6,1,-tSn A STUDY OF LIMNOLOGICAL CONDITIONS OF SKEENA LAKES AS THEY AFFECT THE DISTRIBUTION AND ABUNDANCE OF THE 1HITEFISHES COREGONUS AND PROSOPIUM By Harold Godfrey A Thesis submitted in Partial Fulfilment of the Requirements for the Degree of MASTER OF ARTS in the Department of ZOOLOGY THE UNIVERSITY OF BRITISH COLUMBIA April, 1949. ii ABSTRACT Limnological conditions in lakes of the Skeena drainage, British Columbia,have been examined to asoertain what factors may be restricting the distribution and/or abundance of the Eastern and Rooky Mountain whitefishes. The Eastern whitefish is known to be in only four Skeena lakes, and the Rooky. Mountain whitefish in all Skeena lakes which have been investigated. It is probable that the Eastern whitefish has not entered other Skeena lakes because the lake conditions are not suitable for its establishment. Such conditions are mainly warm waters, shallow depths, and small area; and are sometimes the heavy silting of the water, and the resultant poor food supply. It is not numerous in any of the four lakes, probably because of the relative poor abundance of bottom food organisms, particularly in the absence of such organisms as the amphipod Ppntoporeia. Conditions are apparently most favourable for Eastern whitefish in oligotrophia lakes. Rocky Mountain whitefish appear to favour eutrophic lakes, and are most abundant in lakes where a good supply of bottom food is assured by the absence of such potential competitors as the Peamouth chub and Squawfish. There is no evidence of any heavy predation on either of the two whitefish. It is improbable that any physioal barrier has limited the distribution of these fish. • • • * ooo .•.• TABLE OF CONTENTS» Page. Abstract ii Introduction 1 Acknowledgements 2 Systematic Position 3 Distribution in North America 4 The Skeena Drainage 6 Distribution of Eastern and Rocky Mountain IShitefish 8 Climate 13 Geology of the Skeena Lakes 16 Morphometrical and Physioo-Chemioal Characteristics .... 20 Introduction 20 Materials and methods 20 Lakelse lake 22 Babine lake 28 Morrison lake 33 Other lakes 37 Summary and significance 38 The Bathymetric Distribution of Eastern and Rocky Mountain TOiitefish 45 Introduction 45 Treatment of netting data ....... 46 Distribution of Rocky Mountain whitefish in Lakelse lake 49 Distribution of Rooky Mountain whitefish in Babine lake 52 Distribution of Eastern whitefish in Babine lake 55 Catoh of both species in different Positions in Babine lake 58 Distribution of Eastern whitefish in Morrison lake 62 Summary and comparisons 65 The Pood of the Whitefishes 68 Materials and methods 66 Food of Rocky Mountain whitefish in Lakelse lake 69 Food of Rocky Mountain whitefish in Babine lake 74 Food of Rocky Mountain whitefish in Morrison lake 78 Discussion 80 Food of Eastern whitefish in Babine lake ....... 81 Food of Eastern whitefish in Morrison lake ...... 84 Discussion 86 Summary 88 Bottom Fauna 91 The bottom fauna of Lakelse lake 91 Introduction • 91 Methods and materials 91 Results 94 TABLE OF CONTENTS. Cont'd. Page_. Characteristics of the distribution of six major groups 94 Abundanoe of bottom fauna in relation to distance from shore 100 Further considerations on the distribution of bottom fauna 102 The bottom fauna of Babine lake 104 The bottom fauna of Morrison lake 107 Comparison with other lakes 108 The Food of the Whitefishes in Relation to Supply 112 Lakelse lake 112 A Note on Mysis 115 Competitors for Food of Whitefish 117 Introduction 117 Materials and methods 118 Peamouth chub . 119 Squawfish 125 Cutthroat trout 131 Dolly Varden char 140 Northern and Common suckers ....... 140 Summary 148 Predation on Eastern and Rooky Mountain whitefish 150 Introduction 150 Cutthroat trout 151 Squawfish 153 Dolly Varden char . 154 Lake Trout 154 Rainbow trout 154 Burbot V 157 Discussion 157 Growth Rates 161 Growth of the Eastern whitefish in Babine and Morrison lakes 161 Growth of the Rooky Mountain whitefish in Lakelse and Babine 163 Comparisons of Body Proportions . 165 Factors Limiting Distribution 167 Rocky Mountain whitefish 167 Eastern whitefish ... 167 Summary • 174 Factors Limiting Abundanoe 175 Rocky Mountain whitefish 175 Eastern whitefish 180 TABLE OF CONTENTS. Cont'd. Page. Summary and. Conclusions ... 186 Literature oited • 193 Appendix 197 .•.. OOO •.•• LIST OF FIGURES. Page. Fig. 1. Map of the Skeena river showing the known dis• tribution of Rocky Mountain ( ) and Eastern whitefish (#) 7 Fig. 2. Average monthly precipitation and air temperatures at various points within the Skeena drainage ... 14 Fig. 3. Map of Lakelee lake showing bottom contour lines and dredging lines 23 Fig. 4. Water temperatures of Lakelse lake, 1946 - 1948 25 Fig. 5. Map of Babine lake showing bottom contour lines 29, Fig. 6. Water temperatures of Babine lake, Divisions II and III, 1946 31 Fig. 7. Map of Morrison lake showing bottom contour lines 34 Fig. 8. Catch per net-night per mesh of Rooky Mountain whitefish at different depths in Lakelse lake. Data of 1946 and 1947 oombined 51 Fig. 9. Catch per net-night per mesh of Rocky Mountain whitefish at different depths in Babine lake. Data of Divisions I and II for 1946 and 1947 combined 54 Fig. 10. Catch per net-night per mesh of Eastern whitefish at different depths in Babine lake. Data of Divisions I and II for 1946 and 1947 oombined 57 Fig. 11. Catch per net-night per mesh of Eastern whitefish at different depths in Morrison lake. Data of 1946 and 1947 oombined . 64 Fig. 12. The relative abundance of six major groups of bottom organisms at different depths in Lakelse lake, 1946 97 Fig. 13. The distribution of the Ephemerida, the Chironomidae and the Gastropoda in Lakelse lake, 1945 99 Fig. 14. The distribution of the Peleoypoda, the Trichoptera, and the Amphipoda in Lakelse lake, 1945 101 Fig. 15. The relative abundance of bottom fauna in Lakelse lake at different distances from shore, and showing the average depths of such distances, 1945 103 Fig. 16. Catch per net-night per mesh of Cutthroat trout, Squawfish and Peamouth ohub at different depths in Lakelse lake. Data of 1946 and 1947 oombined 123 Fig. 17. View of Lakelse lake from the east shore. Lakelse river a little right of oentre. 198 Fig. 18. Aerial view of Lakelse lake and Lakelse river. 198 Fig. 19. Aerial view of Babine lake. The north-west arm in the background ..... ..... 199 Fig. 20. View of Babine lake. Looking towards Old Fort 199 ..•. ooo .•*. INTRODUCTION. Sinoe 1944 the Pacific Biologioal Station has conducted investigations concerned -with the Skeena river salmon populations. It has long been rea• lized that the mortality of young salmon is particularly high during their lacustrine phase, and the investigators, therefore, have direoted considerable effort and attention towards the conditions obtaining in the Skeena's lakes and streams. This has made possible the collection of muoh_data and Z .material pertaining to other freshwater fishes, and in particular, has provided for this present study of the whitefishes of the Skeena drainage. Sinoe, however, the whitefishes were not of especial importance to the salmon investigations, there are many occasions in which the data necessary for their thorough study are meagre or lacking. The two whitefishes present in the Skeena are the Common or Eastern whitefish, Coregonus clupeaformis (Mitohill), and the Rooky Mountain white- fish, Prosopium williamsoni (Girard). The Common whitefish is apparently limited in its distribution to only four of the Skeena lakes; the Rocky Mountain whitefish on the other hand is of universal occurrence throughout the drainage, though in places it is not particularly abundant. The present problem has been to determine what faotors may be limiting the abundance and distribution of the two whitefishes in certain of the Skeena lakes. This has been approached by examining the available material and data pertinent to the identification and distribution of the two speoieB throughout the drainage, and by defining their ecological dis• tribution, food and relative abundance of food, competition for food, predation, and the physical, ohemioal and biological conditions obtained in the waters they inhabit. ACKNOWLEDGEMENTS. Dr. R. E. Foerster, Director of the Paoifio Biological Station at Nanaimo, and Dr. A. L. Pritchard, until recently in oharge of the Skeena salmon investigations, and now Director of Fish Culture Development at Ontario, have generously permitted the use of the material and data neoessary for the preparation of this paper. The writer would like to thank Dr. W. A. Clemens, Dr. P. A. Larkin and Dr. W. S, Hoar of the Department of Zoology of this University for their kind assistance and for helpful critioism of these efforts. Mr. J. A. McConneH of the staff of the Pacific Biological Station made many of the fish stomach analyses used here, and has frequently been of great help in collecting various data. The writer is pleased to acknowledge the generous help of his fellow field workers. While in attendance at this University during the past year, the writer has received a Bursary from the National Researoh Counoil of Canada, and he would like to take this opportunity to express his thanks to the Council. •... ooo •••. 3 SYSTEMATIC POSITION. Th» family Salmonidae were formerly divided into two sub-families, the Salmoninae and the Coregoninae. Recent American practice reoognizes the two distinct families Salmonidae (salmon and trout) and Coregonidae (white- fish and lake herring). Regan and most other European ichthyologists included within the genus Cpregonus all the known species of whitefish and lake herring. Jordan and Evermann(l91l), however, have given generic or sub-generic status to several minor groups of species, placing the whitefishes in the genus Cpregonus, under the subgenera Cpregonus and Prosopium. Koelz (1927) recognizes the three groups Leuoichthys, Cpregonus and Proaopium as distinot genera, and disregards the sub-genera of Jordan and Evermann.