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San Francisco, California



NATE MILNOR, President Los Angeles

GERMAIN BULCKE, Commissioner San Francisco

EDWIN L. CARTY, Commissioner Oxnard

LEE F. PAYNE, Commissioner Los Angeles

W. B. WILLIAMS, Commissioner Alturas

GEORGE P. MILLER, Executive Secretary San Francisco


A. C. TAFT, Chief- San Francisco

A. E. Burghduff, Supervisor of Fish Hatcheries San Francisco

Brian Curtis, Supervising Fisheries Biologist San Francisco

L. Phillips, Assistant Supervisor of Fish Hatcheries San Francisco

George McCloud, Assistant Supervisor of Fish Hatcheries Mt. Shasta

Allan Polhtt, Assistant Supervisor of Fish Hatcheries Independence

1 >. A. <'lanton. Assistant Supervisor of Fish Hatcheries San Bernardino

Karl Leitritz, Assistant Supervisor of Fish Hatcheries San Francisco

J. C. Lewis, Assistant Supervisor of Fish Hatcheries Tahoe

Ed Clessen, Foreman, Fort Seward Hatchery Alderpoint

William Berrian, Foreman, Fall Creek Hatchery Copco

Archie Thompson, Foreman, Yosemite Hatchery Yosemite

John Marshall, Foreman, Feather River Hatchery Clio

A. N. Culver, In Charge, Kaweah Hatchery Three Rivers

Donald Evins, Foreman, Lake Almanor Hatchery Westwood

Ross McCloud, Foreman, Basin Creek Hatchery Tuolumne

Peter Topp, Foreman, Burney Creek Hatchery Burney

C. L. Frame, Foreman, Kings River Hatchery _Fresno

Harold Hewitt, Foreman, Prairie Creek Hatchery Orick

J. L. Stinnett, Foreman, Brookdale Hatchery Brookdale

Harry Cole, Foreman, Yuba River Hatchery Camptonville

Clarence Chansler, Fish Hatchery Man, Madera Hatchery Madera

R. C. Lewis, Foreman, Hot Creek Hatchery Bishop

Cecil Ray, In Charge, Kern Hatchery Kernville

Joseph Wales, Biological Surveyor Mt. Shasta

Leo Shapovalov, Senior Fisheries Biologist Stanford University

William Dill, Senior Fisheries Biologist Fresno

Elden H. Vestal, Junior Aquatic Biologist June Lake

Chester Woodhull, Junior Aquatic Biologist Fresno


J. S. HUNTER, Chief San Francisco

Gordon H. True, Jr., In Charge, Pittman-Robertson Project San Francisco

Donald D. McLean, Economic Biologist San Francisco

Roy M. Wattenbarger, Supervisor Los Banos Refuge Los Banos

L. H. Cloyd, Supervisor Gray Lodge Refuge Gridley

Russell M. Reedy, Supervisor Imperial Refuge Calipatria

Ralph R. Noble, Supervisor Suisun Refuge Joice Island

Joe Vlasnik, Jr., Supervisor Elk Refuge Tupman

John R. Wallace, In Charge, Predatory Animal Control San Francisco

Asa L. Brown, Supervising Trapper Beaumont

John L. McDonald, Supervising Trapper Redding

O. R Shaw, Supervising Trapper Salinas


AUGUST BADE, Chief Yountville

E. D. Piatt, Superintendent, Los Serranos Game Farm Chino

C. Van Ornum, Superintendent, Yountville Game Farm Yountville


RICHARD VAN CLEVE, Chief San Francisco

aH. Dado, Assistant Chief San Francisco

W. L. Scofield, Supervising Fisheries Researcher Terminal Island

G. H. Clark, Supervising Fisheries Researcher Stanford University

Frances N. Clark, Supervising Fisheries Researcher Terminal Island

Harry C. Godsil, Senior Fisheries Researcher San Diego

Donald H. Fry, Jr., Senior Fisheries Researcher Terminal Island

Richard S. Croker, Senior Fisheries Researcher Terminal Island

J. B. Phillips, Senior Fisheries Researcher Pacific Grove

Paul Bonnot, Senior Fisheries Researcher Stanford University

S. Ross Hatton, Senior Fisheries Researcher Stanford University

Geraldine Conner, Fisheries Statistician Terminal Island

(Continued on page 135)

California Fish and Game


Volume 28 SAN FRANCISCO, APRIL, 1942 No. 2


A Fishery Survey of the Colorado River Below Boulder Dam

*_ _ James W. Moffett 76

Pox Ranching in Southern California Edward L. Vail 87

Relationship of the Fresh-Water Mussel to Trout in the Truckee

River Garth Murphy 89

Economic and Geographical Relations of Aboriginal Fishing in

Northern California Gordon W. Hewes 103

Progress Report on Adult Salmon Tagging in 19:59-1941

G. II. Clark and S. Ross II, it ton 111

A Second Progress Report on the Central Valley Fisheries investi-
gations 8. Ross Hatton and G. II. Clark 116

Editorials and Notes

Twentv-nve Years Ago in ''California Fish and Game"

Richard 8. Croker 124

.Mackerel Shark (Lawna nasus) Taken in California

Richard S. Croker 124

Potassium Hydroxide (KOH) as an Aid in Food Habits
Research Walter W. Dalquest 125

Compilation of Information on Wildlife Research 126


Pond, Lake 'and Stream Fishing Richard S. Croker 127

Who's Who and What's What in Fly and Bait Casting in the
United States, 1864-1941 Richard 8. Croker 127

California Fish and Game is a publication devoted to the conservation of wild-
life. It is published quarterly by the California Division of Fish and Game. All
material for publication should be sent to Richard S. Croker. editor, California
Division of Fish and Game, Terminal Island. California.

The articles published herein are not copyrighted and may be reproduced In
other periodicals, provided due credit is given the author and California Division of
Fish and Game. Editors of newspapers and periodicals are invited to make use of
pertinent material.

11262 ( 75 )


By James W. Mofpett
V. S. Fish and Wildlife Service,
Stanford University, California


Curbing of the rampant Colorado River by construction of Boulder
Dam has formed a body of water of great magnitude in an arid desert
region and changed the river itself below the dam. The presentation
of data collected during a preliminary survey of this area and formula-
tion of a tentative management plan for the fishery are the purposes of
this report.

A genuine interest in the problems of Lake Mead and the Colorado
River below Boulder Dam is shown by all sportsmen's organizations,
civic clubs, and governmental agencies in Nevada and Arizona. It is
largely at their request that the investigation was made on which the
following report is based. Many individuals and agencies cooperated
wholeheartedly with the author in the investigation. Thanks are here
expressed to workers in the U. S. National Park Service, the U. S.
Bureau of Reclamation, Boulder Tours Inc., members of the U. S. Fish
and "Wildlife Service stationed at or near Lake Mead, and to the Clark
County, Nevada, Fish and Game Association, whose warden, Mr. Frank
Allen, gave many aids and services. Mr. R. F. Wright, owner of
Willow Beach, furnished much valuable information and assistance in
the work on the river.

Several unpublished, preliminary reports have been written on the
trout water below Boulder Dam. Dr. H. S. Davis and Dr. Paul R.
Needham visited this area and reported their findings. Mr. Fred J.
Foster submitted a report and recommendations on the river. Mr.
Dave Madsen also reported on a 6-day investigation of the river. The
author has drawn freely from these excellent reports. Many of the
recommendations given in this report were advanced in the writings
cited. Wherever this usage occurs, the author wishes herewith to
acknowledge priority and extend full credit wherever it may apply.

The Colorado River has been noted in legend, history and folk lore
for many years. Its turbulent, muddy waters have instilled awe, fear
and a genuine curiosity in the hearts of many from the Spanish con-
quistadores to the present-day tourists who view the Grand Canyon
from points a mile above the river. Explorers and river men have
navigated its channel ; some successfully, others only to find a grave in
its yellowish silt. The erosive work of this river is amazing, especially
since geologists consider the river's origin as quite recent. Blackwelder
(1934) 2 places the river's origin in the Pleistocene.

1 Submitted for publication, January, 1942. Published by permission of the
U. S. Fish and Wildlife Service.

2 Blackwelder, Eliot : Origin of the Colorado River. Bull. Geol. Soc. America,
Vol. 45:551-560.




Practically all waters of the Colorado originate in high, mountain-
ous sections of Utali, Colorado, "Wyoming, Arizona, New Mexico, and
Nevada. These waters flow, with few significant additions, through the
semi-arid parts of these states, eroding soft plateaus and old hike
deposits rapidly. Wherever hard, mountainous sections are traversed,
the river has cut narrow, straight-sided canyons. It is in such a canyon
that Boulder Dam is located. The size, structure, and uses of this dam
are familiar to everyone, so further description in this report is not
necessary. It is important to note, however, that the lake formed by
this dam acts as a depository for the silt load of the river. Water dis-
charged from the dam is free of the silt eroded from the 167,000 square
miles of the river's drainage above the dam. It is because of this fad
and because the water leaving the dam is drained from a stratum far
beneath the surface of Lake Mead, that the 25 to 30 miles of the Colo-
rado immediately below the dam are important in fishery interests.

Trout Water Below Boulder Dam

Physical Features

Coincident with the operation of power generators and flood con-
trol functions at Boulder Dam, water can be released from Lake Mead
at three levels: (1) the surface spillways, (2) the 1,050-foot level, and
(3) the 900-foot level. The 1,050-foot level is about 120 to 170 feet,
and the 900-foot level about 270 to 320 feet, beneath the surface of the
reservoir, depending on the level of the water surface.

Discharged water from the lower levels is cold. During 1940 and
1941, it ranged in temperature between 54° and 57° F. at the 900-foot
level, and between 55° and 61° F. at the 1,050-foot level.

80 -




50 -




Daily Records At 8O0AM.

Ave. Monthly Temperature

- Hiqhest For Month
Lowest For Month


O .



D, M


D, M






Fig. 23. The average monthly, as well as the maximum and minimum water tem-
peratures of the Colorado River near Willow Beach, Arizona, for each month

timing the years 1936 to 1941, inclusive.

River temperatures 10 miles below the dam are shown in Figure
23. This gives the average monthly, as well as the maximum and mini-
mum, water temperatures for each month during the years 1936 to 1941,
inclusive. The data on which this graph is based were furnished by the
U. S. Geological Survey which maintains a gaging station just upstream
from Willow Beach, Arizona. These temperatures did not fluctuate
over one or two degrees Fahrenheit winter or summer during the years



1939 and 1940. However, during August-November, 1941, discharge
of water over the Arizona spillway raised the average temperature to
61-69. 5° F. at Willow Beach. The highest recorded water temperature
during August, 1941, was 77°. Should such a spillway discharge
reach the river during midsummer, resulting high temperatures might
be disastrous to trout. It is very unlikely that any further spillway
discharge will be made.

On October 31, 1941, the water temperature at Eldorado Canyon
was 67° F. (Temperature of discharge water at the dam was 64° F.)
The temperature at Eldorado is within the trout range, but on the high
side. Air temperature at the same time was around 73-79° F. Summer
air temperatures rise to 110-126° F. in this region, and it is believed
their effect on the river might be great enough to raise the water tem-
perature above the tolerable range for trout.

Because of the fairly constant low temperature and clarity of the
water released from Boulder Dam, the river below this point for a
distance of approximately 25 miles has been transformed into good
trout water. The downstream extremity of trout water is arbitrarily
placed at Eldorado Canyon, although conditions suitable for trout may
extend below this point during most of the year. Some good trout
catches have been reported from below this limit, but they are usually
made during the cooler winter months.

Setting of Eldorado Canyon as the lower limit of trout water to oe
managed is supported by the general topography of the river at that
point. The river basin spreads. It contains many extensive silt bars
which are whipped into suspension by the current, increasing the
turbidity of the water considerably. Fish food production is curtailed
by silt deposits and high turbidities. Undoubtedly, some trout produc-
tion will continue below Eldorado, but most attention should be focused
on the river above that point.

At the time of this study, water volumes ranging between 27,000
and 35,000 cubic feet per second were flowing down this stretch of
river. (Fig. 24.) Consequently the river was considerably higher
than it was during October, 1940, when visited by Madsen 3 who


Discharge III Of
Each Month



Fig. 24. Surface elevation changes on Lake Mead. Maximum and minimum dis-
charges in cubic feet per second from Bouldi-.r Dam during the years 1935 to
1940, inclusive. During 1941, only the discharge at the first of each month is

3 Madsen, Dave, 1940 — A typewritten letter report of a visit to Colorado River,
October 1-6, 19 40. Submitted to the Division of Fishery Biology, Washington, D. C,
October 9, 1940.



reported a flow of 4,000-12,000 cubic feet per second. Assuming a
normal flow of 20,000 cubic feet per second, it is estimated that the
river averages about 500 feet in width. Using this figure, there are
approximately 1,600 acres of trout water in this section of the river.

Fig. 25. A downstream view of the Colorado River from the east side of the
canyon showing Ringbolt Rapids and a characteristic side-stream delta
encroaching- on the river from a wash.

Colorado River below Boulder Dam has a gradient of about 3 feet
per mile. This slope is not exceptionally steep, but considering the
large volume of water usually flowing, the work of the river is great.
Furthermore, the fall is not uniform. There may be descents of 3 to
6 feet over rapids within a linear distance of \ mile (Fig. 25). Quiet
water stretches may have a gradient of but 1 or 2 feet per mile. The
rate of flow averages about 4 miles per hour.

Two large rapids, one named Ringbolt (so called because ring bolts
set in the sides of the canyon were used to anchor cables on which
freight boats were hauled over the rapids by early settlers), and
another, unnamed, occur in the river between the dam and Eldorado.
Numerous smaller rapids and long riffles are spaced along the entire
river course.

In most of the riffles and many quieter parts of the stream, exten-
sive gravel shoals are clearly visible at water depths of 15 to 20 feet.
Practically all such shoals and riffles are covered by an almost con-
tinuous blanket of green algae. Because the water is so exceptionally
clear, aquatic plant production is encouraged in practically all of the
river bed, providing that other conditions are favorable.

The Colorado below Boulder Dam is quite inaccessible to modern
vehicles. Sheer walls of rock rise 400 to 500 feet on both sides of the



liver and are penetrated only by occasional dry washes, a few of which
are extensive enough to reach the plateau above the river. In two of
these washes on the Arizona side temporary roads of poor quality lead
to the river. One is at Ringbolt Rapids, about 4 miles below the dam,
and the other at Willow Beach 10 miles below the dam. There is no
road to the river on the Nevada side except at Eldorado Canyon. All
roads leading to the river are subject to washout without notice. Flash
floods of remarkable velocity and volume may strike washes along the
river any time during the summer.

Boating on the river is dangerous, especially in light, poorly
powered craft. The two large rapids just mentioned are not negotiable
upstream except by boats having at least 10-horsepower motors. Even
then, a fair amount of experience is necessary to avoid trouble. There
is one boat livery and dock at Willow Beach, Arizona. Most fishing is
done up and down stream from this point. Waters outside the imme-
diate vicinity of Willow Beach have to be fished by boat. It is impos-
sible to walk up or down the river because of sheer walls (Fig. 26).


Fig. 26. An upstream view of the Colorado River showing the ruggedness and

inaccessibility of its canyon.

Climatic conditions of this region are not conducive to soil forma-
tion in the drainage area of the river. Very little really productive soil
occurs in the entire Colorado River drainage except in its mountainous
extremities. Such a lack of organic matter has an adverse effect on
fish food production. However, this is of greater importance in Mead
Lake than in the river. Enough organic matter is in the water to fill
the needs of river vegetation but many areas where silt and debris


collect would be much more productive were the silt not so inert. Con-
tinuous plant growth in the river should gradually alter the composi-
tion of the silt until it reaches a state of production.

Chemical Features

The chemical nature of Colorado River water below Boulder Dam
is not detrimental to biological productivity. An abundance of oxygen
is stirred into the water as it leaves the dam. Many forms of powerful
and often spectacular turbulence aerate the water thoroughly as it
emerges from the various outlets of the dam. Rapids, riffles, and con-
stant swirling maintain the oxygen content of the water as it progresses
downstream. On October 31, 1941, the oxygen content of the water at
Willow Beach was 9.3 parts per million. The river was highly alkaline.
Tests for pH (hydrogen-ion concentration) made on the same date were
constant at 8.2. No carbon-dioxide was found in the water. Dissolved
carbonates and bicarbonates were present in concentrations of 121 parts
per million. Total dissolved solids were much greater in concentration
than the carbonates and bicarbonates. Leo Dunbar, of the U. S. Bureau
of Reclamation, reports a concentration of 650 parts per million. Most
of these dissolved solids are sulfates of calcium (gypsum), magnesium
(epsom salts) and sodium. Sodium chloride is present in small
amounts. Salt beds are exposed in several localities in Lake Mead.
Calcium salts predominate, originating from great deposits of gypsum
exposed in Lake Mead. These deposits are dissolved slowly and are
transported down river.

Biological Features

There are very few aquatic plants, with the exception of algae, in
the Colorado River. A few sprigs of water-weed (Anacharis sp.) were
found in stomach contents of trout. None was located while cruising
the river. Some reeds (Phragmites) , cattails (Typha) and bulrushes
Scirpus) occur in quiet water. As stated previously, almost the entire
bottom of the river is covered by a blanket of algae wherever riffles and
grave] bars exist. Fronds of this plant pend downstream from practi-
cally .'very rock. The main algal component is a species of Cladophora.
Other species of green and blue-green algae are present, but they are
not as abundant as Cladophora.

The roots of many shore plants such as Cottonwood trees, tamarisk
and willows project into the river. Wherever o- od stands of these
plants exist, excellent cover for fish is formed by the thick maze of roots
washed \'voo of the banks. Typical desert vegetation is sparsely dis-
tributed over the higher lauds of the river valley. The occurrence of
these terrestrial plants is important because the insects inhabiting them
are a potential food supply for fish.

Very little could be done to obtain quantitative bottom samples.
The water was so high that regular apparatus could not be handled
effectively. It was ascertained that sandy portions of the river bottom
are quite barren. Repeated sampling with an Ekman dredge yielded no
organisms retainable in a screen with 30 meshes to the inch. Practi-
cally all the food organisms inhabited the riffles and especially the algae
growing there. Mayfly nymphs, chiefly Callibaetis, were abundant;
stonefly nymphs occurred rarely; midge larvae and pupae were very


common. Microcaddis larvae and pupae were present in practically
every alga] sample examined. Some aquatic beetles were found in
stomachs of trout. Many smaller organisms were present in abundance.
Several species of Daplniia and Diaptomns occurred in swarms among
the algal filaments and also sparingly in the water. Protozoa of sev-
eral kinds were undoubtedly present in the algal masses but no exam-
ination was made for them.

During April of 1041. 100,000 fresh-water shrimp were planted in
the river upstream from Willow Beach. Observations in that vicinity
failed to reveal any shrimp in November, 1941. No shrimp were found
in stomachs of trout taken around Willow Beach. These findings do
not mean that the planting was a failure as high water hampered a
thorough search for these organisms.

Fish collected or observed by the author while located on the
Colorado below Boulder Dam are listed below:

Rainbow Trout, Salmo gairdnerii Richardson

Large-mouthed Bass, Hvro salmoides (Lacepcde)

Carp, Cyprinus carpio L.

Bony Tail, Gila elegans Baird & Girard

Humpback Sucker, Xyrauchen texanus (Lookington)

Channel Catfish, Ictalurus punctatus (Rafinesque)

Colorado "White Salmon," Ptychocheilus htciits Girard

It is very probable that other species are present in the river.
More collecting should be done at a time when the water is low and a
seine can be operated successfully. The rainbow trout, large-mouthed
bass, carp and channel catfish are introduced species. Rainbow trout
were placed in the Colorado in November, 1935, following changes made
in the character of the river by Boulder Dam. These fish are more or
less isolated in a desert environment by physical barriers. The dam
cannot be traversed by fish attempting to move upstream and thermal
conditions prohibit extensive downstream migration. Because the trout
are more or less confined, this area would be ideal for population, yield
and growth studies.

The growing season in the trout water area of the Colorado under
discussion, is exceptionally long. Temperatures are not variable, the
sun shines almost every day and food production is maintained
throughout the year. Insect life cycles are continuous. There is no
long period of inclemency which inhibits activities of adult insects.
Algal production is uniform through the year. Although it is not yet
certain, one might surmise, and with much justification, that the trout
groAvth is also continuous. This assumption is supported by observa-
tions made on the scales of trout taken from the river. Thirty-seven
specimens ranging between 9\ and 17-J inches in total length were
examined. Many of the fish were not weighed because they were
cleaned by fishermen before being brought to the dock. However, 6
fish between 10 and 11 inches in length averaged 7.4 ounces in weight.
These fish had an average coefficient of condition 4 of 1.09 as based on

4 The coefficient of condition of a fish is a measure of its plumpness in relation
to its length. It is determined by taking the weight in pounds or grams multiplied
by 100,000 and divided by the cube of the length in inches or centimeters.

Standard length is the distance from the tip of a fish's snout to the end of its
vertebral column. Total length is the over-all length of the fish.


total length in centimeters rather than standard length. Three fish
between 11 and 12 inches in total Length averaged 8.2 ounces in weight.
Their coefficient of condition was 1.00. One troul 13} inches long,
weighed 13.5 ounces and had a coefficient of coin I it inn of 1.01. Five
fish between 14 and 15 inches total length averaged 1 pound, 0.8 ounces
in weight. Their average coefficient of condition was 1.00. One fish,

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