Age, Growth, and Diet of Fish in the Waldo Lake Natural-Cultural System
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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.