A FISHT ,Y W1.NAGE!4ENT SURVEY OF AMERICAN FALLS RESERVOIR
IDAHO DaARTMFET OF FISH MID GAME
November, 1 9 4 9 Page
1
TABLE Or CONTENTS INTRODUCTION
History, Location, Administration m:1nstigation of Survey ...... 1 Recreational Development ...... 2 Time of Survey, Personnel ...... 3
PHYSICAL CHARACTERS 4
Drainage of the Reservoir ...... 5 Inlets ...... 5 Outlet ...... 10 Fluctuation and Its Significance ...... 11
CHE ICAL CHARACTERISTICS AND TE:ta i.1J TUBE 12
Oxygen, Alkalinity, pH ...... 13 Water Temperature ...... 13 Pollution ...... 14
B3I.LOGICAL CHARACTERS 15
Vegetation ...... 15 Fish Foods ...... 16 Fishes ...... 18 Relationship of the Species to Each Other and Their Environment ...... 19 Fish Plantings ...... 21 Predators ...... 22
COMMERCIAL FISHERY RECOM
THE INDIAN FISHERY MENDA
CONCLUSIONS TIONS
MANAGEMENT PROPOSALS AND DISCUSSION M a p of Drainage Area, Fig. 1 22 Map of Reservoir, Fig. 2 Plates 1-4 23
24 25 3 0
31 32 33,4 A FISHERY 2;ANAGI:=IT SURVEY OF AP .ICAi: FALLS RESERVOIR
Forrest R. Hauck Idaho Fish and Game Department
INTRODUCTION
History, Location, Administration, and Instigation of Survey
Prior to the construction of the dam at American Falls which formed the American Falls Reservoir, the area now covered by reservoir waters was a river "bottom" land, Much of it was under cultivation for the production of "wild" hay; some was used as pasture. This area of slightly over 55,000 acres was liberally cut up by meandering streams and sloughs. A number of springs had their origin in the "bottom" and there were numerous islands. From the accounts of people who were famil- iar with the bottom, it abounded with fish and wildlife and much recrea- tional use was made of the area.
Upon completion of the dam in 1927, this large area was inun- dated and much of its original recreational value was lost. Waterfowl shooting still is carried on along its periphery. There was promise of a good sports fishery at the outset but this has shown a gradual decline in the 22 year history of the water.
Located in parts of Bingham, Bannock and Power Counties in southeastern Idaho, American Falls Reservoir is principally an irrigation project. Its waters are administered by the Minidoka Project of the
U.S. Bureau of Reclamation and are used in Minidoka, Cassia, Twin Falls,
Jerome, Gooding and Lincoln Counties downriver, where thousands of acres of cultivated land are made productive by this use. The fish and wild— life living in and on the reservoir are administered by the State of
Idaho. In addition to these five agencies a sixth, also, is concerned.
About one—third of the area covered by reservoir waters was a part of the Fort Hall Indian Reservation and approximately one—third of the periph- ery area is reservation land and, along with tributary waters thereon,
is administered by the Bannock—Shoshone Indian Tribe and Agency. It is
understood that the Bureau of Reclamation holds flowage rights only on
the reservation lands up to elevation 4355.
It was suggested by sportsmen's organizations of Power, Bingham
and Bannock counties that a fishery survey of the reservoir be made to
determine (1) the reason for the decline of the sports fishery, (2) manage-
ment projects which might improve this fishery. This survey was begun in
the spring of 1948 and carried through the fall of 1949. It was carried
on as a management survey, not a biological fishery survey, and for that
reason only data pertinent to its fishery management is concerned and
covered by this report,
Recreational Development
Recreational development of American Falls Reservoir's sport fishery has been very slow. Winter fishing for perch, through the ice, is the major phase of the sport fishery and its popularity has increased gradually through the last 15 years. Areas of the reservoir in the vicin- ities of American Falls, Aberdeen, Sterling, Springfield, and near the mouth of the Portneuf are all popular with the ice fishermen. The only factor limiting this sport is the weather. During the extreme, prolonged cold period in January and February, 1949, for example, very little perch fishing was done. Perch fishing is almost entirely confined to winter fishing since, for some unexplained reason, the perch in the reservoir do not take bait readily during the summer months.
The sport fishery for trout is confined almost entirely to shore fishing. A sm » amount of trolling is done but here again, the weather is a limiting factor. Wave action on the reservoir is usually moderate to severe and several lives have been lost from boating accidents during wind storms. Areas where most trolling is done are near the dam and on the backwaters near the mouths of the Portneuf River and Spring Creek. Shore fishing for trout is popular in the Aberdeen area and near Spring-
field (near mouths of Danielsen and Boom Creeks) in the spring and fall.
Other shore fishing is done in the backwaters along the Portneuf. The lack of fishing success is probably a limiting factor to
trolling for trout, and this in turn is due to a comparatively small trout
population. Better fishing success is encountered in nearby fishing waters
such as Snake River both above and below the reservoir, Springfield Lake, and the various streams on the reservation. Other scattered sport fishing
is confined largely to family groups near their places of residence.
There are no recreational facilities on the reservoir which have
been developed for fishing alone. There are two municipal boat dock:,
one at Aberdeen, one at Spring Hollow near American Falls. These have
been built to launch boats, there being no boat rentals at either. Boat
regattas are annual events from each of the docks, Facilities for camping
are non-existent. It is difficult to launch a boat anywhere on the reser-
voir except from the above docks, a landing in Bill Smith Bay, and develop-
ments of commercial fishermen near Sterling, Springfield, and on the Portneuf
side, except during the spring months when the reservoir is full,
There is probably less sport fishing on the entire reservoir
during a year's time than in the five miles of river below the dam during
the season of May 21 to September 25. Thus the importance of the reservoir
as a public fishing water cannot be rated very high. As has been pointed
out, however, this is not the fault of the sports fishermen. Limitations
of weather in both summer and winter help keep its value low.
Time of Survey, Personnel The survey covered by this report was started in May, 1948 and continued through August, 1949. A total of seven stations were set up on the reservoir and pertinent data collected at each. Approximately one week to ten days was spent at each station collecting data. About twice that time was spent in laboratory work analyzing and tabulating the data re: ...eh tieh. whe seen, c-hiec-ehh ihee.rm:.tioh
frc-)h thL here of Iteclamatioh, Fort, Hal_ Ind.i.e.r. 1,-enc:-, and. ehoresme:..
Locatiee etatione and month an:: year of work follow.
• Off Bill omith Bay — May, 194 Off 3prin Hollow — %' y, 194: ano. 3ehtemoer, 194? • Off :iberdeen coat aOCh — :i,eh-tamoer 191,9 Off 3terling — May, 1949 Cff mouth 3n-Ike iver — 'y, 1949 Off mouth Coring Creek — June, 194% and ;ea:het, 1949 • 2ackehaterc ne-r Portneuf 1iiver mcuth — Au-uet, 1949
3tetiens and time for work were selected se as eive a coy: lets
picture of the reservoir during spring (hieh weter) and fall (low hlter)
both near the dam and in the backwater ::reds.
Pere:anewl consisted of the writer and Boe 2hillihe 194E,
and Leon ::dre-:h7:, durinT the August, 1949, survey.
P!LYSICAL CHAiie,CT11:3
Aelerican Falls Reservoir i3 reuechly triangular in shape with its long axis nointing southwest. The dam whice form the reservoir is on this noint. It is approximately 20 mile: lon elonL; this; axle and,at its widest part, the northern base of the isosceles trianle, it is almost 9 miles wide.
It covers, when full, an are:_ of about 87 :square miles. The shoreline alonz the western and eastern sides ie composed almost entirely of sand and lava cliffs (Bee pletes 1, 2), the former gratuelly being undermined by wave action and forming sand beeches. The short northern shoreline is flat ubottomu land, some of it marshy, the remainder with scattered trees and brush. At the dam the reservoir is 60 feet deep when f u l l . The bottom gradually slope::
=ward to the northern b.c k-.:aterz with the orieinel river beds and sloughs being: the cnly depressions in its floor.
dnoa: in the reservoir will eoun- to at least 1:7 nor cent and as high as 20 her cent of the surface hree dehendinL upon the clevetion of the water. At the northern end of the reservoir one must uc at least 0 miles from the shoreline to oo in whter dee- enough to set a
=11' net. Tei- ehoa-1 water th no—eecrr end i - comhoeee of . , eele e• :rec..- oottome hiCh tnc eend 1: dominant, comoriein es
:per cent of the shoal areas.
The sotto.:: other than in shoal area= : i v, ccn JlSt.I of .... deeo ayer ..
or rich silt covered with e thin layer of ora:o marl. The water of the reservoir is white. Its tranopare c : varies
s:itt: the season of the year and now recently wave action has occurred.
During late spring the water is colored with a rich plankton .:ro':t`;, and ,vain in lace summer months with decaying algae and other detritus.
DRAI:,1AGL )F TIE Snake River aoove the dale drains an extremely large basin
e::tending to Lontuna on the ncrth, into -,-yo:ring and _e_lo::stone Par:: on
the nertheest and all of southeastern Idaho except for the small area in
the sear River drainage (3ee figure 1). Its drainage basin of iu-
nroxialatel:: 11,000 square miles is made un of desert areas, sagebrush
plains and hi+.ls, an. timbered mountainous terrair interenersed with
. marshy meadows. Al._ of tale drainere area is of lava or lime: 1i n . fcrm_:–
tion `:a:. the is, as a consequence, hard. L,yinv within this drei.na_.e
basin are thousands of acres of cultivated and irrigated lanais.
Inlets
3ccause of the diverse character of the inlets to ;one:ican
Falls P._aservoir, they should be listed and discussed under several aections:
(a) streams and wastes sub i c ct to extreme fluctuation due to irri atior. a.nd, conseouently, not too imnortdnt in the overall fi.sncries picture,
(b) stream: or springs of regular floe out with barriers to unstro,i;s mi.- ration, and (c) streams and springs Cf more or loss regular flow, that is,
,:lt., ne extremely low eriedc of flow. These lute: arc the streams that are iyoort:nt to the fishery picture. fluctuation (with maximum and ;minimum floes in caei_ fee; per second in parentheses) are Bannock Creek (40—2) on the east side and Crystal
Ditch (3—0), Artesian Spring (5—1), :sterling Waste (11—1), Colburn
Waste (4-1), Aberdeen Waste (159—10), Tartar ''"aste (52-0), 5chiltz
Waste (3—1), Cedar Waste (65—0), Boom Creek, Alkali Creek and Triple
Creek (5—1) on the west and north side of the reservoir. Of these,
Uannock Creek probebly was used by spawning fish before its diversion
for irrigation but can no longer be considered too important as a
spawning and rearing stream.
(b) Two streams, the Crystal Waste (0—25) and Danielsen Creek
(66-73), although showing excellent flows throughout the year, contain barriers near or at their mouths. The Crystal "ante (or Sering) is a privately developed water used by a commercial hatchery. A concrete dam approximately one—quarter of a mile above its mouth marks the limit to which spawning fish can migrate. Spawning runs of trout and blueback salmon use this short section of stream which does contain suit—able . ravel beds on the riffle areas. There is pro' :bl- a small escapement of rainbow trout over the dam into the lower end of the stream and the reservoir from the commercial hatchery. Danielsen
Creek is the outlet for Springfield Lake, a body of water that furnishes excellent trout f i s h ing during the regular season and which is heavily stocked to take care of the fishing pressure requirements. The stream presents a barrier at its mouth in the form of a falls over a lava—rock cliff. The height of this falls varies with the elevation of the reservoir but at no time is less than six feet high. The reservoir at the mouth of Danielsen Creek is popular with trout fishermen and fishing success is good. It is thought, even though experiments with marked fish have never been carried on, that the majority of trout taken at this point are part of an escapement from
Springfield Lake. The fact that the falls are a barrier to upstream migration of trout from the reservoir is off-set by their also barring the
migration of undesirable species into Springfield Lake.
Table 1
Some inlets to American Falls Reservoir with significant tribu- taries and their flows in C.F,3. -From U.3.B.R. records.
Flow, C.F.S. Name High
Crystal Spring 40 25 Danielsen Creek 66 33 Snake River (Mean 7,026) 23,600 380 McTucker Spring 28 26 Pyle Spring 16 14 Tide Creek 61 54 Big Jimmy Creek 54 27 Spring Creek 496 469 Kinney Creek 31 29 Clear Creek 125 125 Ross Fork 64 50 Portneuf River 348 290 Bannock Creek 40 2
Total inflow *excl. of Snake 3,479 2,609
Total inflow 27,079 2,959
May - September, 1948
*Total inflow includes all measured flows as well as unmeasured, such as springs within the reservoir itself.
(a) The remainder of the reservoir inlets (Table 1) are important enough to be considered separately. All of them do or could support: heavy populations of game fish, heavy fishing pressure, large numbers cf spawning fish and their progeny.
1. Snake River. Aside from being the largest inlet, Snake River has numerous tributaries near enough to the reservoir to be significant in the fisheries picture. All of these tributaries are spring-fed, have fairly constant temperatures, are productive of food for fish and have good spawning areas. Among these tributaries are McTucker Spring (28-26
G.F.S.) which will serve as an example of all such tributaries of the Snake.
McTucker Spring has a constant temperature of 52o F. at its
* 4eally a meandering meadow-stream, about five ales in length, of which 60 per cent is made up of pool areas and 40 per cent
riffle areas. It maintains a good population of trout, a spawning run of
trout, and is heavily fished during the regular trout season. Scale studies indicate that its resident fish grow rapidly as would be expected
from the abundant, available food present. There are at least five other
spring-fed streams on the west side of, and tributary to, Snake River which
are on reservation land and under the jurisdiction of the Indian Agency
Tribal Council.
Snake River itself is typical of a large, productive river.
Al-though it is subjected to fluctuation due to heavy spring run-offs
and irrigation demands upriver, it always carries a good flow of
water. It has deep pools and large gravel bars or riffles. unlike most
of the spring-fed tributaries, it carries a heavy population of rough
fish in addition to a fair trout population. Areas of it are fished
heavily dur- ing the summer months and produce fair to good catches of trout. The extent to which trout use Snake River for spawning is not known, no evi- dence of any beds ever having been seen in the lower area. With the T ring- fed tributaries furnishing excellent spawning areas, it is questionable if too much spawning occurs in this section of the Snake.
2. Spring Creek. As its name implies, Big Spring has its origin from a number of large springs all of which lie on the Indian Reservation. Spring Creek is located in the Snake River bottom midway between Snake giver and the cliff to the east which marks the eastern boundary of the river bottom.
It is the largest of six similar spring-fed streams flowing across reserva- tion land. The water temperature varies from 52° F. to 65° F. It has a slight gradient. In all characters except fish population, Spring Creek could be compared to Silver Creek in Blaine County. It contains large beds of Chara, narrow-leaf pondweed,(Potamogeton), tivrionhyllum and
Ranunculus, Its water is very productive of fish food which includes fresh-water shrimp, mayflies, stone lies, Caddisflies and snails, all available to fish. Tne extent to which spawning fish utilize Sprin: Creek
is not actually known. In May of 1949 there was no evidence of spawning
in the area of the county road bridge, and in August of this year, no small
trout were observed in the pools or along the shore. The only game fish
seen and identified through this area were whitefish. Spring Creek, with
its tributaries combined, give a stream about 14 miles long. Pool struc-
ture is average; food grade high. Spawning areas are sufficient for the
use of a migratory run of trout from the reservoir.
3. Clear Creek. This stream, another spring—fed bottom or meadow
creek is only one—fourth the size of Spring Creek yet maintains a steady
flow of 125 C.F.S. It arises and flows along the bottom of the cliff which
forms the eastern margin of the Snake River bottom. It has not been
exploited so fully as Spring Creek as is shown by numbers of small trout
seen and taken near the county road bridge in August, 1949, In the lower
reaches only one trout, a large one, was seen. In the upper end both
cutthroat and rainbow trout as well as their cross were taken. The
stream appears to be used moderately for spawning.
4. Portneuf River. The Portneuf, although subject to extreme fluctuation and some pollution, is at present the most productive fishing stream of those which empty into the reservoir on the reservation. It arises on reservation land some 40 airline miles northeast from its mouth but traverses approximately 85 miles of state and private land before it re—enters reservation land some four miles above its mouth. Upriver demands for irrigation are responsible for the low water of summer months below Pocatello but this flow is increased by several large springs before the Portneuf enters the reservoir. Batise
Spring, located near the Rowland
Dairy and one about a mile below this point (Meader Trout Farm) are privately owned. The former is used extensively by spawning trout and suckers. Two large springs are tributary to the Portneuf on the reserva- tion, Bartlett and Jimmy Drink. Both of these were used to a large ccrt
sp at present. awhin? c ° "'e4y of ro out ho f ` t e `1n1
w Ae flow of ater
Falls dam except during from the reservoir w r periods hen flood is tod Ou,,let us at floir ually Amer resches water the ican p eak 1S going ever Outl t t s i e the Suer 'yore is during 1'a, - o the Y llx•a- conen hidh~ hs when v~~nr+V r dune and ut' thro4 ~ Table 2 er s ni?h
RVdrograph – Sna-h- R St rlonth Year
r~Ysu )1 Oct., 1947 4440 IOW ro~,r3ph~ No , 5,020 1,930 3,465 651 31024 Ln~ 4fugation w ater j shed b3 . s 1948 flow 3urin the U• S. sure3u of `ocl_ in clusive. ti n the p ° shows outlet rni the eriod 1 normal. The outflow during this year October,was ' 947 to "'e~teu ber, just slightly above
Acre feet
213,700 130000 A cxl.un -pat ::an; treat he Lo: r the 3 .-e-ze eu contains suita0le spawning areas for trout but these _:.:^e not used hee.vilu at present,
Outlet
The flow of water from the reservoir is. regulated at the American
Falls dam except during periods when flood water is going over the spillway.
May Outlet flow usually reaches its peak during or June and continues high through the summer months when downriver demand for irrigation water is high. The following hydrograph, furnished by the U. S. Bureau of eclama- tion shows the outlet flow during the period October, 1947 to "-entember,
1948, inclusive. The outflow during this year was just slightly above normal.
Table 2
Hydrograph - Snake River Outlet Flow in C.F.S. October, 1947 to September, 1948 Month, Year High Low Mean Acre feet
Oct., 1947 4,440 1,930 3,46 213,700 Nov. 5,02 651 3,02 180,000 Dec. 4,950 673 4,22 259,600 Jan., 1948 4,96 689 4,09 251,900 Feb. 3,96 464 3,091 177,800 Mar. 4,33 175 2,650 163,000 Apr. 13, 73,24 8,19 487,400 May 25, 19,89 1 6 , 2 1,002, June 25, 610, 3 1 9 , 3 1,149,000 July 12, 211, 3 1 1 , 3 726,100 Aug. 12,1 10,3 1 1,2 693,000 Sept. 10,900 147 7,26 433,400 Total 5,736,
The average annual run-off of Snake River below American Falls dam from 1896 through 1949 was 5,714,000 acre feet. Highest run,-off occurred in 1913 with a flow of 8,601,000 acre feet, lowest was in1934 with a flaw of 2,568,000 acre feet,
-10- Fluctuation and Its Significance
Since American Falls Reservoir is a reclpmgtion project, it
is subject to severe fluctuation. The effects of this fluctuation on the
fishery of the reservoir are plainly evident. Table 3 gives a picture of the
fluctuation during the last 8 years. Since the reservoir has been full
during either May or June of each of these years, the maximum storage has
been omitted. This is 1,704,480 acre feet.
Table 3
Fluctuation of American Falls Reservoir Fluctuation Since Preceding Spring or Coming Spring Oct. 1 Storage, In feet, Year In Acre Feet Elevation % in Acre Feet
1941 319,000 1,385,480 35 81 1942 410,360 1,294,120 32 71 1943 897,050 807,430 16 47 1944 534,450 1,170,030 26 67 1945 924,820 779,660 15.5 46 1946 718,970 985,510 21 58 1947 686,770 1,017,710 21.5 51 1948 664,720 1,039,760 22 61 Average 644,517 1,059,837 23.6 60.2
Severe fluctuation in an impoundment has a tendency to devaluate the fishery of that water during both the period of rising, and the period of falling, water levels. The time interval during the two periods is about equal on this reservoir but there are two months, August and September, when the bulk of the water level fall occurs. Since these two months are the most productive for the growth of plankton and other fish foods, the fluctuation has a tendency to (1) concentrate the organisms (available for fish food) that escape the fluctuation, (2) concentrate the fish populations or squeeze them into a smaller space, (3) force an escapement of the latter over or through the dam or a migration into the fresher, cooler water near the mouths of inflowing streams. It is during these two months that the waters of the lower reservoir show the results of this concentration and the attempt of fish life to escape the unfavorable water conditions. Large mats of decaying algae form on the water's surface just above the dam. Marsh gas, escaping from these decaying organisms,
is discernible. Large numbers of fish, particularly chubs and perch, pass
through the gates into the forebay of the dam, some to take up life in this water, some to pass on down through the powerhouse turbines into the river
below. The fish populations in the forebay can only fret there, at least
originally, by passing through the dam, or over its spillway when the reser-
voir is full. Along the shoreline of the reservoir, particularly after a
windstorm, the results of this concentration of aquatic life and the resul-
tant death of algae and other plant life can be both seen and smelled.
Just as there is a concentration of organisms during the fall
of the water levels, there is a dilution of the organisms during the rise
in elevation of the surface of the reservoir. This, coupled with the large
inflow and outflow, has a tendency to deplete the mineral content of the
reservoir bottom and thus reduce the productivity of the water. This
depletion was greatest during the early life of the reservoir, but will
continue gradually throughout its life. The adverse effect of the rise in
water level on the fish of the reservoir is not as great as during the
fall. Their food supply is more scattered than during the period of low
water. Then, too, the fish, with the exception of kokanee and whitefish,
are seeking places to spawn. Their food requirements are becoming greater
with increasing temperatures and development of the gonads. The month of August shows the greatest decrease in the water storage of the reservoir. During 1948, for example, storage on AuEu st 1 was 1,310,000 acre feet. On September 1 this had been decreased to 850,000 acre feet or a fluctuation of 460,000 acre feet, a loss of one—third of the water storage and a fall in elevation of 10.5 feet! There was a similar fluctuation for the years 1941—47, inclusive.
CHEMICAL CHARACTERISTICS AND =MATURE
Chemical characteristics'and temperature of a water are important
in fishery management inasmuch as they are a measure of the productivity
14,af;no factors which thtermine the species best suited for a water.
Oxygen
Oxygen content of the water in American Falls Reservoir was
never found to be below the optimum requirements for trout. A series
of samples taken from the surface and at varying levels below the surface to
a depth of 50 feet varied in oxygen content from 5.4 ppm to 8.7 ppm. The
reservoir is frequently subjected to windstorms which tend to increase the
amount of dissolved oxygen in the water.
Alkalinity
The carbonate alkalinity of the water varied from 12.2 to 16:8 ppm
as CaCO3, the bicarbonate alkalinity from 142.6 to 162.4 ppm as CaCO3. The
period of highest alkalinity was in September; of lowest, in May. The water
would be classed as moderately hard and productive.
pH
The pH of the water was on the alkaline side, giving readings
from 7.6 to 7.9. This lies within the range of suitability for trout as
well as other game fishes common to Idaho. t•ater Temperature
There is no thermal stratification of any duration in American
Falls Reservoir. It is covered with ice each winter with water temperatures varying from 33.6° F. just below the ice to 35.4° F. in 32 feet of water. Since the surface is frozen each winter, there is the usual spring and fall turnover. This occurred, in 1948, during the months of March and April in the spring and November and December in the fall. If a thermocline is established, it lasts but a short time in the spring. Sur—face temperatures on the reservoir nary during the summer months from 61.9° F. (May, 1948, Station
4) to 69° F. (August, 1949, Station 7). At p the mouth of Spring creek, the surface tem erature in August, 1949 was
540 F. This temperature gradually increased to a constant of 69° F. aoout one mile out into the reservoir. Near the mouth of the Portneuf, the sur- face temperature was 58° F. in August, 1949, while a mile offshore it reached
660 F. the same day. The backwaters, then, have cooler waters through the slimmer than the open reservoir. There was, however, no heavier population of game fish here than anywhere else in the reservoir.
The absence of a thermocline in the sui er is probably a limiting factor to the establishment of a good population of kokanee er blueback.
Although no one will define the suitable habitat of the kokanee, they have established themselves in a number of lakes in Idaho which do have thermo- clines.
Table 4
Typical Spring and Fall Vertical Temperature Readings, American Falls Reservoir
May 29, 1948, Station 1 Sentember 15, 1948, Station 4 Depth Temp. ° F. Depth Temp. ° F.
Surface 62.5 Surface 61.9 5' 62.4 3' 61.6 10' 62. 6' 61.56 15' 62. 9' 61.5 20' 61.9 12' 61.5 25' 61.3 15' 61.5 30' 60.6 Bottom 16' 61.5 35' 58.5 40' 53.1 45' 52.2 50' 52. Bottom 54' 51.9
Pollution And bollution within the reservoir from
Although pollution is more of a concern with public health than with fishery work, it does have a definite harmful effect on aquatic life. Only that aspect will be discussed.
There re three sources bf pollution on American Falls
Reservoirs Pollution from industrial plants which dump wastes into the ~ of the rcliutieh fros the first two sources hover reecnee '-
reservoir it ae:_ Averse effects uvon eeuetie orgeinisme is the eackweterE
where i t aecrc:see trio availeUle oxyeen increaeee the acidity and
am. onie in tee weter. There has been no evieence found ef fish—kills due to
the entrance of these effluents into the reservoir.
;non: the industrial of ants alone; the two rivers which dump
r untreated effluents are su47ar and starch factories, an oil refiner:, ail—
road shops, e fertilizer elant, dairy industries and ttchihh elents. lest of
the tome one cities alone the river:: dump raw sewae. The forshtion of
marsh ass, by- decaying al'ae in the summer monthe is very notice—
able. However, since this 3.1 ae is near tee surface or or the surfece, most
of the gae eecapes or is dispersed by weve action.
It the time the solid raw sehaee and commerciei. pollutente reach the reservoir bacterial action has made them buoyant or seal—buoyant.
Here, in the beckwaters and is the absence of eave action for seve oys, they for, wit oil wastes, e surface scum which sometimes wiiI cever several hundred acres, particularly near the mouth of the ?oTtneuf. A bottom ncliutiee blanket was found in the reservoir in the mouth of the Portneuf. It was also noticeable in the 'ortneuf above the reservoir. Such a blanket tenae to smother out certain forme of bottom faunae which are reulaced by =re tolerant forms. :o soraoles of bottom faunae were taken in the river i eelf.
CHid'.hC11,;.S
Veg.etation
The most abundant form of aeuetic veetaticT. found in the reservoir ie seecies of smarteeed, :'-olvechum. Thies seecies is amnhitious and is te foe no throughout most of the ceckw.,ter area of the reservoir as well as in score of the protected bays on the east and west side. It ha:
11, est:1bliL,nou Itself in then areas to eeoth of about feet ana affords
fishes and breeding areas for perch, which use those beds, ide.]7 for tr.: sees) -- co' teeir cg::, ee s:11 e7ueele iseeete.
the shoreline recedee, mats of smartweed ere left exessed.
jther aquatic plants, which ere te ec foune in reservoir areas
suitable ; Loeir rooting and grovth (this axcludee all sandy shoals), are
Darrow-leaf oondweed, potamosetan sp. ruffled or clasoing-leaf pork:weed, jotamoeeten so. io.n.agnum moss, ::ohagnum so. cater nilfoil, ;yrioeSyllum on.
Severel species of marginal weter :raseez, belrush, aria sedge
were observed out riot identified.
The submerged and emergent plants of the reservoir are .import art
te fish life both directly and indirectly. They afford shelter and shade for
youn fish and food for carp and suckers, seeve ac food factories and conseeuently
feeding areas since they harbor any forme: smell aquatic life,
for:: naeitsts for the denosition of eggs, and aid animal life by
o;ryenating the water. Men the surface the reservoir iroes to 15 feet
or more below the full elevation, a vast majority of the ace:tie elant life
is stranded and the fish l i f e is deprived of this feed, shelter, etc.
It is apparent also, that only the amohibicus olcints in the roue of t i - eneials or nerennials will survive this annual drying or stranding. The annual plant:, reseed themselves each year.
Fish Foods
Available fish fo ds are abundant in many forme i n American
Falls reservoir, oarticularly eurins the soring and early summer months.
In the late summer and the fall months there is a noticeable decrease in their abuneence which correlates with the fluctuation in the reservoir.
I, nee -clatic and aerial forms. Insect forms available as fish feed include meyfly, damsel, and dragon fly nymphs and adults, di terous larvae and adults, beetle larvae aria adults, and etcnefly adults. The imoortance of the adult aerial form can be seen on the reservoir by the action of
-1 surface-feedin: fis in the absence of wind. !:ost of this Eurfa'e feeding if done V7 nerca and chubs. nails ofla nneciee of fresh-wester ehrimh G, ...... ur coo) "re i r l common in the r ,::rvoir one: it is n:-:r full copecity. No quantitative stomach analyses hove b,en mode, ne yet, to determine the correlation or lack of correlation between available
fish food forms and the relative nbundance of those forms. In qualitative analyses, all forms mentioned above have been found in the stomachs of trout, perch, and chubs.
Plankton. The abundance of plankton also shows correlation with reservoir fluctuation. Spring quantitative hauls took from 2.75 to ?.^ cc
of plankton for each cubic meter of water. Fall hauls ;r.oduced from .36 to
.4 cc plus 4.1L: to 4.6 cc of detritus (BC per cent of haul) which consisted orinciially of the decaying vegetation mentioned nreviously. Although this quantity of nla.nkton could only be considered everabe for a productive water, the dominant forms are those most often us.d by small fish for food.
Qualitative studies of the plankton and their re1.-tive abundance in the total p1:nnkton is given in table 5.
Table 5
Plankton and Their Relative Abundance in American Falls Resevair
Tvne Class or Order. Genus &el^tine abund.
% p Zo inlenkton: Copepoda ,Cyclo s sp. & nnunlii abundant Cladocera Daphnia sp. Rotatoria Anurea sp. Common 5prcodina DiffluEia sp. fairly commo Fla :ellata Ceratum sp. common Phytoplenkton: Bncillariaceae: Asterionella sp. common Stephanodiscus sp. rare Cocconema sp. p n Fragi1lari sr. 11 Cvmbel la sp. Synerrr sp. n n Cyanophyceae Oscillatoria sp. common
Bottom Foods. No bottom organisms were recovered in water below the :0 foot Tenth and the 'nlr form ta'_-en in shoal water was a species of oligochnete worm. It is evident that the extent to which bottom organisms form the a.ot of fishy-s is negligible. No microscopic examin• tion war made of e a i ; it ties e amin u for v i l e f^rr only.. The extreme fluctuation
of the reservoir could be responsible for absence of ^re bottom org'nirms
since most species carrot withstand desiccation.
?ishes
A provisional list of the fishes taken from American Falls Reser-
voir is given. This list is divided into game and rough fish, both native and
exotic.
Game fish native to the reservoir include:
Cutthroat trout, Selma cicrkii lewisi Mountain whitefish, Prosonium williatnsoni
Genie fish which have been introduced are:
Rainbow trout, Salmo airdnerii irideus Kokanee or blueback, Oncorhynchus_ nerkr kennerl:-i Yellow perch, Percr flavescens Mudcat or brown bullhead, Areiurus nebulosus
ion—game fish native to the reservoir are:
Utah lake chub, Gila atrarir, domnina Rosyside tucker, Oatastomus ardens (fecundus) Silverside minnow, Richsrdsonius balteatus hvc_'rorhlox Scilpin or meuntrin bullhead, Cottus bnirdii eeniecober
::on—game fish introduced:
Carp, CSrorinus car-oio
Not taken in the reservoir itself but found in it; tributary streams are the following species, all non—game:
Mountain sucker, P?ntosteus iordani Dusky Dace, Rhinichthvs esculus carrinztonij Sculpin or mountain bullhead, Cnttus tubulatus
Another species of sucker, Csatostonris cotortomus rocrvello, has been described from the mouth of Ross Fork Creek, but was never taken in any of these collections.
C^m.)arative Populations and how derived. Enough gill net :et: were made in the reservoir to obtain a good sample of all the fishes susceJtille to s gill net. Meshes of 3/4-, 1—, l.—, 11—, 1 3/4—, and —inc} 2nets v':re used at six of the seven stations on the reservoir. Tine were set deb he-a on tXE- surface, ff shore ^na in o e. :er. _• t' u of
these £etF and the rerul:s are shown in table 6.
Teble 6
Gill Net Sets and C^tches, American Falls Reserv-ir
Numbers taker. Total St^tion Hours Suckers Chubs Perch Trout ;,`hitefish
1 19 137 26 7 --- 1 3 35 163 147 60 2 4 24 86 57 37 5 2b 24 l07 26 6 16 15 97 --- 2. 7 14 66 75 5 ---
Totals 1 3 2 1 326 175 5
For each trout taken, then, there were 27 perch, 65 chubs and 98 suckers. The whitefish and kokan2e populatisns were insignificant or some would hpve been taken in the s males. Car- are not susceptible to gill nets but computing from commercial fishing catches they re almost as numerous as the suckers. Sc_lpins, dace, and silversi,:.e min:_o-e ire not ta':en in the gill nits.
Relationship of the Species to hac: Other and Their Environment
A fishery management survey would not be complete without a dis- cussion of the ecology of the resident fishes. For the sake of brevity, however, only those phases of the ecology will be discussed which have a bearing on the decline of the sport fishery.
Trout. Trout are the least capable of standing up under he=v. competition and the least prolific of the fishes found in Americ'r Malls Reservoir. All of the game fish and the chub comaete directly with trout for food. Cap are omnivorous feeders and therefore m.oy compete directly with trout for food.
All other fishes compete with the trout for space. The carp, and the suckers to a lesser extent, feed on aquatic plants which might be called food factories and shelter for game fish. In its turn, the trout fees or the your& of other fish' e t^ sms.11 _:tent. hsi olci trr
fish, the trout seeks an environment in clean, cold water. I_f he fails to
find it in his immediate habitat, he migrates. The r_ servoir nffor::s suit-
ble habitat for trout except during the months of ru_;urt, September and
October. The extreme fluctu"tion with relotively high tem;ieratures,
decrease in food supply, and cresence of obnoxious gas in the water during
these months m.^kes the lower reeches of the reservoir unten-hie and the
trout either got's throw the dam or folio• s the currents into the back-
.:rters.
The trout population has never been over-exploited in the
reservoir by sport fishing. Many more rough fish are reaoved erch year by commercial fishermen than trout by sport fishermen; and ;-et the decline continues. Fish planting records (see table 7) show th,t almost 7 million trout have been planted In the reservoir and adjscent tributaries over the past ten years (1939-1i8 inclusive). V ry few of these fish h-ve found their way into the fisherman's creel on the reservoir itself. Fa:-lure to compete with other fishes. and, or, undesirable habitat are the only explana- tion.
Perch. The perch is a cool-scter fish; its habitat reouirements are not so narrow ae the trout. It can withstand hi, er temperatures, is more voracious in feeding habits, and is not too eencitive to silt or impurities in the
:Inter. Although there is an overlapping in habitat between the two sp'cias, gill net catches show a rather sharp line of cem_.rcation in the perch habit.st during 1^te su.mmc=r months from the trout habitat.
The perch fishery has not beer over-ex-sloited snc'. remains fairly constant. This is born out by the continued. large sire of erch, year after ye'r. The e is an eecanement of --erch throu:;h the dam which is difficult to explain. Most of these are smaller rerch which may :;e csugnt in the current and are wept through. This escapement is another reason Why -Serer do nit show over-Spulati^n in th_- reservoir with the r"sultant ran^r.qa,. in size. hoknnee An _tte,:ot wee msee to :eeta: l i sn c:)'._
lode : sockeye salmon in the reservoir in 1942, 4, 5, and It i.; nct
known, as yet, just hog successfu2 this, attempt has been. The burl, of the
stocking was done in 1941- when over a million kokenees were eianted. Scale
sample studies in adjacent eneke '?fiver waters here indicated that the kokanee
matures sexually in two, throe or four years with the majority maturing in three.
If the kokanee is to establish it elf then, we could expect a: excellent snahrinF run in 1947 and again in 1950. fair run
was observed in 1947 in the Crystal Drain, some have been seen in the Mack-foot
Giver, but the bulk of the elanti n ;s anpeers tc have drifted over or throw}-, the dam and down into !inidcka oar: back%:titers whe e they eeee to be establishi nr a fair po 'nl_tion.
Kokanees, until their year of sexual maturity are 2 oet excli_-sively plankton feeders. :)ur .nu their year of maturity tee:- may feed on larger organises. I t is during this year that they -aast :tie taken by s ort fishermen if they are to be harvested, since, like all Fecific calhen t, die after spawning. Apparently, the downstream escapement is due tc sc.me factor in the habitat which makes it uncesirable. This could be to:'."eretore or chemical condition of the water. bullhead catfish. The bullhead has been introduced Into the reservoir in recent years. Pow or by whom is not known. I t has shsl.:n up in commercial catches in small numbers since 1946. :hen this shecies has estj dished itself in the reservoir, it will tiring new problems in mane e-ent.
Fish Plantings The following table nets the fish nlant_n-:s by en cies for the years
1939 to 1948, inclusive, in the American Palls Reservoir and adjacent tributaries. These tributaries incluJe Ross Fore, Clear, :)nrins:, Jimmy, and
5es:neck Cresks on the reservation, Dingle, 1.icTucker, Gremon, hiefen, Heet, and Tilden Sprin;-s on the west side of Snake, as well as 5n_Ke :fiver a.ant ins :-elor: „he ?'i.l..er h rid e area. :lees of fish ere _liven only for
~,...~ 1_1 noires. Table -
Fish Plantin,z Record. :'.ericun Falls Reservoir and Adjacent Tributaries.
Year a± cow Cut. thro :t iir: e k Annual Tot el
1939 245,300 245,300 1940 lol,b85 390,000 559,U85 1941 411,820 302,000 45,000 75:3,820 1942 108,525 785,300 1;1,003 1,084,825 1943 105,230 1,021,20 1,12!,,350 1944 731,890 853,000 1,1`?8,8 0 2,373,770 1945 73b,770 40,000 255,0c0 631,770 1946 55,470 034,915 212,000 71e,585 1947 c3,723 181,790 245,513 1948 ___:11,22f. ~ 27;',537
Total 1,295,748 4,411,527 45,000 1,002,880 8,015,155
.;vera,;e of nt!year : 801, 515
:'red etors There are a number cf :red acicus birds living on .1nd ne°tin, ne _r the rese voir. Included among these ere 'elicans, blue herons, nie.nt herons,
::reties, terns, gulls, mergansers, lo ns, lesser e-rets end ecru or,nts. 0o-ne of these species subeist al:eost entirely on fish. Since their diet consists almost entirely of rough fish, however, little harm is acne to the ,came fish in the reservoir. The only place they co'.:ld do damage to game fish populeti:r.s would be in the tributary etrca s.
Cl/V.i,:.Li.ii. F :.,:,F'::. t'., !, commercial fishery has existed on the reservoir for se'.time. Fichernen seine for carp, suckers, and chubs In the backwater areas. •.)f these three: species, the carp has the hi:-hest ce-.^.-ercial value, fcilowed by the sucker, then the chub. ddthoui-h complete catch statistics arc not available, the toss annual revenue t e the fisherman must be in exce_ s of „15,00:; for reservoir waters. watch statistics for cne of the three seiners w orkinF the reservoir is given in table 8. Commercial fishinc catches of one seiner on American Falls Reservoir 1944-46, inclusive.
Species and Pounds Year Carp* Suckers* Uninentifed Annual Total
1944 26,650 3,925 100,000 130,575 1945 48,963 30,207 104,200 183,370 1946 92,060 44,750 116,280 253,090 1947 10:;,200 57,110 10,000 167,310 1948 102,528 55.542 20,000 178070
Totals 370,401 191,534 350,480 912,415
*Dressed weight If the avera.e annual catch of the statistics in Table 8 is
doubled to allow for the catches of the seiners not included, there is
harvested annually from American Falls Reservoir about 182 tons cf rough
fish for a yield per acre of roughly 10 pounds.
The commercial fishing has had no adverse effects upon the sport fishery in the reservoir, nor has it heel much good effect. ,isi e from removing quantities of bigger fish, thereby helping stabilize the popula- tions by preventing an •verpopulation, it has done little good, The small fish remain to rrow up and help repeat the cycle. It does have a place in the fishery picture because it is harvesting a crop that should be harvested.
THE INDIAN FISHERY
Although there is no Indian fishery on the reservoir, there is one on the streams tributary to the reservoir which must be considered.
Members of the tribe are not limited by season, methods, nor limits while fishing in waters on the reservation. Non-members who purchase the seven- dollar permit moy fish certain reservation waters but they are subject to state fishing regulations, especially creel limit. The reason for this is obvious. The absence of limitations on tribal members has brought about ar over-exploitation of reservation streams end the resi:ltant losses miyers.
The heavy exploitation of the excellent spawning streams on the reservation was started years before the reservation was in e.xi.ctence.
In the early nineteen twenties the State Fish and Game Department operated a spawn-taking station on Jimmy Drink under agreement with the Tribal
Council that all fish reared from this operation would be returned to reservation waters. Members of the tribe, however, could spear fish enter- ing the traps, remove boards from the trap and sear escaping fish, or erect traps below the state traps. The state aency soon withdrew. This same stream was blocked with chicken wire barriers during the winters of
1946-47 and 1947-48. Remains of old spearing stands still are to be found at the mouth of this stream. Of the six excellent spawning =end rearing streams on the reservation only Clear Creek shows any remains of a spawn- ing run.
Alone with the over-exploitation of reservation waters by both
Indian and white was a aecrease in the numbers of fish planted in these s t r e w until, in 194f, no fish at all were requisitioned by the Council, and few fish were planted by any agency, state or federal.
CCNCLUSIGNS
a gradual decline in the 1. It is evident that there has been trout sport fishery on American Falls Reservoir and that this decline has been due to a number of factors:
(a) Severe fluctuation with attendant heavy inflow and outflow, which causes:
(1) A decrease in food supply for small fish and
plankton feeders during late summer,
(2) An approach to optimum-maximum temperature
for trout,
(3) The death of aquatic plants with their decay
and release of march gas which crakes areas of greAter ...,:oe,als rnr trout (4) Tile escapement a_ aisn , `.:e r.. Fic j fine tnf ,:t._ ^ .. undesirable.
(b) Heavy populations of fishes which are in direct com-
petition with trout for food (perch, chub, carp), shelter ( a l l speciee), space
(alb species) and indirect competition with trout for food (carp, sucker).
(c) Over-explcitation of spawning streams tribe:tar; to the
reservcir or the lower ends of snake and 'ertneuf Rivers, particularly on the
reservation..
(d) 7e>ther
(e) Lack of fishing euccess
2. Age-;rowth studies of resident speciee of fish ,how no overpopulation or approach to overpceeilation in the reservoir. Factors which contribute to this are :
(a) Large escarerent of fishes over and through the dam,
(b) Rough flub removal by commercial seincrs,
(c) Predation upon rough fish by fish-eating birds.
M:''7AGEi4ENT PR. 'CSALS AND DISCU',SIOU Now that the decline of the sport fishery in thier:ican Falls
Reservoir and its causes are recognized, the problem remains as to what can be done to improve this fishery. Before going into that perhaps this qu:stion should be asked: Just how good can we ever expect the sports fishery in the reservoir to be? Perhaps the answer to this will unravel itself through the following discussion.
Let us first dispose of management proposals which cannot be carried out. The water level of the reservoir cannot be regulated--it will always fluctuate. Population manipulations are difficult in water this large except through the introduction of a voracious feeder. This can be considered leter under stocking pro ram variations. Predator control would not be of much help since the predators are do;rg QC) per cent good
e 4 .. 4 .rnw•.r}.i h cause of fluctuation I I7
IN t'I
1u1'10, i
let I
vjriidi
,,.t !~.. M~' ;11~~ ~, C~ ~:7~ 7t"0''cam clE4. U^r1Llt1l ~~
ii,1r I/1J fishing regulations. rerhap: in one or both of these we can find the solu- tion as to how the sport fishery in the reservoir can ue improved.
CHANGef IN F13HING E ULATICNS The present re;:alations governing state waters concerned in ttis survey are satisfactory as now set up. tinter fishing is necessary if the perch are to be harvested. Very few trout are taken in this winter fishery.
Creel limits, methods, and seasons on tributary streams are satisfactory-- further tightening of regulations would only result in the loss of many of the trout now harvested in these waters. There remains only the waters on the reservation where changes in regulations could improve the sport fishery on these streams as well as on the reservoir.
As has been pointed out, the reservation waters have been over— exploited by the Indian and sport fishery. At the same time restocking of these streams has been neglected. :officials of the agency are cognizant of both these facts and the resultant loss of revenue from ?emit buyers. The
Tribal Council is hesitant to deprive the members of the tribe their fishing rights as set us by treaty with the United States at the time the reservation was formed. Yet to further delay the tightening of regulations for the protection of what little brood stock is left will eventually mean the total loss of that stock. If this were to harnen, the Indian, in the loss of the fishery, will have lost his fishing rights, and the tribe will have lost all revenue from peri.it buyers. The depleted populations in
Spring, big Jimmy, Clear, and other streams on the reservation can be rebuilt by wise stocking--if these rebuilt populations are given some protection, particularly during their spawning seasons. Regulations to this effect are only sound management. The Indian does not kill his ewes before they have lambed nor his. cows before they have calved, yet he continues to kill his trout before they have spawned. Soon there will oe nee.:. left to spewn.
The protection of brood fish in reservation waters will build up
the resident populations in these stream: as well as in reservoir be.ckwat:
rs, and a centinuin;- supply will be aeeured. It is neze3sars', first, to
rebuild the population of brood fish.
The loss of broad stock populations in reservation eaters cannot be
blamed on all member:: of the trite nor upon all th: wite permit holders. It
can be blamed directly upon those fey who have taken advantage of their rights
for commercial purposes.
Stocking Program Variations
To be considered under stocking -rogra.': variations are such items
es species, numbers, sizes of fish to be stocked, steckik sites, and the
intro..uction of new soc ties.
Rainbow Trout. i?urir, the years 1939-4r', inclusive, `,here were :,895,748
rainbow trout planted in the waters covered by this report. The largest
nuaber planted in any one year was 411,820 in 1941, the smallest, 55,470 in
1946. Plantings in 1946-48, inclusive, were lower in number but the fish;
were larger in size so that if recognized survival rates apply, the numbers
are comparable. Plantings during the earlier of these years included
reservation streams while those of the later years excluded those waters.
From 1944 to 1947, inclusive, 117,860 3- to 6-inch rainbow treat were planted
directly into the reservoir and yet it is doubtful if more than three or
four per cent of these have found their way into the fisherman's creel on the
reservoir. L:here do these fish go?
Rainbow trout plantings have been carried on rather consistently in the streams tributary to the west side of 'nake River and these. streams continue to furnish good fishing. Certain areas of the reservoir which have been stocked in recent years continue to furnish fishing viz., the
areas around Aberdeen and et the mouth of Danielsen Creek. These former
lantint,s h eve, .perhaps, added to the f_ sti ng success in ;n ke 7:i ver itself, belot. the dam.
Of the reservatien eaters, Springy; Creek was planted in 1939, 40,
41, 46 and omitted in 1942, 43, 44, 45 and 47. This is Evident in the low
resident-trout population. Clear Creek was stocked in 1940, 41, 44, 45, 46,
47 and omitted in 1942, 43, and 48. The more regular piantin_s in Oleer creek
re in.evidence.
It is doubtful, from poet planting records, that any v_ ri:iticns
from the present prectiee in stocking of rainbow trout will add to fishing
success in the reservoir. If the rainbow could establish itself in the
reservoir, it would have done so before now. Thee are too many adverse
conditions existing in the reservoir, such as trash fish competition and
conditions arising from fluctuation, which the rainbow c:n neither tolerate
nor overcome. However, the areas now furnishing fishing can continue to
furnish fish nr by wise plantings in those areas. Similarly those areas which
have been epleted can be rebuilt so they will again provide a sport fishery.
Cutthroat Trout. Vah,at has been written about the rainbow trout will ap;:ly
largely tc the cutthroat except that it is less tolerant to adverse water
conditions and more tolerant to rough fist, populations, the young of which
it forages on. It too, however, cannot compete successfully too long with
the chub or carp.
The cutthroat is the species of trout native to these w ;tens.
It appears more often in the averaee creel. It has been planted consistently in the reservoir and tributary streams, first through the 1920's, and again through the 1940's. Yet, it too, shows in the creel sparingly for the numbers planted. From the large numbers planted (1,021,320 in 1943, for example), and because of the fact this species is native, one would expect to find it well represented in gill net samples, yet it appears only once in every 357 fish taken. since it has not been able to establish itself in the reservoir (cannot comne le with rough fish or finds water
~~ _ .. a...... ;.. ;1 .lf is a CLL.
waters am stockinzs to this enc sho:.:ld be carried on. Its ariit into
backwaters, once populations are rebuilt in reservation streams, will fur-
nish fishing in this area.
Other Trout. The consideration of the introduction of new species of fish
should include two separate discussions: (a) Can the fish establish itself,
or, are conditions suitable for its establishement, and () ;:hat effect will
its introduction have on other sport fish populations here and in adjacent
waters.
New species of trout which might be introduced into the reservoir
are the eastern brook, brown, and mackinaw. Conditions are not suitable
for the brook trout since its temperature tolerance is below reservoir
waters, nor the mackinaw since it requires a thermocline. The brown trout
is as tolerant to adverse water conditions as the rainbow and can withstand
hi(her temperatures. It is also more voracious than the rainbow trout.
Being no more tolerant than the rainbow, however, it is doubtful if it would
establish itself to the point where it would furnish any more fishing than
the rainbow does at present.
Ware-water Species. There are two species of warm-water fishes which could
improve the sport-fishery outlook in the reservoir itself. These are the
largemouth black bass and the crappie. One would hesitate to introduce
the largemouth bass because of the harmful effects it could have on the
trout fishery downriver. Then too, this species is not tolerant of rapid
changes in temperature nor of extreme fluctuation, and murky water. A
sudden windstorm with a drou in temperature during the nesting season and
the eggs die. Severe fluctuation results in desertion of the nest and
the death of the eggs.
The crappie, on the other hand, would not harm the downriver trout
fishery, is much more tolerant of fluctuation, murky water, and changing temperatures. It can be taken on flies, with bait or by trolling. Its flesh is excellent. It could establish itself and would furnish good e-r- 1. it IL V s; c aown the rcu;r: fish populations. It would not cnan. t the outlook for
improved trout fishery in the backwaters or tributaries. nly one factor is against its introduction. It is little known in this section of Idaho rsid until i t b com. s known there would erobably be l i t t l e fishing done for i t . It is a prolific species and tends to overp o p ulate, so it :mist be fished he vily if i t ie tc maintain a large size. The one bid- q uestion in its introduction is whether or not it will be utilized.
its. i„ l~i':1...... Di. Ali From this survey and a careful ccnsir:er::tion of all the data, in order to improve the sport fishery of the American Falls Reservoir and its tributary streams, it is recommended that:
I. Present trout planting policies be revised so that, the max.i-^ill"s amount of trout fishing can be realized in these suitable ere'ls cf the reservoir and in the tributary streams;
2. A trout-p lanting program be set up for reservation streams, provided that the Tribal i.c,unci i recognizes the over-exp loitation of these streams and the threatening loss of their trout fishery and will set up regulations to ; rctsct these fish during; their period of spawninc, and --re- vent core. cialisc; by members;
3. The introduction of a harm-enter species, viz., the era:-ie, be consiaered in order that the ;o'er portion of the reservoir will be utilized by a sport fish, provided that enough interest is shown in the nrespect of introduction and utilisation of this species. r' MONTANA ~
Yellowsto n.e ParK 44,1 i t it is ! r it . it
1 .1 Fails e/ 1 aina je Fusin, We River Above 4hlerr can g alls :'o-!
,o 20 d es /DA HO
-air? aye Area //,644 I.n./
------U TA H 0nd• si.ca-, beds: s a~~ R.
Po.tne,J R. gP„.i C.. L Clear Cr. Banno, Cr soot L.ond;nys 2,3 - s#.t-ie. Locat,.ns
Abode eq FiG. 2 AMERICAN FALLS RESERVOIR At E/edaton 4354 Scale: l''= 25ma:
/t telue[al aro ' U.S.Q Ri.. Map Saar.eci .4 1122 3eµ
Plate 1. American Falls Reservoir from the dam, looking north. Shoreline typical of east and west sides.
Plate 2. American Falls Reservoir looking south from above Station 7. Backwater area near mouth of Portneuf River.
Plate 3. Backwaters of American Falls Reservoir from above Station 7, leaking northwest.
Plate 4. Clear Creek at the mouth of Ross Fork Creek, with the river bottoms of the reservation in the background.