FISH->GAME
California Fish and Game is a journal devoted to the conservation and
understanding of v/ildlife. If its contents are reproduced elsewhere, the authors
and the California Department of Fish and Game would appreciate being
acknowledged.
Subscriptions may be obtained at the rate of $10 peryear by placing an order
with the California Department of Fish and Game, 1416 Ninth Street,
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Complimentary subscriptions are granted on an exchange basis.
Please direct correspondence to:
Perry L Herrgesell, Ph.D., Editor
California Fish and Game
1416 Ninth Street
Sacramento, CA 95814
u
D
VOLUME 71
OCTOBER 1985
NUMBER 4
Published Quarterly by
STATE OF CALIFORNIA
THE RESOURCES AGENCY
DEPARTMENT OF FISH AND GAME
—LDA—
194 CALIFORNIA FISH AND CAME
STATE OF CALIFORNIA
GEORGE DEUKMEJIAN, Governor
THE RESOURCES AGENCY
GORDON VAN VLECK, Secretary for Resources
FISH AND GAME COMMISSION
WILLIAM A. BURKE, Ed.D., President
Brentwood
BRIAN J. KAHN, Vice President ABEL 0. GALLETTI, Member
Santa Rosa Los Angeles
ROBERT BRYANT, Member ALBERT C. lAUCHER, Member
Yuba City Long Beach
DEPARTMENT OF FISH AND GAME
JACK C. PARNELL, Director
1416 9th Street
Sacramento 95814
CALIFORNIA FISH AND GAME
Editorial Staff
Editorial staff for tfiis issue consisted of the following:
Wildlife William E. Grenfell, Jr.
Inland Fisheries Jack Hanson
Marine Resources Robert N. Lea, Ph.D.
Environmental Services Kim McCleneghan, Ph.D.
Editor-in-Chief Perry L. Herrgesell, Ph.D.
CONTENTS
195
Page
Temporal Distribution of Breeding and Non-Breeding Canada
Geese From Northeastern California Warren C. Rienecker 196
The Occurrence, Seasonal Distribution, and Reproductive
Condition of Elasmobranch Fishes in Elkhorn Slough, Cali-
fornia Larry G. Talent 210
Effects on Wildlife of Ethyl and Methyl Parathion Applied to
California Rice Fields Thomas W. Custer,
Elwood F. Hill and Harry M. Ohiendorf 220
Population Biology of Bluegills, Lepomis macrochirus, in Lotic
Habitats on the Irrigated San Joaquin Valley Floor
Michael K. Saiki and Christopher J. Schmitt 225
NOTES 245
An Observation of Reproductive Bahavior in a Wild Popula-
tion of African Clawed Frogs, Xenopus laevis, In
California Michael J. McCoid 245
Parasites of The Sacramento Perch, Archoplites interruptus
Cay C. Goude and C. David Vanicek 246
Book Reviews 251
Index to Volume 71 252
NOTICE OF FEE INCREASE
After 70 years of publication, it has become necessary to change the fee
structure that supports California Fish and Game. Beginning with the Janu-
ary 1986 issue the individual subscription fee will be increased from $5 to
$10 per year. Libraries and institutions providing exchange material to The
California Department of Fish and Game will continue receiving the jour-
nal on a complimentary basis; those that do not will be charged the
increased rate. Additionally, $35 per page will be charged to authors or
their institutions. These charges will be assessed on all manuscripts submit-
ted after January 1, 1986. Authors will be billed upon receiving galley
proofs for review. Finally, authors will be charged for all reprints. A reprint
fee schedule will be provided with the transmittal of galley proof.
The editorial staff does not believe that these charges are high enough to
preclude the ability of prospective authors to publish in the journal or of
subscribers to obtain it. This income will ensure the continuation and
enhancement of the professional reputation the journal currently enjoys.
196 CALIFORNIA FISH AND CAME
Calif. Fish and Game 7M4): ]9f,-209 1985
TEMPORAL DISTRIBUTION OF BREEDING AND '
NON-BREEDING CANADA GEESE FROM
NORTHEASTERN CALIFORNIA ^
WARREN C. RIENECKER
California Department of Fish and Game ,
Waterfowl Studies Project
1022 Celestial Way
Yuba City, California 95991
During June 1979, red neck collars with individual codes were placed on 999
western Canada geese, Branta candensis moffitti, on three molting areas (Goose
Lake, Telephone Flat Reservoir, and Meiss Lake) and two nesting areas (Tule Lake
NWR and Beeler Reservoir) in northeastern California. During the 4-yr study period,
538 collar sightings from 319 individuals were made and 179 collared geese were
reported shot. Fifty-nine percent of marked geese were seen only once compared
to 1% seen six times. Most sightings were made on the breeding and wintering
grounds of northeastern California (51%) and wintering grounds on municipal water
district reservoirs in counties surrounding San Francisco Bay (43%). San Pablo Dam
Reservoir is the wintering area most used by Goose Lake and Telephone Flat Reser-
voir geese. Goose Lake and Telephone Flat Reservoir geese utilized some of the same
reservoirs in the Bay Area, but did so in different proportions. The reservoirs are
closed to hunting and consequently geese wintering there have less hunting pressure
compared to those remaining in northeastern California. Meiss Lake and Tule Lake
flocks were semi-resident and seldom left northeastern California. Tule Lake geese
sustained a greater harvest than geese from the three molting areas. Some one- and
two-yr old geese made a molt migration to the Northwest Territories. A few geese
wintered as far south as the San Joaquin Valley where they overlapped with the
Rocky Mountain population.
INTRODUCTION
The western Canada goose of the Pacific Flyway currently is regarded as
consisting of two main populations, the Pacific and the Rocky Mountain (Krohn
and Bizeau 1980). The Pacific population is comprised of five subpopulations,
one of which includes northeastern California along with southeastern Oregon
and northwestern Nevada. California Department of Fish and Came and U.S.
Fish and Wildlife Service biologists estimate the average population size of
Canada geese breeding in California at approximately 20,(XX).
During 10 days in mid-June 1979, 999 Canada geese were marked with red
neck collars on the breeding grounds of northeastern California. Each collar was
inscribed with a black letter "k" and three black digits oriented vertically and
repeated four times. Raveling (1978) suggested and Krohn and Bizeau (1980)
concurred that serious consideration be given to exchanging routine agency
banding programs for color marking programs and to the assignment of a biolo-
gist to "live" with each population subunit of interest to obtain consistency in
records of marked individuals. Use of collars has generally been acknowledged
as the best technique for studying geese.
Objectives of the study were to ( i ) relate nesting areas of northeastern Califor-
nia with molting areas, ( ii ) to relate breeding areas with wintering areas, and ( iii )
to locate the boundary in the Central Valley of California between the wintering
areas of the Pacific and Rocky Mountain populations of Canada geese.
' Accepted for publication January 1985.
TEMPORAL DISTRIBUTION OF CANADA GEESE
197
METHODS
Flightless geese were captured by herding with boats into a corral-type trap
set on shore. Usually, the goose drive started 3-13 km from the trap site and
covered a wide area. The operation was directed by airplane with radio conri-
munication to boats. About 1 5 persons were recruited from California Depart-
ment of Fish and Game, U.S. Fish and Wildlife Service, U.S. Forest Service, and
University of California-Davis to trap and collar geese.
The plan was to collar 500 geese on nesting areas of Tule Lake NWR and
Beeler Reservoir and 500 on molting areas of Goose Lake, Telephone Flat Reser-
voir and Meiss Lake (Figure 1 ). However, fewer geese were caught on nesting
areas than expected, so more geese were collared on the molting areas.
(Table!).
Meiss Lake
Tule Lake
Goose Lake
Telephone Flat Res.
Beeler Res.
Stafford Res
San Poblo Dam Res
Briones Res.
Calaveras Res
Upper San Leandro Res
FIGURE 1. Locations of banding sites of Canada geese in northeastern California and wintering
areas of Canada geese in the San Francisco Bay Area.
r
198 CALIFORNIA FISH AND GAME
TABLE 1. Number of Canada Geese Collared in Northeastern California, June 1979, and
Number Subsequently Sighted or Shot.
Collared Individuals Number Number
Collaring Site Adult Local Total sighted (%) sightings" shot^
Goose Lake 300 - 300 85(28) 136 51
Telephone Flat Res 323 - 323 124(38) 211 55 v
MeissLake 150 - 150 18(12) 25 20
Beeler Res 10 17 27 7(26) 16 5
TuleLakeNWR jO? _?2 i^ 85(43) 150 48
Total 892 107 999 319 538 179
° Some individuals sighted several times.
'■As of January 31, 1983.
In the first year after trapping (October 1979-May 1980), all known and
potential goose areas in California fronn Merced County (see Figure 1) north
were searched at least once for collared geese (Table 2).
TABLE 2. Distribution by Days of Effort Expended in Searching for Neck-banded Canada
Geese in California, 1979-82.*
MONTH
Location S O N D J F M A M J J A Total
Klamath Basin
1979 9 7 16
1980 2 2 2 7 7 20
1981 7 5 1 1 3 17
1982 112 2 2 8
Northeastern Calif.
1979
1980 3 9 1 13
1981 6 6
1982 1 9 10
Shasta and Scott Valleys
1979 1 1
1980 2 4 .6
1981 2 2
1982
Sacramento Valley
1979 2 5 4 11
1980 11 2
1981 1 1
1982 3 1 4
San Francisco Bay Area
1979 4 4
1980 5 11 2 18
1981 4 4 8
1982 4 . '; 4-;
North San Joaquin Valley ''"
1979 16 . '16'
1980 13 26 24 5 ■ 68^
1981 1 11 18 16 3 49
1982 1 13 34 24 16 88
Warner Valley, Oregon
1980 2 2
* Includes sightings from all major contributors
■•" Major portion of observation time was made by Aleutian Canada goose observation team while searching for
Aleutian geese.
TEMPORAL DISTRIBUTION OF CANADA GEESE 199
RESULTS AND DISCUSSION
Between October 1979 and March 1983, 538 collar sightings were made from
319 individually marked geese. During the same time, 179 collared geese were
reported shot (Table 1 ). Forty-one percent of the sightings were made the first
year, 34% the second year and 21% during the third year. Although no search
effort was made, 4% were seen in the fourth year. Fifty-nine percent of the geese
sighted were seen only once during the study (Table 3). Forty-six percent were
seen at least once and/or shot. Eighty percent of the shot geese were never seen
alive after collaring.
TABLE 3. Sightings Per Individual Collared Canada Goose in California, 1979-82.
Sightings Percent
1 59
2 21
3 11
4 6
5 2
6 1
100
Although much of the northern half of California was searched for marked
geese the first year, most of the observations of the 319 marked geese were made
on the breeding and wintering grounds of northeastern California (51%) and on
the wintering grounds in the San Francisco Bay Area (41%).
Whereas the number of sightings per area can be regarded as somewhat
representative of the distribution of the population, it mainly indicates where
emphasis was placed in searching for collars (Table 2). For example, more hours
of searching were spent in the Klamath Basin throughout spring, summer and fall
compared to the relatively short time spent searching in the San Francisco Bay
Area during winter, yet 43% of the 538 sightings came from the Bay Area
compared to 38% from the Klamath Basin. However, the number of geese
collared on each of the five banding areas has an influence on these percentages.
For example, approximately two-thirds (623) of the 999 geese marked were
from Goose Lake and Telephone Flat Reservoir, and the Bay Area is the main
wintering ground for these birds. The fact that less than one-half of the collared
geese were observed in the field is assumed to be the result of limited time
available for searching for marked geese.
San Francisco Bay Area
Leg band recoveries indicate that most geese migrating south from northeast-
ern California disperse throughout the Sacramento Valley (W. Rienecker, Calif.
Dept. Fish and Game, unpubl. rep.). However, this is only indicated from
harvested geese. The majority of collars sighted during the winter were seen on
municipal water district reservoirs in counties surrounding San Francisco Bay.
These reservoirs are closed to hunting and therefore not sampled by hunter kill.
The importance of these reservoirs as a wintering area for northeastern California
Canada geese was not well known prior to this study.
Collar sightings supported by leg band recovery data (W. Rienecker, Calif.
Dept. Fish and Game, unpubl. rep.) suggest that geese from all five collar areas
could conceivably be found on one reservoir at some time during winter, but
200 CALIFORNIA FISH AND GAME
not necessarily at the same time. Although some geese were seen more than
once on an area, suggesting they might have stayed there for the winter, others
were seen only once suggesting that some geese are more mobile, or that
sightings were not made at the final destination of the wintering grounds.
Although geese collared at Goose Lake and Telephone Flat Reservoir utilized
some of the same reservoirs in the San Francisco Bay Area, they did so in
different proportions (Table 4). For example, 66% of the Telephone Flat Reser-
voir geese were seen at San Pablo Dam Reservoir, and 27% at Upper San
Leandro Reservoir; compared to 38% and 13% respectively, for geese marked
at Goose Lake.
It was common to see a Telephone Flat Reservoir goose on San Pablo Dam
Reservoir one winter, and again a few weeks later or the following year on Upper
San Leandro Reservoir, 45 km apart. This suggests that a preferred wintering area
might encompass two or more water areas, possibly due to feed conditions or
harassment.
For Goose Lake and Telephone Flat Reservoir geese, the San Francisco Bay
Area is the most important wintering area south of northeastern California. San
Pablo Dam Reservoir appears to have the greatest goose use. Once having
reached 2 years of age, most Canada geese continued to return to their tradi-
tional roost sites in subsequent years (Raveling 1979). Crissey (1968) stated that
during the migration and wintering periods about all that Canada geese seem to
require is a pond of water five or more acres in size, free from disturbance and
surrounded by agricultural land where birds can either graze or feed on waste
grain. San Francisco Bay Area reservoirs meet these requirements. Each reservoir
is at least several hundred acres with ample grazing on surrounding hillsides.
These reservoirs are closed to hunting and have restricted public use which is,
no doubt, an added attraction to geese. Rienecker's study on Canada geese
leg-banded in northeastern California (Calif. Dept. Fish and Game, unpubl. rep.)
indicate nonbreeding geese banded on the molting areas of Goose Lake and
Clear Lake had a lower band recovery rate than breeding adults banded on the
nesting grounds. He assumed this discrepancy was caused by nonbreeders
inhabiting areas with less hunting pressure than areas occupied by breeders.
These data suggest that the San Francisco Bay Area reservoirs are the areas of
less hunting pressure. Raveling (1978) indicated that a breeding population can
show expansion because of favorable survival of a large subunit while other
subunits are unknowingly being extirpated.
Relationship Between Nesting and Molting Areas
Goose Lake
Prior to this study, the assumption was that some molters on Goose Lake came
from nesting areas in Oregon (e.g. the Warner Valley), but the absence of collar
sightings from Oregon suggest these geese are not generally found north of
Goose Lake (Table 5). Retrap data (W. Rienecker, Calif. Dept. Fish and Game,
unpubl. rep.) from leg-banded geese and the lack of collar sightings in Surprise
Valley, California also suggest they do not come from nesting areas east of Goose
Lake. All sightings during the breeding period were from the south and southwest
of Goose Lake along the Pit River drainage as far as Big Valley, and from the
reservoirs to the west in the Devil's Garden of Modoc National Forest. Spring
sightings on the Modoc NWR, south of Goose Lake, were dominated by Goose
Lake birds.
TEMPORAL DISTRIBUTION OF CANADA GEESE
201
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Telephone Flat Reservoir
Geese from Telephone Flat Reservoir were distributed in a pattern similar to
those of Goose Lake but tended more towards the southwest in the direction
of Big Valley (Table 6) . Some sightings were made as far west as Tule Lake. Five
of the 29 sightings of Telephone Flat Reservoir geese made at Tule Lake were
recorded during the breeding season.
Meiss Lake
The few sightings made of Meiss Lake birds suggest their nesting areas are
located southwest in Shasta and Scott valleys, east to the west side of Lower
Klamath NWR, and north to the Klamath Wildlife Area near Klamath Falls,
Oregon (Table 7).
Beeler Reservoir
Geese collared on the nesting area of Beeler Reservoir were not found nesting
elsewhere. Generally, Beeler Reservoir geese move by late September. Data
suggest that some move north to the Klamath Basin in late summer and are apt
to stay there until the following breeding season. Others stay in northeastern
California until late fall, then move down to the San Francisco Bay Area for the
winter (Table 8). Retrapdata (W. Rienecker, Calif. Fish and Game, unpubl. rep.)
suggest that the non-breeders molt on Clear Lake, 32 km northeast of Beeler
Reservoir.
Tule Lake
Tule Lake NWR collared geese were not observed nesting on other areas. For
example, although the Lower Klamath NWR is located less than 9.5 km west of
Tule Lake, no Tule Lake collared geese were seen nesting there.
The relatively few sightings of Tule Lake geese outside of the Klamath Basin
(Table 9) suggest this flock is also semi-resident. Clear Lake, 23 km east of Tule
Lake, is the main molting area for these geese; however, each year a segment
of non-breeders from this flock migrate to the Northwest Territories to molt ( W.
Rienecker, Calif. Dept. Fish and Game, unpubl. rep.). The one collar sighted and
two collared geese shot in Alberta from the Tule Lake birds (Table 9), plus one
shot from the Telephone Flat Reservoir geese were assumed to be returning from
the Northwest Territories to California. Sterling and Dzubin (1967) documented
molt migration of B. c. maxima and B. c. moffitti Uorr\ their midcontinent breed-
ing ranges to the subarctic tundras of the Northwest Territories. Molt migrations
have since been documented for the Pacific Canada goose in Oregon ( McLaury,
Malheur NWR, unpubl. rep.) and Washington (Hanson and Eberhardt 1971 ) in
addition to California (W. Rienecker, Calif. Dept. Fish and Game, unpubl. rep.).
Rienecker (Calif. Dept. Fish and Game, unpubl. rep.) indicated that, accord-
ing to the breeding ground surveys over the past 20 years, the Klamath Basin
Canada goose flock has been in a downward trend, whereas in the remainder
of northeastern California, the population has been increasing. He suggested
several possibilities for this decline, one of which was overharvest to the point
of reducing the breeding population. Although there were no statistically signifi-
cant differences (X^ = 1.2, P < .05) between molting areas in number of geese
shot, there was a difference (X^ — 3.04, P < .10) between molting areas and
the Tule Lake nesting area. Tule Lake adult geese sustained a greater harvest than
geese from the three molting areas.
204
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208 CALIFORNIA FISH AND CAME
Fall and Winter Movements
There is some uncertainty how nnuch time the various flocks of the northeast-
ern California subpopulation spend on wintering grounds away from the
northeastern part of the State. Generally, the first collared geese seen in the San
Francisco Bay Area were during the first week in November and the last collar
in the second week of February. However, it is suspected that many geese do
not migrate as far south as the Bay Area or, if they do, they stay for only a short
period of time. Ray Johnson (Klamath Wildl. Area, pers. comm.) stated that
geese on his area in the Klamath Basin do not leave for much more than two
weeks during winter. A rancher in Fall River Valley stated (pers. comm.) that
geese leave the valley only when snow covers their food supply, but return when
food is available. This is not a heavy snow area, consequently, food is available
most of the winter. However, collar slightings suggest that many nonbreeders
and unsuccessful breeders from Goose Lake and Telephone Flat Reservoir move
down to central California, especially the San Francisco Bay Area, in the fall and
remain there most of the winter.
The distance between breeding area and winter area for Meiss Lake geese is
short to nonexistent as compared to the distance traveled by Goose Lake and
Telephone Flat Reservoir geese. Few winter south of Shasta Valley suggesting
they are more resident than geese on Goose Lake and Telephone Flat Reservoir.
Although the sample was small, Beeler Reservoir geese seem to follow the
same pattern as those of Goose Lake and Telephone Flat Reservoir. Six of 17
collared Beeler Reservoir birds were sighted or shot outside northeastern Califor-
nia. The Tule Lake birds, being semiresident, generally leave only if forced out
by adverse weather conditions.
Leg band recoveries suggest that the boundary in California between wintering
flocks of the Rocky Mountain population and the Pacific population is in the
northern San Joaquin Valley. It was thought that the collaring program would be
more specific for location of this dividing line between the two populations.
However, it appears that very few collared geese wintered in the San Joaquin
Valley and there is a gradual thinning out and overlap of the population as they
approach the outer limits of their wintering areas.
Problems Associated With Color Marking
The poor color combination of black on red combined with a vertical code
of four symbols (letter K and 3 digits) was a distinct hindrance to this study. The
code was unnecessarily long and thus too small to be easily read with the
average 20-45 power scope. The poor color contrast and small code size on
days with poor light conditions and distant geese often resulted in unread codes.
Those people that saw geese with collars, but who were not actively searching
for collars, were able to read only 36% (62) of the codes on collars. Personnel
on this study, however, were equipped with the higher powered Questar scope
which improved the success ratio to 73% (474). The Questar was necessary
most of the time, but not all codes were read without difficulty. A great deal of
time was wasted attempting to read distant collars. Had the codes been larger
and more easily read, more time could have been spent searching for other
collared geese.
TEMPORAL DISTRIBUTION OF CANADA GEESE 209
ACKNOWLEDGMENTS
I wish to thank B. Deuel for his assistance on the project, and also C. Ely, J.
Johnson and members of the Aleutian Canada goose observation team for
recording collar sightings. Appreciation is also extended to D. Raveling and D.
Connelly for their critical reviews of this manuscript. Finally, I thank the many
people who helped with trapping and collaring. This work was performed as part
of Pittman-Robertson Project W-30-R "Waterfowl Studies" supported by Fed-
eral Aid to Wildlife Restoration funds.
LITERATURE CITED
Crissey, W. F. 1968. Informational needs for Canada goose management programs. Pages 141-147 in R. L. Hine
and C. Schoenfeld, eds. Canada goose management. Dembar Educational Research Services, Inc. Madison,
Wisconsin.
Hanson, W. C, and L. L. Eberhardt. 1971 . A Columbia River Canada goose population, 1950-1970. Wildl. Monogr.,
28. 61 pp.
Krohn, W. B. and E. C. Bizeau. 1980. Rockly Mountain population of the western Canada goose; its distribution,
habitats, and management. U. S. Fish Wildl. Serv., Spec. Sci. Rep. — Wildl. 229. 93 pp.
Raveling, D. G. 1978. Dynamics of distribution of Canada geese in winter. Trans. North Am. Wildl. Nat. Res. Conf.
43: 206-225.
1979. Traditional use of migration and winter roost sites by Canada geese. ). Wildl. Manage., 43(1 ):
229-235.
Sterling, T. and A. Dzubin. 1967. Canada goose migrations to the Northwest Territories. Trans. North Am. Wildl.
Nat. Res. Conf. 31: 355-373.
210 CALIFORNIA FISH AND GAME
Calif. Fish and Game 71 (4): 210-219 1985
THE OCCURRENCE, SEASONAL DISTRIBUTION, AND
REPRODUCTIVE CONDITION OF ELASMOBRANCH
FISHES IN ELKHORN SLOUGH, CALIFORNIA ^
LARRY G. TALENT ^
Moss Landing Marine Laboratories,
Moss Landing, CA 95039
The occurrence, seasonal distribution, and reproductive condition of elasmo-
branch fishes were studied in Elkhorn Slough, a shallow estuary near Moss Landing,
California, from 1 October 1971 through September 1972. Seven species of elasmo-
branch fishes were captured. In order of abundance they were: leopard shark, Triakis
semifasciata; bat ray, Myliobatis californica; gray smoothhound, Mustelus califor-
nicus; round stingray, Urolophus halleri; shovelnose guitarfish, Rhinobatos produc-
tus; brown smoothhound, Mustelus henlei; and thornback, Platyrhinoidis triseriata.
Leopard sharks and bat rays were commonly captured in Elkhorn Slough throughout
the entire year. Gray smoothhounds, round stingrays, shovelnose guitarfish, and
brown smoothhounds were only seasonally common at the study site. Thornbacks
were rare at the study site during all seasons. Of the elasmobranch fishes captured
in Elkhorn Slough, leopard sharks and bat rays were apparently the only species that
regularly gave birth to young in the slough.
INTRODUCTION
Little is known about the seasonal distribution or reproductive biology of
elasmobranch fishes along the California Coast. Moreover, the data available on
most species are insufficient to even determine if populations are sedentary or
migratory. The only published reports on the occurrence and reproductive
condition of elasmobranchs in Elkhorn Slough, an estuary in central California,
are based on results of annual shark derbies usually held during the months of
May and June (Herald and Dempster 1952, Herald 1953, Herald et al. 1960).
There are no published reports on the occurrence or reproductive condition of
elasmobranchs in Elkhorn Slough during other parts of the year.
There is a need to evaluate the importance of estuaries to the life histories of
elasmobranch fishes because these areas are being rapidly lost worldwide due
to industrial development. In particular, the value of Elkhorn Slough to elasmo-
branch fishes must be determined because it is possible that parts of the slough
will be developed for industrial and recreational purposes in the future.
The objectives of this paper are to describe the elasmobranch fishes captured
in Elkhorn Slough, to present information on their seasonal distribution in the
study area, and to describe the reproductive condition of female elasmobranchs
captured during the project.
MATERIALS AND METHODS
This study was conducted in Elkhorn Slough (Figure 1), a shallow estuary,
located on the east side of Monterey Bay near Moss Landing, California. Elkhorn
Slough consists of about 1000 ha of submerged areas, tidal flats and salt marsh.
The slough has a maximum depth of approximately 4 to 5 meters and is charac-
terized by extensive mudflats that are periodically exposed during low tide and
' Accepted for publication March 1985.
^ Dr. Talent's present address is: Department of Zoology, Oklahoma State University, Stillwater, OK 74078.
ELASMOBRANCHS IN ELKHORN SLOUGH
211
inundated during high tide. A more detailed description of the study area was
presented by Talent (1976); Browning (1972) provided a thorough description
of Elkhorn Slough and the surrounding area.
FIGURE 1. Map of Elkhorn Slough showing the study site.
Results of this paper are based on elasmobranch fishes collected from 1
October 1971 through September 1972. Elasmobranchs were collected at least
monthly with two 90-m nylon gill nets that contained longitudinal sections of
10.2, 15.2, and 22.9-cm stretch mesh, 30 m each. Mesh sizes smaller than
10.2-cm stretch were not used in order to minimize the capture of large numbers
of bony fishes. All gill net sets were on the bottom, 2.4 km from the mouth of
Elkhorn Slough (Figure 1).
212 CALIFORNIA FISH AND GAME
Gill nets were set perpendicular to water flow in the slough 1 or 2 hours before
sunset and fished overnight. When nets were retrieved (early morning), water
temperature was determined at the surface and near the bottom with a bucket
thermometer. Water samples were then taken from the surface and bottom with
Niskin bottles and were later analyzed for salinity with a Kahlisco precision
induction salinometer. Salinity was computed from conductivity ratios using the
equations of Cox, Culkin, and Riley (1967).
All captured elasmobranchs were measured to the nearest millimetre. Total
length (tl) of all elasmobranchs except rays was measured; for rays disc width
(Dw) was measured. The sex of all fishes was determined and the reproductive
condition of females was determined by necropsy.
The relative abundance of all sizes of all species of elasmobranchs in Elkhorn
Slough could not be evaluated due to the size and species selectivity bias of the
gill nets. Sharks less than 40 cm tl, for example, were too small to be captured
by the smallest mesh netting used. Although bat rays and round stingrays were
captured, they usually were not captured unless their caudal sting became
entangled in the netting. Thus, capture results do not necessarily represent the
relative abundance of the different species in Elkhorn Slough. Also, information
obtained on the abundance and species of elasmobranchs in Elkhorn Slough
during summer was limited because green algae, Enteromorpha spp., grew pro-
fusely in Elkhorn Slough. As a result, drifting algae completely fouled the gill nets
during June and July preventing capture of elasmobranchs.
To facilitate seasonal comparisons of elasmobranch abundance, the year was
divided as follows: winter (Nov., Dec, Jan.); spring (Feb., March, April); sum-
mer (May, June, July); and fall (Aug., Sept., Oct.).
RESULTS
Tennperature and Salinity
The water at the study site was well mixed during all collection periods.
Wilcoxon matched-pairs sign-ranks tests (Siegel 1956) indicated there was no
significant difference between the surface and bottom water temperature (P >
.05) or the surface and bottom salinity (P > .05). There were, however, season-
al differences in water temperature and salinity (Figure 2). The monthly aver-
ages of surface and bottom water temperature were low (below 12''C) during
winter and early spring but high (above 14°C) during most other parts of the
year.
Except for November, the monthly averages of surface and bottom salinity
were not significantly different from water in Monterey Bay (P > .05) and
ranged from 32.7 to 33.6 %o- During November, as a result of heavy rainfall, the
monthly average surface and bottom salinity decreased to 30.9 %o-
Species Accounts
Seven species of elasmobranch fishes were captured in Elkhorn Slough. These,
listed in order of total number captured, were the leopard shark, Triakis semifas-
ciata; bat ray, Myliobatis californica; gray smoothhound, Mustelus californicus;
round stingray, Urolophus halleri; shovelnose guitarfish, Rhinobatos productus;
brown smoothhound, Mustelus henlei; and thornback, Platyrhinoidis triseriata.
ELASMOBRANCHS IN ELKHORN SLOUGH
213
17
16 -
o"
15
LlJ t4
OH
3
I-
<
tC 13
12
11
10
O Salinity
O Temperature
- 35
- 34
2.
37
36
33 ?
<
- 32
- 31
30
^.
ONDJFMAMJJAS
MONTHS
FIGURE 2. The average monthly water temperature and salinity (surface and bottom values
combined) at the study site in Elkhorn Slough, 1971-72.
Leopard Shark
Four-hundred-twenty-two leopard sharks were captured. Individuals ranged
in size from 40 to 1 40 cm tl. Leopard sharks were commonly captured in Elkhorn
Slough during all seasons (Figure 3). Although gill nets did not function properly
in June and July, leopard sharks were frequently caught during these months by
fishermen (Talent, unpubl. data). Pronounced differences existed in the season-
al length-frequency distribution of leopard sharks more than 60 cm tl ( Figure
4). Leopard sharks 60 to 100 cm tl were commonly captured during summer
and fall but relatively few were captured during winter and spring. Leopard
sharks 100 to 140 cm tl were captured in all seasons but were particularly
abundant in winter and spring.
The smallest gravid female (i.e., containing eggs or embryos in uterine ovi-
ducts) was 104 cm tl. The number of eggs or embryos found in uterine oviducts
of gravid leopard sharks ranged from 6 to 24. All gravid females examined in
April contained near-term young but many of those examined in late May
contained eggs with little embryonic development. Thus, leopard sharks appar-
ently gave birth to young in Elkhorn Slough during April and May.
Bat Ray
One-hundred-fifty-two bat rays, ranging in size from 20 to 140 cm DW, were
captured. Bat rays were commonly captured in Elkhorn Slough throughout
spring, summer, and fall but fewer were captured in winter ( Figure 3) . Although
214 CALIFORNIA FISH AND CAME
the disc width-frequency distribution of bat rays varied seasonally, bat rays less
than 60 cm dw were captured more frequently than large bat rays during all
seasons. However, gill nets were not efficient at capturing large bat rays. There-
fore, the size distribution captured did not reflect the relative abundance of the
different size classes of bat rays present in Elkhorn Slough.
The smallest gravid female was 105 cm DW. Reproductively mature females
captured in June 1972 by fishermen contained from 2 to 6 fully developed young
in their uterine oviducts. But mature females captured in August contained eggs
with little embryonic development. Apparently, bat rays gave birth in Elkhorn
Slough during July and August.
Gray Smoothhound
Sixty-nine gray smoothhounds, ranging in size from 60 to 120 cm tl, were
captured in Elkhorn Slough. Gray smoothhounds were commonly captured in
winter arid early spring but were captured infrequently during other parts of the
year (Figure 3). No seasonal changes in length-frequency distribution of gray
smoothhounds were apparent.
The smallest gravid female was 87.5 cm tl. Gravid females contained from
3 to 16 developing embryos in their uterine oviducts. No gravid females contain-
ing full-term embryos were captured at the study site which suggests that gray
smoothhounds did not give birth to young in the slough.
Round Stingray
Forty-eight round stingrays were captured. Individuals ranged in size from 20
to 25 cm DW and were all mature males except for one mature female. Round
stingrays were frequently captured during winter but were rarely captured during
other parts of the year (Figure 3).
Neither gravid female nor juvenile round stingrays were captured during the
study which strongly suggests that round stingrays do not breed in Elkhorn
Slough,
Shovelnose Guitarfish
Forty shovelnose guitarfish were captured in Elkhorn Slough. These ranged in
size from 60 to 150 cm TL. Shovelnose guitarfish were commonly captured in
gill nets during fall and early winter but were captured infrequently during other
parts of the year ( Figure 3 ) . Shovelnose guitarfish, however, were also common-
ly captured during June and July by fishermen, months during which gill nets did
not function. No seasonal changes in length-frequency distribution of shovel-
nose guitarfish were apparent during the period they were captured in Elkhorn
Slough.
The smallest gravid female was 110 cm TL. Only eggs with little embryonic
development were found in uterine oviducts of mature females captured in the
slough. Thus, no evidence was found to suggest parturition took place in Elkhorn
Slough.
Brown Smoothhound
Twenty brown smoothhounds were captured at the study site; individuals
ranged in size from 40 to 100 cm TL. Brown smoothhounds were commonly
captured in Elkhorn Slough in spring but were captured infrequently during other
seasons (Figure 3). No seasonal changes in length-frequency distribution of
brown smoothhounds were observed.
ELASMOBRANCHS IN ELKHORN SLOUCH
(T
UJ
a.
L<
sopard Shar
k(N
= 422)
20
10
0
«— •
Hn
n
—
—
D
30
20
10
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40
30
20
10
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40
30
20
10
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30
20
10
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Bat Ray(N = l52)
n-nn
D Q
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n
Round Stingray {N = 48)
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D
Shovelnose Guitarf isti (N =40)
n
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B
ow
n Sm
p]
hhound (N = 20)
20
10
n
0
n
n n
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
MONTHS
FIGURE 3. Seasonal distribution of elasmobranch fishes captured in Elkhorn Slough, 1971-72.
216
CALIFORNIA FISH AND GAME
FALL (N = I34)
30
20
10
0
50
40
WINTER (N = 94)
30
20
10
0
rn
1 I
SPRING (N = I2I)
30
20
10
0
" I
SUMMER (N = 56)
30
20
10
0
600-
799
800-
999
1000-
1199
1200-
1399
TOTAL LENGTH (mm)
FIGURE 4. Seasonal length-frequency distribution of leopard sharks, Triakis semifasciata, captured
in Elkhorn Slough, 1971-72.
ELASMOBRANCHS IN ELKHORN SLOUGH 217
The smallest gravid female was 67 cm tl. Gravid females contained from 1
to 8 developing embryos in their uterine oviducts. Hovc'ever, no females contain-
ing full-term young in their oviducts were captured which suggests that few, if
any, brown smoothhounds give birth in the slough.
Thornback
Thornbacks were rare at the study site; only one was captured during the
entire study. This specimen was a mature male and was captured during fall.
DISCUSSION
A minimum of seven species of elasmobranch fishes frequented the study area
in Elkhorn Slough. The study area, however, was not utilized by all seven species
during all seasons. Leopard sharks and bat rays were commonly captured
throughout the year but gray smoothhounds, brown smoothhounds, shovelnose
guitarfish, and round stingrays were only seasonally common. Thornbacks were
apparently rare at the study site during all seasons.
The causes of the seasonal patterns of distribution of elasmobranchs at the
study site are unknown. It is unlikely that my sampling activities biased the
seasonal patterns of occurrence observed during this study because a tagging
study indicated that less than 10% of any population of elasmobranch using the
study area was collected (Talent, unpubl. data). In addition, salinity probably
was not a major factor affecting seasonal abundance of any species of elasmo-
branch at the study area because salinity varied little from seawater throughout
most of the year. November was the only period during which salinity was
reduced by rainfall. During this period, salinity at the study area was lowered
to about 31 %o but no reduction in the number of elasmobranchs captured was
observed. However, there is a need to study the seasonal distribution of elasmo-
branchs in Elkhorn Slough durinjg years with heavy rainfall to determine the
effects of lower salinities.
The temperature cycle at the study area possibly affected the seasonal distri-
bution of some elasmobranchs. Monthly averages of surface and bottom water
temperature at the study area ranged from a low of 10. TC in winter to a high
of 17.2°C in summer. This cycle of temperature change occurs fairly regularly in
the Monterey Bay area but may occur several weeks earlier or later during
different years (Johnson 1961 ). Gray smoothhounds and round stingrays were
most abundant when water temperature was below ITC whereas shovelnose
guitarfish were most abundant when water temperature was above 14°C. Addi-
tionally, predominantly large mature leopard sharks were captured when water
temperature was below ITC, whereas predominantly immature leopard sharks
were captured when water temperature was above 14°C. There appeared to be
little correlation, however, between water temperature and the seasonal distri-
bution of bat rays and brown smoothhounds. Although water temperature may
be one factor affecting the seasonal distribution of elasmobranchs, other factors
such as food availability, competition, and reproductive activity probably also
affect seasonal distribution.
Elkhorn Slough may be of great importance to the life histories of some
populations. The rich invertebrate fauna in the slough is an important food
source for elasmobranch fishes (Talent 1976, 1982). Furthermore, the slough
may be a nursery area for elasmobranchs. During the study many leopard sharks
and bat rays apparently gave birth in Elkhorn Slough. Although there was no
218 CALIFORNIA FISH AND CAME
evidence that Elkhorn Slough was an important breeding area for other species
of elasmobranchs, some individuals probably do breed in the slough. Specifi-
cally, a few shovelnose guitarfish may occasionally breed in the slough. The
presence of very small shovelnose guitarfish in stomach contents of leopard
sharks captured in Elkhorn Slough (Talent 1976) and the occasional capture of
very small individuals in the slough with seines (Talent, unpubl. data) seems to
support this contention.
The presence of round stingrays in Elkhorn Slough raises some interesting
questions. Babel (1967) found that in southern California, adult round stingrays
were non-migratory and moved only short distances over a period of years.
However, my data indicated the population of round stingrays occurring in
Elkhorn Slough was migratory. In addition, the occurrence of 47 males out of a
total of 48 specimens collected strongly supports the contention of Herald et al.
(1960) that sexual segregation occurs in Elkhorn Slough.
If the seasonal occurrence of elasmobranchs at the study site is reflective of
elasmobranch occurrence in Elkhorn Slough, then gray smoothhounds, brown
smoothhounds, shovelnose guitarfish and round stingrays, as well as different
size classes of leopard sharks and bat rays, utilized the slough for only part of
the year and, therefore, are migratory. Leopard sharks can migrate long distances
between habitats; one adult female was recaptured 112 km north in San Fran-
cisco Bay one year after it was tagged in Elkhorn Slough (Talent, unpubl. data).
Little, however, is known about the seasonal movement patterns of the elasmo-
branch species frequenting Elkhorn Slough. Research must be conducted on
marked elasmobranchs along the Pacific Coast to determine age specific migra-
tory patterns before the seasonal patterns of occurrence of these fishes in Elk-
horn Slough and other embayments can be fully evaluated.
ACKNOWLEDGMENTS
I thank C. E. Bond and G. M. Cailliet for critically reviewing an earlier version
of the manuscript, and A. Staebler and M. Silver for their suggestions during the
investigation. J. Cohen, J. Cross, G. McDonald, and E. Yarberry assisted in
collecting specimens; S. Owen and S. Seelinger analyzed water samples for
salinity. I especially thank C. Talent for assistance in all areas of the study. The
Oklahoma Cooperative Fishery Research Unit supplied financial support for
completion of this study.
LITERATURE CITED
Babel, ). S. 1967. Reproduction, life history, and ecology of the round stingray, Urolophus halleri Cooper. Calif.
Fish and Came, Fish Bull. (78):1-104.
Browning, B. M, 1972. The natural resources of Elkhorn Slough — their present and future use. Calif. Dept. Fish and
Game, Coastal Wetland Series 4;1-105.
Cox, R. A., F. Culkin, and ). P. Riley. 1967. The electrical conductivity /chlorinity relationship in natural sea water.
Deep-Sea Res., 14:203-220.
Herald, E. S. 1953. The 1952 shark derbies at Elkhorn Slough, Monterey Bay, and at Coyote Point, San Francisco
Bay. Calif. Fish Came, 39(2):237-243.
Herald, E. S., and R. P. Dempster. 1952. The 1951 shark derby at Elkhorn Slough, California. Calif. Fish Game,
38(1):133-134.
Herald, E. S., W. Schneebeli, N. Green, and K. Innes. 1960. Catch records for seventeen shark derbies held at
Elkhorn Slough, Monterey Bay, California. Calif. Fish Game, 46(1):59-67.
ELASMOBRANCHS IN FLKHORN SLOUCH 219
Johnson, ). H. 1961. Sea surface tenfiperature monthly average and anomaly charts northeastern Pacific Ocean,
1947-58. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 385. 56pp.
Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill Book Co., Inc., New York, N Y
312pp.
Talent, L. C. 1976. Food habits of the leopard shark, Triakis semifasaata, in Elkhorn Slough, Monterey Bay,
California. Calif. Fish Came, 62(4):286-298.
Talent, L. G. 1982. Food habits of the gray smoothhound, Mustelus californicus, brown smoothhound, Mustelus
henlei, shovelnose guitarfish, Rbinobatos productus, and bat ray, Myliobatis califomica, in Elkhorn Slough,
California. Calif. Fish Came, 68(4):224-234.
220 CALIFORNIA FISH AND CAME
Calif. Fish and Came 7M4): 220-224 1985
EFFECTS ON WILDLIFE OF ETHYL AND METHYL
PARATHION APPLIED TO CALIFORNIA RICE FIELDS ^
THOMAS W. CUSTER
U.S. Fish and Wildlife Service
Patuxent Wildlife Research Center
Gulf Coast Field Station
P.O. Box 2506
Victoria, Texas 77902
ELWOOD F. HILL
U.S. Fish and Wildlife Service
Patuxent Wildlife Research Center
Laurel, Maryland 20708
AND
HARRY M. OHLENDORF
Pacific Coast Field Station
c/o Division of Wildlife and Fisheries Biology
University of California
Davis, California 95616
Selected rice fields on the Sacramento National Wildlife Refuge Complex were
aerially sprayed one time during May or June 1982 with either ethyl (0.11 kg Al/ha)
or methyl (0.84 kg Al/ha) parathion for control of tadpole shrimp, Triops lon-
gicaudatus. No sick or dead vertebrate wildlife were found in or adjacent to the
treated rice fields after spraying. Specimens of the following birds and mammals
were assayed for brain cholinesterase (ChE) activity to determine exposure to either
form of parathion: house mouse, Mus musculus; black-tailed jackrabbit, Lepus cali-
fornicus; mallard. Anas platyrhynchos; ring-necked pheasant, Phasianus colchicus;
American coot, FuUca americana; and red-winged blackbird, Agelaius phoeniceus.
Both mice and pheasants from methyl parathion-treated fields had overall mean ChE
activities that were significantly (P < .05) inhibited compared with controls, and 7,
40, 54, and 57% of individual blackbirds, pheasants, mice, and coots, respectively,
had inhibited brain ChE activities (i.e., less than — 2 SD of control mean). Although
no overall species effect was detected for ethyl parathion treatment, pheasants
(43%), coots (33%), and mice (37%) had significantly inhibited brain ChE activities.
Neither of the parathion treatments appeared acutely hazardous to wildlife in or
adjacent to rice fields, but sufficient information on potential hazards was obtained
to warrant caution in use of these chemicals, especially methyl parathion, in rice
fields.
INTRODUCTION
Ethyl parathion [phosphorothioic acid (?,0-diethyl 0-(4-nitrophenyl) ester] and
methyl parathion [phosphorothioic acid Q,(9-dimethyl 0-(4-nitrophenyl) ester]
are two organophosphorus insecticides that receive diverse use on North Ameri-
can croplands and are the principal insecticides used on California rice (Calif.
Dept. Food Agric. 1982). Both forms of parathion are highly toxic to, wildlife
(Hill et al. 1975; Hudson, Tucker, and Heagele 1984; Schafer et al. 1983),
however only ethyl parathion has been repeatedly implicated in field mortalities
of wildlife (Mills 1973; Stone 1979; White et al. 1979, 1982; Grue et al. 1983;
Stone, Overmann, and Okoniewski 1984) even though methyl parathion is one
of the most widely used insecticides in the United States. Because of the agricul-
' Accepted for publication February 1985.
PARATHION EFFECTS ON WILDLIFE 221
tural importance of these closely related insecticides and the disparity of their
effects on wildlife, we conducted a study of the two chemicals to determine
whether either was detrimental to wildlife when applied to rice by standard
aerial methods. The Sacramento National Wildlife Refuge Complex (SNWRC),
California, including four refuges and over 8,100 ha of marsh and cropland, was
selected for the study because special land-use permits are issued for rice farm-
ing and about two-thirds of the crop (about 800 ha) may be treated with
pesticides and harvested; the remainder of the rice crop cannot be treated or
harvested. Brain cholinesterase activity in random-captured wildlife was our
primary means of evaluating exposure (Bunyan, Jennings, and Taylor 1968;
Zinkel et al. 1980; DeWeese et al. 1983).
METHODS
Selected rice fields on SNWRC were sprayed once during May or June 1982
with either ethyl or methyl parathion for control of tadpole shrimp. Ethyl parath-
ion was applied at 0.11 kgAI (active ingredient) /ha (= 0.1 lb/acre) on 21 May
by helicopter from 3 m altitude or less at an air speed of 80 kph on 260 ha of
rice on the Sacramento National Wildlife Refuge (NWR). It was also applied on
8 June by fixed-wing aircraft from 2 m altitude or less at an air speed of 190 kph
on 72 ha of rice on the Sutter NWR. Methyl parathion was applied at 0.84 kg
Al/ha ( = 0.75 lb/acre) by helicopter from 3 m altitude or less at an air speed
of 80 kph on 32 ha (20 May) and 70 ha (25 May) rice fields on the Colusa NWR.
The effects of each treatment on wildlife were evaluated by routine observa-
tions of animal activities on and adjacent to parathion-treated rice fields, and by
opportunistic sampling of animals within a 20-m bound of the fields on the
second and third days postspray. All animals except house mice were shot,
decapitated, and their heads frozen on dry ice preparatory for ChE assay. House
mice were live-trapped but otherwise handled the same as other species. Con-
trols were collected and stored as above from untreated sites on the SNWRC
before any spraying was performed. Specimens studied included both sexes of
house mouse, black-tailed jackrabbit, and American coot, and males only of
ring-necked pheasant, mallard, and red-winged blackbird. Whole brain ChE
activity (based on longitudinally bisected half brains) were assayed at 25°C by
the method of Ellman et al. (1961) as described by Hill and Fleming (1982).
Brain cholinesterase (ChE; predominately acetylcholinesterase, EC 3.1.1.7) ac-
tivity of each animal was then compared with the prespray norm for the species
as described by Hill and Fleming (1982). Individuals from like treatments were
also pooled and compared by one (single sex) or two-way (multiple sex)
analysis of variance ( a = .05 ) . The Bonferroni multiple comparison method was
used to separate means (Miller 1981).
RESULTS
Although intensive searches were not conducted, general observations were
continued on and adjacent to the treated rice fields for 10 days postspraying and
no sick or dead birds or mammals were found.
Ring-necked pheasants and house mice collected near rice fields after applica-
tion of 0.84 kg Al/ha methyl parathion had significantly (P < .05) lower brain
ChE activity than either controls or those from fields treated with 0.1 1 kg Al/ha
ethyl parathion (Table 1 ). Maximum brain ChE inhibition from methyl parathion
was 39% for both pheasants and mice. Even though mean brain ChE activities
222
CALIFORNIA FISH AND GAME
in red-winged blackbirds and American coots were not significantly inhibited by
the methyl parathion treatments, 7 and 57% of the individuals sampled had brain
ChE activities below the norm (i.e., — 2 SD of control mean; Hill and Fleming
1982) for the species. Mean brain ChE activity was not significantly reduced for
any of the species collected near ethyl parathion-treated rice fields. However,
individual brain ChE activities were below the norm for individual pheasants,
coots, and mice, but not mallards, blackbirds, or rabbits. Maximum ethyl parath-
ion-induced brain ChE inhibition for pheasants, coots, and mice was 18, 15, and
52%, respectively. No between-sex differences were detected for coots, house
mice, or jackrabbits [two-way analysis of variance (a = .05)].
TABLE 1. Brain ChE Activity (/Limol/min/g, wet weight) in Birds and Mammals Collected
Near Rice Fields on the Sacramento National Wildlife Refuge Complex, 1982.
Individual
Species
Treatment
N
Mean
SD
Extremes
respondents '
Ring-necked
Control
10
13.5 A^
0.82
12.7 and 15.7
(11.9)
pheasant
Ethyl parathion
7
12.2 A
0.88
11.1 and 13.4
3
Methyl parathion
5
11.5B
2.04
8.2 and 13.4
2
Mallard
Control
5
8.9
1.28
7.5 and 11.0
(6.4)
Ethyl parathion
6
8.6
0.67
7.8 and 9.4
0
Red-winged
Control
10
19.1
1.84
16.4 and 22.0
(15.4)
blackbird
Ethyl parathion
9
20.0
1.20
17.6 and 21.1
0
Methyl parathion
14
18.5
1.45
14.3 and 20.0
1
American
Control
2
18.8
1.06
18.1 and 19.6
(16.7)
coot
Ethyl parathion
3
17.0
0.91
16.0 and 17.7
1
Methyl parathion
7
15.6
3.60
10.3 and 20.1
4
House
Control
19
5.4 A3
0.40
4.7 and 6.1
(4.6)
mouse
Ethyl parathion
19
5.3 A
0.87
2.6 and 6.5
2
Methyl parathion
13
4.7 B
0.51
3.3 and 5.2
5
Black-tailed
Control
5
6.2
0.78
5.2 and 7.3
(4.7)
jackrabbit
Ethyl parathion
4
6.8
1.17
5.9 and 8.5
0
' Individual respondents = no. of parathion-exposed animals below parenthesized diagnostic threshold, (i.e., <
— 2 SD of control mean).
^ Means not sharing the same letter are significantly different from one another (ANOVA, a = .05).
^ Means not sharing the same letters are significantly different from one another [(two-way ANOVA, sex (2),
treatment (3), a = .05, Bonferroni multiple comparison method)]. There was no significant between-sex
difference.
DISCUSSION
Our findings of no mortality and mean inhibition of brain ChE activity of 15%
for ring-necked pheasants following an application of 0.84 kg Al/ha methyl
parathion are consistent with earlier studies. Methyl parathion and toxaphene
(chlorinated camphene), each applied at 1.1 kg Al/ha to cotton, caused no
deaths but produced an average brain ChE inhibition of 23% in bobwhite quail,
Colinus virginianus (Smithson and Sanders 1978). No bobwhite or pheasant
mortality was associated with a methyl parathion application of 0.56 kg Al/ha
to alfalfa (Edwards and Graber 1968).
Although the mentioned applications of methyl parathion at 0.56 to 1.1 kg A
I/ha were not found lethal under conditions of the various studies, there is
evidence that the very young of precocial species may be affected by such
PARATHION EFFECTS ON WILDLIFE 223
treatments. Three-day-old pheasants displayed nervous disorders when exposed
to a methyl parathion application of 0.3 kg Al/ha, and 5-day-old chicks died at
0.6 kg Al/ha but neither treatment affected 10-day-old pheasants (Christensen
1969). Gallinaceous birds less than 2 wk old are shown less tolerant of both field
application (Messick et al. 1974) and controlled dietary exposure (Ludke, Hill,
and Dieter 1975; Hill and Camardese 1981) of organophosphorus pesticides
than even 1 -mo-old chicks. This age disparity of tolerance of organophosphates
did not occur in acute tests with mallards from 36 h to 6 months of age (Hudson,
Tucker, and Haegele 1972).
The ethyl parathion application of 0.1 1 kg Al/ha in our study was well below
that reported to affect wildlife. Pinioned mallards on ponds sprayed with 0.45
kg Al/ha ethyl parathion six times at biweekly intervals (Keith and Mulla 1966)
or once at 1.12 kg Al/ha (Mulla, Keith, and Gunther 1966) showed no mortality.
When fields were sprayed with 0.9 kg Al/ha ethyl parathion, adult pheasants
exhibited neither mortality nor inhibition of brain ChE activity (Messick et al.
1974). Wolfe, Baxter, and Munson (1971) found no behavioral changes or
mortality of 9-wk-old pheasants sprayed with 0.56 kg Al/ha ethyl parathion on
grain sorghum; average brain ChE activity was depressed by about 20%.
We conclude that ethyl parathion applied at 0.11 kg Al/ha to rice poses no
lethal threat to wildlife, and although we observed no mortality, methyl parath-
ion at > 0.84 kg Al/ha may pose some hazard. This latter conclusion is based
on mentioned published evidence of early chick mortality (Christensen 1969),
and our demonstration of significant inhibition of brain ChE activity associated
with methyl parathion exposure in at least one species each of bird and mammal.
ACKNOWLEDGMENTS
We thank C. Bitler, D. Kalfsbeck, P. Mack, D. Mauser, and J. Weaver for field
assistance; the Sacramento NWR staff and J. G. ZinkI for logistic support; P.
McDonald for typing the manuscript; and E. Kolbe and S. Wiemeyer for review-
ing the manuscript.
LITERATURE CITED
Bunyan, P. ]., D. M. Jennings, and A. Taylor. 1968. Organophosphorus poisoning, diagnosis of poisoning in
pheasants owing to a number of common pesticides. ). Agric. Food Chem., 16:332-339.
California Department of Food and Agriculture. 1982. Pesticide Use Report: Annual 1981: Calif. Dept. of Food
and Agric, Sacramento. 263 p.
Christensen, G. C. 1969. Pheasant-pesticide report. Nevada Dept. Fish Came, Job Final Rep. W-39-R-9. Job 16.
Mimeogr. 26 p.
DeWeese, L. R., L. C. McEwen, L. A. SettimI, and R. D. Deblinger. 1983. Effects on birds of fenthion aerial
applications for mosquito control. J. Econ. Entomol., 76:906>-911.
Edwards, W. R., and R. R. Craber. 1968. Responses of avians to methyl parathion in a hayfield. Pres. III. Nat.
Hist. Surv., Urbana, III., 53-59.
Ellman, C. L., K. D. Courtney, V. Andres, Jr. and R. M. Featherstone. 1961. A new and rapid colorimetric
determination of acetylcholinesterase activity. Biochem. Pharmacol., 7:88-98.
Grue, C. E., W. J. Fleming. D. C. Busby, and E. F. Hill. 1983. Assessing hazards of organophosphate pesticides
to wildlife. Trans. N. Am. Wildl. Nat. Resour. Conf., 48:200-220.
Hill, E. F., and M. B. Camardese. 1981. Subacute toxicity testing with young birds: Response in relation to age
and intertest variability of LC50 estimates. Pages 41-65 in D. W. Lamb and E. E. Kenaga, eds. Avian and
Mammalian Wildlife Toxicology: Second Conference, Am. Soc. Test. Materials, STP 757.
Hill, E. F., R. C. Heath, J. W. Spann, and J. D. Williams. 1975. Lethal dietary toxicities of environmental pollutants
to birds. U. S. Fish Wildl. Serv. Spec. Sci. Rep. Wildl. 191. 61 p.
Hill, E. F., and W. J. Fleming. 1982. Anticholinesterase poisoning of birds: Field monitoring and diagnosis of acute
poisoning. Environ. Toxicol. Chem., 1:27-38.
224 CALIFORNIA FISH AND GAME
Hudson, R. H., R. K. Tucker, and M. A. Haegele. 1972. Effect of age on sensitivity: Acute oral toxicity of 14
pesticides to mallard ducks of several ages. Toxicol. Appl. Pharmacol., 22:556-561.
Hudson, R. H., R. K. Tucker and M. A. Haegele. 1984. Handbook of toxicity of pesticides to wildlife, 2nd ed.
U.S. Fish Wildl. Serv. Resour. Publ. 153. 90 p.
Keith, J. O., and M. S. Mulla. 1966. Relative toxicity of five organophosphorus mosquito larvicides to mallard
ducks. ). Wildl. Manage., 30:553-563.
Ludke, J. L., E. F. Hill, and M. P. Dieter. 1975. Cholinesterase (ChE) response and related mortality among birds
fed ChE inhibitors. Arch. Environ. Contam. Toxicol., 3:1-21.
Messick, J. P., E. C. Bizeau, W. W. Benson, and W. H. Mullins. 1974. Aerial pesticide applications and ring-necked
pheasants. J. Wildl. Manage., 38:679-685.
Miller, R. G. 1981. Simultaneous statistical inference, 2nd ed. Springer Verlag, New York. 299p.
Mills, J. A. 1973. Some observations on the effects of field applications of fensulfothion and parathion on bird
and mammal populations. Proc. N. Z. Ecol. Soc, 20:65-71.
Mulla, M. S., ). O. Keith, and F. A. Gunther. 1966. Persistence and biological effects of parathion residues in
waterfowl habitats. ). Econ. Entomol., 59:1085-1090.
Schafer, E. W., Jr., W. A. Bowles, and J. Hurlbut. 1983. The acute oral toxicity, repellency, and hazard potential
of 998 chemicals to one or more species of wild and domestic birds. Arch. Environ. Contam. Toxicol.,
12:355-382.
Smithson, P. C, and O. T. Sanders, Jr. 1 978. Exposure of bobwhite quail and cottontail rabbits to methyl parathion.
Proc. Southeast Assoc. Fish Wildl. Agencies, 32:326-334.
Stone, W. B. 1979. Poisoning of wild birds by organophosphate and carbamate pesticides. NY Fish Game J.,
26:37^7.
Stone, W. B., S. R. Overmann, and J. C. Okoniewski. 1984. Farmers purposefully poison birds with parathion.
Condor, 86:333-336.
White, D. H., K. A. King, C. A. Mitchell, E. F. Hill, and T. G. Lamont. 1979. Parathion causes secondary poisoning
in a laughing gull breeding colony. Bull. Environ. Contam. Toxicol., 23:281-284.
White, D. H., C. A. Mitchell, E. J. Kolbe, and J. M. Williams. 1982. Parathion poisoning of wild geese in Texas.
J. Wildl. Dis., 18:389-391.
Wolfe, C. W., W. L. Baxter, and J. D. Munson. 1971 . Effects of parathion on young pheasants. Nebr. Agric. Exper.
Sta., 18:4-6.
ZinkI, J. G., R. B. Roberts, C. J. Henny, and D. J. Lenhart. 1980. Inhibition of brain cholinesterase activity in forest
birds and squirrels exposed to aerially applied acephate. Bull. Environ. Contam. Toxicol., 24:676-683.
SAN JOAQUIN VALLEY BLUEGILLS 225
Calif. Fish and Came 7M4): 7\ {4) 22S-244 1985
POPULATION BIOLOGY OF BLUEGILLS, LEPOMIS
MACROCHIRUS, IN LOTIC HABITATS ON THE IRRIGATED
SAN JOAQUIN VALLEY FLOOR'
MICHAEL K. SAIKI
U.S. Fish and Wildlife Service
Columbia National Fisheries Research Laboratory
Field Research Station — Dixon
6924 Tremont Road
Dixon, California 95620
AND
CHRISTOPHER J. SCHMITT
U.S. Fish and Wildlife Service
Columbia National Fisheries Research Laboratory
Route #1
Columbia, Missouri 65201
Rapid expansion of irrigated agriculture in the western United States has prompted
concerns for aquatic resources. Although the impacts of irrigation activities on qual-
ity and quantity of river water are well documented (e.g., high turbidity from soil
erosion, eutrophication from nutrient runoff, pesticide contamination, reduced dis-
charge), their effects on fish populations are still poorly understood. We studied the
food, growth, and relative weight (a measure of body condition) of bluegills, Lepo-
mis macrochirus, in relation to environmental factors in reaches of the San Joaquin
and Merced rivers that have been affected to varying degrees by irrigation return
flows. Fry of bluegills ate mostly cladocerans and copepods; fingerlings and larger
fish ate immature aquatic insects, terrestrial insects, amphipods, and mollusks. Biue-
gill stomachs were fuller and contained a higher diversity of forage taxa in habitats
with low turbidity and conductivity, weak buffering capacity, and low nutrient
levels; bluegills also ate a more diverse diet where the potential forage supply
(benthic macroinvertebrates) was most diverse. Bluegills attained mean total
lengths of about 42 mm at age I, 86 mm at age 11, 116 mm at age III, 153 mm at age
IV, and 166 mm at age V. Mean relative weight ranged from 96-111. Growth rate and
relative weight were not significantly correlated with environmental or dietary varia-
bles. On the basis of our study, we concluded that environmental degradation from
irrigation activities affected the diet of bluegills primarily by modifying the food
supply, but growth rate and body condition were not affected.
INTRODUCTION
Irrigated agriculture increased from 15 million ha in 1964 to nearly 17 million
ha by 1974 in the United States (U.S. Bureau of the Census 1978). Over 88%
of the new acreage was in the 1 7 westernmost states and Louisiana. In California,
more than 90% of the 3.3 million ha of cropland harvested in 1 974 was irrigated.
The rapid growth of irrigation has led to concerns that irrigation-related activi-
ties may be detrimental to aquatic biota. In the San Joaquin Valley of California,
where crops have been grown for over a century, irrigated agriculture is current-
ly the most prevalent land use (California Department of Water Resources 1960,
1969). During the irrigation season (usually March to October) return flows
from irrigated fields constitute most of the discharge in low-elevation rivers
(California Department of Water Resources 1960).
'Accepted for publication February 1985.
226 CALIFORNIA FISH AND GAME
Numerous investigators (e.g., Sylvester and Seabloom 1963, Hotes and Pear-
son 1977, Miller et al. 1978) have reported that altered temperature and flow
regimes, and increased concentrations of dissolved salts, pesticides, sediments,
agricultural fertilizers, and animal wastes are among the environmental changes
typical of rivers that drain irrigated watersheds. In the San Joaquin Valley, physi-
cal and chemical characteristics of rivers are influenced considerably by irriga-
tion activities (Sorenson and Hoffman 1981, Sorenson 1982, Saiki 1984).
Although recent attempts have been made to assess the effects of general
agricultural land use on aquatic life (e.g., Mitchell 1975; Welch, Symons, and
Narver 1977; Dance and Hynes 1980; Luey and Adelman 1980; Marsh and
Waters 1980), few studies have specifically addressed the effects of irrigated
agriculture on fish populations.
This study was part of a broader ecological investigation designed to profile
environmental conditions in low elevation rivers on the San Joaquin Valley floor.
Our major objectives were to ( i ) describe the food, growth, and body condition
of different populations of resident bluegills, Lepomis macrochirus, from differ-
ent locations on the rivers, and (ii) determine if any differences in these biologi-
cal characteristics are associated with environmental changes from irrigation.
The bluegill was studied because it is an important warmwater game fish that
is common throughout most of the study area (Saiki 1984). The ecology and
general life history of bluegills that inhabit lakes and reservoirs have been well
studied in California and elsewhere (see reviews and bibliographies by Emig
1966; Carlander 1977; Hartmann, Hartmann, and von Geldern 1978; and oth-
ers); however, almost no information is available for populations from lotic
habitats on the floor of the San Joaquin Valley.
STUDY AREA
The San Joaquin Valley floor occupies about 3.4 million ha bounded by the
Sierra Nevada on the east, the Coast Range on the west, the Tehachapi Moun-
tains on the south, and the Sacramento-San Joaquin Delta on the north. The
Valley floor is one of the most important agricultural areas of California. Major
crops are cotton, grapes, tomatoes, hay, sugar beets, and vegetables. An arid
climate (13-36 cm of rainfall /yr characterized by hot summers and cool winters
necessitates irrigation on about 1.8 million ha of croplands.
Nine reaches (includes the mainstream and small backwaters flushed by the
mainstream) were sampled on the San Joaquin River and two of its tributaries,
the Merced River and Salt Slough ( Figure 1 ) . The San Joaquin and Merced rivers
originate in the Sierra Nevada, and their initial water supplies result mainly from
snowmelt and rainfall. Salt Slough originates on the Valley floor and derives most
of its discharge from groundwater seepage and irrigation return flows.
The physicochemical characteristics of the study reaches showed longitudinal
( upstream to downstream ) trends indicative of progressively increasing environ-
mental degradation (Saiki 1984). The most conspicuous of these trends were in
turbidity, total alkalinity, and conductivity (Table 1). Concentrations of mac-
ronutrients also increased upstream to downstream — especially NO3+NO2-N
and ortho-P04. Water quality improved somewhat in the San Joaquin River
below SJR-4 (see Figure 1 for names and locations of sampling reaches) due to
inflows of higher quality water from tributary streams. Dissolved oxygen concen-
trations typically exceeded 4 mg/ I (50% saturation) at all reaches, and were
never low enough to constitute a hazard to fishes. The pH was typically 7.0 to
8.9.
SAN JOAQUIN VALLEY BLUECILLS
227
Benthic macroin vertebrate communities were dominated by the Asiatic clam,
Corbicula fluminea; chironomid larvae, and oligochaetes (Sorenson and Hoff-
man 1981; M. K. Saiki, unpub. data). During our study, benthic standing crops
v^ere usually higher and communities more diverse in the upstream than in the
downstream reaches of both the San Joaquin and Merced rivers (Table 2).
CALIFORNIA
Enlorgeij Area
Somplinq Sites
® SJR
® SJR-2
(D SJR- 3
@ SJR-4
© SJR- 5
® SJR- 6
® MR
® MR-2
® SS
I I Nonirrigoted londs
[ I Irrigated londs
^B Reservoirs
FIGURE 1. Locations of sampling reaches and irrigated croplands in the study area. Names of
reaches are as follows: SJR-1, San Joaquin River near Fort Washington; SJR-2, San
Joaquin River at Firebaugh; SJR-3, San Joaquin River at Lander Avenue; SJR-4, San
Joaquin River at Fremont Ford State Recreational Area; SJR-5, San Joaquin River near
Crows Landing; SJR-6, San Joaquin River at South County Park; Salt Slough, Salt Slough
below Lander Avenue; MR-1, Merced River below Highway 59; and MR-2, Merced
River at George J. Hatfield State Recreational Area.
The composition of fish communities and relative abundance of individual
species in the study reaches differed upstream to downstream (Saiki 1984).
Species that occurred primarily at upstream reaches included sculpins, Cottus
spp.; green sunfish, Lepomis cyanellus; redear sunfish, L microlophus; Sacra-
mento squawfish, Ptychocheilus grandis; hardhead, Mylopharodon conoceph-
alus; and threespine stickleback, Gasterosteus aculeatus. Downstream reaches
were dominated by inland silverside, Menidia beryllina; white crappie, Pomoxis
annularis; threadfin shad, Dorosoma petenense; fathead minnow, Pimephales
promelas; splittail, Pogonichthys macrolepidotus; Sacramento blackfish. Ortho-
don microlepidotus; tule perch, Hysterocarpus traski; and striped bass, Morone
saxatilis. Besides bluegills, largemouth bass, Micropterus salmoides; black crap-
pie, Pomoxis nigromaculatus; and mosquitofish, Cambusia affinis were com-
monly found both upstream and downstream.
228
CALIFORNIA FISH AND CAME
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SAN JOAQUIN VALLEY BLUECILLS 229
TABLE 2. Mean Annual Standing Crops and Shannon-Weaver Diversities (d) of Benthic
Invertebrates from Selected Reaches of the San Joaquin and Merced Rivers, and
Salt Slough, July 1980-October 1981.
Standing crop
Reach* (g/"i' wet weight) d *
SJR-1 3.48 2.35
SJR-2 0.74 0.58
SJR-3 0.91 >. . 0.98
SjR-4 0.47 1.59
SJR-5 0.28 2.1 1
S)R-6 107 1.85
Salt Slough 0.73 0.81
MR-1 2.46 ^ 2.31
MR-2 1.07 2.39
"•■ See Figure 1 for names and locations of reaches.
• Calculated from unpublished data of M. K. Saiki.
METHODS AND MATERIALS
Bluegills were collected monthly from July 1980 through October 1981 at
SJR-1 and SJR-4. At all other reaches, we made collections every three months
during the same period, except that sampling was terminated after October 1980
at SJR-3 and started in January 1981 at SJR-6. Bluegills were captured with two
seines — one 5.5 m long by 2.4 m deep with 9.5-mm square mesh, and one 30.5
m long by 1.8 m deep with 12.7-mm square mesh. Fish were also collected by
backpack electrofishing at SJR-1, MR-1, and MR-2; other sites were too turbid
and the conductivities too high for effective electrofishing.
Immediately after capture, bluegills were measured (total length), and scales
were removed for age and growth analysis. The fish were then preserved in 10%
formalin.
After returning from the field, we weighed and sexed bluegills by dissection.
Stomach contents were removed from the anterior end of the esophagus to the
pyloric sphincter, and food items were identified with the help of taxonomic
keys (Pennak 1953, Usinger 1971, Merrit and Cummins 1978).
The fullness of the digestive tracts of bluegills (C, an index of the amount of
food eaten) was estimated from the formula
Q = (A X 100%)/(W- A)
where A is the weight of all food items in a fish's stomach and W is the weight
of the fish. This formula is a modification of I, ( = L'indice de repletion = fullness
index) that was first defined by Hureau (1969, cited by Berg 1979).
Diversity (d) j)f food was computed from the Shannon-Weaver formula
d = 3.321 928/ W (W log,o W - SW; log,o W^)
where W is the total biomass of individuals in the sample and W, is the biomass
of individuals in taxon i (Weber 1973). Wilhm (1968) showed that the use of
biomass units does not influence the estimate of d.
Food overlap (C\) was calculated from the formula
s s s
Cx = (2 2XiYi)/(5:Xi -h 2 Yi) '
i=1 i=1 i=1
where s is the total number of food taxa, X; is the proportion of the total diet
from site X composed of taxon i, and Y, is the proportion of the total diet from
site Y composed of taxon i (Zaret and Rand 1971 ). The value of Cx can vary
230 CALIFORNIA FISH AND CAME
from 0 (when the samples contain no taxa in common) to 1 (when the samples
are identical). The determination of a "significant" C is arbitrary, and depends
on the experience and judgment of the investigator. Zaret and Rand (1971)
assumed that C > 0.60 was significant overlap in their study of tropical stream
fish diets; we interpreted C\ > 0.70 as significant overlap.
Individual fish were aged by counting annuli on scales. The procedure de-
scribed by Brown, Miller, and von Geldern (1977) was used to identify new
annuli. The body-scale relation was computed, and growth was back-calculated
according to the Fraser-Lee method cited by Bagenal and Tesch (1978).
Relative weight {\N,)oi individual bluegills, a measure of body condition, was
computed from the formula
W, = W/W, X 100
where W is the actual weight of the fish and W, is a standard weight ( Wege and
Anderson 1978, Anderson 1980). According to Wege and Anderson (1978),
W, is easier to interpret than most other condition indices (e.g., C, K, or K„)
because its values can be compared directly between fish of different lengths
and from different populations. Furthermore, the calculation of W, is simple and
values do not change with different units of measure.
RESULTS
Food
Of 1,675 bluegill stomachs that we examined, 95% (1,600) contained food.
The arcsine-transformed percentage of stomachs with food (based on four size
classes of bluegills: <25, 26-50, 51-100, and >100 mm) was not significantly
correlated with total length of the fish ( r = 0.26, df = 33, P > .05 ) . Comparisons
of stomachs with food vs. empty stomachs (based on the combined size classes
of bluegills from all reaches) indicated significant seasonal differences
(X^ = 24.05, df = 3, f < .01 ); stomachs with food occurred most frequently
in spring (April-June, 99%), followed by summer (July-September, 97%), fall
(October-December, 93%), and winter (January-March, 92%). Among
reaches, the proportions of stomachs with food vs. empty stomachs differed
significantly (x' = 21.95, df = 8, P < .01), but longitudinal trends (upstream
to downstream) were not apparent.
Stomach Fullness and Diet Diversity
The fullness index (C,) was inversely correlated with fish size class (r =
—0.25, df = 105, P < .01 ), indicating that the stomachs of smaller fish typically
containecjl more food relative to body weight than did those of larger fish.
Therefore, comparisons of C, over seasons and reaches required adjustment of
the data to eliminate the influence of fish size. Consequently, we excluded all
fish < 25 mm long because this size class was usually available only in spring
and summer, and also deleted data from SJR-3 and Salt Slough where we failed
to collect all size classes of fish >25 mm year round. One-way Analysis of
Variance (ANOVA) performed on the arcsine-transformed proportions demon-
strated that seasonal differences for C, were significant (Fjeo = 3.90, P<.05).
Further testing [Fischer's Protected Least Significant Difference (LSD)] showed
that the winter mean (0.33%) was significantly (P< .05) lower than the means
for the other seasons (spring, 0.52%; summer, 0.55%; fall, 0.53%), which did
SAN JOAQUIN VALLEY BLUECILLS 231
not differ significantly among themselves. The mean annual C, values for the
eight reaches (range = 0.35-0.56%) did not differ significantly (f^^jj = 0.88,
P>0.05).
Diet diversity was positively correlated with total length (r = 0.66, df = 32,
P<.01), indicating that the variety of organisms eaten was generally wider
among large than among small fish. Comparisons of diet diversity among reaches
required deletion of data for fish < 25mm long because bluegills of this length
were not examined from SJR-5 and Salt Slough. One-way ANOVA demonstrated
that diet diversity differed significantly among reaches (Fgjs = 5.75, P < .01 ),
and that, although there were some exceptions, diet diversity was generally
higher in upstream than in downstream reaches (Table 3).
TABLE 3. Mean Annual Diversity of Food of Bluegills from Selected Reaches of the San
Joaquin and Merced Rivers, and Salt Slough.
Shannon-Weaver
Reach * ■ diversity, d ^
S)R-1 !.....!!.: 3.425 „,,,,
S)R-2 1 .862 b, ,, e
S)R-3 1.731 b,d,e
SJR-4 2.736 „. ,, d, ., ,
S)R-5 2.453 b, ,, d, .. ,
SJR-6 2.016 b, c, d, .
Salt Slough 1 .896 1, j, e
MR-1 2.991 „, ,, d, f
MR-2 3.281 „,,,,
• See Figure 1 for names and locations of reaches.
+ Values containing the same subscript are not significantly different (P > .05, LSD).
General Description of Food
The most obvious trend in food was related to fish size (Figure 2). In general,
zooplankton (primarily cladocerans and copepods) constituted most of the
food eaten by bluegills < 25 mm long. The dietary importance of zooplankton
decreased with fish size; larger bluegills ate more chironomid and trichopteran
larvae, ephemeropteran nymphs, winged insects, detritus (unidentifiable organ-
ic materials), and miscellaneous materials (mostly unidentified larval aquatic
insects and plants). Chironomid larvae, detritus, and miscellaneous materials
were the primary foods of bluegills larger than 100 mm.
Although diets changed seasonally, chironomid larvae, zooplankton, detritus,
and miscellaneous materials were always among the most frequently eaten
foods (Figure 3). Ephemeropteran nymphs also were important in winter,
winged insects in summer and fall, and amphipods in fall.
Chironomid larvae, zooplankton, and miscellaneous materials were major
foods of fish in all reaches (Figure 4). Detritus was also an important food item
everywhere except in SJR-6. Fish from upstream reaches (SJR-1, MR-1 ) fed more
heavily on trichopteran larvae and ephemeropteran nymphs than did those from
most downstream reaches; however, trichopteran larvae also were important in
MR-2. Amphipods were most important as forage in SJR-4, SJR-5, and Salt
Slough, whereas winged insects were important only in SJR-3 and SJR-5.
232
CALIFORNIA FISH AND GAME
<25mm, N = 49
26-50mm, n = 437
Winged
Insects
5l-IOOmm,N = 784
>IOOmm, N = 330
Winged
Insects
Mollusks
BLUECILL FOODS:
Amphlpods
Mollusks
Detritus
Miscellaneous
/ / ^ / /
/■/,'//
/ / / / ^
Chironomid larvae
m
~\
Trichopteran larvae
:J
Ephemeropteran nymphs
w^
Winged Insects
WW
Zooplankton
FIGURE 2. Food of various size classes of bluegills, based on unweighted annual mean damp-dry
biomass from eight reaches on the San Joaquin and Merced rivers, and Salt Slough.
Food Overlap Among Reaches
Indices of food overlap between pairs of reaches were calculated only for fish
longer than 25 mm. If one arbitrarily assumes that Cx > 0.70 represents signifi-
cant overlap, there were 20 overlaps between reaches (Table 4).
SAN JOAQUIN VALLEY BLUECILLS
233
Food overlap occurred between the two upstream reaches (SJR-1, MR-1),
with one reach (SJR-1) also overlapping a downstream reach (MR-2). Except
for MR-2, all downstream reaches showed significant overlap; MR-2 overlapped
only SJR-3, SJR-4, and SJR-5. These results demonstrate that, for the most part,
the diets of bluegills differed between upstream and downstream reaches.
However, diets in MR-2 consisted of foods characteristic of both upstream and
downstream reaches.
Winter, N = 290
Spring, N = 279
Winged
Insects
Amphipods
Sumnner, N = 706
Fall, N = 325
Amphipods
BLUECILL FOODS:
Chironomid larvae
Trichopteran larvae
Ephemeropteran nymphs I I
Winged insects
Zooplankton
Amphipods
Mollusks
Detritus
Miscellaneous
Mollusks
TTrr.
/ / 7 / .
/ f / / / .
FIGURE 3. Seasonal food habits of bluegills, based on unweighted mean damp-dry biomass of four
total length classes ( <25, 26-50, 51-100, and > 100 mm) of fish from eight reaches
on the San Joaquin and Merced rivers, and Salt Slough.
234
CALIFORNIA FISH AND GAME
SJR-I.N = 34I SJR-2. N=I52
Trichopteran
larvae
SJR-3.N=82
Amp hi pods
Trichopteran
larvae
Ephemeropteran
nymphs
SJR-4. N = 508 SJR-5.N=96
Amphipods
Trichopteran
larvae
SJR-6.N=I40
Winged
insects
Salt Slough. N = I5
_ _ Amphipods
Ephemeropteran
nymphs
MR-|.N = I32 MRz2,N5l34
_,..^^ \~Ephemerop/eran
insects
Amphipods
BLUECILL FOODS:
Chironomid larvae I 1
Trichopteran larvae ^^H
Ephemeropteran nymphs I I
Winged insects ^^^
Zooplankton
Amphipods
MoMusks
Detritus
Miscellaneous
ED
□
FIGURE 4.
Annual food of bluegills from eight reaches on the San Joaquin and Merced rivers, and
Salt Slough. Based on unweighted means (damp-dry biomass) of four total length
classes ( <25, 26-50, 51-100, and > 100 mm) of fish.
Food in Relation to Environmental Characteristics
Correlation analysis revealed that stomachs were fuller and contained a higher
diversity of forage taxa in environments characterized by clear water, weak
buffering capacity, and low levels of total P (Table 5). Bluegill stomachs were
also fuller in areas with low conductivity and NH3-N concentrations. When the
fullness and diet diversity indices were compared with the standing crop and
diversity of benthic macroinvertebrates, only the two diversity indices were
significantly correlated (r = 0.85, df = 7, P < .01 ).
SAN JOAQUIN VALLEY BLUECILLS 235
TABLE 4. Annual Food Overlap (Cx) among Bluegill > 25 mm TL for Pairs of Reaches on
the San Joaquin and Merced Rivers, and Salt Slough.
Salt
Reach* SJR-J S/R-2 SJR-3 SJR-4 SjR-5 SJR-6 Slough MR-1 MR-2
SJR-1 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
SJR-2 1.00 0.97 0.93 0.71 0.93 0.89 0.28 0.67
S)R-3 1.00 0.97 0.77 0.92 0.93 0.32 0.73
SJR-4 1.00 0.84 0.92 0.96 0.32 0.76
SJR-5 1.00 0.77 0.84 0.52 0.82
SJR-6 1.00 0.84 0.21 0.67
Salt Slough 1.00 0.36 0.68
MR-1 1.00 0.59
MR-2 1.00
* See Figure 1 for names and locations of reaches.
TABLE 5. Product-moment Correlation Coefficients Describing Relations between Environ-
mental Variables (Annual Means for Each Reach) and the Mean Annual Indices
of Stomach Fullness (C,) and Diet Diversity (d) for Each Reach.* +
Environmental variable C d
Physical
Water temperature —0.44 —0.60
Conductivity —0.77* —0.60
Turbidity -0.20 —0.22
Sediment fineness 0.32 0.52
Chemical
Dissolved oxygen 0.1 2 0.01
pH —0.57 —0.40
Total alkalinity -0.82** -0.72*
NH3-N -0.82** -0.12
NO^-I-NO'-N —0.42 —0.49
Total N —0.69 —0.51
Ortho-PO' —0.60 —0.65
Total P -0.72* -0.76*
• Symbols: *, P < .05;**, P < .01.
+ Degrees of freedom (df) = 7 except for NH^-N, NO'-l-NO'-N, total N, ortho-PO^ and total P, where df = 6.
Age, Growth, and Relative Weight
Age and Growth
New annuli were visible on scales of bluegills collected between midwinter
and late spring. New annuli first occurred on the outer margins of scales in
January 1981 in both SJR-4 (1 of 37 fish sampled) and SJR-6 (9 of 31 fish
sampled), and in March at SJR-1 (2 of 8 fish sampled). Annulus formation was
completed by April in all reaches except SJR-4 (44 of 45 fish sampled had new
annuli), where annulus formation continued through May.
The body-scale relations of 4,862 bluegills were well described by simple
linear equations fitted by least squares; r^ values for the different reaches ranged
from 0.82 to 0.97. Intercepts ranged from 16.3 mm at both SJR-3 and SJR-4 to
24.0 mm at Salt Slough. Because the values varied so little, the unweighted mean
of all intercepts, 19.0 mm, was used to back calculate total lengths at the end
of each year of life; this value compares favorably with the standard value of
20 mm proposed by Carlander (1982).
236 CALIFORNIA FISH AND CAME
Young-of-the-year were captured in all reaches; fish < 25 mm long entered
the catch in June or July. Maximum ages of bluegills captured ranged from 3 yr
(i.e., fish in their fourth growing season) at SJR-3 and Salt Slough, to 5 yr at SJR-1
andSJR-2 (Table 6).
In general, growth rates for males and females were similar at all reaches (i.e.,
there were few significant differences in the mean total lengths attained by males
and females after each year of life). However, there were three exceptions: age
II females were larger than males in SJR-6 (t = -2.13, df = 38, P < .05) and
in MR-2 (t = —3.29, df = 30, P < .01); and age III males were larger than
females in SJR-4 (t = 2.20, df = 12, P < .05) . These few sexual differences were
disregarded in our evaluation of overall growth histories.
The back calculated growth of 1,825 bluegills (sexes combined) ranged from
about 39 to 47 mm at annulus I, 72 to 101 mm at annulus II, 89 to 139 mm at
annuluslll, 145 to 167 mm at annulus IV, and 165 to 168 mm at annulus V (Table
6). Mean lengths attained after each year of life were not significantly different
(P > .05) among reaches.
Annual growth increments were inversely correlated with fish age (r =
—0.72, df = 29, P < .01 ), indicating that growth rates decreased among older
fish. Further analysis showed that fish from populations with rapid growth during
the first year of life also grew rapidly during their second year (r = 0.47, df =
29, P < .01 ); however, growth rates during the third year were not correlated
with second year growth (r = 0.03, df = 20, P > .05). Growth in the fourth
year was negatively correlated with growth in the third year (r = —0.68, df =
8, P < .05), suggesting that large fish (i.e., fish that grew rapidly during their first
three years) grew more slowly than smaller fish of the same age.
Relative Weight
In general, sex-related differences for W, were negligible. Only 2 of 55 monthly
comparisons of W, values for male and female bluegills were significantly differ-
ent: females were in slightly better condition (i.e., heavier) than males of similar
length at MR-2 in January 1981 (t = -2.21, df = 12, P < .05), and males were
in better condition than females at MR-1 in July 1981 (t = 3.27, df = 11, P <
.01).
Relative weight was not correlated with length at time of capture (r = 0.19,
df = 32, P > .05) or age (r = 0.16, df = 32, P > .05). In addition, even though
the mean W, for different reaches ranged from 96 at SJR-6 to 111 at SJR-2, the
differences were not statistically significant (one-way ANOVA, Fa 25 = 2.33, P
>.05).
Growth, Relative Weight, and Environmental Variables
With two exceptions, physicochemical characteristics (see Table 1 for specif-
ic variables) and biological characteristics (C, and other indices given in Tables
2-3) were not significantly correlated with either growth rate or W,. The two
exceptions were NH3— N vs. total length of bluegills at age IV (r = 0.798, df =
5, P < .05) and Q of fish > 100 mm long vs. fish length at age IV (r = -0.889,
df = 5, P < .01).
SAN JOAQUIN VALLEY BLUECILLS
237
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238 CALIFORNIA FISH AND GAME
DISCUSSION
There is little doubt that irrigation activities have caused a general deteriora-
tion of the aquatic habitat on the San Joaquin Valley floor. Many of the physico-
chennical differences between upstream and downstreann reaches noted in the
San Joaquin and Merced rivers — e.g., temperature, conductivity, turbidity, dis-
charge, sediment size composition, total alkalinity, and dissolved nutrients (Ta-
ble 1 and Saiki 1984) — could influence the occurrence and abundance of
stream-dwelling invertebrates (Hynes 1970), and may explain the lower stand-
ing crops and diversity of benthic macroinvertebrates at the downstream
reaches (Table 2). In the Merced River, Sorenson and Hoffman (1981 ) attribut-
ed upstream to downstream decreases in the abundance (numbers of individu-
als) and diversity of benthic invertebrates to changes in substrate composition
(upstream, the substrate was largely mixed gravel and sand; downstream, fine
sand and silt). Studies conducted in other river systems (Dance and Hynes 1980,
Welch et al. 1977) have shown that drainage from agricultural lands causes
instream environmental modifications — intermittent flows, heavier sediment
and nutrient loads, higher summer temperatures, and pesticide contamination —
that may reduce the diversity of the macroinvertebrate community, decrease the
standing crop, or both.
Less certain is whether environmental changes from irrigation activities have
influenced the fish fauna. Food, growth rate, and body condition are three
biological characteristics of fish populations that can be affected by changes in
the aquatic environment (Lagler, Bardach, and Miller 1962; Bennett 1971; War-
ren 1971).
Food
Aquatic invertebrates are usually the most important food items in the diets
of bluegills. Although small bluegills may feed almost exclusively on planktonic
Crustacea (Werner 1969; Hall, Cooper, and Werner 1970; Siefert 1972), an
inverse relation typically exists between bluegill size and the percentage of
microcrustacea in their diet (Hall et al. 1970). In larger bluegills, aquatic insect
larvae and other macroinvertebrates typically constitute the primary forage, and
flying insects, small fish, fish eggs, and plant material rank second (Goodson
1965, Turner 1966). Keast (1979) stated that bluegills are generalized feeders
that forage on individual taxa according to their occurrence in the environment.
However, Keast also noted that exceptions occur; for instance, even though
oligochaetes are usually abundant in the benthos, they are rarely found even in
the stomachs of generalists.
The important role that macroinvertebrates play in the diets of generalized
feeders such as the bluegill suggests that major differences in the benthic fauna
should be reflected in their food habits. Aquatic insects that were abundant at
upstream reaches (e.g., Trichoptera, Ephemeroptera) in the Merced and San
Joaquin rivers but scarce or absent downstream (Sorenson and Hoffman 1981;
M.K. Saiki, unpub. data) were also important as bluegill foods only at upstream
reaches (Figure 4). Longitudinal patterns in the occurrence of benthic taxa also
seem to explain the upstream-downstream differences noted in the analysis of
food overlaps (Table 4). Perhaps the clearest evidence of association between
species composition in the benthos and diets, however, was the significant
correlation (r = 0.85, df = 7, P < .01 ) between benthic diversity (Table 2) and
SAN JOAQUIN VALLEY BLUEGILLS 239
the diversity of foods eaten (Table 3). These results suggest that the composition
of the benthic fauna constrains the variety of foods eaten by bluegills.
Neither the standing crop nor the diversity of benthic invertebrates v^as cor-
related with the stomach fullness index (standing crop of benthos vs. Q, r =
0.52, df = 7, P > .05; benthic d vs. C„ r = 0.38, df = 7, F > .05), suggesting
that the total benthic fauna did not limit the amount of food eaten by fish.
According to Hall etal. (1970), theability of bluegills to use zooplankton as food
under conditions of high prey (= zooplankton) density could compensate for
vicissitudes in benthic production. In downstream reaches, where benthic foods
were less abundant (Table 2), bluegills apparently supplemented their diets by
foraging on alternate prey (e.g., zooplankton and winged insects), thereby
maintaining a stomach fullness index that was not significantly different from that
for fish from upstream reaches (F677 = 0.98, P > .05).
Age, Growth, and Relative Weight
Scott and Grossman (1973) stated that the maximum age of bluegills appears
to be 8-10 yr. However, Garlander (1977) noted that bluegills up to 11 years
old have been reported, based on ages determined from scales. Moyle (1976)
mentioned that a large bluegill (230 mm) in Galifornia is likely to be 8-9 yr. old.
Maximum ages of bluegills captured during our study ranged from 3 to 5 yr.
(Table 6), indicating relatively short life spans particularly downstream in SJR-3
and Salt Slough.
According to nationwide data summarized by Garlander (1977), bluegills
typically attain total lengths of 53 mm by the end of their first year, 95 mm by
the second year, 128 mm by the third year, 153 mm by the fourth year, and 173
mm by the fifth year. Moyle (1976) indicated that, in general, growth rates in
Galifornia lakes and reservoirs are similar to those of bluegills in the midwestern
United States, but slower than those of bluegills in the South. Growth of bluegills
that we collected from lotic habitats on the San Joaquin Valley floor was general-
ly slower than the average for lentic populations from Galifornia (Table 7). To
our knowledge, growth histories of populations from other lotic habitats in
Galifornia have not been published.
Previous attempts to relate growth rates of fishes, including bluegills, to
physicochemical and biological characteristics have generally met with only
limited success. Laboratory studies (e.g., Lemke 1977, Beitinger and Magnuson
1979) demonstrated a close link between water temperature, the abundance
and quality of the food supply, and the growth of bluegills. In the field, average
growth has been correlated with total carbonates, total dissolved solids, and
plankton abundance (Eddy and Garlander 1940), turbidity (Buck 1956), and pH
(Stockinger and Hays 1960, cited by Garlander 1977; Gash and Bass 1973).
However, Ridenhour (1960) reported no relation between environmental con-
ditions and either year class success or growth of bluegills in an Iowa lake over
an 8-yr. period, except that growth was usually better when aquatic vegetation
was more abundant. Ricker (1942) also found no association in several Indiana
lakes between bluegill growth and size of lake, average depth, transparency of
water, abundance of weeds and bottom food organisms, or abundance of preda-
ceous or competing fish.
Bennett (1971 ) stated that rapid growth and high body condition (K factor,
a measure of "plumpness" similar to WJ of fish are usually related, although
relatively rapid growth seems to be associated in some locations with moderate-
240 CALIFORNIA FISH AND GAME
ly low condition at least during part of the year. However, Buck and Thoits
(1970) and Cooper, Wagner, and Krantz (1971 ) indicated that condition factors
may be poor indicators of growth in length when measured over only a short
period of time. A few studies have reported associations between bluegill condi-
tion and environmental variables such as temperature (Proffitt and Benda 1971,
McNeeley and Pearson 1974), turbidity and discharge (Proffitt and Benda
1971), and the abundance of food (Morgan 1958, Wohlschlag and Juliano
1959).
In our study, growth rates and W, of bluegills did not differ significantly among
the reaches sampled. In addition, growth and W, were generally not correlated
with physicochemical variables, the standing crop and diversity of benthic mac-
roinvertebrates, or the stomach fullness index and diet diversity.
One reason for the inconsistent results of present and previous attempts to
correlate growth with environmental data may be the diversity of variables that
can influence growth under field conditions (Carlander 1966). In addition, the
relations between many environmental and biological variables may not be
linear or even monotonic (Green and Vascotto 1978). Another possibility is that
population density, a parameter that we did not measure, may be more impor-
tant than any other single factor as a regulator of individual growth rates; this
relation has been documented by numerous investigators (e.g., Parker 1958,
Cooper et al. 1971, Wiener and Hanneman 1982) for bluegill populations in
ponds and small lakes. To our knowledge, similar relations between population
density and growth of bluegill have not yet been demonstrated for lotic systems
such as those we sampled. However, Parsons and Benson (1960, cited by
Carlander 1977) reported increased growth of bluegills after fertilization of a
portion of the Obed River, Tennessee, which suggests interactions between the
food supply and population density.
Carlander (1966, 1977) proposed that environmental factors may control only
the maximum biomass of fish that can be supported in a given habitat (i.e., the
carrying capacity), and that potential growth of the biomass by recruitment or
growth of individuals is determined by the degree to which the biomass is below
carrying capacity. If Carlander's hypothesis is correct, relations between envi-
ronmental factors and growth of bluegills are indirect, and significant correla-
tions are unlikely if the populations under investigation are at or near their
carrying capacities.
IMPLICATIONS FOR MANAGEMENT
Despite mounting evidence that lotic environments are greatly modified by
return flows and other by-products of irrigated agriculture, the effects of these
modifications on fish populations are still poorly understood. Of several bluegill
life history characteristics that we measured (i.e., food, growth, and relative
weight), only food appeared to be influenced by environmental changes. The
considerable flexibility or adaptiveness that characterizes many freshwater
fishes (e.g., Larkin 1956, Le Cren 1965), especially bluegills, that allows them to
modify their population densities and growth rates probably explains our inabili-
ty to detect effects on growth and relative weight. However, measurable effects
on these characteristics may eventually occur if environmental degradation in
the lower San Joaquin River approaches the tolerance limits of this species.
SAN JOAQUIN VALLEY BLUECILLS
241
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242 CALIFORNIA FISH AND CAME
Although much remains to be learned about how fish populations are affected
by irrigated agriculture, alternative farming practices are available or might be
devised to lessen potential impacts and perhaps even enhance fish and wildlife
habitats. Researchers are currently examining ways to reduce the contaminant
load of return flows (e.g., Loehr 1979). In the San Joaquin Valley, construction
of a drainage canal has been proposed to collect and dispose of irrigation
wastewater directly into the Sacramento-San Joaquin Delta, thereby reducing
inputs to the San Joaquin River (Hanson 1982a, 19826). The use of return water
is also being considered for marsh development (Gilmer et al. 1982) and for
aquaculture (Monaco, Brown, and Gall 1981).
ACKNOWLEDGMENTS
We thank D. Cacela, T. Takagi, R. Nakamoto, D. Hartmann, and E. McClary
for assistance in the field; and J. Fairchild, S. Finger, and M. Henry for critically
reviewing the manuscript and making many useful suggestions.
LITERATURE CITED
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of fish production in fresh waters. IBP Handbook No. 3, Blackwell Scientific Publications, Oxford.
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Beland, R.D. 1954. Report on the fishery of the Lower Colorado River: the Lake Havasu fishery. Calif. Dep. Fish
Game, Inland Fish. Admin. Rep. No. 54-17, 42 pp.
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York. 375 pp.
Berg, J. 1979. Discussion of methods of investigating the food of fishes, with reference to a preliminary study of
the prey of Gobiusculus flavescens (Gobiidae). Mar. Biol., 50:263-273.
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Brown, D., E.E. Miller, and C.E. von Geldern, Jr. 1977. Detection of delayed annulus formation among bluegill,
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Bruns, P.M. 1958. Seasonal changes in growth rates of bluegill (Lepomis macrochirus, in Felt Lake. Thesis, Stanford
Univ., Stanford, Calif. 83 pp.
Buck, D.H. 1956. Effects of turbidity on fish and fishing. N. Am. Wildl. Nat. Resour. Conf., Trans., 21:249-261.
Buck, D.H., and C.F. Thoits III. 1970. Dynamics of one-species populations of fishes in ponds subjected to cropping
and additional stocking. III. Nat. Hist. Surv. Bull., 30(2):68-165.
California Department of Water Resources. 1960. Lower San Joaquin Valley water quality investigation. Calif. Dep.
Water Resour., Bull. No. 89. 189 pp.
1969. Lower San Joaquin River water quality investigation. Calif. Dep. Water Resour., Bull. No. 143-5.
207 pp.
Carlander, K.D. 1966. Relationship of limnological features to growth of fishes in lakes. Verb. Int. Verein. Limnol.,
16:1172-1175.
1977. Handbook of centrarchid fishes of the United States and Canada. Iowa State Univ. Press,
Ames. 431 pp.
_1982. Standard intercepts for calculating lengths from scale measurements of some centrarchid and
percid fishes. Am. Fish. Soc, Trans., Ill (3):332-336.
Cooper, E.L., C.C. Wagner, and C.E. Krantz. 1971. Bluegills dominate production in a mixed population of fishes.
Ecology, 52(2):280-290.
Dance, K.W., and H.B.N. Hynes. 1980. Some effects of agricultural land use on stream insect communities. Environ.
Pollut., Ser. A, 22:19-28.
Eddy, S., and K.D. Carlander. 1940. The effect of environmental factors upon the growth rates of Minnesota fishes.
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Emig, j.W. 1966. Bluegill sunfish. Pages 375-392 in A. Calhoun, ed. Inland fisheries management. Calif. Dep. Fish
Game, Sacramento, Calif.
SAN JOAQUIN VALLEY BLUEGILLS 243
Fast, A.W., L.H. Bottroff, and R.L. Miller. 1982. Largemouth bass, Micropterus salmoldes, and bluegill, Lepomis
macrochirus, growth rates associated with artificial destratification and threadfin shad, Dorosoma petenense,
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Cash, S.L., and J.C. Bass. 1973. Age, growth and population structures of fishes from acid and alkaline strip-mine
lakes in southeast Kansas. Kans. Acad. Sci., Trans., 76(1):39-50.
Cilmer, D.S., M.R. Miller, B.D. Bauer, and J.R. LeDonne. 1982. California's Central Valley wintering waterfowl;
Concerns and challenges. N. Am. Wildl. Nat. Resour. Conf,, Trans., 47:441-452.
Coodson, L.F. 1965. Diets of four warmwater game fishes in a fluctuating, steep-sided California reservoir. Calif.
Fish Came, 51(4):259-269.
Green, R.H., and C.L. Vascotto. 1978. A method for the analysis of environmental factors controlling patterns of
species composition in aquatic communities. Water Res., 12:583-590.
Hall, D.J., W.E. Cooper, and E.E. Werner. 1970. An experimental approach to the production dynamics and
structure of freshwater animal communities. Limnol. Oceanogr., 15(6):839-928.
Hanson, B.R. 1982a. Irrigation wastewater — a problem. Fremontia, 210(1 ):34-36.
19826. A master plan for drainage in the San )oaquin Valley. Calif. Agric, 36(5-6):9-11.
Hartmann, D.L., L.A. Hartmann, and C.E. von Celdern, Jr. 1978. A bluegill bibliography with abstracts and
annotations. Calif. Fish Game, Inland Fish. Admin. Rep. No. 79-1. 196 pp.
Hotes, F.L., and E.A. Pearson. 1977. Effects of irrigation on water quality. Pages 127-158 in E.B. Worthington, ed.
Arid land irrigation in developing countries: Environmental problems and effects. Pergamon Press, New York.
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Monaco 68:1-44.
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Keast, A. 1979. Patterns of predation in generalist feeders. Pages 243-255 in H. Clepper, ed. Predator-prey systems
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California. Calif. Fish Game, 50(4):271-291.
Lagler, K.F., J.E. Bardach, and R.R. Miller. 1962. Ichthyology. John Wiley & Sons, Inc., New York. 545 pp.
Larkin, P.A. 1956. Interspecific competition and population control in freshwater fish. Can. Fish. Res. Board, J.,
13(3):327-342.
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13:R&-105.
Lemke, A.E. 1977. Optimum temperature for growth of juvenile bluegills. Prog. Fish-Cult., 39(2):55-57.
Loehr, R.C. 1979. Potential pollutants from agriculture — an assessment of the problem and possible control
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PP-
244 CALIFORNIA FISH AND GAME
Proffitt, M.A., and R.S. Benda. 1971. Growth and movement of fishes, and distribution of invertebrates, related to
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NOTES 245
Calif. Fish and Came 7} (A): 24S-230 1985
NOTES
AN OBSERVATION OF REPRODUCTIVE BEHAVIOR IN A
WILD POPULATION OF AFRICAN CLAWED FROGS,
XENOPUS LAEVIS, IN CALIFORNIA.
Information on the status of the African clawed frog, Xenopus laevis, in
California is largely anecdotal (Mahrdt and Knefler 1972, 1973; St. Amant 1975;
Branson 1975; Branning 1979; LaRue 1980). Studies are few in nunnber (Munsey
1972; St. Amant, Hoover, and Stewart 1973; McCoid and Fritts 1980 a; b; B. J.
Zacuto, Calif. Fish and Game, unpubl.; Fritts and McCoid, Riverside Co. Fish and
Game Comm., unpubl.). This report provides the first observation of reproduc-
tive activity of the African clawed frog in the wild in California.
From summer 1974 through spring 1977 I studied populations of the African
clawed frog in southern California. Observations on reproductive behavior were
made at a pond 1.6 km southwest of Vail Lake, Riverside County (see McCoid
and Fritts 1 9806 for a site description ) . The African clawed frog typically inhabits
turbid waters (Picker 1980) and most of my study sites of the African clawed
frog in southern California were quite turbid. Possibly because of this, observa-
tions of reproductive behavior reported in the literature have been limited to
studies made in captivity. The pond in Riverside County was clear and provided
a unique opportunity to observe behavior under natural conditions.
I studied the population in Riverside County from April 1975 through March
1977. On 30 March 1976 I first noticed that males had begun calling and began
my behavioral observations then. Calling choruses began approximately Vj h
before sunset and continued after dark, although an occasional call was heard
during the day. The African clawed frogs called from late March through early
June, but actual reproduction was not seen until mid-April. Eggs and larvae were
collected in this pond between 22 April and 20 May. The estimated peak of
calling intensity occurred in April and May.
During the peak calling period, choruses could be heard from 10 to 15 m from
the water. The waters' edge could be approached without caution as reproduc-
tive activity apparently overroad evasive activity. Ordinarily, during the rest of
the year approaches had to be made rather stealthily for any observation. After
dark, observations were conducted with the aid of flashlights and these evoked
no apparent response. Most African clawed frogs observed were quiescent with
only short sporadic movements and rare feeding activity. However, movement
close to a male (easily differentiated, as males are smaller than females) by
another frog (of either sex) elicited a chase, this being given up in less than a
meter if not caught. If capture was effected and a male amplexed another male,
release was almost immediate. Picker (1980) reported a male release call which
accounts for brevity of male-male encounters. Females responded two different
ways when amplexed.
First, the female and male would continue swimming with occasional stops
in vegetation. At these stops, their feet would slightly twitch and then pump two
to ten times in 2 to 3 s. This sequence was followed by a resting period and
repeated (usually in a different clump of vegetation). The longest period of
246 CALIFORNIA FISH AND GAME
observation was 10 min for one pair before being lost in vegetation. Bles (1905)
reported behavior very similar to this in the laboratory with observed oviposi-
tion.
The other response was where the female initiated a rigor stance immediately
after being amplexed. Picker (1980) described this as the reaction of a non-
responsive female to a male. Perhaps these females had recently laid eggs and
were unable to oviposite. The female would assume a rigid position with her legs
extended completely and back slightly arched. A male would continue amplex-
ing a tonic female and swim around with her but generally released her within
1 min. The female would then drift to the bottom and remain rigid from 5 s to
2 min.
Males would respond to movement in front of them. They could easily be
enticed to amplex my hand by slowly moving it in front of them under water.
At one time a California toad, Bufo boreas, was observed to be amplexed by an
African clawed frog for in excess of 1 h until I disturbed them.
ACKNOWLEDGMENTS
I thank the Riverside County Fish and Game Commission for partial support
of field work. For assistance in the field, I thank D. Ruth, C. Crumly, and H. Snell.
T. Fritts provided ample guidance and field assistance.
LITERATURE CITED
Bles, E. J. 1905. The life-history of Xenopus laevis, Daud. Trans. Roy. Soc. Edinburgh. 41: 789-821.
Branning, T. 1979. Frog wars. National Wildlife., 17(2): 34-37.
Branson, B. A. 1975. Claude WHO? Another unwanted species. National Parks Conserv. Mag., )une 1975: 17-18.
LaRue, L. 1980. The frog that's eating California. Texas Flyer., 9(4); 52-53.
Mahrdt, C. R. and F. T. Knefler. 1972. Pet or pest? The African clawed frog. Environ. Southwest., 446: 2-5.
1973. The clawed frog — again. Environ. Southwest., 450: 1-3.
McCoid, M. ). and T. H. Fritts. 1980a . Notes on the diet of a feral population of Xenopus laevis (Pipidae) in
California. Southwest. Nat., 25: 272-275.
19806 . Observations of feral populations of Xenopus laevis (Pipidae) in southern California. Bull.
So. Calif. Acad. Sci., 79: 82-86.
Munsey, L. 1972. Salinity tolerance of the African pipid frog, Xenopus laevis. Copeia, 1972: 584-586.
Picker, M. 1980. Xenopus laevis (Anura:Pipidae) mating systems — a preliminary synthesis with some data on the
female phonoresponse. S. Afr. J. Zool., 15: 150-158.
St. Amant, J. A. 1975. Exotic visitor becomes permanent resident. Terra., 13(4): 22-23.
, F. Hoover, and C. Stewart. 1973. African clawed frog, Xenopus laevis (Daudin), established in
California. Calif. Fish Game, 59: 151-153.
— Michael j. McCoid. Department of Wildlife & Fisheries Sciences, Texas A&M
University, College Station, Texas 77843. Accepted for publication December
1984.
PARASITES OF THE SACRAMENTO PERCH, ARCHOPLITES
INTERRUPTUS
The Sacramento perch, Archoplites interruptus, is the only centrarchid native
west of the Rocky Mountains. It is endemic to the lower Sacramento-San Joaquin
drainage system. Clear Lake, and the Pajaro and Salinas River systems of Califor-
nia. Habitat disruptions and the introduction of competing centrarchids have
resulted in a decline in the abundance of the Sacramento perch in its native range
(Aceituno and Nicola 1976, Moyle 1976, Vanicek 1980). However, it is not in
danger of becoming extinct, as it has been successfully introduced in many other
waters.
NOTES 247
Murphy (1948); Mathews (1962 and 1965), Moyle, Mathews, and Bonderson
(1974); and Aceituno and Vanicek (1976) reported on the life history of the
Sacramento perch. However the parasites of this unique species have received
little attention. The Sacramento perch was among the species examined in the
general fish parasite surveys of northern California waters by Haderlie (1953)
and Edwards and Nahhas (1968). This study provides additional information on
the parasites of the Sacramento perch by examining the helminth parasites of
three populations from different environments and comparing their species com-
position and infestation rates.
METHODS AND MATERIALS
Sacramento perch used in this study were collected from Lake Greenhaven
(Sacramento County), West Valley Lake (Modoc County), and Crowley Lake
(Mono County). Lake Greenhaven is a 24-ha artificial lake at an elevation of 15
m, now surrounded by urban development. Water temperatures range from 7''C
in winter to 23°C in summer. Fish species present include golden shiner,
Notemigonus crysoleucus; goldfish, Carassius auratus; carp, Cyprinus carpio;
channel catfish, Ictalurus punctatus; mosquitofish, Cambusia affinis; Sacramento
perch; bluegill, Lepomis macrochirus; green sunfish, L. cyanellus; white crappie,
Pomoxis annularis; and largemouth bass, Micropterus salmoides.
West Valley Lake is a 388-ha reservoir at an elevation of 1331 m located in
the South Pit River drainage system of the Modoc Plateau. It is surrounded by
pinon pines, Pinus monophylla. Water temperatures range from 5°C in winter to
over 20°C in summer. Sacramento perch were introduced in 1972. Other fish
species in this lake include rainbow trout, Salmo gairdneri; brown trout, 5. trutta;
tui chub, Cila bicolor; Sacramento sucker, Catostomus occidentalis; Tahoe
sucker, C. tahoensis; white catfish, Ictalurus catus; and brown bullhead, I.
nebulosis.
Crowley Lake is in the Owens River drainage at an elevation of 2067 m. It is
a reservoir of about 2112-ha surrounded by sage brush, Artemesia tridentata.
Water temperatures range from near 0°C in winter up to 20''C in summer. Sacra-
mento perch were introduced (unauthorized) about 1970. Rainbow and brown
trout also occur here.
Of these study lakes, only Lake Greenhaven is located within the native range
of the Sacramento perch.
From 17 to 25 Sacramento perch were collected from each lake during the
spring and summer of 1979. Fish were collected with gill nets at Lake Greenhav-
en and West Valley Lake, and with hook and line at Crowley Lake. We immedi-
ately placed the fish on ice and transported them to the laboratory where they
were dissected immediately, or frozen and dissected later. Each fish was
weighed and measured (fork length), and surveyed for ectoparasites before
being dissected. Scale samples were taken for age determination. Condition
factors were calculated with the equation C = W X 10 ^, where W =
L3
weight in grams and L = fork length in millimetres.
Organs (mesentary, digestive tract, liver, gonads) of individual fish were
separated into different dishes and carefully teased apart. All parasites were fixed
in formal-acetic alcohol (FAA). The specimens were cleared with lactophenol
248
CALIFORNIA FISH AND CAME
and mounted wet. Specimens were identified with the aid of Hoffman (1967).
R. Toth, Associate Fish Pathologist, California Department of Fish and Game,
confirmed our identification of the parasites.
. RESULTS AND DISCUSSION
Characteristics of the fish sampled from the three lakes are presented in Table
1. Both sexes and several age groups were represented in all three samples.
TABLE 1. Characteristics of Sacramento Perch from Lake Greenhaven, West Valley Lake,
and Crowley Lake, California.
Average
condition
factor
Lake Greenhaven 1.8
West Valley Lake J 2.0
Crowley Lake 2.5
5ex.-
Range
M = Male
in length
F = Female
Age
(mm)
U = Unknown
class
120-150
F
19
IV-VIP
M
6
70-210
U
7
1 (6)
F
7
II (4)
M
3
III (4)
IV (2)
V (1)
180-260
U
5
II (2)
F
7
III (8)
M
9
IV (7)
V (1)
' Vanicek, C. D. (1980).
Only one species of parasitic helminth, Proteocephalus sp., was found in the
Lake Greenhaven fish (Table 2); all 211 specimens were plerocercoids which
we could not identify to species, but could be P. ambloplites. The gonads were
the organ most frequently parasitized (19 fish), followed by the digestive tract
(13 fish) and the liver (5 fish). Females had a higher infestation rate (10/fish)
than the males (4/fish).
In the West Valley Lake population, the only endoparasite found was Con-
tracaecum sp. All were larvae and could not be identified to species, but Hader-
lie (1953) has identified Contracaecum spiculigerum from the Sacramento
perch. This parasite occurred in 13 of the 17 fish, and averaged 18 individuals
per fish; most occurred in the mesentaries (Table 2). West Valley Lake fish were
parasitized externally by Lernaea sp.; the infestation rate ranged from one to five.
Two endoparasites were found in Crowley Lake fish: Contracaecum sp. and
Posthodiplostomum minimum. Contracaecum sp. was found in the intestines of
three fish; the mean infestation rate was one per fish. Ten fish were parasitized
with larval P. minimum, all of which occurred in the liver, with a mean infesta-
tion rate of eight.
Proteocephalus has not previously been reported for the Sacramento perch.
Hoffman (1967) reported the following parasites for the Sacramento perch:
Trematoda, Plagioporus serotinus and Urocleidus dispar; Nematoda, Contraca-
ecum spiculigerum; Crustacea, Lernea cyprinace. Edwards and Nahhas (1968)
found only P. minimum in Sacramento perch.
NOTES
249
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250 CALIFORNIA FISH AND GAME
The parasite fauna for the three Sacramento perch populations overlapped
very little, possibly reflecting the contrasting environments of the lakes. Noble
and Noble (1976) pointed out when fish are introduced to new regions their
original parasite fauna may be greatly affected by lack of intermediate hosts or
by unfavorable water conditions. Within time the host fish may acquire new
species of parasites.
The tapeworm Proteocephalus in bass causes fibrosis of the gonads that can
result in sterility. In small fish the wandering plerocercoids can cause death when
they damage vital organs, while in adult fish the plerocercoids produce adhe-
sions which can impair metabolism and reduce egg production (Hoffman 1967).
The Lake Greenhaven population is stressed and declining, as evidence by
recent reproductive failures, reduced growth, low condition factors, and de-
creased abundance (Vanicek 1980). The gonads were the most heavily parasit-
ized organ by Proteocephalus in the Lake Greenhaven fish, especially the
females; perhaps this parasite has contributed to the decline of Sacramento
perch at Lake Greenhaven.
ACKNOWLEDGMENTS
We are grateful to personnel of the California Department of Fish and Game
for assistance in this project, including R. Toth, E. P. Pister, D. M. Wong, V. L.
King, and W. D. Weidlein. Others who assisted were E. Goude, and C S. and
C. O. Staley.
LITERATURE CITED
Aceituno, M. E. and S. ). Nicola. 1976. Distribution and status of the Sacramento perch, Archoplites Interruptus
(Girard) in California. Calif. Fish Game, 62(4): 246-255.
Aceituno, M. E. and C. D. Vanicek. 1976. Life history studies of the Sacramento perch, Archoplites interruptus
(Girard) in California. Calif. Fish Game, 62(1): 5-20.
Edwards, S. R. and F. M. Nahhas. 1968. Some endoparasites of fishes from the Sacramento-San Joaquin Delta,
California. Calif. Fish Game, 54(4); 247-256.
Haderlie, E. C. 1953. Parasites of the freshwater fishes of northern California. University California Publ. Zool.,
57(5): 303^M0.
Hoffman, G. L. 1967. Parasites of North American freshwater fishes. University of California Press, Berkeley and
Los Angeles, 472 p.
Mathews, S. B. 1962. The ecology of the Sacramento perch, Archoplites Interruptus, from selected areas of
California and Nevada. Thesis, University California Library, Berkeley, 93 p.
1965. Reproductive behavior of the Sacramento perch. Copeia, 1965(2): 224-228.
Moyle, P. B. 1976. Inland fishes of California. University California Press, Berkeley and Los Angeles, 405 p.
Moyle, P. B., S. B. Mathews, and N. Bonderson. 1974. Feeding habits of the Sacramento perch, Archoplites
Interruptus. American Fish Society Trans., 103(2): 399-^K)2.
Murphy, G. I. 1948. A contribution to the life history of the Sacramento perch, Archoplites interruptus, in Clear
Lake, Lake County, California. Calif. Fish Game 34(3): 93-100.
Noble, E. R. and G. A. Noble. 1976. Parasitology, the Biology of Animal Parasites. Lea and Febiger, Philadelphia,
566 p.
Vanicek, C. D. 1980. Decline of the Lake Greenhaven Sacramento perch population. Calif. Fish Game, 66(3):
178-183.
— Cay C. Goude, U.S. Army Corps of Engineers, Sacramento, California, and C.
David Vanicek, Department of Biological Sciences, Calif State University, Sacra-
mento, Sacramento, California, 95819. Accepted for Publication January 1985.
251
BOOK REVIEW
CHARTGUIDE MEXICO WEST
By Ed Winlund, Jack West, Carolyn West, Charlie Davis, and Dan Gotshall; ChartGuide Ltd.,
Anaheim, CA; 1983; 76 p; $41.00 (14 by 20 inch, spiral bound).
Everything about ChartCuide Mexico West is impressive. The unusual 14 by 20 inch size of this
book with its inviting tropical scene on the cover immediately captures the eye. But the best part
is inside.
The guide covers the Pacific coast of Mexico from San Diego to Guatamala, including the oceanic
islands and the Gulf of California. It begins with the sections "Before You Go" and "Underway",
where much advice on dealing with the Mexican authorities, tourist cards, customs, insurance, and
the availability of parts is found. "Chart Interpretation" includes the instructions for using the guide.
The sections on "Navigation Electronics" and "Radio Communication" are the most complete
presentation of those subjects I have seen for any area. Other sections give a good overview on the
weather and sea conditions one might find off Mexico.
Most of the book is composed of reproductions of nautical charts illustrating stretches of coastline
or islands. Accompanying each chart there is a variety of useful information not often seen on
nautical charts, such as land mass shape sketches and pictures of local lighthouses. Many of the
islands and areas of particular interest are covered by individual inserts with greater detail. The guide
should be of valuable assistance in navigating the Mexican coast, but it should not be, as the authors
warn, the only source of navigation information.
Each chart is annotated with information pertinent to the locale, and includes specific chart
parameters, tide, assistance, and shoreline descriptions. Anecdotal stories and historical facts are
included, as well as the kinds of fishes and shellfish that may be found. All comments referring to
a particular chart appear on that chart or on the facing page. There is never any need to flip through
pages trying to match text with illustrations and charts.
The last sections list references, including personal comments, charts used, and navigational aides,
and a general index to subjects and locations. A nice feature is the inclusion of Spanish translations
of technical terms and locations throughout the guide. Such translations may be useful when
communicating with non-english speaking Mexicans.
The printing quality of ChartCuide Mexico West is clear and crisp which is good as up to six
columns of the fine print may be hard for some to read for very long, especially at sea. At $41.00,
the price is high, but I think it is a worthwhile investment for anyone traveling to Mexico, especially
yachtsmen. Divers and fishermen will find the guide quite useful, too — Peter L. Haaker
GUIDELINES FOR MARINE ECOLOGICAL SURVEYS: NEKTON
Prepared by the California Committee on Marine Ecological Survey Standards (C^MESS);
published by the California Sea Grant College Marine Advisory Program; Extension Sea Grant
Marine Adivsory Program; University of California, Davis, CA 95616; iv + 12 pp; $2.00
In 1969 the California Committee on Marine Ecological Survey Standards (C'MESS) began a
difficult and much needed task; i.e., organization of guidelines for marine ecological survey methods.
They planned a series of publications outlining and summarizing survey methods for biota in a variety
of marine habitats. The first publication outlines survey methods for nekton. The fishes and inverte-
brates comprising this functional group occupy a wide variety of habitats, distributions, abundances,
etc. Sampling gear and methods used to survey these organisms are, likewise, highly diverse.
Included are discussions on destructive sampling techniques (i.e., sampling without replacement)
using nets, traps, lines, and chemicals and the type of data, both physical and bioJogical, that should
be collected during sampling operations.
Use of SCUBA for assessment of nekton populations is also discussed. The most common meth-
ods, their application, advantages, and disadvantages are briefly described and summarized in a clear
and concise table for easy comparison.
The guidelines also provide a brief discussion of the potential sources of fishery landing data, as
well as a short description of pertinent statistical analysis techniques. A glossary of common ecologi-
cal terms and a list of references are included.
Standardization of techniques in ecological studies is one of the most crucial problems faced by
ecologists today. This booklet makes the first step to resolving these problems. While the details of
individual sampling programs must be worked out on a case by case basis, the guidelines provide
a starting place for all professional biologists and students alike. I eagerly await publication of the
rest of the series. At only $2.00 a copy, it is a must for all biologists' libraries. — Kenneth C. Wilson
252 CALIFORNIA FISH AND CAME •
INDEX TO VOLUME 71
AUTHORS
Barilotti, D. Craig, Ronald H. McPeak, and Paul K. Dayton: Experimental Studies on the Effects of Commercial Kelp
Harvesting in Central and Southern California Macrocystis pyrifera Kelp Beds, 4-20
Benville, Pete E., Jr., Jeannette A. Whipple, and Maxwell B. Eldridge: Acute Toxicity of Seven Alicyclic Hexanes
to Striped Bass, Morone saxatilis, and Bay Shrimp, Crangon franciscorum, in Seawater, 132-140
Bernard, Hannah J.: see Duffy and Bernard, 122-125
Bodkin, James L., Ronald |. Jameson, and Glenn R. Van Blaricom: Pup Production, Abundance, and Breeding
Distribution of Northern Elephant Seals on San Nicolas Island, Winter 1981, 53-55
Bond, Carl E., and Robert E. Olson: Northward Occurrence of the Opaleye, Cirella nigricans, and the Sharpnose
Seaperch, Phanerodon atripes, 56-57
Burton, Steve F.: see Conyea and Burton, 188
Butler, Robert A.: see Tegner and Butler, 150-163
Chesemore, David L.: see Warner and Chesemore, 184-185
Cohen, Yosef: see Dahlsten, Morrison, Rowney, Wilson and Cohen, 172-178
Collins, Joshua N., and Vincent H. Resh: Utilization of Natural and Man-Made Habitats by the Salt Marsh Song
Sparrow, Melospiza melodia samuelis (Baird), 40-52
Cook, Sid. F., and James Long: The Oxeye Oreo, Allocyttus folletti Myers, From The Bering Sea, 57
Cross, Jeffrey N., James Roney, and Gary S. Kleppel; Fish Food Habits Along a Pollution Gradient, 28-39
Custer, Thomas W., Elwood F. Hill, and Harry M. Ohiendorf: Effects On Wildlife of Ethyl and Methyl Parathion
Applied To California Rice Fields, 220-224
Dahlsten, Donald L., Michael L. Morrison, David L. Rowney, Marilyn Wilson, and Yosef Cohen: Bird Diets and
Prey Availability in The Western Sierra Nevada, California, 172-178
Dayton, Paul K.: see Barilotti, McPeak, and Dayton, 4-20
Deuel, Bruce: Experimental Lead Dosing of Northern Pintails in California, 125-128
Dhaenens, Mark A.: see Marsh and Dhaenens, 107-110
Duffy, John M., and Hannah |. Bernard: Milkfish, Chanos chanos (Forsskal, 1775), Taken in Southern California
Adds New Family (Chanidae) To The California Marine Fauna, 122-125
Ebert, David A.: Color Variation in the Sevengill Shark, Notorynchus maculatus Ayres, Along the California Coast,
58-59
Eldridge, Maxwell B.: see Benville, Whipple, and Eldridge, 132-140
Fancher, Jack M., see Zembal, Fancher, and Nordby, 164-171
Conyea, Gary P., and Steve F. Burton: Occurrence of a Juvenile California Lizardfish, Synodus lucioceps, in
Washington Waters, 188
Goude, Cay C, and C. David Vanicek: Parasites of the Sacramento Perch, Archoplites interruptus, 246-250
Haight, David R.: see Hill and Haight, 185-187
Hanson, Charles H., and Erik Jacobson: Orientation of Juvenile Chinook Salmon, Oncorhynchus tshawytscha, and
Bluegill, Lepomis macrochirus, to Low Water Velocities Under High and Low Light Levels, 110-113
Hassler, Thomas J.: see Okeyo and Hassler, 76-87
Hill, Elwood F.: see Custer, Hill and Ohiendorf, 220-224
Hill, Kevin and David R. Haight: Northward Range Extension For the Striped Marlin, 185-187
Hofmann, Paul: see McKibben and Hofmann, 68-75
Hopkins, Judith: see Jones, Johnson, and Hopkins, 116-117
Houk, James L.: see McCleneghan and Houk, 21-27
Jacobson, Erik: see Hanson and Jacobson, 110-113
Jameson, Ronald J.: see Bodkin, Jameson, and Van Blaricom, 53-55
Johnson, Robert R.: see Jones, Johnson, and Hopkins, 116-117
Jones, Lawrence L. C, Robert R. Johnson, and Judith Hopkins: Additional Records of Pronotogrammus multifas-
ciatus and Gempylus serpens from California, 116-117
Kleppel, Gary S.: see Cross, Roney, and Kleppel, 28-39
Leidy, Robert A.: Pugheadedness in the California Roach, Hesperoleucus symmetricus ( Baird and Girard ), 1 1 7-1 22
Long, James: see Cook and Long, 57
Marsh, Paul C, and Mark A. Dhaenens: Growth of Grass Carp, Ctenopharyngodon idella, in Artificial Central
Arizona Ponds, 107-128
McCleneghan, Kim, and James L. Houk: The Effects of Canopy Removal on Holdfast Growth in Macrocystis
(Phaeophyta; Laminariales), 21-27
McCoid, Michael J.: An Observation of Reproductive Behavior in a Wild Population of African Clawed Frogs,
INDEX TO VOLUME 71 253
Xenopus laevis, in California, 245-246
McKibben, Laurence A., and Paul Hofmann: Breeding Range and Population Studies of Comnr>on Snipe in Califor-
nia, 68-75
McPeak, Ronald H.: see Barilotti, McPeak and Dayton, 4-20
Morrison, Michael: see Dahlsten, Morrison, Rowney, Wilson, and Cohen, 172-178
Nordby, Christopher S.: see Zembal, Fancher, and Nordby, 164-171
Ohiendorf, Harry M.: see Custer, Hill, and Ohiendorf, 220-224
Okeyo, Daniel Okoth and Thomas J. Hassler: Growth, Food and Habitat of Age 0 Smallmouth Bass in Clair Engle
Reservoir, California, 76-87
Olson, Robert E.: see Bond and Olson, 56-57
Resh, Vincent H.: see Collins and Resh, 40-52
Rienecker, Warren C: An Analysis of Canvasbacks Banded in California, 141-149
Rienecker, Warren C: Temporal Distribution of Breeding and Non-Breeding Canada Geese From Northeastern
California, 196-209
Roest, Aryan I.: Determining The Sex of Sea Otters from Skulls, 179-183
Roney, James: see Cross, Roney, and Kleppel, 28-39
Rowney, David L.: see Dahlsten, Morrison, Rowney, Wilson, and Cohen, 172-178
Saiki, Michael K., and Christopher ). Schmitt: Population Biology of Bluegills, Lepomis macrochirus, in Lotic
Habitats on the Irrigated San Joaquin Valley Floor, 225-244
Schmitt, Christopher J.: see Saiki and Schmitt, 225-244
Seigel, Jeffrey A.: The Scalloped Hammerhead, Sphyrna lewini, in Coastal Southern California Waters: Three
Records Including The First Reported Juvenile, 189-192
Stewart, Brent S., and Pamela K. Yochem: Radio-Tagged Harbor Seal, Phoca vitulina richardsi, Eaten by White
Shark, Carcharodon carcharias, in the Southern California Bight, 1 1 3-1 1 5
Talent, Larry G.: The Occurrence, Seasonal Distribution, and Reproductive Condition of Elasmobranch Fishes in
Elkhorn Slough, California, 210-219
Tegner, Mia J., and Robert A. Butler: The Survival and Mortality of Seeded and Native Red Abalones, Haliotis
rufescens, on the Palos Verdes Peninsula, 150-163
Van Blaricom, Glenn R.: see Bodkin, Jameson, and Van Blaricom, 53-55
Vanicek, C. David: see Goude and Vanicek, 246-250
Villa, Nick A.: Life History of The Sacramento Sucker, Catostomus occidentalis, in Thomes Creek, Tehama County,
California, 88-106
Warner, Donald R., and David L. Chesemore: A Technique to Secure Small Mammal Livetraps Against Disturbance,
184-185
Whipple, Jeanette A.: see Benville, Whipple, and Eldridge, 132-140
Wilson, Marilyn: see Dahlsten, Morrison, Rowney, Wilson, and Cohen, 172-178
Yochem, Pamela: see Stewart and Yochem, 113-115
Zembal, Richard, Jack M. Fancher, and Christopher S. Nordby: Intermarsh Movements By Light-Footed Clapper
Rails Indicated In Part Through Regular Censusing, 164-171
SUBJECT
Abalones: The survival and mortality of seeded and native Red, on the Palos Verdes Peninsula, 150-163
Bass, smallmouth: Growth, food and habitat of age 0, in Clair Engle Reservoir, California, 76-87
Bass, threadfin: Additional records of, from California, 116-117
Bird: Diets and prey availability in the Western Sierra Nevada, California, 172-178
Bluegills: Population biology of, in lotic habitats on the irrigated San Joaquin Valley Floor, 225-244; Orientation
of juvenile chinook salmon and, the low water velocities under high and low light levels, 110-113
Canvasbacks: An analysis of banded, in California, 141-149
Carp, grass: Growth of, in artificial Central Arizona Ponds, 107-110
Fish: Food habits along a pollution gradient, 28-39
Fishes, elasmobranch: The occurrence, seasonal distribution, and reproductive condition of, in Elkhorn Slough,
California, 210-219
Frogs, African clawed: An observation of reproductive behavior in a wild population of, in California, 245-246
Geese, Canada: Temporal distribution of breeding and non-breeding, from Northeastern California, 196-209
Hammerhead, scalloped: The, in Coastal Southern California Waters: Three records including the first reported
juvenile, 189-192
Hexanes, alicyclic: Acute toxicity of seven, to striped bass and bay shrimp in Seawater, 132-140
254
CALIFORNIA FISH AND CAME
Lizardfish, California: Occurrence of a juvenile, in Washington waters, 188
Mackerel, Snake: Additional records of, from California, 116-117
Macrocystis: Experimental studies on the effects of commercial kelp harvesting in Central and Southern Califor-
nia, kelp beds, 4-20; The effects of canopy removal on holdfast growth in, 21-27
Mammal: A technique to secure small, livetraps against disturbance, 184-185
Marlin, striped: Northward range extension for the, 185-187
Milkfish, Chanos chanos (Forsskal, 1775): Taken in Southern California adds new family (Chanidae) to the
California marine fauna, 122-125
Opaleye: Northward occurrence of The, and The Sharpnose seaperch, 56-57
Oreo, oxeye: The, from the Bering Sea, 57
Otters, sea: Determining the sex of, from skulls, 179-183
Parathion, ethyl and methyl: Effects on wildlife of, applied to California rice fields, 220-224
Perch, Sacramento: Parasites of The, 246-250
Pintails, northern: Experimental lead dosing of, in California, 125-128
Rails, light-footed clapper: Intermarsh movements by, indicated in part through regular censusing, 164-171
Roach, California: Pugheadedness in the, 117-122
Salmon, chinook: Orientation of juvenile, and bluegill to low water velocities under high and low light levels,
110-113
Seal, harbor: Radio-tagged, eaten by white shark in the southern California bight, 113-115
Seals, northern elephant: Pup production, abundance, and breeding distribution of, on San Nicolas Island, Winter
1981, 53-55
Seaperch, sharpnose: Northward occurrence of the Opaleye and the, 56-57
Shark, sevengill: Color variation in the, along The California coast, 58-59
Snipe, common: Breeding range and population studies of, in California, 68-75
Sparrow, salt marsh song: Utilization of natural and man-made habitats by the, 40-52
Sucker, Sacramento: Life history of the, in Thomas Creek, Tehama, California, 88-106
Agelaius phoeniceus: 220-224
Allocyttus folletti myers: 57
Alosa sapidissima: 118
Ammonspiza maritima: 40
Ana americana: 144
Anas platyrhynchos: 220-224
Anthias gordensis: 116
Aphedoderus sayanus: 1 1 8
Archoplites interruptus: 246-250
Astrometis sertulifera: 152
Aythya valisineria: 141-149
Bairdiella chrysura: 118
Baccharis pilularis: 42
Branta candensis moffitti: 191-209
Branta candensis maxima: 203
Brevoortia tyrannus: 118
Callorhinus ursinus: 114
Carassius auratus: 102, 138, 247
Carcharodon carcharias: 113-115
Carpodacus purpureus: 175
Catharus guttatus: 175
Catostomus catostomus: 91
Catostomus commersoni: 92
Catostomus occidentalis: 88-106, 247
Catostomus tahoensis: 98, 247
Ceratostoma nuttali: 156
Certhia americana: 174
SCIENTIFIC NAMES
Chanos chanos: 122-125
Chen caerulescens: 144
Citharichthys sordidus: 28-39
Citharichthys stigmaeus: 28-39
Coccothraustes vespertinus: 175
Colinus virginianus: 222
Contopus borealis: 1-74
Contracaecum spiculigerum: 248
Corbicula fluminea: 227
Cottus asper: 102
Crangon franciscorum: 132-140
Ctenopharyngodon idella: 107-110
Cyanocitta stelleri: 174
Cynoscion nebulosus: 118
Cyprinus carpio: 102, 118, 247
Dendroica coronata: 175
Dendroica nigrescens: 175
Dendroica occidentalis: 175
Dendroica petechia: 175
Distichlis spicata: 41
Dorosoma petenense: 227
Esox lucius: 118
Empidonax hammondii: 175
Empidonax oberholseri: 175
Enhydra lutris: 179-183
Fulica americana: 167, 220-224
Frankenia grandifolia: 41
INDEX TO VOLUME 71
255
Gallinago gallinago delicata; 68-75
Cambusia affinis: 227, 247
Casterosteus aculeatus: 227
Cempylus serpens: 116-117
Gila bicolor: 247
Girella nigricans: 56-57
Grindelia humilis: 42
Cymnohorax mordax: 161
Haliaeetus leucorephalus: 88
Haliotis corrugata: 162
Haliotis discus discus: 160
Haliotis discus hannai: 160
Haliotis fulgens: 153
Haliotis gigantea: 160
Haliotis rufescens: 150
Haliotis sieboldi: 160
Hesperoleucus symmetricus: 117-122
Hysterocarpus traski: 102, 227
Ictalurus catus: 247
Ictalurus nebulosis: 247
Ictalurus punctatus: 247
Icelinus quadriseriatus: 28-39
)aumea carnosa: 41
Junco hyemalis: 175
Kellettia keiletti: 152
Lavinia exilicauda: 102
Lavinia symmetricus: 100
Lebistes reticulatus: 138
Lepomis cyanellus: 100, 227, 247
Lepomis macrochirus: 100, 110-113, 138, 227, 247
Lepomis microlophus: 227
Lepus californicus: 220-224
Lernea cyprinace: 248
Leucaspius delineatus: 118
Loxorhynchus grandis: 152
Macrocystis pyrifera: 4-20, 21-27
Melospiza melodia samuelis: 40-52
Menidia beryllina: 227
Micropterus dolomieui: 76-87
Micropterus salmoides: 76, 101-102, 118, 227, 247
Microstomus pacificus: 28-39
Mirounga angustirostris: 53-55, 113
Morone saxatilis: 118, 132-140, 227
Mugil cephalus: 122
Mus musculus: 220-224
Mustelus californicus: 210-219
Mustelus henlei: 210-219
Myadestes townsendi: 174
Myliobatis californica; 58, 155, 210-219
Mylopharodon conocephalus: 100, 227
Notemigonus crysoleucas: 138, 247
Notorynchus maculatus: 58-59
Octopus bimaculatus: 160
Octopus bimaculoides: 160
Oncorhynchus nerka: 76
Oncorhynchus tshawytscha: 110-113
Oporonis tolmiei: 175
Orthodon microlepidotus: 227
Panulirus interruptus: 152
Parophrys vetulus: 28-39
Parus rufescens: 174
Passerella iliaca: 175
Perca flavescens: 118
Phanerodon atripes: 56-57
Phanerodon furcatus: 56
Phasianus colchicus: 220-224
Pheucticus melanocephalus: 175
Phoca vitulina richardsi: 113-115
Pimephales promelas: 138, 227
Pipilo erythrophthalmus: 175
Piranga ludoviciana: 175
Pisaster giganteus: 152
Plagioporus serotinus: 248
Platyrhinoidis triseriata: 210-219
Pleuronichthys verticalis: 28-39
Pogonichthys macrolepidotus: 227
Pomatomus saltatrix: 118
Pomoxis annularis: 227
Pomoxis nigromaculatus: 227
Posthodiplostomum minimum: 248
Pronotogrammus multifasciatus: 116-117
Proteocephalus amblopiites: 248
Ptychocheilus grandis: 227
Rallus longirostris levipes: 164-171
Rallus longirostris obseletus: 169
Regulus satrapa: 174
Rhinichthys osculus: 102
Rhinobatos productus: 210-219
Roccus chrysops: 118
Rhomboplitesaurorubens: 118
Salicornia virginica: 41
Salmo gairdneri: 76, 102, 118, 247
Salmo salar: 38
Salmo trutta: 76, 118, 247
Salvelinus leucomaenis: 118
Scorpaena guttata: 161
Scorpaenichthys marmoratus: 155
Spartina foliosa: 41
Sphyrapicus ruber: 174
Sphyrna lewini: 189-190
Spizella passerina: 175 '
Symphurus atricauda: 28-39
Synodus lucioceps: 188
Tautoga onitis: 118
Tetrapterus audax: 185-187
Trachurus symmetricus: 58
Triakis semifasciata: 210-219
Triops longicaudatus: 220
256 CALIFORNIA FISH AND GAME
Turdus migratorius: 175 VIreo solitarius: 175
UrocleJdus dispar: 248 Wilsonia pusilla: 175
Urolophus halleri: 210-219 Xenopus laevis: 245-246
Vermivora ruficapilla: 175 Zaiophus californianus: 114
Vireo gilvus: 1 75 Zaniolepis latipinnis: 28-39, 1 1 8
Photoelectronic composition by
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INSTRUCTIONS TO AUTHORS
EDITORIAL POLICY
California Fish and Game is a technical, professional, and educational journal
devoted to the conservation and understanding of fish and wildlife. Original
manuscripts submitted for consideration should deal with the California flora and
fauna or provide information of direct interest and benefit to California researchers.
Authors may submit an original plus two copies, each, of manuscript, tables, and
figures at any time.
MANUSCRIPTS: Authors should refer to the CBE Siyle Manual (Fifth Edition) and a
recent issue of California Fisti and Game for general guidance in preparing their
manuscripts. Some major points are given below.
1. Typing — All material submitted, including headings, footnotes, and literature
cited must be typewritten doublespaced, on white paper. Papers shorter than
10 typewritten pages, including tables, should follow the format for notes.
2. Citations — All citations should follow the name-and-year system. The ''library
style" will be followed in listing references.
3. Abstracts — Every article must be introduced by a concise abstract. Indent the
abstract at each margin to identify it. Abstracts, on separate sheets of paper,
should accompany "Notes".
4. Abbreviations and numerals — Use approved abbreviations as listed in the CBE
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Tables should be numbered consecutively beginning with "1" and placed together in
the manuscript following the Literature Cited section. Do not double space tables. See
a recent issue of California Fisti and Game for format.
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reprint charge schedule along with the galley proof.
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