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An Investigation of Arctic Char (Salvelinus Alpinus) and Lake Trout (Salvelinus Namaycush) in Lake Clark National Park, Alaska

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An Investigation of Arctic Char (Salvelinus Alpinus) and Lake Trout (Salvelinus Namaycush) in Lake Clark National Park, Alaska An Investigation of Arctic Char (Salvelinus alpinus) and Lake Trout (Salvelinus namaycush) in Lake Clark National Park, Alaska A Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science with a Major in Fishery Resources in the College of Graduate Studies University of Idaho by Ryan Kreiner November 7, 2006 Major Professor: Dennis Scarnecchia, Ph.D. ii AUTHORIZATION TO SUBMIT THESIS This thesis of Ryan Kreiner, submitted for the degree of Master of Science with a major in Fishery Resources and titled “An Investigation of Two Resident Fish Species in Lake Clark National Park, Alaska: Arctic Char (Salvelinus alpinus) and Lake Trout (Salvelinus namaycush),” has been reviewed in final form. Permission, as indicated by the signatures and dates given below, is now granted to submit final copies to the College of Graduate Studies for approval. Major Professor _____________________________Date______________ Dennis Scarnecchia, Ph.D. Committee Members _____________________________Date______________ Katy Kavanagh, Ph.D. _____________________________Date______________ Chris Peery, Ph.D. _____________________________Date______________ Carol Ann Woody, Ph.D. Department Administrator _____________________________Date______________ Kerry Reese, Ph.D. Discipline's College Dean _____________________________Date_______________ Steven Daley Laursen, Ph.D. Final Approval and Acceptance by the College of Graduate Studies ______________________________Date_______________ Margrit von Braun, Ph.D. iii ABSTRACT Anadromous sockeye salmon (Oncorhynchus nerka) are a keystone species for freshwater ecosystems, and in Lake Clark National Park, Alaska (LCNP), declines in salmon runs over the past 25 years have raised concerns about the health of resident fish species. Data on resident arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush) growth and condition from six lakes within LCNP were collected in 2004 and compared with an historical information collected by Russell (1980) during the summers of 1978-79. Four hypotheses were investigated: 1) arctic char and lake trout growth rates would be higher in lakes with sockeye salmon than in those without them; 2) arctic char and lake trout condition would be higher in lakes with sockeye salmon than in those without them; 3) arctic char and lake trout condition in 2004 would be lower than condition in 1978-79 in lakes with sockeye salmon coincident with declines in anadromous fish runs; 4) arctic char and lake trout diets would consist of sockeye salmon fry and eggs in those lakes with sockeye salmon. Growth of both resident species was not found to be faster in systems with anadromous sockeye salmon. It is more likely that a host of factors such as predation and available prey contributed to resident fish growth. Both species relied seasonally on sockeye salmon in the form of eggs and fry when available. This translated to a higher condition for lake trout but not for arctic char. Because ages of fish captured were needed to estimate growth rates, reader precision and bias of age estimation using two calcified structures, otoliths and pectoral fin rays, were also investigated for both species. Otoliths provided more reliable results than fin rays for both species. In arctic char, fin rays produced higher estimates 81% of the time. In lake trout, fin rays did not produce interpretable results. iv TABLE OF CONTENTS Page SIGNATURE PAGE............................................................................................. ii ABSTRACT..........................................................................................................iii TABLE OF CONTENTS ..................................................................................... v LIST OF TABLES ............................................................................................... vi LIST OF FIGURES ............................................................................................ vii ACKNOWLEDGEMENTS ..............................................................................viii Chapter 1. Growth and Condition of Arctic Char (Salvelinus alpinus) and Lake Trout (Salvelinus namaycush) in Lake Clark National Park, Alaska ........................ 1 ABSTRACT........................................................................................................... 2 INTRODUCTION................................................................................................. 3 STUDY SITE......................................................................................................... 7 METHODS .......................................................................................................... 12 RESULTS ............................................................................................................ 17 DISCUSSION ...................................................................................................... 31 LITERATURE CITED ...................................................................................... 38 Chapter 2. Precision and Bias for Two Methods of Aging Arctic Char (Salvelinus alpinus) and Lake Trout (Salvelinus namaycush).......................................... 45 ABSTRACT......................................................................................................... 46 INTRODUCTION............................................................................................... 47 METHODS .......................................................................................................... 50 RESULTS ............................................................................................................ 52 DISCUSSION ...................................................................................................... 65 LITERATURE CITED ...................................................................................... 67 v LIST OF TABLES Chapter 1 Table Page 1 Fish species present in study lakes........................................................................ 11 2 Starting sample dates from lakes in both studies (1980, 2004). ........................... 12 3 Von Bertalanffy parameters for lake trout in Lake Clark National Park, Alaska ................................................................................................................... 21 4 Percentages of arctic char stomachs containing specific prey items for lakes within Lake Clark National Park, Alaska.. ........................................................... 28 5 Percentages of lake trout stomachs containing specific prey items for lakes within Lake Clark National Park, Alaska. ............................................................ 30 Chapter 2 1 Sample sizes by lakes of arctic char and lake trout captured in Lake Clark National Park, Alaska. .......................................................................................... 50 2 Age frequency table of age estimates from arctic char otoliths from four populations in Lake Clark National Park, Alaska, in 2004................................... 53 3 Stock-specific age frequency table of age estimates from arctic char otoliths from four populations in Lake Clark National Park, Alaska, in 2004 .................. 54 4 Age frequency table of age estimates from lake trout otoliths from five populations in Lake Clark National Park, Alaska, in 2004................................... 56 5 Stock-specific age frequency table of age estimates from lake trout otoliths from five populations in Lake Clark National Park, Alaska, in 2004................... 57 6 Age frequency table of age estimates from arctic char fin rays from three populations in Lake Clark National Park, Alaska, in 2004................................... 59 7 Stock-specific age frequency table of age estimates from arctic char fin rays from three populations in Lake Clark National Park, Alaska, in 2004................. 60 8 Stock-specific age frequency table of age estimates from arctic char fin rays versus arctic char otoliths from three populations in Lake Clark National Park, Alaska, in 2004 ............................................................................. 64 vi LIST OF FIGURES Chapter 1 Figure Page 1 Map of Lake Clark National Park, Alaska, including lakes investigated in this study and barriers to anadromous salmon migration. ................................ 10 2 An example of a ground arctic char otolith and a whole lake trout otolith, displaying annuli................................................................................................... 14 3 Von Bertalanffy parameters for arctic char in Lake Clark National Park, Alaska… ............................................................................................................... 18 4 Length at age data from four populations of arctic char in Lake Clark National Park, Alaska, showing von Bertalanffy growth curves when obtainable.................................................................................................... 19 5 Length frequency histogram of artic char captured in 2004................................. 20 6 Length at age data from five populations of lake trout in Lake Clark National Park, Alaska, showing von Bertalanffy growth curves.......................... 22 7 Arctic char condition by lake and year ................................................................. 24 8 Condition (K) of arctic char plotted against total length of the fish .................... 25 9 Lake trout relative weight by lake and year.........................................................
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