along the north-south axis. Carbon dating suggests that the western shoreline is the result of an 10
Figure 4. A bathymetric map of Waldo Lake. 11 older basaltic andesite flow estimated to be between 300,500 and 500,000 years old. The gently sloping bathymetry of the eastern shoreline is attributed to lava formation by an ancient volcano, now known as The Twins, located 5 km east of Waldo Lake (Figure 5). The age of this flow is estimated to be between 10,000 and 250,000 years old. The presence of glacial drift on the southern shore of the lake suggests that glacial activity did occur in this area, but it is not thought to have been the major factor forming the Waldo Lake Basin.
Basin and Lake Morihometr' Waldo Lake, located at an elevation of 1650 meters in the central Oregon Cascade Range, is the second largest natural body of water in Oregon. The area of the Waldo Lake Basin is 79 km2. The lake encompasses an area nearly one third of the total basin area (25.12 km2). The lake has a volume of 0.95 km3, an mean depth of 38.0 meters, and a maximum depth of 128 meters (Larson and Donaldson 1970).
Basin Substrate The regolith of the basin consists of moderately weathered light colored pumice and rounded rock boulders up to 1.5 meters in diameter (Larson and Donaldson 1970, Malueg et al. 1972). According to Larson (1972) the depth of the soil mantle is no greater than 2 meters and the underlying fractured, hard basaltic bedrock is exposed in many places, especially at the north end of the lake. The soil mantle of the basin is porous and allows for rapid percolation of groundwater (Larson and Donaldson 1970, Davis and Larson 1976). 12
HILES a 2 1 4 5
0 2 4 6 8 KILOriETERS tr :41V.447 Rigdon Butte (1706 m) 'Vi1,22 North Fork of the Middle Fork X 4.1-17 of the Willamette River ?Mni Charlton Butte (2134 m) Dam Camp Outlet Cove X Brookic Slide
Islet Campground *V. Waldo Lake (1650 m)
1111
The Twins (2244 ni)
Shadow Bay 6'
- - -13aain Boundary Brifige East of South Waldo Shelter South Waldo Shelter Tributary Mat- Waldo Lake Wilderness ,0440alxvi' Mt Ray (2134 in)
Figure 5. Fish sampling locations in Waldo Lake and its tributaries and outlet (North Fork of the Middle Fork of the Willamette River) (designated by an X on the map). 13
Lake Substrate The lake substrate is similar to that of the surrounding basin. The irregularly shaped shoreline is composed of bedrock, boulders, cobble, gravel, sand and silt (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Sandy beaches are common on the eastern and northern shores but are rare along the western shore. The lake bottom is comprised primarily of silt. Studies on sedimentation rates by Davis and Larson (1976) suggest that the lake has always been ultra-oligotrophic and that the sedimentation rate is low (approximately 1.5 gr/m2/yr). The organic contents of these sediments also suggest that Waldo Lake is ultraoligotrophic. Sediments taken from the deepest part of the lake (127 m) contained 0.2 percent total phosphorous, 0.9 percent total nitrogen, and 5.1 percent total carbon (Malueg et al. 1972).
CLIMATE
Climatic conditions are important components of natural cultural systems. Climate determines the amount, timing, and form of precipitation entering a basin as well as the solar radiation, air temperature, and wind speed and direction. Climatic conditions determine the environment in which the basin is situated. In addition, climate may play a role in basin formation through glacial activities. 14
Precipitation The major sources of water entering the lake come from direct precipitation and snow melt runoff (Johnson et al. 1985). The average precipitation is between 154 and 180 cm (Larson and Donaldson 1970, Powers et al. 1975, Lidder et al. 1980). Precipitation falls as snow during the winter months with a reported mean of 8 1/3 m (Larson and Donaldson 1970). Summer months typically experience less precipitation than occurs during the rest of the year.
Air Temperature and Solar Radiation The mean annual air temperature is 5° C (Larson and Donaldson 1970). Yearly average monthly temperatures range from -5.2° to 18° C (Lidder et al. 1980). The entire lake surface freezes during the winter of some years. Larson (1970) reported that the average incident radiation for the Waldo Lake area was 266 g cal/cm2/4 hrs. This was measured in 1969 from 1000 to 1400 hours.
Wind Speed and Direction Winds in the basin are typically from the west and may reach 12 to 20 knots.
WATER
The water component of a natural-cultural system describes the chemical and physical attributes of the environment in which aquatic organisms live. This component is extremely important as these attributes influence the colonization of species and their abundance. 15
Water Chemistry Waldo Lake is thought to be one of the most dilute lakes in the world based on comparing water chemistry and biological standards to those of other lakes that are classified as being oligotrophic (Larson and Donaldson 1970, Larson 1972, Maleug et al. 1972) Powers et al. (1975) supported this conclusion by reporting that the specific conductance and total dissolved solids in Waldo Lake are an order of magnitude less than those in other lakes in North America that are classified as oligotrophic, such as Lake Tahoe and Crater Lake. Nutrient concentrations in Waldo Lake are very low. The concentrations of ions, conductivity, and alkalinity in the lake are within the range of those concentrations measured in snow samples taken from the basin (Maleug et al. 1972) and are similar in composition to rainwater in a pristine environment (Johnson et al. 1985). Larson (1970) compared the water chemistry of Waldo Lake to that of distilled water. Inorganic nitrogen concentrations reported by Larson and Salinas (1995) were below the level of detection(1.0 p/1) on most sampling dates. Ammonia concentrations were more variable (1.0 to 19 g/1)(Larson and Salinas 1995). Both total and organic phosphorous concentrations are very low (<5 g/1)(Larson and Salinas 1995). Total carbon concentrations range from 0.95 to 5.41 mg/1 (Larson and Salinas 1995). Maleug et al (1972) reported total carbon concentrations to be less than 1 mg/l. Larson and Donaldson (1970) reported that samples taken from the water surface and from deep within the lake had nearly identical chemical characteristics. 16
Other Limnological Information Aside from water chemistry there are other physical limnological characteristics that describe the oligotrophic nature of Waldo Lake such as Secchi disk readings, pH values, and temperature and dissolved oxygen profiles. Summer Secchi disk readings, which describe the transparency of a lake, ranged from 23.0 to 35.4 m (Larson and Donaldson 1970, Maleug et al. 1972, Powers et al. 1975, Lidder et al. 1980). Secchi disk readings may vary depending upon climatic conditions or due to coniferous pollen suspended in the water column (Powers et al. 1975). The pH of Waldo Lake, taken from both the surface and the water column, varies from a range of 5.3 to 5.9 (Maleug et al. 1972, Lidder et al. 1980) to a range of 6.0 to 6.6 (Carter et al. 1966, Larson and Donaldson 1970). More recent research (1989 to 1993) found pH values ranging from 5.4 to 7.6 (Larson and Salinas 1995). The alkalinity of Waldo Lake is very low at <4 mg/1 as CaCO3(Carter et al. 1966, Maleug et al. 1972). Larson and Salinas (1995)observed a range in alkalinity from 1.6 to 2.9 mg/liter as CaCO3 This low alkalinity suggests an extremely low buffering potential to resist changes in pH. The summer water temperature ranges from 18.3° C at the surface to 3.3° C at a depth of 100 m (Larson and Salinas 1995). The lake is thermally stratified from June through October (Larson 1970). Thermal stratification occurs every year and the epilimnion ranges in depth from 5 to 10 m (Powers et al. 1975). The thermocline occurs between 14 and 20 m (Lidder et al. 1980). Dissolved oxygen was reported to be near saturation levels at all lake depths by Carter et al. (1966). Lidder et al. (1980) reported dissolved oxygen concentrations of 9.0 mg/1 in the epilimnion and 11.5 mg/1 in the hypolimnion. These results were similar to those found by Ziesenhenne in 17
1938. Powers et al. (1975) estimated the annual evaporation from the lake to be 109 cm and the lake water retention time to be 21.2 years.
BIOTA
The biota in a natural-cultural system can be described as the living organisms found within the system of interest. In the Waldo Lake natural-cultural system the biotic components that will be described include those inhabiting the lake environment such as phytoplankton, zooplankton, autochthonous input, benthic macroinvertebrates, amphibians, and fish as well as the terrestrial components which include plant communities which provide allochthonous input to the lake as well as terrestrial invertebrates and vertebrates. Research on age, growth, and diet of fish in Waldo Lake was performed during the 1992 and 1993 field seasons. The methods used and results obtained from this research are discussed in the following chapters. The remainder of this chapter summarizes the information that is currently known about the biotic components of the Waldo Lake natural-cultural system.
Phytoplankton Phytoplankton primary production and chlorophyll a concentrations in Waldo Lake are considered to be the lowest ever reported for freshwater lakes (Larson 1991). Primary production is thought to be controlled by temperature, light and nutrient availability (Larson 1970). Powers et al. (1975) found that primary productivity and phytoplankton densities in Waldo Lake 18
were significantly less than those found in Crater Lake or Lake Tahoe. Larson (1972) reported barely measurable concentrations of chlorophyll a (2.9 mg chl a/ m2). More recent studies indicate that primary production (mg Carbon/m2/hr) has increased from a mean of 6.79 in 1989 to a mean of 69.97 in 1993 (Larson and Salinas 1995). Previous to 1989 the primary production in Waldo Lake was fairly constant. Dinoflagellates are the predominant phytoplankton taxa. The most common dinoflagellate belongs to the genus Glenodium (Johnson et al. 1985). Green flagellates and diatoms occurred in low densities (Maleug et al. 1972). The most common diatom is the genus Eunotia although Asterionella formosa, Melosira sp., and Synedra sp. are also present (Johnson et al. 1985) Cymbela and Tabellaria sp. have also been identified in Waldo Lake (Carter et al. 1966). Davis and Larson (1976) added Peronia sp., Frustulia sp., Navicula sp., Achnanhtes sp., and Fragilaria sp., to the list of diatoms present in Waldo Lake after conducting sediment core tests. They concluded that most of the diatoms were periphytic and very few were planktonic. They also found that oligotrophic diatoms were present throughout the core sample suggesting no changes in the water quality of the lake prior to the 1976 study.
Zooplankton Zooplankton populations in Waldo Lake are sparse throughout the water column but are thought to be more abundant near the lake bottom (Aquatic Analysts 1990). Powers et al. (1975) and Maleug et al. (1972) found no zooplankton in Waldo Lake plankton tows. Malick et al. (1971) collected between 0.27 and 1.40 zooplankton/ m3 19 while performing vertical tows using a no. 6 mesh net (intake diameter = 0.5 meters). These numbers were significantly lower than those Malick et al. (1971) obtained in Crater Lake (260 to 575 zooplankton/ m3). Larson and Donaldson (1970) and Lidder et al. (1980) were more successful at collecting zooplankton. Zooplankton taxa captured included Diaptomus, Daphnia, Polyphemus, Senecella, Calonoides, and two rotifers. There has been an apparent change in both zooplankton density and species composition since zooplankton studies were first initiated in the late 1960's (Larson and Salinas 1995). Zooplankton densities increased from 2 individuals/m3 in 1966 to over 4,000 individuals/m3 in 1991. The dominant taxa also changed during this time period from Daphnia to Bosmina.
Benthic Macroinvertebrates Macroinvertebrates are integral members of high mountain lake ecosystems. One group of macroinvertebrates, aquatic insects, comprise a major proportion of the secondary productivity in freshwater systems (Benke 1984). In addition, Merritt et al. (1984) described aquatic insects as performing important roles in the processing, cycling, and storing of nutrients in lentic and lotic ecosystems. Larkin (1979) labelled freshwater invertebrate species as "fish food", and according to Healey (1984) fish production can be influenced by aquatic insects that provide a substantial forage base for many freshwater fish populations. A total of 41 taxa were collected from Waldo Lake nearshore and offshore samples (Table 1) using sweep nets and benthic core samples in the nearshore and an Eckman dredge in the offshore. Taxa is used in this context to 20 identify organisms at a particular level of taxonomic resolution (e.g., order, family, genus). Aquatic insects comprised the majority of taxa (80%) collected in benthic samples (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). The nearshore area, or littoral zone, of Waldo Lake had the highest diversity of taxa with 98% of all taxa present in nearshore microhabitats. The number of taxa collected from offshore sites, or pelagic zone, was considerably less (27% of all taxa). Differences in distribution, diversity, and abundance of macroinvertebrates in nearshore microhabitats can, in part, be related to concordance between habitat conditions and the habitat requirements of organisms (Liss and Warren 1980, Gilinsky 1984, Hoffman et al. 1996). Many differences observed during a season may be due to perennial localized conditions associated with benthic substrates and habitat complexity. The distribution of nearshore macroinvertebrates in Waldo Lake varied by taxa and microhabitat. Table 2 shows the number of taxa found in each of the microhabitat types during the 1992 and 1993 nearshore benthic surveys. Taxa diversities were lowest in the sand and massive rock/bedrock microhabitats and highest in sand/silt, gravel/cobble, small boulder, large boulder, and aquatic vegetation microhabitats (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). 21
Table 1. Macroinvertebrate taxa collected from nearshore microhabitats (littoral zone) and offshore areas (pelagic zone) of Waldo Lake, 1992-1993) (Robert Hoffman, Department of Fisheries and Wildlife Oregon State University, unpublished data).
Functional Taxa Nearshore Offshore Feeding Group
Hydra aamatoda )0a SCAV Atari Oligochaeta 300( DETR Mirudinea SCAV Anphipoda Talitridae Hyallela azteca MO( SCAV Gamnaridae Gammarus sp. xxx SCAV Pelecypoda Sphaeriidae MC< DETR Ephemeroptera Baetidae Callibaetis CODA Siphlonuridae Ameletus CODA Leptophlebifdae pareeptoohlebia CODA Cdonata Aeshnidae Aeshna PRED Cordulfidae PREO Lestidae PRED Libellulidae Sympetrum, Libellula PRED Coenagrionidae PRED Plecoptera Chloroperlidae Sweltsa PRED Pteronarcyidae Pteronarcella SHRD Trichoptera Lepidostoaatidae Leoidbstoma SHRD Leptoceridae Mystacidks CODA Liavvq3hilidae Nesperophytax SHRD Omneohilus SHRD Psychoelypha CODA Polycentropodidae Polycentroous PRED Megaloptera Sialidae Sialis PRED Neaiptera Corixidae PRED Gerridae Gerris. Treaobates PRED Notonectidae Notonecta PRED Saldidae PRED Coleoptera Curculionidie SHRD Dytiscidae Hydaticus PRED Nydroporus MO; PRED Oreodytes PRED Gyrinidae irxrs PRED Nydrophilidae Hydrophilus PRED Lepidoptera Pyralidae Crambus SHRD Diptera Ceratopogonidae PRED Chfronmaidae GERR Culicidae Aedes CODA Tipulidae PRED/SHRD
PRED = Predator CODA = Collector-Gatherer SCAV = Scavenger SNRD = Shredder DETR = Detritivore GENR = Generalist 22
Table 2. The number of taxa and the percent of the total number of taxa collected in the nearshore microhabitats, 1992 and 1993 (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data).
Microhabitat Number of Percent Taxa (n = 40)
Sand 16 40.0 Sand/Silt 26 65.0 Gravel/Cobble 29 72.5 Small Boulder 27 67.5 Large Boulder 26 65.0 Massive Rock/Bedrock 17 42.5 Aquatic Vegetation 23 57.5 23
Differences in macroinvertebrate distribution were also related to time-of-year. Some macroinvertebrate taxa such as Gammarus, Ameletus larvae (order Ephemerpotera), and Chloroperlidae larvae (Order Odonata) were found consistently throughout the ice-free season (June-October) (Table 3) (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Other taxa such as Callibaetis larvae (order Epmemeroptera) and Corduliidae larvae(order Odonata) were most abundant during the early season, whereas Paraleptophlebia larvae (order Ephemeroptera) and several trichoptera taxa were most prevalent during mid-season. Taxa most abundant during the late season were Hesperophylax and Psychoglypha larvae and pupae (order Trichoptera). All nearshore macroinvertebrate taxa collected in 1992 and 1993 were assigned to functional feeding groups (Merritt and Cummins 1984). The majority of taxa in Waldo Lake were classified as predators (50%) although scavengers, shredders, and collector-gatherers were also present (Table 1). In general, functional feeding group organization tended not to vary much between microhabitats (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data).
Terrestrial Invertebrates Terrestrial invertebrates may be an important component of fish diet in some lakes (Reimers et al. 1955, Wales 1946, Smith 1961, Reimers 1979). Terrestrial invertebrates were collected from the lake surface and from onshore substrates along the lake perimeter during the 1992 and 1993 field seasons. Most terrestrial invertebrate taxa were observed during the first month of 24
Table 3. The presence of nearshore macroinvertebrates from late May through early October. Placement into categories was based on the mean number of microhabitats in which each taxon was present during each month. (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). 25 Table 3.
Category Associated With Portion of Season When Macroinvertebrates are Present Taxa 1 2 3 4 5 6a 6b 6c
Nematoda X Atari X Oligochaeta X Hirudinea X Hyallela azteca X Gammarus X Sphaeriidae X Ameletus X Callibaetis X Paraleptophlebia X Aeshnidae X Coenagrionidae X Corduliidae X Lestidae X libellulidae X Chloroperlidae X Pteronarcyidae X Hesperophvlax X Leoidostoma X limnephilus X MVstacides X Polyeentropus X Psychoglvpha X Sialis X Corixidae X Gerris X Notonecta X Saldidae Trepobates X Curculionidae Gyrinus X Hydaticus Hydrophilidae Hydroporus. X X qa24YTS1 X tfembus Ceratopogonidae X Chironomidae X X Culicidae X
Totals 7 6 11 2 5 8 1 1 Percent 17 15 27 5 12 19 2 2
Key to Categories:
1. Fairly consistent presence the entire season 2. Highest presence early-season 3. Highest presence mid-season 4. Highest presence late-season S. Highest presence during the first month of season 6a. Present during first month only 6b. Present during second, third, or fourth month only 6c. Present fifth month only
1992 Season = late-May to early-October 1993 Season = late-June to early-October 26 the field season, decreasing to only one family (Formicidae) by August (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Terrestrial vertebrates observed in the Waldo Lake Basin include spiders (Arachnida), grasshoppers (Orthoptera), Homoptera, ground beetles and lady bird beetles (Coleoptera), moths (Lepidoptera), and several families of Hymenoptera.
Amphibians Salamanders were secretive and difficult to locate. Two species were identified in Waldo Lake: Ambystoma gracile and Taricha granulosa. Adults and neotenes of these species were found in Waldo Lake, but no egg masses were found in Waldo Lake. Several small ponds in the area could be used for egg laying and early larval development (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Frogs and toads were abundant in the nearshore areas of Waldo Lake. Species identified include Rana cascadae, Bufo boreas, and Hyla regilla. Adult H. regilla were seen primarily in June, while adult R. cascadae and B.boreas were present from June through early October. R.cascadae tadpoles and recently metamorphosed individuals were found in meadow areas and grass bordered coves along the south shore of the lake near the South Waldo Shelter.
Allochthonous Input A lake can be influenced by its watershed through inputs of allochthonous organic material (Richey and Wissmar 1979, Wetzel 1979). These materials are important sources of nutrients and vary according to timing, 27 quantity, quality, and resistance to decomposition (Richey and Wissmar 1979, Wetzel 1979, Ward 1984). Allochthonous inputs can be an important source of carbon in lakes that have limited autochthonous primary production (Ho 1980). In oligotrophic Mirror Lake, New Hampshire, USA, Cole et al. (1989) found that 70% of the lake's carbon input was derived from terrestrial inputs, while in Findley Lake, Washington, USA, Wissmar et al. (1977) found that allochthonous inputs provided enough carbon to be a sufficient forage base for aquatic insects. Aquatic insects have adapted in many ways to exploit this source of energy (Wetzel 1979, Ward 1984). Allochthonous inputs can also potentially enhance periphyton production in lakes and greatly influence biological activity on benthic substrates and in the water column (Richey and Wissmar 1979). The deposition of allochthonous organic matter occurred both onshore and within Waldo Lake, especially in coves and other sheltered areas along the lake shoreline (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). The deposition of allochthonous organic material at onshore locations along the shoreline of Waldo Lake was extensive and contained a large amount of organic material. The allochthonous organic matter in Waldo Lake is composed predominantly of conifer needles, pollen, coarse and fine wood, conifer cones, and grass. Combinations of these materials are deposited in large masses along the shoreline or blown onto the lake surface, usually in the nearshore area, where they sink to the substrate surface. Inputs on the nearshore substrate are often re-suspended and washed ashore by the action of wind and waves, while organic material in onshore deposits are sloughed back into the water where they again sink to the substrate. 28
This cyclical movement of allochthonous materials continued throughout the ice-free season (approximately June to mid-October) until the lake water level decreased to a point where onshore deposits were no longer impacted by shoreline wave activity (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Pollen is a form of allochthonous input into many lakes, but may not significantly contribute to the nutrient cycle within a lake. Pollens tend to be differentially resistant to decay (Sangster and Dale 1961, Wetzel 1983, Faegri and Iverson 1989), especially in the non-oxidizing sediments of most standing waters (Wetzel 1983). Sangster and Dale (1961) found Pinus pollen to be extraordinarily resistant to disintegration and was therefore well represented in the sediment deposits of four habitats (pond, lake, swamp, bog) in Ontario, Canada. Pollen was sampled at nearshore and offshore locations in Waldo Lake (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Two genera, Pinus and Abies, were identified and appeared to be most prevalent in June and July. Pollen tended to accumulate in large masses along the shoreline either on the substrate or suspended in the water column. Samples of pollen collected by hand from large clouds of suspended pollen grains contained 13,250 grains/ml to 19,800 grains/ml. Pollen did not appear to accumulate in large masses offshore, although occasional "slicks" of pollen on the lake surface could be seen. Pollen grains were collected in offshore tows during June and July with the greatest number of grains per tow occurring in late-July (126 grains per 10 m tow). Grains of pollen were not found in August or September tows. It appears that pollen input into Waldo Lake occurs primarily 29 from late-Spring (i.e., approximately June) to early summer (i.e., approximately late-June through July) and is concentrated in the nearshore area, where much of the pollen accumulates on the lake substratum.
Autochthonous Organic Material According to Wetzel (1983) the organic matter of aquatic systems is often synthesized predominantly through primary phytoplanktonic production. Yet, in ultraoligotrophic lentic systems, a large proportion of a lake's primary production can be derived from other autochthonous sources such as benthic plant production (Kalff and Welch 1974, Welch and Kalff 1974). Autochthonous materials have been identified as the primary sources of particulate matter in many lakes (Merritt et al. 1984). Typical materials include phytoplankton, moss, emergent/ submergent vegetation (such as grasses and vascular hydrophytes and periphyton), bacteria, fungi, fine detritus, and microscopic invertebrate species (Lamberti and Moore 1984). Autochthonous materials collected from Waldo Lake include epibenthic algae, moss, submerged grasses, emergent/submergent vascular hydrophytes, and periphyton associated with cobble and small boulders (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). 30
HUMAN CULTURE
Human influences have increased since the 19th century making the human component a very dynamic and integral part of the present day Waldo Lake Natural- Cultural System. Table 1 shows how the cultural components might interact with the natural components. To understand the role of human culture in the Waldo lake natural-cultural system it is helpful to look at the history of human activities and management in the basin. This information gives insight to the development of human values currently associated with Waldo Lake.
History of Human Culture Component Waldo Lake was a natural system long before it became a natural-cultural system. This change occurred about 5,000 years ago when Native Americans are thought to have first inhabited the Waldo Lake Basin. Before the addition of the cultural sub-system, the natural sub system likely developed along a course different from that seen today. When humans interact with a natural system, the development of that system may be changed through the direct and indirect effects of the interactions. This is part of the evolution from a natural to a natural-cultural system. Archeological sites indicate that Native American tribes such as the Klamath, Calapooyan, and Molallas used the area surrounding Waldo Lake approximately five thousand years before white settlers arrived. Information on the Native Americans is limited, but it is probable that the Waldo Lake Basin was used primarily as a summer 31 camp area for hunting and huckleberry picking (Carol Winkler, archeologist, US Forest Service, personal communication). White settlers first explored this area in the 1800's. Judge John Beckenridge Waldo, the lake's namesake, visited the area in the late 1800's (Williams 1989). The Waldo Lake Basin and the surrounding areas were used for camping, hunting, and fishing. During this time, the basin could only be accessed by horseback. Access to Waldo Lake was limited to jeep roads and hiking trails prior to 1969. Since this time, paved roads to the lake and three campgrounds on the eastern shore, containing a total of 226 units, have been added. Since the addition of the campgrounds, visitor use has increased dramatically. The Forest Service reports that in 1971 there were 18,700 recorded visitor use days and by 1992 this number had increased to 144,002 (Table 4). Visitor use is highest during the snow-free season, which is from late May to early October in most years. The largest percentage of human use occurs in the form of overnight camping, with fishing, hiking, boating, viewing, picnicking, swimming, hunting, and winter use also occurring in the basin (Table 5). Since the road into Waldo Lake is not plowed, winter use consists primarily of snowmobiling, cross country skiing, and snowshoeing. In 1984, Congress passed the "Oregon Wilderness Bill", which designated the western and northern portions of the Waldo Lake Basin as wilderness (Figure 2). The southern and eastern portion of the basin, as well as the lake and its shoreline are not included in the wilderness designation. Motor boats are allowed on the lake, although there is a state regulation limiting speed to 10 miles per hour. 32
Table 4. Visitor use days at Waldo Lake Campgrounds from 1969 to 1992 (Chris Jensen, USFS, Willamette National Forest, Oakridge Ranger District, unpublished data).
Year Number of Visitors
1971 18,700 1972 16,400 1973 27,900 1974 25,300 1975 29,300 1976 19,600 1977 23,200 1978 25,000 1979 24,500 1980 33,300 1981 49,700 1982 44,900 1983 55,100 1984 58,200 1985 53,700 1986 61,952 1987 91,780 1988 97,754 1989 83,241 1990 96,397 1991 121,801 1992 144,002 33
Table 5. Waldo Lake recreation use data (modified from the Oregon Department of Transportation, State Parks Division, 1986).
Activity Visitor Days Percent
Camping 61,800 62 Fishing 8,500 9 Hiking 7,600 7 Boating 6,500 6 Winter Sports 6,200 6 Viewing/Driving 5,000 5 Picnicking/Swimming 3,000 3 Hunting 1,800 2 34
The Introduction of Fish to Waldo Lake Waldo Lake is a naturally fishless lake. The first known stocking of fish was done by Judge John Beckenridge Waldo in the late 1800's (Williams 1989). Files obtained from the Oregon Department of Fish and Wildlife (ODFW) report anglers catching brook trout as early as 1930 although ODFW has no records of stocking the lake until 1938. It is possible that other anglers followed the role of Judge Waldo and transported fish from nearby lakes and planted them in Waldo Lake. ODFW stocking occurred from 1938 until 1990 (Table 6). Species stocked by ODFW include rainbow trout (Oncorhynchus mykiss), brook trout (Salvelinus fontinalis), cutthroat trout (Oncorhynchus clarki), and kokanee salmon (Oncorhynchus nerka). Of these species, all but cutthroat trout exist in the lake today. Brook trout have been stocked nearly every year from 1939 to 1990. Rainbow have not been stocked since 1979 and kokanee salmon were last stocked in 1970. In 1991, stocking of the lake was discontinued due to a threatened lawsuit by the Waldo Wilderness Council for violation of the Clean Water Act of 1972. The basis of the lawsuit was that fish stocking in this naturally fishless lake could potentially increase the nutrient concentrations in the lake and increase primary productivity therefore altering the ultraoligotrophic nature of Waldo Lake.
Fishing Pressure A fishing questionnaire was handed out to campground hosts at North Waldo, Islet, and Shadow Bay Campgrounds to assess the fishing activity on Waldo Lake. From the information gathered in the survey conducted by the campground hosts, it appears that fishing effort on the lake was low throughout most of the summer in 1993. Very 35
Table 6. Number of fish stocked by the Oregon Department of Fish and Wildlife (ODFW) in Waldo Lake, Oregon (from ODFW files, Springfield, Oregon).
Year Rainbow Brook Kokanee Cutthroat Trout Trout Salmon Trout
1938 72,000 1939 98,130 1940 1,234,560 1941 44,330 1948 87,500 1950 583,391 417,169 1951 151,240 1952 247,900 329,270 1953 82,512 570,265 1954 322,327 401,499 1955 84,744 218,975 1956 120,922 297,811 1957 440,738 137,569 1958 175,785 100,000 1959 133,020 240,351 1961 290,240 258,706 1962 100,016 668,860 1963 380,919 300,170 174,980 1964 343,760 213,867 25,125 1965 414,235 284,723 337,080 1966 235,815 384,815 196,550 1967 253,977 179,760 361,920 1968 797,112 338,550 1969 1,444,866 194,650 207,440 1970 300,572 267,462 200,284 1971 299,500 478,400 1972 17,226 172,000 1973 11,830 1974 55,154 1975 199,840 1976 147,000 49,997 1977 291,768 1978 2,400 264,701 200,430 1979 76,683 100,485 1980 110,625 1981 222,273 1982 200,200 1983 249,945 1984 200,705 1985 199,976 1987 74,880 1988 106,864 1989 8,195 1990 109,300 1991 Stocking of Waldo Lake was discontinued. 36 few people reported catching fish in July and August. Primary methods of fishing include trolling, spin casting with lures and fly fishing. Anglers fished both from motorboats and from shore. Fish ranged in size from 8 to 20 inches in length and all were kept. It is possible that other individuals who caught fish were not sampled, but this survey gives the general impression that the lake is not heavily fished. (It should be noted that the people who often fish Waldo Lake do so in the early spring and late fall and therefore would not have been included in this survey). The results obtained from this questionnaire are similar to those reported in 1986 (Table 5). While fishing is one activity that occurs in the basin, it does not appear to be the primary reason that most people visit the area.
Conflicting Values As is common with any resource, there are conflicting ideas about the types and amounts of use that should occur in a given area. Conflicts over the use of Waldo Lake and its surrounding basin occurred as early as the 1800's between recreational users and sheep herders. Controversy over the management of Waldo Lake and its surrounding basin continues. Concern over the management of Waldo Lake has been increasing over the last several years. During the Willamette National Forest Planning process, management of the Waldo Lake Basin received 1,921 comments, making it one of the most commented on areas on the forest (USDA Forest Service, 1991). In addition to the Forest Plan, a number of letters are received each year regarding the development and allowable activities within the Waldo Lake Basin. 37
There are many groups of people who use the lake resulting in differing and sometimes conflicting sets of values. As is often the problem with a multiple-use resource, there are many users who would like to see the lake managed for their own uses and values.
The Values Human values associated with the Waldo Lake Basin were compiled from letters written to the Forest Service, comments to the Willamette National Forest Plan, editorials, magazine and newspaper articles and personal communication with individuals concerned with the management of Waldo Lake. Values that people hold about Waldo Lake can be categorized into two broad categories, protectionists and naturalists and multiple-use advocates.
PROTECTIONISTS AND NATURALISTS Protectionists and naturalists generally believe that long term solutions are the most important aspect of management decisions. Exclusion from human use is considered to be the best management method if it is thought that the natural system cannot withstand the pressures of human activities. In response to management of Waldo Lake, those fitting into the Protectionist/ Naturalist category believe that the biggest threat to Waldo Lake are humans and would support management decisions that would revert the lake back to its natural condition or at least seek to keep further degradation from occurring. Intrinsic in this belief is the thought that motors, which may potentially pollute the lake with oil, gas and noise, should be banned and that campgrounds should be removed if 38 it becomes evident that the number of visitors is negatively impacting the lake. There is also the belief that the stocking of non-native fish species should not be allowed. The belief is that these fish are contributing to the pollution of the lake and there are many less unique lakes nearby where anglers can catch fish. The management views of both protectionists and naturalists is that Waldo Lake should be preserved so that this uniquely wild place will be available for future generations.
MULTIPLE-USE ADVOCATES Multiple-use advocates generally believe that resources should be managed for multiple use, while maintaining the integrity of the natural ecosystem so that future generations may also enjoy the resource. Often underlying this is the idea of sustainable use management, that is, through proper management, resource systems can be utilized in such a way so as to maximize the range of human uses without sacrificing the natural system. In regard to the management of the Waldo Lake Basin, multipe-use advocates believe that multiple use of this resource is possible and that it is not necessary to preclude certain user groups from the lake. Motors are thought to be acceptable because of concerns of safety and lake access. The ten mile per hour speed limit and the few numbers of boats on the lake even during the peak summer season lead this group to the conclusion that motor boats are not posing a threat to the water quality of the lake although some do propose using electric motors to decrease noise pollution. Fish stocking in the lake is a generally accepted activity. Fish were first stocked by Judge Waldo in the late 1800's and ODFW stocked fish from 1938 to 1991. The question that multiple-use advocates 39 pose is, "If fish were polluting the lake why has there not been a detectable change in water quality during this time?" The management view of conservationists is to maintain the beauty and integrity of the Waldo Lake ecosystem, while continuing current activities such as boating, fishing, and camping, especially if there is no available scientific evidence to prove that these activities are harmful to Waldo Lake. Although none of the letters within the U.S. Forest Service files express the value, some members of the public believe that non-wilderness areas such as the eastern portion of the Waldo Lake Basin have an economic value that is not currently being utilized to its full potential as a timber resource and therefore is not being managed properly as a multiple-use resource. There is also the general belief that tourism to places such as Waldo Lake is an economic venue that is not being utilized to its fullest extent. 40
AGE, GROWTH, AND DIET OF FISH IN WALDO LAKE
Methods
Fish Capture Fish were collected one week per month from early June through mid-October (the ice-free season) in 1992 and 1993. Variable mesh experimental gillnets set in nearshore areas were used to capture fish in 1992. During the 1993 sampling period, experimental gillnets and trap nets were set in the nearshore areas of the lake. The length of time that nets were set was variable. The experimental gillnet was checked every few hours and left set overnight in cases where few fish were captured during the day. The trap net was set and then checked between 12 and 24 hours later. During occasions when few fish were captured, the trap net was left for an additional 12 to 24 hours before being re-checked and pulled. A backpack electroshocker was used in 1993 to capture fry in the inlets and the outlet of the lake, although some fry were also captured in the trap net in 1993. Figure 5 shows the sampling locations. Field measurements included species determination, sex, total length, fork length, and weight. Fork length and total length were measured to the nearest millimeter. Weight was measured to the nearest gram using a hand-held scale. Due to concerns about depleting current stocks of fish, otoliths and stomach contents were removed from a sample of fish representative of size classes for the determination of age, growth, and diet. 41
Age and Growth Otoliths are useful in determining the age and growth in fish because of the patterns of bands that occur as fish grow. When otoliths are viewed under a microscope with reflected light, translucent and opaque bands are visible. Opaque bands are associated with the rapid growth of spring and summer, while translucent bands are associated with slower growth of fall and winter. A translucent and opaque band together represent one year of growth (Jerald 1983) Otoliths obtained by the Oregon Department of Fish and Wildlife (ODFW) in 1991 as well as those obtained in the 1992 and 1993 field seasons were analyzed to determine age and growth. Otoliths were immersed in 75% alcohol for 24 hours, and in 95% alcohol for 24 hours to remove any residue. For each fish both otoliths were cleaned and the otolith in best condition was chosen for examination. Otoliths were air dried and then immersed in one-two drops of Canadian Balsam for 24 hours. Following this procedure, otoliths were viewed under a stereomicroscope to determine the number of annular rings and the distance between rings. Fish captured after the formation of the first annular ring but before the formation of the second annular ring were designated as age I fish. The same procedure was used to place fish in other age groups. Growth of fish captured in Waldo Lake was determined from otoliths by backcalculating length-at-age, and by recapture of fish that had been marked and released as age I fry by ODFW in 1988. Backcalculated length-at-age provides information about the length of the fish at the time of annular ring formation. Backcalculated length-at age was determined by using the direct proportion method (Ricker 1975). Only the last year of growth was used to backcalculate length-at-age. Gutreuter (1987) noted that 42 using only the most recent annuli decreased risks of temporal contamination of data for comparisons over time when inevitably, growth information from prior years is incorporated into the estimates for latter years of growth. Also, using only the last year of growth reduced the confusion of size selective mortality (Lee's phenomenon) with annual growth (Gutreuter 1987). Average relative growth rate (GR) was calculated according to Warren (1971) as GR = L2-L1/0.5(L1 +L2)(t2-t1) where L2 is the length at the last annular ring formation and L1 is the length at the previous annular ring formation; t2 is the time at the last annular ring formation and tl is the time at the previous annular ring formation. The average relative growth rate relates growth over a time interval to average size over the same interval, whereas absolute growth [G = L2 - Ll] does not relate to average size. All sexes were combined to increase sample size and all otoliths were assumed to be normal. Length obtained from recapture of fish marked in 1988 provided information on growth of fish of known age. ANOVA was used to analyze differences in age-specific growth rates between years.
Condition The condition of the fish in Waldo Lake was assessed by using a Fulton-type condition factor. Length and weight data was available from 1951 through 1991 from ODFW files. Using these data, as well as the data collected during the 1992 and 1993 field seasons, a mean condition factor was calculated for each fish species captured per year. For brook trout analysis, only those sampling dates occurring between September 21st and October 2nd were used in an attempt to eliminate the effect of time of year as a 43 confounding variable. This was not possible for rainbow trout and kokanee salmon due to low sample numbers, therefore all samples for these species were combined. All sexes were also combined due to a lack of available information in some years. ANOVA was used to analyze differences in mean condition between years.
Diet To determine the diet of fish in Waldo Lake, stomach contents were removed in the field and stored in 70% ethanol. Stomach contents were analyzed at Oregon State University using a stereomicroscope. Stomach content components were identified to the lowest taxonomic level possible using whole specimens or identifiable body parts such as the thorax or head capsule when whole organisms were not available. Taxa were identified using the key developed by Merritt and Cummins (1984). When large numbers of organisms were present in the stomach contents, subsamples were taken. Counts obtained in the subsample were multiplied by the corresponding dilution factor to obtain the total number of individuals of each taxon in the stomach. Taxa that made up greater than one percent of the total number of consumed taxa were analyzed to determine if there was seasonal variation in diet within fish species and to what extent diet overlap occurred between fish species. The percentage of a given taxon consumed, which consists of the total number of individuals of that taxon divided by the total number of individuals of all taxa consumed, describes the relative importance of each taxon in fish diet (Bowen 1983). This method of quantifying food types does not, however, reflect the food preference of the fish. This would require knowing the 44 amount of food consumed of a given type relative to the amount available in the lake (Ivlev 1961). This method also does not take into account the nutritional value of a particular food item. For example an individual salamander is larger and probably has a higher nutritional value than an idividual chironomidae larvae, but each still only counts as one food item. To determine if there were differences in the feeding location of the three fish species in Waldo Lake, taxa consumed by fish were categorized based on the location in which they were found during macroinvertebrate surveys. Some benthic macroinvertebrates were found only in the nearshore samples while others were found in both nearshore and offshore samples. Therefore if a fish had eaten an organism that belonged to the nearshore category, the fish must have been feeding in the nearshore area, while if it consumed a taxon that belonged to the nearshore/offshore category it is impossible to know at which location the prey item was taken. Taxa that were located on the surface during benthic macroinvertebrate sampling were presumably consumed by fish at the water surface or within the water column as the prey item became water-saturated and sunk below the water surface.
Reproduction Reproduction of fish species in Waldo Lake is of special concern due to the discontinuation of the stocking program in 1991. To determine if reproduction is occurring in Waldo lake, major inlets along the southern end and the outlet (the North Fork of the Middle Fork of the Willamette River), from Waldo Lake to the falls, were electroshocked during the 1993 ice-free season. Species of fry caught in these areas were determined. 45
Results
Fish Capture Overnight trap nets and gill nets were the most effective methods of fish capture. In 1992, 42 fish were captured, and in 1993, 187 fish were captured (Table 7). Fish ranged in size from 75 mm (total length) to 480 mm. Brook trout were the most commonly caught species followed by kokanee and rainbow trout. Due to concerns about depleting current stocks, otoliths and stomach contents were removed from 32 of these fish for the determination of age, growth, and diet.
Age and Growth To validate otolith aging techniques, back-calculated length at age from otoliths were compared to the measured lengths from fish belonging to the brook trout cohort marked and stocked as age I fish in 1988 by ODFW. Comparisons of the growth curves shows that backcalculated length-at-age has a similar slope to the length-at-age determined from the capture of marked fish (Figure 6). The confidence intervals of these two curves do not overlap, however, indicating that there is a significant difference between the curves. This could be due to errors in back-calculation techniques, differences in growth rates between the 1988 cohort and the 1991-1993 fish due do differing environmental conditions, or different initial sizes of the fish. Table 8 shows that the growth rates and relative growth rates for the 1988 cohort are similar to those of the 1991-1993 fish which suggests that differences observed may be due, in part, to differences in initial lengths. 46
Table 7. Number of fish captured and the number of otoliths examined by species and year (data and otoliths for 1991 fish were provided by the Oregon Department of Fish and Wildlife, Springfield, OR).
Number of Number of Year Species Fish Captured Otoliths Examined
1991 Brook Trout 136 79 Rainbow Trout 5 0 Kokanee Salmon 0 0
1992 Brook Trout 55 15 Rainbow Trout 4 4 Kokanee Salmon 9 6
1993 Brook Trout 75 23 Rainbow Trout 2 1 Kokanee Salmon 44 6 47
Table 8. Comparison of average growth rates and average relative growth rates between the marked 1988 cohort and the back-caculated lengths of the fish captured in 1991-1993. (Data and otoliths for 1991 fish were provided by the Oregon Department of Fish and Wildlife, Springfield, OR).
Average Growth Rate (mm fish length/year)
Age 1988 fish 1991-1993 fish
I to II 89.7 89.0 II to III 82.3 72.9 III to IV 33.8 36.3 IV to V 24.8
Average Relative Growth Rate (mm/mm fish length/year)
Age 1988 fish 1991-1993 fish
I to II 0.454 0.503 II to III 0.290 0.283 III to IV 0.099 0.116 IV to V 0.067 48
500 -E- Captured Fish Captured Fish 95% CI 450 Back-calculated + Back-calculated 95% CI
400
350E E -c 300 cco m -I 250
200
150
100 III IV V Age (years) L
Figure 6. Comparison of growth rates from captured fish of known age and from back-calculated age from otoliths of brook trout captured between 1991 and 1993. 49
Using only data from the last year of growth as suggested by Gutreuter (1987), the average relative growth rates for each age class of brook trout were compared between years (Figure 7). Brook trout growth rate generally decreased with age. However, there were no significant differences in the growth rate of each age class between 1991-1993 (1991-1993, ANOVA p>0.1). Relative age specific growth rates of brook trout in Waldo Lake are comparable to brook trout growth rates in other Lakes (Figure 8). Due to the small sample sizes of rainbow trout (n=5) and kokanee salmon (n=14), age and growth analysis were not conducted.
Condition The Fulton-type condition factor is an index of well being and is useful in comparing conditions of fish in the same lake over time or in comparing the condition of fish in a particular lake to fish in other lakes. For Waldo lake brook trout there were statistically significant differences between years for mean condition factors (Table 9; F-Statistic = 17.3 with 6 and 1044 degrees of freedom; p-value < 0.01). Brook trout in 1969 and 1992 have slightly higher condition factors than those in other years. The condition of Waldo Lake brook trout is comparable to brook trout in other lakes. The same is true for kokanee salmon and rainbow trout (Table 9). 50
222 1991 1,77] 1992 ;11.21; 1993
I to II II toils III to IV IV 0 v V to VI VI to VII
Age Class
Figure 7. Average relative growth rate for Waldo Lake brook trout. 51
Hon H to III Ill to IV IV to V V to VI Age (Years)
Waldo Lake (OR) Matamek Lake (CAN) Red Rock Lake (CAN) Pyramid Lake (CAN) Bunny Lake (CA) fa Castle Lake (CA)
Figure 8. Mean relative growth rate as determined from otolith analysis for Waldo Lake brook trout (1991-1993) compared to relative growth rates of brook trout from other lakes (determined from length-at-age data). Data for Matamek Lake (Canada), Red Rock Lake (Canada), and Pyramid Lake (Canada) reported in Scott and Crossman, 1979. Data for Bunny Lake (California), and Castle Lake (California) were reported in Carlander, 1969. 52
Table 9. Mean Fulton-type condition factor of fish in Waldo Lake compared to fish in other lakes (the number of fish from which the condition factor was calculated is shown in parenthesis).
Condition. Species Location Factor
Brook trout Waldo Lake (1969) 1.36(115) Waldo Lake (1978) 1.21(377) Waldo Lake (1985) 1.27(186) Waldo Lake (1990) 1.25(107) Waldo Lake (1991) 1.24(136) Waldo Lake (1992) 1.32(55) Waldo Lake (1993) 1.25(75) 8 California Lakesa 0.96(many) Castle Lake (CA)a 1.05-1.98(512) Mono Lake (CA)a 1.34(661)
Rainbow trout Waldo Lake (1991) 1.19(5) Waldo Lake (1992) 1.20(4) Waldo Lake (1993) 1.06(2) Castle Lake (CA)a 1.05(673) Convict Lake (CA)a 1.02 Dorothy Lake (CA)6 0.88 Mildred Lake (CA)a 1.15 Crater Lake (OR)b 1.11(124)
Kokanee salmon Waldo Lake (1992) 1.20(9) Waldo Lake (1993) 1.07(44) Crater Lake (OR)b 0.97(188)
aCarlander 1969 bBuktenica and Larson 1992 53
Diet Taxa found in stomach contents of fish captured in Waldo Lake consisted primarily of aquatic benthic macroinvertebrates, but terrestrial invertebrates and vertebrates were also part of the total diet (Table 10). Of the three fish species present in Waldo Lake, brook trout were the most opportunistic, consuming chironomidae larvae and pupae, trichoptera larvae and pupae, ceratopogonidae adults, amphipods, Hymenoptera (formicidae) adults, as well as the larvae of ephemeroptera, odonata, and megaloptera (sialidae) (Figure 9). Rainbow trout in Waldo Lake consumed primarily chironomidae larvae and pupae although odonata larvae, ephemeroptera larvae, and amphipods were also consumed. Kokanee salmon displayed the most specialized feeding behavior. Kokanee salmon fed almost exclusively on chironomidae larvae and pupae although small numbers of ephemeroptera larvae, odonata larvae, and coleoptera were also consumed. Vertebrates are not included in Figure 9 because they were generally of less importance by number than the other categories of food items and did not make up greater than one percent of the total diet. Chironomidae larvae were the most common component of the diet of all three fish species in Waldo Lake (Figure 9). Other taxa consumed by all three species of fish included ephemeroptera larvae, odonata larvae, amphipoda, coleoptera larvae and chironomidae larvae and pupae. Ceratapogonidae adults were consumed by brook trout and kokanee salmon. Brook trout was the only species that consumed trichoptera larvae and pupae, megaloptera larvae, and hymenoptera adults in amounts large enough to comprise greater than one percent of the total diet. 54
Food Organism
Ephemeroptera
Odonala I. MI= Amphipoda
Trichnidera 1.+11'
Megaloplera
Coleoptera I. I
Chironomidae I.+P \\\ ' \ \ %.%
Ceratapogottidhe
hymen Formienle A
0 10 20 30 40 50 60 70 no 90 100
%. of Total Diet
NE Brook Trout ESE Rainbow Trout Kokanee Salmon (n=67) (n=5) (n=14)
Figure 9. The percent of taxa observed in the stomach contents of fish captured in Waldo Lake (1991-1993). Only taxa comprising >1% of the total diet are included. L = larvae, P = pupae, A = adult). 55
Table 10. Taxa found in stomach contents of fish collected from Waldo Lake in 1992 and 1993. Taxa are grouped according to the location in which they were collected during benthic macroinvertebrate surveys.
AQUATIC
Nearshore Hirudenia Ephemeroptera larvae Odonata larvae
Nearshore and Offshore Oligochaeta Amphipoda Pelycypoda (Sphaeriidae) Trichoptera larvae and pupae Megaloptera larvae Coleoptera larvae and adults Ceratopogonidae larvae and pupae Chironomidae larvae and pupae
Lake Surface (Aquatic Adults) Trichoptera Ephemeroptera Coleoptera Ceratopogonidae Chironomidae
TERRESTRIAL
Lake Surface (Terrestrial Adults) Arachinidae Hemiptera Coleoptera Diptera Lepidoptera Hymenoptera
VERTEBRATES
Hyla regilla (adult) Unknown salamander species Taricha aranulosa (adult) Trout fry 56
All three species of trout in Waldo Lake fed heavily on taxa that inhabited both the nearshore and offshore areas (Figure 10). Rainbow trout and brook trout tended to feed more on organisms found only in the nearshore areas than did kokanee salmon. Brook trout fed on surface organisms while these organisms did not comprise greater than one percent of the total diet of rainbow trout and kokanee salmon. Brook trout diet in Waldo Lake varied throughout the ice-free season. In June, brook trout fed nearly exclusively on trichoptera larvae and pupae and ephemeroptera larvae (Figure 11). In July, brook trout diet was the most diverse of all months. Trichoptera larvae and pupae were still important components of the diet as were trichoptera adults but brook trout also consumed larvae of odonata and megaloptera and terrestrial coleoptera adults, ephemeroptera adults, oligochaetes, and hirudinea. Brook trout diet shifted primarily to chironomidae larvae in August. The larvae of odonata and coleoptera, as well as amphipoda, and hymenoptera (formicidae) were also consumed in August. Chironomidae larvae and amphipods dominated the diet in September. Odonata larvae, terrestrial diptera adults and vertebrates were also consumed in September. In October, brook trout diet shifted primarily to amphipods and ceratopogonidae adults. Trichoptera larvae and pupae and megaloptera larvae were also consumed. To determine if the feeding areas of brook trout shifted throughout the ice-free season, taxa consumed by brook trout were again grouped according to their location during macroinvertebrate surveys (Figure 12). Taxa located only in the nearshore area were consumed less often as the season progressed. Taxa located in both nearshore and offshore areaswere consumed consistently 57
100
80
0) o 60 -a
20
0 Brook Trout (n=67) Rainbow Trout (n=5) Kokanee Salmon (n=14)
Nearshore Nearshore and Offshore Lake Surface
Figure 10.Location of prey items of Waldo Lake brook trout, rainbow trout, and kokanee salmon. Locations were determined from benthic macroinvertebrate surveys conducted during 1992 and 1993 (Table 10; Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data). Only taxa comprising >1% of the total diet of each species of fish are included. 58
June (n = 5) July (n = 11)
Ephcmcroptcre (L) Odonata (L) (38.4%) Oligochctae Mcgaloptcra (L) (4.4%)
Colcoptcra (TA) (22 %) Ephcmcroptcra (AA) (22%)
Ihrudenea (2.2%)
Trichoptera (L+P) Trichoptera (AA) (61.0%) (44.4%)
August (n = 14) September (n = 12)
Chironomidac (L +P) Odonata (L) (23%) (62.1%) Colcoptcra (L) (2.8%)
Amphipoda (4.6%) Amphipoda (273%) Hymeneptera (Formicidac) (TA) (6.5%)
Odonata (L) (6.1%) Chironomidac (1.+P) Vertebrates (3.0%) (82.0%) Di ptcra (TA) (13%) October (n = 25)
Amphipoda (38.2%) Ceratapogonidac (AA) (522 %)
LEGEND = aquatic insect larvae Mcgaloptcra (L+P) (4.4%) P = aquatic insect pupae Trichoptera (L+P) (2.7%) AA = aquatic insect adult TA = terrestrial insect adult
Figure 11.Percent of taxa observed in Waldo Lake brook trout stomach contents (1991-1993). Only taxa comprising >1% of the total diet are included. 59
100
80
60
40
20
Nearshore Nearshore and Offshore Lake Surface Location of Prey Item
June (n=5) July (n=11) August (n=14) September (n=12) October (n=25)
Figure 12.Location of prey items of Waldo Lake brook trout. Only taxa comprising >1% of the total diet are included. 60 throughout the ice-free season although the relative importance of individual taxa in the diet varied by month. Taxa located at the water surface were consumed sporadically throughout the season, probably depending upon the wind drift and hatches of aquatic adults. Brook trout diet does not appear to be consistently related to the relative abundance of benthic macroinvertebratescollected in nearshore and offshore areas. Months when the nearshore or offshore macroinvertebrates were most abundant in nearshore and offshore areas were not necessarily the same months when those taxa were the most frequently consumed (Figure 13). In June, chironomids were the most abundant taxon in the benthic surveys, but constituted less than one percent of brook trout diet. However, trichoptera larvae and pupae were the second most abundant taxon in benthic surveys in June and were a significant component of brook trout diet (Figure 11). Ephemeroptera, although not as abundant as other taxa, were also an important component of brook trout diet in June. In July, trichoptera larvae, pupae, and adults, and odonata larvae were the most consumed taxa in brook trout diets (Figure 11), yet chironomids were much more abundant throughout the lake and amphipods were more abundant in nearshore areas. In August, chironomids were the most common taxon consumed by brook trout (Figure 11) and were the most common taxon in benthic surveys. In September, trout continued to consume large quantities of chironomids even though the abundance of this taxon in the nearshore area had declined significantly. Finally, in October, amphipods were the most common taxon consumed by brook trout. Amphipods were abundant only in the nearshore area in October. 61
Figure 13.The relative abundance of aquatic macroinvertebrate taxa collected from nearshore and offshore areas (1992-1993) (Robert Hoffman, Department of Fisheries and Wildlife, Oregon State University, unpublished data) and the percent occurrence of these taxa in brook trout stomach contents. Figure 13.
% of TnIni Wet infivs./m 2 7. of Tolul Diel I Indy, m 2 100 500 100 100 Trichoptera no 400 00 00 Odonata Larvae Larvae and Pupae
00 300 00 80
10 200 40 40 P 20 100 20 20 \ `4, 0 July August September October June July August September October June
IncIrs./m 2 7. of Total Dlet 7. of Total Wet 100 N Indvs./m 2 100 5.000 350 Chironomidae Amphipoda 00 300 00 4.(WA) Larvae and Pupae
250 80 80 200 40 150 40 2.000
20 100 20 1.000 50 August September October 0 October June July June July August September 7. of Total Wet N Intivs./m 2 100 50 Ephemeroptera DD 40 Larvae - 00 30 KM Offshore Abundance -, 40 20 = Henoshore Abundance I of Total Fish Diet - 20 10
0 June July August September October 63
Small brook trout (101-250mm) tended to be more opportunistic in both taxa consumed (Figure 14) and location of feeding (Figure 15) than did large brook trout (251-450mm). Ceratopoginid adults and amphipods were the major taxa composing the diet of the small brook trout, while larger brook trout tended to consume primarily chironomids larvae and pupae, trichoptera larvae and pupae, ephemeroptera larvae, and amphipods (Figure 14). Small brook trout fed on taxa located in a wider variety of areas than did large brook trout, which tended to concentrate feeding on taxa located in the nearshore and offshore areas (Figure 15). Smaller brook trout also consumed more surface organisms that did larger brook trout.
Reproduction Rainbow trout, brook trout, and kokanee salmon appear to reproducing in the Waldo Lake Basin. Fry of all three species were captured in the bay near the outlet during the 1993 ice-free season. Brook trout fry were also located in the in several of the intermittent tributaries along the southern end of the lake (Figure 5). In the small tributary that flows past the South Waldo Shelter, 3 brook trout fry ranging in size from 75 to 125 mm were captured. Similar-sized brook trout were also found below the first bridge crossing east of the South Waldo Shelter. No fish were sighted upstream of this bridge. Kokanee salmon and rainbow trout fry were captured in the North Fork of the Middle Fork of the Willamette River between Waldo Lake and the falls. Although other tributaries along the southern shore were shocked, no fish were observed. 64
Food Organism
Ephemeroptera °I.
Odonata °I.
Araphip oda
Trichoptera L+P
Mega. sialidae °I.
Coleoptera 'L
Chironomidae °I.+P
Trichoptera °A
Ceratapagonidae °A
Hyrnen.Forraicidac 'TA
0 10 20 30 40 50 60 70 80 BO 100 2; of Total Diet IN 101-250 mm En 251-450 mm (n 36) (n - 30)
Figure 14.The percentage of taxa observed in the stomach contents of two size classes of brook trout (1991-1993). (L = larvae, P = pupae, A = adult). 65
100
80
60 t
40
20
0 Nearshore Nearshore and Offshore Lake Surface Location of Prey Item
101-250mm (n=36) 251-450mm (n=30) I
Figure 15.Location of prey items of two size classes of Waldo Lake brook trout. Only taxa comprising >1% of the total diet are included. 66
Discussion
Waldo Lake: A Complex, Dynamic, Natural-Cultural System The components of the Waldo Lake natural-cultural system are complexly interrelated. A change in one component has the potential to affect other components (Figure 1 and Figure 3). This complexity is observed in all natural-cultural systems, of which the Waldo Lake natural-cultural system is but one example. Table 11 shows how each component of the Waldo Lake natural-cultural system is related to each of the other components. For example, climatic conditions are an important component of the Waldo Lake natural-cultural system. Climate determines the amount, timing, and form of precipitation entering the basin as well as the solar radiation, air temperature, and wind speed and direction. Climatic conditions determine the environment in which the Waldo Lake Basin is situated. In addition, climate has had a role in basin formation through glacial activities. Climate has the potential to affect the human culture component as visitor use days tend to fluctuate depending upon weather conditions and seasonal patterns. Air temperatures and seasonal changes may also affect the biotic component. The substrate of the Waldo Lake natural-cultural system depends upon the geologic history of the basin. These substrate types are an important factor in determining nutrient availability in the lake environment. The water component of the Waldo Lake natural- cultural system describes the chemical and physical attributes of the environment in which aquatic organisms 67
Table 11. A matrix for the Waldo Lake Basin showing the interrelationships between the components of the Waldo Lake natural-cultural system. The matrix depicts how the components shown in rows along the top of the matrix effect those components listed along the left side. Table 11.
Climate Water Biota Substrate Human Culture Evaporation from the lake Air pollution may lead to acid surface results in future rain which could effect the Climate sources of precipitation. pH of Waldo Lake
Pollution and the addition Solar radiation and wind Redistribution of available Due to a low lake to basin and/or redistribution of effect water temperature, lake nutrients through uptake and ratio and the volcanic nutrients are possible mixing and evaporation rates. excretion by the biota. substrate of the basin, Waldo Nutrient addition through Lake has low nutrient depending upon the Water allochthonous and concentrations. There are no management of the basin. autochthonous input as well permanent inlets. Roads, trails, and as from decomposing biota. campgrounds may change runoff patterns. Biotic communities are Precipitation timing, forM and Water quality In Waldo Lake See Figure 16 (Waldo Lake Nutrient availability determine affected by the management amount as well as air determines species Food Web) for greater detail species composition and of the basin. Fish were temperature may effect composition and abundance. of the interrelationships of the abundance. Macroinvertebrate diversity introduced into the Waldo species composition and Low nutrient concentrations biota in the Waldo Lake and density vary depending Lake Basin. Fire abundance. Wind and result in low primary Basin. Biota on the substrate of different suppression activities in the wave action form productivity and sparse basin have the potential to accumulations of zooplankton populations in habitats. affect allochthonous input. allochthonous and Waldo Lake. autochthonous input Sedimentation patterns may The Waldo Lake basin was Decomposition of biota and be affected by roads, formed, in part, by glacial allochthonous and campground, and trails. activity. Wind and wave autochthonous input is a Substrate action cause erosion and source of sedimentation. effect sedimentation rates
The basin defines the setting Human values determine the Visitor use days and types of The water is used for Wildlife viewing, as well as of the lake. management of the Waldo use fluctuate depending upon activities such as boating, hunting and fishing are Lake Basin. Values in the weather conditions and swimming, and fishing. common activities in the Human Culture basin Waldo Lake Basin have seasonal changes. changed over the last few decades. 0 oo 69
live. This component is extremely important as these attributes influence the colonization of species and their abundance. In addition, evaporation from the lake surface results in future sources of precipitation. The biota in the Waldo Lake natural-cultural system can be described as the living organisms found within the system of interest. Figure 16 shows the interrelationships between the biotic populations inhabiting the lake environment and other components of the Waldo Lake natural-cultural system that are closely related to the biotic component. The biota may affect the water component as activities such as feeding and excretion redistribute available nutrients. The decomposition of biota is a source of sediment input. For the human component, the biota is often considered a source of recreational activities such as hunting, fishing, and wildlife viewing. Waldo Lake was originally a natural system and did not become a natural-cultural system until approximately 5,000 years ago when native Americans are thought to have first used the Waldo Lake Basin. Human influences have increased since the 19th century making the human component a very dynamic and integral part of the present day Waldo Lake natural-cultural system. To understand the role of human culture in the Waldo Lake natural-cultural system it is helpful to look at the history of human activities and management in the basin. This information gives insight to the development of human values currently associated with Waldo Lake. Changes in human values associated with the Waldo Lake natural-cultural system have occurred over the last few decades. Fish were originally stocked into Waldo Lake during a period of time when human values focused on development, making Waldo Lake a better, more accessable 70
tight Terrestrial Energy Energy
Alloch honous Autochthonous Nutrients Input Input
Terrestrial Insects
IDecomposition & Sedimentation Detritus
Benthic Mocrolnwrfebralss
Aquatic KoKanee Brook Trout Rainbow Trout e
Humans
Figure 16.A food web focusing on the biotic component of the Waldo Lake natural-cultural system. 71
place for humans to recreate. This is exemplified not only by the stocking of fish, but also the addition roads, campgrounds, and boat ramps into the Waldo Lake Basin. In the last few decades a shift of values has occurred. Now instead of requesting that more amenities be added to the Waldo Lake Basin, many people are looking for more of a pre-developmental type of experience. It also remains to be seen how this trend will change in the future. Changes in the biotic component of the Waldo Lake natural-cultural system have also occurred in the last few decades. Recent studies of Waldo Lake suggest that primary production has increased by a factor of ten from 1989 to 1993 (Larson and Salinas 1995). The cause for this change is unknown and it has yet to be seen if this trend will continue into the future. The components of the natural-cultural system are constantly changing. Some components such as climate and substrate, may change slowly, over thousands of years, while other components such as biota and human culture may change rapidly within a centuary, or even a decade. This capacity of the natural-cultural system to change makes it possible to understand the interrelationships only as they exist at a given time, for at some later time the interrelationships may have changed significantly. Therefore, although it is possible to devise a view of the Waldo Lake natural-cultural system, it is only a snapshot in time of a dynamic system. This capacity of the Waldo Lake natural-cultural system to be dynamic is not unique to Waldo Lake, but is expressed in all natural-cultural systems. 72 Age, Growth and Condition of Fish in Waldo Lake Relative growth rates of Waldo Lake brook trout suggest that they are growing well in this ultraoligotrophic system when compared to other lakes in which brook trout are present. The oldest brook trout captured from Waldo Lake during the course of our research (1991-1993) was eight years old and 470mm in length. Fish in Castle Lake, California reportedly lived as long as the fish in Waldo Lake but were not as large (Wales 1946, 1947). At eight years old, brook trout in Waldo Lake are not the oldest brook trout recorded. A stunted population of brook trout in Bunny Lake, California contained individuals that lived to be 24 years old (Reimers 1979). These fish only reached a length of 238 mm. The dominant factor influencing the length of life and the stunted growth of the Bunny Lake brook trout was shortage of food and low water temperatures that were more conducive to torpor than to activity. In contrast to Bunny Lake brook trout, brook trout in Waldo Lake are large for their age, although fish from Red Rock Lake and Pyramid Lake, both in Canada, reached a larger size at an earlier age (Scott and Crossman 1979) than did Waldo Lake brook trout. Fish in Waldo Lake are in relatively good condition when compared to fish in other lakes. Table 9 shows that Waldo Lake brook trout have relatively high condition factors compared to brook trout in ten lakes in California (Carlander 1969). Kokanee salmon in Waldo Lake are also in good condition when compared to kokanee salmon in Crater Lake (Buktenica and Larson 1992). Rainbow trout in Waldo Lake appear to be in good condition, although the sample sizes are too small to be conclusive. 73 Diet of Fish in Waldo Lake Large fish exist in Waldo Lake, despite its ultraoligotrophic nature, in part because the definition of lake trophic status is based upon physical, chemical, and biological characteristics within the pelagic zone of the lake. Benthic productivity is not normally considered when classifying the trophic status of lakes although benthic organisms have been shown to be important components of fish diet in lakes (Larkin 1979, Healey 1984, Benke 1984, Buktenica 1989, Liss et al. 1995). Benthic invertebrates are important in the diet of fish in Waldo Lake. The most important food items for kokanee salmon, rainbow trout and brook trout were chironomidae larvae and pupae although ephemeroptera larvae, odonata larvae, amphipods, trichoptera larvae and pupae, megaloptera larvae, coloeptera larvae and ceratapogonid and hymenoptera (formicidae) adults also constituted greater than one percent of the total diet. The feeding behavior of salmonids is often characterized as being opportunistic (Muttkowski 1925, Allen 1941, Elliot 1967, and Metz 1974). Prey items include a wide diversity of life forms depending upon available food sources. Large-bodied prey items are thought to be preferred with smaller food items becoming important as they become available and as large prey decline in abundance. Studies of salmonids in lake environments have shown that prey size, visibility, and relative abundance effect the types of prey that are consumed (Bisson 1978, Zaret 1980, Allan 1981). Waldo Lake brook trout diet does not appear to be directly related to the relative abundance of nearshore or offshore benthic macroinvertebrate taxa. Instead, a more complex relationship between the relative abundance of macroinvertebrates, feeding location, and time of year 74
appear to determine which taxa are consumed by brook trout. Brook trout tended to feed on macroinvertebrate taxa that were found only in the nearshore area early in the ice-free season (Figure 12). In June brook trout fed on ephemeroptera (which had a relatively low abundance but were found only in the nearshore area) and trichoptera larvae and pupae (abundant in the nearshore area, but scarce in the offshore area). Chironomids were the most abundant taxa in June, but were not consumed by brook trout. In July, brook trout diet shifted to odonata larvae (located in the nearshore area) and trichoptera larvae, pupae, and adults (not as abundant in the nearshore area as in June, but more abundant in the offshore area). During August and September, chironomidae larvae and pupae were an important component of brook trout diet. Chironomidae larvae and pupae were abundant in the offshore area throughout the ice-free season, and abundant in the nearshore area through August. In addition to chironomid larvae and pupae, amphipods (abundant in both nearshore and offshore areas) and odonata larvae (available only in the nearshore area) were also consumed by brook trout in September. In October, when the brook trout were spawning, amphipods (abundant in the nearshore areas) were consumed frequently. Specialization by specific individuals within a population also occurs, but it is not thought that the degree of specialization has any affect on growth rates (Bryan and Larkin 1972). Different types of specialists tend to grow equally well. The degree of specialization varied both between and within fish species located in Waldo Lake. Kokanee salmon displayed the most specialized feeding behavior. Brook trout consumed a wider variety of 75 taxa than did kokanee salmon. Brook trout feeding behavior also varied depending on fish size. Small brook trout (100-250mm) were more opportunistic than were large brook trout (251-450mm). These findings tend to be consistent with the feeding behavior of brook trout in other lakes. Ricker (1932) found brook trout to be opportunistic, feeding on amphipods, ephemeroptera larvae, trichoptera larvae and pupae, chironomidae larvae and pupae, as well as a variety of aquatic and terrestrial adults. In general the diet of brook trout in lakes tends to be made up mostly of insects and aquatic invertebrates (Reimers 1979, Smith 1961, Wales 1946, Reimers et al. 1955, Allen 1960, Royer 1960). Like brook trout, aquatic and terrestrial insects are the primary food for rainbow trout (Reimers et al. 1955, Bisbee 1961, Wales 1946, Hasler and Farner 1942, Atkinson 1932). Amphipods are also important in rainbow trout diet (Reimers et al. 1955, Atkinson 1932, Hazzard 1932). Efford and Tsumura (1973) found that in Marion Lake Canada, rainbow trout fed specifically on trichoptera larvae and pupae and odonata larvae. Wurtsbaugh and Brocksen (1975) found that the rainbow trout in Castle Lake, California were primarily consuming ephemeroptera larvae and chironomidae larvae and pupae. Rainbow trout in Waldo Lake displayed feeding behavior similar to that found in other lakes. Taxa comprising greater than one percent of rainbow trout total diet included chironomidae larvae and pupae, odonata larvae and amphipods. Kokanee salmon typically feed on zooplankton in lakes where this food item is available, although they may also feed to a lesser extent on aquatic insects (Beacham and McDonald 1982, Graynoth et al. 1986, Platts 1958, Lewis 1970 and 1971). Chironomids are usually considered to be a minor component of the diet of kokanee salmon (Clemmens 76
et al. 1939), but in Nicola Lake, Canada, chironomids constituted a major portion of the overall summer diet (Northcote and Lorz 1966). This is also the case in zooplankton-sparse Waldo Lake where chironomid larvae and pupae are the most commonly consumed taxa. Ephemeroptera larvae, odonata larvae, and coleoptera larvae were consumed to a lesser extent than chironomids. In lakes where zooplankton are not available it appears that kokanee salmon are able to feed on chironomids and other aquatic insects (Efford and Tsumura 1973, Graynoth et al. 1986). Vertebrates such as frogs, salamanders, and other fish were found infrequently in brook trout and rainbow trout stomachs in Waldo Lake and made up less than one percent of the total diet. This is probably due to the low abundance of these vertebrate species currently in Waldo Lake.
Reproduction of Fish in Waldo Lake There is evidence that all three species of fish in Waldo Lake are reproducing, but the extent of reproduction is unknown. Fry of all three species of fish were captured during the course of this study. In addition kokanee salmon and rainbow trout populations existing in Waldo Lake during this study must be derived from natural reproduction since, according to ODFW records, rainbow trout have not been stocked since 1979 and kokanee salmon were last stocked in 1970 (Table 7). Kokanee salmon and rainbow trout fry were captured in the bay near the outlet, as well as in the outlet itself. 77
Several brook trout fry were collected in the lake as well as some of the small ephemeral tributaries entering the lake. Brook trout juveniles were found in the small tributary that flows past the South Waldo Shelter. This tributary becomes intermittent during the summer making it unlikely that the fall spawning brook trout spawn in this stream during most years. Spawning for all three species of fish is apparently possible in Waldo Lake even though there are no permanent inlets entering the lake. Ricker(1932) and Wurtsbaugh and Brocksen (1975) found that brook trout were able to spawn in the shallows of lakes if underwater springs are available to oxygenate the eggs. Kokanee salmon are also thought to be able to spawn near springs or on gravel where there is significant wave action (Chapman and Fortune 1963). There are thought to be underwater springs located at the southern end of Waldo Lake where the majority of spawning activity for brook trout and kokanee salmon occurs in the late fall (ODFW, personal communication). Smith (1959) reported that in Lake Rotokawan and Blue Lake, New Zealand, rainbow trout were able to successfully spawn along sand and gravel areas that were sufficiently oxygenated due to wave action. Shoreline spawning may also be possible in Waldo Lake due to the cool water temperatures and the often present wave action along the eastern and western shorelines. 78
BIBLIOGRAPHY
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Allan, J.D. 1981. Determinants of diet of brook trout (Salvelinus fontinalis) in a mountain stream. Canadian Journal of Fisheries and Aquatic Science. 38: 184-192.
Allen, R.R. 1941. Studies on the biology of the early stages of salmon (Salmo salmar): 2. Feeding habits. Journal of Animal Ecology. 10: 47-76.
Aquatic Analysts. 1990. Waldo Lake water quality report. Department of Environmental Quality, Portland, Oregon.
Atkinson, N.J. 1932. A study of comparative results from stocking barren lakes with rainbow trout. Transactions of the American Fisheries Society. 62:197-201.
Benke, A.C. 1984. Secondary production of aquatic insects. Pages 289-322 in V.H. Resh and D.M. Rosenberg, editors. The Ecology of Aquatic Insects. Praeger Publishing, New York, New York.
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