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. Koelz*a practice is followed in this paper.
The genus Cpregonus was established by Linnaeus. Subsequent in• adequate or erroneous descriptions, and the wide variability of the group have led to faulty records of distribution and to considerable synonymy.
The generic status of Prosopium first appeared in Hubb's oheok list of the fishes of the Great Lakes (1926), but Hubbs (MoHogh, 1938) attributes the recognition of Prosopium as a distinot genus to Koelz (1927). Within this group, too, many synonyms have been established.
The Coregonidae, in oommon with other salmonid fishes are confined to north-temperate and to sub-arctic regions, and their distribution is oircumpolar (Dymond and Valdykov 1933). Their evolution is comparatively recent (Jordan and Evermann 1896), and is probably from a freshwater olupeoid ancestor (MaeFarlane 1923). DISTRIBUTION IN NORTH AMERICA.
In addition to the list of synonyms of Coregonus clupeaformis given by Koelz (1927), Dymbnd (1943) has recently reduced to its synonymy the following forms described for northwestern Canada; C. nelsonii Bean,
C. Kenniootti Bean, C. odonoghuel Bajkov, and C. atikameg Bajkov. He has also placed Bajkov's record of the C. nasns in Canada in the synonymy of
C. clupeaformis. Dymond's conclusions have not been acoepted by Fowler
(1947) or Harper (1947) who still prescribe to the forms C. odonoghuel and C. atikameg as originally desoribed by Bajkov. From collections made by Harper in the Hudson bay region of Keewatin a^d Manitoba, Fowler has desoribed specimens of C. a. atikameg and C. a. manitobenBJs. Fowler admits the inadequacies of Bajkov's original description of C. atikameg, yet describes his specimens as such on the basis of the slender body; dark colour of both back and fins; lack of black spots on scales, dorsal and adipose fins; the nearly-straight upper profile of iiie head; the long maxilla nearly reaching the eye; and the habitat of braokish and salt water. He states that he is "unable to agree" with Dymond's conclusions on the synonymy of atikameg with clupeaformis, "at least until more evi• dence is forthcoming". Fowler's recognition of atikameg in Harper's collections is based on the examination of two specimens. In view of the fact, that, as Dymond (1943) says, "it is hardly necessary to say that colour is influenced by the oharaoter of the waters in whioh the fish live", it would seem more appropriate to await further evidence before describing the new species. In his original description Bajkov states that the gill-raker count (25) of atikameg is less than that of clupeaformis.
Of the two specimens desoribed by Fowler, the gill-raker count is given for only one, and is 28. Harper (1947) in reference to previous records of the Common whitefish from northwestern Canada, states, "... many of them under the name of Cpregonus clupeaformis although it is hardly likely that the name is applicable to the fishes of this region"*
There seems little doubt that, though subject to considerable variation in colour and form, Cpregonus clupeaformis is the only distinct species of the genus in North America, and is widely distributed on the continent* It is found in the eastern provinoes; and in the Great Lakes and the large prairie lakes it ooours in such abundance as to constitute
Canada's most important freshwater fishery. The species is anadromous in the Hudson bay region (Dymond 1933), end in the Alaskan arctic, entering the rivers and lakes to spawn. It is present in the Yukon and in.northern
British Columbia west of the Rooky Mountains, and has been introduced into lakes of southern British Columbia.
In contrast to the Common whitefish, the Rocky Mountain whitefish is restricted in its distribution to regions west of the Rocky Mountains,
(although according to Radforth, 1944, it has orossed these mountains at certain points), and in British Columbia to more southerly lakes and streams, though its known northward distribution has been extended by reoords of the Skeena and Fraser salmon investigations beyond that des• cribed earlier by Dymond (1935). The known occurrence of this fish in
British Columbia is given by Carl and Clemens (1948). Jordan, et al
(1930) give its distribution as followsi "Rivers of Sierra Nevada and west slope of Rocky Mountains, from the Fraser and the Columbia to the
Truckee and other streams of the Lahontan basin of Nevada; abundant especially in lakes of Northern Idaho, Western Montana, Washington and
Utah". THE SKEENA DRAINAGE.
Details of the Skeeaa drainage and of its tributory units (North
Skeena unit, Babine unit and Morice unit) are illustrated in the nap of
Fig.Z'. The total drainage of the Skeena is approximately 19,300 square miles. In the north it arises in the Kluayaz - Duti river systems at
57° 12' N. Lat., 127° 45' W. Long, and extends approximately 245 miles to its southern limit in the Nanika lake district of the Morice system, at
53° 40* N. Lat., 127° 50' W. Long. It originates at its eastern limits from the headwaters of the Sutherland river (a small tributory to Babine
Lake) at 54° 16' N. Lat., 124° 40* W. Long., and extends westward for approximately 220 miles to its mouth at a point about 15 miles south east of Prinoe Rupert on the Pacific coast,vat 54° 10' N. Lat., 130° 10' W.
Long. Its highest recorded point of drainage is from Johanson lake at
4730 feet, and between Hazelton and Prince Rupert its valley transects the coastal range of mountains. More than 75% of the Skeena drainage is within the oentral plateau, east of the Coast mountains, at an elevation greater than 2000 feet. 7
Kluoyaz IL . S
Kluatantan L. w
dohanion L. 9u«lu) L.
»»l\ko L. t^* SKEENA RIVER Damthllgwl t Slamgttth L
0 10 20 \8lir R
Uigtlot , l. SKEENA R.\
Shtlogyori R. \Nllkitkwa R.
^Gunono o t
' Ki tpi ox BABINE R.
Kitwanga L. • Nilkltkwo L. ^For*ry£abln«
\Morr lion l. ^
tforicttown Foil*
BttLKLEY R.
itfofrt-Ojf Ldj. iBMITHERS Fulton R. Klttumgallam
/Bulkloy R. Donaldt ^opptr R. Ldo.
^.AKELTSE L. y**
VAtaitair L.
MORICE L. Ecitoll R. ^NanNio R.
Johnst on ^Noniko L.
/Kidprieo L.
Fig. 1. Map of the Skeena river showing the known distribution of Rocky Mountain and Eastern whitefish (#). 8
DISTRIBUTION OF EASTERN AND ROCKY MOUNTAIN TOITEFISH IH THE SKEENA SYSTEM,
Lakes which are known to contain either of the two speoies of whitefishes are indicated in Fig. 1 . Their distribution in the Skeena lakes is also shown in Table X together with the known distribution of certain other fishes.
The Rooky Mountain whitefish is the most widely distributed fish of any that are known to occur in the Skeena system. It has been found, and generally in fair abundance, in every lake investigated. It is also known, by observation, to inhabit numerous streams and rivers. The lakes in which Rooky Mountain whitefish are found vary from deep, cold and opaque waters, to small, shallow and warm "ponds".
The Eastern whitefish has been netted in only four lakes. These are Babine, Morrison, Bear and Atuklotz. However, many of the lakes were investigated by only single and short visits, and no doubt collections from these lakes were incomplete. I*kes which by virtue of a fair number of sets (Table ZJ[ ) should have provided some evidence of the presenoe of the Eastern whitefish if they were there, are Morice, Lakelse, and
Nilkitkwa. Without doubt no Eastern whitefish are present in either
Lakelse or Morice lakes. The fish may very likely move out of Babine lake the short distance down the upper Babine river into Nilkitkwa lake, but it is not likely that many remain in the lake, sinoe much of it is very shallow and often warm. A fair number of sets have been made in Stephens and Swan lakes. Eastern whitefish are not definitely listed for either lake, but some doubt is entailed due to the misplacing of a specimen whioh was sent down to Nanaimo for identification, and which, apparently, might have been an Eastern whitefish. It is fairly certain that Kitwanga, f
TABLE I..
THE KNOWN DISTRIBUTION OF SOME OF THE FISHES PRESENT IN THESKEEN A LAKES
LAKELSE BABINE MORRISON BEAR NILKITKWA KITWANGA KITSUMOaLUM ALASTAIR STEPHENS SWAM MOTASE AKJKLOTZ SUSTUT JOHANSON KLUAYAZ DAMSHILGWIT SLAMGEESH MORIC E
EFFORT - NO. OF GANGS SET # • A A A B C D D E D D E D E E E E E c
1 EASTERN WHITEFISH X X X x
ROCKY MOUNTAIN X X X X X X X X X X X X X X X X X WHITEFISH
PEAMOUTH CHUB X X X X X X X
SQUAWFISH X • X X X X
CUTTHROAT TROUT X X X X X X X
DOLLY VARDEN CHAR X X X X X X X X X X X X X X
RAINBOW TROUT X X X X X X X X X ' x X X
NORTHERN SUCKER X X X X X X X X X X X X X
COMMON SUCKER X X X X X
COLOMBIA LARGE X SCALED SUCKER
BURBOT X X X X X X X LAKE TROUT (CHAR) X X X X
# A - More than 50 gangs set B - Between 20 and 50 gangs set C - Between 10 and 20 gangs set D - Between 5 and 10 gangs set E - Less than 5 gangs set Kitsumgalum and Alastair lakes carry no Eastern whitefish* Only a few sets were made in Kluayaz, Damshilgwit, Slamgeesh, Johanson, Sustut and Motase
lakes. Although it cannot be said definitely that no Eastern whitefish
are present in these lakes, there is little doubt that in none of them are
there any large populations. No sets have been made in Asitka lake.
The distribution of the Eastern whitefish, is probably restricted to
the more northern Skeena lakes and to lakes of the Babine drainage.
Apparently it has not yet moved down the* Skeena river, nor crossed the
oentral plateau to lakes west of the Coast Range mountains.
The Burbot, or Ling, is found in the same lakes as the Eastern whitefish, and in two other lakes only, Nilkitkwa and Sustut. The Dolly
Varden char follows the Rooky Mountain whitefish in the extent of its
distribution. It has been found in every Skeena lake investigated with
the exception of the lakes of the Babine system, Babine, Nilkitkwa and
Morrison lakes. (It is not recorded for Kluayaz lake, but only a few
sets were made in this lake). The Lake trout (Great Lakes char) is
found in company with the Dolly Varden char only in Morice and Bear
lakes, and it is present in the three lakes where no Dolly Varden occur.
It is found in only two lakes, Nilkitkwa and Morice, where there are no
Eastern whitefish.
Either Cutthroat or Rainbow trout are present in almost all the lakes.
In only four lakes have they been reoorded as being present together.
Peamouth chub and Squawfish, which are abundant in some lakes, ocour
in lakes west of the Coast Range (Lakelse, Kitwanga and/or Kitsumgalum), and
in the Babine lakes of the oentral plateau. None have been recorded from
any of the more northerly lakes. The Northern suoker has a wide distribution. The Common or White
suoker is found only in the Babine or northern lakes east of the Coast
Range; there is doubt, apparently, as to its presenoe in Kitwanga lake.
Only one specimen of the Columbia Large-soaled suoker has been taken,
and that in Lakelse lake in 1948.
Other species, which have been either gilled, seined or observed
in Skeena lakes are Kokanee, Soulpin, Threespined stickleback, Lake
shiner, Chub minnow, Longnose dace, Red bellied dace, and the five species
of Pacific salmon.
The scientific names of these fish are as follows:
Eastern (Common) whitefish Coregonns clupeaformis Rooky Mountain whitefish •Prosopium williamsonl Burbot (Ling) Lota maculosa Dolly Varden ohar Salvelinus malma speotabilis Lake trout Cristivomer namaycush Rainbow trout Salmo gairdnerii Cutthroat trout Salmo olarkli Peamouth ohub locheilns caurinus Squawfish chooheilus oregonensls Northern (Longnose) sucker Catastomns oatastomus Common (white/ sucker Catastomns commersonii Columbia Large-scaled suoker Catastomus maorooheilus Sculpin Cottus asper Threespined sticklebaok gasterosteus aouleatus Lake shiner Richardsonius balteatus Chub minnow Couesius greeni Longnose daoe Rhinlchthys cataraotae Red bellied daoe Uhrosomus eos. Kokanee Onoorhynchns nerka kennerlyi Spring salmon tschawytsoha Chum salmon Keta Coho salmon " tXsutoh Sockeye salmon " nerka Pink salmon " gorbusoha
At this point a matter of certain interest and importance can be
introduced. Dr. William H. WMte of the Department of Geology of this
University has called the writer's attention to the faot that there is an apparent connection by way of the north Skeena drainage and the Peace river system between the Pacific and Arctic Oceans. The Continental
Divide, in the vioinity of McConnel creek and the Sustut river is a flat expanse of boggy terrain, in which there are numerous small lakes and streams. The condition is such that water connections between the Pacifio and Arctic drainage systems are probable. The following is a statement which Dr. White has been kind enough to make:
"The Sustut river and tributaries (tributary to the Skeena system) and the Ingenika river (tributary to the Peace system) head in a network of broad valleys or intermontaine plains oooupied by muskeg, small lakes, and a dendritic pattern of tiny inter-connecting sluggish streams. In times of moderate and high water it is probable that water connections exist between the Pacific and Arctic drainage systems in this area.
McConnel creek, in the northern part of this area, issues from an upland plateau area east of McConnel lakes and actually splits in the low-lying, level valley south of the lakes. Part joins the Arctic drainage system, and the remainder by a devious route joins the Sustut-Skeena system. This split, is however, a very temporary drainage feature whioh has not been in existence for very long (oertainly post-Pleistocene) and which will not persist for long".
Dr. White also told the writer that he has taken trout and whitefish from McConnel lake. The trout, by his description were probably cutthroat, and the whitefish would seem to have been either Rocky Mountain, or the
Round whitefish (Prosopium cylindraceunx). CLIMATE.
The three primary factors which effect the variations of climatic conditions throughout the Skeena drainage are, (a) the river's route eastward from the coast, (b) its transection of the coastal range of mountains into the central plateau, and (c) its gradual elevation above sea level. The important local conditions affecting certain lakes are those attributable to high altitude, and enclosure by mountains.
Average monthly temperatures for Prince Rupert, Terrace, Telkwa and Fort St. James are given in Fig. ZJ • average monthly precipitation for Prince Rupert, Terraoe and Babine lake are given in Fig. Z.
Precipitation is extremely high in the coastal region and deoreases gr^ually as the western slopes of the coastal mountains are approached.
Beyond these mountains the decrease in rainfall is more abrupt (Fig. Z\
The climate of Terrace and Lakelse lake is further influenced by their situation in the Kitsumgallum-Lakelse valley which follows northward from the Kitimat arm, on the coast, and crosses at right angles to the main eastern Skeena valley. Strong, rain-bearing winds sweeping up this valley are, apparently, quite frequent. Two hundred and fifty miles from the coast in the region of Babine lake and Fort St. James, whose altitudes approach 2500 feet, precipitation is relatively light and is fairly uni• form throughout the year.
Greater extremes of winter and summer temperatures are experienced on the central plateau than in the coastal region. Average August and
January temperatures for Prince Rupert are 57°F and 35°F; for Terraoe
62°F and 25°F; and for ff&rt St. James 56°F and 10°F. Fig. 2. Average monthly precipitation and air temperatures at various
points within the Skeena drainage. /S
In general isothermal conditions and winds follow the direction of the mountain ranges which run northwest and southesst.
Local variations due to altitude and to protection by close surrounding hills are no doubt of greater magnitude than those effeoted by the differences in latitude between the northern and southern reaches of the Skeena.
The average number of hours of bright sunshine for Prince Rupert and Smithers are given below; they are representative of conditions within the coastal and central plateau regions.
Average number of hours of bright sunshine:
JFMA H J J A S OND TOTAL Prince Rupert: 37 60 79 104 141 125 119 122 98 55 41 32 1013
Smithers: 41 87156 166 290 221 173 219 144 76 66 17 1650
No. of Years: Prince Rupert - 26
" " " Smithers - 34 GEOLOGY OF THE SKEENA LAKES.
Introduction.
Str/6m (1928) has said of a lake that it owes its peouliar character to the affects of two conflicting tendencies, the first being the tendency of a lake to exist as an independent miorocosm, where the evolution of its life processes is determined by the morphology of its basin; and the
second, the tendency that works towards making lakes mere produots of their substrates and drainage areas. Rawson (1930, 1941) suggests that though the 'type' of the lake has more influence on its fauna than has its geologioal setting, the 'type' itself is affected by the nature of the surrounding country. He also states (1939) that "while edaphie factors determine the kinds and amounts of primary nutritive materials, the morphology of the basin, and the climate may to a large extent determine the utilization of those materials".
The geology of the Skeena lakes themselves has not been investigated, but considerable portions of that part of the province have been surveyed by the geological branoji of the Department of Mines and Resources.
Lakelse and Kitsumgallum Lakes.
Lakelse and Kitsumgallum lakes lie in an ancient valley (the
Kitsumgallum-Lakelse valley) which extends northward from the Kitimat
arm and crosses the main Skeena valley at right angles. The valley re•
presents part of an old drainage system robbed by the lower Skeena, in
Tertiary or Pleistocene times, although it is possible that the Skeena
itself may have been robbed in still earlier times (Cretaceous, perhaps) by the Lakelse - Kitsumgallum system (McConnel 1912). The floor of this valley is covered by extensive gravel deposits, and gravel terraces occur up to 200 feet above all the larger lakes and streams. These deposits were presumably laid down during the wane of the Glacial period and in Recent time through extensive deposition by overloaded streams and deepening of the river channels. Pleistocene and Recent formations are evidenced by the scattered glacial boulders found over the whole area, and glacial striae are present in many plaoes parallel to the main valley8. The mountains which rise precipitously above the valley are part of the Coast Range batholith, comprising Triassio, Jurassic and
Cretaceous rocks. Formation of the Upper Jurassio (Cretaceous) dominate' the drainages of both lakes at elevations above the gravel terraces.
They are composed of suoh crystalline intrusives as granite, grandorite and diorite. Triassic formations of limestone, sandstone and volcanics form part of the drainage on the west and north-east of Kitsumgallum
lake. (Kindle 1937).
According to JfeConnel (1912) the district having been depressed by a great weight of ice during the Glacial period, was later inundated by long arms of the sea whioh extended up the Skeena valley, through the coast range and into the interior region.
The pertinent characteristics of the drainage systems of these two
lakes are, l) the crystalline nature of -the rocks throughout the higher
elevations, 2) the gravel terraces and glacial sedimentation of the valley floor, and 3) that the region was inundated by the sea during the wane of the Glacial period.
Babine and Morrison Lakes.
These lakes lie amidst a wide expanse of rolling hills which extend from the Babine Mountains, which lie 20 miles to the west and parallel to the lakes, eastward to the western foothills of the Rocky Mountains*
Tertiary formations consisting of volcanio sedements from the Oligocene
or later comprise the southern part of the drainage of Babine lake along its western shores* To the north and on the same side of the lake occur old formations consisting of volcanio sediments from the Jurassic. The eastern drainage is mostly a heavily drift-covered area, where exposures of Palaeozoio intrusives border the lake to the south, and cross the lake to intrude upon the Oligocene volcanios. Surveys have not been extended to inolude Morrisonllake.
Morioe Lake*
Most of this lake is steeply walled in by precipitous slopes whioh consist of Jurassic crystalline rooks. Coast range intrusives, also crystalline in nature, of the Jurassic and/or Cretaceous cut across the southern third of the lake. These conditions are similar to those of the Lakelse and Kitsumgallum drainages, but unlike them, no extensive gravel beds occur in the Morice drainage. The effects of glacial action are everywhere evident and several alpine glaciers are still active on the higher slopes. Most of the streams entering the lake are opaque with glacial silt.
Bear, Suetut and Johanson Lakes.
Slopes of the Tsaytut spur border the western shores of Bear lake, and are comprised of part of the Takla group of Jurassic formations containing suoh rocks as andesite, basalt flows and agglomerates. On the west the drift area intervenes between the lake and the Connelly Range, whose formations are of the Sustut group of the Upper Cretaceous and Paleocene, consisting of conglomerate, coal and similar sediments,
Sustut and Johanson lakes lie amid the same great expanse of the heavily drift-oovered area. Mountains, mostly of Permian formations, lie in their close vicinities.
Kluantantan Lake, at the northern limits of the Skeena, lies in sedimentary formations of the Jurassic and Cretaoeous.
The geology of the area intimate to the remaining lakes, is not known.in detail. 24
MORPHOMETRICAL AND PfiYSIGO-CHEMICAL CHARACTERISTICS.
Introduction
The morphometric and physico-chemioal characteristics of the Skeena lakes can be given only brief and generalized treatment except in the oases of Lakelse, Babine and Morrison lakes* In Table 2ZT some of the more important qualities of 20 Skeena lakes have been listed*
The morphometry of the basin of a lake contributes in a very definite manner to its trophio conditions. Thienemann (1927, 1928) was one of the earlier limnologists to stress this importance of a lake's physical dimensions. Thienemann (loo sit), S trjom (1928) and Rawson
(1930, 1939) have particularly emphasized the relation of water volume and extent of surface and bottom as a factor governing the trophic nature of a lake. This relation may be expressed directly as the mean depth of a lake, which thus becomes a significant index. Seoondary factors suoh as the temperature of the water, its oxygen content, the production of nitrogenous materials and so forth, modify the general condition, and these themselves may be influenced direotly or indirectly by the geological and geographical oharaoter of the drainage.
The requirements of the present problem are to know some of these characteristics of the lakes as they directly affect the whitefish in its habitat, or as they limit the abundance of its food.
Materials and Methods.
Thirteen of the Skeena lakes have been sounded, but with varying degrees of thoroughness, wherever possible depth contours have been determined. 1
2J
TABLE JL
SOME MORPHOLOGICAL AND PHYSICO-CHEMICAL CHARACTERISTICS OF 20 SKEENA LAKES
AREA AREA MAX. LENGTH MAX. WIDTH MAX. Dl VOLUME- SHORELINE ELEVATION SURFACE BOTTOM MEAN MIN. Sq. miles Hectares Km. Km. M. M. Cu.M x 106 DEV'P'T FEET PEAK PEAK SUMMER SUMMER TEMP.°C TEMP.°C TRANS• BOTTOM PARENCY LAKELSE M. 0? % SAT. 5.47 1417 8.69 2.41 29.87 7.32 108.0 1.83 220 20.2 13.8 3.05 45 JOHNSTON 0.87 225 3.22 .97 , - ALASTAIR 2.3 596 8.37 .80 71.93 22.56 136.9 2.21 500 17.1 4.4 7.92 _ KITSUMGALLUM 6.8 1761 10.94 2.57 132.58 70.86 1247.8 2.03 468 18.0 4.0 .46 80 KITWANGA 2.8 725 6.92 1.61 13.41 7.32 52.0 2.33 600 19.1 7.0 5.79 - SWAN 10.8 2797 11.26 «•» 3.22 64.00 22.85 636.1 3.47 1500 4.3 - 80 STEPHENS 3.1 803 5.63 1.61 25.91 10.36 85.6 2.10 1500 20.3 6.0 - 72 MORICE 40.0 10360 41.67 4.50 236.21 99.67 10327.5 3.18 2614 - 4.0 3.04 - BABINE 171.8 44496 148.83 9.33 207.26 49.07 26551.5 6.59 2332 18.3 7.5 5.8 52 NILKITKWA 2.0 518 10.46 .80 18.90 5.79 29.8 2.79 2310 18.4 8.6 4.87 63 MORRISON 5.6 1450 15.29 1.77 60.96 20.73 305.8 2.60 2400 18.4 5.4 3.35 62 MOTASE - - 5.63 1.61 32.00 — - 3350 8.75 6.3 .16 - BEAR 7.2 1865 19.95 4.83 73.15 12.80 240.0 3.2 2640 19.25 6.0 4.42 - AZUKLOTZ - - 2.82 1.21 10.67 - - 2648 18.75 16.2 4.42 - SUSTUT 1.3 337 5.63 .80 18.59 6.40 21.4 2.06 4250 - - . 9.14 - ASITKA - - 1.21 .80 7.93 - - 4250 13.5 11.7 6.49 - JOHANSON 0.6 155 4.42 .80 49.38 14.63 22.9 2.90 4730 11.5 5.3 9.14 - DAMSHILGWIT - - .40 12.19 11.8 8.9 3.66 - SLAMGEESH - - .40 .40 7.93 — — 11.5 11.4 3.66 - KLUAYAZ - - 3.22 1.61 19.51 3800 11.25 7.8 .16 -
i
! V 22
Water temperatures were recorded by means of a Negretti-Zambra reversing thermometer, and in Babine lake, and more extensively in Lakelse, a bathythermograph was used on occasions.
The oxygen contents of water were determined by the Winkler method*
The pH determinations were made with a Taylor pH slide comparator.
Much of the data whioh has been used in this section have been taken from a manusoript prepared by Mr. J. R. Brett of the staff of the Pacific
Biological Station as an appendix to the report submitted by Dr. A. L.
Pritchard to the Fisheries Research Board of Canada on the results of the Skeena salmon investigations.
Lakelse lake.
Morphometry. The shape of the lake and the distribution of its bottom oontours are illustrated in Fig.o? . The lake has an area of
5.47 square miles, is approximately 5.4 miles long and varies between
0.7 to 1.5 miles in width. Its shore development of 1.83 is not great.
It is relatively shallow, and its 0 - 5 m. and 5 - 10 m. zones contain
approximately 43 and 28 per cent respectively of the total area. Its mean depth is 7.8 m. This "V" configuration of the lake bottom, and its
small mean depth are indicative of a potential eutrophic condition.
Additional characteristics of the lake are listed in Table 31.
The lake is further characterized by extensive reed beds which
extend out to the limit of the 5 m. contour line, and by the absence of
rocky shores. Kooted aquatic vegetation is particularly extensive in
the southern third of the lake.
The main stream entering the lake is Williams ereek at the northern
N 3. Map of Lakelse lake showing bottom contour lines and
dredging lines. 2*
end; smaller streams are Granite and Soully creeks on the east side, and
Clearwater and Andalas at the southern end of the lake* There are several other minor streams. Lakelse river is the only outlet from the lake*
With the exception of Blackwater creek, the different streams bring cold mountain run-off, or spring-fed water into the lake. Three of them oarry glacial silt.
Temperature. In 1944 temperatures of Lakelse lake were recorded only during the summer. Sinoe April 1946 temperatures have been recorded through each month of the year - generally at the first and middle of each month. Recordings were made at Station 1, which was within the small zone of greatest depth.
The lake is ioe covered for 5 months of the year from approximately mid-November to mid-April. The ioe oover is not excessive. (A thickness of 24 inohes of hard ice and porous snow was recorded in 1948). Maximum temperature conditions are reached during August. In Fig.*f the temperature of the water at various depths is iBhown for the years 1946 to 1948.
A true thermocline occurs only occasionally in Lakelse lake because of disturbance by frequent strong winds, especially those which sweep up from the Kitamat arm. Only the small area at the deepest part of the lake (25 m.) remains out of circulation for any length of time. When thermoclines were detected, the epilimnion extended to depths of approximately 15 - 20 m.
Sinoe 1944 maximum thermal conditions have been reached at some time during the month of August, giving four-year average surface and bottom temperatures of 19.1°C and 10.9°C respectively (Table22T j.
The date of the "maximum thermal state" referred to in Tables JiT and X Fig«, 4. Water temperatures of Lakelse lake, 1946 - 1948, was determined after plotting the isobars by selecting that day on which the average temperature of all depths was greatest during the period of
recording.
TABLE ML
Surface and Bottom Temperatures at Time of Maximum Thermal State.
Station I, Lakelse Lake.
Year Date Surface Bottom
1944 Aug. 8 19.4°C 13.0°C 1945 11 8 20.2 9.2 1946 " 29 18.8 10.3 1947 " 16 17.8 11.1
Average Aug. 15 19.1°C 10.9°C (approx.)
The fall overturn is approached gradually during October and
November. By the end of November the lake is usually ice covered. Fall
and winter data for 1946 - 1948 are given in Table 157 below.
TABLE iZ"
Fall Overturn and Winter Data. Lakelse Lake.
Fall Overturn Winter Data
Date 4°C Bottom temp. Year Date commenced Temp, reached Freeze-up Minimum Break-up
1946- 7 Oct. 31 7.0°C Nov. 8 Nov. 24 3.7°C April 15
1947- 8 Oot. 15 11.0 Dec. 8 Deo. 20 3.2 April 23 Dissolved Oxygen . The lowest concentration of dissolved oxygen
recorded in Lakelse lake was 45 per cent saturation (5.2 p.p.m.) at a o
depth of 25 m. and temperature of 9.7 C, on September 14th, 1945. During
the period of winter stagnation, beneath the ice cover, the oxygen content may have been lower in the hypolimnion, but no such condition has been
observed. A sample of water under the ice, taken from a depth of 25 m.,
and temperature of 3.8°C was 78 per cent saturated (10.5 p.p.m.), on
April 6th, 1946.
The maintenance of a relatively high oxygen content of water at all
depths throughout the year in Lakelse lake is attributed to its shallow•
ness, to the constant wind-produoed turbulence of its waters during spring,
summer and autumn, and to the replenishment and circulation of oxygen by
tributary streams.
Hydrogen Ion Concentration. The field methods and apparatus employed
occasion inaccuracies, yet there is little doubt that no conditions of
extreme acidity or alkalinity are present during any season in Lakelse
lake.
Average summer readings were as follows:
Bromthymol Blue Slide (pH 6.0 - 7.6) - Av. Surface pH - 7.1 Av. Bottom pH - 6.6 Difference - 0.6
Apparently, then, no excess of CO2 accumulates, and the circulation
provided by the several inflowing streams and the run off of Lakelse
river is sufficient to disperse the products of bottom decomposition.
The average pH of the inflowing streams was approximately neutral (7.0).
Turbidity. A standard (all white) Secchi disk was employed in the 2$
usual manneruxf averaging the depth of its disappearance and reappearance.
Weather conditions at the time of observation were noted.
The average "transparency" as recorded during 1945-48 was approxi• mately 3 m. High and low extremes were recorded at 5.3 m. (1947) and
1.2 m. (1946, 1947).
During eaoh year of observation in Lakelse, peaks of transparency were noted in July and September, and of turbidity in May and mid-October.
The latter two periods coincided with flood conditions.
Babine Lake.
For purposes of defining the range of the work of field parties this lake has been divided into three divisions, and field parties have operated in each during the summers of 1946 and 1947. Division III included the north arm of the lake and Nilkitkwa lake; Division II, half the length of the lake south from a line across the lake from
Wright Bay; and Division I, the centre of the lake from Old Fort to
Wright Bay (see Fig.d ), The field parties of Division I also investi• gated Morrison lake.
Morphometry. Details of the morphometry of the lake are given in Tabled , and the map of Fig./~ illustrates its shape and bottom contours. Its great length of 92.5 miles and narrow average width of a little over a mile give this lake the high shore development of 6.59.
The main body of water of the lake is deep, varying from 80 to 140 m.
The greatest depths are found in the southern centre of the lake, and here the maximum depth of 207 m. was recorded. The two northern arms are relatively shallow, with only a portion of the western arm exceeding
30 m. 2
'Fig. 5. Map of Babine lake showing bottom contour lines BABINE RIVE-
BABINE LAKE
AND ADJACENT WATERS
DEPTH CONTOURS AT TWENTY METRE INTERVALS
WITH BROKEN LINE AT TEN METRES
5 MILES
ROADS
TRAILS Jo
With the exception of the two northern arms, most of the lake shore• line drops off fairly sharply into deep water. A description of the types of the narrow shoreline of Division II applies fairly well to the remainder of the lake excluding the two northern arms:- gently sloping sand and mud- shore, 2G per cent; gently sloping fine gravel, 19 per cent; gently sloping broken rock and boulder, 4 per cent; a steeper incline of fine gravel soon replaced with coarse gravel, 42 per cent; broken rocks on a precipitous slope, 8 per cent; and bluffs with no distinot shoreline, 4 per cent. The two shallow arms carry less rock, have shores of gradual decline and contain fairly extensive reed beds*
Contour lines less than that of 20 m. have not been determined. The area of the 0-20 m. zone is 44.5 sq. miles or 25.9 per cent of the total area. The mean depth of the lake including the northern arms is approxi• mately 49 m. The bottom configuration of Babine lake is thus essentially a deep "V shape in its greater part.
Temperature. Summer temperature recordings were made fortnightly at stations in each division. Winter records were obtained at Division III
(northern arm) in 1946 and 1947.
In Fig.the temperature of different depths is illustrated for
Division II and III in 1946.
The lake is oovered for about six months of the year with a deep layer of ice and snow. In 1946 the ice began to break up in Division II towards the end of April, and in Division III during the second week of
May. The lake was again frozen in that year by about the 20th November.
More stable conditions and the establishment of true but shallow thermoclines ocour more frequently in Division III, than throughout the
3Z
deep and open waters of Divisions I and II. Wind action down the long sweep
of the lake maintains considerable circulation to depths of 30 m. throughout most of the lake during summer. Below this depth in Divisions I and II, and
below a depth of 15 m. in DivisionsIII conditions remain,,mor©, stable, and
bottom temperatures have not exceeded 5.0°C for Divisions I and II, and
7.6°C for Division III at the time of maximum thermal state (Table S ).
TABLE % •.-
Surface and Bottom Temperatures at the Time of Maximum Thermal State.
Year Date Surface°C B©ttom°C Depth Taken m.
Division II 1946 July 23 18.3 ,; 4.1 73 1947 " 28 14.1 4.0 73
Division III 1946 Aug. 9 15.2 6.0 56 1947 " 22 17.5 7.5 36
At times heavy winds prolong the period of open water and on
occasions have temporarily broken up the ice in certain parts of the lake
during the winter.
Dissolved Oxygen. In each division the oxygen content at all depths
has been high throughout most of the year, and concentrations have rarely
gone below 80 per cent. Winter data have been inadequate, but it is believed
from the available evidence that no scarcity occurs in any major part of .
&he lake during this period. Minimum oxygen concentrations determined in
1946 and 1947 are given in Table JL
Hydrogen Ion Concentration. Only small variations above or below
neutrality have been recorded throughout the lake* Records of extreme
deep and surface conditions are given in Table JUL o*3
TABLE
Minimum Oxygen. Concentrations Recorded in Babine Lake. (Corrected for Altitude).
Div. I Div. II Div. Ill 1946" I3itT IW 1945 1947 Date . July 10 July 18 June 13 July 23 May 23 Depth - «..' 60 134 7 3 38 39 Temp. - °C 4.25 4.1 4.0 5.2 4.2 Og Per cent Saturation 68 80.9 68 67 53
TABLE .XIL
Extreme of Recorded pH Conditions in Babine Lake.
Division I Division II Division III
Year 1946 1946 1947 pH at Surfaoe 7.25 7.20 7.6 pH at Depth 6.8 (60 m.) 7.30 (67 m.) 7.3 (30 m.)
Transparency. The average Secchi disc recording throughout the lake was 5.2 m. Recordings varied from an extreme low of 1.8 m. to a high of
7.6 m. Lowest transparencies invariably occurred in Division III and were coincident with spring flood conditions. Division averages were 5.3 m.
Division I; 5.2 m. Division II; and 6.2 m. Division III
Morrison Lake.
Morphometry. A novel feature of Morrison lake is that it lies between a aystem of two small lakes and their streams which enter it from the north, and Babine lake to the south, into which it flows by way of the
Morrison river. In this it is unlike the rest of the lakes of the Skeena ;Fig. 7. Map of Morrison lake showing bottom contour lines. drainage. Important characteristics of the lake appear in Table _ZZT
A map of the lake, with bottom contours is given in Pig. 7~
Morrison lake has a shore development of 2.60, which is relatively large for its area of 5.6 sq. miles. It is 9.5 miles long and has an average width of less than 1 mile. A narrowing of its width divides the lake into two distinot zones - a relatively deep northern two-thirds, and a shallow southern third. A shallow bottom, bearing very large rocks which often appear above the surface, and ooves which oarry extensive reed beds are -typical of muoh of the southern part of the lake. These conditions are emphasized in the vicinity of the source of the Morrison river.
The lakes to the north are Haul and Salmon, and their outflowing
streams bear the same names. These are the only important tributaries into Morrison lake.
The 0-5 and 5 - 10 m. zones oooupy 19.4 and 16.3 per cent res• pectively of the lake's total area. The values for the northern division of the lake alone would be considerably less than this. Maximum and mean depths of the lake have been determined as 61 and 21 m.
Temperature. Winds are fairly frequent on Morrison lake, but
surrounding hills and mountains generally prevent any great disturbance of the deep waters of the northern centre. Shallow thermoclines exist during muoh of the summer between the levels of 5 and 10 m. Table 10- demonstrates the thermal conditions of the water at Stations I, II and
III in 1947 on the dates indicated. Thermoclines in the 5 - 10 m. strata are evident on each occasion with the exception of the 26th September, at Station III.
There are no records of the duration of the ice cover of Morrison TABLE "M>
WATER TEMPERATURES AT DIFFERENT DEPTHS, AT STATIONS I, II, and III,
MORRISON LAKE, 1947. (Degrees Centigrade)
STN. Ill STN. II STN. I
July 2 Aug. 4 Sept. 26. July 31. July 2. July 31.
0 m. 15.4 16.75 14.4 18.0 17.2 18.0
5 13.4 16.5 12.0 15.0 13.4 17.7
10 7.4 9.95 11.3 8.9 7.3 10.0
20 5.5 5.95 6.5 6.1 6.2 7.2
60 4.9 5.3 5.4 _ _ lake. Probably It lasts longer than that of Babine lake, since the lake is smaller and more protected.
Zn 1947 at Station III, in the deep centre of the lake, peak thermal conditions redorded gave a bottom temperature of 5.4°C, and a surfaoe temperature of 16.75°C. The shallower parts of the lakes were warmer than this.
Dissolved Oxygen. The oxygen content has been found high at all depths. In 1947, the bottom (60 m.) oxygen content in July, August and
September was 70, 72 and 80 per cent saturation respectively. The lowest summer record was a bottom saturation of 60 per cent.
Hydrogen Ion Concentration. All recordings indicated a small pH range of 6.8 to 7.2.
Transparency. Secchi disc readings at Station III in 1947 were
2.8 m. on July 2nd and 4.0 m. on August 4th. The condition is similar, then, to that in Lakelse and Babine lakes.
Other lakes.
Certain characteristics of the remaining 17 lakes investigated are summarized in Table £ •
Morphometry. Since 1945 the Skeena lakes have been classified under three categories: (l) "deep, cold bodies of water almost opaque and grey from glacial silt" - Morice, Kitsumgallum, Johnston, Motase,
Kluayaz. (2) "rather shallow bodies of water, clear, of moderate tempera• ture and abundant in plant life - Lakelse, Kitwanga, Suetut, Asitka,
Morrison, Stephens, Nilkitkwa, Azuklotz, Samshilgwit, Slamgeesh, Kluantantan.
(3) Intermediate between (l) and (2). Johanson, Swan, Alastair, Babine, Bear. Temperature. In only one lake, Azuklotz (maximum depth 10 m.), has it been recorded that the bottom temperature exceeds the bottom peak of Lakelse lake. A single observation of the surface temperature of
Motase lake in summer gave a low of 6.75°C.
Oxygen Content. Oxygen oontent determinations were made in only four of these lakes. No serious deficiency was recorded except in
Kitwanga lake. In this lake a definite summer depletion at bottom was noted. Kitwanga lake is one of the highest plankton producers of the
Skeena lakes.
Transparency. Glacial silt contributes to the extreme opacity of the five lakes of oategory (l). The remaining lakes are intermediate or clear as indicated.
Summary and Significance.
Rawson (1930, 1934, 1939, 1942) in his investigations of a number of diversified and widely separated lakes has added considerably to the characteristics which may be employed in the classification of lakes as oligotrophic, eutrophic or dystrophic. His descriptions mainly have been followed in this attempt to plaoe the Skeena lakes into these categories, and therefore a summary of his discussions will be given. Reference has also been made to the early work on lake types by Thienemann (1927, 1928) and to the proposals of Str/c»m (1931, 1938), Eggleton (1939) and Welsh
(1935). Characteristics of an ollgotrophio lake include the following; a poor food supply (plankton and bottom fauna), generally having a U- shaped bottom, deep basin, large and exposed surface area, no marked thermal stratification, no oxygen depletion nor high acidity in deeper waters, small amounts of nitrogen, phosphorous and calcium. The character• istics of eutrophic lakes, approximately the opposite of the former, are; Jf.
V-shaped, generally protected and able to support much aquatic vegetation, marked thermal stratification, hypolimnial oxygen depletion and high acidity during stagnation, high temperatures and relatively large amounts of phosphorous, nitrogen and calcium. Other conditions such as the presence of certain characteristic organisms are also referred to. Thus the larval chironomid C. plumosns is typioal of profundal waters of eutrophio lakes where the oxygen oontent is very low, while the Tanytarsus larva in pro• fundal waters, needing a rioh supply of oxygen, designates oligotrophio conditions.
On the basis of these characteristics it is possible at least to indicate the tendenoy of the various Skeena lakes towards either eutrophy or oligotrophy, although because of such brief investigations definite categories for most lakes can be assigned only tentatively. In Table some of^the characteristics of oligotrophia and eutrophic lake types have been listed for ten lakes, and it is indicated how eaoh lake ascribes to the various conditions.
These ten lakes are first chosen since the plankton hauls made in them have been examined in a quantitative manner by Mr. V. H. McMahon of the
Pacific Biologioal Station (unpublished mss. ). Table 7£ can be used here to designate certain of the characteristics necessary to assign a lake type for the remaining Skeena lakes.
In continuing the study of lake types emphasis will be placed on the three lakes, Lakelse, Babine and Morrison, which have received most attention during the investigations, and whose data form the foundation of this study of the whitefish.
Several lakes, it will be noticed, do not ascribe universally to TABLE JX
CONDITIONS FOR EUTROPHY AND OLIGOTROPHY IN 10 SKEENA LAKES.
THERMALLY DEPTH AREA BOTTOM STRATIFIED TEMPERATURE LAKE SHALLOW DEEP SMALL LARGE V TJ YES NO HIGHER LOWER
LAKELSE
BABINE V
MORRISON X V x X
KITWANGA 6 X V X
KITSUMGALLUM x X U X
ALA STAIR X X V X X
SWAN X X V X X
STEPHENS X V X X
MORICE U
BEAR X V
NOTE: Conditions for EUTROPHY Seldom are to the left of ea^. h In part of lakes only. column; and to the right for OLIGOTROPHY TABLE IT- (Cont'd)
PLANKTON BOTTOM FAUNA HEAVILY BOTTOM 02 SUMMER- pH ABUNDANCE' ABUNDANCE LAKE LOW HIGH LOW NOT LOW HIGH LOW HIGH LOW SILTED TYPE
LAKELSE X X MOD. MOD. # EBfTROPH-IC BABINE X X MOD. X OLIGOTROPHY MORRISON X X MOD. X # OLIGOTROPHY KITWANGA x X X. EUTROPHIC KIT SUMGALLUM X X X X OLIGOTROPHY ALASTAIR - MOD. OLIGOTROPHY SWAN X X MOD. OLIGOTROPHY STEPHENS X X X EUTROPHIC MORICE X X X X OLIGOTROPHY BEAR X X MOD. OLIGOTROPHY
# Conditionally, as described in text
NOTE: Conditions for EUTROPHY are to the left of each column; and to the right for OLIGOTROPHY either condition of eutrophy or oligotrophy. Lakelse lake indicates a fundamental condition of eutrophy, but serious oxygen depletion or aoidity has not been observed. It is thermally stratified, having a distinct thermocline only occasionally. These departures from the typically eutrophic condition can be explained by the frequency of the wind-produced turbulence it experiences, and the constant circulation effected by its
several affluent and its effluent streams. Reference has been made to these conditions earlier in this section. Mr. McMahon has estimated the production of plankton in Lakelse lake as 0.00197 cc. per foot of "functional1' depth. This quantity, is apparently of only moderate dimensions. . (The
"functional" depth is that depth of water iii whioh 80% of the plankton by volume, is found). The bottom fauna of Lakelse, determined by the writer as 628 organisms per square metre, (weighted for area of different depth
zones), is also only of moderate abundance. Lakelse lake, then, essentially eutrophic in type, by virtue of the primary factors of its morphology
(such as its area and depth), exhibits in its secondary factors, (such as its thermal and chemical stratification), conditions which indicate oli• gotrophy. Several specieB of chironomid larvae are found in Lakelse,
including at least three genera. Among those Chironomus is apparently the most common. Tanytarsus was found in shallow waters, but sufficient
identification has not been done to make a preoise statement on the dis• tribution of different chironomids. In the deepest part of the lake one
dredge haul contained Chironomus and two other species of the Chironomidae.
It would be better, perhaps, to suggest the lake type by the complete absence of either C. plumosus or Tanytarsus from distinct profundal zones, provided it is known that they do inhabit the general region around the
lake. Babine lake is decidedly oligotrophic. With the exception of its two northern arms and some of the bays (Wright bay, for example), none of the listed conditions for eutrophy hold. Though bottom sampling has been meagre, they indicated low to moderate abundance of organisms.
Plankton production (by volume) was not very different from Lakelse. In contrast to certain other oligotrophio Skeena lakes, however, its waters are of fairly high transparency, and ligh penetration, therefore, is relatively good. The common chironomids found in bottom samples were of the genus Chironomus. The same form persisted from shallow water to depths of 50 metres. No Chironomidae were taken in the few dredge hauls made at 100 metres.
Most of the conditions of Morrison lake are those that obtain for oligotrophy. Though its area is almost identical with that of Lakelse, much of the lake is considerably deeper. It differs from the remaining
Skeena lakes by having at a short distance from its northern limits, two
small, tributary lakes (as desoribed earlier in this section). How these influence the overall conditions of Morrison lake has not been determined.
Perhaps they have no greater relative effeot than the tributary streams of other lakes. The production of plankton in Morrison is somewhat greater than in Lakelse. Its bottom fauna is apparently very sparse.
Chironomidae identified belonged to the genus Chironomus, but only a few dredgings were made in this lake.
Kitwanga and Stephens are decidedly eutrophic on the basis of all the conditions listed. Their plankton production is relatively very high.
Kitsumgallum lake and Morice lake are definitely oligotrophic.
They produce extremely low quantities of plankton. Their oligotrophic conditions are particularly influenced, beyond their general morphometrical and physico-ohemioal characteristics, by the severe silting of their waterB.
As Table Ti- indicates, Alastair, Swan and Bear lakes tend rather to oligotrophy despite oertain contrary conditions.
The remaining Skeena lakes are tentatively classed as fellows:
Oligotrophicj Johnston, Motase, Kluayaz, Sustut, Johanson: Eutrophio;
Nilkitkwa, Azuklotz.
Several of the northern lakes are apparently in a dystrophic phase, a condition in whioh the accumulation of humic materials and the encroach• ment of marginal plants and their incomplete decay, culminates in the formation of peat bogs and dry flats. Such lakes are Slamgeesh, Damshilgwit and Asitka.
Though tentatively olassed as eutrophio, Nilkitkwa lake (since it shows no serious oxygen depletion nor high acidity) digresses from such a condition, perhaps because of the circulation provided by the Babine river, which leads into the lake at its southern limit, and leaves it at its northern end.
Sustut lake, though relatively small and shallow, is, no doubt, particularly influenced towards oligotrophy by its high altitude (4250 ft.).
Johanson and Kluayaz lakes, already listed as oligotrophic, are at similar elevations. THE BATHYMETBJC DISTRIBUTION OF EASTERN AMD ROCKY MOUNTAIN ,WHITEFISH.
Introduction,
This attempt to determine the depth distribution of the two species of whitefish has been made by analysing the oatch records of standard sets of gill-nets in Lakelse, Babine and Morrison lakes.
Some of the limitations of gill-net sampling should be mentioned since they affect the interpretation of the analyses.
Every major type of environment should be sampled adequately. This was done in a small lake such as Lakelse, but oould not be achieved in
Babine lake. Morrison lake is relatively small, but was visited only periodically eaoh summer, and fewer positions, therefore, were netted.
According to Withler (1948) small differences in the size of meshes, and even in the size and kind of twine used can cause gill-net selectivity.
A gang of nets therefore, usually consists of one kind of twine only, and is made up of several nets so that as wide a range of mesh sizes as is convenient is included.
To allow each net of different size to sample the different depths equally, the position of nets in a gang is continually varied. This method requires much time and personnel and in the Skeena investigations variation was partly aohieved by alternately reversing perpendioular set8 rather than changing the position of nets in §. gang.
A typical gang of nets used in the Skeena investigations oonsisted of 1^-, 2^-, 3^, 4§- and 5^ inoh stretched meshes in that order. With one exception all nets were 150 feet long and 6 feet deep. Several standard positions were chosen in each of the three lakes*
In Lakelse lake 14 positions were fished; 10 in each division of Babine lake and 3 in Morrison lake* As conditions permitted, sets were rotated from one position to another, and usually gangs were set simultaneously in more than one position* The duration of a set varied because of weather conditions and other work, but all sets remained throughout a night and never more than one night*
Gangs were set either parallel to the shore (i.e. throughout a uniform depth), or at right angles to the shore. The latter type of set was the more common, and in suoh cases gangs were reversed on e aoh alternate set.
Treatment of the Netting Data*
The analyses of Table for Rocky Mountain whitefish (Lakelse lake) and TableJLL for Eastern whitefish (Morrison lake) have been com• puted, so that reference to the catches of small meshes will indioate small fish, while reference to the catches of larger meshes will indicate larger fish. These analyses are appropriate for the three lakes (Lakelse,
Babine and Morrison). For convenience meshes which varied by only a small fraction of an inch have been grouped to the nearest ^ inch.
As Tables-X,> and_XZ indicate, the average size of the fish inoreases as the sige of the mesh increases, and there is considerable overlapping between the successive meshes in the sizes of the fish they gill.
Reference to small or larger meshes will thus serve to indioate small or larger fish.
In the tables and figures which summarize the catch per depth relationship of either species in the three lakes, the meshes have been TABLE X-f
AVERAGE SIZES OP ROCKY MOUNTAIN RHITEFISH CAUGHT IN VARIOUS MESHES
LAKELSE LAKE. .' 1945, 1946 and 1947 DATA COMBINED
MESH SIZES - Inches (Combined linen and cotton).
1* If 2 2* 3 3^
No. of Fish 29 5 69 26 33 5 2
Av. size 8.25 10.0 9.75 11 .10 12.31 13.0 13.13
Range 6.75- 6.75- 7.5- 9 .25- 10.5- 10.5- 11.5- 10.25 13.5 11.5 14 .5 13.54. 14.5 14.75 S. D. 1.06 3.19 0.89 1 .04 .74
A few set of cotton meshes of sizes 2.7 inches and 2.1 inches have been included with the 2§ and the 2 inch meshes respectively. TABLE ~J&
AVERAGE SIZES OP EASTERN 1HITEFISH CAUGHT IN VARIOUS MESHES. MORRISON
LAKE, DATE OF 1946 and 1947 COMBINED.
MESH SIZES
LINEN
1* 2 2* 3 3* 4 5
No. of fish 17 28 6 10 24 4 1
AT. size-in. 6.85 9.47 11.83 13.13 13.20 13.56 18.0
Range 6.00 - 8.00 - 11.5 - 11.75 - 12.5 - 11,75 - - 8.25 14.0 12.75 14.25 14.5 14.25
S.D. .84 2.04 .54 .79 .53 1.21
COTTON
2 3 3* 4 4*
No. of fish 16 20 22 45 32 5 2 2
AT. size-in. 7.56 12.64 12.10 13.32 13.46 12.90 14.13 15.25
Range 5.75 - 11.0 - 8.75 - 11.25 - 12.5 - 11.0 - 13.25- 13.25 8.25 14.0 14.25 14.5 14.75 13.75 15.0 17.25
S.D. 1.53 1.35 2.02 .77 .62 1.10 — - given a number corresponding to the nearest inoh rather than their actual
size. This has been necessary since many meshes varied by only small fractions of an inch. These data combine the catches of both linen and
cotton gangs, since the error involved in such a procedure is offset by the value of larger samples.
The theory employed here to investigate the depth distribution of fish, is, if a small mesh makes its best catches in shallow water, then
small fish are concentrating in the shallower water. Conversely if large meshes obtain their highest catches in deep water, the large fish must be more abundant at such depths. These methods and this theory have also been used by Hile and Juday (1941) in their analyses of the bathymetrio distribution of rock bass, perch, bluegill and other fish in oertain
Wisconsin lakes. The writer has attempted several methods to interpret
the catoh distribution, but has found the one used here to be the most useful and reliable for the data at hand.
The catch per set (or catch per net-night, since all nets remained
set throughout one night) has been made the unit of effort and relative abundance. The oatch per net-nfLght will hereinafter be referred to as the c.n.n.
Distribution of Rocky Mountain WMtefish in Lakelse Lake.
Totals of 80, 63 and 45 fish were netted by standard methods in
this lake in 1945, 1946 and 1947 respectively.
Table*/', and Fig. f summarize the catches of different meshes in
different depth zones. Since gangs were selcom reversed in 1945, only the 1946 and 1947 data have been made use of for this analysis. TABLE */•
CATCH PER NET-NIGHT OF ROCKY MOUNTAIN WHITEFISH IN NETS SET AT DIFFERENT
DEPTHS IN LAKELSE LAKE. 1946 and 1947 DATA COMBINED.
MESHES.
Depths -m. #1 #2 #3 #4 #5 TOTALS CNN Sets C.NN Sets C.NN Sets CNN Sets C.NN Sets CNN Sets
0-3 .524 42 1.651 43 .233 30 o "; '39 0 c.O 35:: :s .529 189
3-6 .250 4 .364 11 0 23 0 15 0 12 .077 65
6-9 .050 20 .083 12 0 15 0 13 0 20 .025 80
9-12 0 2 0 2 - - 0 1 0 1 0 6
12 - 15 0 4 0 4 0 4 0 4 0 4 0 20
15 - 18 ------
18 - 24 0 2 0 2 0 2 0 2 0 2 0 10
TOTALS .324 74 1.027 74 .096 74 0 74 0 74 .289 370 of/
ME SH E S i 19 13 U I s I i lg la U Is 11 IglsUlsh lg la UIsti lg 1 a 14 1 s I i lg la U IsJ i I2 I 3 U Is
NO. OF SETS
4gl»3b 1-6 x o UJ z OC ill a. • 8 o I > - 3 3 — 6 6—9 9—12 12 — 15 15 — 18 18- 24 DEPTH- METRES Fig. 8. Catch per net-night per mesh of Rooky Mountain whitefish at different depths in Lakelse lake. Data of 1946 and 1947 combined. No fish were caught in a mesh larger than the # 3 mesh. None were netted in depths greater than 10 m, although all meshes were set in such depths a total of 36 times, and each mesh the number of times indicated in the table. The greatest catches of any mesh that did catch fish were in the 0 - 3 m. zone. The smallest meshes made catches up to 9 m. The largest mesh to catch fish caught them only in the shallow zone of 0 - 3m.; these catches made up a total of 7 fish gilled by the 3 inoh and 3§ inoh meshes, and three of these were larger than any caught in the smaller meshes, their average size being 14.5 inches, fork length. The criticism can be made that certain meshes inadequately sampled some of the zones. This is true, but as Table*'/ and Fig. 9 - 12 m. zone was sampled only once by the # 4 mesh and caught no fish, but neither did it catch fish in the 6 - 9 m. zone when set 20 times, nor in the 12 - 15 m. zone when set 4 times'. In Lakelse lake, then, the results of gill-net catches indicate that the Rocky Mountain whitefish of all sizes tend to occupy the shallower waters of 0 - 10 m. and that the smaller fish frequent deeper water more often than do the larger fish. Distribution of Rooky Mountain Whitefish in Babine Lake. In all divisions' 6f Babine lake a total of 332 Rocky Mountain white- fish were netted in 1946 and 1947. Only the standard catches of Division I and Division II (excluding Wright bay) are used here. These total 269 fish. Table Jfu/ and Fig. ^.*"show the relationship between the size of fish (as inoidated by mesh size) and abundance at various depths (as indicated by the o.n.n.). #3 TABLE )Ufl. CATCH PER NET-NIGHT OF ROCKY MOUNTAIN 1HITEFISH IN NETS SET AT DIFFERENT DEPTHS IN BABINE LAKE (DIVISIONS I AND II). 1946 and 1947 DATA COMBINED. MESHES DEPTHS. M. • #1 -i #5 #4 #5 Totals CNN Sets CNN Sets CNN Sets CNN Sets CNN Sets CNN Sets 0-5 .888 63 1.911 56 .717 46 .041 49 .014 74 .691 288 5-10 .129 31 .464 28 .774 31 .030 33 0 37 .263 160 10 - 15 0 7 .419 31 .429 21 .091 33 0 11 .243 103 15 - 20 0 14 .077 13 .067 15 0 14 0 18 .041 74 20 - 25 0 5 0 8 .077 13 0 7 0 9 .048 42 25 - 30 0 6 - - - - - 0 7 0 13 TOTALS .476 126 .985 136 .540 126 .044: 136 .006 156 .396 680 MESHES ] lg laUls 11 la la U Is 1 i lg laU Isl i 1 g I a 1 41 s I i 1 a 1 aU I s 1 i I g i a 141 s NO. OF SETS. Bak*;iaal4Qt74k i friala i kak7 7 lailai Laaln Ii4lialisli4.fl fi I a lis 1719g | nlnlol7 X UJ or ui o. X o < o 0-5 5-10 10-15 15-20 20- 25 25-30 DEPTH-METRES 7Fig« 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 oombined. Only 1 fish was caught in depths greater than the 15 - 20 m. 2one, though a total of 55 sets was made in depths greater than 20 m. Meshes #1, #2 and #6 made their greatest catches in the 0 - 5 m. §one. In the case of the TT3 mesh the difference between the o.n.n. in the first and second zones was slight. The o.n.n. of #4 mesh was greatest in the 10 - 16 m. zone, but since it represented only 3 fish, it is possible that fish of this size were evenly distributed up to depths of 15 m. Mesh #6 was set 166 times; it oaught only 1 fish (14.75 inches fork length), and that in the 0 - 6 m. zone. The largest fish caught was a female of 17.25 inohes fork length whichwas netted in 4 inch mesh at a depth of approxi• mately 7 m. As in the case of the lakelse fish, the Rocky Mountain whitefish of Babine lake inhabit the shallower waters during the summer, up to depths of 10 and 16 m. The few taken at greater depths are usually the medium sized fish. Distribution of Eastern Whitefish in Babine Lake. The total oatch of Eastern whitefish in Divisions I and II (excluding Wright bay) for 1946 and 1947 was 121 fish. The oatoh/depth relationship is shown in Table XN. and Fig. The #2, #3, and #4 meshes each made their best oatches in the 10 - 15 zone* The smallest sized mesh (#1) netted fish only in the shallowest waters of 0 - 5 m. It was set at various greater depths a total of 63 times The largest mesh (ite) made fairly even oatches throughout the range of depths sampled, except in depths greater than 25 m., where none was caught* Mesh # 2 made a greater catch in the 0 - 5 m. zone than in the 5 - 10 m. zone, although its greatest oatches were at depths of 10 - 15 m. A probable explanation for this effect is that if the smallest fish TABLE XN. CATCH PER NET-NIGHT OP EASTERN WHITEFISH IN NETS SET AT DIFFERENT DEPTHS IN BABINE LAKE. 1946 and 1947 DATA COMBINED. MESHES. Depths - m. # 1 #2 #3 #4 #5 TOTALS C.NN Sets C.NN Sets C.NN Sets C.NN Sets C.NN Sets C.NN Sets 0 - 5 .095 63 .286 56 .130 46 .286 49 .054 74 .160 28$ 5 - 10 0 31 .142 28 .194 31 .455 33 .081 37 .175 160- 10 - 15 0 7 .323 31 .238 21 .697 33 .091 11 .378 103 15 - 20 0 14 .231 13 .067 15 .144 14 0 18 .081 74 20 - 25 0 5 0 8 .077 13 0 7 .111 9 .048 42 25 - 30 0 6 _ 0 7 0 13 TOTALS .048 126 .243 136 .151 126 .397 136 .058 156 .178 680 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 combined. ft (i.e. of #1 mesh) tend to remain in waters not deeper than 5 m. (whioh the evidence does indicate), and if the sizes overlap in successive meshes, (which has already been demonstrated), then mesh #2 should have a relatively greater catch in the 0 - 5 m. zone. In other words fish of this size probably gradually inorease in numbers from shallow waters to a maximum in the 10 - 15 m. zone. The Eastern whitefish in Babine lake concentrate in depths up to 25 m. They were most abundant in depths between 10 and 15 m. The smallest fish were netted only in the shallowest water. The evidence does not indioate that there were relatively more larger than smaller fish in shallow water. Catch of Both Species in Different Positions in Babine Lake. Netting positions in Babine lake offer a sufficiently wide range of depth that the oatoh data may be analysed in a different manner to explore the catch/depth relationships. In the following analyses each species is treated separately. All perpendicular sets made in Division II (excluding Wright bay) in 1946 and 1947 were used. The o.n.n. of eaoh of the 10 positions is reoorded against the average depth of the position. The average depth of the position was determined by averaging the five net depths. In each case correlation coefficients were deter• mined to measure the relationship between the c.n.n. and the mean depth of the positions. The analyses for Rocky Mountain and ^astern whitefish are presented in Tables xv. and xv/. respectively. In the case of the Rocky Mountain whitefish there is a highly significant inverse relationship between the catoh per unit of effort (i.e. c.n.n.) and depth. The probability that this condition arose by chance alone is only 1 in a 100 (see Table xvt ). This indicates TABLE XV.< CATCH/DEPTH RELATIONSHIP OF ROCKY MOUNTAIN WHITEFISH IN BABINE LAKE. CATCH PER NET-NIGHT AT DIFFERENT POSITIONS IN DIVISION II. 1946 AND 1947 DATA COMBINED POSITIONS 1 2 3 4 5 6 7 8 9 10 1946 1.50 6.75 0.25 3.50 1.00 0.75 4.00 4.60 1.50 2.00 1947 1.50 3.20 2.40 4.00 1.75 0.25 3.50 0.00 0.50 2.75 Combined 1.50 4.78 1.44 3.78 1.38 1.38 0.50 3.71 2.56 2.17 AT. Depth-ft. 40' 13' 38' 6' 32' 26' 10' 11' 52» 33' AT. Depth-m. 12.2 4.0 11.6 1.8 9.8 7.9 3.0 3.4 15.8 10.1 r - - o.7 7 j t - 5.37, /> (%® .01 - d.f .8 - 3.355.J NegatiTe correlation very significant. TABLE XV/. CATCH/DEPTH RELATIONSHIP OF EASTERN WHITEFISH IN BABINE LAKE. CATCH PER NET-NIGHT AT DIFFERENT POSITIONS IN DIVISION II. 1946 AND 1947 DATA COMBINED • POSITIONS 1 2 3 4 5 6 7 8 9 10 1946 1.00 2.00 0.00 0.50 1.50 .50 0.00 0.25 0.25 .50 1947 .50 .40 1.80 0.25 1.00 0.00 .40 0.00 0.00 1.00 Combined 0.67 1.11 1.00 0.38 1.25 0.25 0.22 0.13 0.13 0.83 Av. Depth-ft. 40' 13' 38' 61 32' 26' 10' 11' 52« 33' Av. Depth-m. 12.2 4.0 11.6 1.8 9.8 7.9 3.0 3.4 15.8 10.1 r - 6 0° 175, t - .503 ^ ' > ' f (\, ® 0.5, d.f .8 - .703^ Positive correlation non-significant that as long as deeper waters are sampled equally with the shallower, the catch decreases as the depth increases* -'•'he catch oan be arranged as follows for further study:- greatest catches were in Positions 2 whose mean depth is 4*0 m. A. "i """18» m >v ach e a n r* II, nIt II u t*n Z' • « « » is/2.60 o.u m* 8 M " "13.4 m. intermediate catches were in Position 10 " " " "10.1 m. each o.n.n. is <2.50 and ,> 2.00 lowest oatches were in Positions 1 " " " "12.2 m. U II II I111.1 6 m. 6 " " 11 " 9.8 m. each c.n.n. is<2.00 6 " " " 7.9 m. 9 " " "15.8 m. The results for the Eastern whitefish indicate no significant correlation between the catch and mean depth of Positions. However, were correlation indicated, it would be in a positive direction at about .50 probability level. The interpretation of these results suggests that the numbers of Eastern whitefish are greatest at some intermediate zone between shallow and deep water. The catches at different Positions are given below: greatest oatches were in Positions 5 whose mean depth is 9.8 m. 2 " " * " 4.0 m. each o.n.n. is 1.00 it it "11.6 m. or greater intermediate oatehes were in Positions > 10 " " " "10.1 m. each o.n.n. is.> .50 1 " " " "12.2 m. <1.00 lowest catches were in Positions 4 " " " " 1.8 m. 6 0 " " 7.9 m. 7 " " " » 3.0 m. each c.n.n. is < .40 8 " 3.4 m. 9 " " " "15.8 m. These results, for both species, agree with those of the more detailed method given earlier in this section. Distribution of Eastern Whitefish in Morrison Lake. The total catch of fish in Morrison lake by standard methods in 1946 and 1947 was 241 fish Table XV//. and Fig.// summarige the results in terms of c.n.n. of each mesh in different depths. *he fewer positions used (three only), and the similarities of their depths are reflected in the low numbers of sets of each mesh in certain depths. This happens because with perpendicular sets the only variation achieved was by reversing the gangs. Despite the relatively larger catches the data are less easily interpreted than those of Babine lake where many more sets were made throughout a greater variety of positions. The c.n.n. of the #3 mesh is considerably greater in the 5 - 1G m. zone from 9 sets than it is in the 10 - 15 m. zone from 12 sets. Similarly the c.n.n. of the #2 mesh is greater in the 5 - 10 m. zone from 10 sets than it is in the 10 - 15 m. zone from 9 sets. The c.n.n. of the #2 mesh in the 0 - 5 m. and 15 - 20 m. zones were also relatively high, but were made by only 1 and 2 sets respectively. Fish of sizes represented by the #2 and #3 meshes are probably more concentrated in depths of from 5 - 15 m. than in depths less or greater than this. Although some of the zones have been inadequately sampled it is probable that the smallest fish, as re• presented by #1 mesh, were most numerous in shallow waters. The $6 mesh caught only 2 fish; (these were 17.25 inches and 18.00 inches fork length, greater by 1% inohes and 2j| inches than the largest fish caught by the #4 mesh), and these were netted in the 0 - 5 m. zone. A general conclusion can be drawn that the smallest (nettable) and larger individuals tend to remain closer inshore than intermediate sized TABLE XV//.-. _ CATCH PER NET NIGHT OF EASTERN WHITEFISH IN NETS SET AT DIFFERENT DEPTHS IN MORRISON LAKE. 1946 and 1947 DATA COMBINED DEPTHS - METRES MESHES 0 -•5 5 10 10 - 15 15 • 20 TOTALS CNN Sets CNN Sets CNN Sets CNU Sets CNN Sets #1 2.80 10 0 2 0.25 4 0.67 6 1.50 22 2 2.00 1 3.90 10 1.56 9 3.50 2 2.82 22 3 0 1 9.56 9 3.92 12 - - 6.05 22 4 0 1 0.50 6 0.55 11 0.50 2 0.45 22 5 0.22 9 - - 0 7 0 6 0.09 22 TOTALS 1.45 22 4.45 29 1.58 43 0.75 16 1.10 110 Catch per net night per mesh of Eastern whitefish at different depths in Morrison lake. Data of 1946 and 1947 combined. 6* fish which inhabit deeper water up to 16 m. and occasionally beyond this. Summary and Comparisons* The following remarks refer to fish of nettable sige and their dis• tribution in the lake during the summer months. In Lakelse lake Rocky Mountain whitefish of all sizes remain in relatively shallow waters throughout a depth zone of 0 - 10 m. The greatest numbers are found in depths up to 3 m. and the largest individuals pro• bably range less often into waters outside the 0 - 3 m. zone than do those of intermediate and smaller size. The distribution of the Rocky Mountain whitefish in Babine lake is into somewhat deeper water than in Lakelse but otherwise is essentially similar. The smaller fish are most numerous in the shallowest zone of 0 - 5 m. Fish of intermediate size are probably evenly distributed up to a depth of 10 m., and are found less often at greater depths. The largest fish remain in shallow water more so than do the fish of intermediate size. The Eastern whitefish of Babine lake is most abundant in depths greater than those in whioh the Rooky Mountain whitefish are most numerous. Thus all but the smallest and largest fish occur in greatest numbers in depths of 10 - 15 m. The smallest fish were netted only in the shallowest zone, and the largest were found evenly distributed throughout depths up to 25 m. All sizes were netted at depths be*bween 0 and 10 m. There is therefore considerable overlapping between the ranges of both species. The overlapping of ranges if probably greater than indicated since the smallest fish, which were netted only in the shallowest zone (i.e. that zone frequented by most Rooky Mountain whitefish) are represented by a mesh which gills them less frequently than they occur in the actual popu• lation. In Morrison lake the distribution of the Eastern whitefish parallels that of the Babine fish except that it may be slightly shifted shorewards. Again the smaller fish are concentrated oloser inshore than the intermediate sised fish which tend to range deeper. Koelz (1927) from the reoords of gill-nets, pound nets and the ob• servations of commercial fishermen ooncluded that the Eastern whitefish in Lake Michigan, Lake Huron, Lake Superior and Lake Nipigon move in a regular manner in and offshore at various seasons. When the ioe breaks they are found abundantly in moderately deep water but soon move onto the shoals as the summer approaches; by mid-summer they have again gone to deeper waters and remain scattered until autumn, when they approach the shores once more. They remain in shallow water during the spawning and through• out the winter, moving to deeper water just prior to the ice-break, driven there "possibly by heavy shore ourrents or in search of food." The "shallow" and "deep" waters Koelz refers to are about 12 m. and 3G m. respectively, but vary somewhat among the four lakes. He also mentions that in all lakes they are sometimes found at depths of 120 m., where such depths occur near shallow areas, but that they prefer depths shallower than these. There was evidence to indicate that these fish, which travel in schools, do not move far along a lake (i.e. parallel to the shore). In Lake Nipigon large whitefish are typically found in depths of 15 to 45 m. (Clemens et al, 1924). At such depths Pontoporeia and Chironomidae larvae are abundant. MoHugh (1939) states that in Okanagan lake, British Columbia, the i7- Eastern whitefish was caught at depths ranging from 6 to 42 m., and the Rocky Mountain whitefish from shallow water to a depth of 16 m. He con• cludes that the Rocky Mountain whitefish appears to inhabit shallower waters than the Eastern whitefish, "although the range of the two overlap to some extent". Downing (1908) lists typical depths at which the Eastern whitefish are most frequently caught in certain lakes, as follows: Lake Ontario 18 - 36 m., Lake Erie 22 - 56 m., Lake Huron 18 - 64 m., Lake Michigan 22 - 36 m., and Lake Superior 18 - 27 m. Throughout the literature quoted there are several references to the fact that the Eastern whitefish is sometimes caught at particularly great depths, but, in general, these fish tend to school in only moderately deep water, and their typioal range is fairly similar in a variety of lakes. THE FOOD OF TEE OTHITEFISHES. Materials and Methods. Stomachs were removed from metted fish, preserved in formalin and shipped to the Pacific Biological Station at Nanaimo for later analysis. During the autumn of 1948, while in attendance at the University the writer made stomach analyses of the whitefish caught in Lakelse, Babine and Morrison lakes during 1945, 1946 and 1947. These comprised a total of abouj 200 stomachs of Eastern and Rooky Mountain whitefish, The data on the analyses of 96 Eastern whitefish from Morrison lake, 17 Eastern whitefish and 39 Rooky Mountain whitefish from Babine lake (netted in 1946 and 1947) have also been made use of here. These analyses were made by Mr. J. A. McConnell of the Paoific Biological Station. Stomachs were severed at the oesophagus and pyloric sphinoter. The contents were removed dry to petri dishes, divided into the respective groups, the numbers of organisms of each group counted, and the volume of a group and the total volume determined by water displacement. The content of each stomach was recorded on cards which carried the pertinent data relating to the fish. The two most useful measures of stomaoh analyses are those referring to the number of fish which have fed upon an organism, and the volume of that organism in the sample, expressed as a percentage of the total volume. Both these measures must be balanced against eaoh other and should be interpreted in terms of others given. The number of stomachs which contain an organism will often indicate the importance of that organism as food, but the value is subject to distortion sinoe large amounts of one organism may ooour in most of -the stomachs, while only small amounts of another organism may be present in the same number of stomachs. In the case of the per cent volume, this may be great yet may result from representation in only a few stomaohs To render the results of stomach analyses more readily appraisable a measure has been defined which expressed as a unit the importance of each food organism both in terms of the number of fish which have consumed it, and of its relative abundance in the total amount of food consumed. This unit will be called the "Consumption Index". It is defined as the product of the number of fish which have consumed an organism and the average volume of that organism in the stomachs of the total sample of fish. Hereinafter the Consumption Index will be referred to as the C.I. The significance of the C.I. is of course limited. It is not additive within a sample sinoe the fish will probably have eaten more than one kind of organism - molluscs and chironomid larvae, for example. Sinoe the C.I. is the product of actual numbers of fish and volume of food, it cannot be compared year to year, unless the numbers of stomachs of each year's sampling is the same. Food of the Rooky Mountain Whitefish in Lakelse Lake. Tables xvm- , xi-x, , xx. record the analyses of the 1945, 1946 and 1947 samples. (The 1945 sample will be emphasized since it is the largest). In all cases fish with empty stomachs are included in the various determinations. Immature aquatic insects constituted the most important items of diet. The remainder of the food was made up almost enitrely of pelecypods and gastropods. Aquatic insects, as nymphs and larvae, occurred in TABLE Xv/tt. STOMACH ANALYSES OF 62 ROCKY MOUNTAIN WHITEFISH CAUGHT BY GILL-NET IN LAKELSE LAKE. April 16th to July 15th, 1945 No. of Stomachs Total No. Total Vol. Av. NO. AT. Vol. •with in all in all per per % Organism Stomachs Stomachs Stomach# Stomach^ Volume C.I.x Insecta Ephemerida 35 319 20.90 5.145 .337 23.95 11.8 (nymph) Odonata 3 3 .35 .48 .006 .40 (nymph Trichoptera 26 306 16.81 4.938 .271 19.26 7.0 (larva & case) Diptera 7 2832 12.90 45.677 .208 14.78 1.5 (Chironomid larrae & pupae0 Coleoptera 2 2 .02 .032 T T (adult) Remains - - • .60 .010 .69 Mollusca Gastropoda 8 115 3.89 1.855 .063 4.46 0.5 Pelecypoda 7 598 25.80 9.645 .416 29.57 2.9 Crustacea Amphipoda 3 126 .30 2.032 .005 .34 (Hyalella) Fish Eggs 1 1.00 .016 1.15 Miscellaneous .02 T T Plant 12 4.67 .075 5.35 No. of Stomachs containing food - 61 No. of Stomachs empty - _1 Total No. of Stomachs . 62 # Total Sample. st Consumption index. TABLE */* STOMACH ANALYSES OF 15 ROCKY MOUNTAIN WHITEFISH CAUGHT BY GILL-NET IN LAKELSE LAKE. MAY 16th to JULY 26th, 1946 No. of Stomachs Total No. Total Vol. AT. NO. AV. Vol. with in all in all per per % Organism stomachs Stomachs Stomach^ Stomach^ Volume Insecta Ephemerida 6 56 2.72 3.73 .181 10.19 (nymph) Trichoptera 7 270 15.00 18.00 1.000 56.24 (larva & case) Odonata 2 20 1.10 1.33 .073 4.12 (nymph) 1 .05 .003 .19 Remains Mollusca 2 51 2.00 3.40 .133 7.49 Gastropoda 3 110 5.60 7.33 .373 20.99 Pelecypoda 1 .20 .013 .75 Plant No. of Stomachs containing Food 14 No. of Stomachs empty _1 Total No. of Stomachs 15 # Total sample. TABLE XX- STOMACH ANALYSES OF 7 ROCKY MOUNTAIN WHITEFISH CAUGHT BY GILL-NET IN LAKELSE LAKE. (Standard and Experimental). June, 1947 No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organism Stomachs Stomachs Stomach^ Stomach^ Volume Insecta Ephemerida 3 17 .74 2.429 .206 4.82 (nymph) Trichoptera 2 21 .80 3.000 .114 5.22 (larva & case) Diptera 2 850 2.90 121.429 .414 18.90 (Chironomid larvae) Mollusca Gastropoda 1 1 T .143 T Pelecypoda 2 ' 140 9.40 20.000 1.20 61.27 Plant 1 - 1.50 - .21 9.78 No. of Stomachs Empty - Nil. # Total sample. approximately 80 per cent of the stomachs, and constituted 60 per cent of the diet by volume. Amongst these the mayfly nymphs oourred most frequently, and made up the greatest volume (for though the volumes of Triohoptera were greater in the 1946 and 1947 samples, they included the volume of larval cases). The principle Ephemerida in Lakelse were the burrowing type of the genus Ephemera. Chironomid and caddis larvae con• stituted an approximately equal per cent volume, but the chironomids occurred in only 11 per cent of the stomaohs as opposed to the presence of caddis larvae in almost 42 per cent of the stomachs. Damsel-fly nymphs, adult aquatic beetles and other unidentified insect remains made up the small remaining amount of food. The pelecypods probably ranked second in importance to the mayfly nymphs if consideration is again given to the volume of oaddis oases. However, in the 1945 sample they occurred in only 11 per cent of the stomachs. Like the oaddis cases, the molluscan shell, though included in the volume determinations, did not constitute food. The gastropods (the chief form of which was Planorbis) were of relatively little importance. The amphipod Hyalella was found in only 3 of the stomachs of the 1945 sample (4.8 per cent). Fish eggs in the same sample were in the eyed stage and were probably those of the Three-spined stickleback. Bryozoa and plant remains, including algae, were taken frequently, but for the most part had probably been ingested indiscriminately along with other foods. The analyses may be summarized and compared by listing the more important C.I.'s, as based on the 1945 sample: 7+ Mayfly nymph* 11.8 Caddis larvae and oases 7.0 Pelecypoda 2.9 Chironomid larvae 1.6 Gastropoda 0.5 Seasonal Variation of Food. All but eight of the 62 stomachs of the 1945 sample were from fish netted in late May and in June. No marked variation in diet oould be ob• served, but it is most probable that certain species variations did oocur during this period. The 1946 and 1947 samples were from a similar period. In February of 1948 netting through the ice yielded a total catch of 5 Rock)/ Mountain whitefish. One fish (9 inches fork length) had 12 gastropods and 10 chironomid larvae in its iomaoh; the seoond inches fork length) had only a traoe of plant remains; the third (7^- inches fork length) had eaten 6 amphipods and 1 chironomid larva. The records of the 1945 bottom dredgings indicate that at the position and depth where these fish were netted, bottom organisms are scarce. The Food of Rocky Mountain Whitefish in Babine Lake. Analyses have been made on 121 stomachs of this species from Babine lake. The data are presented in Tables xxt and . Thirty- nine stomachs were of fish netted in 1946; these were examined by Mr. J. A, McConnelJof the staff of the Pacific Biological Station. The re• mainder were examined by the writer in the autumn of 1948, and of "these 62 were from fish netted in Division II, and 20 from Division I, all from 1947 oatches. TABLE AK/. STOMACH ANALYSES OF 76 ROCKY MOUNTAIN WHITEFISH CAUGHT BY GILL-NIT IN DIVISION II, BABINE LAKE. DATA OF 1946 and 1947 COMBINED. No. of Stomachs Total No. Total Vol. Av. N0. Av. Vol. with in all in all per per % Organism Stomachs Stomachs Stomach^ Stomach^ Volume C.I.x cc. Insecta Trichoptera 41 1250 34.72 16.4 .457 33.34 18.74 (larva & case) Coleoptera 6 9 .16 .1 .002 .15 .01 (adult) Diptera 21 1236 7.25 16.3 .095 6.96 2.00 (mostly Chironomid pupa & larva) Plecoptera 2 5 .15 .1 .002 .14 - (nymph) Ephemerida 14 246 5.96 3.2 .078 5.72 (nymph) Remains - - .57 - .008 .55 1.09 Crustacea Amphipoda 2 46 .35 .6 .005 .34 .01 (Hyalella) Cladocera 12 20,000 3,30 263.2 .043 3.17 .52 (Daphnia & Bo smina) Copepoda 13 1,000 1.10 13.2 .014 1.06 .18 (Heterocope) Mollusca Gastropoda 26 1,800 28.35 23.7 .373 27.22 9.70 Pelecypoda 7 1.200 13.64 15.8 .179 13.10 1.18 Plant - 7.33 - .096 7.04 - Miscellaneous - 1.27 - .017 1.22 - No. of stomachs with :foo d - 72 No. of stomachs empty - 4 (5.\5% of total) Total no. of stomachs - 76 # Total sample x Consumption Index TABLE XXII STOMACH ANALYSES OF 46 ROCKY MOUNTAIN WHITEFISH CAUGHT BY GILL-NET. DIVISIONS I AND iIII . BABINE LAKE. DATA OF 1946 and 1947 COMBINED. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. - with in all in all per per % Organism .s Stomachs Stomachs Stomach# Stomach Volume C.I.x Insecta Triohoptera 25 161 12.6 3.6 .28 55.2 7.00 (larva & case) Ephemerida 3 21 .2 .5 - .9 - (nymph) Plecoptera 2 42 .7 .9 .02 3.0 .04 (nymph) Odonata 1 3 .8 .1 •02 3.4 .02 (nymph). Diptera 14 121 1.3 2.7 .03 5.6 .42 (larva & pupa) Remains 1 - T - — — - Hydraoarina 3 32 .1 7.1 - .4 - - Mollusoa Gastropoda 11 192 6.1 4.3 .14 26.3 1.54 Pelecypoda 1 6 .1 .1 - .4 - Copepoda Heterocope 2 ? .4 - .01 1.7 .02 Cladooera Bosmina 5 ? .2 - - .9 - Plant 6 _ .5 _ .01 2.1 .06 No. of stomachs with food - 33 No. of stomachs empty - 12 (26.6$ of total) Total no. of stomaohs - 47 # Total sample x Consumption Index rr Results from these analyses are similar to those for the Lakelse fish. Small differences occur which are interesting in terms of possible variation in abundance. Insect young dominated the diet; they constituted the greatest present volume, and were consumed by more fish than were other organisms. Eighty-seven (72 per cent) of the 121 fish had eaten Insecta (almost en• tirely immature forms); 39 per cent had fed on molluscs, and 21 {-17 per cent) on the small Crustacea. C.I.'s based on the 121 stomachs were as follows: Insect - young 120.1 Molluscs 39.0 Small crustaceans 2.7 Acceptance of C.I.'s must again be modified by the fact that the Insecta volume included the cases of caddis larvae. The average volume Trichoptera per stomach should be considerably reduced therefore (probably by approximately one-half). The C.I. for Insecta is thus too high, but remains greater than that for the Mollusca. The shells of molluscs in a somewhat parallel manner affect their C.I. In Lakelse lake mayfly nymphs formed the most important group of organisms in the diet of the Rocky Mountain whitefish. In Babine lake, both in terms of the amounts consumed, and $he number of fish which had fed on them, mayfly nymphs were the least important of the three major groups of young insects which made up the bulk of the diet (i.e. caddis larvae, chironomid larvae and pupae, and mayfly nymphs). In Babine lake the Trichoptera provide the highest C.I.'s. Pelecypods ranked high in the diet of the Lakelse fish and gave the third C.I.j they were very seldom consumed in Babine lake, and gave a low C.I. On the other hand, the Gastropoda in Babine not only take the place of the Pelecypoda, but constituted a C.I. second to the Trichoptera. Only a few Hyalella were taken by a few Rocky Mountain whitefish in Lakelse lake. In Babine lake the variety of crustaceans consumed was greater by the inclusion of such plankton forms as Cladocera (Bpsmina and Daphnia) and Copepoda (Heterocope), along with a small number of the amphipods (Hyalella). Of these the Cladocera were most frequently taken (14 per cent of the fish examined). The total of 121 specimens was made up of catohes from the three Divisions of the lake, and although the fish from either Division were widely separated from each other, their diets were suprisingly similar. An interesting exception was that of the 23 specimens from Division I; none had eaten pelecypods. Food of the Rocky Mountain Whitefish in Morrison Lake. Only 15 of these fish have been caught during three summers of netting in Morrison lake. Eleven of them were taken in 1947, and the stomach contents of 9 of these were examined by the writer to provide the following data. The stomach analyses are summarized in Table w- These fish were taken in the same positions at which many Eastern whitefish were netted. The bulk of the food was made up of aquatic insect material and of immature insects in particular. Only 1 fish had taken a minute quantity of plankton crustaceans, and in its stomach these organisms were mixed together with plant and some insect material. Insofar as the reliability of so few speoimens permits, it seems that the Rocky Mountain whitefish in Morrison lake remains essentially a bottom feeder. Its diet in both Morrison and Babine lakes is similar. 77 TABLE WU- STOMACH ANALYSES OF 9 ROCKY MOUNTAIN WHITEFISH CAUGHT BY GILL-NET IN MORRISON LAKE, 1947. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach^ Volume c.c, Insecta Ephemerida 3 - 1.70 - .19 23.0 (nymph) Trichoptera 5 60 4.80 . 6.6 .53 64.9 (larva & case) Plecoptera 1 1 .10 - .01 1.3 (nymph) Odonata 1 1 .08 - .01 1.1 (nymph) Diptera 2 11 .22 1.2 .02 3.0 (chironomid adults) Remains 1 - T - - - Crustacea Cladocera 1 20 T 2.2 - Mollusca Gastropoda 1 5 T .6 - Plant ' - .50 .06 6.8 No. of stomachs with food - 8 No. of stomachs empty - JL_ (11.1$ of total) Total no. of stomachs - 9 # Total sample. Unlike the Eastern whitefish in Morrison lake, the Rocky Mountain whitefish doeB not appear to have made an attempt to substitute plankton Crustacea for a diet of bottom organisms. The average volume of food per stomach was distinctly low. Discussion. The food of the Rocky Mountain whitefish has been described fre• quently as consisting primarily of immature aquatic insects. McHugh (1940) stated that the diet varied with the locality and according to the abundance of bottom organisms, feeding at any level, including the surface, taking place in waters that were poor in bottom fauna. Munro and Clemens (1937) have stated that while aquatic insects constituted the most important food, the eggs of kokanee and ooho were sometimes taken in considerable numbers* McHugh (1939) mentioned that the summer food of the Rocky Mountain whitefish in Okanagan lake, B.C., was com• prised chiefly of Cladocera, with lesser amounts of squatic insects. According to McHugh (1940), first year fish fed almost exclusively on such bottom organisms as the larvae and pupae of the chironomids, and frequently upon ephemerid nymphs. Cladocera and other free-swimming forms appeared occasionally in the diet, and there was a rare occurrence of terrestrial insects. These young fish were taken in shallow water along the shores of lakes and streams. Fish in their second year and older fed more variedly. Bottom organisms still predominated and consisted of the larvae and pupae of chironomids, and other aquatic Diptera, larval Ephemerida and Trichoptera and Gastropods. Cladocera and terrestrial flying insects ocourred only occasionally, but then in considerable numbers. McHugh found considerable difference between the diets of lake and stream fishes. This difference was attributed to the variation in the availability of the different forms in the two types of environment. Stream fish fed chiefly on such stream bottom forms as mayfly nymphs, stonefly nymphs and caddis larvae. According to McHugh size was the probable factor controlling the variation in diet with age. This was demonstrated by the fact that larger organisms were absent in the stomachs of the younger and smaller fish. Also lesser proportions of the smaller organisms, such as chironomid larvae, were present as the fish grew older and larger. Fish of intermiedate size fed primarily on intermediately sized organisms suoh as mayfly nymphs, stonefly nymphs, caddis larvae and terrestrial insects. The largest organisms suoh as Gastropoda occurred in greatest volume in the stomachs of the oldest fish. Seasonal variations in diet have been demonstrated by Munro and Clemens (1937) and by McHugh (1940) for Okanagan lake. In Okanagan lake, in late winter and early spring, the diet consisted almost exclusively of aquatic insect larvae. As the spring and summer progressed the variety was increased by the addition of terrestrial insects and microCrustacea such* as Cladocera. The greatest variety occurred in late summer, but the aquatio inseot larvae were still important. Fish about to spawn apparently restricted their feeding considerably. Food of the Eastern Whitefish in Babine Lake. Table MM- combines the analyses of 1946 and 1947. The Eastern whitefish of Babine lake is essentially a bottom feeder. Bottom organisms such as larval insects and small molluscs, made up more than 80 per cent by volume of the stomaoh contents of the 59 specimens. Plankton Crustacea such as the copepod Heterooope, and the Cladocera Bosmina and Daphnia were occasionally important. As with the Rocky TABLE XX/* STOMACH ANALYSES OF 39 EASTERN Yi/HITEFISH CAUGHT BY GILL-NET IN DIVISION I AND II, BABINE LAKE. 1946 and 1947 DATA COMBINED No. of Total No. Total Vol. AT. NO. AT. Vol. stomachs in all in all per per % C.I. x with Stomachs Stomachs Stomach^ Stomach^ Volume Organism Insecta Trichoptera 9 305 26.25 7.82 .673 15.7 6.06 (larra & case) Diptera 7 137 .63 3.51 .016 .4 .11 (Chironomid larva & pupa) Ephemerida 1 1 .10 .03 .003 .1 (nymph) Remains - - T T T Crustacea Amphipoda 2 4 T .10 T T - (Gammarus %-alella) Copepoda 7 ? 13.10 - .336 7.9 2.35 (Hetrocope) Cladocera 4 ? 1.30 - .033 .8 .13 Mollusca Gastropoda 24 3000 118.41 76.92 3.036 71.0 72.8 6 Pelecypoda 3 91 1.20 2.33 .031 .7 .09 Fish Cottus 1 2 1.50 .05 .038 .9 .04 Plant 19 - 3.82 - .098 2.3 1.86 Miscellaneous - - .50 - .013 .3 No. of Stomachs with food - 37 No. of Stomachs empty - 2 . (5.1# of total) Total no. of Stomachs - "39" # Total sample x Consumption Index te Mountain whitefish, when encountered they were consumed in large numbers* The small gastropods constituted the most important single item of food. Almost 62 per cent of the fiBh had eaten these, and their volume in the stomachs was approximately 71 per cent of the total food volume. The more important C.I.'s are as follows: Gastropoda - 72.86 Combined Molluscs - 73.61 Pelecypoda - .09 Trichoptera - 6.06 Combined Insecta - 13.15 Diptera - .11 Copepoda - 2.35 Combined Crustacea - 5.69 Cladocera - .13 The range of sizes and dges of the 39 fish were approximately from 7 inches (2 years) to 19 inches fork length (11 years). Only traces of gastropods were found in fish less than 16 inches in fork length. In fish of 16 inches or greater, gastropods occurred more frequently and in larger numbers. Ingestion of the smaller forms was not confined to the smaller, younger fish. For example, of the four fish that had eaten cladooerans, large numbers were found in one 18 inch fish and one 11 inch fish, and traces were found in one 18 inch fish and one 15 inch fish. The oopepod Heterocope was found only in fish 15 inches fork length or greater. Chironomidae larvae had been taken by fish of 7, 9, 11, 16 and 18 inches fork length. Caddis larvae were eaten more frequently by smaller fish, but the larger genera had been taken by larger fish. The sample was biased towards the larger fish since 26 of the 39 specimens were 16 inoh fork length or greater, while 13 only were under 16 inches. Nevertheless it is reasonable to state that the larger fish fed more on the larger organisms such as the molluscs and the larger forms of oaddis larvae. Seasonal variations in diet cannot be demonstrated. No spring, winter or autumn catches were made. Food of the Eastern Whitefish in Morrisom Lake. The Eastern whitefish is abiandant in Morrison lake. It is netted there more frequently than any other species. Visits to this lake werd made by the field party of Division I once a month, for a period of a week, during June, July and August in 1946 and 1947. The description of the food of the Eastern whitefish in Morrison lake is based upon the analyses of 95 specimens made by Mr. J. A. MoConnell of the Pacific Biological Station. These constituted all the available samples. Table W presents the summarized and treated data* The food of the Eastern whitefish in Morrison lake is strikingly different from that in Babine lake, and in all divisions of Babine lake. In Morrison lake 97.6 per oent of the fish whose stomachs contained any food at all, had eaten plankton crustaoea. Only 12.6 per cent of the total samples had eaten small amounts of larval Insecta, mostly chironomids; and only 8 of the 95 specimens (8.4 per cent) had taken small numbers of mollusos. The important crustacean was the copepoda Heterocope. This form alone constituted 86 per cent of the total volume of food consumed by the 95 fish, and had been taken by 71.5 per cent of the fish. C.I.'s are as follows: Dlptera larvae (mostly Chironomids) .0 Total Insecta .0 Heterocope 18.6 Daphnia .4 Total Crustacea 23.7 "Bosmina .1 Pelecypoda .1 Total Mollusoa .1 TABLE XXV. STOMACH ANALYSES OF 95 EASTERN WHITEFISH CAUGHT BY GILL-NET. MORRISON LAKE, 1947. July 2 - August 4. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per /o Organisms Stomachs Stomachs Stomach^ Stomach^ Volume C.L. % c.c, c.c. Insecta Diptera 12 52 0.19 .55 .002 .63 .02 (larva) Amphipoda 1 .01 Gammarus Copepoda Heterocope 68 13,200 25.92 138.95 .273 85.85 18.56 Diaptomus 1 50 0.11 .53 .001 .31 Cladocera Daphnia 28 4400 1.38 46.31 .014 4.40 .39 Bosmina 16 1700 0.45 17.89 .005 1.57 .08 Hydracarina 2 0.02 0.03 Mollusca Pelecypoda 5 30 1.36 .32 .014 4.40 .07 Gastropoda 3 5 0.06 .05 T T Plant 0.90 .009 2.83 No. of stomachs with food 83 No. of stomachs empty 12 (12.6$ of total) Total no. of stomachs 95 # Total sample x Consumption Index The obvious possibility of a paucity of bottom organisms in Morrison lake will be discussed later. The data have been examined to determine whether any notable differences occurred between the diets of fish of different sizes. Since the copepod Heterocope contributed 86 per cent of the total volume of food found, the variations could not be great as long as sufficient numbers of small or large fish were represented in the sample. Of the 95 specimens, 35 were fish whose fork length ranged from 5 inches to 11^- inohes; the remainder (60) ranged from 12 inches to 15j|- inches fori length. One important difference only was noticed, namely, that the smaller fish had taken the cladooeran Daphnia. Thus 16 fish of fork lengths 7 to 9j§- inches, out of a total of 32 of those sizes, had taken all but 25 per cent of the total volume of these organisms- The 25 per cent had been consumed in small amounts by only 11 out of the 62 fish larger than &§• inches. The few fish that had' eaten molluscs ranged in size from 12 to 14^- jbahes standard length. Discussion. McHugh (1939) has made a study of the food of Eastern whitefish which had become established in Okanagan lake, B.C., following introduction as fertilized eggs. He found considerable seasonal variation; thus in the summer (July - August), plant material formed the greatest bulk of the stomach contents, followed by small fish, Cladocera and insect material; while in the autumn (September - Ootober) insect material predominated, followed by Cladocera and peleoypods. The food of both Eastern and Rooky Mountain whitefish in this lake reflected the very marked scarcity of bottom organisms as determined by dredging. In lake Nipigon, Ontario (ClemenB et al 1924), the young fish were first plankton feeders, but soon turned to bottom organisms* Pontoporeia, Chironomidae larrae, mollusoa and Ephemeridae nymphs, in that order, were the important food of the larger fish. The kinds and proportions of the various organisms varied greatly due to the great range in depth at whioh the fish were taken (from 1 to more than 90 m.). Most of the larger fish were found between 15 and 45 m., and at such depths, Pontoporeia and Chironomidae larvae were most abundant. In several Manitoban lakes, Bajkov (1930) observed that the important food items for the adult fish were such bottom organisms as amphipods, chironomid larvae and small molluscs. Presumably by experiment, (feeding hatchery fry on natural larvae) he demonstrated that young fry in their first summer month fed mostly on plankton, but even in that month turned to suoh bottom organisms as Diptera larvae. Hart (1939), from direct stomach analyses, found a notable scarcity of plankton organisms in young fish. The bulk of their food comprised uladocera, Copepoda, and insect larvae, mostly chironomids. Plankton organisms dominated the food of fish taken in deep water, though bottom organisms were not uncommon. Bottom organisms, especially chironomid larvae, were of greater importance in Lake Superior and Lake Nipigon than in Shakespear Island lake and Lake Ontario. In his summary of the findings of other investigators, Hart mentions that Hankinson showed that the Entomostracans, Bosmina longirostris, Diaptomns ashlandi and Cyolops viridis constituted the important food of young fish in Lake Superior; and that Forbes by experimental feeding, demonstrated that the preferred food of newly hatohed fry was Entomastraca, especially Cyolops and Diaptomuaj. ff Hubbs, according to Koelz (1927) found the food of Lake Huron whitefish to be composed mostly of the amphipod Pontoporeia', supplemented by small molluscs. Chironomid larvae were also common. A summary of the food of the whitefish in Lake Simcoe (R awson 1930) indicated that it was composed of molluscs, 36 per oent, ephemerid nymphs, 30 per cent; ohironomid larvae 16 per cent; caddis larvae, amphipods, hydrachnids, ostracods and fish eggs, 18 per oent. Most analyses also included small quantities of squatio and terrestrial insect material, oaddis worms, bryozoan statoblasts, and occasionally fish, (generally Cottus). In Great Slave lake and Lake Athabaeka, the food of the Eastern whitefish was predominantly the amphipod Pontoporeia (Rawson 1947, Larkin 1948). In Great Slave lake Pontoporeia formed 60 per cent by volume the food of the Eastern whitefish; 40 per cent in Lake Athabaska. In Great Slave lake, Pontoporeia made up to 70 per cent of the bottom fauna in zones of 25 - 100 m., and at these depths constituted more than 70 per cent of the food of the whitefish (up to 85 per cent at times). In shallower water it was replaced by small molluscs. Similarly in Lake Athabaska, though to a lesser degree, Pontoporeia was of particular importance in deeper water, being replaced in the diet in shallow water by molluscs. Summary. To estimate the relative importance of various organisms as food for whitefish, an-index, termed the "Consumption Index" was developed and employed. The C.I. was defined as the product of the number of fish (in a given sample) whioh had consumed an organism and the average volume of the organism in the stomachs of the total sample of fish. The function of the C.I. was to indioate, as a unit, the importance of an organism as food, both in terms of the number of fish in a sample whioh had consumed that organism, and the quantity of that organism in the stomachs of the fish sampled. The bulk of the summer food of the Rooky Mountain whitefish in Lakelse lake was made up, and in the order given, of the following organisms: Mayfly nymphs, caddis worms, small peleoypods, Chironomidae larvae and small gastropods. In Babine lake also, the Rocky Mountain whitefish, in summer, fed primarily on young insects and small molluscs and Crustacea. In this lake the important insects were caddis worms, Chironomidae pupae and larvae, and mayfly nymphs, in that order. The small peleoypods were seldom con• sumed in Babine lake, but the gastropods ranked second to the caddis larvae in the diet of the fish. A greater variety and more plankton Crustacea were taken by the Babine Rocky Mountain whitefish. The stomaoh contents of the very few Rooky Mountain whitefish netted in Morrison lake oonsisted primarily of immature aquatic insects. Only traces of plankton orustacea were found in their stomachs. The Eastern whitefish in Babine lake had fed mostly, in summer, on gastropods, caddis worms and plankton Crustacea (such as the cladocera Bosmina and Daphnia), in that order. Gastropods and the copepod Heterooope, had been taken chiefly by the larger fish. Chironomidae and Trichoptera larvae had been eaten by fish of all sizes, but the larger caddis worms had been consumed by larger fish. The food of the Eastern whitefish in Morrison lake differred markedly both from the food of that fish in Babine lake, and from the food of the Rocky Mountain whitefish in Morrison lake. More than 90 per oent of the food of Eastern whitefish in Morrison lake was made up of plankton crustaoea, the most important form being the oopepod Heterocope. Heterocope constituted 86 per cent of the total volume of food found in all the stomachs. Most of the cladocera Daphnia, had been taken by the smaller fish* •••* ooo •••• 91 BOTTOM FAUNA. The Bottom Fauna of Lakelse Lake* Introduction* From the evidence of the food analyses it is apparent that the Rocky Mountain whitefish of Lakelse lake feed almost exclusively on bottom organisms, such as the young of aquatic insects and small molluscs. An examination of the bottom fauna will therefore provide some evidence on their abundance and availability to these and other species of fish which are primarily dependent on them for food* Methods and Materials. The analyses whioh follow are based upon 73 dredge hauls which were made in Lakelse lake during the period June 5th to September 5th in 1945, The location and direction of the various dredge lines is shown on the map of Fig, «3 , Most of the dredging was concentrated along the lines I and II, Various depths were sampled at these lines on four occasions during the summer. Single samples at fewer depths were made at the remaining positions* The Ekman dredge used sampled an area of 484 cm2. (76,6 in.2). The contents were transferred to pails or wooden tubs and were then washed successively through three screens. The only data available which desoribeB these screens states that they were, wire wire 3/32", and cotton 1/16". These dimensions are probably those of the size of the holes or meshes (unstretched). The wire screens were also described as "fine wire", and the cotton, as braided and of broad twine. Since the finest screening used by Rawson (1930) was silk bolting cloth, 1400 meshes per square inoh, then the '- Skeena technique could have taken very few of any but the macroscopic organisms. The organisms were preserved in 5 per cent formalin. Sampling limitations of the dredge technique have been adequately described by Rawson (1930). These are primarily the result of the nature ©f the bottom, leakage from the mouth of the dredge as it is hauled upward, loss of organisms during screening, and the error due to an uneven dis• tribution of the fauna on the lake bottom. Whenever a haul was made the depth of its position and the distance from the nearest shore were noted. The Lakelse samples and those taken at Babine lake during the same year were examined during the autumn of 1948. The contents were removed from their labelled bottles to petri dishes, and the various organisms were separated, identified and counted. No attempt was made to determine wet or dry weights, and in the time available it was possible to make only the gross identifications indicated in the various tables. Tables and xxv//. and Figs. /z to show the abundance of the various organisms in the lake, the relative abundance at different depths and at varying distances from shore. Three types of zone are referred to in Lakelse lake, and they are indicated by their depths. These are the littoral (0 - 5 m.), the sub- littoral (5 - 15 m.) and the profundal (greater than 15 m.). Eggleton (1939) defines the littoral zone as that region lying between the shoreline and the approximate lakeward limit of rooted aquatic vegetation; the profundal, as that region which extends from the greatest depth, up the slope towards shore to a level somewhat above that corresponding to the average limit of the hypolimnion; and the sub-littoral lies between these two. These definitions approximate those of Welsh (1935). Certain of the characteristics of the profundal as given by Eggleton (1939) are: a permanently low temperature, lack of dissolved oxygen in some part, acidity of water at times, little or no light, and often an accumulation of carbon dioxide, methane or other gases of decomposition. It does not follow any sharp transition from the sub-littoral. The sub-littoral has been des• oribed as a zone of "heaping refuse" and as the "shell zone" by virtue of its collection of dead molluscan shells (Eggleton, loc sit). Perhaps it is best understood by considering^ aone of transition from the con• ditions of the littoral, to'those of the profundal. Some of these characteristics do not obtain for the various zones in Lakelse lake, and others have not been determined. It has been con• venient, however, to apply the classification for the following reasons. Rooted aquatic vegetation in most of the lake is abundant to depths up to 5 m. It does not occur at depths greater than this according to any of the records. The 0 - 5 m. zone can therefore be considered as the littoral zone (Eggleton 1939). A depression with a maximum depth at 32 m. is at the northern end of the lake. The occasional thermoclines re• corded for the lake were found only in this region; and in late summer the limit of the hypolimnion was found at approximately 20 m. Temperatures were permanently low at these depths, although at 24 m. they have reached 7.3°C. The lowest oxygen content recorded was 45 per oent saturation at 24 m. Daylight is of very short duration at suoh depths. In relation to the overall characteristics of Lakelse lake this region is definitely discrete, and can therefore be desoribed as the profundal (Eggleton, loo sit). S o too, is the region of rooted aquatic vegetation. 9*- Results* The total number of organisms taken in the 73 hauls was 2653* This constitutes an overall average of 36.3 organisms per dredging, or approxi• mately 750 organisms -per square m. The bulk of these organisms was made up of the following seven groups, in order of their relative abundance; Pelecypoda, Amphipoda (Hyalella), Gastropoda, Ephemeridae nymphs, Chironomidae larvae, Oligochaeta and Trichoptera. The remaining organisms constituted only 3.6 per cent of the total number. Table MV/. gives the occurrence of the various organisms in further detail. Table xxv//- and Fig*/-3/^ demonstrate the abundance of the more important groups of organisms at various depths. In general, the overall distribution of bottom fauna follows that described by Rawson (1930), Eggleton (1939) and others. The zone of greatest abundance lay between the shoreline and a depth of 5 m. This is the littoral zone. In this zone the concentration of the more important fauna was approximately 50.5 per dredge area or about 1045 organisms per square m. In the sub-littoral zone corresponding values were 8.7 organisms per dredge area or 180 per square m. In the profundal zone there were 15.0 organisms per dredge area or approximately 311 per square m. Characteristics of the Distribution of the Six Major Groups of Bottom Organisms. Pelecypoda. The genera Pisidium and Sphaerium of the family Sphaeriidae constituted the bulk of peleoypods present in the lake. They occurred in most habitats and at all depths. They were found most fre• quently in mud and sand in the vioinity of pondweeds. The maximum occurrence of peleoypods was in the littoral zone at a mean depth of 2.5 m. TABLE XAVA RESULTS OF THE ANALYSES OF 73 DREDGINGS MADE IN LAKELSE LAKE IN 1945, 5th JUNE TO 5th SEPTEMBER. Total Noi in Av. No. Av. No. per % of ORGANISMS 73 Hauls per dredge so. metre Total ALL 2653 36.3 751 PELEGYPODA 715 9.8 203 27 HYALELLA 523 7.2 149 20 GASTROPODA 502 6.9 143 19 EBHRMERIDA - NYMPHS 388 5.3 110 15 CHIRONOMID - LARVA 189 2.6 54 7 OLEGOCHAETA 135 1.8 37 5 TRICHOPTERA - LARVA 106 1.5 31 4 HIRUDINEA 38 ODONATA - NYMPH 17 DJPTERA - LARVA 13 MYSIS 6 CYCLOSTOMATA - LAMPREY 5 HYDRACARINA 3 HEMIPTERA 3 1.3 27 4 FISH LARVAE 3 ARACHNIDA 2 HYMENOPTERA 2 COLEOPTERA - ADULT 1 INSECTA - LARVAE 2 TABLE XXV//. THE AVERAGE NUMBER PER DREDGE OP' 6 MAJOR GROUPS OP BOTTOM ORGANISMS AT DIFFERENT DEPTHS. LAKELSE LAKE, 1945. DEPTHS - METRES ORGANISM 0-^1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 15 21 27 - • EPHEMERIDA - .20 7.80 14.05 4.75 4.80 1.06 .25 Nymph PELECYPODA 8.20 9.40 19.84 14.25 3.40 5.06 3.0 1.75 3.0 16 5.0 GASTROPODA 5.40 17.60 12.90 10.13 1.40 2.65 1.75 .50 HYALELLA 19.20 15.40 13.21 11.63 .30 .25 CHIRONOMID - 1.20 2.60 2.74 1.88 .40 1.53 3.0 .25 1.75 12.75 13.0 Larvae TRICHOPTERA- Larvae 2.40 2.60 2.58 2.63 1.60 .06 1.0 No. of DREDGINGS 5 5 19 8 5 17 1 4 4 4 1 60 ro & 50 1 CO M S» \ COMBINED 40 o COMBINED O Q EPHEMERIDA - •-b UJ LT PELECYPODA . Q 30 or GASTROPODA . AMPHIPODA IB O d CHIRONOMIDAE. • *l z > TRICHOPTERA . < 20 10 15 22 27 DEPTH METRES ff Their abundance fell to a minimum in the sub-littoral zone at depths between 5 and 19 m., but was fairly evenly distributed from these depths to the deepest water. As indioated in Fig. it is possible that their numbers increased in waters deeper than 15 m. Gastropoda. Most of the gastropods were very small species of the genus Flanorbis. These were present in greatest abundance in the littoral zone, and were found most frequently at a mean depth of 1.5 m. (Fig. Like the pelecypods they were relatively scarce in the sub-littoral zone, but none was found in depths exceeding 15 m. Hyalella sp. Only this genus of the Amphipoda was observed in the bottom fauna samples. Hyalella was not collected in depths exceeding 7m., and it was very rare in depths greater than 4 m. Its maximum abundance was close inshore at an average depth of less than 1 m. (Fig./^c)- Since this organisms is very active, it is likely that certain numbers often avoided or escaped from the dredge. This in itself, however, should not affect the measure of its relative abundanoe at various depths. These organisms were found in bottom of mud, mud and sand and marl, particularly in areas bearing pond-weeds. Ephemerida. Almost all the mayfly nymphs belonged to burrowing type of the genus Ephemera. They reached their peak of abundance at a depth of approximately 2.5 m.; very few were found in depths less than 1 m. In the sub-littoral zone, in the 6, 7 and 8 m. depths sampled, only a few were collected, at a mean depth of 5.5 m. One specimen was taken from the four samples of the 15 m. zone (Fig./3^- Chironomidae larvae. The Chironomidae larvae and the Felecypoda were the only organisms of the six major groups which were colleoted in ^JFig, 13. The distribution of the Ephemerida, the Chironomidae and the Gastropoda in Lakelse lake, 1945. /cm the five dredge hauls at depths greater than 15 m. Their abundance was apparently greatest in the profundal depths. In the littoral and sub- littoral zones they were sparcely but somewhat evenly distributed. Notice should be taken here that the considerable rise in numbers of the Chironomidae larvae in the 20 and 27 m. depths effects the overall in• creasing abundance of organisms from the sub-littoral into the profundal whioh is demonstrated in Fig,/3 . This distribution is characteristic of certain of the ohironomids and as such is of particular importance in the feeding activities of some fishes. (However, the apparent maximum in deep water may be because bottom feeding fish of several species do most of their feeding in the shallow water, thus keeping that region well cropped.) Trichoptera. Only actual caddis larvae were included in the * Trichoptera counts. Larval cases were collected frequently, mueh more so in faot, than were the larvae, but since most of these no doubt belonged rather to the accumulated debris, they cannot be thought of as indicating a greater abundance of the larvae. These larvae were quite evenly dis• tributed up to depths of 4 m. At no time were they particularly abun• dant relative to the other major organisms, but in common with the others they were least abundant in the sub-littoral. None were collected from depths greater than 7 m. In addition to the organisms listed and counted in Table Algae, Bryozoa (mostly the statoblasts), and the fresh-water Porifera, Spongilla were frequently collected in the hauls and were abundant. Abundance of Bottom Fauna in Relation to Distanoe from Shore. In Fig./^ the average number of organisms found at varying dis• tances from shore is plotted. Peaks of abundance ocourred at approximately Fig. 14. The distribution of the Pelecypoda, the Trichoptera, and the Amphipoda In Lakelse lake, 1945. lost. 70 and 230 m. from shore. The mean depths of these distances were 5 m. or less. Fewest organisms were found at distances of 100 and 400 m., and the mean depths of these distances were between 5 and 15 m. At distances between 450 to 600 m. from shore, the numbers of organisms increased some• what. These distances in each case corresponded to depths of 15 to 28 m. Therefore it is apparent that the correlation for abundance of the bottom fauna is with depth rather than distance from shore. Further Considerations on the Distribution of Bottom Fauna. The areas of various depth zones in Lakelse lake are as follows«• 0 - 5 m. - 612 ha. or 2.35 sq. mi. - Littoral 5 -10 II 396 " or 1.53 II II - 2.33 sq. mi. - Sub-littoral 10 -15 II _ 207 " or .80 n II 15 -20 II 153 " or .59 II II II 11 n II 20 -25 mm 49 or .19 .79 sq. mi. - Profundal 25 -30 It _ 3 " or .01 II ti The littoral zone constitutes approximately 43 per cent of the total area of the lake. It is thus approximately equal to the area of the sub-littoral, despite the latter's greater range of depths. The area of the profundal is about l/7 (14 per cent) of the total area. Considering all the organisms found in the dredgings, they occurred in the different zones as follows* Littoral zone, 53.7 per dredge (1112 per m.); Sub-littoral, 11.8 per dredge (244 per m.); Profundal, 15.3 per dredge (317 per m.). The weighted average for the entire lake was there• fore 628 organisms per square metre. Employing averages which have been weighted for area of depth zone, it can be said "that 76 per cent of the bottom fauna was distributed in the littoral; 16 per oent in the sub- littoral and 8 per cent in the profundal. Fig. 15. The relative abundanoe of bottom fauna in Lakelse lake at different distances from shore, and showing the average depths of such distanoes, 1945. The Bottom Fauna of Babine Lake. In July, 1946, a total of 45 dredgings was made in the three divisions of this lake. Four samples dried in transit; the remainder constituted the materials on whioh these analyses were made. Two lines were sampled in Divisions II and III, and one in Division I. A total of 9 hauls were made at depths of 25 to 100 m., and 30 hauls in depths of 1 to 10 m. Two samples were taken at 15 and 20 m. Table Xxv///- lists the organisms found in eaoh line, and gives the average numbers for the combined samples. The determined value of 453 organisms per square m. is indicative of a rather poor abundance of bottom organisms for the lake as a whole* The variety of organisms in Babine and Lakelse lake was quite similar, but in certain cases the abundance differred markedly. In Babine lake the Gastropoda were more numerous than the Felecypoda, and this is especially the case in the shallower zones of Divisions I and II. Mayfly nymphs and caddis worms were scarce. The maximum total abundance was in the 0 - 5 m. zone. Most of Babine lake is fairly deep, though the bottom slope varies considerably. In general, Division II has the steepest shoreline, and as Table xxv/tr. indicates the lines sampled here had the poorest abundance of bottom fauna. Only relatively small and scattered areas of Babine lake qualify a6 sub-littoral; that is, a zone of transition from the littoral to the profundal. ^he profundal zone will be recog• nized as such here, although as already described in an earlier section, thermal stratification throughout most of the lake was transitory and shallow. Throughout the great body of the lake there was oertainly no TABLE XXVIII. . BOTTOM FAUNA OF BABINE LAKE. ANALYSES OF DREDGINGS. 1946. AVERAGE NUMBER OF ORGANISMS PER DREDGE. DIV. I DIV. II DIV. Ill ALL DIVISIONS LINE I LINE I LINE II LINE I LINE II . -ALL LINES HYALELLA 6.6 5.0 - 1.0 .9 2.3 CHIRONOMIDAE 3.2 2.4 ,6 2.9 8.6 3.7 (LARVA) TRICHOPTERA r .4 - .1 .4 .1 (LARVA) EPHEMERIDA .2 .1 .1 .4 .1 ..2 (NYMPHS) COLEOPTERA - - .1 - - T (ADULT) • PLECOPTERA - - - .1 - T (ADULT) DIPTERA - - - 1.13 .6 T (LARVA) GASTROPODA 12.8 2.4 1.3 12.1 13.4 8.0 PELECYPODA 1.8 5.0 .7 6.8 8.6 5.0 OLIGOCHAETA .6 1.3 .1 1.1 3.1 1.4 HEMIPTERA .2 - .1 - T HIRUDINEA .2 .-3 - .4 2.0 T ARACHNIDA - - - .1 T FISH - LARVAL - .1 - - - T HYDRACARINA — *- .4 T No. of dredgings analysed 5 9 9 8 10 41 Total No. of organisms 130 150 27 212 379 898 Av. no. p§r dredge 26.0 16.7 3.0 26.5 37.9 21, Av. no. per sq. metre 538 346. 62 549 785 453 Av. depth of lines - metre 4.8 26.7 22.2 11.3 5.9 15 /o6 evidence of a "zone of shells" or "heaping refuse". Therefore the lake, excluding the northern arms and certain shallow bays, can be described as containing a littoral zone of varying depth, wider and somewhat deeper under such conditions as are present in Division I, narrow and shallow in Division II; and a profundal zone, which in much of Division II descends rapidly from the littoral. The number of dredgings made in Babine lake were too few to warrant many detailed analyses in terms of the distribution of the fauna, but for comparison with Lakelse lake the following computations have been made. In the 0 - 5 m. zone there were 683 organisms per square m.; 186 per square m. in the 5 - 15 m. zone, and 83 per square m. in depths greater than 15 m. (Lakelse values were 1112, 244 and 317 respectively). The overall average of 453 organisms was not weighted to the area of the different depth zones. When this is done the apparent abundance (for the whole lake) drops con• siderably. A'hus, approximate areas of various depths are as follows: 0 - 20 a. - 44.5 sq. mi. - 25,9% of total area 20 - 40 " - 41.2 fl " - 24.0" " " 40 -180 " - 86.1 " " - 50.1" " " Contour lines shallower than 20 m. have not been determined, but if as muoh as one-half of the area of the 0 - 20 m. zone i6 used for the area of the littoral, then the approximate weighted average for the lake is 203 organisms per square m. (22.25 x 683) - (22.5 x 186) - (86.1 x 83) - 130.6 . This is, of course, a rough estimate, but it does indicate the effect of so great an area of bottom, poor in fauna, upon the condition of the lake as a whole. The low weighted average of 203 organisms per square m. is to be expected of lakes of rather extreme oligotrophy, and in which there are no Pontoporeia. /of. In terms of the bottom feeding fish, the important fact is that the greatest abundance of organisms is in relatively shallow waters, and as netting analyses of other sections show, such fish are more or less res• tricted to depths shallower than 20 m. and are most abundant in the 0-5 zone* The Bottom Fauna of Morrison Lake* Few dredge hauls were made in this lake* In 1946 and 1947, 16 dredgings were made, but the original samples and data are not available* The summarised data of 12 Bamples have been given to the writer, and are as follows: Organisms Species Abundance Abundance per sample Oligoohaeta 1 2 specimens .17 Phyllopoda 1 2 " .17 Mollusca - Gastropoda 1 5 " .41 Lamellibranchia 2 7 " .60 Insecta - Ephemeroptera 2 10 " .90 Neuroptera 2 10 " .90 Diptera 2 31 ". 2.60 These samples were taken along two lines and at depths ranging at 1 m. intervals from 1 to 5 m., and at depths of 8, 10 and 20 m. The writer has been able to re-examine two samples collected in 1947, one from a depth of 4 m., the other from a depth of 8 m., and both from the east shore at the north end of the lake. The 4 m. sample contained 2 oligochaete worms and 1 chironomid larva; that from 8 m. had 20 chironomid larvae, (all of the genus Chironomus). Descriptions of the bottom of the various depths sampled describe most of it as a thick, black and grey mud, sometimes containing decayed wood. Too little is known of this lake to make any definite statements regarding bottom productivity. Field parties visited the lake only for /of short periods during the summers, and work was concentrated on netting, plankton hauls, collection of physico-chemical data and observance of the salmon. However, from the few dredgings taken, and from other general observation (e.g. the overall grey muddiness of the bottom), it is pro• bably safe to conclude that the shallow zones of Morrison lake are not particularly productive of bottom fauna* Since the 0-5 and 5 - 10 m. zones represent only 19*4 and 16*2 per cent respectively of the lake's total area it offers conditions markedly in contrast to those of Lakelse, ; and the paucity of bottom organisms is probably one of them. Comparisons with other Lakes* In other parts of this province a number of lakes have been in• vestigated and it is of interest to compare the abundance of their bottom : fauna to that of the Skeena lakes. Table lists various character• istics of several lakes for comparison with Lakelse lake. Table IT may . be used for further details on Lakelse lake, and for the characteristics of Babine and Morrison lakes. British Columbia lakes compared with Skeena lakes are Paul, Pinantan, Penask, Fish and Nicola of the Kamloops region (Rawson 1934), Shushwap : lake in the Thompson river drainage (Clemens, et al 1937), and Okanagan lake (clemens, et al 1939; Rawson 1942). The Skeena lakes are deoidedly poor producers of bottom organisms as compared with most of the other lakes listed in Table • The smaller and shallower lakes such as Pinantan, Penask and Fish which are more similar in these characteristics to lakelse, produce a much greater abundance of bottom fauna. Two of these lakes are definitely eutrophic, as particularly evidenced by their extreme summer stagnation. Lakelse /Of. TABLE AX/X. COMPARISON OF CERTAIN CHARACTERISTICS OF 13. CANADIAN LAKES AND THE^BUNDANCE. i OF THEIR BOTTOM FAUNA LAKELSE PAUL PINANTAN PENSSK FISH NICOLA SHUSHWAP OKANAGAN BABINE SIMCOE . ATHABASKA GREAT SLAVE Area. sq. mi. 5.5 1.5 0.6 3.0 0.75 15.0 100 143 171.8 720 3050 10500 Length, mi. 5.4 3.8 1.5 1.0 14 • 67 92.5 25 150 350 Width - mean. mi. 1.5 .3 .5 .25 1 2 1.- 14 20 120 Depth - mean. m. 7.3 34.2 12.0 11.0 14.0 25.0 69.5 49.0 15 26 - Depth - max. m. 29.9 56.0 21.0 22.0 27.0 46.0 105.0 232.0 _ 207 44 126 600" Shore develop• ments 1.8 5.6 - 16.9 3.9 6.6 2.3 - 7.4 Surface Temp. - high. °C. 20.2 20.0 20.8 17, 16 19 19.2 21.3 18.3 18.2 25 12.8 Bottom Temp. - high. °C 13.8 6.0 6.0 12.5 6.5 8.1 5.4 (64m) 4.6 7.5 ll.l(20m) 4.4 3.3 Bottom O2-I0W- ppm. 5.2 4.3 0.1 0.1 0.3 0.4 6.4 9.0 6.8 4.3 7.4 7.4 Elevation-ft. 220 2542 2600 4500 4100 2066 1150 1130,. 2332 720 690 495 approx. Yes- Stratification occas •1 Yes Yes slight ? Yes No ? slight ? occas11. V. slight unstable No No Bottom No No great, slight great. much No No No No No No Stagnation - H2S - H2S Lake type Eut. Oligc >. Eut. ? Eut. ? Oligo. Oligo. ... 01igo_._ Eut. Oligo. Oligo. No bottom similar organisms per m. #628 #1363 1700 1962 Pinantan ? 304 364 453 (#203) #820 1003 1066 # Corrected for area of depth zones. 1 I 1 lake, though shallow and small, experiences no depletion of oxygen for the probable reasons already given; it departs in other characteristics, also, from strict eutrophy. Rawson lists Nicola lake as the poorest producer of bottom fauna among the five Kamloops lakes he investigated. This lake, too, though larger and deeper than the others, showed signs of severe summer stagnation. Rawson (1934) considers the quantity of bottom fauna of Paul lake as similar to that of other small lakes in Germany and North America and describes it as "moderate". Its expected production, however, on the basis of the product of its depth and area, is less by about 50 per cent. (Rawson 1930, developed a ourve of relationship between quantity of bottom fauna and the product of depth and area). This he attributed to its extreme depth and the steep declivity of its shores. Shushwap and Okanagan lakes, because of their great areas and depths, cannot be compared directly to lakelse, but are the only two lakes listed (exoepting Babine lake), which exhibit a smaller abundanoe of bottom organisms. The morphologioal characteristics of those two lakes are quite similar to Babine lake, and it is interesting to note that the abundance of their bottom faunas is possibly quite similar. The eastern (Simcoe) and northwestern (Great Slave and Athabaska) Canadian lakes are included sinoe they represent bodies of water in which the Eastern whitefish is present in such abundance that it is fished commercially. Rawson (1930) has described lake Simcoe as eutrophic, although it never experiences any very serious oxygen depletion in the hypolimnion. In Lake Simcoe the greatest number of bottom organisms (1134 per sq. m.) were found in the upper profundal tone (30 - 35 m.), and the greatest dry weight (14.8 kgm. per ha.) in the upper sub-littoral (5 - 10 m.). The peculiarities of this distribution were effected by the great abundance of Chironomidae larvae in deeper waters. In Creat Slave lake and Lake Athabaska, the amphipod Pontoporeia makes up more than 60 per cent of the total bottom fauna both by numbers and weight. This orustaoean is generally abundant at all depths. (In Lake Athabaska its numbers are restricted in depths less than 2 metres by the high temperatures). In Creat Slave lake it contributes 65 per cent of the food of the ^astern whitefish, and 40 per cent in Lake Athabaska. (fiawson 1947, Larkin 1948). FOOD OF THE WHITEFISH IH RELATION TO SUPPLY. Lakelse Lake* Of the 62 Rocky Mountain whitefish which made up the sample for the 1945 food analyses, all but three were caught at depths between 0 and 5 m. Data presented earlier in this paper showed that 76 per cent (by number) of the bottom organisms occurred in the littoral zone (0-5 m.), 16 per cent in the sub-littoral (5 - 16 m.), and 8 per cent in the pro• fundal (15 - 50 nw). With the exception of the Chironomidae larvae, the abundance of all major organisms was greatest in the 0 to 5 m. depths. The Chironomidae larvae were most numerous in the profundal zone. To investigate the food of these fish in relation to the supply, the following comparisons have been made. Food. Bottom Fauna % by No. % by Vol. Importance % by No. % by Vol. Importance (By C.I.) (by vol.) ie larvae 66 115 4 7 1 5 Pelecypods 14 30 3 27 35 1 Ephemerida - nymphs 7 24 1 15 30 * 2 Triohoptera - larva & oase 7 19 2 4 12 4 Gastropoda 5 4 5 19 19 3 5 4 6 20 1 6 The volume of the bottom fauna was estimated by using the relative volumes of organisms as determined in the stomaoh analyses. (Since counts only were made for the bottom organisms). In the case of the Trichoptera, the bottom fauna value was doubled before determining its per cent volume, since cases had been included in the stomaoh analyses, and it was considered that they constituted approximately one-half the volume of those organisms. ltd The table on the previous page immediately suggests that the chironomid larvae were disproportionately represented in the stomaoh contents. This condition is particularly notable, since their peak of abundance was found by dredging to be well outside the apparent feeding range of the fish (as shown in an earlier section), that is, in the pro• fundal, rather than in the littoral. Beoause of their small size and also because of the relatively large meshes used for screening, most of these forms may have been lost during the prooesses of dredging and screening. This might especially happen in shallow water beoause, aquatic vegetation being abundant, leaves and stems of plants might frequently cause the jaws of the dredge to remain open, whereas in deep water, the bottom being of a more homogenous mud or ooze, the jaws would olose more efficiently. However, since so many fish (of several species) feed on these organisms in shallow water, their abundance in the deeper zone should be greater, for here the fauna is not being equally oropped. There seems little doubt that in view of the evidence provided in an earlier seotion, that the fish which had eaten the larger numbers of Chironomidae larvae found in their stomachs, had found them at the same approximate depths at which they themselves were netted. This same con• dition would apply to the Peamouth chub or other fish, all of which are very unlikely to feed extensively on the deep bottom. The abundance of organisms in stomachs and in bottom samples cannot be oompared directly, and it is customary to make the comparisons in terms of the relative importance of the different organisms on the basis of their percentage occurrence in either group. This, for example was done by Rawson (1930, 1939). However, in an earlier seotion of this paper which dealt with the food of the whitefish, it was pointed out that the percentage volume itself does not correctly indioate the relative importance as food of any organisms, and that the numbers of fish consuming an organism must also be considered. The "Consumption Index" was introduced to serve this purpose. When it was used in the case of the Lakelse samples of 1945, the importance of various organisms was as follows: mayfly nymphs, 1st (2nd in fauna); caddis worms and cases 2nd (4th in fauna); pelecypods, 3rd (1st in fauna); chironomid larvae, 4th (5th in fauna); gastropods, 5th (3rd in fauna). (So many variables and unknown factors are involved in this parti• cular problem that, in the writer's opinion, it is fruitless to carry the analysis further). With the exception of the amphipods there is no certain evidence to indicate that various organisms are being oonsumed out of proportion (less or more) to their abundance on the bottom. In the oase of the amphipod Hyalella, its percentage occurrence (by numbers) in the bottom fauna was much greater than in the food. This organism is small and active, and frequently rises above the mud. It will not be well sampled, therefore by the dredge. Assuming therefore, that its abundanoe was even greater than the bottom sampling has indicated, it was probably not consumed in accordance with its abundance. In other words it was either less available to, or less desired by the bottom-feeding fish than were the other forms. Hyalella was most abundant in extremely shallow water, at depths less than one metre. Though the maximum catches of Rooky Mountain whitefish and Peamouth chub were made in the 0 - 5 m. zone, suoh a depth of less than one metre is probably too shallow and too warm, even for their feeding. A Mote on Mysis. The finding of Mysis in Lakelse lake is believed to constitute the first record of this crustacean in either marine or fresh waters west of the Rocky Mountains (conversation with Dr. W. A. Clemens and Dr. P. A. Larkin of the Department of Zoology of this University). Besides its occurrence in the stomachs of Cutthroat trout (Tables xxx*"/- and xxx/xj., and in the 1945 bottom samples, (Table X*vl- ), Mysis was taken by plankton net in a total vertical haul made in Lakelse lake in 1948; it has not, however, been recorded for any of the other Skeena lakes (letter from Mr. V. H. McMahon of the Pacific Biological Station). The form is probably Mysis relicta, since this is the only fresh• water species known for North America (Ward and Whipple 1918). Specimens have been sent for identification to Dr. C. R. Shoemaker of the U. S. National Museum in Washington, D.C. Mysis relicta is the fresh-water form of Mysis ooulata, to -which it is identioal, though smaller. It has been the subject of considerable controversy on the basis of the theory that its origin in fresh-water lakes was as a glacial marine relict. It was believed that, particularly during the glacial periods, lakes once cut off from the sea, became fresh• water, but retained part of the original marine fauna which had been able to adapt to the new conditions. This theory does not seem to explain the facts of its distribution in North America. In North America Mysis oculata has been recorded for Labrador, Newfoundland, eastern Canada, and in the Canadian arctic. Besides the eastern lakes of Canada, Mysis reliota has been found in Lake Athabaska, Great Slave and Great Bear Lakes (Larkin 1948) and even as far south as the Waterton lakes. (Conversation with Dr. Larkin). The origin of Mysie relieta in Lakelse lake is probably marine, since that region was inundated by the ocean following the retreat of the last Pleistocene ice sheet (McConnel 1912). COMPETITORS FOR FOOD OF WHITEFISH. Introduction. Several species of fish feed on the young inseots and small molluscs which form the bulk of the food of nhitefishes. If the supply of suoh bottom organisms is limited, then competition will ensue unless seme speoies can turn easily to other food. Competition will be acute if the supply is seriously low and if the total numbers of all fish using a common diet is high. However, regardless of the absolute numbers of the various speoies concerned, a oommon diet cannot be defined as true com• petition if the supply is sufficient. Conditions of crowding, seasonal fluctuations, or any other factors which might reduce the abundanoe ©f the food supply, could very soon effect a state of urgent competition. To determine the extent of competition, then, certain major factors which first must be known are, (a) the abundanoe of food and its distribution (b) the variations in food abundance, (c) the absolute numbers of the different fish species concerned and their distribution, and (d) the amounts of food whioh the fish consume. Obviously such data can be determined only in relative terms, and decisions must rely finally on such observations as the oondition of the fish, reduotion of populations, both of consumers and of food, and so forth. Most lake investigations measure, what may be described as the potentialities for competition by competing fish, rather than the extent of competition existent. The prooedure followed is to assess the relative abundance of the various fish by gill-netting, and by stomach analyses to discover what foods are important, then relate these factors to the abundanoe of food as determined by dredging or by plankton hauls. /tf. This is the general description of the method employed here, and it has been extended by descriptions of the distributions of various fishes, since though the diets of two may be common, one may not normally inhabit the zone occupied by the other. Comparisons of the growth of the white- fish in Lakelse, Babine and Morrison lake have also been referred to. Bottom feeding fish oan be sampled well by gill-nets set along the lake bottom, but others, such as Rainbow and Cutthroat trout, no doubt pass above the net in deeper water. Where much of the lake is shallow, as in Lakelse, gill-netting is more successful with pelagic fish, than in lakes like Babine and in the deep northern two-thirds of Morrison lake. Certain fish are netted rarely; they either avoid the net or escape from it readily. The Ling, for example, with its soalelesB and slippery body is seldom gilled, and many more of these fish have been actually observed in Babine lake, than the netting data indicate. (Many have been seen, for example, each year in the shallow water near the migrant yearling Sockeye fence). Materials and Methods. The writer has analysed the stomach contents of 422 Squawfish, 501 Cutthroat trout and 41 Dolly Varden from Lakelse lake. Other data used include the stomach analyses of various species from Babine and Morrison lakes. These analyses were made by Mr. J. A. MoConnel of the Pacific Biologioal Station. To describe the depth distribution of some of the more important competitors, the original oatch records for 1946 and 1947 were used to determine the c.n.n. per depth of each species according to the method already described for the whitefishes. Where the total numbers of fish //f o caught were small, the weighted mean depth of capture, from two years' records has been determined. Some species are described as competitors on the basis of their food analyses alone; these are the rarely caught fish. Peamouth Chub. Stomach analyses of this fish from Babine and Morrison lakes are given in Tables ***- and"***'- • The depth distribution of Peamouth chub in Lakelse lake is demonstrated in Table xxx//, and Pig • In Babine lake the mean depth of capture (weighted) of 526 Chub netted in Division I in 1946 and 1947 was 2.2m. Less than 20 fish were caught in Division II (excluding Wright bay) in those two years. In Wright bay in 1947, all of the 97 Chub caught in several sets had been netted in depths of less than 3m. The weighted mean depth of capture of 50 fish netted in Morrison lake (1946 and 1947) was 3*9 m. In addition to the stomach analyses given in Tables *xx. and xxx/ the following is a summary of the analyses of 10 Lakelse speoimens: Molluscs - 68$ of total food volume Insecta - 9% " " " " Algae - 23$ " . " 6 fish had eaten molluscs, 4 insect material and 5 algae; 3 stomachs empty. Considering the food of this fish it is evident that its diet is very similar to that of both species of whitefish in each lake, with the exception of the Eastern whitefish in Morrison lake. The bulk of the food of the three fishes (again excepting the Eastern whitefish in Morrison lake) was made up of suoh bottom forms as young insects and small f*?o. TABLE *XX. STOMACH ANALYSES OF 31 PEAMOUTH CHUB CAUGHT BY GILL-NET. BABINE LAKE, 1946. June - August. No. of Stomachs Total No. Total V01. AT. NO. AT. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach# Stomach^ Volume C.Ir* cc. cc Insecta Trichoptera 11 149 2.55 4.80 .082 15.1 .90 (larra & case) Coleoptera 1 1 T 0.03 T T (adult) - Diptera 5 94 0.10 3.03 .003 0.5 .02 (larva & pupa) Remains 6 - 0.10 - .003 0.5 .02 Amphipoda 7 38 0.15 1.22 .005 0.9 .04 Cladocera 1 1 T 0.03 T T - Hydracarina 1 1 T 0.03 T T - Mollusca Gastropoda 19 ? 13.95 - .450 82.5 4.05 Bryozoa 1 1 0.10 0.03 .003 0.5 - No. of stomachs with food - 28 No. of stomachs empty - _3 (9.7$ of total) Total no. of stomachs - 31 # Total sample st Consumption Index SJSS. TABLE XKX». STOMACH ANALYSES OF 41 PEAMOUTH CHUB CAUGHT BY GILL-NET. MORRISON LAKE, 1947. July 2 - August 4. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach# Stomach Volume C.I.K c.c. c.c. Insecta Ephemerida 10 30 .46 .73 .011 8.59 .11 (nymph) Plecoptera 1 4 T .09 T T - (nymph) Trichoptera 16 71 1.54 1.77 .038 28.90 .61 (larva, pupa & case) Diptera 10 132 .10 3.22 .002 1.56 .02 (larva) Coleoptera 5 15 .20 .37 .005 3.91 .03 (adult) Hymenoptera 1 1 T .02 T T - (adult) Remains 8 -. .40 - .009 7.03 .07 Amphipoda Hyallela 2 13 .40 .32 .009 7.03 .02 Gammarus 1 4 T .09 T T — Cladocera Daphnia 1 20 T .49 T T - Hydrocarina 1 1 T .02 T T - Mollusca Gastropoda 13 32 2.10 .78 .051 39.84 .66 Plant 6 - .18 - .004 3.12 .02 No. of stomachs with food - 32 No. of stomachs empty - 9 Total no. of stomachs - 4T # Total sample x Consumption Index TABLE XXX// CATCH PEE NET-NIGHT OP PEAMOUTH CHUB IN NETS SET AT DIFFERENT DEPTHS IN LAKELSE LAKE. 1946 and 1947 DATA COMBINED DEPTHS METRES MESH 0 - S 3-6 6-9 9-12 12-15 15 - 18 18 - 21 21-24 CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS 1 27.1 43 11.8 5 23.0 19 14.5 2 12.5 4 -.02 2 4.6 44 .8 11 1.2 12 0 2 .5 4 0 2 3 o • 31 0 22 0 16 - 0 4 0 2 4 0 39 0 15 0 10 0 5 0 4 e 2 5 0 34 0 13 0 16 0 5 0 4 0 2 Total no. of fish - 1971 Total no. of sets (nets) - 374 NO. OF SETS. CUTTHROAT 4 5 SQUAWFISH 1 £ 4 Ul Q. I O < "O PEAMOUTH 20 10 ISx. 0 — 10 \ 10 — 20 20 — 30 30—40 40—50 50 — 60 60—70 DE PTH — H&W-E-S ^Fig. 16. Catch per net-night per mesh of Cutthroat trout, Squawfish and Peamouth chub at different depths in Lakelse lake. Data of 1946 and 1947 combined. /2u. molluscs. The high C.I.'s for the three fish in Babine lake were each for caddis worms and gastropods. In Lakelse lake mayfly nymphs were relatively more abundant, and constituted the most important single item of food for the Rocky Mountain whitefish. Referring to the distribution of the three species (Figs. S and for Rocky Mountain whitefish, Figs. *o and //- for Eastern whitefish, and Fig. /C and the data given above for Peamouth), it can be seen that the Peamouth chub and the Rooky Mountain whitefish occupied virtually the same zone of water wherever they co-existed, i.e. at greatest abundance within the 0 - 6 m. zone. In the case of the Eastern whitefish, its peak of numbers was in the deeper 10 - 15 m. zone, but there was considerable overlapping into the zone of the former two fish. The Peamouth chub was perhaps more dependent upon shallow waters than the Rocky Mountain white- fish. This was evidenced by a very low oatoh-per-net-night in Division II of Babine lake, whose shores slope down more rapidly than in Division I, and where the catch of Rocky Mountain whitefish was higher than in Division I where Peamouth were more plentiful. In Morrison lake there are few Peamouth ohub, and even smaller numbers of Rocky Mountain whitefish. In this lake, the relatively abundant Eastern whitefish exists on a diet (summer) of approximately 90 per cent plankton Crustacea. Evidence already given has indicated that there are few bottom organisms in Morrison lake. The Morrison lake Peamouth chub and Rooky Mountain whitefish have so far shown no evidence of changing their food habits. These conditions describe an assumed state of high abundance (i.e. summer conditions), thus there seems little doubt that in Morrison lake these speoies are active rather than merely potential com• petitors for food. This is the only evidence which indicates a possible /2r explanation for the small numbers of these fish in the lake (i.e. Rooky- Mountain whitefish and Peamouth chub), and for the fact that the Eastern whitefish has radically changed its feeding habits* Squawfish. In Tables xxt.ni. to x*xv/. the stomaoh analyses of Squawfish from Lakelse, Babine and Morrison lakes have been summarized and tabulated* Table xxxv//. and Fig. /(> indicates the catch/depth relationship of this fish in Lakelse lake. In Babine lake the weighted mean depth of capture of 50 Squawfish netted in Division I in 1946 and 1947 was 2.3 m. Ho Squawfish were netted in Division II in 1946, and only 4 (mean depth 5.4 m.) in 1947 (Wright bay exoepted). In Wright bay in 1947, 41 Squaw• fish were netted at a mean depth of approximately 2 m. In Morrison lake 83 Squawfish were netted in 1946 and 1947 at a mean (weighted) depth of 3.4 m. The Squawfish is essentially a carnivorous fish, since the bulk of its diet is made up of fish and occasional lampreys and frogs. Bottom organisms suoh as insect larvae, and occasionally molluscs, are neverthe• less important, becoming more so no doubt whenever movements or migrations of small fish remove them (the small fish) vrom the range of the Squawfish's feeding. Sinoe the distribution of Squawfish is confined to depths similar to that of the whitefish, particularly the Rooky Mountain white- fish, they do compete with the whitefish to some extent. In Lakelse lake, where they are relatively abundant, such competition against the Rooky Mountain whitefish is probably acute, in that it supplements that of the Peamouth, and other species. Squawfish are not as numerous in Babine lake, but are quite abundant in Morrison lake. In these lakes, therefore, and TABLE XX xfr/f. STOMACH ANALYSES OF 202 SQUAWFISH CAUGHT BY GILL-NET IN LAKELSE LAKE. APRIL - AUGUST, 1945. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per t % Organism Stomachs Stomachs Stoma ch# Stomach^ Volume C.I. c. c.c. Insecta Ephemerida 7 85 3.80 .421 .019 2.16 .133 (nymph) Trichoptera 4 8 2.50 .040 .012 1.36 .048 (larva & case) Diptera 2 1 T .005 T T (adult) Coleoptera 2 .10 T T .002 (adult) Hymenoptera 1 .40 .002 .23 (adult) Remains 3.55 .018 2.04 Mollusoa Gastropoda 2 4.10 .025 .020 2.27 .040 Remains 1 .20 T .001 .11 .001 Fish Sockeye 7 22 25.80 .109 .128 14.55 .896 Salmonidae 11 16 12.80 .079 .063 7.16 .693 Stickleback 37 53 27.49 .262 .136 15.45 5.032 Cottidae 6 7 47.00 .035 .233 26.48 1.398 Peamouth Chub 1 1 29.00 .005 .144 16.36 .144 Remains 21 16 7.50 .079 .037 4.20 .777 Eggs 6 - 6.50 .032 3.64 .192 Cyclostomata Lamprey 10 9 4.65 .045 .023 2.61 .230 Miscellaneous - 1.25 .006 .68 Plant remains 6 1.20 .006 .68 .036 No. of Stomachs containing food - 133 No. of Stomachs empty - 69 # Total sample Total No. of Stomachs 202 x Consumption Index /*7- TABLE xxx/y. STOMACH ANALYSES OF 209 SQUAWFISH CAUGHT BY GILL-NET. LAKELSE LAKE, (Standard & Experimental) 1947. May 11 - September 24. No. of Stomachs Total No. Total Vol. AT. No. AT. Vol. with in all in all per per % Organisms Stbmachs Stomachs stomach# Stomach# Volume C.I.x cc. cc. Insecta Ephemerida 10 11 1.08 .053 .005 1.99 .05 (nymph) Odonata 1 3 .10 .014 T .18 • ~ • • (adult) Plecoptera 3 5 .87 .024 .004 1.60 .01 (nymph) Trichoptera 8 18 2.80 .086 .013 5.16 .10 (larra & case ). Hemiptera 2 250 4.20 - .020 7.74 .04 (larval) Coleoptera 2 2 .07 .010 T .13 — (adult) Remains (37) 3.28 - .016 6.04 .59 Cyclostomata Lamprey 3 2 3.02 .010 .014 5.56 .04 Fish Sockeye 5 11 10.30 .053 .049 18.97 .25 Salmonidae 8 8 3.86 .038 .018 7.12 .14 Peamouth 1 1 5.20 .005 .025 9.58 .03 Stickleback 12 12 5.37 .057 .026 9.89 .31 Remains 48 - 10.57 - .051 19.47 2.45 Eggs 7 - 1.90 .009 3.50 .06 Plant 9 1.50 .007 2.76 .06 Miscellaneous 1 .18 .001 .33 - No. of Stomachs containing food - 135 No. of Stomachs empty - _74 (35.4$ of Total) Total no. of Stomachs - 209 # Total sample x Consumption Index TABLE X* KV STOMACH ANALYSES OF 14 SQUAWFISH CAUGHT BY GILL-NET. BABINE LAKE, 1946. July - August. No. of Stomachs Total No. Total Vol. AT. NO. AT. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach# Volume cc. cc. Insecta Trichoptera (larra) 1 5 .2 .36 .01 2.5 Trichoptera (case) 1 3 .4 .21 .03 7.5 Remains 3 1.95 .14 35.0 Fish Remains .14 .07 17.5 1.0 Mollusca Gastropoda .36 .13 32.5 1.8 Amphipoda Hyalella 1 T .07 T T Plant 1 .3 .02 5.0 No. of stomachs with food - 4 No. of stomachs empty 10 (71.4$ of total) Total no. of stomachs 14 # Total sample TABLE XXXV/. STOMACH ANALYSES OP 45 SQUAWFISH CAUGHT BY GILL-NET. MORRISON LAKE, 1947. July 2 - August 4. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomachy Volume C.I.K c.c. Insecta Ephemerida 6 18 .60 .40 .013 2.57 .08 (nymph) Trichoptera 18 112 4.20 2.49 .093 18.38 1.67 (larva & case ) Coleoptera 1 1 T .02 T ' T • - (adult) .Diptera 2 4 .05 .08 .001 .20 - (larva & pupa ) Remains 9 - .80 - .018 3.56 .16 Amphipoda 1 1 T .02 T T - Mollusca Gastropoda 5 7 2.6 .15 .058 11.46 .29 Pish Salmonidae or Coregonidae 1 1 T .02 T T - Cyprinidae 2 2 .85 .04 .019 3.75 .04 Cottidae 4 4 3.55 .08 .079 15.61 .32 Remains 3 3 .25 .06 .005 .99 .02 Bryozoa Statoblasts 1 - .05 .22 .001 .20 - ; Plant 3 - .20 - .004 .79 .01 Amphibia Prog 1 1 9.70 .02 .215 42.49 .22 No. of stomachs with food - 42 No. of stomachs empty - __3 (6.6$ of total) Total No. of stomachs 45 # Total sample sc Consumption Index TABLE XXXY/A CATCH PER NET-NIGHT OP SQUAWPISH IN NETS SET AT DIFFERENT DEPTHS IN LAKELSE LAKE. 1946 and 1947 DATA COMBINED DEPTHS - METRES MESH 0 - 3 3 - 6 6 - 9 9 - 12 12 - 15 15 - 18 18 - 21 21 - 24 CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SET! #1 6.3 43 1.2 5 3.1 19 4.5 2 2.0 4 0 2 2 1.9 44 .6 11 1.4 12 1.5 2 .5 4 0 2 3 .2 31 .1 22 .1 16 - 0 4 - 0 2 4 0 39 .1 15 0 10 0 5. 0 4 Mi 0 2 6 0 34 0 13 0 16 0 5 0 4 _ 0 2 Total no. of fish - 442 Total no. of sets (nets) 374 /jr. particularly in Morrison since bottom organisms are generally very scarce, the Squawfish probably effeots a removal of whitefish food as important as in Lakelse. Cutthroat Trout. The o.n.n. of Cutthroat trout at different depths in Lakelse lake is given in Table XLIV. and Pig. • Mention has already been made that the gill-net will hardly sample pelagic fish in deep waters since they pass above the net. Thus in Babine lake, though sportsmen could catch these and other trout or char by troll or fly in deep water, they were never netted in such depths. For these reasons the netting analyses for Babine and Morrison lakes have not been pursued further. The food of Cutthroat trout is given in Tables xxx*//*. to xx.///. The trout is frequently piscivorous, but insect material also forms an important part of the diet, and constituted almost 40 per cent of the food (by volume) for the Lakelse fish, and possibly somewhat more than this in Babine lake. Among the Inseota the important C.I.'s for the Lakelse samples were as follows: 1946 1947 1948 (angled) Coleoptera (mostly adult) 13.6 22.0 3.9 Ephemerida (mostly nymphs) 7.3 7.5 .1 Triohoptera (caddis worms and cases) 1.5 1.9 .3 Plecoptera (larva & adult) trace 4.3 .0 Odonata (larva) .3 .1 .1 In Lakelse lake, then, although the Cutthroat trout consumed large numbers of insects, their diet differed markedly from that of the Lakelse Rooky Mountain whitefish in terms of the speoies of insects taken. The adult Coleoptera were definitely the most important insect form taken by /3Z. TABLE Xxxv//' STOMACH ANALYSES OF 141 CUTTHROAT CAUGHT BY GILL-NET. LAKELSE LAKE, 1945. April 16 - September 3. No. of Stomachs Total No. Total Vol. AT. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach# Volume C.I.x c.c. c.c. Porifera 1 - .20 - T T - Insecta Ephemerida 28 973 36.87 6.90 .26 14.2 7.28 ( nymph) Odanata 13 16 3.08 .11 .02 1.1 .26 (nymph) Plecoptera 3 10 .10 .07 T T - (adult) v Triohoptera 22 77 9.27 .55 .07 3.8 1.54 (larva & case) Hemiptera 5 4 .23 .03 T T - (adult) Diptera 4 8 .50 .06 T T - Coleoptera 45 1000 41.90 7.09 .30 16.3 13.50 (adult) Hymenoptera 18 79 6.35 .56 .04 2.2 .72 (adult) Remains - - 6.50 - .05 2.7 - Arachnida 4 4 .20 .03 .03 T - Crustacea A Amphipoda 2 — T - T T - Phyllopoda 1 3 .20 .20 T T Mysis 5 92 1.80 .65 .01 .5 - .05 Mollusca Gastropoda 1 2 .05 .01 T T - Fish Sockeye Salmonl5 51 46.13 .36 .33 17.9 4.95 Pink Salmon 1 25 4.20 .18 .03 1.6 .03 Salmonidae 3 15 4.50 .11 .03 1.6 .09 Stickleback 54 283 81.72 2.01 .58 31.5 31.32 Cottids 1 1 9.50 .01 .07 3.8 .07 Remains 9 10 3.60 .07 • .03 1.6 .27 Plant Remains 7 - 3.45 - .02 1.1 .14 Miscellaneous 1 - .60 - T T - No. of stomachs with food - 131. No. of stomachs empty 10 (7.09% of total) Total No. of stomachs - 141. # Total sample Consumption Index. S3 3- TABLE xxx/X. STOMACH ANALYSES OF 276 CUTTHROAT CAUGHT BY GILL-NET. LAKELSE LAKE, 1947. (Standard & Experimental) May 11th to September 23rd. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach# Volume C.I. x cc. cc Porifera 4 - 2.92 - .oil .699 Hirudinea 1 1 .30 .004 .001 .072 Insecta Ephemerida 55 839 37.67 3.040 .136 9.013 7.48 (nymph) Odonata 12 20 1.07 .072 .004 .256 .05 (nymph) Plecoptera 36 286 32.47 1.036 .'118 7.769 4.25 (nymph & adult) Triohoptera 34 99 15.53 .359 .056 3.716 1.90 (larva ft case) Hemiptera 1 2 .05 .007 T .012 - (adult) Diptera 13 96 4.22 .348 .015 1.010 .20 (adult mostly) Coleoptera 110 1373 55.18 4.975 .200 13.203 22.00 (adult mostly) Hymenoptera 20 176 11.84 .638 .043 2.832 .86 (adult) Neuroptera 4 180 3.10 .652 .011 .742 .04 (adult) Lepidoptera 1 1 .30 .004 .001 .072 .00 . (larva) Remains - - 19.59 - .071 4.687 Arachnida 1 2 .02 .007 T .005 Crustacea Amphipoda 1 1 T .004 T T Mysis - 44 1.19 .159 .004 .285 Fish Sockeye 35 154 75.38 .558 .273 18.036 9.56 Cutthroat 1 3 20.00 .011 .072 4.785 .07 Salmonidae 6 7 12.75 .025 .046 3.051 .28 Stickleback 66 349 102.07 1.264 .370 24.422 24.42 Cottids 1 1 5.00 .004 .018 1.196 .02 Remains 36 - 10.67 - .039 2.552 1.40 Plant 17 - 6.52 - .024 1.560 .41 Miscellaneous - - .10 - T .024 - tnph 13 (4.71$ of totaBt)mpty. # Total sample, x Consumption Index. Sit- TABLE XA. STOMACH ANALYSES OF 15 CUTTHROAT CAUGHT BY SEINE OR HOOK AND LINE. LAKELSE RIVER, 1945. April - September. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach# Stomach# Volume Insecta Ephemerida 1 50 2.60 3.33 .173 19.1 Odonata 3 3 .15 .20 .010 1.1 Plecoptera 2 2 .22 .13 .015 1.7 Trichoptera 2 18 1.00 1.20 .067 . 7.4 Diptera 1 3 .10 .20 .007 • .8 Coleoptera 5 lo3 2.67 6.87 .178 19.6 Hymenoptera 2 6 . .05 .40 .003 .3 Remains - - .44 - .029 3.2 Arachnida 1 1 .05 .07 .003 .3 Fish Sockeye 1 1 2.60 .07 .173 19.1 3-spined stickle- 2 2 2.00 .13 .133 14.6 back Remains 1 1 .30 .07 .020 2.2 Plant - Remains 3 - 1.44 - .096 10.6 No. of stomachs containing food - 12 No. of stomachs empty - _3 (20$ of total) Total no. of stomachs 15 # Total sample TABLE STOMACH ANALYSES OF 69 CUTTHROAT CAUGHT BY ANGLING. LAKELSE LAKE, 1948. May to Early June. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % • Volume Organisms Stomachs Stomach6 StomacWf Stomach^ C.I. K cc. cc. Insecta Ephemerida 7 21 .80 .30 .012 1.31 .08 (nymph) Coleoptera 21 219 12.80 3.17 .186 21.02 3.91 (adult) Odonata 6 10 .55 .14 .008 .90 .05 (larva) Trichoptera 8 19 2.45 .28 .036 4.02 .29 (larva & case) Hemiptera 2 • 16 .39 .23 .006 .64 • .01 (adult) Plecoptera 1 1 .10 .01 .001 .16 .00 (nymph) Diptera 1 6 .20 .09 .003 .33 .00 (adult) Remains 3.05 .044 5.01 Mollusca Gastropoda 1 20 2.00 .28 .029 3.28 .03 Crustacea Amphipoda 1 2 .02 .03 T .03 - Fish Sockeye 1 2 1.20 .03 .017 1.97." .02 Salmonidae 2 5 3.88 .07 .056 6.37 .11 Cyprinidae 1 1 3.70 .01 .054 6.08 .05 Stickleback 13 35 15.75 .51 .228 25.86 2.96 Remains 5 5 12.55 .07 .182 20.61 .91 Plant 6 1.35 .020 2.22 .12 Miscellaneous 1 .10 .001 .16 .00 No. of stomachs containing food - 54 No. of stomachs empty « 15 (21.7% of total) Total no. of stomachs - 6"9~ # Total sample x Consumption Index Jtjt. TABLE STOMACH ANALYSES OF 14 CUTTHROAT TROUT CAUGHT BY GILL-NET. BABINE LAKE, 1946. June - August. No. of Stomachs Total No. Total Vol. AT. NO. AT. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach^ Volume c.c. c.c. Insecta Ephemerida 6 38 3.0 2.7 .21 4.0 (nymph) Trichoptera 7 48 6.1 3.4 .43 8.4 (larvae) Coleoptera 9 80 1.8 .6 .13 2.5 (adult mostly) Hemiptera 2 7 .2 .5 .01 0.2 Lepidoptera 2 3 .4 .2 .03 . 0.6 Orthoptera 1 3 1.5 .2 .11 2.1 Hymenoptera 5 144 12.9 10M .92 17.9 Diptera 2 9 .1 .6 .00 T (larva & pupa) Remains 7 8.6 _ .61 11.9 Nymphal cases 3 2.5 .4 .18 3.5 (Ephemerida) Fish Peamouth (?) 1 1 21.0 .1 1.50 29.2 Lake Shiner 1 10 5.0 .7 .36 7.1 Sucker 1 2 9.0 .1 .64 12.6 Amphipoda Hyalella 1 .1 No. of stomachs with food - 14 No. of stomachs empty 0 (0 % of total) Total no. of stomachs - T¥ # Total sample TABLE X^///. STOMACH ANALYSES OF 3 CUTTHROAT TROUT CAUGHT BY GILL-NET. MORRISON LAKE, 1947. July. N o. of Stomachs Total No. Total Vol. Av. No. Av. V01. with in all in all per per % Organisms Stomachs Stomachs Stomach# Stomachjf Volume Insecta Trichoptera 1 T 0.33 T T (pupa) Coleoptera 3 0.1 1.00 (adult) .03 33.3 Fish Remains 0.2 0.33 .06 66.6 :No. of stomachs with food - 2 No. of stomachs empty - 1 (33.3$ of total) Total no. of stomachs # Total sample AC• TABLE XA/Y. CATCH PER NET-NIGHT OF CUTTHROAT TROUT IN NETS SET AT DIFFERENT DEPTHS IN LAKELSE LAKE. 1946 and 1947 DATA COMBINED DEPTHS - METRES BSH 0-3 3 - 6 6 - 9 9 - 12 12 - 15 15 - 18 18 - 21 21 - 24 CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS CNN SETS 1 1.8 43 .6 5 .2 19 0 2 0 4 - - 0 2 2 4.3 44 .1.3 11 1.7 12 1.0 2 .5 4 - - 0 2 3 1.3 31 .4 22 .6 16 0 4 - - 0 2 4 .1 39 .1 15 .1 10 .2 5 0 4 - - 0 2 5 .1 34 0 13 .2 16 0 5 0 4 _ 0 2 Total no. of fish - 370 Total no. of sets (nets) 374 the trout, while the whitefish fed mostly on mayfly nymphs, caddis worms and pelecypods in that order. Coleoptera were recorded as little more than traces in all the whitefish stomachs examined, and the Plecoptera were wholly absent. Ephemerida, on the other hand were important to both fish. In Lakelse lake the ephemerid nymphs provided the highest C.I. for whitefish, and the next but highest for the Cutthroat trout. As the tables indicate, smaller amounts of other insects were also common to the diets of both fish. Molluscs, particularly the Peleoypoda, were important as food for whitefish in Lakelse, but among the 5p0 odd Cutthroat stomachs examined, only two had small traces of these organisms. Less can be said on the matter for Babine and Morrison fish except that the figures do indicate conditions similar to those in Lakelse. The netting data of the trout in Lakelse lake indicate that the Cutthroat trout of all sizes were most abundant in the shallow waters of the 0 - 10 m. zone. Intermediate sized fish possibly extended out to deeper water than the smallest or largest fish. Thus these fish probably also share a depth habitat in common with the Rocky Mountain whitefish and Peamouth chub, though it is most likely that the trout move out into deeper waters, nearer the surface and well above the depths of sunken nets. The fact that an important item of their diet was the yearling Sockeye salmon, which is definitely pelagic during its lacustrine existence, supports this statement. Considering, finally the fact that the bottom organisms were decidedly fewer throughout depths greater than 5 m., the Cutthroat trout were doubtless active competitors for a considerable portion of the food of whitefish. Dolly Varden Char. This char is not present in Babine or Morrison lakes* Only small numbers have been taken in Lakelse lake. Stomach analyses of specimens caught by gill-net, angled, and taken from the yearling Sockeye trap are summarized in Tables XLV. to Xi.w// These fish took relatively very small amounts of insect material or any other organisms which enter the diet of the Rocky Mountain whitefish. Their food was made up almost entirely of other fishes, particularly the small oottids. Northern and Common Suckers. Very few Common suckers have been netted in Division I of Babine lake (25 in two years), and no Northern suokers. In Division II, 63 Northern and 14 Common suckers were netted in 1946 and 1947. The mean depth at which the Northern suckers were netted was between 3 and 4m.; and that for the Common sucker somewhat less than this. In Lakelse lake only 51 suckers were netted in 1946 and 1947. In the same years only 8 suckers were caught in Morrison lake. The few stomach analyses made were of 3 Common suckers and 6 Northern suokers from Babine, (Tables XA/X and xz.. ); and 4 Northern suckers from Morrison lake, (Table )• The bulk of the food of both species was made up of larval insects and was supplemented by molluscs and plankton Crustacea. Though the diets were similar to those of the whitefish, these fish are of little importance as competitors in Lakelse or Morrison lakes because of their small numbers. They appear to be more abundant than the Eastern whitefish and only slightly less numerous than the Rocky Mountain whitefish in Division II of Babine lake. They were netted very infrequently ////• TABLE X*~V STOMACH ANALYSES OF 7 DOLLY VARDEN CAUGHT BY GILL-NET. LAKELSE LAKE, 1945. April 22 - April 24. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach# Volume Insecta Trichoptera .29 Fish Salmonidae 2 2.30 .29 .33 20.00 Remains 2 9.00 .29 1.29 78.18 Plant Remains .18 .03 1.82 No. of stomachs containing food - 4 No. of stomachs empty - 3 (42.86$ of total) Total no. of stomachs # Total sample TABLE XJLV/, STOMACH ANALYSES OF 9 DOLLY VARDEN CAUGHT BY ANGLING. LAKELSE LAKE, 1948 No. of Stomachs Total No. Total Volume with in all in all Organisms Stomachs Stomachs cc, Insecta Coleoptera .15 Fish Sockeye 1 1 2.00 Cottid 2 2 27.10 Sucker 1 1 48.00 Remains 2 2 .65 No. of stomachs containing food - 7 No. of stomachs empty - 2 Total No. of stomachs - 9 TABLE X^WA STOMACH ANALYSES OP 12 DOLLY VARDEN CAUGHT IN THE YEARLING (SOCKEYE) MARKING TRAP. LAKELSE LAKE, 1947 No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomachif Stomach^ Volume Insecta Odonata 1 5 .40 .42 .033 .71 Trichoptera 1 1 .20 .08 .017 .35 Remains Fish Cottids 1 1 56.00 .08 4.67 98.85 No. of stomachs containing food - 3 No. of stomachs empty - 9 (75$ of total) Total no. of stomachs 12 # Total sample TABLE XAV///: STOMACH ANALYSES OF 13 DOLLY VARDEN CAUGHT BY GILL-NET, LAKELSE LAKE, 1947, (Standard & Experimental) No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all , in all per per % Organisms Stomachs Stomachs Stomach^ Stomach# Volume Insecta Coleoptera 1 1 .02 .08 .001 .28 Trichoptera 2 3 .25 .23 .019 3.56 Fish Sockeye 1 2 .55 .15 .042 7.82 Coho 1 1 6.00 .08 .461 85.47 Plant .20 .154 2.85 No. of stomachs with food - 5 No. of stomachs empty 8 (61.5$ of total) Total No. of stomachs 13 W Total sample TABLE M'.X. • STOMACH ANALYSES OF 3 COMMON SUCKERS CAUGHT BY GliL-NET. BABINE LAKE, 1946. No. of Stomachs Total No, Total Volume with in all in all Organisms Stomachs Stomachs Insecta Ephemerida 2 16 5.3 (nymph) Trichoptera 2 22 7.3 (larva & case) Diptera 3 Large numbers Large numbers (larva & pupa) Amphipoda Gammarus 1 2 .6 Hyalella 3 65 21.6 Hydracarina 1 1.0 Mollusoa Gastropoda 2 6 2.0 Pelecypoda 2 7 2.3 Cladocera Bosmina 1 Also present were: •various diatoms, Diatoma, Synedra, Tabellaria 2 species of filamentous algae the protozoan, Vorticella and other microscopisl forms No. of Stomachs with food - 3 No. of Stomachs empty - £ Total no. of Stomachs - 3 TABLE STOMACH ANALYSES OF 6 NORTHERN SUCKERS CAUGHT BY GILL-NET. BABINE LAKE, 1946. No. of Stomachs Total No. Total Volume with in all in all Organisms Stomachs Stomachs Insecta Ephemerida 2 ,16 2.6 (nymph) Trichoptera 4 60 10.0 (larva & case) Coleoptera 2 2 0.3 (adult) Diptera 4 51 8.5 (larva & pupa) Amphipoda Hyalella 3 84 14.0 Sp. 1 5 0.8 Ostracoda 2 10 1.6 Hydracarina 2 f ? Mollusca Gastropoda 2 6 1.0 Pelecypoda 1 1 0.2 Copepoda Cyclops 1 Cladocera Bosmina 2 Plant 2 No. of stomachs with food - 5 No. of stomachs empty - 1 (17. % of total) Total no. of stomachs - 6 /*7 TABLE LI. STOMACH ANALYSES OF 4 NORTHERN SUCKERS CAUGHT BY GILL-NET IN MORRISON LAKE, AUGUST, 1947. No. of Stomachs with Relative Organisms abundance Insecta Diptera Large numbers (larva) Cladocera Daphnia 1 Trace Bosmina 1 Trace Copepoda Cyclops Trace Astracoda Sp. Small number Mollusca Pelecypoda 1 Small number Remains 2 Trace Plant Medium amount None empty. in Division I. In Division II, then, they may actively compete with the whitefish, particularly the Rocky Mountain whitefish, Clemens (1939) states that the Northern sucker in Okanagan lake was netted only in deeper water (30 m. and 60 m.), while the Common sucker was not netted at depths greater than 15 m. In Okanagan lake the Northern suoker is apparently "an associate of the Eastern whitefish when the two species occur in the same body of water", (Clemens, loc. sit). This is not the case in Babine lake, apparently, since only one fish was netted at a depth exceeding 10 m,, and in view of the fact that the greatest catches of Eastern whitefish were in Division I, where no Northern suckers have been netted. Summary, Peamouth chub are the important competitors for the food of both whitefish in Lakelse and Babine lakes, Stomaoh analyses showed that the diets of the three fish were very similar. The chub are particularly numerous in Lakelse lake. The maximum occurrence of both the chub and the Rocky Mountain whitefish was in the 0 - 5 m. zones; and the range of both species considerably overlapped that of the Eastern whitefish in deeper water. Competition for the few bottom organisms in Morrison lake has probably contributed to the restriction of Rocky Mountain whitefish in that lake to its very small numbers. This condition may also have been responsible in part for the habit of the Eastern whitefish in that lake of feeding almost exclusively on plankton Crustacea. Though the Squawfish were found to be essentially carnivorous, they fed frequently on food similar to that of the whitefishes, and inhabited approximately the same tones as the Rocky Mountain whitefish and the Peamouth Chub. The Squawfish, also, is very abundant in Lakelse lake. Cutthroat trout were frequently piscivorous and consumed many terrestrial insects. However, bottom organisms suoh as young aquatic insects were also important particularly in Lakelse lake. They are pro• bably active competitors in Lakelse lake where they are very numerous, and where they tend to come in to shallow water more frequently than they do in Babine and Morrison lakes. Dolly Varden char, which are not present in Babine and Morrison lakes, are seldom numerous and feed mostly on other fish. The Northern and Common suckers were considered to be of little im• portance as competitors in Lakelse and Morrison lakes because of their small numbers* The food of these two fish is similar to that of both whitefish, and they are probably of some importance as competitors in Babine lake* • • • • ooo •..• PREDATION ON EASTERN AND ROCKY MOUNTAIN WHITEFISH. Introduction. Piscivorous fishes of the Skeena lakes are Cutthroat trout. Rainbow trout, Dolly Varden char, Lake trout (char), Squawfish, Burbot and Sculpin, In Babine and Morrison lakes the Lake trout. Rainbow trout, Cutthroat trout, Squawfish and Burbot are each present, though their habitats are not necessarily in common, ^n Lakelse and the other more coastal and southerly lakes there are no Burbot or Lake trout, but varying numbers of each of the other species. There are no Squawfish, Cutthroat trout or Lake trout in the northern lakes (lakes north of and including Swan lake), with the exoeption of Bear lake in whioh the Lake trout is present. In these same northern lakes, and including also Kitwanga and Kistumgallum lakes, the Rainbow trout appears to replace the Cutthroat trout. The small Sculpin probably occurs in all the lakes. The extent of predation on either of the whitefish is judged by the amounts of these fish which appear in the stomachs of the predators, and by the numbers of such predators whioh are present in any lake. In only a few oases is it possible to indicate the abundanoe of any of the various species, and this is done by comparing the c.n.n. figures of different lakes. Frequently the condition of the stomach contents has prevented the identification of fish remains beyond sub-order or family. Although some quantitative data are provided here, this study rather limits itself to recording those fish which are known to prey on either of the two whitefishes. In a study of predation on young Sockeye salmon in Skeena lakes (Withler 1946) has made use of a Predation Index* This is defined as the product of the o.n.n. and the average volume of prey (either all fish or Sookeye). The Predation Index is subject to the following limitations, l) the c.n.n. is unreliable for a poorly sampled lake, 2) the c.n.n. (and therefore the Predation Index) is probably not comparable "for speoies widely divergent in morhholigical or behaviour characters" (Withler, loc sit.) suoh as Squawfish and Cutthroat trout for example, 3) the smaller the catch, the less reliable are the stomach analyses. Since all these data accrue from summer observations it is obvious that some of the most important considerations of predation may be missed. In particular it ' has not been possible to obtain any looal evidence of predation on the eggs or emergent fry of both whitefishes. Withler's figures, as they apply to an "all fish" diet of several predatory species in different Skeena lakes, are presented in Table This table indicates the relative "aotivity" of different predators in £he various lakes. It is possible to direct the examination more in• timately towards the whitefishes, since the writer has recently examined the stomach contents of large numbers of Cutthroat trout and Squawfish, and a number of stomaohs of Dolly Varden char and Rainbow trout, and has also re-examined the earlier analyses for specific data on the predation on whitefish. Cutthroat Trout. (Tables XXMH/ /fe x*.///,). No Rooky Mountain whitefish were specifically identified in any of the stomach samples of Cutthroat trout from Lakelse lake. Stiokleback, TABLE V.U. PREDATIOH INDICES FOB PREDATOR SPBCIES OF FISH TAKEN BY STANDARD NETTING IN TEN SKEENA LAKES. VALUES ARE FOR AN "ALL FISH" DIET. (ADAPTED FROM TABLE IV, WITHLER, 1949) LAKE YEAR LAKE TROUT DOLLY VARDEN SQUAWFISH TROUT BURBOT LAKELSE 1946 - 0.31 0.54 0.90 - BABINE. DIV. I 1946 0.37 - 0.01 0.00 0.01 BABINE. DIV. II 1946 1.12 - 0.00 0.06 0.01 BABINE. DIV. III1946 0.05 - 0.00 0.01 0.00 MORRISON 1947 3.98 - 0.01 0.10 1.53 NILKITKWA 1947 1.75 - 0.01 0.21 0.00 STEPHENS 1945 - 2.20 - 0.00 - SWAN 1945 - 1.34 - 0.35 - KITWANGA 1946 - 0.14 0.60 0.19 - ALASTAIR 1947 - 0.00 - 1.88 MORICE 1945 3.15 0.43 - 0.04 - BEAR 1947 0.64 0.00 0.00 0.00 young salmon and trout, and oottids made up virtually almost all of the fish diet. It will be noticed that unidentified "Remains" constitute only a small volume, so that if whitefish were included within this oategory they were unimportant. These samples indicate only summer conditions. In the small samples from Babine and Morrison lakes, no whitefish remains were identified. Squawfish. (Tables XXXI.I Y° wi). In Lakelse lake Squawfish are known to prey on whitefish since there is at least one record of a gilled Squawfish having a half-ingested white- fish in its mouth. However, stomach analyses show no indication of any extensive predation, for no whitefish remains were so identified. The important fish foods were Stickleback, young salmon and trout. Stomaohs of gilled Squawfish were usually quite difficult to analyse, sinoe the contents were almost always considerably disintegrated into small particles thoroughly mixed with the digestive mucous. The writer noticed that stomaoh contents of angled Squawfish were always more complete and less digested, and suggests that the Squawfish probably lives longer after being gilled than do such fish as trout or kokanee. The effect is possibly due in part to differences in shapes of head and opercula. The analyses of Babine and Morrison samples did not indicate any active predation. Predation Indices for this fish indicated a particularly high activity in Lakelse and Kitwanga lakes. This value, it will be recalled, is en• hanced by the relative abundance of the species in any lake. Dolly Varden Char. (Tables x^v hoxkvm). All fish remains were identified to speoies in the Lakelse samples* None were of the Rooky Mountain whitefish. Ho other samples have been analysed. This char is not present in Babine or Morrison lakes* Lake Trout. (Tables , n v ). Twenty-three stomachs from Morrison lake were analysed, and 53 from all divisions of Babine lake. (These analyses were made by Mr. J. A. MoConnell of the Pacific Biological Station). This char is not present in Lakelse lake. The Lake trout is particularly predaoeous. From the 53 Babine samples, 1 Rocky Mountain whitefish and 1 Eastern whitefish were identified in two stomachs. In addition 4 other fish had eaten what could only be identi• fied with surety as either 7 "Coregonldae or Salmonidae (but not Onoor- hynchus)". In Morrison lake (sample of 23 stomachs) 9 Eastern and 1 Rooky Mountain whitefish had been taken by 4 fish, and 1 fish had taken either "Salmonidae or Coregonidae". In this oase definite Eastern white- fish remains constituted more than 50$ (by volume) of the food taken by the 23 fish. Without doubt the Lake trout, in accordance with its numbers, and with the abundanoe of whitefish, is an active predator of these fish. The high Predation Indices for this fish were for Morrison, Morice, Nilkitkwa and Babine lakes, in that order. Rainbow Trout. Only 6 stomachs were analysed and these from Morrison lake. Three whitefish had been taken by 1 trout. TABLE UM- STOMACH ANALYSES OF 53 LAKE TROUT CAUGHT BY GILL-NET IN BABINE LAKE, 1946. June - August. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach^ Volume C.I. Insecta Ephemerida 7 15 .35 .28 .006 .1 .04 ( nymph) Trichoptera 3 35 1.90 .66 .036 .7 .11 (larva & pupa) Coleoptera 2 2 .08 .04 .001 .02 - (adult) Lepidoptera 1 1 .20 .02 .004 .08 - (adult) Diptera 14 49 .50 .94 .009 .2 .13 (larva & pupa) Diptera 2 3 T .06 T T - (adult) Remains 3 T - T T — Fish Sockeye 2 3 1.70 .06 .032 .7 .06 (fry) Kokanee 1 1 105.00 .02 1.980 40.6 1.98 (adult) Coho 1 2 6.80 .04 .128 2.7 .13 (fry) Salmonidae 5 4 1.10 .08 .021 .4 .11 Coregonidae or Salmonidae 4 7 12.00 .13 .226 4.6 .90 Coregonidae 2 2 29.60 .04 .558 11.4 1.12 Burbot 1 1 33.00 .02 .623 12.8 .62 Cottidae 2 2 14.70 .04 .277 5.7 .55 Remains 12 12 46.95 .23 .886 18.2 10.63 Amphipoda Gammarus 1 1 .05 ' .02 T T Copepoda Heterocope 6 - .60 — .011 .2 .07 Porifera 4 - 2.50 - .047 .9 .19 Plant remains 3 — * 1.70 .032 .7 .10 No. of stomachs with food - 32 No. of stomachs empty - 21 (40$ of total) Total no. of stomachs 53 # Total sample. x Consumption Index TABLE UV.' STOMACH ANALYSES OF 23 LAKE TROUT CAUGHT BY GILL-NET IN MORRISON LAKE, 1947. July - August. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach^ Volume C.I. x Insecta Ephemerida 1 2 0.1 .09 L .004 .04 (nymph) - Diptera 2 11 T .48 T T (larva & pupa ) - Remains 3 4 0.1 .18 .004 .04 .01 Fish Kokanee 2 2 82.0 .09 3.560 33.43 7.12 Coregonidae 4 10 129.5 .43 5.630 52.87 22.52 Salmonidae or 1 1 0.6 .04 .026 .24 .05 Coregonidae Cyprinidae Peamouth 1 1 3.1 .04 .135 1.27 .14 Lake Shiner 1 2 4.7 .09 .204 1.92 .20 Cottidae 2 2 6.0 .09 .260 2.44 .52 Remains 6 9 13.0 .39 .565 5.31 3.39 Copepoda Heterocope 2 8 T .35 T T - Cladocera Bosmina 2 1 T .04 T T - Porifera 7 - 6.0 - .260 2.44 1.62 Total no. of stomachs with food - 16 Tot al no. of stomachs empty 7 (30.4$ of total) Tot al no. of stomachs 23 # Total sample . x Consumption Index Burbot (Tables LV,LVI). The Burbot is present in Babine and Morrison but not in Lakelse* From Babine and Morrison 12 and 4 stomachs respectively hare been analysed* In the Babine sample no definite whitefish remains were noted, and unidenti• fied remains constituted only a small volume. Two of the Morrison fish had definitely taken whitefish, and one other had taken "Salmonidae or Coregonidae"* Thewe fish are not netted in accordance with their observed abundance* The Predation Index of this fish is diBtinotly highest in Morrison lake* Discussion* In certain southern lakes of British Columbia (Monro and Clemens 1957) Squawfish and Ling feed to some extent on Rooky Mountain whitefish, and the Ling on Eastern whitefish and their eggs. Whitefish eggB were found in the stomachs.of Seulpins (Cpttus asper). The evidence of an extensive study of the food of Lake Nipigon fishes (Clemens, et al 1923, 1924) suggested relatively little predation on the Eastern whitefish, even by such particularly aotive fish eaters as Lake trout and Ling. Similar conclusions were made by Rawson (1930) for Lake Simooe and by Bajkov (1930) for Lake Winnipegosis. In Lake Opeongo (Fry and Kennedy 1937) predation by the Lake trout on the Eastern whitefish was fairly heavy, but in Great Slave lake and Lake Athabaska (Rawson 1947), this fish fed only occasionally on the Eastern whitefish. Hart (1930) for Lake Nipigon and Bajkov (1930) for Lake Winnipegosis, both stated that predation on eggs of Eastern whitefish by the Common TABLE UV STOMACH ANALYSES OP 12 BURBOT CAUGHT BY GILL-NET IN BABINE LAKE, 1946. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach^ Volume Insecta Ephemerida 1 1 T .08 T T ( nymph) Trichoptera 2 2 .25 .17 .02 3.3 (larva) Diptera 1 1 T ,08 T T (larva & pupa) Remains 2 T T Fish Cottidae 1 1.6 .08 .13 20.6 Cyprinidae 1 0.4 .08 .03 5.1 (Lake shiner) Remains 3 .42 .08 .6 0.9 Amphipoda .08 .6 Hyalella sp. 1 .05 Copepoda T ,33 Heterocope 2 Chilopoda 1 .05 .08 .6 (Centipede) 1 Hirudinea (leech) 1 6 4.50 .50 .38 58.1 No. of stomachs with food - 8 No. of stomachs empty _4 (33.3$ of total) Total No. of stomachs 12 if Total sample. TABLE UVI. STOMACH ANALYSES OF 4 BURBOT CAUGHT CAUGHT BY GILL-NET IN MORRISON LAKE, 1947. August. No. of Stomachs Total No. Total Vol. Av. No. Av. Vol. with in all in all per per % Organisms Stomachs Stomachs Stomach^ Stomach^ Volume Fish Whitefish 2 3 17.3 .75 4.33 17.03 Salmonidae or 1 1 .3 .25 .01 .02 Coregonidae Peamouth 84.3 .25 21.08 82.94 No. of stomachs empty - 1 (25$ of total) # Total sample sucker was not great. Certain other fish, including the whitefish itself, did take many eggs. In the Skeena lakes the most active predators on whitefish are the Lake trout and theiBurbat These are also, apparently, the important predators in various other lakes. However, it is surprising that, all in all, both whltefishes are subjected to less predation than are many other species of fish, ^'his is probably due to differences in habitat. The heaviest known predation on whitefish in the Skeena system occurs in Morrison lake, where many Eastern whitefish are taken by Lake trout and Burbot. (See the variou6 food tables and TableThis intensity of predation appears to be in accordance with the abundance of the three species in the lake. GROWTH RATES. A study of the growth of the Skeena whitefish from collections taken in Lakelse, Babine and Morrison lakes was made by the writer during the University year 1947 - 1948 as part of his Bachelor of Arts thesis. A summary of these findings are presented here. The method employed was to plot the age of the fish, as determined by the scale method, against its fork length at the time of capture. The ages of the following fish were so determined; 59 Common whitefish from Babine lake and 155 from Morrison lake; 150 Rooky Mountain whitefish from Babine lake, 118 from Lakelse lake and 11 from Morrison lake. Male and female fish were grouped together. The growth of the Common whitefish in Babine and Morrison lakes. Tabled vn. summarizes the growth data. Growth of the species was faster in Babine lake than in Morrison lake, at least in the first three years of life. From their third year on the rate of both populations was more equal, but because of its earlier advantage and the maintenance of a slightly faster rate the Babine fish remained the larger. Instantaneous growth rates of the two populations between their thrid and ninth years were 0.099 for Babine fish and 0.095 for Morrison lake fish. No fish of a length greater than 480 mm. were netted in either lake. The oldest fish reoorded were 2 at 10 years, (fork length 441 mm.) from Morrison lake, and 2 at 11 years (fork length 475 mm.) from Babine lake. When these rates of growth were compared with those of the species in Okanagan lake, British Columbia (McHugh, 1949) and three Ontario lakes (Hart 1931) it was found that growth in the Skeena lakes was most similar to that of Lake Ontario fish from Belville, and to that in Okanagan lake. /6z. TABLE l»v»l. GROWTH OF THE COMMON WHITEFISH IN BABINE AND MORRISON LAKES. FORK LENGTH - mms NO. OF SPECIMENS (Weighted means) AGE GROUP BABINE MORRISON BABINE MORRISON II - 151 6 III 248 207 7 4 IV 307 264 .4 6 V 365 307 8 5 VI 384 321 11 15 VII 394 329 9 27 VIII 419 344 10 29 IX 449 366 7 2 X 470 441 1 2 XI 473 - 2 .- //A In Shakespeare Island lake and Lake Nipigon the overall growth rates were considerably slower, and fish of sizes similar to the oldest Skeena fish were as old as 27 years (Shakespeare Island lake), and 20 years (Lake Nipigon). The growth of the Rooky Mountain whitefish in Lakelse and Babine lakes. A summary of the growth data of this species is given in Table Lvin. The growth of the Babine fish was faster than that of the Lakelse fish during its first two years, since, although no fish younger than 2 years were recorded from Babine lake, the size of the Babine fish was greater than that of the Lakelse fish at that age. From then on the growth of both populations was very similar, with the Lakelse fish possibly growing at a slightly faster rate. Instantaneous growth rates for the second to ninth year period were 0.098 for Babine fish and 0.119 for Lakelse fish. Only 11 specimens were available from Morrison lake. The ages and lengths of these too, indicated a slower growth in Morrison lake than in Babine. Comparisons were made with rates of growth determined by McHugh (1941) from specimens taken from various lakes and rivers including Cultus lake of British Columbia. Growth in the Skeena lakes was found to be most similar to that in Cultus lake, but the latter was somewhat faster than in either Babine, Lakelse or Morrison lakes. The growth of both species was compared. The Common whitefish main• tained a faster rate of growth than the Rocky Mountain whitefish, particularly in early years. The data indicated that in the Skeena lakes the former have a longer life span than the Rocky Mountain whitefish. Both these conclusions agreed with those made by McHugh (1939) for these fishes in Okanagan lakes of British Columbia. TABLE l~v«M GROWTH OF THE ROCKY MOUNTAIN WHITEFISH IN LAKELSE, BABINE AND MORRISON LAKES FORK LENGTH - mms NO. OF SPECIMENS (Weighted means) AGE GROUP LAKELSE BABINE MORRISON LAKELSE BABINE MORRISON I 90 - - 1 - - II 127 166 177 6 12 3 III 176 204 213 14 12 6 17 211 246 228 10 22 2 V 242 366 - 31 26 - VI 281 281 - 28 17 - VII 302 315 - 16 22 - VIII 336 341 317 7 16 7 IX 330 348 - 4 9 - X 338 365 1 1 _ COMPARISONS OF BODY PROPORTIONS. As part of the thesis already referred to the writer also presented a comparative study of morphological characteristics of populations of both species in Babine, Morrison and Lakelse lakes* Specimens were collected in the field during the summer 1947, were preserved, and were examined in the autumn of that year* Wherever possible a total of 36 measurements and counts were made on each specimen* Approximately 12 and 20 Common whitefish from Babine and Morrison lakes, and 27 and 25 Rocky Mountain whitefish from Babine and Lakelse lakes were so examined* The original data were presented in detail in the Appendix of the thesis, which has been placed in the Depart• ment of Zoology of this University* Because of the relatively small number of specimens in each sample and to effect a valid comparison of fishes dissimilar in total length, a comparison of several body parts was made by employing the method of the analyses of covariance as recommended by Mottley (1941). The remaining body parts were compared on the basis of their respective percentage of body length* Populations of the Common whitefish in Babine and Morrison lakes were found not to differ significantly in the following oharaoteristiosj head length, head depth, snout to ocoiput, ocoiput to insertion of dorsal fin, snout-length, interorbital, length of maxilla, anal fin, all fin bases with the exception of the dorsal fin base, body depth and width, oaudal peduncle width and length, pectoral fin to insertion of ventral fin, insertion of ventral fin to vent, numbers of gill rakers on either aroh, numbers of fin rays in all fins* The following characteristics differed between the two populations of whitefish; the horizontal diameter of the eye of the Morrison fish was consistently larger than that of the Babine fish; all fins of the Morrison lake fish (exception the anal fin) were longer than those of Babine fish; there were usually a few more scales along the lateral line of the Morrison fish, and a more frequent occurrence#of an additional row of scales both above and below the lateral line. Babine and Lakelse populations of the Rooky Mountain whitefish were similar in the following characteristics: head length, head depth, snout to oooiput, oociput to dorsal insertion, horizontal diameter of eye, snout length, interorbital, length of maxilla, all fin lengths and bases with the exception of the length and base of the anal fin, body depth and width, pectoral fin to insertion of ventral fin, insertion of ventral fin to vent, scale rows above and below the lateral lines, gill rakers on each arch, the numbers of rays in all fins. The length of the anal fin and its base were both greater in the Lakelse fish. The Lakelse fish possibly had a longer and deeper caudal peduncle. The Babine fish generally had a few more scales along the lateral line. FACTORS LIMITING DISTRIBUTION. Rooky Mountain Whitefish. This fish has been found in every Skeena lake investigated. It has also been observed in numerous streams. Lakes where Rooky Mountain whitefish are found vary from suoh shallow and warm coastal waters as Lakelse, to deep and oold lakes like Morice, and to the northern lakes at high altitudes, such as Bear, Johanson, Kluayaz and others. Sinoe the Rocky Mountain whitefish is.»not known from Alaska, the Yukon or in northwestern Canada, it is generally assumed (for example, Carl and Clemens 1948) that it has repopulated British Columbia from a refuge oentre south of the Pleistocene ioe sheet. It probably entered Skeena waters via the Columbia and Fraser systems. No factors have restricted its distribution at any point throughout the Skeena drainage. Eastern Whitefish. Many lakes have been insufficiently investigated to allow cate• gorical statements on the distribution of the Eastern whitefish. However, it seems fairly certain that the Eastern whitefish is restricted to Skeena lakes east of the Coast range. It has been netted only in Babine and Morrison lakes, and in Bear and Azuklotz lakes. VKhen considering the general distribution of this fish throughout North (America, it is apparent that it prefers clear, cold and deep waters. These conditions, as described in an earlier section, do not obtain in such lakes as Kluayaz, Slamgeesh, Damshilgwit, Asitka, Sustut, Nilkitkwa, Stephens and Kitwanga, all lakes east of the Coast range, and in which no Eastern whitefish have been netted. Slamgeesh, Damshilgwit and Asitka lakes were desoribed in this paper as dystrophic lakes, while /ff- Nilkitkwa, Stephens and Kitwanga were considered as being eutrophic (Stephens and Kitwanga being decidedly so, while Nilkitkwa deviated some• what from the eutrophic condition probably because of the circulation provided by the Babine run-off). Sustut was tentatively included with the oligotrophia lakes primarily because of its high altitude, and maximum depth of 18 m. It only just enters this category, however, for it has many extensive shallows, and is a small lake (less than 1 square mile). The preference of the Eastern whitefish for oligotrophio lakes is probably a sufficient reason to explain their exolusion from these Skeena lakes where suoh conditions are distinctly absent. The remaining lakes of the central plateau are Johanson, Motase, Swan and Morice. Motase lake is not a deep lake, though it does exceed 30 metres. The main tributaries of this lake are of glaoial origin, and the lake is therefore heavily silted (Secchi disc readings of 8 inches were obtained). Suoh a condition, together with its small size and probable fairly low mean depth would present direct unfavourable con• ditions for the Eastern whitefish, and would also, no doubt, result in a poor abundanoe of food organisms. Early in this paper it was stated that due to the loss of a speoimea of a whitefish from Swan lake, which apparently might have been an Eastern whitefish, no definite statement could be made regarding either it8 absence or presence in this lake. Considering the conditions of Babine, Morrison and Bear lakes, Swan lake does not seem to present any obstacles to the establishment of the Eastern whitefish. Plankton is somewhat more abundant in Swan lake than in many other lakes including Babine, Morrison, Bear and Lakelse. No bottom dredgings have been taken, but there is no evidence to indicate that they would be critically scarce. The writer's opinion is that there is a good possibility that the Eastern whitefish is present in Swan lake. If this is not the oase, no reason oan be given at the present to explain its absence. Certainly there does not seem to be any obvious physical barrier to the species which would prevent its migration from Bear or Babine lakes, and such migration could surely have been aohieved during the time sinoe the entry of the whitefish into the drainage following the retreat of the Pleistocene ice sheet. Should this fish effeot its migration in an upstream direction, there remains the possibility that it may have entered the drainage by some Buch route now extinot, and that it has not extended its distribution in a downstream direction. Johanson lake is fairly deep, having a mean depth of approximately 15 metres; it is, however, a very small lake, with an area of 0.6 square miles. Most of the lake shore drops off rapidly to deep water. Its water is fairly clear, though the more important of only two tributaries to the lake is from a heavily silted source (Darb lake, 1% miles long). Johanson lake offers poor conditions for the establishment of an Eastern whitefish population, and in particular has inadequate spawning facilities for this fish which usually moves on to shoals to spawn. Morice lake has been netted sufficiently to have indicated the presence of the Eastern whitefish had there been any there. This lake lies at an elevatiea of 2614 feet, in a precipitous terrain where several glaciers still remain. It forms part of the headwaters of the Bulkley river. The Bulkley and Babine rivers meet at Eazelton (elevation 973 ft.), and between Hazelton and Morice lake os»the Moricetown canyon and falls. Most of the year the falls would present an obstacle to the upstream migration of fish except some of the salmon or trout. At times of high water they are still difficult to traverse but this possibly oould be done by such fish as Eastern whitefish. Of course the falls must have been less of a hazard in their early post-Pleistocene history. The lake is very deep (maximum depth more than 236 m.; mean depth 100 m.), and with the exception of one small bay shallow waters are completely lacking. The bottom of the lake is made up of silt, sand and gravel, and no mud or humus bottoms were detected. There is no rooted aquatic vegetation. The waters of the lake are cold, apparently not rising above 14°C. Plankton and bottom organisms are apparently very scarce. Fish present in this lake are Lake Trout, Dolly Varden char, Rainbow trout. Rocky Mountain whitefish, Northern sucker, Sculpin and perhaps some smaller species. None is abundant, and the Lake Trout were found to be very thin. Rooky Mountain whitefish, on the other hand, were more abundant and fat, and their stomachs were full of small molluscs. Though the streams feeding the lake are heavily silted, a Seochildisc was visible at 5 m. in September of 1945. Regardless, therefore of the mode of origin of the Eastern whitefish in the Skeena drainage, and of -whether it has been possible for the fish to enter Morice lake, conditions in the lake are oertainly not those which would favour the establishment of a population of Eastern whitefish. Bottom food and spawning facilities are poor, and there is, apparently, an insufficiency of plankton to favour a change of feeding habits in that direction such as shown by the Morrison lake whitefish. These factors in themselves may be sufficient to explain the absence of the Eastern whitefish in Morice lake. No Eastern whitefish occur in the coastal lakes, Johnston, Alastair, Lakelse, and Kitsumgallum. Little is known of Johnston lake other than that it is small, fairly deep and somewhat opaque from glacial silt. Lakelse lake is small, shallow and warm, and generally eutrophio in type. '7'- Alastair lake has an area of about 2*3 square miles, and is divided into a shallow and a deep half. The shallow northern half of the lake is be- ooming a marsh. Drainage into the lake from the bordering mountains brings glaoial silt and sand, but the lake itself is clear. No oxygen deter• minations have been made, and no data can be given conoerning the abun• danoe of bottom fauna or plankton. Kitsumgallum lake, somewhat larger than Lakelse lake, is deep, cold and heavily silted. Most of its shore• line drops rapidly to deep water. The lowest abundance of plankton for any of the Skeena lakes so investigated has been recorded for Kitsumgallum. Considering the morphological characteristics of this lake, bottom fauna must also be very sparce. The only fish known to inhabit the lake are the Rocky Mountain whitefish, Dolly Varden char. Cutthroat, Peamouth chub and Sculpin. These three lakes then, also present unfavourable conditions for the establishment of Eastern whitefish populations. If it can be assumed that no barriers bar the downstream migration of the fish from the interior lakes, then it must be that the unsuitability of these coastal lakes is restricting the further distribution of the species. In the Wisconsin age of the Pleistooene the Cordilleran Glacier Complex or Ioe Sheet, centred in British Columbia, covering the entire province and extending from Alaska, south to approximately the 48th parallel of latitude (Flint 1947). British Columbia lakes must therefore have been repopulated by their present day fishes during the period following the retreat of the ice. As the ice advanced over the continent fish were either exterminated, or their ranges were shifted to areas far to the south, or "they were able to survive in certain unglaciated regions. Aocording to the characteristics of their present day distribution in North America, the origin of British Columbia fishes can be given a general description. Thus certain fishes must have entered the province from the south, while others have come either directly from the regions of Alaska which escaped glaciation, or indirectly from a Mississippi refuge south of the Laurentian ioe sheet, via the Great Lakes, and thence northwestward by way of a succession of large glacial lakes now extinct* Aooording to Radforth (1944) certain fish have populated Ontario waters from an Alaskan source which escaped glaoiation. Those of interest here, since they also ocour in the Skeena are the Eastern whitefish, the Lake Trout, the Northern sucker and the Burbot. There is the possibility that the Northern sucker, the Burbot and the Northern pike (Esox luoius, not present in the Skeena) may have been able to endure the conditions of the Mississippi plains, and survived there. Thus Wynne-Edwards (1947) considers it probable that these fish have entered the Yukon from the Mississippi valley and the Great Lakes. However, the Eastern whitefish, the Northern sucker and the Burbot are"closely related to, if not identical with species present in Eurasia (Berg 1936). Since also, these fish and the Lake Trout are continuous from a "narrow area of dis• tribution in eastern North America towards a widespread range in the northwestern part of the continent", the hypothesis of an Alaskan centre of redistribution is further strengthened (Radforth 1944). Hence in the Skeena system the origin of these fish is probably from an Alaskan source, possibly directly s outhward down the central plateau from the Yukon system, or perhaps by way of the Mackenzie-Peace system, which as men• tioned in an earlier section, appears to have penetrated the Great Divide even in recent times. The Lake Trout is present in the four lakes which contain Eastern whitefish, and in one other lake only, Morice lake, (exoepting Nilkitkwa lake, at the outlet of Babine lake, whioh the whitefish, no doubt enters temporarily). 'The char is not abundant in Morioe lake, but conditions there would seem to suit this species somewhat better than the Eastern whitefish. In the first place, the char can and does feed on small trout and salmon, Rocky Mountain whitefish and other species; whereas the whitefish needs sufficient bottom organisms, or at least a good supply of zooplankton. The Burbot is found in only one lake, Sustut, where there are no Eastern whitefish (again excepting Nilkitkwa lake). Sustut is a small shallow lake, unsuitable for the Eastern whitefish and it is almost surprising that the Burbot is there. However, the presence of trout, salmon, Rocky Mountain whitefish and other fish no doubt ensures a food supply for .a small population. The Northern sucker has been netted in all but a few of the Skeena lakes, and probably is present in some of these which have been investi- gated only friefly. In particular it is present in suoh coastal lakes as Lakelse and Alastair. It has not been netted in Kitsumgallum. The suoker can apparently tolerate a wide variety of conditions, as evidenced not only by its Skeena distribution, but by that also in other parts of the continent, the Mississippi drainage, for example. Since two of "these associates of the Eastern whitefish (the Burbot and Lake Trout) are, with few exceptions, restricted to the same lakes as the whitefish, it may seem at first that some barrier has been effective in halting their westward distribution. If this is the case, no such barrier can be defined or explained. However, the third associate (the Northern sucker) has entered even the most westward lakes, and since this form has an apparent wider range of tolerance, it is more likely that conditions obtaining in the individual lakes themselves (as already described) have prevented the establishment of the other species* Summary. The Rocky Mountain whitefish has been recorded in every Skeena lake which has been investigated, and has been observed in many rivers and streams* The Eastern whitefish has been recorded definitely only for Babine, Morrison, Bear and Azuklotz lakes. The loss of a specimen of whitefish from Swan lake prevents a definite statement for that lake. There is no known barrier which has prevented a further westward migration of the Eastern whitefish. With the exception of Swan lake, all the other Skeena lakes in which there are no Eastern whitefish have definite conditions unfavourable to the establishment of this species. For the most part these conditions are small area, warm and shallow waters. Certain lakes, Morice, Kitsumgallum, Motase and Johnston, though they vary greatly in size and depth, present such unfavourable conditions for the Eastern whitefish as heavily glaciated waters, a poor abundance of food organisms, and a lack of shoals necessary for spawning. Factors which have limited the distribution of the Eastern white- fish to other Skeena lakes are probably the individual conditions ob• tained in those lakes rather than some physical barrier. FACTORS LIMITING ABUNDANCE. Rooky Mountain Whitefish. Lakelse Lake. Rocky Mountain whitefish are not numerous in this lake. The total number caught by standard sets in three years (1945 - 1947) was 186 fish, giving a o.n.n. of 0.32. Peamouth chub, Squawfish and Cutthroat trout are each more plentiful than the whitefish, and in the same three years the numbers of these fish caught in standard sets were as follows: Peamouth chub, 3,238 (c.n.n. 5.62), Squawfish 768 (c.n.n. 1.33), Cutthroat trout, 523 (c.n.n. 0.91). The trout are doubtless more abundant than the netting data indioate, since they are not entirely bottom feeders, and range into deeper water and above the nets. There do not seem to be any direct morphological nor physico- chemioal conditions of this lake which would restrict the population of whitefish to the small size indioated. The water is dear, well oxygenated and cool. Spawning facilities are adequate. Food, however, in the form of bottom organisms is not abundant and is shared with such oompeting species as the Peamouth chub and Squawfish, and the Cutthroat trout to a certain extent. These fish, particularly the chub, whose diet is most common to the whitefish, are numerous. The depth zones inhabited by the Peamouth chub, Rocky Mountain whitefish and Squawfish are very similar in Lakelse lake. There was no evidence of any great predation by other fish, but this applied to summer conditions when such prey as Sockeye fry and Stickle• backs would be most plentiful. In early spring, and during late fall and winter, perhaps, other species suoh as the whitefish may be more sought after, particularly if migratory habits have herded prey and predators closer together. Babine Lake* In all divisions of Babine lake (excluding Wright bay of Division II) a total of 304 Rocky Mountain -whitefish was netted from 167 standard sets in 1946 and 1947. This represents a c.n.n. of 0.36. There were always a few more fish netted in Division II than in Division I and they were again more numerous in the shallow conditions of Wright bay. It is difficult to compare Babine and ^akelse lakes in this respect, but the data do indicate that there were probably as many Rocky Mountain whitefish per unit area of the shallower waters in Babine lake as in Lakelse lake. In that seotion which dealt with the bottom fauna of the lake, it was shown that even in the littoral tone there was probably a poor abun• danoe of bottom organisms. The important competitor fish were again the Peamouth ohub and Squawfish, but in Babine lake the relative abundanoe of these fish differred markedly in some areas from conditions in Lakelse lake. Also, in Babine lake the Eastern whitefish is present, and these two fish compete between themselves for the bottom organisms, for although the maximum occurrence of the Eastern whitefish is in deeper water than that of the Rooky Mountain whitefish, the ranges of each overlap con• siderably. In Division I of Babine lake, the Rooky Mountain whitefish followed the Peamouth ohub in the gill-net catches (exoluding the plankton eating Kokanee, Oncorhynchus nerka kennerlyi). The Squawfish was one of the less often caught fish in that division. In Division II the Rocky Mountain whitefish lead the catches (again exoepting the Kokanee), while the Squawfish and Peamouth chub were the least caught fish of any that were usually netted there. Conditions differred again in Wright bay of .Division II, for here the Peamouth chub and Squawfish were particularly abundant, and were much more plentiful than the Rocky Mountain whitefish or any other species. '77- When the growth of the Rocky Mountain whitefish in the two lakes was compared, it was found that the Babine fish had grown faster. At three years of age Babine fish were larger than the Lakelse fish of the same age, therefore the more rapid growth had been effected prior to this, and pro• bably during the first year. The advantage may have been attained during a very early plankton feeding stage, or later when the fish had turned to bottom organisms. In either case the abundance of plankton or bottom fauna in Lakelse lake is probably not so much greater than in Babine lake as to be plentiful for the numerous oompeting Peamouth ohub, Squawfish, trout and other species. In other words competition for a limited food supply, though probably operative in both lakes, is more serious in Lakelse lake than in Babine lake, or at least in certain areas of Babine lake. At this point a condition should be referred to, which though it is, perhaps, obvious, seems to have been neglected in the literature possibly because of the difficulties of its assessment. The condition referred to is, that if lakes are to be oompared as to the abundance of their food resources, some indication should also be given of the size of fish populations inhabiting the lakes. T^o lakes, for example, may have potential equal numbers of bottom organisms, but if for some reason other than food supply, one lake is much more heavily populated than another, its standing crop (which is what dredging will measure) will be considerably less than that of the other lake. Thus the apparent mediocrity of the bottom fauna of Lakelse lake must be due in part to the large numbers of certain fish it is supporting. A similar oondition is particularly evident in Morrison lake, where a bottom-feeding fish, the Eastern whitefish, has turned to a diet which is almost exclusively plankton. Plankton in Morrison lake is that much more abundant than the quantitative analyses based on straining the water with plankton nets indioate. In other words, a true estimate of the standing crop, either of bottom organisms or of plankton, would include a measure not only of those organisms on the bottom or in the water, but of that also in the stomachs of fishes. In Babine lake there are Burbot and Lake Trout, two important predators whioh are not present in Lakelse lake. Neither of these fish were well sampled and they are no doubt more numerous than the data indicate. Their predation on the Rocky Mountain whitefish is probably not serious since they tend to inhabit deeper water than the whitefish. There is no evidence to indicate serious predation on the whitefish by Squawfish or trout. Morrison Lake. Approximately 50 gangs have been set in this lake in three years. These took many Eastern whitefish and fair numbers of other species, but only about 15 Rocky Mountain whitefish. Eleven of these were netted in the summer of 1947. Stomach analyses showed that they had fed almost exclusively on bottom organisms, the important forms being the caddis worms. A trace only of plankton (Cladocera) had been eaten by one of nine fish. As the food studies of this paper have shown, the abundant Eastern whitefish of Morrison lake feed almost wholly on plankton. The gill-raker counts of Rocky Mountain and ^astern whitefish in Morrison lake were 20.6 and 27.6 respectively (average number of gill-rakers on first gill arch). The gill-rakers of the Rocky Mountain whitefish are short and stubby; those of the Eastern whitefish long and slender. Thus the Rooky Mountain whitefish is probably less well adapted for plankton feeding than the Eastern whitefish. Little has been done in the way of bottom sampling, but the evidence of the food of Eastern whitefish, and a few dredgings have in• dicated a paucity of bottom fauna in the lake. Squawfish and Peamouth chub follow the Eastern whitefish in abundance in that order, but they are not nearly as numerous as in Lakelse lake. The chub particularly, and to some extent the Squawfish, are bottom feeding fish, and the relatively fewer numbers of these species and the Rocky Mountain white- fish probably indicate that the scaroity of bottom fauna is limiting their abundance in Morrison lake, though the argument is admittedly circular. Forty-one Peamouth chub in Morrison lake (Table x-*x<. ) had con• sumed an average volume of food per stomach of 0.13 cc. In Babine lake (Table Axy.. ) 31 Peamouth chub had consuned an average of 0.54 cc of food per stomach. The important food in each lake was the gastropods, followed by caddis worms, but it is the difference between the quantities of gastropods taken which effects the apparent great difference in amount of food consumed per fish in the two lakeB. Food analyses for Lakelse Rooky Mountain whitefish showed that mayfly nymphs, molluscs and caddis worms constitute the bulk of the diet, in that order. The variety and abundance of bottom forms is doubtless greater in Lakelse lake, and thus the evidence of the diets of Peamouth chub and Rocky Mountain whitefish in Morrison lake may indicate that a scaroity of mayfly nymphs and molluscs is the immediate reason for the general paucity of bottom fauna in the lake. Apart from such conditions as are characteristic of the oligotrophic nature of most of Morrison lake, no explanation oan be given at this time which would explain why there could be any very serious soarcity of bottom fauna in the lake. Physico-chemical conditions are apparently quite satisfactory. Water analyses, which might have provided a clue, have not been made. Though the terrain has not been geologically sur• veyed, it is probably similar to the eastern drainage of Babine lake, which is mostly a rolling, drift-covered area. Wind action is not ex• cessive. The two important tributaries are from Haul and Salmon lakes to the north, of whioh almost nothing is known. The few dredgings taken in the northern and in deeper southern parts of the lake, usually brought up a fine, grey adhesive mud. There was little organic material in these hauls, and if these are the conditions throughout the lake they are doubt• less unfavourable for bottom dwelling organisms. A fire of some twenty years ago destroyed much of the forest growth around the north of the lake, and this, doubtless has had certain deleterious effects upon the aquatic : life. Whatever the primary factors responsible, it seems very probable that a serious paucity of bottom organisms is restricting the numbers of Rocky Mountain whitefish in Morrison lake. Mayfly nymphs and molluscs appear to be particularly scarce. The Eastern Whitefish. Babine Lake. The oligotrophic conditions of Babine lake are apparently \ suitable for the maintenance of populations of Eastern whitefish. These i \ fish are not, however, very numerous, and it would be fruitless to attempt even small scale commercial operations. In 1946 and 1947 a total of 121 Eastern whitefish was netted in Divisions I and II (excluding Wright bay) from the setting of 136 five-net gangs. This gives a c.n.n. of 0.18. No Eastern whitefish have ever been netted in Division III. The important food of the Eastern whitefish in Babine lake is the small gastropods. These made up over 70 per cent of thef ood of 39 fish. a Very few dredgings have been made, but those did indicate a poor abundance of bottom fauna even in the littoral zone. Sharing of a meagre food supply with such competing fish as Rocky Mountain whitefish (whose range from shallower water overlaps that of the Eastern whitefish), the Peamouth ohub and the Squawfish is doubtless the major factor which is restricting the abundance of these fish in Babine lake. In the large Canadian lakes where Eastern whitefish are sufficiently numerous to support large-scale commercial fisheries, the most important item of their diet is the small, bottom-dwelling amphipod, Pontoporeia (see section "The food of the Eastern whitefish"). Though their distri• bution varies in different lakes, these forms are usually abundant at all depth8. They are particularly suitable, in terms of availability, for the Eastern whitefish, whose zone of maximum occurrence is in deeper water than that of oertain other bottom-feeding fish. Pontoporeia is not present in either Babine, Morrison or Lakelse lakes where dredgings have been made. In those large Canadian lakes where it is abundant this organism seems to be filling a niche that no other form can do quite so effectively, and it seems probable that the situation as far as the Eastern whitefish is concerned, would have been greatly enhanced had Pontoporeia existed in the Skeena drainage. According to Larkin (1948) Pontoporeia and Mysis thrive in oligotrophic lakes, and occasionally in moderately eutrophio lakes. Larkin suggests that it might be a valuable experiment to transplant these crustaceans into alpine and sub-alpine lakes of low productivity. Babine lake should provide excellent conditions for suoh an experiment, as long as it was considered that the Eastern whitefish warranted such development in that territory, and provided that a large increase in its numbers would not defect the situation of game fish or the young Sookeye salmon. Since young Sockeye salmon are pelagic, and feed al• most exclusively on plankton they should not be seriously affected. If the transplant was successful, the game fish might profit by it. Babine lake in its present condition appears to be an inefficient system, and a poor producer of fresh-water fishes. Fish cultural develop• ment of the lake, by the introduction of suitable food for -the Eastern whitefish, might enhance the resources of that territory. Morrison Lake. In this lake the Eastern whitefish has apparently been able to adapt itself to a diet of plankton crustaceans. It did this presumably beoause of a scarcity of bottom fauna and possibly irrespective of the presence of potential bottom-feeding competitors. In 1946 and 1947 a total of 241 fish was caught from 110 sets (22 gangs). This represents a relatively high c.n.n. of 2.19. Though the change seems to have been quite successful, as indioated by the large numbers of the whitefish in the lake, it is problematical whether the diet is as efficient in promoting growth as bottom organisms would be. The average volume of food per,stomaoh of 39 Babine fish was 4.28 o.c., and that for 95 Morrison fish was 0.32 cc. Seventy-one per cent by volume of the food of the Babine fish was made up of gastropods, whose shells would constitute a great part of the total volume. However, the difference between the two lakes is too great to attribute wholly to inorganic material in the food of the Babine fish. The sampling error involved in such small samples is no doubt great, but it seems possible that by taking plankton, the ^astern whitefish in Morrison lake is feeding less efficiently. The fish's prehensile mouth and musoular stomaoh are designed for the search and consumption of bottom organisms, and in Morrison lake it is probably forced to expend a greater relative amount of energy in pursuit of its food than in lakes where it feeds on the bottom organisms* When proportionate parts, gill- raker and scale counts were compared between Morrison and Babine lake fish, very few differences of significant proportions were found. Unfortunately gill-raker lengths were not compared. The eye of the Morrison fish was a little larger, and this may have some bearing on its ability to feed efficiently on plankton. The growth of the Eastern whitefish in Morrison lake was shown to be slower than in Babine lake, and particularly in the first, or first and second years. Competition for the plankton food in Morrison lake was suggested as the possible cause for slower growth. Besides the whitefish, Sockeye salmon in Morrison lake also feed on the plankton. However, the standing crop of plankton in summer was moderately high, and under such conditions might be sufficient for all consumers. Though seasonal variations might provide more critical minima in the quantities of plankton, they might also be accompanied in the fish by reduced metabolic activity because of lower temperatures, and the need therefore, of less food. It is impossible at this time to determine the seasonal variations in the abundance of net plankton in Morrison lake, but if it were to follow, in a general manner, that described for Lake Mendota ( Birge and Juday 1922), then it is possible that despite the abundanoe of plankton-feeding fish in Morrison lake, there is sufficient food for them at any time. Until the seasonal variations in abundance of plankters, and of specifio plankterB in specific lakes is better understood, it is safer to be aware of the potentialities of competition, and to rely on indirect evidence such as the numbers of fish and their condition. Morrison is a moderately oligotrophio lake. If the bottom sediments of the lake are suitable, Pontoporeia might be introduced here to replaoe the plankters in the diet of the whitefish, and thus to leave a greater abundanoe of plankton food for the young salmon. Other Lakes. Conditions in the remaining Skeena lakes as they pertain to food supply are insufficiently known to go beyond generalizations in assessing their abilities to maintain populations of the Eastern or Rocky Mountain whitefish. The only other lakes known to have the Eastern white- fish are Bear lake and its tributary lake, Azuklotz. No dredgings have been made in Bear lake, and although bottom fauna may not be particularly plentiful, the relatively high catches of both whitefish indioate better bottom-food conditions than in most of the lakes. Catch per net-night values for Rooky Mountain whitefish were 4.36 (1945), 1.67 (1946) and 1.70 (1947); and for the Eastern whitefish 1.18 (1945), 1.13 (1946) and 1.50 (1947). It is doubtful if Pontoporeia is present in Bear lake. With the exception of Swan lake, none of the remaining Skeena lakes seems to be particularly suitable for the maintenance of Eastern whitefish populations. Most of the lakes are small, shallow and relatively warm, while certain others are inadequate beoause of their silted waters, and the paucity of their fauna. (See section on "Paotors limiting the distri• bution of the Eastern whitefish"). Swan lake is perhaps suitable for this whitefish, and it may be present there. In all but Lakelse, Babine, Morrison and Bear lakes, netting has been so inadequate that o.n.n. figures are not sufficiently reliable to attach much significance to them. High oatches of Rocky Mountain white- fish in Slamgeesh, Damshilgwit, Sustut, Johanson, Swan and Stephens may indioate that they are relatively plentiful there, but only a few sets were made in these lakes* Slamgeesh, Damshilgwit and Sustut lakes were described as entering a dystrophic phase. Asitka lake is in a similar condition, but no netting has been done there. Kitwanga and Stephens were described as distinctly oligotrophio on the basis of all the conditions of eutrophy listed in Table '/X £ These lakes had the greatest abundanoe of plankton of 10 of the Skeena lakes so examined. The c.n.n. of Hooky Mountain whitefish in Kitwanga lake has varied in three years from 0.08 (1946) to an average of 0.7, which is relatively low. Two gangs set in Stephens lake in 1946 gave a c.n.n. of 2.4. Motase lake, described as oligotrophio, gave a low o.n.n. from a few sets, but Morice lake, also oligotrophic and silted like Motase lake gave a moderately high o.n.n. from 10 gangs. In general it seems that the Rocky Mountain whitefish are re• stricted by the available supply of bottom food, and the extent of moderately shallow water which they appear to favour. The abundance of food is itself a factor of the lake type (area of littoral zone, tempera• tures, and so forth), and is further influenced by the arrival of silt in the water. SUMMARY AMD CONCLUSIONS. Conditions obtaining in Skeena lakes have been examined to attempt the definition of factors which are primarily responsible for the dis• tribution and abundance of the whitefishes Cpregonus clupeafdrmls (Mitchill) and Prosopium williamsoni (Girard) throughout the Skeena drainage. The distribution of both whitefish and of other fishes in the Skeena drainage is described. Climatologioal and geological descriptions of the area are given. The morphometrical and physico-chemical conditions of the Skeena lakes are described, and the lakes are listed (though some of them but tentatively) aocording to the oligotrophic, eutrophic and dystrophic types. Comparisons with other Canadian lakes are made. Lakes listed as oligo• trophic are:- Morice, Kitsumgallum, Babine, Morrison, Johnston, Aiastair, Swan, Bear, Motase, Kluayaz, Sustut and Johanson; as eutrophio: Lakelse, Kitwanga, Stephens, Nilkitkwa and Azaklotz; and as dystrophic: Slamgeesh, Damshilgwit and Asitka. The depth distribution of the Rocky Mountain in Lakelse and Babine lakes, and of the Eastern whitefish in Babine and Morrison lakes is des• cribed from the analyses of the oatches of standard sets of gill-nets. Rocky Mountain whitefish are most abundant in depths up to 5m., and Eastern whitefish at depths between 10 and 15 m. The ranges of both species overlap considerably. Some variations in the distribution of small and large fish are described. The food of both whitefish is described on the basis of stomaoh analyses of fish of Lakelse, Babine and Morrison lakes. An index, termed /Sf. the Consumption Index is described, and was employed in the determination of the relative importance as food of the various organisms whioh enter the diet of the fish. Rocky MountajLn whitefish feed almost exclusively on bottom organisms, the most important of whioh are young aquatio insects, followed by small gastropods. The diet of the Eastern whitefiBh in Babine lake is very similar to that of the Rocky Mountain whitefish in that lake. In Morrison lake the Eastern whitefish feed almost entirely on plankton orustacea, of which the most important form is the copepod, Heterooope. In Morrison lake the few Rocky Mountain whitefish whioh have been netted there had fed on bottom organisms. A few descriptions of variations in the diet of young and old fish are given. The bottom fauna of Lakelse lake is described on the basis of dredgings made in 1945. The abundance of different organisms and their distribution is estimated and illustrated. A total of 628 organisms per square m. (weighted for the average area of different depth zones) is described as moderately abundant. With the exception of the Chironomidae larvae the important organisms were most abundant in the littoral zone of 0 - 5 m. The Chironomidae larvae were most numerous in the profundal zone at depths greater than 15 m.: the reason for this distribution is described, as probably being due in part to the loss of organisms during the processes of dredging and screening, and in part to the low cropping by fish of organisms in deep water. Very approximate descriptions and estimates of the bottom fauna of Babine and Morrison lakes are given on the basis of a few dredgingB made during the summer of 1946. A total of 205 organisms (weighted for average area of different depth zones) for Babine lake is described aB low. Bottom organisms are probably even more scarce in Morrison lake. The amphipod Pontoporeia doeB not occur in either of these two oligotrophio lakes; nor, possibly, in any of the other oligotrophio Skeena lakes. This condition is considered as a particular reason for the apparent scarcity of bottom organisms in such lakes* The food of the whitefish, as indicated by the analyses of stomach contents, is compared with the supply, as determined by bottom dredging* The data are adequate only for the generalization that, with the exception of the amphipod Hyalella, the important organisms are probably consumed in accordance with their abundance in the zones most frequented by eaoh whitefish. Hyalella is most numerous at depths of less than 1 m.; since such a depth is probably too shallow, and generally too warm even for the Rooky Mountain whitefish, and sinoe its occurrence in the food was pro• portionately much less than on the bottom, this organism is probably fre• quently unavailable to the whitefish. The occurrence of the Mysidaoea, My sis re1iota (positive identifi• cation pending) in Lakelse lake, is believed to constitute the first record of this organism, or that of its marine form, Mysis ooulata, in either marine or fresh-waters west of the Rooky Mountains. The marine origin of Mysis reliota is probable, sinoe the Lakelse area was once inundated by the Pacifio ooean during the wane of the Glaoial period. On the basis of their food, as determined by stomach analyses, and according to their abundanoe and distribution at different depths, as in• dicated by "the analyses of gill-net catches, the important competing fish for the food of ishitefish are listed as the Peamouth ohub, Squawfish and Cutthroat trout. The Peamouth chub 1B the most aotive competitor, especially in Lakelse lake where it is abundant. It inhabits approximately the same waters as those of the Rocky Mountain whitefish. Squawfish and Cutthroat Jtff. trout, though they feed considerably on other fish, and the Cutthroat on terrestrial inseots, also consume fairly large quantities of those bottom organisms which are important in the diet of the whitefish. These two fish are numerous in Lakelse lake, and the Squawfish is fairly abundant in Morrison lake. The Cutthroat is less important as a competitor than the Squawfish, especially in Babine lake, since it probably more often frequents deeper water than when} the whitefishes and the bottom organisms are most abundant. Dolly Varden char, the Northern and the Common suokers are des• cribed as relatively unimportant competitors, primarily because of their small numbers. By similar methods of stomach and gill-net catches analyses the major predators of whitefish are listed as the Burbot and Lake Trout in Morrison lake. These fish are present in Babine lake, but not in Lakelse lake. There was no evidence that the numerous Squawfish and Cutthroat trout predated heavily on Rocky Mountain whitefish during the summer in Lakelse lake. Both species of whitefish are considered as being relatively free from predation in the Skeena lakes, at least during summer months. Growth determinations indioate that Rocky Mountain whitefish in Babine lake grow faster than those of Lakelse lake, especially during the first one or two years. Growth of the Eastern whitefish is more rapid, especially in the first and second years, in Babine lake than in Morrison lake. Numerous and several speoies of fish competing for only a moderate supply of bottom organisms in Lakelse lake are considered as the important factor contributing to this condition in Lakelse lake; and the possible lower efficiency of feeding on plankton is suggested as the probable partial oause for the slower growth of Eastern whitefish in Morrison lake. Xfo. Morphological comparisons of Lakelse and Babine Rooky Mountain white- fish, and the Babine and Morrison Eastern whitefish indicate that only few and slight differences ocour between these populations. Rocky Mountain whitefish occur in all the Skeena lakes. No faotors therefore have, limited their distribution throughout the drainage. The Eastern whitefish has been netted only in Babine, Morrison, Bear and a small tributary lake to Bear lake, Azuklotz lake. In view of the apparent preference of the Eastern whitefish for clear, cool and deep bodies of water, that is, in general, for lakes that are oligotrophio in type, it is considered that the conditions of those Skeena lakes that are relatively small, shallow and often quite warm, are suoh that they do not favour the establishment of populations of Eastern whitefish, and constitute, therefore, factors.which have prevented the distribution of the Eastern whitefish to those lakes. Such lakes are (Dystrophic) Slamgeesh, Dam- shilgwit and Asitka, and (Eutrophio) Sustut, Stephens, Kitwanga and Lakelse. Certain lakes, though inoluded among the oligotrophio, are small, heavily silted and probably have a low abundanoe of suitable food organisms. These include Johnston, Alastair and Motase lakes. Kitsumgallum and Morice lakes are relatively large and deep, but they are heavily silted, have poor food supplies, and inadequate spawning facilities in the way of shoals. Johanson lake is moderately deep, but is small and has few shoals suitable for spawning. Swan lake seems to be the only other lake suitable for the maintenance of populations of Eastern whitefish. It is possible that the Eastern whitefish is there, but has not yet been identified. The writer does not consider that any physical obstaoles have prevented the further distribution of these fish in the Skeena drainage. Factors limiting the abundance of either whitefish in Skeena lakes are considered as those contributing to an inadequate supply of suitable food, direot unfavourable conditions of the lake waters, and insufficient spawning facilities. In Lakelse lake numerous Peamouth ohub, Squawfish and Cutthroat trout share the food of Rocky Mountain whitefish. The supply of bottom organisms is only moderate, perhaps primarily because of the con• tinuous and heavy cropping. There appear to be no other obvious character• istics of the lake, either physical or physico-chemical whioh are restricting a growth in the numbers of these fish. The situation is somewhat similar in Babine lake, for although there may be fewer chub, Squawfish or trout, the Eastern whitefish is present in this lake, and competes for the food. In Babine lake, Eastern whitefish are not numerous, probably beoause the rather low food supply must be shared, and espedially, perhaps, be• cause no Pontoporeia are present in the lake to augment the bottom fauna, particularly in deeper water. In Morrison lake there are relatively large numbers of Eastern whitefish, but exceedingly few Rocky Mountain whitefish. Here the bottom fauna is apparently very scarce, there are no Pontoporeia, and although the Eastern whitefish appear to exist successfully on plankton orustacea, this habit does not seem to be oonduoive to effioient feeding. Rocky Mountain whitefish, whose gill-rakers are fewer and shorter, still feed on the meagre bottom organisms which they share with the Peamouth ohub and possibly other fish. It is doubtful if Pontoporeia is present in Bear lake, sinoe although catohes of both Rocky Mountain and Eastern whitefish have been greater than in Babine lake, these fish are only moderately abundant there. Other conditions of this lake are quite suitable. It is likely that the Eastern. whitefish in Azuklotz lake is only as an occasional migrant from Bear lake* Rooky Mountain whitefish are probably fairly abundant in all but a few of the remaining lakes, since food, water conditions and spawning facilities are fairly suitable for these fish. Competition for food is especially effective by Peamouth chub, Squawfish and Cutthroat trout, and conditions, for Rocky Mountain whitefish would therefore be more favourable in those lakes where these competitors are not present (see Table I). Deep, cold lakes with steep shorelines appear to be least suitable for Rooky Mountain whitefish. Suoh lakes are Morice, Kitsumgallum, Johnston and Kluayaz. It is suggested in this paper that when lakes are being compared on the basis of the abundanoe of their food organisms, that the approximate numbers of their fish populations be indicated. This is believed necessary sinoe a measure of the standing crop of food which does not consider the quantity of food present in the stomachs of fishes, will not be truly comparable between two lakes whose abundanoe of fishes differs markedly. Since the oepepod Pontoporeia seems to favour oligotrophio lakes, and beoause it is particularly valuable in the food of Eastern whitefish in Canadian lakes where these fish are very abundant, it is suggested that Larkin's recommendation (1948), to introduce Pontoporeia into oligotrophio lakes of low productivity, would be very suitable for such lakes as Babine, Morrison and Bear if ever the economy of that part of the Province requires it. ...• 000 ..•• LITERATURE CITED. Bajkov, A., 1930 - A study of the whitefish (Cpregonus clupeaformis) in Manitoban lakes. Contr. Can. Biol, and Fish., fi.S., _5, 15: 1 - 15. i Berg, L. S., 1936 - Motes on Cpregonus (Prosopium) cylindraceus (Pallas). Copeia, 1: 1 - 57. Birge, E. A. and C. Juday, 1922 - The inland lakes of Wisoonsin. The plankton. 1. Its quality and chemical composition. Bull. Wise. Geog. and Nat. Hist. Surv., 64, Sci. Ser., 13: LX - 222. Carl, 0. C. and W. A. ClemenB, 1948 - The fresh-water fishes of British Columbia. B. C. Prov. Mus., Dept. Educat., Handbook 5: 1 - 132. Clemens, W. A., 1939 - The fishes of Okanagan lake and nearby wafers. Bull. Fish. Res. Bd. Can., 56: 27 - 38. Clemens, W. A. et al, 1923 - The food of Lake Nipigon fishes. Univ. Tor. Stud., Biol. Ser.. Pub. Ont. Fish. Res. Lab., 16: 173 - 188. — , 1924 - Food studies of Lake Nipigon fishes. Univ. Tor. Stud., Biol. Ser., Pub. Ont. Fish. Res. Lab., 25: 103 - 165. , 1937 - A contribution to the limnology of Shushwap lake, British Columbia. Rept. B.C. Fish. Dept., 1937; T91 - T97. Downing, S. W., 1908 - A plan for promoting the whitefish production of The Great Lakes. Bull. U.S. Bur. Fish., 28, Pt. 1: 627 - 633. Dymond, J. R., 1933 - Coregonine fishes of Hudson and James Bays. Contr. Can. Biol., N.S., 8, Ser. A, Gen., 28: 1-12. —— — , 1936 - Some fresh-water fishes of British America. Rept. Comm. Fish., B.C., 1935: 60 - 73. — , 1943 - The Coregonine fishes of northwestern Canada. Trans. Roy. Can. Inst., 24, Pt. 2: 171 - 231. and V, D. Vladykov, 1933 - The distribution and relationship of the salmonoid fishes of North America and north Asia. Proc. Fifth Pac. Sci. Cong., 5: 3741 - 3750. Eggleton, F. E., 1939 - Role of the bottom fauna in the productivity of lakes. Am. Ass. Advan. Soi., Sci. Press, Pub. 10: 123 - 131. Flint, R. F., 1947 - Glacial geology and the Pleistocene epooh. New York, IX - 589. Fowler, H. N., 1948 - Fishes of the Neultin lake expedition, Keewatin, 1947. Part I - Taxonomy. Proc. Phil. Acad. Nat. Sci., C: 141 - 152. LITERATURE CITED. Cont'd. Fry, F. E., and W. A. Kennedy, 1937 - Report on the 1936 Lake Trout in• vestigation, Lake Opeongo, Ontario. Univ. Tor. Stud., Biol. Ser., 42, Pub. Ont. Fish. Res. Lab„ 54: 1 - 20. Harper, F., 1948 - Fishes of the Neultin lake expedition, Keewatin, 1947. Part 2 - Historical and field notes. Proo. Phil. Acad. Nat. Sci., C: 153 - 184. ~ Hart, J. L. 1930 - The spawning and early life history of the whitefish, Coregonus clupeaformis (Mitchill), in the Bay of Quinte, Ontario. Oontr. Can. Biol, and Fish., N.S., 6, 7: 1 - 150. , 1951 - The growth of the whitefish "Coregonus clupeaformis (Mitchill)". Contr. Can. Biol, and Fish., N.S., £, 20: 429 - 444. Hile, R. and C. Juday, 1941 - Bathymetric distributions of fish in lakes of the northeastern highlands, Wisconsin. Trans. Wise. Acad. Sci. Arts and Letts., 33: 147 - 18 . Hubbs, C, L., 1926 - A check list of the fishes of the Great Lakes and tributary waters with nomenclatorial notes and analytical keys. Mus. Zool. Univ. Mich., Misc. Pub. 15: Jordan, D. S. and B. N. Evermann, 1896 - The fishes of North and Middle Amerioa. Bull. U.S. Nat. Mus., 47, Pt. 1: 1 - 1240. , 1911 - A review of the salmonid fishes of the Great Lakes with notes on the whitefishes of other regions. Bull. U.S. Bur. Fish. 29: 1 - 41. . N. B. Evermann and H. W. Clark, 1930 - Check list of the fishes and fishlike vertebrates of North and Middle America north of the northern boundary of Venezuela and Colombia. Rpt. U.S. Comm. Fish, for 1928. Pt. 2. Kindle, E. D., 1940 - Mineral resources, Hazelton and Smithers areas, ^Cassiar and Coast distribts, British Columbia. Geol. Surv. Can., Memoir 223:1-107. Koelz, W. K. 1927 - Coregonid fishes of the Great Lakes. Bull. U.S. Bur. Fish., 43, Pt. 2: 297 - 643. Larkin, P. A.J 1948 - Pontoporeia and Mysis in Athabaska, Great Bear and Great Slave lake's. Bull. Fish. Res. Bd. Can., 78: 1 - 33. Macfarlane, J. M., 194 - The evolution and distribution of fishes. New York; v + 564. McConnell, R. G., 1912 - Geological section along the Grand Trunk Pacific Railway from Prince Rupert to Aldermere, B.C. Geol. Surv. Can., Sum. Rpt., 1912: 55 - 62. LITERATURE CITED. Cont'd. MoHugh, J. L., 1938 - A preliminary study of the genus Prosopium with speoial reference to Prosopium williamsoni (Girard). Univ. B. C. Dept. Zool., Unpub. Thesis: 1 - 120. , 1939 - A biological survey of Okanagan lake, British Columbia. Bull. Fish. Res. Bd. Can., 56: 39 - 50. , 1940 - Food of the Rocky Mountain whitefish Prosopium williamsoni (Girard). Jour. Fish. Res. Bd. Can., 5, 2: 131 - 137. ——— , 1941 - Growth of the Rocky Mountain whitefish. Jour. Fish. Bd. Can., 5_, 4: 337 - 343. Mottley, G. Mo.C., 1941 - The covarianoe method of comparing the head- lengths of trout from different environments. Copeia, 3: 154 - 159. Munro, J. A. and W. A. Clemens, 1937 - The American Merganser in British Columbia and its relation to the fish population. Bull. Biol. Bd. Can., 55: 1 - 50. Radforth, I., 1944 - Some considerations in the distribution of fishes in Ontario. Contr. Roy. Ont. Mus. Zool., 25: 1 - 116. Rawson, D. S., 1930 - The bottom fauna of Lake Simooe and its role in the ecology of the lake. Univ. Tor. Stud., Biol. Ser«, Pub. Ont. Fish. Lab., 40: 1 - 183. , 1934 - Productivity studies in lakes of the Kamloops region, British Columbia. Bull. Biol. Bd. Can., 42: 1 - 31. — , 1939 - Physical and chemical studies, plankton and bottom fauna of Okanagan lake, B.C., in 1935. With appended data from adjacent smaller lakes. Bull. Fish. Res. Bd. Can., 56: 3 - 26. , 1941 - Soil as a primary influence in the biological productivity of lakes. Trans. Can. Conserv. Ass., 78 - 87. — , 1942 - A comparison of some large alpine lakes in western Canada. Ecology, j!3, 2: 143 - 161. , 1947 - Great Slave lake. Bull. Fish. Res. Bd. Can., 72: 45 - 68. , 1947 - Lake Athabaska. Bull. Fish. Res. Bd. Can., 72: 69 - 85. Str/rim, K. M., 1938 - Norwegian mountain lakes. Archiv. fur Hydrobiologie 33, 1: 82 - 92. Thienemann, A., 1927 - Der Bau des Seerbeckens in seiner Bedeutung fur den Ablauf des Lebens im See. Verh. Zool. B0t. Ges., 77. /ft. LITERATURE CITED. Cont'd. o Thienemann, A., 1938 - Der Sauerstoff im eutrophen und oligotrophen see* Die Binnengewasser, 4. Stuttgart. Ward, A. W., and G. C. Whipple, 1918 - Fresh-water biology. New York: IX - 1111. Welch, P. S., 1935 - Limnology. New York. XIV - 471. Withler, F. C., 1948 - Fish predation on the young sockeye (Onchorhynihus nerka) in certain lakes of the Skeena drainage as evaluated by the study of the catches and stomach contents of predators obtained by gill-netting. Univ. B. C., Dept. Zool., Unpub. Thesis: 1 - Wynne-Edwards, V.C., 1947 - The Yukon Territory. Bull. Fish. Res. Bd. Can., 72: 6 - 20. ooo APPENDIX Fig. 17. View of Lakelse lake from the east shore. Lakelse river a little right of centre. Fig. 18. Aerial view of Lakelse lake and Lakelse river. Fig. 20. View of Babine lake. Looking towards Old Fort.