The Limnology and Fish Biology of Tenmile Lake, Labrador , "

Home , Round whitefish

.+ Environment Canada Environnement Canada • Fisheries Service des peches and Marine Service et des sciences de la mer ...

The Limnology and Fish Biology of TenMile Lake, Labrador , "

•

by . R. F. Pa rsons

Technical Report Series No, NEW/T-75-3

Resource Development Branch Newfoundland Region •

, DEPARTMENT OF THE ENVIRONMENT FISHERIES AND MARINE SERVICE NEWFOUNDLAND REGION

TECHNICAL REPORT SERIES NO. NEW/T-75-3

THE LIMNOLOGY AND FISH BIOLOGY OF TEN MILE LAKE, LABRADOR

R.F. PARSONS

RESOURCE DEVELOPMENT BRANCH ST. JOHN'S, NEWFOUNDLAND A limnological investigation and fish inventory was conducted on

Ten Mile Lake, Labrador, during the summer of 1974. Chemical and

physical parameters were measured for the lake.

The pH levels ranged between 6.0 and 6.6, while specific

conductance values varied between 12.0 and 21.0 microhoms @ 25 C. The water area of the lake is 26.39 km2 with a mean depth of 2.90 m.

Thermal stratification was noted in two areas of the lake. Seven fish species were sampled from the lake. These include Coregonus clupeaformis

(lake whitefish), Prosopium cylindraceum (round whitefish), Salvelinus

fontinalus (brook trout), Salvelinus namycush (lake trout), Esox lucius

(northern pike), Catostomus commersoni (white sucker), and Lota lota

(burbot). White sucker was the most abundant species, contributing 25.0%

by number and 24.3% by weight of the total sample. TABLE OF CONTENTS

Page

LIST OF FIGURES...... ii

LIST OF TABLES ••••• ...... iv

LIST OF APPENDICES.. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• vi

INTRODUCTION •••••••••••• ...... 1

DESCRIPTION OF THE STUDY AREA.... • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 2

}1A.TERIALS AND METHODS.. . . • . • . .. • • ...... • . • . . • . • • • • • . .. . . • • . • • . • • . • • 5·

RESULTS AND DISCUS SION. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 9

s~y ••••..•.. II ••••••••••••••••••••••••••••• , • • • • • • • • • • • • • • • • • • •• 65

ACKNO~EDGMENTS •••• , •••••••••••••• It • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 70

REFERENCES • ...... , ...... , ...... 71 APPENDIX ••• ...... 74

i LIST OF FIGURES

Figure Page

1. Ten Mile Lake in relation to Smallwood Reservoir, Labrador ...... 41. • • • • • • • • • • • • • • • • • • • • • • •• • • • • • • • • • • •• • • • 3

2. Bathymetric map of Ten Mile Lake ••...... ••.••••.•.•.•. 6

3. Locations of gillnets and trap nets, and of the sampling stations for plankton and water quality •...•.•.•.••.•••••• 7

4. Temperature profile showing thermocline in two areas of Ten Mi Ie Lake...... 11

5. Dissolved oxygen profile showing chemocline in two areas of Ten Mile Lake...... 12

6. Fish-length to scale-length relationship for lake white fish from Ten Mile Lake ...... 20

7. Comparison of growth rates for lake whitefish from Ten Mile Lake and Jacopie Lake, Labrador .•..•••••••••.•••••••• 23

8. Fork-length distribution of lake whitefish •••••••••••••••• 24

9. Age-composition of lake whitefish from Ten Mile Lake •••••• 24

10. Fish-length to scale-length relationship for round white fish from Ten Mile Lake...... 28

11. Comparison of growth rates for round whitefish from Ten Mile Lake, Labrador, and the Ungava area •••.•..••.•••.•.•• 29

12. Fork length distribution of round whitefish from Ten Mile Lake...... 31

13. Age composition of round whitefish from Ten Mile Lake ••••• 31

14. Fish-length to scale-length relationship for northern pike from Ten Mile Lake...... 36

15. Comparison of growth rates of northern pike from Ten Mile Lake and Jacopie Lake, Labrador...... 38

16. Length distribution of northern pike from Ten Mile Lake

•••••••••••••••••••••••••••••••••••••••••••••••••••••• l1li ••• 40

17. Age composition of northern pike from Ten Mile Lake ••••••• 40

18. Comparison of the growth rates of lake trout from Labrador and other northern Canadian lakes...... 45

ii Figure

19. Length distribution of lake trout from Ten Mile Lake •••••••• 46

20 . Age composition of lake trout from Ten Mile Lake •••••••••••• 46

21. Comparison of growth rates of brook trout from Avalon Peninsula of fiel,ffoltndland, and t~vo areas of La brador ••.•.••• 52

22. Length distribution of brook trout from Ten Mile Lake ••••••• 53

23. Age composition of brook trout from Ten Mile Lake ••••••••..• 53

24. Fish-length to scale-length relationship for white suckers from Ten Mi Ie Lake...... 58

25. Comparison of growth rates for white suckers from Ten Mile Lake and the Mac Kenzie River a rea. . • • • • • • • • • • • • • • • • • • • • • • • •• 59

26. Length distribution of white suckers from Ten Mile Lake •••••• 60

27. Age composition of white suckers from Ten Mile Lake ••••••••• 60

iii LIST OF TABLES

Table

1. Morphometry of Ten Mile Lake, Labrador ...... •...... •.•.•. 9 2. Water quality analysis from two selected stations and one deep hole on Ten Mile Lake. (Samples collected during June and July, 1974) ...... 14

3. Check-list of plankton species identified in Ten Mile Lake,

1974 ...... 1,.".,1 •••••••••• II •••• II ••• '" ••••••••• II i6

4. Mean scale length and calculated fork length at annulus formation of lake whitefish from Ten Mile Lake •••.••.••••••• 21

5. Stomach contents of lake whitefish from Ten Mile Lake •.••••• 25

6. Mean scale length and calculated fork length at annulus formation of Ten Mile Lake round whitefish •••.•••••••••••••• 30

7. Comparison of weights for round whitefish from the

different lakes ...... 01 ...... 0 •••••••••••••••• 32

8. Stomach content analysis of round whitefish from Ten Mile Lake...... • .. • ...... • . .. • .. • . .. • .. .. • . . • • • .. • • • • • • . • • • • .. .. • . • • • • •• 33

9. Mean scale length and calculated fork length at annulus formation of northern pike from Ten Mile Lake ••..•••••.•..•• 37

10. Stomach content analysis of northern pike from Ten Mile

Lake ...... f • • .. .. • .. • • • • • • • • • .. • • • • • • • • • • • .. • • • • .. • • •• 41

11. Mean scale length and calculated fork length at annulus formation of lake trout from Ten Mile Lake .•...... •.••.•.•. 44

12. Stomach content analysis for lake trout from Ten Mile Lake

...... II ...... 48 13. Mean scale length and calculated fork length at annulus formation of brook trout from Ten Mile Lake •...••...••••.... 51

14. Stomach content analysis for brook trout from Ten Mile Lake

...... o!I • .. • • •• 54

15. Mean scale length and calculated fork length at annulus formation of white suckers from Ten Mile Lake •...•..••••••.• 56

16. Stomach content analysis for white suckers from Ten Mile Lake ...... 61

iv Tab1e~' Page

17. Percent number and weight of each species taken from Ten Mile Lake, Labrador, 1974...... 64

v LIST OF APPENDICES

1. Conversion of conductivity values to T.D.S •••.•.••••••••.. 74

2. Temperature readings for Ten Mile Lake (June-July, 1974) 75

vi INTRODUCTION

A limno1ogica1 and fish inventory study of Ten Mile Lake was con

duct d during t he summer of 197 4 . This study is part of a detailed,

long-term program initiated by the Resource Deve l opment Branch i n 197 3,

designed to evaluate the fiah and wa t er resources of i nland La brador.

Th e objectives of this study were three-fold. It marked the first

t ime that any Unatural" waters of Labrador were i nvestigated in terms of physical, chemica l and bi otic parameters. This study would also be the

basis for compar ison of s t udies done on the already flooded Smallwood

Reservoir. Since there we r e no baseline studie s done on the lakes which now constitute the reservoir , we can only extrapolate f r om the data now available from Ten Mi le Lake, being in the vicinity and not affected by

flooding. The data obtained will also be useful for comparison with the waters and f ish resources on insular Newfoundland. -2

DES CRIPTION OF THE STUDY AREA

THE LAKE

Ten Mile Lake (Fig. 1) is situated approximately 32.9 km northwest

of the town of Churchill Falls at a latitude of 53°43' North and a

longitude of 65°05' west. The lake has an elevation of approximately

457 m above sea level. The drainage area for the lake is approximately 2 46.3 km . most of which is small bogs; marshes and streams. The major

inlet to the lake is Brook 61, (Fig. 2) flowing from the southwest. The

major outlet is a large brook in the extreme western end of the lake.

Ten Mile Lake is a typical glacial lake , very irregular in shape and

including 268 islands.

Geographic Situation: Ten Mile Lake is one of the thousands of

lakes on the Labrador Plateau. The Plateau forms the eastern section of

the Canadian Shield which extends across much of the northern portion of

the continent. The bedrock, which is widely visible in this area, is of archaen granites and gneisses, dating back to the Cambrian era,

Climate: The average annual precipitation for the Churchill Falls area is 760 rom (30"), made up 0 400 rom (16") of rain and 4,000 rom (154") of snow. the mean daily temperature for the month of January is -23C and

for the month of July is l3.6C. The extreme temperature for winter is

-48C and 30C for summer (CFLCO News Service Fact Sheet),

Vegetative Cover: Most of the surrounding area is forested with a mixed stand of tamarack,white spruce, and black spruce, Other species ,

LOCATION L -,Ir MAP

I W LOBSTICK I LAKE

.--. ------

o 25 50 ! ' I OSSOKMANUt(N SCALE OF KMS. RESERVOIR

CHURCLILL RIVER

F IG . 1 T E N M I LE L AKE I N RELATION TO SMALL WOOD RESERVOIR , LABRADOn . -4

in the area include balsam fir, trembling aspen , balsam popular, white birch and mountain ash.

Numerous shrubs, berries and mosses , including the widespread caribou moss, provide the basic ground cover. Goldenrods and fireweeds are the most common wildflowers.

Wildlife: The low productivity of the area , due to both the nature of the soi1 and the short growing season, limits the population of large mammals. (Sheppard T. Powell Assc. Ltd., 1971). !he major fur bearing inhabitants of this region include muskrat, mink, beaver, red squirrel, otter, martin, red and Arctic fox, black bear, wolverine, porcupine, caribou and timber wolf.

The chief game birds include Canada goose, black duck, pintail, teal, golden eye, willow ptarmigan and spruce grouse. Non-game birds which next in the area include the common loon, Arctic tern, gulls, ospreys, owls, bald eagles and many species of small song birds. -5

MATERIALS AND METHODS

Physical and Chemical Studies

Ou tline maps were traced and enlarged from a topographical map published by the Department of Mines and Technical Surveys. Depth soundings of the lake were made using a Benmar DR-25 model depth recorder.

A bathymetric map was constructed using the information collected from the dept h recordi ngs (Fig. 2). Additional morphmetric parameters were calcu lated using me thods outlined by Welch (1948).

Selected physical and chemical parameters of the water were monitored at t hr ee different stations in the lake (Fig. 3), Surface water tempera tures of the lake were recorded by a Ryan thermagraph from June 26 to

J uly 27 . Water temperatures from two deep depressions in the lake bottom were a l so recorded (Fig, 3). Dissolved oxygen concentrations were mea sured using the modified Winkler method. Analysis of water samples t aken during July, 1974, was carried out by the Laboratory Services Unit of the Water Resource Group, Resource Development Branch, St. John's,

New foundland.

Biological Studies

The fish were sampled with a variety of gear including gillnets, lake trap nets and minnow traps. Fishing stations were selected to en sure that as great a variety of areas as possible were sampled (Fig. 3).

Most of the fish sampled were taken with gillnets. These nets were in gangs composed of five nets, each 36.7 m in length, giving a total length of 233.6 m. Each gang was composed of a 3.8 cm, 5.1 cm, 7.7 cm, r--- -6 ...... ~------.... ~..

?~ -fi/#

\~\'\- .-C?... , \

-- til

. ~ ....

CI'fUAC .... 'll F~ ll _ S -

TE N MILE LAKE

Sea Ie 1 em :::: O. 31 km

Fig. 2. BathYmetric map of Ten Mile Lake. \ ,

KEY S Surface net , • • B Bottom net .. ,- T Trap net .. ., Sampling stati~ I • -.I B • • •D Deep sample.. - I '.. ~. 0' I I ~. ~ - ~. ~".,'I.."" ~ .-. ~~ _ S ~. S"/II."

_ _ _ .... B # .; S· ' , ~ :.;,.t,:..'" . - ,.,tL" .- . .I'f!':' -, - ... '.... ~ II ~~'.. . ,~ .. . " ~ • ~" ••& . ,. ~ " ~ ..

TEN MILE LAKE

Scale 1cm'0.6 km.

Fig. 3. Locations of gillnets and trap nets, and of the sampling stations for plankton and and water quality, 10.2 cm, and a 12.8 cm stretched mesh gi1lnet. Each gang was allowed to f ish overnight before being hauled. A total of 19 sets were made, 10 floating sets and 9 sunken sets. A trap net was fished for 9 nights.

At the completion of each set, records were made of the total catch of individual species according to mesh size and location of net, surface or bottom. The fish collected were used to calculate age and growth information plus other population parameters. Each fish was weighed to the nearest 10 g, and measured to the nearest mm. Scale samples (and otolith samples in the case of burbot) were removed for later age determination. Stomach samples were preserved in 1~1a formalin for food habit studies in the laboratory. Fish were examined for sex and stage of maturity by examination of gonads.

Plankton samples were taken at sampling stations 1 and 2. A plankton net with a 15.24 em opening and number 20 bolting silk was used.

These plankton samples were preserved in 5% formalin for later identification. - 9

RESULTS AND DISCUSSION

Physical and Chemical Environment

Morphometry: A bathymetric map, which was drawn from 88 sounding transects, is presented in Figure 2. The morphometric parameters for the lake are given in Table 1. 2 The area of ten Mile Lake is 30.3 km , of which the 268 islands 2 account of 3.91 km. The very irregular shape of Ten Mile Lake results in shoreline development index of 3.84.

Table 1. Morphometry of Ten Mile Lake, Labrador.

Ma ximum length 11.42 km

Maximum effective length 7.10 km

Maximum width 4.81 km

Maximum effective width 2.78 km

Mean width 2.64 km

Maximum depth 18.30 m

Mean depth 2.90 m

Mean depth-maximum depth relationship 0.16 m

Direction of major axes ESE-WNW 2 Area of lake including islands 30.30 km 2 Area of islands 3.91 km 2 Area of lake excluding islands 26.39 km

Shoreline length 74.96 km

Shoreline length including island shorelines 196.91 km

Shoreline development 3.84 Table 1 (cont'd.)

Number of islands 268 . 3 Volume of lake 75,525,000 m

Lake area for water less than 6.0 m deep 93.6%

Temperature: Ice-out in Ten Mile Lake occurred the first week of

June and freeze-up occurred in early October.

Changes in water temperature during the working period are shown in

Appendix 1. The lowest surface water temperature during this period was

13.8 C and the highest was 21.1 C.

A pronounced thermocline was observed in two different areas of the lake where a vertical temperature profile was taken on August, 1974. The temperature curves for these thermoclines are shown in Figure 4. No other thermal stratification was observed in the lake. The shallowness of the lake combined with normal wave action seemed to be sufficient for complete mixing of the lake waters.

Dissolved Oxygen: During the study period the lowest dissolved oxygen concentration observed was 9.01 ppm. which represents a 91% saturation. Oxygen concentrations remained virtually unchanged with depth except in the cases observed in the two deep depressions of the lake (Fig. 5). In both of these depressions an oxygen deficit was observed in the bottom 4.5 meters.

Water Quality Analysis: With the exception of the two deepest depressions in the lake, analysis of water samples showed very little -11

2 Area No.1 Area No.2 • • 3

4 I

5 j ./

././//

./ 6 ...... -_/ U> - 7 r/ - a: w t- I w / ~ 8 Z I f I I t- 9 Cl.. ~ w I 0 I 10 , I 11 +I 12 ~ I 13 , I 14 +I

15 +I 16 •

2 4 6 8 10 12 14 16 18 20 22 24

TEMPERATURE (OC)

Fig.4 Temperature profile showing Thermocline in two areas of Ten Mile Lake. -12

Area No.1 2 .... -----~ Area No.2 • • 3

I 6 /) // / CJ) ./ / CI: 7 UJ ~ / I / UJ / ~ / 8 , Z / / I / I a.. 9 UJ ? 0

12 / I 13 , I I 14 ~ / / 15 1 I 16 ~

1 2 3 4 5 6 7 8 9 10 11 12

DISSOLVED 02 (p.p.m.)

Fig .5 Dissolved oxygen profile showing Chemocline in two areas of Ten Mile Lake. -13

variation in the chemical properties within different parts of the lake

(Table 2). The chemoc1ine that was detected in the depressions is

probably due to the lack of mixing and the significantly colder tempera

ture of the water in these depressions.

Measurements of pH in Ten Mile Lake were within the range of 6.0

to 6.6, the average being 6.35. The mean specific conductance value

(14.20) calculated from sampling stations 1 and 2 is considerably lower

than the mean value (38.0) for 354 Newfoundland lakes and rivers.

Specific conductance values were converted to total dissolved

solids (T.D.S.) by the formula given in Appendix 2. T.D.S. values are

used in calculating the morphoedaphic index (T.D.S./mean depth) of a

lake in a formula formulated by Ryder (1965). This morphoedaphic index

is used for estimating the fish production in north temperate lakes. A

rapid approximation of the productivity can be obtained by solving the

equation: Y = 2~ where X represents the morphoedaphic index, and Y

is the productivity in kg/hectare/yr.

An estimated potential fish yield of 2.64 kg/hectare/year is

indicated by combining the chemical and morphometric data on Ten Mile

Lake. This compares more favourably with the estimated production of

Smallwood Reservoir which is 2.23 kg/hectare/year; but slightly less

than the estimates for the smaller lakes in Newfoundland which yield an

average of 4.03 kg/hectare annually. Since the level of dissolved nutrients for Ten Mile Lake is much lower than the average nutrient level

of the natural lakes on the island, it would seem that its shallow

nature tends to compensate for this and results in a relatively

moderate level of fish production. Table 2. Water quality analysis from two selected stations and from one of the deep depressions on Ten Mile Lake. (Samples collected during June and July, 1974.

Conduc tivity Total Total @ 25°C Alka- Tur- Station pH Hardness ( mhos/em) T.D.S. linity bidity Ca + Cl+

If 1 Surface 6.3 6.0 14.1 17.2 4.3 1.3 1.1 0.8

If 1 Bottom 6.0 6.0 14.6 17.5 5.0 3.2 1.0 0.7

If2 Surface 6.5 6 . 0 14.6 17 • 5 4.3 1.0 1.3 0.7

If2 Bottom 6.3 6.5 13.5 16.7 4.0 1.7 1.1 0.7

Deep Hole 6.0 12.0 23.6 24.0 8.0 1.2 2.0 0.7

PLANKTON

Phyloplankton: Only the most common phytoplankton were identified

(Table 3). They were; Tabellaria fenestrata, Asterionella formosa,

Dinobyron divergens, E. bavaricum, and Uroglenopsis americana.

The diatoms, ~. formosa and T. fenestrata were also reported as

being very common in the Churchill Falls region by Duthie and Ostrofsky

(1974). The three remaining phytoplankton are Chrysophytes. Both D.

divergens and E. bavaricum are considered common to this area, however,

no mention was made of U. americana occurring in the areas studied by

Duthie and Ostrofsky (1974).

Zooplankton: Two taxa of Protozoa were identified from the

samples (Table 3). Epistylis rotans was identified in only one sample,

while Vorticella sp. was noted in three different samples.

Eight taxa of Rotifers were identified (Table 3). They were well -15

represented throughout most samples.

The crustaceans, 9 cladocerans and 3 copepods, constituted the bulk of the taxa identified. Most species were well represented throughout the samples, with the exception of Daphnia catawba. The presence of this species is questionable since it was based on the identification of one individual. Cydorus sphaericus was identified in only one sample as well; however, there were sufficient individuals to confirm the identification.

The composition of the plankton identified, indicate that the taxa of Ten Mile Lake is typical for the dilute waters of the Precambrian

Shield. Duthie and Ostrofsky (1974) studied the plankton from several bodies of water in the Churchill Falls area and reported a total of 44 taxa. All plankton mentioned here with the exception of Uroglenopsis americana, Kellicottia bostoniensis and Daphnia catawba were reported from their study. Table 3. Check-list of pl ankt on species identified in Te n Mile Lake, 1974 .

Samp l e number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Sampl i ng station 1 1 2 2 2 * 2 2 2 2 1 1 1 1 2 2 Date collected 29/6 29/6 29/6 29/6 29 /6 29/6 7/7 7/7 7/7 7/7 7/7 7/7 18/7 18/7 18/7 18 /7 Water Temp.(OC) 16.6 16.6 15.8 15.8 15 .8 16.6 16.6 16.6 16.6 16.6 16.6 16.6 15. 4 15. 4 15.3 15.3 Sampling depth Surf Surf Surf Surf I- 2m I - 2m Surf Surf I-2m I-2m Surf Surf Surf Surf Surf I-2m

Common Ph~toplankton Tabe11aria fenestrata X X X X X X X X X X X X X X X Asterionella formosa X X Dinobryon divergens X X X X X X X X X X X X X Uroglenopsis americana X X X X X X X X X X X X X X X

Dinobr~on Bavaricum X X X X X X X X X X X X

I Protozoa I-' 0\, Epistylis rotans X

Vorticella ~ X X X

Rotifera Asplanchna..M> . X X X X X X X X X X X X X X X Conochiloides ~ X X X X Conochilus unicornis X X X X X X X X X X X X Kellicottia bostoniensis X X Kellicott:l,a longispina X X X X X X X X X X X X X X X Keratella cochlearis X X X X X X Polyarthra spp. X X X X X X X X X

Trichocerca ~. X X X X * Sample number 6 br oken. Table 3. (cont'd.)

Sample number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Sampling station 1 1 2 2 2 * 2 2 2 2 1 1 1 1 2 2 Date .:o11ected 29/6 29/6 ?9/6 29/6 29/6 29/6 7/7 7/7 7/7 7/7 7/7 7/7 18/7 18/7 18/7 18/7

Water temp (C) 16.6 16.6 15.8 15.8 15,8 16.6 16.6 ~6.6 16.6 16.6 16.6 16.6 15.4 15.4 15.3 15.3 Sampling depth Surf Surf Surf Surf 1-2m I-2m Surf Surf 1-2m I-2m Surf S·lrf Surf Su.:f Surf 1-2m

C1adocera Bosmina coregoni X X X X X X X X X X X X X X Chydorus sphaericus X Daphnia ga1eata mendotae----- X X X X .Daphnia longiremis X X X X X X X X X X X X X X

Daphnia pulex X X X I I-' -...J Daphnia catawba (?) X I Holopedium gibberum X X X X X X X X X X X X .X X X

Polyphemus ~dicu1us Sida crystal1ina X

Copepoda Epischura lacustris X X X X X (" Epischura (juveniles) X X X X l

Diaptomis minutu~ X X X X X X X X X X X X X X X Diaptcmis (Naup1ii) X X X X X X X X X X X Diaptomis (juveniles) X Cyclops scutifer X X X X X X X X X X X X X X Cvclopoid (naup1ius) X X X X X X X X X X X X Cyclopoid (juvenile) X -18

FISH SPECIES:

Whitefishes - family salmonidae

Lake whitefish - Coregonus clupeaformis (Mitchill)

Lake whitefish is widely distributed throughout North America. In

Canada, it occurs from New Brunswick and Labrador westward to British

Columbia the Yukon and the Northwest Territories (Scott and Crossman,

1973). The lake whitefish is indigenous to Labrador and constitutes one

of the most abundant freshwater fishes of that area. The greatest con centration of whitefish populations is in the north-western and central

sections of Labrador. ~9-

The lake whitefish prefer cool waters, as observed by higher catch

r eturns in the deeper net sets of Ten Mile Lake. In the fall, whitefish

move into shallow water to spawn. They do not construct a redd as do

other salmonids, but rather, release their eggs more-or-less randomly

over the spawning grounds. The eggs remain on the spawning grounds until

they hatch in April or May (Scott and Crossman, 1973).

Adult lake whitefish are bottom feeders over most of their range,

consuming a wide variety of invertebrates and small fishes. The young

feed mainly on planktonic crustaceans (Reckahn, 1970).

BACK-CALCULATION OF GROWTH

Van Oosten (1923) and Hogman (1968) have previously shown that

scales may be used to age lake whitefish. The Lee method (Lagler, 1952) of back-calculation which assumes a constant ratio in body and scale

increments was used in this study.

A plot of the average fish lengths against the average scale diameters indicated that the data were best described by a straight line Figure 6. The equation for the line fitted by least squares is:

L = 1.42 Ls + 6.27 correleation coefficient (r) = 0.86. f The average scale lengths for each year of life and the corresponding calculated fish lengths are given in Table 4 and presented in Figure 7.

The growth rate is slightly faster than that reported by Hatfield et al. (1972) for the MacKenzie River Valley and Quadri (1968) for Lac

Ie Ronge, Saskatchewan. However, it is comparatively slower than rates given for southern regions. (Scott and Crossman, 1973). In comparison with Jacopie Lake Whitefish of the Smallwood Reservoir (Bruce, 1974) the -20

34 E u :::I: 30 ~ (!) Z w -l 26 :::..::: a: 0 22 LL.

0 3 6 9 12 15 18 21 24 27 30 33 36

SCALE LENGTH (em)

Fig.6 Fish length - scale length relationship for Lake Whitefish from Ten Mile Lake. Table 4. Mean scale length and calculated for k length at annulus formation of l ake whitefish from Ten Mile Lake.

Annulus I II III IV V VI VII VIII IX X XI XII XIII

Scale length (cms) 3.7 8.5 12.4 15.9 18.5 20.4 22.4 24.6 26.4 27.8 28.7 30.3 32.8

Fork length (cms) 11.6 18.3 23.8 28.8 32.5 35.2 38 . 4 41. 2 43.7 45.8 47.0 49.4 52.8

I N ...... I -22

growth rate is slightly faster as shown in Figure 7.

LENGTH DISTRIBUTION AND AGE COMPOSITION

The length distribution of whitefish from Ten Mile Lake is pre

sented in Figure 8. The total mean fork length for the sample was 42.0

cm with a range of 14.9 cm - 52.0 cm. There was no significant

difference between the male and female mean fork lengths.

Approximately 9ato of the fish sampled were over 33 cm in fork

lengths.

The age composition for lake whitefish from Ten Mile Lake is pre

sented in Figure 9, 61.3% of the sample is VIII + years or older. The

oldest fish taken was XIII + years but the largest fish was X+ years with

a fork length of 53.0 cms .

. LENGTH-WEIGHT RELATIONSHIP

The length-weight relationship for lake whitefish is expressed by

the equation:

Log W = 3.04 LogL - 4.91; correlation coefficient (4) = 0.98.

Where W is the weight in grams and L is the fork length in centi

meters. The value of the exponent "b" (3.04) corresponds well with that

of 3.14 reported by Bruce (1974) for JacopieLake, Labrador. In similar

latitudes of western Canada Hatfield et a1. (1973) reported "b" values

of 3.247 and 3.243. There was no significant difference between the mean

weight of the males and the females.

Sex Ratio: The male to female ratio of lake whitefish samples was

1.45:1. There were seven immature fish in the sample. 55

Ten Mile Lake ••.-----~•• 50 Jacopie Lake e------e (Bruce. 1974)

E u 35

I r- c.::J 30 Z l.U ...J

~ 25 a: 0 u. 20

1 2 3 4 5 6 7 8 9 10 11 12 13

AGE (YEARS)

Fig .7 Comparison of growth rates for Lake Whitefish from Ten Mile Lake and Jacopie Lake, Labrador. -24

30 I-

> u z U.J => 20 d UJ a: IJ.. t- Z U.J U 10 - a: U.J a..

13.55 17.55 21 .55 25.55 29.55 33.55 37.55 41 .55 45.55 49.55 53.55

FORK LENGTH (em)

Fig.8 Fork length distribution of Lake Whitefish.

30 r

> U Z U.J => 0 20 I- U.J a: IJ.. t- Z U.J U a: 10 I- U.J a..

I I I I 1 2 3 4 5 6 7 8 9 10 11 12 13

AGE (YEARS)

Fig.9 Age composition of Lake Whitefish from Ten Mile Lake. - 25

Food Habit s: Seventy lake whitefish stomachs were analyzed for food contents. Eighty-one percent of the stomachs were full and none of the stomachs were empty. Stomach analysis indicated that the whitefish were primarily benthic feeders. The three most commonly occurring food items were immature Dipterans (100%), Hydracarina (97.1%) and gastrapoda

(601'0) (Table 5).

Table 5. Stomach contents of lake whitefish from Ten Mile Lake.

Sample number: 70 Average condition: 9OO'{' full Number of stomachs empty: 0 Percentage Food Item Frequency Occurrence Trichoptera 25 35.7 Ephmeroptera 12 17.1 Diptera 70 100.0 Amphipoda 1 1.4 Hirudinea 1 1.4 Hemiptera 21 30.0 Colec?tera 2 2.9 Hydracarina 68 97.1 Pelecypoda 40 57.1 Gastrapoda 42 60.0 Detritus 58 82.9 -~-

Round Whitefish - Prosopium cylindraceum (Pallos)

The distribution of round whitefish is not continuous across Canada as is the lake whitefish. In Canada it ranges from northern New

Brunswick into Labrador and Ungava and westward into parts of Quebec,

Ontario and the Great Lakes except for Lake Erie. The distribution is discontinuous throughout the southern and central portions of the remaining western provinces but is reported in the far northerly portions of these provinces as well as the Territories and Yukon (Scott and Crossman,

1973). -v-

The round whitefish is a cold water species. In the northerly extent of its distribution it can be found in ponds, rivers and streams

but in the more southerly parts of its range, the round whitefish is usually found in deep lakes. Spawning takes place in the fall of the year over the gravelly shallows of lakes, at river mouths or occasionally in rivers. Round whitefish, feed primarily on benthic invertebrates including trichopterans, plecopterans and dipterans (Scott and Crossman,

1973).

Age Growth: Ageing of round whitefish was done through scale examination. The average scale diameter of 84 fish was plotted against the corresponding fish lengths, (Fig. 10) indicating that the Lee method of back-calculation was suitable for this study. The relationship between scale size and fish length is described by the equation:

L ; 2.87 (Ls) + 8.37; correleation coefficient (r) 0.93. f = Round whitefish from the Ungava area (Koksoak et al. 1968) displayed a slightly slower growth rate (Fig. 11). However, the growth rate in

Ten Mile Lake (Table 6), is substantially slower than in other northerly lakes described by Rawson. (1951) and Kennedy, (1949).

The oldest and largest fish taken was XIII + years with a fork length of 33.0 cm.

LENGTH-DISTRIBUTION AND AGE COMPOSITION

Figure 12 presents the length distribution of round whitefish from

Ten Mile Lake. The total mean fork length was 24.9 cm with a range of

14.7 cm to 33.0 cm. The mean fork length for the female whitefish was

25.9 cm, which was 2 cm longer than the mean fork length of the males. -28

32 30 • 28

E (.) 20 J: • ~ <.9 18 Z w ....J ~ 16 0:: 0 u. 14

o 2 4 6 8 10 12

SCALE LENGTH (em)

fig .10 fish length - scale length relationship for Round Whitefish from Ten Mile Lake. - 29

Ten Mile Lake • • Ungava Area ...------e 30 (Koksoak et ai, 1963) J' / / / 28 / / /

26 ./ / ./ / / '" 24 / / / // '. 22 / / / -- ./ 20 , ./ / ./ E / u / 18 / :::x:: ,. I / ./ (9 ./ Z 16 / w / .....J ~ • a: 14 0 ~

o 1 2 3 4 5 6 7 8

AGE (YEARS)

Fig,11 Comparison of growth rates for Round Whitefish from Ten Mile Lake, Labrador and the Ungava Area. -30

Fifty-five percent of the round whitefish in this sample are 24.55 cm or larger (Figure 12).

Figure 13 presents the age composition of the Ten Mile Lake round whitefish sample.

Ninety percent of the sample is between three and six years old.

Table 6. Mean scale length and calculated fork length at annulus formation of Ten Mile Lake round whitefish.

Annulus I II III IV V VI VII VIII

Scale length (cm) 1.4 3.0 4.3 5.1 5.9 6.2 7.3 8.3

Fork length (cm) 12.3 16.9 20.6 23.1 25.3 26.3 29.3 32.2

LENGTH-WEIGHT RELATIONSHIP

The length-weight relationship for round whitefish is expressed by the equation:

Log W = 3.39 Log L - 2.57; correlation coefficient (r) = 0.95.

The whitefish of Great Bear Lake (Kennedy, 1949) and Great Slave Lake

(Rawson, 1951), are comparatively heavier fish than those from Ten Mile

Lake (Table 7). -31

>- 25 - U Z UJ ::> 20 - 0 UJ a: LL 15 ~ ~ Z UJu a: 10 UJ a..

5 -

14.55 16.55 18.55 20.55 22.55 24.55 26.55 28.55 30.55 32.55 34.55

FORK LENGTH (em)

Fig.12 Fork length distribution of Round Whitefish from Ten Mile Lake.

30 > U Z 25 UJ ::> 0 UJ 20 a: LL

~ Z 15 UJ U a: UJ a.. 10

I 1 2 3 4 5 6 7 8

AGE (YEARS)

Fig.13 Age composition of Round Whitefish from Ten Mi Ie Lake. -32

Table 7. Comparison of weights for round whitefish from three different lakes.

Weight of round whitefish in ~rams Fork Ten Mile Lake Gt. Bear Lake Gt. Slave Lake length ( cm) Labrador N.W.T. N.W.T,

20 69 85

25 148 250.0 200

30 275 350.0 340

35 457 465.0 570

40 724 650.0 880

Sex Ratio: the sex ratio, female to male was 1.27 to 1. Two

i mm ature fish were collected from the sample.

Food Habits: Seventy-five stomachs were analyzed for a

qualitative food occurrence study. Thirty-three percent of the

stomachs were full and ten percent were empty.

Table 8 shows the complete analysis of food items found in the

stomachs. Table 8. Stomach content analysis of round whitefish from Ten Mile Lake.

Sample number: 75

Average condition: 50/0 fulJ

Number of stomachs empty: 8

Food item Frequency Percentage Occurrence

Odonata 1 1.5

Trichoptera 45 67.2

Ephmeroptera 1 1.5

Diptera 29 43.3

Hemiptera 1 1.5

Coleoptera 4 6.0

Hydracarina 16 23.9

Pe1ecypoda 4 6.0

C1adocera 1 1.5

Insect remains 6 9.0

Gastrapods 8 11. 9

Detritus 21 31.3 -3 4

Family Esocidae - Pike

Northern pike - Esox lucius (Linnaeus)

The northern pike has a circumpolar distribution in the northern hemisphere. In Canada it is found in all provinces and territories except the Maritime provinces and insular Newfoundland.

Pike usually inhabit ponds and warm, slow-moving water, that is heavily vegetated. However, they are found in a wide range of habitats over the whole of their distribution (Scott and Crossman, 1973).

The pike are spring spawners and usually spawn immediately after the ice melts. They spawn during daylight hours on the heavily vegetated -35

foodplains of rivers, marshes and bogs of larger lakes. Egg population

in the female pike has been estimated at 9,OOO/pound of female. The

eggs usually hatch in 12-14 days with an estimated 9~o mortality. (Scott

and Crossman, 1973).

Pike could be classed as an opportunistic feeder in that it feeds on

whatever is available. They feed most heavily on fish but other small

vertebrates such as mice, ducklings, frogs and muskrats are often

consumed.

BACK-CALCULATION OF GROWTH

The lIS pike in this sample were aged through scales. Frost and

Kipling (1959), however, found that ageing pike through the opercular

method was more reliable.

The Lee method of back-calculation was successfully used in this

study.

A plot of the average fish length against the average scale diameter

indicated the data is best described by a straight line (Fig. 14), th€

equation for the line fitted by least squares is:

L = 4.27 Ls - 1.57; correlation coefficient (r) = 0.91. f The mean scale length for each year of life and the corresponding calculated fish length is given in Table 9, and presented in Figure 15.

The calculated growth rate is quite similar to that reported for

Smallwood Reservoir, Labrador (Bruce, 1974), and for other northern parts of Canada, (Hatfield et al. 1972; Miller and Kennedy, 1948).

However, pike from the more southerly regions display a much faster growth rate (Rawson, 1932; Wainio, 1966). 100

E u - 60 I ~ (!;) Z W -I 50 ~ a:: 0 u. 40

2 0

o 2 4 6 8 10 12 14 16 18 20 22

SCALE LENGTH (em)

Fig .14 Fish length - scale length relationship for Northern Pike from Ten Mile Lake. -37

Table 9. Mean scale length and calculated fork length at annulus formation of northern pike from Ten Mile Lake.

Calculated Annulus Frequency Scale length (cm) fork length (cm)

I 0 2.2 7.8

II 1 5.1 20.2

III 0 7.8 31.7

IV 9 10.2 41.9

V 14 12 . 2 50.5

VI 31 13.8 57.3

VII 11 14.6 60.8

VIII 18 15.5 64.6

IX 3 15.5 64.6

X 5 16.2 67.6

XI 3 16.6 69 . 6

XII 2 16.8 70.2

XIII 2 17.1 71.4

XIV 0 17.0

XV 0 17.4

XVI 0 17.7

XVII 0 18.0

XVIII 0 18.2

XIX 1 18.5 -38

Ten Mi le Lake 70 • • Jacopie Lake (Bruce, 1974) 65

50 E u

:J: 45 I I (.!) / Z I I w 40 -' I / ~ a: 35 a / l.L. / / / 30 " ~

o 1 2 3 4 5 6 7 8 9 10 11 12 13

AGE (YEARS)

Fig .15 Comparison of growth rates of Northern Pike from Ten Mile Lake and Jacopie Lake, Labrador. - 39

LENGTH DISTRIBUTION AND AGE COMPOSITION

The length distribution and age composition of northern pike is pre

sented in Figures 16 and 17 respectively.

The mean total length as 62.33 ern with a range of 23.4-91.0 cm. The mean female length (64.32 cm) was larger than the mean male length

(60.12 cm).

One of the pre-requisites for an accurate back-calculation is a large sample size with good representation in each age group. This was not obtained in the case of northern pike. As a result the baek-ca1cu

1ated lengths for the VIII and IX age group were the same. The small sample number in all year classes beyond eight years renders the results less reliable than in previous year classes.

The oldest and largest pike taken was a female XIX + years with a fork length of 91.0 cm.

LENGTH-WEIGHT RELATIONSHIP

The length-weight relationship for 115 northern pike from this lake is expressed by the equation:

Log W = 3.13 LogL - 5.34; correlation coefficient (r) = 0.95.

The pike showed a slightly higher value of "b" than did pike from the

Smallwood Reservoir Labrador, (Bruce, 1974). Miller and Kennedy (1947) reported a similar growth rate (b = 3.17) for pike from four northern

Canadian lakes.

Sex Ratio: The female to male ratio was 1.75:1, two immature fish were collected. -40

30 I- > U Z UJ :::> 0 w 20 0: U. ~ Z UJ u a:: UJ 0 10

J 22.55 28.55 34.55 40.55 46.55 52.55 58.55 64.55 70.55 76.55 82.55 88.55 94.55

FORK LENGTH (em)

Fig .16 Length distribution of Northern Pike from Ten Mile Lake.

35 I

;- 30 ~ > U Z UJ :::> 0 w a:: 20 - u.. ~ r--- Z w u - ex: UJ 0 f- 10 ~ r---

r--- - ,....-, o ,--, I l J 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

AGE (YEARS)

Fig.17 Age composition of Northern Pike from Ten Mile Lake. -4 1

Food Habits: The stomachs of 81 northern pike were examined to determine food habits (Table 10), twenty-nine (3670) of these were empty.

Of the remaining S2 pike, Sl contained fish or fish remains and one stomach contained the remains of a mouse. Invertebrates occurred in only one stomach (1.970)'

Table 10. Stomach content analysis of northern pike from Ten Mile Lake.

Sample number: 81

Average condition: 50io full

Number of stomachs empty: 29

Food Item Frequency Percent Occurrence

Hirudinea 1 1.9

Whitefish 1 1.9

Lake trout 1 1.9

Burbot 10 19.2

Suckers 31 S9.6

Minnows 7 13. S

Pike 1 1.9

Fish remains 6 11. S

Mice 1 1.9 -42

Trout and salmon - Family Salmonidae

Lake trout - Salvelinus namaycust (Walbaum)

The lake trout is widely distributed across northern North America from Alaska to the Maritime provinces and from the Great Lakes to some of the Arctic Islands (Rawson, 1961). In Labrador it is most abundant in th~ larger lakes in the north-western and central sections.

Lake trout prefer water temperatures between 4-10 C (40-50 F).

Spawning takes place in the autumn, usually over large boulder or rubble -43

bottom of an inland lake. Depth for spawning varies considerably, but most often occurs at depths of less than 12 m, (Scott and Crossman, 1973).

Although these fish are mainly piscivorous they take advantage of almost any food available.

BACK-CALCULATION OF GROWTH

The sample of 115 lake trout were aged by scales. As with most trout populations, the relationship between body length and scale length was curvilinear. The Monastyrsky logarithmic method was used to fit the data and straighten out the regression.

Back-calculation of lengths was made from the equation:

Log L 0.875 Log Ls + 0.866; correlation coefficient (r) 0.74. f = = The average scale lengths for each year of life and the corresponding calculated lengths are given in Table 11 and presented graphically in

Figure 18.

The lake trout of Labrador have a slower growth rate than that reported for other populations of lake trout throughout northern Canada.

Rawson (1961), reported a fork length of 61.2 cm after eight years in

Lac la Ronge, Saskatchewan, whereas in Ten Mile Lake they only attain a length of 38.8 cm. Kennedy (1954), indicated that lake trout in Great

Slave Lake , N.W.T., attain a length of 48.8 cm after eight years of growth. -44

Table 11. Mean scale length and calculated fork length at annulus formation of lake trout from Ten Mile Lake.

Calculated Annulus Frequency Scale Length (cm) Length (cm)

I 0 0.8 6.0

II 0 1.7 11.7

I II 0 2.5 16.4

IV 1 3.4 21.4

V 1 4.4 26.9

VI 1 5.4 32.1

VII 2 6.1 35.7

VIII 5 6.7 38.8

IX 16 7.9 44.8

X 22 8.5 47.8

XI 18 9.0 50.2

XII 16 9.6 53.1

XIII 11 10.1 55.6

XIV 4 11.0 59.8

XV 3 12.2 65.5

LENGTH DISTRIBUTION AND AGE COMPOSITION

The length and age distributions of the lake trout are presented

in Figures 19 and 20. It is seen that 96% of the fish were larger than

42.5 cm, and 74% of the fish were 10 years or older.

The mean fork length was 52.6 cm, with a range of 19.0-75.2 cm.

The mean female length (55.4 cm) was slightly greater than the mean -45

68 !' Ten Mile Lake / Great Slave Lake • • / 64 (Kennedy. 1954) ..... ------e / Lac la Range , ------. (Rawson . 1961) / . / 60 / ~ / 56 / /

/ 52 • / , / , / ,, 48 r / - " / ,, " 44 ! / / / 40 , E , u / , / 36 I / I I f I <.9 ,,I / Z , / UJ I -l 32 , / ~ / a:: ,.," JI 0 28 . u... " / .// 24 , / / / 20 ,/ 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

AGE (YEARS)

Fig.18 Comparison of the growth rates of Lake Trout from Labrador and other northern Canadian lakes. -46

30 > U Z UJ :::> d UJ a::: LL 20 I Z UJ U a::: UJ a.. 10

I o I 18.55 24.55 30.55 36.55 42.55 48.55 54.55 60.55 66.55 72.55 78.55

FORK LENGTH (em)

Fi 9.19 Le ngth distribution of Lake Trout from Ten M i le Lake.

30 t

> U r Z UJ 20 :::> d - UJ a::: - t- LL I Z f0 UJ 10 U a::: UJ a.. r- f-

r- o I I I I ~ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

AGE (YEARS)

Fig.2O Age composition of Lake Trout from Ten Mile Lake. - 47

male length (51.5 cm). The largest lake trout taken which displayed

immature gonads was 48.1 cm.

LENGTH-WEIGHT RELATIONSHIP

The logarithmic relationship of length to weight for lake trout was:

Log W = 3.15 LogL - 2.27; correlation coefficient (r) = 0.97.

This "b" value of 3.15 is greater than that of 2.9157 as reported by Bruce (1974) for Smallwood Reservoir, Labrador, and greater than the value reported by Martin (1970) for Lake Opeongo, Onto However, they are not as heavy as similar size lake trout from Lac 1a Ronge,

Saskatchewan (Rawson, 1961) and Great Slave Lake, N.W.T., (Kennedy, 1954).

Food Habits: The stomachs of 70 lake trout were examined to determine the major food items in their diet. Sixty-eight lake trout

(97%) contained food remains. The highest incidence for a single food item was 94.1% occurrence of diptera pupae. Invertebrates were more pre dominant than fish remains (Table 12).

This is not in agreement with most other food studies of the lake trout (Rawson, 1961; Dryer et a1. 1965; Martin, 1970). However, it could possibly be a seasonal change, considering the abundance of aquatic invertebrates at the time of sampling. -4&

Table 12. Stomach content analysis for lake trout from Ten Mile Lake.

Sample number: 70

Average condition: 50% full

Number of stomachs empty: 2

Food Item Frequency Precent occurrence

Trichoptera 4 5.9

Ephmeroptera 23 33.8

Diptera 64 94.1

Hirudinea 8 11.8

Hemiptera 19 27.9

Coleoptera 5 7.4

Hydracarina 55 80.9

Gastrapoda 1 1.5

Detritus 21 30.9

Burbot 1 1.5

Suckers 3 4.4

Minnows 1 1.5

Unidentified fish 15 22.1 - 4~

Brook trout - Salvelinus fontinalis (Mitchill)

The brook trout are an endemic North American species, occurring mainly in the north east corner of the continent. They are widely dis tributed in the Maritime provinces, Newfoundland, Quebec and Labrador.

In the latter there is a heavy concentration of larger trophy size brook trout in the south-eastern and central sections.

Brook trout occur in clear, cool, well oxygenated streams and lakes. They tend to seek temperatures below 20 C (68 F) (Scott and

Crossman, 1973).

The fall spawning date varies with latitude and temperature. They -50

usually spawn in the gravel areas of shallow streams where they build redds in which they deposit their eggs. The eggs hatch during the late winter Dr early spring. (Scott and Cro~sman, 1973).

Br00k trout feed on a wide range of organisms. Aquatic insects

~sua11y constitute the basis of their diet, but shrews, mice, fish, frogs and algae are not uncommon.

BACK-CALCULATION OF GROWTH

B~ook trout can be accurately aged by means of scale examination

(Cooper, 1951; Alvord, 1953; and Allen, 1956). However, an accurate and reliable back-calculation is d~pendellt upon a sufficiently large sample number from which to obtain scale samples. The brook trout sample con sisted of Ll fish, although a larger sample would have been more favourable.

Plotting the fish lengths against the scale lengths resulted in a curvil~near relationship. The Monastryrsky logarithmic method was employed to straighten the regression.

Back-calculation was then made from the equation:

LogL = 0.78 LogS + 1.07; correlation coefficient (r) = 0.67.

The average scale lengths for each year of life and the corresponding calculated lengths are given in Table 13 and presented in Figure 21.

In comparison with brook trout from Jacopie Lake, Labrador (Bruce,

1974), these fish display a faster growth rate in the first three years but slightly slower in the last three years. However, in comparison with the mean growth rate for brook trout on the island (Wiseman, 1972)

Labrador trout grow much faster (Figure 21).

The oldest brook trout was VI + years; the largest was a V+ years old with a fork length of 49.0 cm. - 51

Table 13. Mean scale length and calculated fork length at annulus formation of brook trout from Ten Mile Lake.

Annulus I II III IV V VI

Scale length (cm) 0.9 1.8 2.8 3.6 4.5 5.1

Fork length (cm) 10.7 18.2 25.7 32.4 38.0 41.7

LENGTH DISTRIBUTION AND AGE COMPOSITION

The length and age distribution of the brook trout are presented in Figures 22 and 23.

The total mean length for the sample was 40.16 cm. The mean male length (43.1 cm) was greater than the mean female length (38.9 cm),

LENGTH-WEIGHT RELATIONSHIP

The general length-weight relationship for brook trout was:

Log W = 3.31 Log L = 5.46; correlation coefficient (r) = 0.98.

The value of the exponent (3.31) is higher than that calculated for brook trout of Jacopie Lake, Labrador (Bruce, 1974) and by Wiseman (1969) for several populations on insular Newfoundland.

Sex Ratio: The female to male ratio was 1.25:1. Only one fish in the sample displayed immature gonads (23.1 cm female).

Food Habits: Twenty-five brook trout stomachs were examined for content. Invertebrates constituted the diet of all trout except one in which fish remains were found (Table 14).

The three most commonly occurring food items were Hemiptera (aquatic bugs) Diptera (mosquito larvae and pupae) and Hydracarina (water mites). -52

......

...... "'" ~ r ..... ,.,;;; ' .. 40 Avalon Peninsula ...... ____~•• / ~~~ (Wiseman, 1972) / / ~~~ " / ~ Jacopie Lake / , (Bruce, 1974) .------. / / " " / / 3 5 Ten Mire Lake .------.... "// . / / / " I ~ / , / , , ~ 30 / ' I / / / ,I'" I,' E i/' u 25 /' :I: f" I / ~ ,1 Z ,1 UJ // -' ,'/ ~ 20 ,'/ o0:: ,'/ u... // fJI , / ,'/, 15 " / " / " / / " / /

I " / / 10 " / / / / tI

1 2 3 4 5 6

AGE (YEARS)

Fig .21 Comparison of growth rates of Brook Trout from the Avalon Peninsula of Nfld ., and two areas of Labrador. -53

35 I

30 ~

~ U Z 25 ~ UJ ::J o UJ 20 l CC u..

~ Z 15 r UJ U a:: UJ Cl... 10

5 r-

o L-______L-__-L____~__~____~__~_____L______~------~ 23.0 28.0 33.0 38.0 43.0 48.0 53.0

FORK LENGTH (em)

Fig.22 Length distribution of Brook Trout from Ten Mile Lake.

60 r

~ 50 I U Z UJ ::J 40 I 0 UJ a:: u.. 30 I ~ Z UJ U a:: 20 I UJ Cl...

10 I

0 1 2 3 4 5 6

AGE (YEARS)

Fig.23 Age composition of Brook Trout from Ten Mile Lake. -54

This occurrence of invertebrates is similar to that reported for brook trout from Jacopie Lake, Labrador (Bruce, 1974),

Table 14. Stomach content analysis for brook trout from Ten Mile Lake.

Sample number: 25

Average condition: 50io full

Num ber of stomachs empty: 0

Food item Frequency Percent frequency

Od onat a 3 12

Trichoptera 5 20

Ephmeroptera 2 8

Diptera 19 76

Amphi poda 1 4

Hirudinea 1 4

Hemiptera 21 84

Coleoptera 8 32

Hydracarina 13 52

Cladocera 3 4

Pelecypoda 1 12

Gastrapoda 9 8

Insect remains 2 72

Detritus 18 36

Fish remains 1 4 - 55

Suckers - Family Catostomidae

White sucker - Catostomus commersoni (Lacepede)

The distribution of white suckers is restricted to North Ame rica.

In Canada this sucker is found in all provinces and territories except insular Newfoundland. In Labrador it is generally distributed and is one of the most frequently occurring fish in the area.

White suckers are usually found in warm shallow lakes and bays, and tributary rivers of larger lakes. (Scott and Crossman, 1973).

In the spring the suckers migrate from the lakes into suitable streams to spawn. Adults are said to home to certain spawning streams. - 56

The female of the species is very fecund, producing an estimated 24,550 eggs per kilogram of body weight (Scott and Crossman, 1973).

BACK- CALCUB.T10N OF GROWTH

Scales were usp.d in the age determination of white suckers.

The method of back-c~lculation used in this stu~y was the same as that used fer lake whitefish and northern pike.

The equation for the regression of body length to scale length was:

L 2.26 Ls + 9.16; correlation coefficient (r) 0.94. f = = The average scale lengths for each year of life and the corresponding calculated lengths are given in Table 15 and presented in Figure 24.

The growth rate is slower than that reported by Hatfield et al. (1972), for the Mac'cenzie River Valley (Fig. 25), and by Campbell (1935) for

Waskesiu L., Maskatchewan.

Table 15. M~an scale lengths and calculated fork length at annulus formation of white suckers from Ten Mile Lake.

Calculated Annulus Frequency Scale length (cm) fork length (cm)

I 0 1.0 11.4

II 0 2.0 13.7

III 0 3.1 16.2

IV 3 4.4 19.1

V 2 5.9 22.5

VI 10 7.5 26.1

VII 6 9.4 30.4

VIII 2 11.0 34.0 - 57

Table 15 (cont'd.) Calculated Annulus Frequency Scale length (cm) fork length (cm)

IX 0 12.6 37.6

X 1 13.9 40.6

XI 25 15.0 43.1

XII 30 15.8 44.9

XIII 19 16.6 46.7

XIV 1 18.4 50.7

XV 1 19.5 53.2

The oldest fish was XV+ years (Fig. 26) and had a fork length of

49.9 cm. The largest white sucker taken was 50.7 cm (Fig. 27) and was

XI+ years. According to McPhail and Lindsey (1970) the maximum reported

size attained by white suckers is 635 mm, and the maximum reported age

is estimated to be 17 years.

LENGTH DISTRIBUTION AND AGE COMPOSITION

The length distribution and age composition of the white sucke~ are presented in Figures 26 and 27.

The mean fork length of 170 white suckers was 44.13 cm. The mean female length (45.89 cm) was slightly less than the mean male length

(47.75 cm) while the mean length of fish with immature gonads was

22.26 cm. -58

36 E u 32 ::I: ~

~ a:: 0 24 u...

0 0 2 4 6 8 10 12 14 16 18 20 22

SCALE LENGTH (em)

Fig .24 Fish length - scale length relationship for White Suckers from Ten Mile Lake. 60

Ten Mile Lake • • Mackenzie River Area ...-----__e (Hatfield et ai, 1972)

/ / 40 /

/ E / u "" ~ I l- t:} Z UJ ....I 30 ::..::: a: 0 u..

o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

AGE (YEARS)

Fig.25 Comparison of growth rates for White Suckers from Ten Mile Lake and the Mackenzie Rlve'r Area, -60

40 t-

> 30 U Z UJ a::J 25 UJ a: l.L.. l- 2 0 Z UJ U a: 15 UJ CL.

5 I 15.55 19.55 23.55 27.55 31.55 35.55 39.55 43.55 47.55 51.55

FORK LENGTH (em)

Fig .26 Length distribution of White Suckers from Ten Mile Lake.

30 c .--

> 25 t- r- U Z w ::J 20 I-- 0 w a: l.L.. 15 f- Z UJ U ....-- a: 10 UJ CL. I- 5

n- Il r 1 2 3 4 5 6 7 8 .9 10 11 12 13 14 15

AGE (YEARS)

Fig .27 Age composition of White Suckers from Ten Mile Lake. LENGTH- WEIGHT RELATIONSH IP

The genera l logarithmic relation of length to weight:

Log N ~ 2.96 Log L - 4.81; correlatiGn c~efficient ~r) = 0.98.

The va!ve of the exponent (2.96) is slightly lower than that cal

~ u lated f0r white suckp.r in the MacKenzie River area (3.14) (Jessop et al.

1973 ) .

Sex Ratio: The female to male ratio was 1.24:1. Eighteen fish

displayed immature gonads. All mature males at the time of collection displayed nuptial tubercles on their caudal and anal fins.

Food Hab i ts: Of the 70 white sucker stomachs examined, 7~1o con

tai l e d food. The most common food items were dipteran pupae (96.4%)

followed by Hydracarina (49.1%) pelecypods (2~1o) and amphipods (18.2%)

(Table 16). This is in agreement with other studies where the white sucker was founc to feed ma i nly on benthic invertebrates.

Table 16. Stomach content analysis for white suckers from Ten Mile Lake.

Sanple num ber : 70

Average condition: 50/ 0 full

Num ber of st~machs empty: 15 Food item Frequency Percent occurrence Trichoptera 4 7.3 Ephmeroptera 4 7.3 Diptera 53 96 . 4 Amphipoda 10 18.2 Hirudinea 5 9.1 Hydracarina 27 49.1 Pelecypoda 11 20.0 Gastrapoda 2 3.6 Detritus 2 3.6 Cods - Family Gadidae

Burbot - Lata ~ (Linnaeus)

The burbot is the only member of the cod fish family which has adapted to a freshwater existence. It is found across Eurasia and in

North America where it ranges as far south as the Mississippi River in

Missouri (McPhail and Lindsey, 1970).

The burbot generally prefer the cold waters of deep lakes and large rivers. Rawson (1951) found that burbot of Great Slave Lake were common to depths of 100 meters while Scott and Crossman (1973) tell of the burbot being taken at depths of 213 meters.

The burbot is one of the few Canadian freshwater fishes that spawns -63

in mid-winter, under the ice (Scott and Crossman, 1973).

The diet of mature burbot consists almost entirely of fish, but the

smaller immature burbot feed mostly on benthic invertebrates (Scott and

Crossman , 1973).

Only two burbot were taken from Ten Mile Lake. The smaller fish + (IV, yE!ars) was 2,2.2 cm, w~ighed 50 l? ~ a_n~ _~ isplayed inunature gonads.

The larger burbot was 57.5 cm, weighed 1,150 g and was an XI + year male.

Ageing of the burbot was done by 'otoliths. Both fish contained , small.

suckers in their stomachs. J ,

\ '. COMPOSITION OF THE CATCH , -.i'; " ~ ., .. ;o-i - . I The total catch for the 28 net sets was 679. .. fi,h. :. weighing 798.6 kg. Of the 28 sets, 9 were l~\e trap· ne 't -~ -a~ d 19 were gillnets"; White sucker, \ lake whitefish, lake tro~t and; northern pike made up 25.970, and 16.9'70 of

the catch respectively, hy numbers. Northern pike and lake trout together made up 54% of the catch by weight. The remaining three species, round whitefish, brook trout and burbot constituted 16.6% by number, but only

4.5% of the catch by weight (Table 17). -64

Table 17. Percent number and weight of each species taken from Ten Mile Lake, Labrador, 1974.

Species Number Percent Weight (g) Percent

Wh ite sucker 170 25.0 193.80 24.3

Lake whitefish 142 20.9 137.74 17.3

Lake trout 139 20.5 198.77 24.8

Northern pike ll5 16.9 232.30 29.1

Round whitefish 84 12.4 13.07 1.6

Brook trout 27 4.0 20.70 2.6

Burbot 2 0.3 2.20 0.3

Total 679 100.0 798.6 100.0 -65

SUMMARY

1. The water area of Ten Mile Lake is 26.4 sq.km. The maximum

depth is 18.3 m and the mean depth is 2.9 m.

2. Thermal stratification occurs only in two isolated deep holes

in the lake. The highest surface water temperature recorded

was 21.1 C. The mean oxygen content for surface water was

9.44 ppm.

3. Water quality is low in terms of nutrient levels. Average

surface water pH was 6.35 and the mean specific conductance

value was 12.65.

4. The potential fish yield for this body of water was estimated

at 2.64 kg/hectare/year.

5. Seven species of fish were taken in gillnets and lake trap

nets. The most abundant of these were white suckers, lake

whitefish, pike and lake trout with lesser numbers of round

whitefish brook trout and burbot.

6. The growth rates of all fish species except lake trout are

approximately the same as other populations of the same

species in northerly latitudes. The lake trout of Ten Mile

Lake display a significantly slower growth rate than has been

reported for other northern populations of lake trout.

7. A qualitative food study was done for all fish species.

Pike and burbot were the only species found to be feeding

exclusively on fish. Benthic invertebrates were the most

important food for the other fish species. -66

One of the many small coves of Ten Mi l e Lake.

Brook 61, the largest inlet to Ten Mile Lake. -67

Using a modified Kemmerer water sampling bottle.

Using a Wisconsin type plankton net for surface and sub-surface sampling. -68

A large northern pike taken in gillnet from Ten Mile Lake.

Lake trap net used in live trappin~ of fish from Ten Mile Lake. -69

Fiel d s t a tion for obtaining information from the fish netted in Ten Mile Lake .

Sampl ing fish with gillnet s in Ten Mile Lake .

-70

ACKNOWLEDGMENTS

I gratefully acknowledge W.J. Bruce for his help and guidance in the preparation of this report, and to R. Porter who reviewed the manu script and provided criticism.

Special thanks is extended to C. Walters, Term Technician and J.

Wheeler, summer students for their invaluable assistance in collecting the field data and maintaining the project.

Special thanks is also extended to Dr. C.C. Davis, p1ankto10gist with Memorial University of Newfoundland for his careful analysis of the plankton samples, and to A. Jamieson who supervised the water quality analysis, and to Mrs. J. McGrath and Mrs. S. Kearsey for typing the text.

The assistance provided by the personnel of CFLCO and G. Burke,

Fisheries Officer for the Churchill Falls area, is greatly appreciated.

Credit is also gratefully acknowledged to Mr. K. McVeigh of the

Graphics Division of Environment Canada for the representative fish photographs. .. -71

REFERENCES

• Allen, G.H. 1956. Age and growth of the brook trout in a Wyoming beaver pond. Copeia (1) : 1-9.

Alvord, W. 1953. Validity of age determination from scales of brown, rainbow trout, and brook trout. Trans. Amer. Fish. Soc. 89 (1): 80-81.

Bruce, W.J. 1974. The limnology and fish populations of Jacopie Lake, West Forebay. Smallwood Reservoir, Labrador. Technical Report Series No. NEW/T-74-2. Res. Dev. Br. Fisheries Service, Dept. of the Environment, Newfoundland Region.

Campbell, R.S. 1935. A study of the common sucker Catostomus commersoni (Lacepede) of Waskesin Lake. M.A. Thesis. Dept. BioI. Univ. Sask., • Saskatoon, Sask . . 48 p .

Cooper E.L. 1951. Validation of the use of scales of brook trout, Salvelinus fontinalis, for age determination. Copeia (2): 141-148.

Dryer, W.R. et al. 1965. Food of lake trout in Lake Superior. Trans. Amer. Fish. Soc. 94 (2): 169-176.

Duthie, H.C. and M.L. Ostrofsky. 1974. Plankton, chemistry and physics of lakes in the Churchill Falls region of Labrador. J. Fish. Res. Board Can. 31: 1105-1117.

Frost, W.E. and C. Kipling, 1959. The determination of the age and growth of pike (Esox lucius (Linnaeus) from scales and opercular bones. J. Cons.-rnt. Explor. Mer. 24(2): 314-342.

Hat field, C.T. et al. 1972b. Fish resources of the MacKenzie River Valley, Interim Report I, Vol. II. Dept. of the Environment, Fisheries Service, Winnipeg, Manitoba, 289 p.

Hogman, W.J. 1968. Annulus formation on scales of four species of coregonids reared under artificial conditions. J. Fish. Res. Board Can. 25(10): 2111-2122.

Jessop B.M. and G. Power, 1973. Age, growth and maturity of round • whitefish (Prosopium cylindraceum) from the Leaf River, Ungava, Quebec. J. Fish. Res. Board Can. 30: 299-304. -72

Kennedy, W.A. 1949. Some observations on the coregonine fish of Great Bear Lake, N.W.T. Fish. Res. Board Canada Bull. 82 : 10 p .

. 1954. Growth, maturity and mortality in the relatively unexploited lake trout, Cristivomer namycust, of Great Slave Lake. J. Fish. Res. Board Can. 11(6) : 827-852.

La gler , K. F. 1956. Freshwater Fishery Biology. 2nd. ed. Wm. C. Brown Company Publishers, Dubuque, Iowa.

MacKay I. and G. Power. 1968. Age and growth of round white fish (Prosopium cYlindraceum) from Ungava. J. Fish. Res. Board Can. 25 : 657 - 666.

Martin, N.V. 1970. Long-term effects of diet on the biology of the lake trout and the fishery in Lake Opeongo, Ontario. J. Fish. Res. Board Can. 27(1) : 125-146.

McPhail, J.D. and C.C. Lindsey, 1970. Freshwater fishes of north we stern Canada and Alaska. Fish. Res. Board Can , Bull. 173 : 381 p.

Miller, R.B. and W.A. Kennedy. 1948. Pike (Esox lucius Linnaeus) from four northern Canadian lakes. J. Fish. Res. Board Can. 7(4) : 190-199.

Powell, Sheppard T. Associates (Canada) Ltd. 1971. Churchill Falls Power Project. Water Quality and Biological Study 1970-71. Vol. lAo

Quadri, S.U. 1968. Growth and reproduction of the lake whitefish, Coregonus clupeaformis, in Lac la Ronge, Saskatchewan. J. Fish. Res. Board Can. 25(10) : 2091-2100.

Rawson, D.S . 1932. The pike of Waskesiu Lake, Saskatchewan. Trans. Amer. Fish. Soc. 62(1932) : 323-330 .

. 1951. Studies of the fish of Great Slave Lake. J. Fish. Res. Board Can. 8(4) : 207-240 .

. 1961. The lake trout of Lac la Ronge, Saskatchewan. J. Fish. Res. Board Can. 18(3) : 423-462.

Reckahn, J.A. 1970. Ecology of young lake whitefish (Coregonus clupeaformis) in South Bay, Manatoulin Island, Lake Huron. In C.C. Lindsey and C.S. Woods (ed.). Biology of coregonid fishes. Univ. Manitoba Press, Winnipeg, Man. 560 p.

Ryder, R.A. 1965. A method for estimating the potential fish production of north-temperate lakes. Trans. Amer. Fish. Soc. 94(3) : 214-218.

Scott, W.B. and E.J. Crossman, 1973. Freshwater fishes of Canada. Fish. Res. Board Can. Bull. 184-920 p. -73

Van Oost~n, J. 1923. A study of th~ scal~s of whitefish of known ag~s. Zoologica 2(17) : 381-412.

Wainio, A.A. 1966. A study of pike (Esox lucius Linnaeus) in two areas • of Lak~ Huron. M.Sc. Th~sis Univ~ronto, Toronto, Ont. 72 p.

Welch, P.S. 1948. Limnological methods. The Blakiston Company, Philadelphia.

Wiseman, R.J. 1969. Some aspects of the biology of the sp~ckl~d trout Salvelinus fontinalus Mitchill 1815, in th~ waters of insular Newfoundland. M.Sc. Thesis, Biology Dept. Memorial University of Newfoundland 1-204. p .

. 1972. The limnology and sports fish populations of sel~cted Avalon Peninsula lak~s. Unpublished offic~ report No. 100. Res. Dev. Br. Fisheri~s Service, Environment Canada, St. John's, New foundland. 167 p. •

• ...

•

• APPENDIX 1. Conversion of conductivity values to r.D. S.

C = actual reading in microhoms 2

T2 temperature of water at actual reading •

•

e.g. 13 = 4 + 68 C C = 14.6 l 4 + 77 l

Y (T.D.S.) 7.02 + (0.72) (C ) = l

e.g. T.D.S. = 7.02 + 0.72 (14.6)

r.D.S. = 7.02 + 10.51

T.D.S. 17.5

... •

•

, -75

APPENDIX 2. T~mperature readings for Ten Mile Lake, (June-July, 1974).

Dat e Surface water temperature ~OC) , June 27 15.5 28 15.5 29 16.6 30 1B.O J uly 1 17.7 2 17.2 3 15.4 4 14.4 5 13.9 6 15.5 7 16.6 B 17.2 9 17.2 10 17.2 11 15.5 12 15.3 13 15.5 14 16.0 15 16.2 16 16.1 17 15.7 18 16.0 19 16.2 20 16.2 21 16.9 22 17.7 • 23 17.7 24 17.7 , 25 1B.3 26 20.0 27 21.1 •

•