LIMNOLOGY OF YELLOWSTONE

LAKE IN RELATION TO THE

CUTTHROAT TROUT

PROPiRTY opPRINCjETON UNIVERSITy

LIBRARY Y

JAN 2

DOrr;e .i DIVISION

UNITED STATES DEPARTMENT OF THE INTERIORFISH AND WILDLIFE SERVICEBUREAU OF SPORT FISHERIES AND WILDLIFERESEARCH REPORT 56

metadc100540

9N2O3 33

RESEARCH REPORTS

This series of reports was begun when the Fish and Wildlife Service was establishedin 1941; the series superseded Wildlife Research Bulletins of the Bureau of BiologicalSurvey and Investigational Reports of the Bureau of Fisheries, those two bureaushaving merged to form the Service. The Research Reports are being continued (withResearch Report 54) in a slightly changed format, as the research-reporting series ofthe Bureau of Sport Fisheries and Wildlife (U.S. Fish and Wildlife Service), com-prising reports of scientific investigations related to the work of the Bureau. TheBureau distributes these reports without charge to official agencies, to libraries, and toresearchers in fields related to the Bureau's work ; additional copies may usually bepurchased from the Division of Public Documents, U.S. Government Printing Office.

Current Research Reports are-

54. Fluctuations in Age Composition and Growth Rate of Cutthroat Trout in Yellow-

stone Lake, by Ross V. Bulkley. 1961. 31 pp.

55. Mortality Studies on Cutthroat Trout in Yellowstone Lake, by Orville P. Ball and

Oliver B. Cope. 1961. 62 pp.

56. Limnology of Yellowstone Lake in Relation to the Cutthroat Trout, by Norman G.Benson. 1961. 33 pp.

57. Chemical Composition of Blood of Smallmouth Bass, by Eddie Wayne Shell.

In press.

58. Chronic Effects of Endrin on Bluntnose Minnows and Guppies, by Donald Irvin

Mount. In press.

LIMNOLOGY OF YELLOWSTONE

LAKE IN RELATION TO THE

CUTTHROAT TROUT

Norman G. Benson

Fishery Research Biologist

RESEARCH REPORT 56

UNITED STATES DEPARTMENT OF THE INTERIOR

Stewart L. Udall, Secretary

Frank P. Briggs, Assistant Secretary for Fish and Wildlife

FISH AND WILDLIFE SERVICE

Clarence F. Pautzke, Commissioner

BUREAU OF SPORT FISHERIES AND WILDLIFE

Daniel H. Janzen, Director

ttT Or

Published by the U.S. Fish and Wildlife Service " Washington " 1961Printed at the U.S. Government Printing Office, Washington, D.C.

For sale by the Superintendent of Documents, U.S. Government Printing OfficeWashington 25, D.C. - Price 40 cents

CONTENTSPage

Introduction-------------- -------------------------------- 1Geology---------------------------------------------------2Weather and water levels_____.________----____________-_-----__ 2Morphometry----------------------------------------------3Methods._----..--------------------------------------------------4Lake currents- ---------------------------------------------- 6

Water temperatures-_.-.------------------------------------------9Secchi disk transparency _--__---_-__________.______._________ 10Water chemistry_ _ __----------------- -------------------------- 11Bottom types-----..--------------------------------------------- 15Aquatic plants._ _ ...--------------------------------------------- 16Plankton..-------------------------------------------------17Benthos------------.-------------------------------------------20

Vertical distribution of cutthroat trout--_--_.___-_._______-_______21Food of cutthroat trout__- - --_______---__ .---__-_----.--_-___ 22Trout density and limnology___ _.----------------------------------24Biology of Yellowstone Lake_.--_------------------------------ 26Summary----_.-------------------------------------------------28Literature cited -------------------------------------------- 29Appendix A-Points of release and recovery of drift bottles----------32Appendix B--Points of release and recovery of drift bottles----------33

m

ABSTRACT

Limnological data collected from 1954 to 1959 on surface currents, bottom currents,temperatures, bottom soils, water chemistry, plankton, bottom fauna, and higher aquaticplants are related to the biology of the cutthroat trout, Salmo clarki lewisi, in Yellow-stone Lake (Wyoming). The lake, formed on Eocene lava, is oligotrophic and low indissolved solids. Diaptomus shoshone, Daphnia shoedleri, and Conochilus unicorns madeup more than 90 percent of the macroscopic zooplankton by number. Upwelling in WestThumb was demonstrated by temperature stratification and conductivities. Plankton dis-tribution and abundance were related to currents and water chemistry. Depth distribution,feeding, and movements of trout are related to food abundance. Trout less than 315 milli-meters in total length are not caught readily because of their feeding habits and greaterdispersal. There is evidence that the heavy trout harvest in the northern part of the lakeallowed Gammarus lacustris, an important trout food, to become locally abundant.

IV

LIMNOLOGY OF YELLOWSTONE LAKEIN RELATION TO THECUTTHROAT TROUT

By Norman G. Benson, Fishery Research Biologist

Rocky Mountain Sport Fishery InvestigationsLogan, Utah

Limnological studies on YellowstoneLake (Wyoming) began in 1890 whenForbes (1893) described the common zoo-plankters, noted their relative abundance,and recorded other general features of thelake. Except for occasional records ofwater temperatures and a few planktoncollections, the lake was not studied limno-logically again until 1954, when the staffof the Rocky Mountain Sport Fishery In-vestigations initiated the work reportedhere.

Much has been published on the biologyof the cutthroat trout in Yellowstone Lakeand tributaries (Cope, 1956, 1957; Ball,1955; Laakso and Cope, 1956; Ball andCope, 1961). The purpose of this paper isto describe general features of the lakeecology and to relate this information tothe known life history of the cutthroattrout.

Orville Ball, Martin Laakso, and severalfishery aids mapped the lake and collectedsome field data. Identification of zoo-plankters and bottom organisms was byMarvin Meyer, Alan Stone, W. W. Wirth,A. W. Bell, and Clarence Shoemaker;Arthur Holmgren identified the higheraquatic plants. I appreciate the critical

review of the manuscript by Oliver B.Cope, C. J. D. Brown, W. T. Edmundson,and Ross V. Bulkley.

The fish fauna of Yellowstone Lake in-cludes the cutthroat trout, the longnosesucker Catostomus catostomvs (Forster),the longnose dace Rhinichthys cataractaeValenciennes, the smallfin redside shinerRichardsonius balteatus hydrophlox(Cope), and the lake chub Hybopsis plum-bea Agassiz. Only cutthroat trout andlongnose suckers are found throughout the

lake. The other species are restricted to

shallow lagoons in the northern end and

West Thumb (fig. 1), to very shallow (lessthan 2 meters deep) protected littoralzones of the lake, or to tributary streams.

The original fish fauna included .only thecutthroat trout and the longnose dace.

Information is presented on lake

geology, lake morphometry, weather,water levels, bottom currents, surface cur-

rents, temperatures, bottom soils, water

chemistry, phytoplankton, zooplankton,food of trout, and depth distribution of

trout. A discussion of the relations of

these conditions to the biology of the cut-

throat trout in the lake follows.

1

2

GEOLOGY

The watershed of Yellowstone Lake hasbeen an area of volcanic activity since theEocene period, when large amounts ofvolcanic breccias were deposited (Bauer,1955). With another heavy breccia de-posit in the middle Cenozoic era, thewhole series of breccias formed a stra-

tum about 2,000 meters thick. Rhyolitedeposits were superimposed on the brecciasin certain areas in the late Cenozoic. Theoriginal breccias are exposed on the south-ern and eastern drainage basins of Yel-lowstone Lake, and rityolite deposits areexposed on the south shore and in the west-ern drainage area. Small deposits of

dolomite, basalt, and glacial drift are pres-ent in isolated sections of the watershed.

The available information does not al-low an adequate explanation of the geo-logical formation of the present basin ofYellowstone Lake, although the original

lake basin was believed to have beenformed by a subsidence or readjustment ofthe original lava flows in the Eocene.Bauer also mentions the possibility that

pre-Eocene glaciation may have formedthe original basin. Recent glaciation,

erosion, and milder forms of volcanic ac-tivity have sculptured the present basin.Many active geysers and hot springs are inthe watershed. The West Thumb area isconsidered to be an old geyser basin, andhot springs are still present on the shore-line and below the water surface.

During its geological history, the lakehas drained into three oceans. Until theearly Pleistocene, the lake drained into thePacific Ocean via the Snake River. At

that time the Grand Canyon of the Yel-

lowstone formed, and the lake drained

northward into Hudson Bay. Since the

retreat of the glaciers, the lake has drained

through the Missouri River system into

the Gulf of Mexico. During the glacial

period, the lake was much larger than at

present, owing to a glacial lobe at the

present site of the Grand Canyon of the

Yellowstone (fig. 1). Several lake ter-

races from the glacial period can be ob-

served in Hayden Valley. One lake ter-

race has a present elevation of 2,470

meters, or 112 meters higher than the lake

altitude.

WEATHER AND WATER LEVELS

The lake watershed is on the east slopeof the Continental Divide at an altitude of2,358 meters (7,731 feet). Air tempera-tures, wind measurements, and precipita-tion for the Yellowstone Lake area havebeen collected at the Lake Ranger Stationfor the U.S. Weather Bureau. The meanmonthly temperatures from 1953 to 1957ranged from minus 15.30 C. (4.50 F.) inFebruary 1956, to 16 C. (60.80 F.) inJuly 1954. The mean monthly tempera-ture during most summer months aver-aged about 130 C. (55.40 F.), and duringwinter months averaged minus 9.50 C.(14.90 F.). Air temperatures in the sum-

mer rarely reach 300 C. (86.00 F.). Theannual precipitation from January 1953to November 1957 varied from 39.3 cm.(15.49 inches) in 1953 to 62.2 cm. (24.47inches) in 1955. Most precipitation fallsduring the late fall and winter months inthe form of snow.

Data collected at the Lake Ranger Sta-

tion on wind velocity and direction showedthat the predominant winds were from thesouth and southwest (table 1), and thatwind velocities were higher when the windcame from the latter two directions.Winds were stronger in 1955, 1956, and1959 than in 1957 and 1958. Diurnal

Ye/lows one River (ou/le)

Lake ag /P/cn Cr

LAKE AREA

Yellowstone

20

Steamboat Point

N 20

tevesnI.Hyden

Valley

sand Point co ub Cr.f

Roar

Arnica r. 95 /a C

COTERIERkLPoMTR

reeze Point

Signal Point

Wolf Point FakI

Eog

MILETHU S

OLAIM UTA4 AR

YE LWMTONE STATIONALPR

06

CBToRyNTRVL0 0ETR

WESTM LEHU2B

20 tiO ETE 4 5

LYEL LOGYSTNE _AK

YELLOWSTNE NATIEALSTAAKM

WYOMrNG

CONTOUR NTERVAL 0nkETER

Grouse so

LIMNOLOGYSTUTIOARM

Yellowstone

Roenn

Rer

YeostoneRiver

Yellowstone River (int/e)

U G.

FIGURE 1.-Contour map of Yellowstone Lake showing limnology stations and localities mentioned in the report.

3

TABLE 1.-Wind velocity and direction at Lake Yellowstone during July and August from 1955 to 1959

[Data collected daily at 4 p.m., at Lake Ranger Station]

Mean daily Days recorded from- Days withYear velocity inno wind

miles per recordedhour S. SW. SE. E. N. W. Other

1955..-..... ----.--- 5.92 25 17 4 1 0 10 0 51956-...--------.. -7.04 24 18 1 2 4 6 7 01957_----...... --.. 1.35 21 4 1 4 2 0 2 281958_....----...-... 2.30 23 6 8 5 2 3 8 71959_-..---.....-.. -8.05 28 18 2 0 5 5 4 0

changes in wind intensity were quite reg-ular in that the high velocity winds usu-ally began about 11 a.m. and decreasedabout 5 p.m. Calm conditions usually pre-vailed during the evenings and earlymorning. The highest air temperaturesprevailed during the period of maximumwind velocity and the resultant wave ac-tion. This daily cycle undoubtedly in-creased the warming effects of the sun onwater temperatures, since surface temper-atures sometimes increased 30 C. fromearly morning to the time of maximumwind intensity.

Information on water levels and volumeof outflow has been collected by the Sur-face Water Branch of the U.S. GeologicalSurvey (1952, 1953, 1954, 1955; also un-published data). The annual water levelfluctuation of Lake Yellowstone variesfrom 1.5 to 1.8 meters. The water levelis lowest from January to March, risesrapidly to a high in late June and July,and recedes from July to December. The

annual outflow in thousands of cubicmeters through the Yellowstone Rivervaried by water year, October throughSeptember, as follows: 1951-62, 1,386,454;1952-53, 1,270,505; 1953-54, 1,284,073;1954-55, 1,003,674; 1955-56, 1,587,798;1956-57, 1,270,949; and 1957-58, 939,482.The variation in outflow by month followsthe water-level curve described above,with a maximum in July and a minimumin December. The capacity of Yellow-stone Lake is about 14X 109 cubic meters.The evaporation rate is about 358,948,500cubic meters per year, considering an ap-proximate annual evaporation rate of1.016 meters (derived from p. 151 inWisler and Brater, 1949). Thus, lakewater is completely replaced about every8 to 10 years.

Lake Yellowstone freezes over in De-cember or January, and ice does not leave

until the last week of May or early June.The ice reaches a thickness of 0.4 to 0.9meters.

MORPHOMETRY

The bottom configuration of Yellow-stone Lake was mapped with a fathometermounted on a launch during the summersof 1954, 1955, and 1956. The depth con-tours were measured by a series of tran-sects at 1-mile intervals in both north-south and east-west directions throughoutthe lake. Transects were made in otherdirections to verify the depths determinedby the grid method and to measure various

arms. A map was constructed to 20-metercontours (fig. 1).

Yellowstone Lake has a surface area of35,391 hectares (136.66 square miles), amaximum measured depth of 98 meters

(320 feet), a mean depth of 42 meters (139feet), and a basin capacity of 14X109cubic meters (12,095,264 acre feet). Theareas of lake bottom at various depthranges are shown in table 2. The lake

4

basin has a deep trench along the eastshore which extends into both the SouthArm and Southeast Arm. It extendswestward between Stevenson and FrankIslands to a point near the west shore ofthe main body of the lake. The lake basinin West Thumb is more cone-shaped, withno islands and with the deepest area in theapproximate center of the thumb.

The lake is shaped like a hand withthree fingers and a thumb, and has ashoreline development of 3.04. The water-shed has an estimated area of 261,590hectares (1,010 square miles) and consistsprincipally of lodgepole pine forest andalpine meadows. The largest stream en-tering the lake is the upper Yellowstone

River, but the lake cannot be consideredsimply an enlarged section of the river,

since 42.2 percent of the lake watershed

is outside the upper Yellowstone River

drainage.

TABLE 2.-Areas of various depth ranges in.Yellowstone Lake

Area, in-- _____ -___-.Percent

Depth range of totalSquare Acres Hec-miles tares

Less than 20 meters-- 31.44 20,121 8,143 23.0120-40 meters------------ _ _ _ 34.82 22, 282 9,017 25.4840-60 meters--_----------_26.70 17,088 6,916 19.5460-80 meters-----------_ 26.40 16, 893 6, 837 19.3280-95 meters-------------17.29 11,066 4,478 12.65

Total area of lake.- 136.65 87, 450 35, 391

METHODS

Limnological stations.-Originally, in1954,20 stations were established for meas-

uring physical and biological conditions.In 1957 the number was reduced to 10 be-cause it was found that variations in the

lake could be accurately determined fromthe 10 stations shown on figure 1.

Temperature and surface currents.-Temperatures were measured by a bathyo-thermograph (depth range, 61 m.) whichwas calibrated periodically with a resist-ance thermometer. Temperatures below61 meters were collected with a reversingthermometer. For describing water strati-fication, the metalimnion as defined byHutchinson (1957) has been used to definethe whole region in which the temperaturegradient is steep.

Surface currents were determined by re-leasing 340 drift bottles on 16 differentseeding lines in the lake. The bottleswere designed by the Great Lakes Biologi-cal Laboratory (Johnson, 1958). Thesebottles were found to resist wind actionunless surface currents were produced bywind. To facilitate recovery, our bottleswere painted red by swirling thinned paint

on the inside. The bottles were releasedwhile maintaining a launch at a constantspeed and releasing the bottles at constanttime intervals. Bottles were recovered,and their locations noted, by NationalPark Service employees, tourists, and U.S.Fish and Wildlife employees.

Bottom currents. - Bottom currentswere measured by a modification of theleaning-tube-type current indicator de-scribed by Carruthers (1958a and 1958b).The indicator (fig. 2) proved accurateenough to measure current speeds to thenearest tenth of a knot and to measure di-rection to within 20 degrees. The graphillustrated by Carruthers (1958b) wasused for recording current speed, since itwas found that our modification of hisbottle followed this curve the same as abottle constructed to his specification.

Water chemistry.-Standard Methodsfor the Examination of Water, Sewage,and Industrial Wastes (U.S. PublicHealth Association, 1955) was used as aguide for dissolved-oxygen, free-carbon-dioxide, and alkalinity determinations.Oxygen values were corrected for temper-

5

float(water surface)

/plastic cap(rubber covered)

glass tubing

nylon thread

air

-compass

gelatin

pyrex infant bottle

net twine

2ft. stick to prevent line fouling

(lake bottom)

anchor

FIGURE 2.-Diagrammatic sketch of bottom-cur-rent indicator.

ature and altitude from the nomographin Hutchinson (1957). Specific conduct-ance was determined by a conductivitybridge and readings were converted to astandard 25 C. A more complete chem-ical analysis of four water samples wasconducted by .the Surface Water Branch

of the U.S. Geological Survey.Secchi disk tranzsparency.-A Sechi

disk (20 cm. in diameter, black and white)was used to measure the limit of visibility,and a water telescope was utilized to elim-inate surface glare.

Bottom soils.-Five bottom-soil sampleswere analyzed for chemical properties by

the Soils Laboratory of Utah State Uni-versity. The percentage of organic matterin 59 additional samples was determined

by the laboratory. Observations weremade on the distribution of boulders, rub-ble, silt, sand, and other bottom types indifferent sections of the lake.

Plankton.-Net plankton tows were

made with a Wisconsin plankton net usingNo. 25 bolting cloth during 1956. Thismethod sampled the top 10-meter stratumof water and the net strained an estimated

595956 0 -62 -2

211 liters (10.99 cu. ft.) of water. Severalinherent errors in this method (as sum-marized by Welch, 1948) are recognized.The samples were preserved in a 3-percent

solution of formaldehyde.In 1957 and 1958 water for net plank-

ton analyses was collected with a 3-literKemmerer water sampler. Each sample

consisted of 10 liters of water and wasstrained through a plankton net withNo. 25 bolting cloth. Plankton samples

for phytoplankton measurements werecounted in a Sedgewick-Rafter countingcell under a magnification of 100 X. Forz o o p l a n k t o n analyses, samples werecounted with a rotary-type counter undera dissecting microscope at a magnificationof 30X (Ward, 1955). Data on phyto-plankters are weak because many formspass through No. 25 bolting cloth. Onlyabundant zooplankters were identified tospecies.

Bottom organisms.-Bottom sampleswere collected with a 6- by 6-inch (231

sq. cm.) Ekman dredge, and the organismswere separated from the bottom soils by

sieving through a No. 30 Tyler (0.589mm.) screen. Four samples were col-

lected at each station. Sandy or rockybottoms could not be sampled adequatelywith the Ekman dredge, although we de-termined the type and relative abundance

of organisms in these bottom types by tak-ing several dredge samples. Commonforms were identified to species by

specialists.Stomach ainalyses.-Stomachs for food

contents were collected from anglers bycreel-census clerks in 1957 and 1958. Ad-ditional stomachs were collected with gillnets in 1957 and 1958. All were preservedin formalin and sorted in the laboratory.

Organisms were identified as closely aspossible and counted. Aliquots were usedin counting large samples.

Gill netting.-Experimental gill nets(125 by 6 ft.) with square meshes 21/2, 2,11/2, 1, and 3/4 inches were used for sam-

6

pling fish in different sections of the lakeat different depths. All nets were set from3 to 6 p.m. on one day and picked up from8 to 10 a.m. the following morning. Eachset is considered to be an equal sample ofan overnight set.

Areas of lake.-Three areas of the lakehave been differentiated for purposes ofcomparing lake limnology with move-ments of trout and fishing pressure in-tensity. The West Thumb area consistsof the lake west of a line between RockPoint and Wolf Point and includes 19.1percent of the lake area (see fig. 1). Thenorthern area consists of all of the lakenorth of a line between Rock Point andElk Point and includes 25.4 percent of thearea. The southern area consists of all thelake south and east of these lines and in-cludes 55.5 percent of the area.

Catch of fish.-Creel census data werecollected on Yellowstone Lake from 1950

to 1959 and the method has been de-scribed (Moore, et al., 1952). The catcheach year was computed from samplingdifferent segments of the fishery, such asshore fishermen, guide boats, and privateboats. All of the fishing in each segmentof the creel census was done predomi-

nantly in a certain area. It was thus pos-

sible to determine with some accuracy thetotal catch each year as coming from each

of the three areas of Yellowstone Lake.

The West Thumb harvest includes all row-boats and guide boats from West Thumb,

20 percent of the trailer-boat catch, and25 percent of the shoreline catch. The

catch from the southern area consisted of

75 percent of the cruiser catch, 15 percent

of the trailer boat catch, and 5 percent of

the catch from Lake or Fishing Bridge

guide boats. All remaining fish caughtwere taken in the northern area.

LAKE CURRENTS

Surface currents. - Certain considera-tions are necessary in the interpretationof drift bottle data:

1. Few bottles were recovered in the openwater, and the route that a bottle followedfrom its release point to its destination wasunknown. The predominant currents in the lakewere deduced from a series of recoveries.

2. The number of bottles recovered on cer-tain isolated southern sections of the lake shorewas low owing to infrequent visits by touristsand National Park Service employees. Specialefforts were made by our employees to collectbottles in these areas, but many undoubtedlywere lost.

3. Descriptions of recovery points were rarelyprecise and no attempts were made to interpretminor differences in the general current pat-terns from a few unusual recovery points.

4. Complete analyses of the influence of dailywind direction on currents is not possible. Thewind data includes readings at 4 p.m. at theLake Ranger Station and experience has shownthat these readings did not always reflect con-ditions for the entire lake or even for a completeday.

Our surface-current information is

based on the recovery of 155 bottles from

340 released, or a recovery rate of 45.6

percent. A summary of the release pointsand recovery points is plotted in appendixfigures 1 and 2. Surface currents asderived from these recoveries are shownin figure 3.

The surface currents on YellowstoneLake during 1957 and 1958 flowed mostlytoward the north, east, or northeast, andwere caused by' the predominant winds

from the south and southwest (table 1).Occasional winds from the east or south-east had much less velocity than winds

from the south or southwest. Most re-

coveries were made on the north and east

shores of the lake. The only area where

the currents regularly deviated from the

above-mentioned directions was around

Frank Island and at the entrance to West

Thumb. Several bottles were carried from

7

seeding lines northwest of Frank Island(seeding lines E and F on appendix tables1 and 2) into West Thumb and southeastof Frank Island. Most of the bottles thatwere released within West Thumb werecollected on the north and northwestshores of the main body of the lake, point-ing to the large amount of surface water

leaving Thumb Lake. Surface water in

the South and Southeast Arms also wascarried northward, although many bottleswere recovered on the east shores of these

arms.The current speed can only be approxi-

mated, but one bottle traveled a minimum

of 7 miles in 1 day. Several bottles were

collected after being carried 10 miles in 2

days.Bottom currents.-Bottom c u r r e n t s

were measured at 57 stations from August

20 to September 7, 1959, and the results

plotted on figure 4. The following gen-eral conclusions were deduced from these

measurements:

1. Some water flows along the lake bottom intoWest Thumb.

2. Currents southwest of Frank Island werevariable, but flowed generally to the northeast.

3. Currents in the northeast main body of thelake flowed northward along the east shore andwestward along the north shore.

4. There was evidence of clockwise bottom cur-rent circulation within West Thumb.

Outlet

t

I / //

7 r

NSWEST THUMB ,

r t

YELLOWSTONE LAKE /WYOMING SOUTHEAST ARM

MILES0 4 SOUTHInlet

S 23456 AR

KILOMETERS

FIGURE 3.-Direction of surface currents on Yellowstone Lake as deduced from drift-bottle recoveriesshown in appendix figures A and B.

8

5. No consistent relation was found betweendepth and current speed.

Relations between surface and bottom

currents.-The predominant north andnortheasterly flow of surface water inYellowstone Lake is generally compen-sated by a northwesterly and southwester-ly flow of water along the lake bottom.The great mass of water that piles up onthe east shore of Yellowstone Lake forcesbottom currents to flow in northerly andwesterly directions, and bottom currentscontinue to flow westward back into WestThumb section. The bottom-current cir-culation in West Thumb suggests a clock-wise movement. Mixture of bottom andsurface water probably occurs in West

Thumb as evidenced from our temperatureand water-chemistry information pre-sented later. Undoubtedly the subsurfacecurrent patterns described above are anoversimplication of the currents actuallyoccurring in Yellowstone Lake, althoughour data do not allow a more complete de-scription of the true conditions. Mortimer(1952) described the occurrences of in-ternal seiches in Windemere, and both ourcurrent and temperature data (presentedlater), when compared with Mortimer'sdata, suggest similar conditions in Yellow-stone Lake. This is true especially in theregion from West Thumb to the north-east shore where the movement of surfacewater is most pronounced.

KEY TO SYMBOLS Outlet

-+ direction

O no detectable 4current 4 (no

I - 0- 0.1 knots2- 0.1-0.2 knots3- 02-03 knots 3.4t--t

4- 03-0.4 knots - 45- 0.4-0.5 knots6- 0.5-0.6 knots

N -1 00

YELLOWSTONE LAKEWYOMING

MILESI. 2 3 4 Inlet

0 1 2 b4$KILOMETERS

FIGURE 4.-Measurements of bottom currents in Yellowstone Lake from August 20 to September7, 1959.

9

WATER TEMPERATURES

Water temperatures at different depthsin Yellowstone Lake have been measuredfrom June to the middle of October. Datafrom Station A have been used for illus-trating seasonal and annual differencesbecause it is north of the area of greatestsurface water movement and the mostcomplete data have been collected at this

station (fig. 5). After the ice leaves nearthe end of May or in early June, the lakebegins to warm, but remains virtually

homothermous (4.5 to 5.8' C.) duringearly June. This period is comparable to

the early spring warming period describedby Church (1945) for Lake Michigan. Inlate June the surface water begins to forma protective warmer layer, although noclear-cut metalimnion has yet formed. Atthis time several temporary metalimnionlayers have been observed (see June 30,

1959, in fig. 5), as has been recorded byPennak (1955) from Grand Lake, Colo-rado. Surface temperatures reach be-

tween 10.0 and 14.00 C. during this phase.In middle July a permanent metalim-

nion begins to form and the temperature

gradient in the epilimnion narrows downto about 100 C. The depth of the epilim-nion during its early formation usuallyvaries from 5 to 10 meters. During lateJuly and early August the stratificationbecomes complete and the summer stagna-tion period described by Church begins.Surface temperatures recorded during this

period varied from 15.5 to 17.80 C., whilethe total temperature drop in the epilim-

nion was usually less than 40 C. The tem-perature gradient in the metalimnionvaried from a drop of 120 C. in 10 meters

to 10 C. in 3 meters. Temperatures be-low 90 meter depths during complete

stratification were not recorded below 4.60

C., which is the temperature reached be-fore stratification.

In late August the lake surface water

begins to cool and the metalimnion starts

to sink. This latter layer develops a

smaller temperature range and the tem-

perature gradient decreases. Tempera-

tures in September at 30 meters werehigher than in August, due to the sinkingof the metalimnion. On October 15, 1958,

61.5 16.1 147 145 I 6 .0 .5 I.5 17.5 I.6 14.71954 1957

Is sEPT.2

AIR TE MP.AUG3

AIR TEMP.

15 -1 JUNE 6.6 -JUNE 8.7

JULY 16.6 JULY 163.0AUG 1067 AIUG 13.4

305 U. 62 7.8 7.6 5. 6.16.1 .4 7.2 6.7 50m

16.1 15.5 16.7 J .- 7 Y.1__ _

7~ 5.5.

AJ 5315.

1955

AIR TEMP.

JULY 13.5AUG. 13.5

FIGURE 5.-Water temperatures (*C.) to 30 meters off Lake Area from 1954 to 1959. Mean monthlyair temperatures each year included.

595956 0 -62 -3

6.1 67 6.7 46 6.4 6A 7.2 9.11.4 12.0 17.2 16.1 17.2 16.1 5.1 10.6 15.9 1.6 16.3 17 5 14.

2A 1956 19590 ,5IDL 2T 6 100

15 Aug3 Aug AUG 24

3AIR TEMP.g AIR TEMP.

6.6 JULY 13.1 > > JULY 13A79 7 AUG. 11.3 :

6.9 6.9 6.9 5.0 5.0 5.2 6.1 6.4 67 6.7

n

u

0

1958

ANt TEMP.

AUG. 13.6

o

PW

c

a

''

10

the surface temperature was 9.10 C. and aslight metalimnion was still present from32 to 35 meters.

Differences in time of stratificationamong years appeared to be related tomean monthly air temperatures in Juneand July, shown on figure 5. Comparabledata for 1956 and 1959 both showed earliercomplete stratification than other years,

and the mean air temperatures for thesemonths were higher than recorded during

other years.

A comparison of the water levels ofYellowstone Lake from 1954 to 1959 (table3) with temperature stratification sug-

gests that the thickest epilimnion strataformed in August during the years ofhigh water such as 1954, 1956, and 1957.High water levels in 1959 were not, how-

ever, associated with a deep epilimnion.

All years of high water showed a more

abrupt temperature gradient in the meta-

limnion than the years of low water levels.

This condition is possibly caused by theheavier stream runoff during high water

level years, since stream temperatures

reach either close to or above epilimnion

temperatures soon after the first heavy

runoff period in early July, and stream

water, therefore, remains in and increases

the depth of the epilimnion layer. Thedata suggest that Yelowstone Lake circu-

lates twice a year and is a first-class di-mictic lake, as classified by Hutchinson(1957).

TABLE 3.-Mean monthly water levels in Yellow-stone Lake during June, July, August, andSept*mber,1954 to 1959

[In meters above the datum of 2,357.48 meters. Date collected byU.S. Geological Survey, 1952, 1953, 1954, and 1955, and unpub-lished data]

Year June July August September

1954---------------- 1.31 1.58 1.03 0.641955-------------- 1.07 1.24 0.90 0.571956---------------- 1.83 1.59 1.03 0. fi1957-------------- 1.37 11.44 10.97 0.631958---------------- 1.07 1.07 1075 1 0501959------------------------1.44 0.95

1 Data not complete.

Striking differences were evident be-

tween the thermal stratification patterns

in the West Thumb area and in the east

central part of the lake. West Thumb had

a thin epilimnion and an indistinct meta-

limnion, while the north central section

had a thick epilimnion and a very distinct

metalimnion (fig. 6). Intermediate con-

ditions existed at the neck of West Thumb

and in other sections of the lake. These

conditions were caused by the predomi-

nant winds from the south and southwest.

Data from drift bottles showed that sur-

face water is moved from West Thumb

to the central and north central parts of

the lake. This water movement probably

caused an upwelling in West Thumb and

a piling up of surface water in the eastern

part of the lake. Miller (1952) and Ayersand associates (1958) observed conditionssimilar to this in certain windy areas ofthe Great Lakes.

SECCHI DISK TRANSPARENCY

Readings with a Secchi disk during Au-gust, 1957 and 1959, varied from 6.5 to8.3 meters on overcast days and from 8.8

to 10.1 meters on clear days. Variations

among different stations in the lake werenot consistent and were not always related

to plankton abundance. These readingswere greater than those recorded by Pen-

nak (1955) for mountain lakes in Colo-rado, even though all were collected dur-

ing the August pulse of Anabaena or the

period of lowest transparency.

15

8

i E YEJUNE JULY AUGUST 'SEPT.

WEST THUMB 1956

- 10

8

JUNE JULY AUGUST SEPT.

EAST CENTRAL

JUNE JULY AUGUST SEPT,EAST CENTRAL

15

JUNE JULY AUGUST SEPT.

FIGURE 6.--Depths of isotherms (*C.) in West Thumb (station G) and the east central part ofYellowstone Lake (station C) during 1956 and 1959.

WATER CHEMISTRY

Yellowstone Lake is located approxi-mately on the Continental Divide anddrains a watershed of igneous rocks ofvolcanic origin. The chemical composi-tion of the water is "primitive" in thesense that it has not been altered by civili-zation, and it does not drain sedimentaryrocks.

Ionic composition.-The ionic composi-tion of the water classifies it as the bicar-bonate type, as defined by Rodhe (1949)(table 4). By arranging the major elec-trolytes into milliequivalents which pre-sents their reacting weight, major anionsexist in the order of HCO3, SO4, Cl. Themajor cations exist in the order Na, Ca,

Mg, K, which is indicative of soft waterdraining igneous rocks. This ionic com-position is similar to North German soft-water lakes summarized by Ohle (1955).

Bicarbonates ranged from 33 to 35mg./l. while most ionic concentrationswere relatively low. Several differenceswere apparent from a comparison of ionsfrom the four sections of the lake. In

general, West Thumb water had the high-

est values of Ca, Mg, Na, K, Cl, F, and B.Concentrations near the outlet and east ofStevenson Island were similar to eachother and the lowest values were in the

Southeast Arm. The higher values in

West Thumb are due both to an upwelling

11

Z

WEST THUMB 1959

H

CLW

c

12

TABLE 4.-Chemical analysis of water collected from 2 to 10 meters at four stations in YellowstoneLake on July 28, 1958

[Analyses by U.S. Geological Survey. Milliequivalents per liter (me./I.) presented for major cations and anions]

Analysis of water collected in-

Constituents Middle Southeast Middle West Four miles east of Near outletArm Thumb Stevenson Island

mg./I. me./l. mg./I. me./1. mg./l. me./1. mg./I. me./I.

Si02- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - 7.4.----------. . 7.2----------- 5.6----------- 5.7 ---...--..Fe----------.......------------------------.---. 0.02-------------0.012--......--.-.. -0.02----...------ 0.02 0-22.5Ca_-..--.--..--------..-----....-...-- ------.4.5 0.2245 5.0 0.2495 4.9 0.2445 4.5 0.2245Mg---------------------------------- 2.4 .1974 2.6 .2138 2.4 .1974 2.4 .1974Na---------....---------------------------- 8.0 .3478 9.4 .4087 9.1 .3957 8.9 .3870K -------------------------------------- 1.8 .0460 2.0 .0512 1.5 .0384 1.7 .6435HCOa--------------------------------------. 33 .5408 35 .5737 35 .5737 34 .5573S04.......------------------------------------- 8.0 .1666 8.0 .1666 9.8 .2040 7.8 .1624Cl--.-..---------------------------------------4.4 .1241 5.6 .1579 4.6 .1297 4.8 .1354F -..---..-..-.. 1..--- ----------------------------------- 0.5 ..---------.. . 0.6.------------0.52----------... 0.52- -----N03---------.. ---------------------- 0.-----------..--....... 0.1---....-.-.. -0.1 .. _-- 0.1 ....--B... - -- - - -- - - -- -------..---..-..-.._......_...... 0.08-..---....... -- 0.13 -__..__ 0.09 -_..__ 0.10 _.. _..Specific conductance (250*C.).-.---.....---..... 86.3-...---------96.4--.........---.92.2--...--.----.--93.2 ....pH . .----------------------------------- 6....- 6.8 - .----------- 6.7----------- 7.0 --------Dissolved solids residue on evaporation at

180*C .. .. ...--------------------------------- 54 ..-.-.-.. 57 ....-.- .. 55 ...-- ...-. 55 ..-----..-Hardness-- .. ..-------------------------------- 21 ----..-.-. 23 -..-.. -.._ 22 ....-..-.. 21 ....-...-.

influence caused by south and southwester-ly winds and possibly to hot spring activ-ity on the west shore and below the water

surface in West Thumb. Water from hotsprings is rich in SiO2, CO2, Na, and Cl.Hot spring water would presumably riseto the surface immediately, and any in-fluences would be recorded in our sam-pling. Upwelling water was consideredto be of greater importance, however,because data presented later on conduc-tivities indicated the increase in ionic con-centrations was related to the clockwisecirculation in West Thumb and not to theprincipal locality of hot spring activityin the extreme west end of the Thumb.Also, there is no evidence of local hotspring influence in the reading from theoutlet where Pelican Creek contributesmuch water from hot springs. HigherSiO 2 in the Southeast Arm is believed tobe due to the inflow of the YellowstoneRiver.

Conductivities.-Water conductivity isdirectly related to total dissolved solidsor total ion concentration. Conductivitiesfrom various stations at 5 and 10 meters(epilimnion) in Yellowstone Lake showedthat West Thumb usually showed thehighest readings, while Southeast Arm

showed the lowest readings (table 5). Ingeneral, the northern part of the lake

showed higher readings than the southernsection. The pattern of water circulationprobably causes this condition. The

monthly changes from July to Sep-tember were not consistent at any station,

although the highest epilimnion readingswere usually recorded immediately after

complete thermal stratification. In 1957this occurred in early July and in 1959it occurred in late June.

Conductivities usually increased withdepth, but not consistently so (table 6).The stations which were most influencedby the summer water circulation, such as

West Thumb, east of Dot Island, and ElkPoint, showed maximum readings in mid-August. Those protected stations, such aseast of Frank Island and in South Armhad minimum readings in August. Theepilimnion layers were more shallow (6-8m.) in the protected stations than in theexposed stations (12-15 m.), and it isreasonable to assume that a more concen-trated trophogenic zone would use upnutrients more rapidly than a broad zone.Also, the mixture of surface and deepwater in exposed stations would serve as

a method of replenishment of nutrients.

13

TABLE 5.-Conductivities (250 C.) in reciprocal megohms at different locations in Yellowstone Lakefrom 1957 to 1959

[Dates of collection for each month below each year. Figures represent average of readings at 5- and 10-meter depths]

June July August SeptemberMeans

ofLocation in lake 1957 1959 1957 1958 1959 1957 1958 1959 1957 1958 1959 read-

(June (June (July (July (July (Aug. (Aug. (Aug. (Sept. (Sept. (Aug. ings by20-25) 26- 2-10) 12-18) 14-22) 19-23) 6-14) 10-13) 15-18) 3-4) 30- area

July 1) Sept. 2)

Off Lake area---------------101 ---.--.. 94 91 85 104 89 88 90 91 84 92Five kilometers east of

Stevenson Island------.-.-.-.-.-.-.------ 84 103 86 91 101 89 57 63 91 92 86Off Dot Island--------------95 87 115 90 91 103 99 98 105 89 88 96Middle West Thumb-------- 101 91 123 -------- 83 99 ---.---. 103 105 92 91 99Off Frank Island------------97 86 105 86 86 80 80 76 62 86 74 83Mouth South Arm----------101 86 101.-------------- 78 93 76 64 86 75 84Mouth Southeast Arm ...-... 85 .-.---- .. 77 ---...-. 72 75 86 97 63 --..---. 93 81

Mean readings forperiod..--.. --. ------97 87 103 88 85 91 89 85 79 89 85 ...---..

TABLE 6.-Variations in conductivities (250 C.), in reciprocal megohms, collected during 1959 bydepth (meters) and location

June 26-July 1 July 29-August 3 August 10-13Location of collecting point

10 15 30 46 61 10 15 30 46 61 0 15 30 46 61 76 89

Middle West Thumb.... ...-------------------------- 91 91 93 100 92 89 89 93 96 97 .--- 103 104 107 106 --. --

East of Dot Island.--._.---------------------------88 96 90 94 95 86 85 89 88.----.----.98 108 105 98 103 -..Off Elk Point .. . _ ._..-------------------------------91 88 87 90 88 75 73------------95 93 95 96 91 89 89Ten kilometers east of Stevenson Island-.-.-.----_--84 88 87 97 --- - 73 78 79 79 78 87 87 89 91 91 91 105Mid South Arm.. . .. _-----------------------------86 91 88 86 88 88 88 89 89 88 76 75 76 -Five kilometers east of Frank Island _.--------------86 90 107 90 ---- 86 87------------76 80 78 72 76 74 -

Mean by depth and sampling period---------88 91 92 93 91 83 83 88 88 88 84 89 92 94 92 89 97

The distribution of conductivities bydepth in and near West Thumb was mea-sured on July 29, 1959, to determine how

surface and bottom current measurementswere related to conductivities (fig. 7).The data clearly demonstrated a clockwisecirculation with conductivities increasingfrom the south to the north section of thearea. The accumulation of additional nu-trients from subsurface waters or upwell-ing can account for the increase in nu-trients as water circulates in West Thumb.The hot spring activity is concentrated inthe western part of the thumb. Both hotsprings and upwelling probably accountedfor the increases in the western and north-ern stations.

Alkalinity. - Bicarbonate alkalinitiesmeasured during 1957 ranged from 22 to

41 mg./1., usually varying from 30 to 33mg./1. The readings showed the same

general seasonal, horizontal, and vertical

distributions as conductivities.Dissolved oxygen.-Theinemann (1928)

showed that lake morphometry has a

strong bearing on oxygen concentrations,

and that large, deep lakes rarely develop

deficits. In 1957 oxygen was measured at

all stations of the lake from mid-June tomid-September, and most readings down

to 60 meters were near saturation. Someseasonal measurements of oxygen concen-

trations as compared with saturationvalues are shown in table 7, which alsopresents the lowest dissolved oxygen read-ing recorded, that of 53 percent saturationon July 25, 1957.

14

TABLE 7.-Some summer dissolved oxygen concentrations (DO) from Yellowstone Lake during1957 and 1959, compared with saturation (S) values

[Values in milligrams per liter and adjusted for altitude. Collected at stations A and B]

Depth June 20, 1957 July 25, 1957 Aug. 20, 1957 Sept. 18, 1957 Sept. 10, 1959

DO S DO S DO S DO S DO S

0meters-------- -------- 10.0 9.5 7.4 7.7 7.2 7.2 7.8 7.3 ------..-- __-- _----4.5meters----------------10.0 9.5 7.4 7.8 7.2 7.3 8.2 7.5 ----.. - --. ----9meters-----------------10.2 9.6----- ----- ---------- 8.0 7.2 8.0 7.5 ---- .---- ...-- ..---15 meters------------ ---------- -------------------------------------------------- - ----- -------. 8.5 8.820 meters----------------- 9.8 9.7-7..---.--------------------------------8.4 7.9 .22 meters. . ..-------------.------------------- 8.3 8.6 8.3 8.3- -- .-- -- 8.3 9.230meters-----------------9.6 8.9.-----------.---------- 8.3 8.6.---------..-.. ----.-- 8.0 9.345 meters---..--------------------------------4.9 9.2 8.3 8.7.--------------------8.7 9.260 meters-....----------.--------------------------------------- 8.2 9.3-----------.---------- 8.2 9.376 meters------------...--.--. --------- -------.----------.------------------..---------- -------------------- 8.0 9.592 meters------------.......- .....---------- ..----------------.. ----------.------------------------------ 6.2 9.5

Depth Conductivity10 90

Dh 9 Depth Conductivity46 97 10 86

15 8530 8946 88

Depth Conductivity Dot Island10 8815 88

N

Depth Conductivity10 8915 89

46 96

KILO METE RS

Depth Conductivity

15 8

FIGURE 7.--Conductivities at different depths (meters) in West Thumb and near Dot Island onJuly 29, 1959.

Weather conditions in the summer of deficit at 92 meters of 64 percent satura-

1959 caused the water to stratify earlier tion. There is little question that duringthan in 1957 or 1958 (fig. 5), which could the short (approximately 45 days) periodpresumably allow an oxygen deficit to in- of complete stratification, a partial oxygencrease. Measurements made on August deficit develops below 30 meters in Yellow-10, 1959, near Stevenson Island showed a stone Lake. The relatively short period

15

of complete stratification, however, pre-vents a severe depletion that would in-fluence the composition of bottom faunaor would even prevent fish from inhabit-ing this zone. Pennak (1955) found agreater progressive oxygen deficiency dur-ing the summer by depth in Bear Lake,Colo., than was present in YellowstoneLake. His data on phytoplankton andcarbon dioxide, however, suggested higherbiological activity for Bear Lake.

Free carbon dioxide.-Free carbon di-oxide existed in all samples collected dur-ing 1957. Readings ranged from 1.5p.p.m. on the surface to 13.3 p.p.m., at 61meters (table 8). The water depth, which

showed a pronounced increase in carbon-dioxide content (above 10 p.p.m.), de-creased from 45 meters in July to 19 inAugust. The depth of 19 m. in Augustwas just below the metalimnion.

TABLE 8.-Free carbon dioxide concentrations inmg./t., by month and depth during summerof 1957

[Mean of readings at various stations]

Depth June July August September

0Ometers------------ 3.5 3.5 ------ 2.05meters-----------3.8 4.3 3.5 3.410 meters----------- 4.0 5.4 6.0 3.5

l9meters----------------------------12.5 4.0.30 meters.------------------ 3.0-45 meters---------- ---------- 11.5 12.8 ------61 meters--------- -------- ---------- 13.3------

BOTTOM TYPES

Types and distribution.-Bottom typesin Yellowstone Lake consist of boulders,rubble, black obsidian sand, and fine clays

with organic matter. Boulders are exposedin quantity only on the east shore and on

the windward shore of Frank Island.Rubble areas are concentrated on the east

shore and in a few exposed sections of the

South and Southeast Arms. The mostcommon shallow (less than 2 m.) waterbottom type is black obsidian sand whichcontains less than one percent organic mat-ter. Silty loams with varying amounts oforganic matter make up more than 95 per-cent of the bottom type of YellowstoneLake. The amount of organic matter in

the bottom sediments increases with depth,with a correlation coefficient from 59 sam-ples of 0.80 (table 9). In general, bottomsoils below 50 m. possess more than 5 per-cent organic matter, while bottom soils be-tween 25 and 50 meters have more than 2percent organic matter. There are manyexceptions to this condition which can beexplained by water movements. Areaswith a greater movement or exchange ofwater, such as the Southeast Arm with theinflowing Yellowstone River, allow a

smaller amount of organic matter to ac-cumulate than do other similar areas, suchas the South Arm, with less water ex-change. Water currents, as described ear-lier, prevented organic matter from ac-cumulating in as great a quantity in theneck of West Thumb as in areas of similardepth inside West Thumb. Greater thanaverage amounts of organic matter ac-cumulated around Sand Point, where an

eddy current is probably present, as shownfrom several drift recoveries. Organicmatter deposition on the lake bottom ofless than 20 meters in depth has much in-fluence on fish distribution and fish foodproduction. Those areas with much or-

ganic matter had large stands of aquaticplants, which had high standing crops oftendipedids and Gammarus. As shownlater, the latter organisms are importantfoods for cutthroat trout.

Chemical properties.-Bottom-sedimentsamples were analyzed to determine whatdifferences in organic carbon, nitrogen,P205, and cation exchange existed in sec-tions of the lake by depth. Soil sampleswere all classified as silt loam in agricul-tural terminology and were typical of the

16

soft bottom sediments. The shallow sta- respect to growth conditions for aquatictions had greater amounts of organic car- plants, both Roelofs (1944) and Wohl-bon and less phosphate (table 10) than the schag (1950) found that organic matterdeeper stations. The cation exchange ca- content and site conditions were fre-pacity was greater in the deeper stations. quently of greater importance than phos-Nitrogen readings were not related to phates, nitrates, or other nutrients, anddepth. The data show a greater utiliza- these same factors appear to be most im-tion of nutrients in shallow water. With portant in Yellowstone Lake.

TABLE 9.-Percentage of organic matter in bottom soils by location and depth at 59 points in 13sections of Yellowstone Lake

Percentage PercentageLocation and depth of organic Location and depth of organic

matter matter

West Thumb: South end of Southeast Arm:25 meters------------------------- ---------- 3.22 32 meters--.. .---...-------------.. ---.. --- 4.6452 meters.-------------------------------------4.13 40 meters----------------------------------- 3.2070 meters.- .---------------------------------- 6.72 49 meters....----------------------------------- 3.5871 meters . . ..----------------------------------- 6.33 37 meters..------------------------------------2.0875 meters . . ..----------------------------------- 5.28 49 meters--------------------------------------1.9485 meters ...----------------------------------- 6.14 1imeter ...------------------- ------------------ 0.8988 meters._-- ._---____...-.. ---___._-_.___- 5.64 Mouth of South Arm:92 meters._.------------------------------------5.81 88 meters ------------------ ----------------- 3.5494 meters. . ..----------------------------------- 6.38 53 meters.-.----------------------------------- 7.22

Neck of West Thumb: 58 meters....---------.. --_..--..-----.... ---- 6.692 meters_--.----------....-..-....... ---__.... 0.31 South end of South Arm:13 meters. ...----------------------------------- 1.93 15meters..------------------------------------. 9.1237 meters. ..----------------------------------- 1.72 6 meters.- ------------------------------ 6.40

Rock Point to Wolf Point: Frank Islandto ElkPoint:53 meters_------------------------------------_1.75toEkPi:22meters---.----------------------- -------- 2.67 3 meters...------------------------------------ 0.22706mmest ------- ~---------------~-----------5

64 e e s. . .. . .. .. _ .. ... _ _ ._ _ _ . 0 88 m eters 5.44640meters------------------------8mtr------------------------------------5.4264 ~ ~ ~ ~ ~ ~ ~ ~ 8 meters-------------------64 88mtr------------------------------------ 5.44Mouth of Flat: 79 meters------------------------------------ 5.85

33 meters-.....----..-. --... _- -.- _-_-_-_...-.---6.40 Sand Point to Elk Point:11 meters...------------------------------------1.48 92 meters- ..------------------------------- 6.71

Eagle Bay to Signal Point: imeter--------------------------------------____ 3.666 meters.--------------------------------------1.91 79 meters ------------------------- ---------- 8.3363 meters------------------------- ----------- 6.02 82meters-------------------------------- ----- 5.9012 meters--.------------------------------------2.49 82meters------------------------------------ 6.0067 meters . . ..----------------------------------- 4.45 81 meters . . ..----------------------------------- 6.2475 meters------------------------------------ 6.19 46 meters------------------------------------- 4.6875 meters-----------------------------------6.23 Stevenson Island to Steamboat Point:

76 meters . . ..----------------------------------- 6.43Mouth of Southeast Arm: 85 meters_---_-__-__-__-.. --._ ... ----.. ---.. 6.31

40 meters--------------------------------- 4.20 87 meters--------------------------------------- 6.8869 meters...----.--------...-_..---.....---_ - 3.54 StevensonIsland to outlet:76 meters-------------- .------------ 3.23 31 meters. ..------------------------------------ 2.2949 meters----..---..--------- ----..-.... ---_ 3.04 55 meters-- ..--------------------------------------- 6.725 meters.---.- .. ..--------------------- ----- 1.22 53 meters------------------------------------ 6.30

TABLE 1O.-Some chemical properties of six samples of bottom soils (silt loam) in Yellowstone Lake,collected August 15-30, 1958

Depth Organic Nitrogen POs Cation OrganicLocation (meters) pH carbon (percent) C/N ratio p.p.m. exchange matter

(percent) capacity (percent)

Southeast Arm------..... ---- --- 40 6. 5 2. 60 . 325 8.0 68 47. 6 7. 26Southeast Arm. .--- ---------- - 70 5. 7--------------. 262-----------------118 58.0...---- ...South Arm..-------------------- 15 6.8 3.70 .562 6.5 45 42.0 6.36South Arm- ------------------- 3 6.0 3.38 .392 8.6 41 40.2 5.81East of Stevenson Island-_..._ 88 6.1 2.24 .415 5.3 280 54.0 3.85

AQUATIC PLANTS

The distribution and relative abundance which are important cutthroat troutof aquatic plants has a great bearing on foods. Collections of aquatic plants werethe production of those bottom organisms made with a plant hook and while col-

17

lecting bottom samples with an Ekmandredge. The species collected and theirdepth distributions were as follows:

MetersPotamogeton richardsonii--------------1- 5Potamogeton praelongus--------------5-10Potamogeton pusillus-----------------1-18Potarnogeton robbinsii------------.--.--.5-10Potamogeton gramineous var. gramini-

folius -----------------------------. 0- 3Lemna trisulca------------- -------- 2-18Ceratophyllum demersum-------------1-17Najas fewilis- _.-----------------------2- 8Myriophyllum exalbescens-------------1- 5Ranunculus aquaticus---------------0.5- 5Fontinalis sp.-----------------------2Elodea canadensis-------------------0- 2Nitella fevilis-----------------------1Eleocharis sp.--------------------- 0.5- 1

Meterssagittaria cuneata------------------0.5Sparganium sp.----------------------0- 2

Aquatic plant beds were generally re-stricted to protected littoral areas whereorganic matter was allowed to accumulateand were not present below a depth of 18meters. The most extensive beds were lo-cated at 1 to 10 meter depths in South andSoutheast Arms, on the lee sides ofStevenson and Frank Islands, and nearthe outlet. On windy, exposed shorelines,such as on the east shore or on the wind-ward side of Stevenson Island, plant bedswere dense from 7 to 15 meters. Aquaticplants in West Thumb were more abun-dant on the protected south shore than onthe exposed north shore.

PLANKTON

Only general statements can be madeabout the abundance, seasonal changes,and genera of phytoplankton from sam-ples collected in 1956. Plankton collec-tions in 1957 and 1958 were aimed prima-rily at sampling zooplankters.

Phytoplankton.-The siliceous nature ofthe watershed undoubtedly caused thepredominance of diatoms in the phyto-plankton. Except for an annual Augustpulse of Anabaena, various diatoms suchas Asterionella, Melosira, and Stephano-

discus, dominated the phytoplankton flora

(table 11). A dense pulse of Asterionella

occurred in 1955, 1956, 1957, and 1958,soon after the ice left in early June.

This pulse extended to 35 m. in depth and

was associated with high water levels due

to melting snows. Melosira formed a pulseto a lesser extent in late July and remained

abundant until September. Anabaena

formed a heavy pulse during the first twoweeks of August during all years meas-

ured. This pulse caused a green cast in

TABLE 11.-Mean number of phytoplankton cells collected per liter (to nearest whole number) fromall sections of Yellowstone Lake, June 28 to August 31, 1956

[Each sample represents one plankton haul from 10 meters to surface]

Number collected during period-

Alga genus June 28- July 10-17 July 20-24 July 30-31 Aug. 1-3 Aug. 7-10 Aug. 15-16 Aug. 20-24 Aug. 29-31July 6 (10 (14 (13 (5 (7 (11 (5 (8 (3samples) samples) samples) samples) samples) samples) samples) samples) samples)

Asterionella---.-----128, 711 115, 896 24, 764 54, 955 2, 349 961 1, 566 583 1,073Stephanodiscus---- 68 74 41 18 34 0 10 88 48Melosira-..-----..--. 2, 138 903 61 0 260 132 2, 125 48 128Staurastrum.--... 10 8 5 1 5 40 2 98 1Coelastrum..--... 0 14 14 0 12 4 1 20 82Anabaena------- 889 123 591 7,420 16, 807 11, 830 17, 998 389 0Other ......-- 1 11 11 1 3 2 4 33 6

1 Includes Coelosphaerium, Pleurococcus, Cosmariurn, Navicula, Fragillaria, Ulothrix, Closterium, Pinnularia, Suriella, Compylo-discus, unidentified desmids.

18

the water due to small clumps of algalfilaments. Data from 1956 showed WestThumb to be the most productive sectionof the lake with Southeast Arm the leastproductive. Stations in the north and cen-tral areas of the lake were similar to thosein South Arm and around Frank Island.These pulses were similar to those reportedby Pennak (1955) for Grand Lake, Colo.,although they were less intensive.

Zooplankton.-The zooplankton faunaconsisted principally of Conochilws wni-cornis, Diaptomus shoshone, Daphniaschoedleri, and nauplii of Diaptomus.Vorticella occurred commonly during theAnabaena pulse in August, but no otherspecies were commonly observed. A fewCyclops were identified, but they occurredso rarely (less than 0.1 percent) that theyhave been included with Diaptomus forpurposes of enumeration. Also, a fewDiaptomns minn u t u s were identified.

Forbes (1893) reported few Cyclops, butvast numbers of Diaptomus. Keratellawas collected occasionally, but the rotifer

fauna consisted almost entirely of Co-nochilus unicorns. Pennak (1957) foundthat one dominant species of copepod,cladoceran, or rotifer, was usually presentin Colorado limnetic communities.

The vertical distributions of zooplank-ters showed that the depth range wherethe largest number occurred extendedfrom 5 to 18 meters (table 12). Diaptomeswere most abundant during July at 5 and10 meters, but were present to 45 meters.Nauplii were most abundant during lateJuly at the depth range of 15 to 23 meters.Daphnia were never abundant from anyplankton samples, but increased in num-ber in September. Daphnia schoedleri,the only cladoceran collected in Yellow-stone Lake, is an inshore swarming speciesand was not sampled adequately at the

TABLE 12.-Verical distribution of Diaptomus (Di), nauplii of Diaptomus (N), Daphnia (Da),and rotifers (R) during 1957 and 1958

[Number per liter is derived from 10-liter samples combined from all limnological stations in Yellowstone Lake. Number of samplesshown in parentheses. Diaptomus counts include a few Cyclops]

August August September MeanDepth and plankter June 1-30 July 1-15 July 16-30 1-15 16-31 3-18 number

per sample

0 meters--------------------------------- (8) (12) (4) (3) (3) (15) (45)Di-------------------------------- -- 8.8 7.7 5.6 0.9 3.4 4.9 6.0N-----------------------------.------ 4.9 6.1 7.4 1.2 2.6 5.8 5.3Da---------------------------------- 0.2 0.1 0.1 0.3 0.1 2.3 0.9R----------------------------------- -0.2 0.5 37.2 0 5.5 2.4 4.6

5 meters....------------------------------- (7) (11) (8) (11) (12) (16) (65)Di..------.--------...-..-----.-- 10.5 18.7 21.7 13.7 13.2 14.9 15.4N----------------------- ------------ 8.7 11.8 10.2 10.9 12.0 13.8 11.6Da--------------------------------- - 0.2 0.3 0.5 0.7 0.9 3.1 1.2R_-....------- .....------......-------- 4.4 15.5 151.9 193.0 41.3 17.7 66.4

10 meters-------------------------------- (7) (12) (8) (15) (11) (12) (65)D.--------..--------.-.--- 15.4 9.4 13.2 8.1 10.4 14.2 11.3N-..-.-..-.------------- ....-------- 8.4 10.7 15.8 5.8 19.9 14.0 12.1Da---------------------------------- 0 0 0 1.7 0.8 3.5 1.2R----------------------------..---- -- 1.2 17.2 85.0 61.5 51.2 22.5 40.8

15-18 meters--------------------------.------------ (5) (3) (15) (8) (9) (40)Di----------------------------- --------------- 3.2 5.1 3.4 5.0 11.7 5.7N---------------------------..---..-.----.----- 7.7 46.9 15.2 16.2 18.1 17.5Da-------------------------- -------- - -------- 0 0.4 0.1 0.7 1.1 0.5R--------------------------------------------- 0.3 168.0 53.2 59.1 10.6 46.8

21-23 meters----.-------------------------------------------- (1) (6) (1) (2) (10)Di------------------------------------------- --------- 3.5 2.1 2.7 8.9 3.7N-----------------------------------------.....------- 55.7 8.0 17.7 15.0 15.1Da--------------------------- ----------- ----------- 0 0 0 2.1 0.2R------------------------------------------..-.-.. --- 2.3 1.4 4.2 24.3 6.3

30 meters.------------------------------ ----------- (2) (2) (6) ...- .-- (5) (15)Di--------------------------------- --------- 10.5 4.3 1.2- - ------- 4.2 3.9N----------------------- ------------- ---..- 11.0 17.4 2.1 9.1 7.7Da-------------------------------------------- 0 0 .0.1 -------- -- 0.6 0.2R------------------------------- -------------- 3.5 2.2 2.7 ------------ 2.0 2.5

45 meters-- ------------------------- ----------- -(1) --- .. (1) (1) .--- (3)Di------------------- ------------ --------- -- 8.0 ------------- 1.2 2.4 -------- 3.9N--------------...----- ---- -------.. 6.7------ .- 4.1 0.------- 3.8Da----------------------------------. - --------- 0 .-----. 0 0 - ----- 0R-.--------------------------------- ------.. 0 -------- 0.6 0 _---------- 0.2

19

various stations for this reason. In lateAugust, 1959, two large swarms coveringan estimated 14,000 cubic meters eachwere observed, and each swarm contained400 to 500 Daphnia per liter. These con-centrations were located by anglers whowere taking advantage of the fish concen-trations in these areas. The intensity ofthese swarms probably varies annually,since such large concentrations wouldprobably have been observed previously.Tonolli (1954) found that annual clado-ceran populations varied greatly in Italianalpine lakes due to meteorological condi-tions. He found that warmer weatherincreased populations significantly, andrelated these conditions to the velocity ofcladoceran developmental processes. Theconcentration in 1959 may have been dueto the fact that the epilimnion formedearlier than in other years observed (fig.5). Rotifers were abundant from themiddle of July to mid-August, and theyextended in abundance down to 18 meters.Those plankton organisms important asfood for cutthroat trout did not extend inabundance below 18 meters in depth.

The abundance of zooplankters amongstdifferent sampling stations can be com-pared from our data on table 13. TheSoutheast Arm (Station J) showed thelowest numbers. This fact is probably dueto the great exchange of water from the in-flowing Yellowstone River and to the lowamount of nutrients in this arm. Dia-ptomus and nauplii were never abundant

in this section of the lake. The WestThumb section showed poor standing cropsand this was due to the continual removalof surface water from this area as shownboth by current and temperature informa-

tion. The heaviest populations were inthe northeast and central parts of the lakewhere surface water accumulates fromwind action. McMahon (1954) found thatthe movement of surface water due to windaction also concentrated entomostracan

plankters in the lee sections of LakelseLake, British Columbia, Canada. The ex-treme north section of the lake and theSouth Arm were similar in numbers col-lected. The large number at Station F onthe lee side of Frank Island is believed tobe due to its protected nature.

TABLE 13.-Mean number of organisms per literfrom June 15 to September 15, 1957, among 10sampling stations in Yellowstone Lake

[All samples collected at 5- and 10-meter depths and separatedas Diaptomus (Di), nauplii of Diaptomus (N), Daphnia (Da),and rotifers (R). Sampling stations shown in figure 1]

NumberMonth and station of Di N Da R

samples

June:

C----------D -- - - - -

------------J------------

July:

C-----------D - - - -- - -

I-----------J-----------

August:A -- - - - - -B -- - - - - -C-----------D -- - - - - -E -- - - - - -F -- - - - - -0 - - - -- - -H -- - - - - -------------

J------------September.

A -- - - - - -B -- - - - - -C----------D -- - - - - -E -- - - - - -F -- - - - - -a----------

*H -- -- - - -I------- ----J-----------

Mean, all samples:A -- - -- - -B -- - - - - -C----------D -- - - - - -E -- - - - - -F -- - - - - -a ----- --H -- - - - - -I-----------J-----------

22

2

2242222324

44444342444

2

2

22

1.43.0

22. 132.0

11.720. 0

0.3

16.322. 521.221.620. 519. 512. 922. 518.88. 7

13. 025. 713. 713. 413. 715.810.411. 48.84.6

6. 13.2

15. 15.6

8.210. 97.3

17.95.2

1.20.7

15.020. 1

11.414. 40

10.213.321.614. 334.36.3

10.812. 817.44. 4

8.815.315.314. 712. 713. 76.6

24. 414.89.4

8.56.88.03. 7

13.43. 2

16. 121.310.4

00

0.0.

00.200.200000

0.1.2

0.81.65.80. 10.71. 10.900.52.1

1.403. 70.9

1.82.00.91. 16. 5

00

9.40

00

39. 17.0

353. 610. 157. 7

253.071.442.153.055. 5

119.484.161.8

166.280.5

170.836.5

117. 136.650. 9

39. 322. 8

09.3

24. 46.28. 4

11.29. 1

AllDi N Da R organ-

isms

11.017.416. 013. 518. 018. 411.414. 515.35.4

8.010.716.11.819. 512. 86.9

17.016.36.0

0.60. 73.80.30.30.80.90.20.61.8

59.441.5

136.388. 053. 7

135. 538. 054. 433.639. 5

79.070.3

172.2113. 691. 5

167. 557.286. 165. 852. 7

20

BENTHOS

Studies on benthos included the deter-mination of vertical and horizontal dis-tribution of the common organisms. Thesampling of hard-botton areas of the lit-toral zone was sparse, but observation didnot disclose any great concentrations oforganisms in these areas, possibly becauseof heavy molar action. Undoubtedly, thenumbers of Ephemeroptera and Trichop-tera were much higher than our samplingdisclosed. The common organisms pres-ent, their depth distribution, and abun-dance were as follows:

Lumbriculidae (usually Limnodrilus sp.) -sparsely present 0 to 95 meters on silty bottom.

Tubifex tubifex (0. F. Muller) -only occurredin abundance in clumps on delta of YellowstoneRiver in Southeast Arm-10 meters.

Helobdella stagnalis (Linnaeus)-sparsely dis-tributed in entire lake down to 15 meters onsilt bottom.

Hyallela azteca (Saussure)-common from 0to 15 meters around aquatic plant bed.

Gammarus lacustris (Sars) -abundant on pro-tected shores down to 30 meters-present to 43meters-most abundant around aquatic plantbeds.

Ephemerella sp.-common only on poorlysampled, rocky shorelines, from 0 to 8 meters.

Psychomyia sp.-rare from 1 to 5 meters.Dicosmoecus sp.-common from 0 to 25 meters.

Tendipes (Tendipes)-abundant from 0 to 30meters.

Tendipes (Limnochironomus) - moderatelyabundant to 90 meters.

Prodiamesa-present at all depths and mostabundant from 70 to 90 meters.

Procladius-moderately abundant to 30 meters.Pisidium-present from 0 to 30 meters.Sphaerium-present from 20 to 60 meters.

The standing crops of benthic organisms

at various depth ranges showed that the

6- to 11-meter range was the most produc-

tive in number, with a mean of 1,036 or-

ganisms per square meter (table 14). This

large production was composed princi-pally of Oligochaetes (Tubifew), Gam-marus, and Hyallela. Gammarus ex-tended in moderate abundance to 23meters, but the largest concentration was

in the 1- to 5-meter range. Tendipedids

were most abundant in the 6- to 11-meter

range, but were numerous down to 92

meters. Sphaeriids were common at 1- to

5-meters. The highest numbers of Gam-marus were found around aquatic plantbeds of Potamogeton pusillus and Lemnatrisulca, but fish predation (to be discussedlater) undoubtedly influenced these num-

bers.

TABLE 14.-Mean number of bottom organisms collected per square meter at various depth rangesin Yellowstone Lake, June 15 to September 18, 1957, and July 15 to August 30, 1958

[N=number collected; F=frequency of occurrence]

Collected at depths of-

Organism 0-5 meters 6-11 meters 12-17 meters 18-23 meters 24-58 meters 61-92 meters(16 samples) (32 samples) (30 samples) (11 samples) (21 samples) (5 samples)

N F N F N F N F N F N F

Oligocheata------------------ 5 4 366 14 23 15 36 7 42 14 39 3Hirudinea----------------- -20 6 70 21 7 6 0 0 13 3 4 1phaeriidae----------------- 22 7 4 3 4 5 4 1 4 2 0 0

Tendipedidae---------- 34 8 83 20 295 25 245 10 497 21 280 3(ammarus lacustris----------537 15 295 28 158 21 178 6 54 9 0 0Hyallela azteca--------------153 8 216 14 84 6 3 1 0 0 0 0Trichoptera----------------- 11 4 2 2 0 0 0 0 0 0 0 0Ephemeroptera------------- 2 2 0 0 0 0 0 0 0 0 0 0Hydracarina---------------- 3 1 0 0 0 0 0 0 0 0 0 0Gastropoda----------------- -1 1 0 0 1 2 0 0 0 0 0 0

Total---------------- 788.-------- 1,036---------572 -------- 466-..-------610.--------323 - .

21

The number of organisms per squaremeter is low when compared with thosefound in similar studies. Reimers,Maciolek, and Pister (1955) reportedmore organisms per unit area for their

lakes in the Sierras, although only LakeMildred contained many amphipods. Thenumber per square meter also was lower

down to 60 meters than Rawson (1953)reported for Great Slave Lake. The latter

author also compared the percentage com-

position of the dominant kinds of bottomorganisms from several large North

American lakes; the Yellowstone Lakebottom fauna was similar, except thatGammarus replaced Pontoporeia as thedominant amphipod. Calhoun (1944a)found a higher standing crop in BlueLake, Calif., than in Yellowstone, but

found a rapid drop in production below20 meters.

The number of bottom organisms in dif-ferent areas of Yellowstone Lake wascompared from 2 to 15 meters (table 15).The largest numbers were collected offLake Area in the northern area of thelake. The lowest number was off ClearCreek, which is an exposed wave-sweptshoreline where organic matter does notaccumulate. A lower number than wouldbe expected was present in the South Armand near Frank Island. Most of the dif-ferences between these latter two stationsand lake were in numbers of Gammarus,which is an important food for cutthroattrout. The low production in SoutheastArm was possibly due to a large accumu-lation of fine silt and to the shiftingbottom.

TABLE 15.-Number of bottom organisms per square meter at six stations in Yellowstone Lake in 1958[Samples ranged in depth from 2 to 15 meters at about 3-meter intervals]

West Thumb Southeast Arm South Arm Off Clear North side of Lake Area,off Solution off Trail Creek, near Peale Creek, July 25; Frank Island, July 28 and

Organism Creek, August July 31; bottom Island, August bottom sand, August 7; bot- August 15; bot-5; bottom sand fine silt with 12; bottom sand, gravel, little tom sand, tom sand,with little silt little sand (6 gravel, and silt silt (4 samples) gravel, and silt gravel, and silt

(6 samples) samples) (6 samples) (5 samples) (6 samples)

Oligochaeta-------- ---------- -- 0 2 20 0 4 24Hirudinea-------------------- -- 0 0 32 11 32 48Hyallela azteca------------------ 203 34 54 30 176 602Gammarus lacustris------------- 317 99 206 99 435 919Hydracarina.------------------... 7 0 0 0 0 11Ephemeroptera----------------- 4 0 0 0 0 3Trichoptera------------------- - 11 2 0 0 0 0Tendipedidae------------------- 39 66 63 27 54 108Gastropoda--------------------- 0 2 0 0 0 0Sphaeriidae------------------- 4 11 18 0 15 18

Total--------------------- 585 216 393 169 716 1,733Mean number per sample- 99. 5 36. 0 65. 5 42. 3 143. 2 288. 8

VERTICAL DISTRIBUTION OF CUTTHROAT TROUT

During the open-water season, cutthroattrout in Yellowstone Lake rarely venturebelow 20-meter depths. During 1957 and1958 more than 99 percent of the cut-throat trout were captured in the upper25 meters of water, in 92 gill-net sets(table 16). Of the total, 63 percent werecollected from the surface to 15 meters,and no trout were captured below 30meters. This type of vertical distributionof cutthroat trout has been documented

by McConnell, Clark, and Sigler (1957)for Bear Lake in Utah and Idaho, al-though the cutthroat population was

small.Our data do not conclusively show great

variations in vertical distribution among

different size groups, but small trout

(155-200 mm., predominently age group

II) frequented water below 20 meters

more than did larger trout.

22

TABLE 16.-Number of cutthroat by size groups captured by 92 overnight experimental gill-net setsat different depth ranges in Yellowstone Lake during July and August of 1957 and 1958

Number in size group range-Depth N _ber _Total

Less than 105-150 155-200 205-250 255-300 305-350 355-400 Above100 mm. mm. mm. mm. mm. mm. mm. 400 mm.

0-5 meters-- .-------------- 11 0 0 25 30 45 55 60 4 2196-9 meters--------------- -11 0 0 51 30 36 57 39 1 21410-15 meters-------------- 22 0 0 40 16 21 38 43 2 16017-20 meters-------------- 11 0 0 6 3 3 25 28 0 6521-25 meters----.---------- 22 1 0 23 3 0 10 9 0 4626-30 meters--------------8 0 0 1 2 1 1 1 0 631-46meters..-.....-... --.. -7 0 0 0 0 0 0 0 0 0

Total---------------92 1 0 146 84 106 186 180 7 710

FOOD OF CUTTHROAT TROUT

The most abundant organisms found inthe stomachs of cutthroat trout in Yellow-stone Lake were Daphnia shoedleri,Gammarus lacustris, and various speciesof Tendipedidae (table 17). Diaptomusshoshone, Trichoptera, Plecoptera, andEphemeroptera occurred in fewer stom-

achs. The seasonal changes in feedinghabits showed that Gammarus was mostimportant in mid-July, but declined inimportance in August. The number ofDaphnia increased from July to Octoberand is believed due to the swarming habitduring the latter part of the summer.Tendipedidae pupae and adults were com-mon in stomachs during July or when themajor emergences occurred. Tendipedidaelarvae were not utilized heavily. Diap-tomus occurred in few stomachs in July,but assumed greater importance later inthe season. Only three stomachs out of409 contained fish, and these were cut-throat trout.

Feeding habits of trout by size groupsshowed that both Gammarus lacustris andDaphnia schoedleri were the most com-monly utilized foods of all sizes of trout(table 18). There was a gradual transi-

tion in the range of 275 to 325 mm. from azooplankton-bottom fauna diet to a pre-

dominantly bottom fauna diet. Diapto-

mws were rarely utilized above 250 mm.,

and Ephemerella nymphs and Trichoptera

were most important among large fish.

From our knowledge of the distribution

of the food organisms in the lake, it ap-pears that small trout feed both in thelimnetic and littoral zones. while largetrout feed almost entirely in the littoralzone. Daphnia schoedleri, the only zoo-plankter found in many stomachs of large

trout, is an inshore swarming species.

Differences in feeding habits in two sec-tions of Yellowstone Lake were demon-

strated from the stomach contents of 344cutthroat trout caught at Fishing Bridgeand West Thumb docks (table 19). Stom-achs from fish caught at Fishing Bridgecontained many stream organisms and

some trout eggs. Trout from West Thumbutilized terrestrial organisms more so thantrout from Fishing Bridge. Many stom-achs from Fishing Bridge contained both

Diaptomus or Daphnia and stream bot-tom insects, which indicates that cutthroattrout can rapidly change their feeding

23

habits to utilize a different type of food. predominant south and southwesterlyThe large number of terrestrial insects winds from the lodgepole-pine forests.from West Thumb included the wind- Calhoun (1944b) found that cutthroatblown bark beetles, wasps, and others, trout (Salmo clarkii henshawi) utilizedwhich were carried into the water by the Tendipes larvae more commonly than

TABLE 17.-Stomach content of 409 cutthroat trout captured by gill net8, by time of capture in 1958

[All sizes combined. P=percent of stomachs containing organisms; M=mean number, to nearest 1.0, of food organisms per stomach.Collected from South Arm, Lake Area, West Thumb, and Southeast Arm]

July 15-31 August 1-15 August 16-31 October 15

Food organism (238 fish) (100 fish) (43 fish) (28 fish)

P M P M P M P M

Daphnia...-.--------------------------------- 19.7 209 24.0 295 37.2 72 82.1 976Diaptomus-------------------------------- 2.1 223 3.0 541 7.0 158 14.2 93Gammarus lacustris--..----------------------- 56.7 25 41.0 27 30.2 9 17.8 105Hyallela azteca..-----------------------.------1.3 5 1.0 15 2.3 65 0 0Hydracarina------------------------------- 2.5 5 0 0 0 0 0 0Plecoptera---------------------------------1.3 1 2.0 2 4.7 1 0 0Ephemerella.. ..------------------------------.. 10.1 13 3.0 3 0 0 0 0Trichoptera . ..-------------------------------- 6.3 13 8.0 4 0 0 0 0Tendipes larva-------------------------------- 8.8 19 4.0 2 0 0 0 0Tendipes pupa----------------------------- 23.5 20 10.0 11 4.7 2 0 0Tendipes adult----------------------.. ----- -20.6 28 8.0 4 2.3 1 0 0Prodiamesa-------------------------------.-.. 0.4 1 0 0 0 0 0 0Procladius-----.---------------------------1.3 4 0 0 0 0 0 0Hymenoptera and Coleoptera----------------- 1. 7 8 1.0 2 0 0 7.1 13Gastropoda. . ..-------------------------------- 2.1 5 0 0 0 0 0 0Pisidium ---------------------------------- 0.8 3 0 0 0 0 0 0Trout eggs .. . ..-------------------------------- 0.4 4 0 0 0 0 0 0Trout .. . . ..------------------------------------ 0.4 1 0 0 2.3 4 3.6 1

Number of stomachs empty------------------- 30 16 11 0

TABLE 18.-Stomach content of 298 cutthroat trout captured by gill net8 during July and Augu8t1958, by length groups

[P=percent of stomachs containing organisms; M=mean number of organisms per stomach, to nearest 1.0]

Trout size range

Food organisms 150-200 205-250 255-275 280-300 305-325 330-350 355-400(41 fish) (66 fish) (30 fish) (19 fish) (37 fish) (45 fish) (60 fish)

P M P M P M P M P M P M P M

Daphnia.... . ..------------------------ 43. 9 381 42. 4 477 33. 3 349 52. 6 749 24. 3 343 24. 4 267 25. 0 189Diaptomus---------.... -.-------------- 12.2 215 7.6 273 0 0 0 0 0 0 2.2 200 1.7 80Gammarus.-----------------------36.6 13 39.4 24 36.7 11 57.9 32 40.5 24 44.4 26 51.7 30Hyallela-------------------------7.3 6 0 0 0 0 0 0 2.7 15 2.2 65 0 0Hydracarina---------------------- 0 0 3.0 10 0 0 5.3 1 5.4 4 0 0 3.3 3Plecoptera.. ...----------------------- 2.4 1 1.5 1 0 0 0 0 2.7 1 0 0 0 0Ephemerella---------- ------------ 9.8 2 10.6 2 6.6 16 5.3 2 2.7 1 4.4 33 3.3 48Trichoptera, . . ..----------------------0 0 4.5 2 1 75 5.3 1 13.5 7 4.4 5 1.7 24Tendipes larva.-----------------------4.9 3 4.5 15 3.3 49 5.3 3 0 0 2.2 3 6.7 25Tendipes pupa. .. ..-------------------- 17.1 14 9.0 15 16.6 26 21.0 5 8.1 15 24.4 17 20.0 32Tendipes adult--------------------7.3 24 10.6 17 20.0 42 0 0 5.4 29. 15.6 5 8.3 54Prodiamesa-----------------------2.4 125 0 0 0 0 0 0 0 0 0 0 0 0Procladius.-..------------------------0 0 0 0 0 0 5.3 3 0 0 2.2 8 1.7 2Hymrenoptera and Coleoptera--------- 0 0 1.5 2 3.3 20 0 0 5.4 5 2.2 2 1.7 2Gastropoda.----------------------- 0 0 1.5 7 0 0 0 0 0 0 2.2 7 1.7 2Pisidium.---------... -.---------------- 0 0 0 0 0 0 0 0 0 0 0 0 3.3 3Trout ......--------------------------- 0 0 0 0 0 0 0 0 2.7 1 0 0 1.7 1

Number of stomachs empty-----.. 8 5 4 2 8 6 17

24

pupae in Blue Lake, due to a scarcity ofother food organisms. He also found thatplankton crustacea were used more com-

monly than Garmmarus and immaturechironomids in a more productive lake.Some workers have mentioned the pisciv-

orous nature of cutthroat trout (Echo,

1956; McConnell, et al., 1957) when largepopulations of forage fishes are present.

Irving (1956) found mostly Gammarusand Tendipes, but few fish, in cutthroattrout from Henrys Lake, in spite of thelarge number of forage species available.In general, cutthroat trout food studieshave shown a preference for macrozoo-plankters and bottom organisms over fish,except where unusually large cutthroatoccur.

TABLE 19.-Stomach contents of 344 cutthroattrout caught by angling in the vicinity ofFishing Bridge and West Thumb docks fromJune 5 to August 15 in 1957 and 1958

[P=percent of stomachs containing organisms; M =mean numberof organisms per stomach, to nearest 1.0]

Fishing Bridge West Thumb(169 fish) (175 fish)

Food organism

P M P M

Gordius--------------------2.4 4 0 0Daphnia_------------------_11.2 171 8.6 128Diaptomnue-----------------_10. 7 1,213 16. 6 714Gammarue lacuetrie---------- 18.9 12 33.7 21Hyallela azteca--------------- 0. 6 145 0 0Plecoptera------------------_8.9 7 2.3 3Ephemeroptera-------------14.2 14 12.0 34Odonata-------------------__ 0 0 0.6 1Hemiptera-----------------0 0 1.1 3Trichoptera-___--- ....----- 10.7 6 3.4 8Hymenoptera andColeoptera. 4.1 8 16.0 10Tendipe, larva......... ----- 6.5 7 4.6 6Tendipe, pupa--------------20.7 30 37.7 22Tendipes adult.-------------5.9 10 22.9 31Procladiu,.....-------------1.8 16 0 0Pieidium------------------- 1.8 2 0 0Cutthroat trout and --- 11.2 8 0 0

Number of stomachs empty- 38 15

TROUT DENSITY AND LIMNOLOGY

Angling pressure on Yellowstone Lakeis concentrated in the northern area and,to a lesser extent, in West Thumb, owingto the lack of access in the southern sec-tions. The total catch by area from 1950to 1959 showed that an average of 66.7 per-cent of the fish were removed from thenorthern area, an average of 24.8 percentfrom West Thumb, and an average of 8.5percent from the southern area (table 20).The northern area occupies 25.4 percentof the lake area, West Thumb 19.1 percent,and the southern area 55.5 percent.

Three possible effects of this unequalharvesting of trout in the northern areawere (1) fewer trout in relation to foodabundance, (2) large numbers of bottomorganisms owing to lack of predation, and(3) movements of trout into the area.

First, gill-netting in different sectionsof the lake showed fewer trout off LakeArea than would be expected from the hab-itat and the large amount of food (table21). All gill-netting was carried out afterthe major spawning runs had stopped.

The largest number were caught in theSouth Arm and around Frank Island.The scarcity of trout off Clear Creek wasdue to the exposed wind-swept nature ofthe shoreline. The scarcity of trout inSoutheast Arm is believed to be due to thelow food production and the fact that gill-netting was on the delta of the Yellow-stone River, which cutthroat do not fre-quent because of the shifting bottom.

TABLE 20.-Percentage of trout caught in each ofthree areas of Yellowstone Lake, by years,1950 to 1959

Percent caught in-

Year NumberNorthern West Southern caught

area Thumb areaarea

1950._....--.. -69.4 24.6 6.0 200,0151951-::::-:--: ;69.3 24.3 6.4 208,2551952_--:::::---68.7 23.4 7.9 245,2771953:--::::---- :66.6 23.7 9.6 195,8731954_-----------69.1 22.0 8.9 215,9331955_-----------66.9 25.1 8.0 286,0561956_-----------64.0 25.6 10.4 290,2211957-:::::-:--63.4 26.9 9.7 301,1551958_-----------64.7 25.3 10.0 349,0271959_-6_ _ _ _ 64.6 27.1 8.3 393,467

Mean_. 66.7 24.8 8.5- -

25

TABLE 21.-Number of trout of more than 200millimeters, total length, captured in depthsof 0 to 20 meters in six areas of Yellowstone

Lake by 38 overnight experimental gill-net setsin 1958

Num- Num- MeanSampling area Date of set ber of ber of catch

sets trout per setcaught

Lake..--------..---July 25-Aug. 6 66 11.018.

Middle South Arm Aug. 13._.... 3 47 15.6Peale Island -::::July15-24 14 219 15.Southeast Arm - ___July 31____ 3 29 9. 6Clear Creek_----::Aug.:19 3 20 6. 6Frank Island and Aug. 8-13- 9 125 13.9

Plover Point.

Second, bottom organisms in thenorthern area were more numerous thanwould normally be expected from thebottom types or abundance of aquaticplants (table 15). The number of organ-isms above 15 meters at Lake Areaaveraged 288.8, whereas the nearest re-corded number in other secti ins of the lakewas 143.2 at Frank Island. The greaterabundance of bottom organisms in thenorthern area was due to more Gammarusand Hyallela, the principal foods of thecutthroat trout. The most plausible reasonfor the large number of bottom organismsat Lake Area is the lack of trout predationon bottom organisms due to rapid recruit-ment by angling. Both Ball and Hayne(1952) and Reimers (1958) demonstratedthat fish populations can severely depletebottom fauna populations. Wohlschlag(1950) found that bluegills fed moreheavily in areas of heavy chironomid pro-duction than in areas of low production.

Third, trout apparently moved into thenorthern area. This movement was be-lieved to be for feeding or to take ad-vantage of the high standing crop ofbottom food, since most movement oc-curred after the spawning period. From1949 to 1955, 18,836 trout were tagged infive spawning streams, and the returnedtags that included suffcient informationon catch location were used to compare thegeneral movements of postspawning troutfrom five spawning streams (table 22),

(Ball and Cope 1961). The data on fishmovement can be summarized as follows:Those fish tagged in Pelican Creek wereusually recovered in the northern area andaround Fishing Bridge. Clear Creek fishalso were captured in the northern area,particularly in Bridge Bay. Fish taggedin Chipmunk and Grouse Creeks, at thelower end of South Arm, were most com-monly captured in the southern area orin West Thumb, although 25 percent werecaptured in the northern area. There wasa movement of postspawners from Chip-munk and Grouse into West Thumb and,to a lesser extent, into the northern areain August, and many were captured inthese locations, during the year followingtagging. From the movements of post-spawners, the only evidence of a long-distance movement from the spawningstream to the area of capture was the largenumber of fish tagged in South Arm thatmoved into West Thumb and into thenorthern area. A lesser movement wasapparent from those fish tagged in ArnicaCreek and recovered on the west shore ofthe northern area of the lake. In generalthe postspawners recovered the secondyear after tagging dispersed more thanthose caught the first year.

TABLE 22.-Movements of cutthroat trout afterspawning, as determined from fish tagged inive spawning streams and recaptured by an-gling, 1949-55

Percent of all returnsNum- Num captured in-ber of ber of _________

Spawning stream fish tagtagged returns North- South- West

em en Thumbarea1 area area

Arnica Creek.-------- 4,948 271 26.2 4.4 69.3Pelican Creek.------- 6, 043 422 88. 9 4. 5 6. 6Clear Creek.--------1,100 54 70.3 12.9 16.7Chipmunk and

Grouse Creeks--- 6,745 160 25.0 41.9 33.1

Total---- 18,836 907--------.------------

I Includes 18 returns from Yellowstone River.

Heavy fishing pressure undoubtedly in-fluenced the number of tag returns fromthe northern area. The estimated annual

26

fishing pressures, in hours per acre, from

1950 to 1954 were northern 10.5, West

Thumb 4.9, and southern 0.6. The fishingmortality rates (percent) for postspawn-ing trout from five spawning streams were

as follows: Pelican, 12.2; Arnica, 9.3;Chipmunk, 5.2; Grouse, 3.7; and Clear,9.4 (Ball and Cope 1961). These fishingmortality rates show that fish from Peli-

can, Arnica, and Clear Creeks are sub-

jected to a greater fishing pressure thanfish from Chipmunk and Grouse, but theratios are not so different as the fishing

pressure per acre for the three areas of thelake; thus, there must have been a greatermovement of trout into the northern area

or to West Thumb than away from it.From the location of tag recoveries,

there appeared to be a tendency for post-

spawning trout to follow the shoreline ofgreater standing crops of food organisms

from their spawning streams to their point

of capture, although such was not always

true. It was particularly true, however,

for fish from Chipmunk, Grouse, and

Arnica Creek. These data support the hy-

pothesis that feeding may be an important

factor in causing trout to move out afterspawning.

There was a greater concentration of

planktonic entomostraca in the north-

east part of the lake due to surface cur-

rents, but the food of postspawning trout

is principally bottom organisms, and a

large standing crop of bottom foods

would be more important than plankton

in causing any fish to migrate.

BIOLOGY OF YELLOWSTONE LAKE

Yellowstone Lake has many character-istics of the large oligotrophic lakes ofCanada or of the northern Great Lakes,but its bottom fauna and fish composi-

tions are notably different. The otherlakes have Pontoporeia or Mysis as thedominant bottom fish-food organism, andall have large populations of coregonids.Undoubtedly, factors which have pre-vented introduction of these organismsinto Yellowstone Lake include the impass-able falls 15 miles below the lake outletand the altitude.

An interesting comparison between themean depths of the large lakes of Canadaand the northern Great Lakes and the an-nual commercial fish production (lbs. peracre) has been prepared by Rawson(1955). He constructed a curve and foundthat fish production decreased with in-creasing depth on a relatively smoothcurve. A comparison of the mean depthof Yellowstone Lake (139 ft.) and itsmean sport-fish production from 1950 to1959 (2.15 lbs. per acre) shows that it fits

into this curve closely between Lake

Nipigon (1.07 lbs. per acre, and mean

depth 180 ft.) and Lake Winnipeg (2.66lbs. per acre, and mean depth 43 ft.). Itis surprising that the sport-fishery produc-tion of Yellowstone Lake with only one

fish species fits so well into this curve when

the commercial fish production of these

lakes involves many fish species and sev-

eral fish predator-and-prey relations.The limnological classification of Yel-

lowstone Lake according to Lundbeck(1934) would be primary oligotrophic,since it is poor in nutrients and has low

temperatures. The volcanic nature of the

drainage, with deficiencies in calcium andother minerals, probably has as great aninfluence in limiting production as has

morphometry. Turbidity and too greata water exchange are not limiting factorsin Yellowstone as mentioned for Port

John Lake, British Columbia (Robertson,1954), which has a similar water chem-istry but a high rate of water replacement.The low number of plankters per liter in

27

Yellowstone Lake is partly offset by thedepth of its trophogenic zone. Ohle(1956) stated that deep lakes may have alower production density, but this defi-ciency is compensated for by a greaterproduction depth than shallow lakes. Thegreat production depth of YellowstoneLake is shown from the depth distribution

of aquatic plants, bottom fauna, andplankton. Secchi disk records, whichreflect plankton density, showed highreadings.

The development and use of YellowstoneLake is controlled by the National ParkService. This control has prevented arti-

ficial eutrophication as has occurred inseveral large oligotrophic lakes (Edmund-son et al., 1956). The data collected byForbes (1893) in 1890 were not quantita-tive, but a comparison of his observationswith the data in this report indicates thatthe dominant species composition of zoo-plankters, phytoplankters, and bottom or-ganisms did not change from 1890 to 1957.

Few large lakes have as few fish speciesas Yellowstone, but it appears that the cut-throat are utilizing the available animalfood rather efficiently. The depth range ofthe trout is closely related to the depth dis-tribution of both the predominant bottomfoods and planktonic foods. The kinds offood utilized by different sizes of troutoverlap to a great degree, although thereis a gradual transition from a bottom

fauna-zooplankton diet to a predomi-

nantly bottom-fauna diet in the range of

275 to 325 mm. (table 18). This change infeeding habits occurs in the same lengthrange when trout first become available

to the sport fishery in numbers. A length

frequency curve of the catch for 1959

shows that the slope begins to increasearound 275 mm., but that the greatest in-

crease takes place above 315 mm. (fig. 8).The reason the catch does not include more

small trout (below 12 inches) is not thatthey are caught and returned to the lake,

500

450

400

350-

} 300-

250 -

E 200 .Z

150

100

60

0215 240 265 290 315 340 365 390 415 440

Length in millimeters

FIGURE 8.-Length frequency of anglers' catchfrom Yellowstone Lake in.1959 from sample of1,690 fish. Points represent medians of 25-mm.groups.

since many anglers will keep trout around10 inches. These trout are difficult tocatch ' and are dispersed more in the lake

owing to their feeding habits. Small troutfeed both in the limnetic and littoral zone,while large trout feed in the littoral zone.The greater dispersal of small trout makesthem less vulnerable to angling. Another

probable effect of this great dispersal is

the low rate of predation on small trout

by large trout as shown by food studies.

This fact also accounts for the high sur-

vival rate of 36 percent which Ball and

Cope (1961) suggest exists from the timethat immature fish leave the parent stream

until they return as spawners.

The only competitive species appears tobe the longnose sucker, since recent studies

(unpublished) have shown that suckers

feed primarily on the same bottom organ-

isms as the cutthroat trout. Past data on

1 Madsen in an unpublished report (Age and growthof the cutthroat trout (Salmo lewisi) in YellowstoneLake, wyoming, dated May 15, 1940) attempted todetermine why anglers rarely caught small trout andfound that small trout would rarely take any lure,even when schools were located.

a I a I a I I I I

28

the sucker population in Yellowstone Lakeare lacking, although records from theYellowstone Fish Cultural Station in-dicate that -the sucker was introduced in1923 or 1924. Numbers of suckers re-corded in the spawning runs in Pelican

Creek showed a general increase up to1950 and a leveling off since that year.The competition with the cutthroat troutappears to be increasing, although therehas been no clear evidence of detrimentalinfluence on the trout population.

SUMMARY

Limnological studies on YellowstoneLake, Yellowstone National Park, wereconducted from 1954 to 1959. Geologicalevidence indicates that the original basinwas formed from,a subsidence or readjust-

ment of the laval flows in the Eocene.

Hot springs still exist in the drainagebasin and in the lake.. Annual. water-levelfluctuation is less than 1.8 meters. Thelake lies at an altitude of 2,358 metersand has the following dimensions: Surfacearea, 35,391 hectares; mean depth, 42meters; basin capacity, 14 x 109 cubicmeters; maximum depth, 95 meters; and

shoreline development, 3.04. A contour

map is included.Water-current studies showed a large

surface-water movement from the southand southwest to the north and northeast

parts of the lake. Compensatory subsur-face currents were found by bottom-cur-

rent studies. Water-temperature datashowed various stages of stratificationfrom late May and early June when theice left until late July when complete

stratification was evident. Differences inwater stratification between West Thumb

and the northeast part of the lake were re-lated to surface-water movement. Highwater levels in certain years were associ-ated with deep epilimnion layers.

Water composition showed HCO3 to bethe major anion and Na to be the majorcation. Conductivities were highest inWest Thumb and lowest in SoutheastArm. Upwelling is believed to have

caused the high readings in West Thumb.Protected stations had lower conductivi-ties than exposed stations, and the causa-tive factor was believed to be the thinnerepilimnion strata in the protected stationswhich caused a more rapid utilization ofnutrients by plankton. Oxygen concen-trations were usually above or near satu-

ration, although deficits developed in thehypolimnion during 1957 and 1959. Freecarbon dioxide was present in all samplesand concentrations above 10 p.p.m. were

found below the metalimnion.

Bottom types included boulders, rubble,black obsidian sand, and fine clays withorganic matter. Amount of organic mat-

ter in the soft sediments increased withdepth, but lake areas with strong currents

had low amounts of organic matter.Greatest concentrations of soil nutrientswere in deep water. A list of aquaticplants and their depth ranges is presented.The depth limit of all higher aquaticplants was 18 meters.

The diatoms Asterionella, Melosira, andStephanodiswe were abundant. A dense

pulse of A n a b a e n a was observed inAugust. Principal zooplankters were

Conochihs unicornis, Diaptomus sho-shone, and Daphnia shoedleri; largestconcentrations ranged from 5 to 18 meters.

Several large swarms of Daphnia shoed-elri, an inshore swarming species, were

observed in 1959. Benthos consisted prin-

cipally of Gam/marus lacustris, Hyallelaazteca, oligochaetes, and tendipedids. Ex-

29

cept for tendipedids, which were presentat all depths, bottom organisms were rare

below 23 meters.Cutthroat trout were concentrated in the

upper 15 meters of water and were rare

below 25 meters. Most abundant food or-

ganisms in trout stomachs in the summerseason were Gammarus lacustris, Daph-

nia shoedleri, and tendipedids. Gam-marus were important in June and July,

and Daphnia in August and September.Small trout utilized both bottom organ-isms and zooplankton, while large troutfed almost entirely on bottom organisms.

Angling pressure and catch were con-

centrated in the northern area and threeeffects of this unequal harvesting were (1)fewer trout in relation to food abundance,(2) large numbers of bottom organismsowing to lack of predation, and (3) move-ments of trout into the area.

Yellowstone Lake is oligotrophic andhas a deep productive depth. The domi-nant species composition of plankton andbottom organisms has not changed from1890 to the present. Low availability ofsmall trout to anglers is caused by feedinghabits and great dispersal; this serves toprevent overexploitation of small trout.

LITERATURE CITED

AYERS, JOHN C., DAVID C. CHANDLER, GEORGE H.LAUFF, CHARLES F. POWERS, and E. BENETTE

HENSON.

1958. Currents and water masses in LakeMichigan. Great Lakes Research In-stitute, University of Michigan, Pub-lication No. 3. 169 pp.

BALL, ORVILLE P.

1955. Some aspects of homing in cutthroattrout. Utah Academy of Sciences,Arts, and Letters, Proceedings, vol.32, pp. 75-80.

BALL, ROBERT C., and DON W. HAYNE.

1952. Effects of the removal of the fish pop-ulation on the fishfood organisms ofa lake. Ecology, vol. 33, No. 1, pp.41-48.

BALL, ORVILLE P., and OLIVER B. COPE.

1961. Mortality studies on cutthroat trout inYellowstone Lake. U.S. Fish andWildlife Service, Research Report55.

BAUER, C. MAX.

1955. Yellowstone, its underworld. Univer-sity of New Mexico Press, Albuquer-que, N. Mex. 118 pp.

CALHOUN, A. J.1944a. The xottom fauna of Blue Lake, Cali-

fornia. California Fish and Game,vol. 30, No. 2, pp. 86-94.

1944b. The .food of the black-spotted trout(Salmo clarkii henshawi) in two Si-erra Nevada lakes. California Fishand Game, vol. 30, No. 2, pp. 80-85.

CARRUTHERS, J. N.

1958a. A leaning-tube c u r r e n t indicator"Pisa." Institute of Oceanography,Monaco, Bulletin No. 1126. 34 pp.

1958b. Seine net fishermen can easily observebottom currents themselves. TheFishing News, London, July 25,1958, pp. 6-7.

COPE, OLIVER B.1956. Some migration patterns in cutthroat

trout. Utah Academy of Sciences,Arts, and Letters, Proceedings, vol.33, pp. 113-118.

1957. The choice of spawning sites by cut-throat trout. Utah Academy of Sci-ences, Arts, and Letters, Proceedings,vol. 34, pp. 73-79.

CHURCH, PHIL E.

1945. The annual temperature cycle of LakeMichigan. II. Spring warming andsummer stationary periods, 1942.University of Chicago, Departmentof Meteorology, Miscellaneous Re-port 18. 100 pp.

ECHO, JOHN B.

1956. Some ecological relationships betweenyellow perch and cutthroat trout inThompson Lake, Montana. AmericanFisheries Society, Transactions, vol.84, pp. 239-249.

EDMONDSON, W. T., G. C. ANDERSON, and DONALD

R. PETERSON.

1956. Artificial eutrophication of Lake Wash-ington. Limnology and Oceanogra-phy, vol. 1, No. 1, pp. 47-53.

30

FORBES, S. A.1893. A preliminary report on aquatic inver-

tebrate fauna of the Yellowstone Na-tional Park, Wyoming, and the flat-head region of Montana. U.S. FishCommission, Bulletin for 1891, vol.11, pp. 207-256.

HUTCHINsON, G. EVELYN.

1957. A treatise on limnology. Vol. 1, Geog-raphy, Physics, and Chemistry. JohnWiley & Sons, New York. 1,015 pp.

IRVING, ROBERT B.

1956. Ecology of the cutthroat trout inHenrys Lake, Idaho. American Fish-eries Society Transactions, vol. 84,pp. 275-296.

JOHNSON, JAMES H.1958. Surface-current studies of Saginaw

Bay and Lake Huron. U.S. Fish andWildlife Service, Special ScientificReport-Fisheries, No. 267. 84 pp.

LAAKSO, MARTIN and OLIVER B. CoPE.1956. Age determination in the Yellowstone

cutthroat trout by the scale method.Journal of Wildlife Management, vol.2, No. 2, pp. 138-153.

LUNDBECK, JOHANNES.

1934. Uber den "Primar Oligotrophen" See-types and Wollingster See als dessenmitleleuro paichen vertreter. Archivfor Hydrobiologie, vol. 27, No. 2, pp.221-250.

MCCONNELL, WILLIAM J., WILLIAM J. CLARK, and

WILLIAM F. SIGLER.

1957. Bear Lake, its fish and fishing. Utah-State Department of Fish and Game,Idaho Department of Fish and Game,Wildlife Management Department ofUtah State Agricultural College, 76pp.

MCMAHON, V. H.1954. Abundance and distribution of entomo-

stracan plankton at Lakelse Lake,B. C., 1949-1952. Fisheries ResearchBoard of Canada, Journal, vol. 11,No. 4, pp. 479-499.

MILLER, F. GRAHAM.1952. Surface temperatures of the Great

Lakes. Fisheries Research Board ofCanada, Journal, vol. 9, No. 7, pp.325-376.

MOORE, H. L., O. B. COPE, and R. E. BECKWITH.1952. Yellowstone Lake trout creel censuses,

1950-1951. U.S. Fish and WildlifeService, Special Scientific Report-'-Fisheries, No. 81. 41 pp.

MORTIMER, C. H.1952. Water movements in lakes during sum-

mer stratifications : evidence fromthe distribution of temperature inWindermere. Royal Society of Lon-don, Philosophical Transactions,Series B, Biological, vol. 236, pp.355-404.

OHLE, W.

1955. Ionen austausch der Gewassersedi-mente. Memorie Istituto ItalianoIdrobiol. de Marchi, Suppli, vol. 8,pp. 221-248.

1956. Bioactivity, production, and energy uti-lization of lakes. Limnology andOceanography, vol. 1, No. 3, pp. 139-149.

PENNAK, ROBERT W.1955. Comparative limnology of eight Colo-

rado mountain lakes. University ofColorado Studies, Series in Biology,vol. 2, p. 75.

1957. Species composition of limnetic zoo-plankton communities. Limnologyand Oceanography, vol. 2, No. 3, pp.222-232.

RAwsoN, D. S.1953. The bottom of Great Slave Lake. Fish-

eries Research Board of Canada,Journal, vol. 10, No. 8, pp. 486-520.

1955. Morphometry as a dominant factor inthe productivity of large lakes. In-ternational Association of Theoreti-cal and Applied Limnology, Proceed-ings, vol. 12, pp. 164-175.

REIMERS, NORMAN.1958. Conditions of existence, growth, and

longevity of brook trout in a small,high-altitude lake of the eastern Si-erra Nevada. California Fish andGame, vol. 44, No. 4, pp. 319-333.

REIMERS, NORMAN, JOHN A. MACIOLEK, and ED-WIN P. PISTER.

1955. Limnological study of the lakes in Con-vict Creek Basin. Mono County,California. U.S. Fish and WildlifeService, Fishery Bulletin, No. 103,vol. 56, pp. 437-503.

ROBERTSON, J. G.1954. The trophic status of Port John Lake,

British Columbia. Fisheries Re-search Board of Canada, Journal,vol. 11, No. 5, pp. 624-651.

RODHE, W.

1949. The ionic composition of lake waters.Verh. Int. Ver. Limnol., vol. 10, pp.377-386.

31

ROELOFs, EUGENE W.

1944. Water soils in relation to lake produc-tivity. Michigan State College, Agri-cultural Experiment Station, Techni-cal Bulletin 190. 31 pp.

THIENEMANN, A.

1928. Der Sauerstoff im eutrophen und oligo-trophen Seen. Die Binnegewasser,4. Stuttgart, Schweizerbartsche Ver-lagsbuchhandlung. 175 pp.

ToNoLLI, VITTORIO.

1954. Stabilita E Produttivita del LimnobioAlpino. Memorie Istituto ItalianoIdrobiol., vol. 8, pp. 29-70.

U. S. GEOLoGICAL SURVEY.1952. Surface water supply of the United

States, Part 6-A. Missouri RiverBasin above Sioux City, Iowa. U.S.Geological Survey, Water SupplyPaper No. 1239. 450 pp.

1953. Surface water supply of the UnitedStates, Part 6-A. Missouri RiverBasin above Sioux City, Iowa. U.S.Geological Survey, Water SupplyPaper No. 1279. 458 pp.

1954. Surface water supply of the UnitedStates, Part 6-A. Missouri RiverBasin above Sioux City, Iowa. U.S.

Geological Survey, Water SupplyPaper No. 1339. 381 pp.

1955. Surface water supply of the UnitedStates, Part 6-A. Missouri RiverBasin above Sioux City, Iowa. U.S.Geological Survey, Water SupplyPaper No. 1389. 423 pp.

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of water, sewage, and industrialwastes, 1955. Tenth edition. 522 pp.

WARD, JAMES.1955. A description of a new zooplankton

counter. Quarterly Journal of Micro-scopical Science, vol. 96, No. 3, pp.371-373.

WELCH, PAUL S.1948. Limnological Methods. Blakiston Co.,

Philadelphia. 381 pp.WIsLER, C. 0. and E. F. BRATER.

1949. Hydrology. John Wiley & Sons, NewYork. 419 pp.

WOHLSCHLAG, DONALD E.

1950. Vegetation and invertebrate life in amarl lake. Investigations of IndianaLakes and Streams, vol. 3, No. 9, pp.321-372.

32

DRIFT BOTTLE RELEASESAND RECOVERIES

C4,l0Seeding Release date Number Number A4,15

line 1957 released recovered G7, IIA16,15A15,16

A July 15 25 12 C4,4 K I G7, 17C July 15 10 10 C3,5 C2,31E Aug. 16 29 13F July 9 13 7.,6 5,10(2)G Aug. 16 22 16 C3,10 G6,324H Aug. 23 51 7 C6,753 G9,12I July 10 II 9 G6,16 G10,12

J July 10 18 4 05,6 H5,301E8,3 H 1,327K July 9 8 6 E,6 11,29

L July 24 18 3 E6,4 3,6 G53,6 16,3

Total 205 87 EI G2,31Ci,17 A14,16

A4,5 C5,23EI1,3 C5,24

A14,16

CII7 E 12,336A3,46 E5,5 K 2,9

A5,1 L 5,7E 2,5 GI,392 H 4,331

K2,431 L 2,7E I,3 43 A5S,1 L 5,750

E 12,2 4 F8,400 4 H15,3014 K 3,14

9 ~E 10,3 F F5,38 F5,346 J 1,675

E 9,I5 F7,339 G8,7 60

E9,383 A8,31 HI,352Ai, 7F3,341 1 8,376

F 4,3 E 12,702

E13 18 F1,342A1, 5 A3,7

K K3,I0KI,

J 10,4N

YELLOWSTONE LAKE149,5

WYOMING

MILES SYMBOLSI,9

0 e 4 , ,..t ..- seeding line0 I 2 3 4 6 A3,7(2) - recovery

KILOMETERS A- seeding line 43- point on seeding line

where bottle released 16,97- number of days

before recovery(2)-two bottles recovered

APPENDIX A.-Points of release and recovery of drift bottles in Yellowstone Lake, Wyoming.

Seedingline

BDMN0P

0

33

DRIFT BOTTLE RELEASESAND RECOVERIES

B5,8 M17,4Release date Number Number B13,7 83,7 M15,5

released recovered P1,4,2 87,8 M5,5(2)M 2 P3,14

Aug 6 1957 35 13 D0,5 810 8 89,8(2)Aug 6 1958 15 4 811'2Aug 9 1957 37 17Aug 6 1958 20 5Aug 6l958 8 0Aug 6 1957 20 13 M8,4

Total 135 52 DII,7 M5,542)P3,31M9,4(2)815,3 M10, 4(2)P4,3 4M11,14(2)

M6,4P6,7

D7, 17 20 P6,D4,7 P6,7

82,9 N 4,7 P4,7013,7

B6,2 1P2,12t.o, a c P2,12

85,10

N

YELLOWSTONE LAKEWYOMING

MILES SYMBOLSI 3 4 ,".4 8 seeding line

KIL METERS B6,3(2)-recoveryB- seeding line6- point on seeding line

where bottle released3 - number of days before

recovery(2)-two bottles recovered

APPENDIX B.-Points of release and recovery of drift bottles in Yellowstone Lake, Wyoming.

U. S. GOVERNMENT PRINTING OFFICE : 1962 0 -595956

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