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CENTRE FOR NEWFOUNDLAND STUDIES ' TOTAL OF 10 PAGES ONLY MAY BE XER0XED (Without Author's Permission) ECOLOGY AND COMPARATIVE POPULATION DYNAMICS OF ANADROMOUS ARCTIC CHARR, SALVELINUS ALPINUS (LINNAEUS 1758), IN NORTHERN LABRADOR by ~©J. Brian Dempson, B.Sc. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Biology Memorial University of Newfoundland March 1982 St. John's Newfoundland i i ABSTRACT Biological characteristics and population dynami"cs of northern Labrador anadromous Arctic charr (Salvelinus alpinus) were investigated. Univariate and multivariate statistical analyses were performed on nine meristic and thirteen morphometric characters of charr samples from various northern Labrador areas. Variation in meristic characters was slight, although significant differences between samples indicated the discrete nature of the stocks. Differences in growth rate, age at maturity, and movement patterns of tagged fish corroborated results of morphological analyses. Biological characteristics including age, growth, movement patterns and aspects of reproduction were examined in Fraser River Arctic charr. No consistent differences in growth rate were found between male and female charr. Upstream migration from the sea began in mid-July with a tendency for larger fish to enter the river first. Average size and age of upstream migrants were 45.1 em and 8.3 years respectively. Biological characteristics of commercially exploited and unexploited Labrador charr populations were examined. Mean age of charr increased with latitude. Commercial exploitation has reduced the proportion of charr greater than 2.3 kg (gutted head-on weight) in commercial catches. Mean length of catches, however, has remained relatively constant in several areas. Total instantaneous mortality rates varied from 0.48 to 0.83 in exploited areas to 0.28 and 0.29 in unexploited populations. iii Comparisons between northern Labrador Arctic charr and charr from other regions are discussed with respect to movement patterns, size, age and reproductive characteristics. Labrador· charr migrated to sea for the first time at smaller sizes (7.8-19.1 em) but comparable ages (3-7 years) with Arctic charr from other regions. Egg production in Fraser River charr was intermediate between charr from eastern and central Arctic regions, and those from the Western Arctic. Female Fraser River charr were estimated to produce 245 eggs 100 g- 1 . Commercially exploited Labrador Arctic charr populations were generally smaller and younger than exploited charr stocks in the Northwest Territories. iv ACKNOWLEDGEMENTS I would like to express my sincere appreciation to Dr. J. M. Green, Department of Biology, for his advice, encouragement and patience during the supervision of this study. Thanks are also extended to Drs. D. Steele and D. Larson for critically reading the manuscript and providing organizational and editorial advice. I am grateful to Rex Porter and Dr. John Pippy, Freshwater and Anadromous Fisheries Management Program, Department of Fisheries and Oceans, for their cooperation and continuous support of this project. Particular thanks are also given to Larry LeDrew, George Furey and Terry Nicholls for their varied assistance during field investigations. Computing and statistical advice were kindly given by D. Stansbury, G. Somerton and Dr. R. Misra. The cooperation of personnel at the Nain Fish Plant especially Jim, Sue and Sarah Webb is gratefully acknowledged. My sincere thanks are also extended to Dr. Lionel Johnson 11 11 corresponding consultant , R. Peet, B. Moshenko, A. Kristofferson and R. 11 Billy11 Baker of the Freshwater Institute, Winnipeg, for their numerous interesting and stimulating discussions regarding the biology and population dynamics of Arctic charr. Finally, my sincere appreciation is given to Glenda Thomas for her support and encouragement especially during the final time consuming stages of this project. To Patsy Doyle, Janice Lannon, and Karen Scott, many thanks for your cooperation, patience and humor in typing, correcting and retyping various stages of this manuscript. v TABLE OF CONTENTS PAGE ABSTRACT ii ACKNOWLEDGEMENTS iv LIST OF TABLES vii LIST OF FIGURES xi LIST OF APPENDICIES xiii 1. INTRODUCTION 1 2. DESCRIPTION OF STUDY AREA 10 3. MATERIALS AND METHODS 14 3. 1. STOCK DETERMINATION 14 3. 1. 1. Collection and preparation of samples 14 3. 1. 2. Meristic and morphometric measurements 14 3. 1. 3. Statistical analyses 17 3. 1. 4. Tagging 20 3.2. LIFE HISTORY 23 3.2. 1. Age determination 23 3.2.2. Biological sampling 23 3.3. COMPARATIVE POPULATION DYNAMICS 27 3. 3. 1. Catch and effort data 27 3.3.2. Commercial sampling 28 3.3.3. Research sampling 29 3.3.4. Estimation of mortality rate 30 4. RESULTS 31 4. 1. STOCK DETERMINATION 31 4. 1. 1. Analysis of meristic and morphometric data 31 4. 1.2. Distribution patterns 34 vi PAGE 4.2. LIFE HISTORY 44 4.2. 1. Age and growth 44 4.2. 1. 1. Juvenile growth pattern 44 4.2. 1.2. Age-length and age-weight 47 relationship 4.2. 1.3. Weight-length relationship 58 4.2.2. Migration 60 4.2.2. 1. Size and age at first seaward 60 migration 4.2.2.2. Annual and seasonal movements 62 4.2.2.3. Time and duration of upstream 64 migration 4.2.2.4. Age and size composition of 68 upstream migration 4.2.3. Reproduction 69 4.2.3. 1. Sex ratio 69 4.2.3.2. Age and size at maturity 75 4.2.3.3. Time and location of spawning 77 4.2.3.4. Maturity index, egg size and 79 fecundity 4.3. COMPARATIVE POPULATION DYNAMICS 81 4. 3. l. Catch and effort data 81 4.3.2. Age and size composition of the catch 88 4.3.3. Age and growth comparison 108 4.3.4. Weight-length relationship 118 4.3.5. Sex ratio and spawning stock composition 123 4.3.6. Age and size at maturity 126 4.3.7. Mortality rate 128 5. DISCUSSION 139 6. SUMMARY 159 REFERENCES 161 APPENDICES 171 vii LIST OF TABLES TABLE PAGE 1 Summary of monthly temperature (°C) and precipitation 12 (mm) data at Hopedale, Labrador (55°28'N, 60°l3'W) for the period 1960-1979. 2 Summary of research samples of northern Labrador 15 Arctic charr available from 1978-1980 for analysis of meristic, morphometric and biological characteristics. 3 Meristic and morphometric characters examined on 16 northern Labrador Arctic charr and designated abbreviations. 4 Summary by area and year of Arctic charr tag recaptures 21 in northern Labrador. 5 Univariate statistics for meristic and morphometric 32 characters from northern Labrador Arctic charr. Analysis of variance results including Levene's test of heteroscedasticity and multiple comparison tests of meristic characters. Statistical analyses based on transformed (~X+ 0.5; Sokal and Rohlf 1969) meristic data. Significance levels are P<O.OS(*) and P<O.Ol(**). Underlined areas are not significantly different. 6 Summary of multivariate analysis of variance 33 of Arctic charr morphometric characters (above diagonal) and percent correctly classified by discriminant analysis (below diagonal). Significance levels are P<0.05 (*) and P<0.01 (**). 7 Comparison of mean length at age between male and 46 female Arctic charr, with age-weight relationship from Fraser River, 1975-1979. Significance levels are P<0.05 (*) and P<O . Ol (**). 8 Age-length key for Fraser River Arctic charr samples, 48 1975-1979. 9 Annual growth increments in Fraser River Arctic 54 charr summarized by 5 centimeter length intervals as derived from tag recaptures. 10 Annual growth increments in Fraser River Arctic 55 charr summarized by age group as derived from tag recaptures. viii TABLE PAGE 11 Linear regressions of lt+i on lt with estimates of L00 57 and K derived from tag recaptured Fraser River Arctic charr. 12 Weight-length relationships derived from various research 59 samples of northern Labrador Arctic charr. 13 Length at age relationship for Arctic charr juveniles 63 captured in Nain Bay during 1979 and 1980. 14 Mean weekly temperatures and total number of upstream 67 migrating Arctic charr recorded at Fraser River, Labrador, 1975-1979. 15 Mean length (em) and weight (kg) by week of upstream 74 migrant Arctic charr in the Fraser River, Labrador, 1975-1979. 16 Age specific sex ratios and age at maturity for Fraser 76 River Arctic charr, 1975-1979. Sex ratios compared by chi-squared analyses (Elliott 1977). Significance levels are P<0.05 (*)and P<O.Ol (**)for deviations from a l:l sex ratio. 17 Relationship between maturity index, gonad weight and 80 egg diameter in Fraser River Arctic charr, 1979. 18 Summary of catch (kg round), effort, and size composition 85 statistics for individual areas within the Nain fishing region, 1974-1980. Size composition expressed as proportion of landings greater than 2.3 kg (gutted head-on). 19 Summary of age samples available from the commercial 89 northern Labrador Arctic charr fishery, 1977-1980. 20 Summary of age, length and weight data for commercially 90 caught Arctic charr from Voisey Bay, 1977-1980. 21 Summary of age, length, and weight data for commercially 91 caught Arctic charr from Tikkoatokak Bay, 1977-1980. 22 Summary of age, length, and weight data for commercially 92 caught Arctic charr from Okak Bay, 1977-1980. 23 Summary of age, length, and weight data for commercially 93 caught Arctic charr from Hebron Fiord, 1977 and 1980. ix TABLE PAGE 24 Estimated numbers at age for Arctic charr caught in 94 Voisey Bay, 1977-1980 (A) with catch per unit effort by age (B) and Paloheimo total mortality rates (C). · 25 Estimated numbers at age for Arctic charr caught in 95 Tikkoatokak Bay, 1977-1980 (A) with catch per unit effort by age (B) and Paloheimo total mortality rates (C) . 26 Estimated numbers at age for Arctic charr caught in Okak 96 Bay, 1977-1980 (A) with catch per unit effort by age (B) and Paloheimo total mortality rates (C).