QMJF0RN1A

™GAME

'CONSERVATION OF WILDLIFE THROUGH EDUCATION"

California Fish and Game is a journal devoted to the conser-
vation of wildlife. If its contents are reproduced elsewhere, the
authors and the California Department of Fish and Game would
appreciate being acknowledged.

Effective January 1, 1975

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Robson A. Collins, Editor
California Fish and Game
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Long Beach, California 90802

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u

0

VOLUME 61

APRIL 1975

NUMBER 2

Published Quarterly by

STATE OF CALIFORNIA

THE RESOURCES AGENCY

DEPARTMENT OF FISH AND GAME

STATE OF CALIFORNIA

EDMUND G. BROWN JR., Governor

THE RESOURCES AGENCY

CLAIRE T. DEDRICK, Secretary for Resources

FISH AND GAME COMMISSION

TIMOTHY M. DOHENY, President, Los Angeles

JOSEPH RUSS III, Vice President PETER T. FLETCHER, Member

Ferndale Rancho Santa Fe

BERGER C. BENSON, Member SHERMAN CHICKERING, Member

San Mateo San Francisco

DEPARTMENT OF FISH AND GAME

G. RAY ARNETT, Director

1416 9th Street
Sacramento 95814

CALIFORNIA FISH AND GAME

Editorial Staff

ROBSON A. COLLINS, Editor-in-Chief Long Beach

KENNETH A. HASHAGEN, Editor for Inland Fisheries Sacramento

CAROL M. FERREL, Editor for Wildlife Sacramento

ROBERT N. TASTO, Editor for Marine Resources — Menlo Park

PAUL M. HUBBELL, Editor for Salmon and Steelhead Sacramento

HAROLD K. CHADWICK, Editor for Striped Bass, Sturgeon, and Shad _ Stockton

(66)

CONTENTS

Page

Growth Rate, Distribution, and Population Density of the North-
ern Quahog Mercenaria merccnaria in Long Beach, California

Jules M. Crane, Larry G. Allen and Connie Eisenxann 68

Observations on the Food Habits of Leopard Sharks (Triakis semi-
fasciata) and Brown Smoothhounds (Mustelus henlei)

Ronald A. Russo 95

Otter Trawl Cod-End Escapement Experiments for California
Halibut Jack W. Schott 82

Notes

A Preliminary List of Fishes Collected from Richardson Bay,
California 1972-1973 Roger E. Green 104

Changes in the Species Composition of Sharks in South San Fran-
cisco Bay Leray A. de Wit 106

First California Record of the Serranid Fish Anthias gordensis
Wade Edmund S. Hobson 111

(67)

Calif. Fish and Game, 61(2) : 68-81. 1975.

GROWTH RATE, DISTRIBUTION, AND POPULATION

DENSITY OF THE NORTHERN QUAHOG MERCENARIA

MERCENARIA IN LONG BEACH, CALIFORNIA

JULES M. CRANE, JR., LARRY G. ALLEN ' and CONNIE EISEMANN

Biology Department, Cerritos College
Norwalk, California 90650

A population of Mercenaries mercenaria (northern quahog) unique to
the West Coast of the western hemisphere is shown to be well estab-
lished in a lagoon in Long Beach, California. An estimated 300,000—
500,000 individuals appear to be displacing the native bivalve species
by out-competing other species for food sources and by being able to
survive greater environmental stress, e.g., sewage spills, introduction of
sodium hypochlorite. Population densities of Mercenaria reach 556 in-
dividuals per square meter.

Individual growth rates averaged 7.2 mm/year (0.28 in) with a gain
of 25.3 g/year (0.89 oz). There appeared to be better growth in fine
sediment than in coarse sand with the most rapid growth in all sub-
strates occurring in the smaller (80mm) clams. Breeding time for
Mercenaria is from June through August when the surface tempera-
tures are above 23 C (73 F).

The origin of the quahog in the lagoon is not known. Because of the
ease with which they may be dug and the consequent heavy clamming
pressure, the lagoon has been closed to all clamming since March,
1971. Recommendations for the preservation and use of this resource
are presented which include keeping the lagoon closed to clamming
for four more years to permit reestablishment of the population.

INTRODUCTION

Although the Atlantic quahog (cherrystone clam) Mercenaria mer-
cenaria has been known to occur in the Colorado Lagoon, a tidegate
controlled extension of Alamitos Bay, Long Beach. California, since
1967, (John Fitch, California Department of Fish and Game, pers.
comm.) its presence was not recorded until 1971 (Salchak and Haas,
1971). From the spring of 1970 to June 1973, a more extensive survey
of the Lagoon was conducted by Cerritos College, Norwalk. California,
under a contract with the California Department of Fish and Game,
to determine growth rates, distribution, spawning, and density of that
clam population as well as to explore some of the environmental para-
meters that might contribute to the success of this species in this par-
ticular area.

The Colorado Lagoon is a Y-shaped bodv of water which contains
about 189,000,000 1 (50.000,000 gal) of seawater and lias a low tide
perimeter of 1,720 m (5,643 ft) (Figure 1). There are six storm drains
which empty water from adjacent streets into the Lagoon. The East
end, at the base of the "Y", has a tidegate which is generally left open
all winter (mid September-May 1). Since the Lagoon is used for recre-
ational swimming, the tidegates are closed for several days at a time
during the summer to ensure sufficient water for swimming. Approxi-

1 Present address : Department of Biologv, California State University, Pullerton,
Fullerton, California 92631. Accepted September, 1974.

(68)

NORTHERN QUAIIOG GROWTH AND DISTRIBUTION

69

-3AV xa\/d

FIGURE 1. Colorado Lagoon, Long Beach, California.

70

CALIFORNIA FISH AND GAME

mately 700 m (2,297 ft) of the perimeter is used as a recreational
beach area by utilizing ocean beach sand replenished annually. This
area is on the North and South sides of the central part of the West
arm of the Lagoon. The East side of the northern arm has about 300 m
(984 ft) of coarse sand which appears to be native to the area. The
northern arm is closed to swimmers. The remaining perimeter is loosely
consolidated fine sand, silt, and clay. The bottom grades rapidly into
fine sand, silt, and clay sediments rich in organic debris. The maximum
depth is about 7.6 m (25 ft) and occurs in the middle of the area where
the two arms of the Lagoon divide. Most of the bottom profiles show a
more or less shallow basin curve. In the tidegate area, however, there
is a sharp drop off on both sides and a long steep slope extending west-
ward along the southern border from the tidegate for about 360 m
(1,181ft).

30 t

1961-1971

1971-1972

25 -

a.

E

20 --

15 "

10

O

J FMAMJ JAS

'72 '71

MONTHS

FIGURE 2. Comparison between ten-year average surface temperature (1961-1971) and the
year August 1971-August 1972.

Average annual surface temperature ranges for the years 1961-1971
ran from a low of 14.3 C (57.7 F) in January to a high of 2.") C (77 F)
in August (Figure 2). Surface dissolved oxygen averaged 6.9 ppm with
a monthly high of 8.3 (April) and low of 5.8 (December) for the same
period (Figure 3).

Salinity determinations were made with an American Optical Com-
pany hand-held refractometer. Salinities averaged 33%< (N = 32)
with one maximum reading of 35',, in -Inly and a minimum of 28%0
following a rain in November. No ten-year data were available for
comparison.

NORTHERN QUAHOG GROWTH AND DISTRIBUTION

71

Dissolved oxygen (ppm)

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72 CALIFORNIA FISH AND GAME

The common pelecypods observed in the Lagoon are quahogs (Mer-
cenaria mercenaries), cockles (Chiont undatella, C. fluctifraga) , little-
necks (Protothaca staminea), jackknife clams (Tagelus calif ornicus),
and mussels [Arculatala {Modiolus) demissa, Mytelis edulis]. Those
found occasionally are the yellow apolymetis (Florimetis obesa =
Apolymetis biangulata) and the yellow cockle (Laevicardium elatum).
These pelecypods arc competing for food year-round with the abundant
tunicate. Styella plicata, and during the summer -with Ciona intesti-
nalis, as well as with numerous fishes.

Despite extensive sampling, very few empty Mcrcenaria valves were
found. This is in contrast to the abundant shell remains of the other
resident pelecypods. The only occasion when Mcrcenaria shells were
apparent was when sampling the densest Mercenaria bed. Dead juve-
niles were found here. This is attributed to the fact that this dense bed
represents a climax community and there simply is no way newly
settled juveniles can out-compete the resident population.

Entcromorpha intestinalis is the dominant macroscopic alga. Speci-
mens of Viva lobata are found occasionally. To keep the area relatively
free of Entcromorpha, the Lagoon perimeter in the swimming area is
raked by hand once or twice a year and the alprae hauled away to a
dump. The perimeter was raked in October 1971, and March 1972
during our study. Included in the wrack thus accumulated were
numerous juvenile clams, including Mcrcenaria. Eandom sampling on
October 6, 1971 of a one m2 pile of Entcromorpha yielded 9 live Mcr-
cenaria ranging in length from 8 to 16mm. Judging by the rapid
growth rate in the early stages, we estimate that these spat represented
the June-August spawning time. At the same time, an estimated 36,000
juvenile (16-64mm) Tagelus calif ornicus were killed in an 800 m-
(8611 ft2) area. This die off was probably due to the tidegates having
been left closed at a minus tide after the raking had left the clams
exposed to an unusually hot, sunny day. This practice was somewhat
improved in March 1972 when the removal of algae was accomplished
without digging in so deeply with the rakes and by leaving the
tidegates open more during the process.

Because of a dramatic increase in clamming activity in the Lagoon
(estimate maximum of 4,000 clams removed/hour at lowest tides) dur-
ing the winter of 1970-71, the Lagoon was closed to all clamming by
the California Fish and Game Commission on March 12, 1971.

SEWAGE CONTAMINATION

On April 29, 1972 the Lagoon experienced an influx of 3,407,000 1
(900.()(i() gallons) of raw sewage, 1,890,000 1 (500,000 gallons) of
fresh water (used to flush the streets . and 318 kg (700 pounds) of
sodium hypochlorite (HTH) as the resull of a failure in the sewage
pumping station nearest the West end of the Lagoon. The area was
dosed to the public and the tidegates were kept closed until May 6,
when the surface coliform count had dropped sufficiently for gradual
flushing through the tidegates to be considered safe. The area was re-
opened to the public May 12, 1!»72.

The appearance of the water in the Lagoon on May 1, 1972, was
brownish and it had the odor of an open sewer. Examination of clams

NORTHERN QUAHOG GROWTH AND DISTRIBUTION 73

in the western swimming area suggested that Protothaca staminea and
Chione fluctifraga were experiencing some physiological stress as
evidenced by weakened adductor muscles and reduced body fluids. In
contrast, Mercenaria mercenaria appeared quite normal in these two
respects.

General examination of the area at that time, and subsequently,
revealed no indication of mass mortality in any of the macroscopic
biota. Surface sample coliform counts taken by the Long Beach Health
Department dropped sharply over a period of 7 days without any
artificial techniques being employed to "clear" the water. For the
eight stations taken in the Lagoon during this period, the maximum
surface coliform count dropped from 700 MPN (Most Probable Num-
ber)/ml on May 1 to 24 MPN/ml on May 2, 2.3 MPN/ml on May 3,
to 0.6 MPN/ml by May 4, 1972.

The dissolved oxygen content (DO) measured on May 1 by the
Long Beach Engineering Department was 2.] ppm (10 year average
for May = 7.6 ppm) with a coliform count on that day of 62.0 MPN/
ml. The next lowest recorded DO since June 1961 is 2.8 ppm (Decem-
ber 1961) when the coliform count was over 70 MPN/ml.

It is worth noting that specimens of Mercenaria in lab aquaria are
also extraordinarily hardy. This was evidenced by their survival in the
laboratory after short (2-3 days) exposure to temperatures of 27
C (81 F) and salinities over 45%0. In an accidentally "fouled"
tank containing Chione fluctifraga, Protothaca staminea and Mer-
cenaria mercenaria, only the Mercenaria survived.

In summary, the sewage exposure of April 29, 1972 appears to have
had no noticeable ill effects on the population of Mercenaria in the
Colorado Lagoon.

ORIGINAL SOURCE OF MERCENARIA IN THE LAGOON

There is no record of the northern quahog being introduced in
Southern California waters since 1940. Spat were shipped to the west
coast in the early 1960 's from the National Marine Fisheries Labora-
tory, Milford, Connecticut (Lossanoff, pers. comm.), but there is no
indication that they were introduced in the Southern California area.
In the winter of 1951-52, one half bushel of cherrystones ("between
cherrystone and quahog size") flown in from Long Island Sound, New
York, were illegally introduced into a restricted area of Alamitos Bay
by a local delicatessen owner. They were maintained in the Bay until
1954 when construction of a bridge destroyed the bed. No specimen
of Mercenaria mercenaria has been found in the bay since then despite
intensive surveys conducted over the last 15 years (Reish, 1968, 1969),
and none have been reported from any area south of Humboldt Bay,
California.

In view of the fact that the Colorado Lagoon clam colony is so
extensive and that the largest quahogs from there (113mm) may be
at least 15 years old, it seems possible that they are the descendants
of the illicit 1951-54 colony. The probability remains, however, that
there was a subsequent similar introduction directly into the Lagoon.

74 CALIFORNIA FISH AND GAME

CLAM DISTRIBUTION AND DENSITY

The areas of highest Mcrcenaria density in the Lagoon reflect tne
areas where clammers could not reach the clams, either because they
were too deep to obtain without diving or because the area was inac-
cessible (Figure 4). The low density areas around the perimeter are
clearly due to clamming. As an example, one perimeter station sampled
in summer, 1970 yielded 53 clams/m2 (4.9 ft2), while the same station
had a density of 1-2 clams/m2 in the summer of 1971. During that
year, clamming activity was observed on several occasions in that
particular area.

Diver transects were examined on September 15, 1972 (Figure 4, A-
A' through F-F'). Clam distribution and density was determined by
hand digging along the length of the transect. The lowest estimates of
density were used in evaluating the data. Precise area counts were
made near the east end of the densest bed to define its perimeter. It is
useful to note that at the western, denser end of the bed the proportion
of breeding size (>40mm) clams to juveniles is 12:1, but where the
bed begins to train off, the proportion is 4 :1. This is interpreted to
mean that the bed is developing in an easterly direction.

Eighty-six stations were established at 20 m (64 ft) intervals around
the Lagoon at the -0.5 to -1.0 tide line. Samples were screened through
I inch mesh wire screen at each station from an area of 1 m2 (10.76
ft2) dug to a depth of 20 cm (8 in). The clams thus obtained were
weighed and measured in the field and returned to the station area.
The perimeter sampling data were lumped according to arbitrary
density figures (Figure 4). The highest measured density occurred
off the main float where 556 Mcrcenaria mercenaria were counted in
1 m2 (10.76 ft2). Extrapolating perimeter and diving stations, a con-
servative estimate would place the Lagoon population of Mercenaria
mercenaria from 300,000-500,000 clams. Most of these are in water
that is more than three feet deep at low tide.

GROWTH RATE DETERMINATIONS

In the summer of 1971, six growth cages, each consisting of 6.35 mm
(i in) iron rods welded into a 61 cm x 61 cm x 15 cm (2 ft x 2 ft x
0.5 ft) framework, covered with } inch nylon fish netting, were stocked
with clams and placed in different locations in the Lagoon (Figure 1).
The clams were measured in their maximum dimension with calipers,
weighed on field balances, and various numbers of clams were placed
in the cages. Clams in cages 1, 2, and 3 were marked with individual
painted numbers, and all clams were marked along the margin with
felt tip red ink marking pens. Divers retrieved the clams at varying
intervals over the following year. The cages and clams were all re-
placed for a future possible study after all the clams were measured
in August 1972. The average annual length increase for the 227 clams
thus measured was 7.2 mm (0.28 in) with a concurrent average weight
increase of 25.3 g (0.89 oz) (Table 1).

Using the individually marked clams, which were measured more
often, it was possible to develop some idea of seasonal variation in
growth rate.

NORTHERN QUAHOG GROWTH AND DISTRIBUTION

75

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CALIFORNIA FISH AND GAME

TABLE 1 — Average Annual Growth of MercenaWa mercenaria in the Colorado
Lagoon Summer 1971-Summer 1972 (N = 227)

Cage number

X Length
mm (range)

X Weight

B

Comments

1 (N =25)

9.3 (1.7-24.6)
4.1 (0.0-9.8)

4.9 (1.3-9.1)

3.9

13.9
7.1

7.2

25 (8^ mon.)
18 (8H mon.)

23

20
43
23

25.3*

Clams measured 4 times

2 (N = 25)- --

Clams measured 4 times; growth

3 (N = 14)

initially obstructed by tuni-
cates
Clams measured 4 times; loss

4 (N =50)...

of clams due to tear in netting
Clams measured 3 times

5 (N =52)

Clams measured 3 times

6 (N = 61)

Clams measured 2 times

Overall average

* Minimum figure due to shorter growth period recorded in Cages 1 & 2.

The period June to November reflected a growth rate almost three
times that in the November to June time span (Table 2).

TABLE 2— Average Monthly Growth Rate by Season, 1971-1972 (N = 64)

Cage number

Nov.-June

June-Nov.

1 (N = 25).

2 (N = 25)

3 (N = 14)

6 month X

0.4 mm
0.2 mm
0.2 mm

0 . 27 mm

1 . 20 mm
0.53 mm
0.65 mm

0.79 mm

Using standard soil screens, an attempt was made to determine the
relationship, if any, between sediment particle size and growth rate.
Sediment samples were taken from the cage area, dried, and each
particle size weighed to obtain the percentage of that size in the
sample.

TABLE 3 — Percent Substrate Particle Size Related to Growth Rate

Particle size (%)

>4. 76-2. 38

2.37-0.59

0.58-0.149

<0.149

Annual growth

rate (annual
average in mm)

Cage 1...

1.2
1.8
0.0
0.3
0.3
5.9

14.4
9.4
2.3
5.4

10.1
20.7

62.3
45.0
32.7
37.3
59.5
61.2

22.8
43.8
65.1
57.1
30.1
12.2

9.3

2

4.1

3..

4.9

Est. * 4..

3.9

5

13.9

6

7.1

* Part of sample lost in weighing.

Note that the ratio of 0.58-0.149 to < 0.149 particle size is greatest
in cages 6, 1, and 5 which contained the clams showing the highest
annual growth rate. The ratio is reversed in cages 2, 3, and 4 which

NORTHERN QUAHOG GROWTH AND DISTRIBUTION

77

show the least growth. However, since the cages were widely separated
throughout the Lagoon, it is reasonable to suppose that the amount
of nutrients available to the clams was not constant, and that would
influence their growth. It is interesting to note that the cage nearest
the storm drains (cage 5) showed the highest growth rate (Table 3).

GROWTH BY SIZE CLASSES

Based on the growth data for the individually marked clams in cages
1, 2, and 3, there appears to be a tendency for the clams to decrease in
length increments as they get larger. This is especially noticeable in
clams over 80 mm (Table 4). Further comment on the larger quahogs
would be speculative in view of the small sample size.

TABLE 4 — Average Annual Length Increase by Size Classes

Time

period

(months)

Size class (mm)

Cage f

40-60

61-80

81-100

1__

12
12
12

XA

12.9mm (N
4.4mm (N
3.0mm (N

= 8)
= 5)
= 1)

8.2mm (N

4.2mm (N

60mm (N

= 16)

= 19)
= 12)

0 (N = I)'

2.

2.3mm (N = 1)2

3

0 (N = 1)3

= 6.7mm

XA = 5.9mm

1 Original length = 97 mm.
5 Original length = 86 mm.
» Original length = 82.7.

Weight increment data must be viewed in light of the fact that final
measurements were made in August and many of the clams may have
spawned out. Also the time period for cages 1 and 2 is different than
the full year for cage 3 which has the smallest sample size. These data
are included merely to give some idea of the order of magnitude of
clam weight increase (Table 5).

TABLE 5 — Average Annual Weight Increase by Size Classes

Time period
(months)

Size class (mm)

Cage #

40-60

61-80

81-100

1

8.5

8.5

12.0

29. 3g (N = 8)
10. 7g (N = 5)
13. Og (N = 1)

24. 4g (N = 16)
19. 2g (N = 19)
24. 2g (N = 12)

4.0g (N = 1)>

2-.

17. Og (N = 1)2

3 .-

13. Og (N = 1)3

1 Original weight = 290g.

2 Original weight = 195g.

3 Original weight = 158g.

PLANKTON SAMPLING

Surface plankton tows were made weekly from June 1972- June
1973. Samples were collected between 8 and 9 am along the east side
of the longer float, using a standard £ m plankton net. All samples were
preserved in either 40% isopropyl alcohol or in a Lugol solution made
up of 10 g KI in 20 ml H20, and 5 g I2 in 50 ml H20 to which 5 g

78

CALIFORNIA FISH AND GAME

X;i < _I I :< >_. was added. Three drops of this solution were used as a
preservative for a 100 ml sample. This latter solution proved advanta-
geous in revealing structural detail not visible with the alcohol pre-
servative. A 1 ml sample from each collecting vial was examined in a
Sedgewick Rafter counting chamber using a Whipple micrometer
(APHA, 1971). Veligers appeared continuously in the samples from
early May through mid-September, with the highest count of 419 in-
dividuals occurring in mid-July. No veligers appeared in samples taken
the remainder of the year, except for a short period from late Decem-
ber to mid- January when a small number (less than 10) appeared in
the samples (Figure 5).

400

300

200-

1972

1973

FIGURE 5. Number of straight hinge veligers per 1 ml concentrated sample from weekly
plankton tows in the Colorado Lagoon, June 1972— June 1973.

It is difficult to distinguish among the species of veligers present in
the plankton samples. Basedon comparison with the veligers raised in
the laboratory, we judge that the samples in June, July, and August
contained Mercenaria mercenaria. In addition, the appearance of large
numbers of straight hinge veligers in the plankton during July and
August corresponds to an increase in surface temperature above 23 C
(73 F). No information is available on bottom temperatures. However,
laboratory observations show that this race of Mercenaria mercenaria
will spawn spontaneously at 22 C (72 F) and can be induced to spawn
from 22-25 C (72-77 F) (see section on spawning).

There are four morphologically different veligers, including the
Mercenaria type, in the sunnier samples. The winter pelecypod spawn-
ing represents a single genus, probably not Mercenaria. We conclude
that Mercenaria is among other clams spawning in June, July, and
August in the Lagoon in response to higher ambient temperatures.

NORTHERN QUAHOG GROWTH AND DISTRIBUTION 79

SPAWNING EXPERIMENTS

In our experiments with spawning we varied the methods of Loosa-
noff (1937) and Loosanoff and Davis (1950) in their study of the east
coast Mercenaria mercenaria.

The procedure for spawning "summer" clams (those taken directly
from the Colorado Lagoon from June through August) was to put them
directly in enamel 4 1 (1.1 gallon) trays (spawning trays) each with
3 1 (.79 gallon) of sea water in a constant temperature bath set at 25 C
(77 F). Spawning resulted from simply transferring clams from the
22-23 C (72-73 F) temperature in the holding tank to the 25 C (77 F)
temperature in trays. However, greater and more regular success was
obtained when sperm from a freshly killed and gonadectomized male
was pipetted into the incurrent siphons of the clams in the trays.
Spawning usually occurred 1-2 hours after the introduction of sperm
to "ripe" clams.

After the clams had spawned, they were removed from the trays.
The water in the trays was then stirred to insure maximum fertiliza-
tion. After 30 minutes, the sperm-egg suspension was introduced into
1.5 1 (0.40 gallon) fingerbowls containing sea water which had been
filtered through cotton. The amount of suspension added to the finger-
bowls varied with the spawning activity. A heavy spawning required
about 100 ml of suspension to insure that the larval population did not
exceed the 250 larvae/ml level suggested by Loosanoff (1963). Our ex-
periments indicate that for small scale culturing, 100-200 larvae/ml is
probably a more desirable level.

Spawning "winter" clams (i.e., those taken from the Lagoon in
winter or those maintained in refrigerated tanks in the laboratory)
was more difficult. The water temperature was raised gradually over
a 3-4 week period to 22 C (72 F). At the same time, the feeding was
double the normal daily amount of 1.8 mg (6 X 10"5 oz) of ground up
Enteromorpha to one g (0.035 oz) of clams in a total tank volume of
208 1 (55 gallons). At the end of the temperature raising period, the
clams were placed into spawning trays and the procedure was then the
same as for the "summer" clams.

"Summer" clams which have spawned in the lab should be able to
spawn again in the same season at least once. In the lab we have had
one group of clams spawn twice, on July 3, 1971 and on September 1,
1971.

Clams fresh from the Lagoon were induced to spawn on six occasions
from early July to late August. Since plankton samples taken from
the Lagoon during June, July, and August contained larvae of Mer-
cenaria mercenaria. We are thus led to conclude that this species spawns
continuously in the Lagoon during the summer months.

Larvae from the successful attempts survived well for at least two
days to the straight-hinge veliger stage after the spawnings which
were observed. After two days problems with feeding, over-crowding,
waste products and the most suitable culture vessel hindered our at-
tempts to raise larvae to settling stage.

A spawning experiment was performed on clams that had been held
under lab conditions for nine months. These clams had been collected
from the Colorado Lagoon in November, 1970 and were kept at 20 C
(68 F) until May 11, 1971 when they were switched to a refrigerated

80 CALIFORNIA FISII AND GAME

tank at 13 C (55 F). From July 3 to July 19, 1971, the temperature
was gradually raised to 21 C (70 F) and maintained at 21-22 C (70-
72 F) for 34 days. At this time, the clams were placed in spawning
trays at 25 C (77 F) and after 3 hours, a sperm suspension from a
dissected male was added. Eleven dams ranging from 53 mm (2.7 in)
to 93 mm (3.6 in) responded by spawning within 50 minutes. The two
43 mm (1.7 in) clams remained inactive.

This experiment shows (at least in one case) that Mercenaria mer-
cenaria from the Colorado Lagoon can be maintained under laboratory
conditions for extended periods of time (at least 10 months) and still
be spawned successfully.

In determining sexual maturity we utilized three methods: observ-
ing spawning directly, drilling to aspirate gonadal material, and dis-
secting to obtain gametes from different size groups.

Spawning experiments were performed using separate trays for
each of the following size classes: 40-50 mm (1.6-1.9 in) (N = 2),
51-60 mm (2.0-2.3 in) (N = 7), 61-70 mm (2.4-2.7 in) (N = 10),
71-80 mm (2.8-3.1 in) (N = 8), 81-93 mm (3.2-3.6 in) (N = 5). All
but the two smallest clams were induced to spawn.

We had success with drilling clams with small dental drills. The holes
were drilled about \ of the distance from the umbo to the shell margin,
approximately on the midline. The needle of a 1 cc syringe was inserted
into the hole into the visceral hump and the aspirated material ex-
amined. The hole in the shell was filled with paraffin and sealed with
collodion. We had about 40% mortality among drilled Mercenaria mi r-
cenaria. In drilling, it was discovered that clams 40 mm (1.6 in) and
larger apparently had mature gametes. One clam 28.9 mm (1.1 in) was
examined but no mature gametes were found.

The third method of determining sexual maturity was dissection and
examining for gametes. All of the 12 clams from 51.9 mm to 82.3 mm
(2.0-3.2 in) checked were found to be mature.

CONCLUSIONS AND RECOMMENDATIONS

The colony of Mercenaria mercenaria in the Colorado Lagoon is a
well established breeding population on the order of magnitude of one
half million individuals. The species appears to out-compete native
pelecypods for food, and for this reason will either replace indigenous
species or at least suppress their growth. The implications in this
statement should be noted if consideration is given to future introduc-
tions of M. mercenaria elsewhere on the West Coast.

The hardiness of Mercenaria mercenaria commends it for laboratory
experimentation and aquacultural investigations.

It would appear that there is a direct relationship between water
temperature and the spawning of Mercenaria. For this "race", the
optimum spawning temperature lies between 22-25C (72-77F).

The present condition of the Lagoon is such that it seems probable
that the Mercenaria colony there will continue 1o thrive, providing no
drastic changes are made in the environment, e.g.. cementing in the
Lagoon, changing the storm drains, building a freeway adjacent to the
Lagoon, dredging, etc.

Since it is quite possible that this particular stock represents a race
of Mercenaria mercenaria which is uniquely suited for survival in Cali-

NORTHERN QUAHOG GROWTH AND DISTRIBUTION 81

fornia waters, use of these specific clams for laboratory breeding pur-
poses, as well as for a pool for stocking breeders elsewhere, would
seem appropriate.

Leaving the Lagoon closed to clamming for four years should give
the beds sufficient time to recover from the intensive clamming pressure.

Bag and size limits specifically for this genus should be established
prior to reopening the area.

ACKNOWLEDGMENTS

This investigation was supported by the California Department of
Fish and Game, Contracts 6S-1910, 6S-835, and 6S-1878 to Cerritos
College, with the senior author as project director. In addition to the
junior authors, the following students have acted as project aides:
Anthony Salchek, Jeff Haas, Patrick Collins, and Russ Reynolds.
Invaluable voluntary assistance was received from many Cerritos Col-
lege students, chief among these being Patricia Allen, Robert Osborn,
John Ljubenkov, Donald Drysdale, Michael Stow, Robert Dorn, and
Laurie Park. We wish to acknowledge the fine cooperation of Bob Cot-
ter, Long Beach Aquatic Recreation Department, as well as the Long
Beach Lifeguard Department and the Long Beach Health Depart-
ment. Inspector Robert Kaneen, California Department of Fish and
Game, was most helpful in maintaining surveillance over the project
area. Walter Dahlstrom, California Department of Fish and Game,
provided guidance and the loan of materials for the project.

REFERENCES

American Public Health Association (APHA). 1971. Standard methods for the
examination of water and wastewater. APHA, Washington, D.C. : 874p.

Loosanoff, V. L. 1937. Spawning of Venus mercenaria L. Ecology 18 (4).

, and Harry C. Davis. 1950. Conditioning V. mercenaria for spawning in

winter and breeding its larvae in the laboratory. Biol. Bull. 98(1) : 60-65.

1963. Rearing of bivalve mollusks, Advances in Marine Biology, Vol. 1,

Academic Press, pp 14-125.
Reish, D. 1968. Marine life of Alamitos Bay. Los Alamitos, California. 92p.

1969. Studies on the Mytilus ediilis community in Alamitos Bay, California.

Veliger 11(3) : 250-255.

Salchak, A., and Jeff Haas. 1971. Occurrence of the northern quahog, Mercenaria

mercenaria, in Colorado Lagoon, Long Beach, California. California Fish Game

57 (2) : 126-128.

Calif. Fish and Game, 61(2) : 82-94. 1975.

OTTER TRAWL COD-END ESCAPEMENT EXPERIMENTS
FOR CALIFORNIA HALIBUT1

JACK W. SCHOTT

Marine Resources Region

California Department of Fish and Game

Two otter trawl cod-end escapement experiments were conducted to
test escapement of sub-legal unmarketable California halibut (Para-
lichthys calif ornicusj through large and small meshed cod ends. Most
sub-legal halibut (less than 22 inches TL) escaped through the 7' 2 -inch
mesh cod end. Fewer halibut of higher average weight, but with
greater total weight, were captured by the 7% -inch mesh cod end,
than by the cod ends of smaller mesh size.

INTRODUCTION

Experience gathered during the tagging of about 14,000 California
halibut, captured in otter trawls equipped with 5-inch mesh cod ends,
showed that mortality increased rapidly with length of trawling (drag-
ging) time. The optimum trawling time that nets could be fished, yet
leave captured fish in prime condition for tagging and release, was no
longer than 30 min. Fishing periods of 1 to 4 hr demonstrated a prog-
ressive increase in mortality, particularly of sub-legal sized (less than
22 inches TL) unmarketable fish. Most sub-legal halibut are juveniles.
At the termination of a 4 hr drag most sub-legal fish were dead and we
believe that the remainder were unlikely to survive.

From this experience, and because most commercial halibut drags
are of 1 to 4 hr duration, we felt a significant number of sub-le^al (un-
dersized) halibut was being destroyed by commercial trawl gear and
that larger meshed cod ends might provide suitable escapement for
these fish.

In December 1964, we began experiments to determine the cod-end
mesh size that would provide optimum escapement for sub-legal hali-
but while still retaining the larger sized fish.

Trawling operations were conducted off Long Beach and Hunting-
ton Beach utilizing 6^-, 7- and 7^-inch mesh cod ends. The smallest
halibut captured by the 6^-inch cod end was 449 mm (17.8 inches) ;
by the 7-inch cod end, 494 mm (19.4 inches) ; and by the 7^-inch cod
end, 525 mm (20.7 inches).

Experiments were designed and conducted with two identical 5-inch
mesh trawl nets. One net was equipped with a 5-h (the second experi-
ment used a 5) -inch cod end and the other utilized a 7^-inch mesh.
All cod ends were 6.1 m (20 ft) in length and made of #80 nylon
twine.

Machine manufactured mesh sizes are measured from center of knot
to center of knot resulting in an actual opening size of less than this
figure. The true escapement size of the mesh was determined by meas-
uring the webbing openings from knot to knot with a knife-edge inside

1 Accepted for Publication November, 1974.

(82)

CALIFORNIA HALIBUT ESCAPEMENT

83

caliper. This was done immediately after trawling operations when the
cod-end webbing was wet and subjected to loadstrain of the catch. Ten
measurements each of the 5-, 5|- and 7-|-ineh meshes resulted in aver-
age size openings of 4.91, 5.41 and 7.31 inches respectively, but sub-
sequent reference to mesh size will be 5-, 5h or 7^-inches.

Size of the cod-end mesh first used in each set of paired drags was
serially chosen from a table of mesh sizes (Table 1). This table was
constructed from random numbers using odd and even numbers to
represent 7^-inch and 5|- (or 5-) inch cod-end webbing. In the event
of a torn net, loading and stoppage of the cod end with moss or kelp
or, if the drag was terminated before the prescribed trawling time was

TABLE 1 — Random Cod-end Mesh Size Drag Sequence

Drag
number

Mesli size
(inches)

Drag
number

Mesh size
(inches)

Drag
number

Mesh size
(inches)

1

7^

sy2

5V2
7V2
7V2
5X
7H

sy2

7Y2
hY2

7y2
5y2

7V2

5y2
5y2
7y2

7H

18

19

7y2

7y2
5y2
5y2
7y2
7y2
5y2
sy2
7y2
7y2
5y2
7y2
5y2
7y2
sy2

35

36

37

7)4

2

5%

3

20

514

4— .

21 .. ..

38.

39

40

7H

5

22

7y2

6

23.

$y2

7 ...

24 .

41 .

7y2

8

9

25

26-_

42

43

44.

5y2
by2

10

27. -

7y2

11

28

45..

7y2

12

29 .

46_.

$y2

13

30. ..

47-

$y2

14

31...

48

7y2

15..

32..

49-.

7y2

10 .

33..

50 .

by2

17

34

completed, the results of the pair of drags were discarded and the next
sequential mesh size taken from the table for the next pair of drags.
Trawling drags were conducted in pairs. A drag was made in one
direction using a net with one size cod end and then the second net
with the other cod end was towed in the opposite direction. Both trawl-
ing experiments were conducted in 3-20 fm from off Ventura to Port
Hueneme and off Santa Barbara, California.

EXPERIMENT I, RESEARCH CRUISE 65-A-l

In January 1965 the Department of Fish and Game launched re-
search cruise 65-A-l on the M/V ALASKA to compare halibut reten-
tion in nets having 5|- and 7^-inch mesh cod ends.

Twenty-two paired drags, each drag of 40 min duration, were made
from February 24 to March 5, 1965. Seventeen species of teleosts, 13 spe-
cies of sharks and rays and 23 species of invertebrates were taken (Tables
2, 3, and 4). The three dominant species captured were California hali-
but, 337 fish; hornyhead turbot (Pleuronichthys vcrticalis), 326 fish;
and fantail sole (Xystrcurys liolepis), 68 fish (Figures 1, 2, and 3 re-
spectively) .

84 CALIFORNIA FISH AND GAME

TABLE 2 — Teleosts Captured in the 5V4- and 7' 2 -Inch Trawl Cod Ends. Cruise 65-A-1

Species

Paralichthys californicus
Citharichthys sordidus...

Xy$treury$ liolepis

Hippoglossina stomata..

Parophrys vetulus

PleuTOnichthys coenosus.
Pleuronichthys decurrens

Pleuronichthys ritteri

Pleuronichthys verticalis.

Hypsopsetta guttulata

Genyonemus lineatus

Menticirrhus undulatus . .
Amphistichus argenteus.

Phanerodon furcatus

Rhacochilus toxotes

Scorpaena guttata

Merluccius productus

Cod end

5H-inch

231
1
44
5
20
3
1
7

205
18
2
1
1
1
1
1
1

7H-inch

106

24

1
14

1

121
3

Size range
(mm)

351-980

162
242-522
295-362
220-387
256-349

257
212-265
199-332
258-359
170-245

605
251-280

205

335
281-308

652

The 5^-inch mesh cod end captured nearly twice as many hornyhead
turbot and fantail sole as the 7^-inch mesh cod end (Figures 2 and 3).
More large fish escaped from the 74-inch mesh than from the 5|-inch
mesh ; however, many smaller fish, though exposed to the same 7^-inch
mesh, were retained.

Comparison of retention of California halibut in the 5£- and 74-inch
mesh cod end showed that almost all sub-legal fish escaped through the
7^-inch mesh but many were retained by the 5^-inch mesh (Figure 1).
The 5^-inch mesh captured 134 (58%) sub-legal halibut that weighed
a total of 161.1 kg (358 lb), and 97 (42%) legal sized fish weighing

TABLE 3 — Sharks and Rays Captured in the SVi- and 7 '/2-Inch Trawl Cod Ends.
Cruise 65-A-l

Species

Cephaloscyllium ventriosum

Mustelus californicus

Mustelus henlei

Triakis semifasciata

Squalus acanthias

Squatina californica

Platyrhinoidis triseriata

Rhinobatos productus

Torpedo californica

Raja inornata

Raja rhina

Gymnura marmorata

Myliobalis californica

Cod end

5J^-inch

7H-inch

5

1

2

1

1

1

1

2

13

11

7

3

28

(i

10

11

1

1

1

14

5

CALIFORNIA HALIBUT ESCAPEMENT

85

318.1 kg (707 lb). The 7^-inch mesh cod end retained 6 (6%) under-
sized halibut that weighed a total of 4.9 kg (11 lb) and 100 (94%)
legal sized fish weighing 379.3 kg (843 lb).

Sixty-one kg (135 lb) more legal sized halibut were captured by the
7^-inch cod end than by the 5^-inch, but the 5^-inch cod end retained
128 more undersized, unmarketable fish than the 7^-inch.

The legal sized halibut captured in the 7^-inch mesh cod end weighed
more and averaged 5 kg (1.1 lb) heavier than those retained by the
5|-inch mesh. In addition, the 7|-inch mesh cod end provided almost
perfect escapement for sub-legal unmarketable fish.

EXPERIMENT II. RESEARCH CRUISE 65-A-4

The second escapement experiment was conducted in May 1965 on
the M/V ALASKA, research cruise 65-A-4. The cruise was designed
to test the effect of longer trawling periods upon halibut escapement
from 5- and 7^-inch mesh cod ends.

Fourteen paired drags, each of 90 min duration, were made May
11-26, 1965. Eleven species of teleosts, 10 species of sharks and rays
and 16 species of invertebrates were taken (Tables 5, 6, and 7). The
four dominant species captured were California halibut, 615 fish;
English sole (Parophrys vetulus), 408 fish; hornyhead turbot, 236 fish;
and sand sole (Psettichthys melanostictus) , 95 fish (Figures 4, 5, 6,
and 7).

About 2\ times more English sole were retained by the 5-inch mesh
cod end than by the 1\. The frequency distribution of fish captured

TABLE 4 — Invertebrates Captured in the SVi- and 7V2-lnch Trawl Cod Ends. Cruise
65- A- 1

Species

Cod end

53^-inch

7H-inch

147

44

9

9

30

33

11

32

151

78

37

12

3

2

6

1

24

90

54

19

5

__

1

38

14

20

18

3

3,000

3,000

8

21

1

1

366

121

4

__

1

4

__

9

125

122

107

29

Astropecten sp

Pisaster ocraceus

Pisaster giganteus

Patiria miniata

Cancer anthonyi

Cancer gracilis

Cancer antennarias

Cancer productus

Loxorhynchus grandis

Loxorhynchus crispatus

Portunus xantusii

Pugettia producta

RandaUia ornata

Hemisquilla stylifera

Feather hydroids, scoopa of

Sea pens, estimated count

Kelletia kelleti

Forerria belcheri

Polinices sp

Trachycardium quadragenarium

Nudibranchs. -

Squid eggs, scoops of

Pelagic tunicates

Bryozoans. scoops of

Kelp, assorted, scoops of

86

CALIFORNIA FISH AND GAME

en

100
98
96
94
92
90
88
86
84
82
80
78
76
74
72
70

5'j-INCH MESH COD END 7'HNCH MESH COD END

p 68

z

Ul

X

a

64

62

5 60
58
56
54
52
50
48
46
44
42
40
38
36

97 FISH (42%)
707.40 LB
AV. WT. 7.3 LB

100 FISH (94.3%)
842.52 LB
AV. WT. 8 5 LB

134 FISH (58%)

358 33 LB

AV WT. 2.7 LB

34 -

6 FISH (5.7%)
11 03 LB

AV. WT. 1.8 LB

20

15

10

0

10

•a

o

'5

a.

o

£•

c

0)

*

-o

0)

<J
O

ID
O

'3

c

13
O

u

-c
u
c

-a

c
o

I

-o

a>

a

D

u

3
-Q

"5

z

a

°c
o

in

0)
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tt

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NUMBER OF FISH

CALIFORNIA HALIBUT ESCAPEMENT

87

by both mesh sizes was about the same but more of the larger fish
escaped through the 7^-inch mesh (Figure 5).

Retention of hornyhead turbot by the 5-inch was about 1\ times
greater than through the 7^-inch. Forty-eight fish longer than 300 mm
(11.8 inches) were retained by the 5-inch but none was captured by
the 7^-inch (Figure 6).

More than four times as many sand sole were captured in the 5-inch
mesh cod end than in the 7^-inch, and the 7^-inch mesh retained more
large fish than short ones (Figure 7).

Retention of California halibut in the 5- and 7|-inch mesh cod end
replicated in most respects what had been demonstrated by Experi-
ment I. Two hundred seventy sub-legals were captured by the 5-inch

5V2-INCH MESH COD END I 7V2-INCH MESH CODE END

33 h

32
31
30

c/> 29

ac

m

t 28

3E

£ 27

u

o

£ 26 -

i-
o
z 25 -

LU

—I

-! 24 -

\-
O
»- 23 -

22

21

20

205 FISH
135.7 LB

121 FISH
60.8 LB

30

20

NUMBER OF FISH

FIGURE 2. Comparison of Retention of Hornyhead Turbot in the 5Vi- and 7!£-lnch Mesh
Cod End. Weights are Calculated. Twenty-two Paired Drags, 40 Min Each. Cruise
65-A-l .

88

CALIFORNIA FISH AND GAME

5V2-INCH MESH COD END 7%-INCH MESH COD END

53

51

49

47

c/>

45

<r

LJ

LJ

43

^

z

41

LJ

o

o

LJ

—I

_J
<

o

NUMBER OF FISH

FIGURE 3. Comparison of Retention of Fantail Sole in the 5Vi- and 7'/2-lnch Mesh Trawl Cod
End. Twenty-two Paired Drags, 40 Min Each. Cruise 65-A-l.

mesh cod end but only 12 were retained by the 74-inch (Figure 4).
One hundred seventy-seven legal sized fish weighing 658.4 kg (1463 lb),
with average weight of 3.72 kg (8.27 lb), were taken in the 5-inch cod
end and 156 fish weighing 614.7 kg (1366 lb), with an average weight
of 3.94 kg (8.76 lb), were retained by the 7^-inch mesh. The 7^-inch

CALIFORNIA HALIBUT ESCAPEMENT 89

TABLE 5— Teleosts Captured in the 5- and 7'/2-lnch Cod Ends. Cruise 65-A-4

Species

Cod end

5-inch

7H-iQch

Size

range

(mm)

318-

1,160

226-

397

241

212-

265

193-

396

232-

468

421-

474

234-

517

206

176-

326

220-

379

249-

400

298

Paralichthys californicus.

Parophrys vetulus

Pleuronichlhys decurrens.

Pleuronichthys rilteri

Pleuronichthys verticalis _,

Xystreurys liolepis

Platichthys stellatus

Psettichthys melanostictus

Symphurus alricauda

Genyonemus lineatus

Amphisticus argenteus

Damalichthys vacca

Scorpaena guttata

447

294

1

7

208

17

2

77

26

20

3

1

168
114

28
2
4

18
1
2
7

TABLE 6 — Sharks and Rays Captured in the 5-

Cruise 65-A-4

and 712-Inch Trawl Cod Ends.

Species

Cod end

5-inch

7H-inch

Galeorhinus zyopterus.-

Mustelus henlei

Squalus acanthias

Squalina californica

Platyrhinoidis triseriata

Rhinobalos productus

Torpedo californica

Raja binoculata

Raja rhina

Myliobatis californica--

1

3

4

3

3

21

1

410

190

4

4

2

__.

6

4

94

182

TABLE 7 — Invertebrates Captured in the 5- and 7 T 2 -Inch Cod Ends.

Cruise 65-A-4

Species

Cod end

5-inch

7H-inch

Astropecten sp

Pisaster giganteus

Patiria min iata

Cancer anthonyi

Cancer gracilis

Cancer antennarias

Loxorhynchus grandis

Loxorhynchus crispatus

Randallia ornata

Hermit crabs (in moon snail shells)

Hemisquilla stylifera

Forerria belcheri

Polinices sp

Jellyfish, large

Aphrodita sp

Bryozoans and hydroids

Kelp, scoops of

11

12

72

52

m _

5

126

69

37

12

1

1

14

27

230

66

30

8

2

0

1

6

2

219

19

..

1

1

._

1J^ tons

9

11

90

CALIFORNIA FISH AND GAME

118
116

5-INCH MESH COD END

7 -INCH MESH COO END

1

110

1

108

106

104

1

102

177 FISH (39.6%)
1463 29 LB

| 156 FISH (92.9%)
1366 48 LB

100

AV WT 827 LB

AV WT. 8.76 LB

98

1

■

96

1

1
1

94

■

92

■

90

1
■

1
1
1

88

1

86

1

■

84

1

|

82

1

80

« 78
or

■■■

1

1

■

ui 76

^■1

5

■■

■

E 74

■■■

■■

z
u

■

^M

u
. 72

^■i

■MM

X

■■

■■

§^■1

■

Z 70

■

■1

-i 68

<

JZ

£ 66

-S

^^^

64

hb

62

■

■■■■■

60

58

ItGAl bl/E

56

— ^ c.c. IINLnto p- ^^_

■

54

"I

52

' i

50

48

46

1

44

42

™

40

270 FISH (604%)

1

■

12 FISH (7 1%)
1 36 13 LB

38

720 33 LB

AV WT 2 67 LB

AV WT 3 01 LBS. >.

36

1

34

1

32

1
1

30

40

30

20 10

NUMBER OF FISH

20

<

o

«

'a
w
U

c
O

CK

en
o

0>

-D

C
UJ

-a
o
U

0)

u

c

5

o
0

-o

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a

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u

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x

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en

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D.

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o
u

UJ

=>
O

CALIFORNIA HALIBUT ESCAPEMENT

91

5-INCH MESH COD END I 7%-INCH MESH COD END

NUMBER OF FISH

FIGURE 5. Comparison of Retention of English Sole in the 5- and 7!/2-lnch Mesh Cod Ends,
14 Paired Drags, 90 Min Each. Cruise 65-A-4.

mesh cod end captured 43.7 kg (97 lb) and 21 fish less than the 5-inch
mesh cod end, but the average weight of these legal fish was .20 kg
(0.44 lb) greater. The capture of the two largest halibut taken in
the same 5-inch mesh drag, may have been by chance. If these two
fish had not been taken it would nearly cancel out the total weight
differences of the 5- and 7^-inch mesh catches.

92

CALIFORNIA FISH AND GAME

Experiment I and II differed by about 24 months and II had about
25% more trawling time. Differences observed in species composition
and escapement may be linked to seasonal behavioral patterns. Some-
what greater retention of fish by the 5-inch cod end used in Experi-
ment II, compared to the 5^-inch mesh catch of Experiment I may
have been related to greater seasonal availability, smaller cod-end mesh,

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5-INCH MESH COO END

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208 FISH
161.8 LB

7H-INCH MESH COD END

28 FISH
17.4 LB

15

10

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NUMBER OF FISH

FIGURE 6. Comparison of Retention of Hornyhead Turbot in the 5- and 7V2-lnch Mesh Cod
Ends, 14 Paired Drags, 90 Min Each. Cruise 65-A-4.

CALIFORNIA HALIBUT ESCAPEMENT

93

longer dragging time and perhaps to species spawning behavior. More
kinds of invertebrates, sharks and rays, and teleosts were captured in
Experiment I than in Experiment II.

7V2-INCH MESH CODE END

5V2-INCH MESH COD END

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FIGURE 7. Comparison of Retention of Sand Sole in the 5- and 7V2-lnch Mesh Cod Ends,
14 Paired Drags, 90 Min Each. Cruise 65-A-4.

94 CALIFORNIA FISH AND GAME

Generally, except for halibut, fish of larger size escaped in greater
numbers through the 7.1-inch mesh (Figures 2. 3, 5, and 6). There was
complete escapement (except for one fish | by hornyhead turhots larger
than 300 mm (11.8 inches) from the 7 '-inch mesh cod end (Figure 2
and 6). With sand sole the reverse was true, smaller fish appeared to
escape while the larger ones were retained (Figure 7).

The 7^-inch mesh cod end provided almost complete escapement for
halibut less than 560 mm in Experiments I and II, but the 5- and
oi-ineh mesh retained many undersized unmarketable fish. Of the 422
halibut less than 560 mm (22 inches) captured in both experiments,
slightly more than 4% were retained by the 7^-ineh mesh cod end
and almost 96% were retained by the 5- and Si-inch mesh.

The difference in escapement between halibut and other flatfishes
is likely linked to the basic behavioral pattern of the particular species.
Hornyhead turbots feed mostly on clam siphons and fantail sole on
crustaceans (pers. comm. John E. Fitch). These feeding habits do not
require the aggressive pursuit that is needed by halibut which feed upon
elusive fish. It is probable that this aggressiveness of sub-legal halibut
provides motivation for their escapement through the 7.,-ineh cod end.

The 6.1 m (20 ft) 7.1-inch mesh trawl cod end is a suitable manage-
ment tool, retaining most legal sized halibut but providing escapement
of undersized (less than 22 inches total length) juvenile halibut that
are, by regulation, unmarketable.

The experiments show that fewer halibut of higher average weight
and with greater total weight were captured by the 7i-inch mesh cod
end than by the cod ends of smaller mesh size. The England Ministry
of Agriculture and Fisheries (n.d.) and E. S. Russell (1926) found
from their trawl experiments that this is true of other species.

REFERENCES

England. Ministry of Agriculture and Fisheries, n.d. The effect of using a larger

cod-end mesh. Fisheries notice, (21) : 1-8.
Russell, E. S., and T. Edser. 1D2G. The relation between cod-end mesh and size

of fish caught. Cons. Term. Inter. Explor. Mer. J. Cons., 1(1) : 39-H4.

Calif. Fish and Game, 61(2) : 95-103. 1975.

OBSERVATIONS ON THE FOOD HABITS OF LEOPARD

SHARKS (Triakis semifasciata) AND BROWN

SMOOTHHOUNDS (Mustelus fien/e/)1

By RONALD A. RUSSO

East Bay Regional Park District

Oakland, California 94619

Information on the food habits of the brown smoothhound (Mustelus
henlei) and leopard shark (Triakis semifasciata) was collected from May,
1970 through June, 1973. The stomach contents of 45 leopard sharks
and 25 smoothhounds from San Francisco Bay, California revealed similar
food habits as are found in Tomales Bay, California.

Of the smoothhounds examined, 39% contained shrimp, 35% crabs,
and 22% fish. Of the leopard sharks examined, 17% contained shrimp,
16% crabs, and 19% fish. The occurence of a significant quantity of
shore crabs [Hemigrapsus oregonensis) in smoothhounds indicates a
definite intertidal feeding habit, which is not evidenced by the quality
of food in leopard sharks. In addition, 17% of the leopard sharks con-
tained fish eggs, 9% clam necks, and 19% contained worms. While
shrimp, crabs and fish were important items in the diets of both sharks,
leopards are distinguished by the appearance of clam necks, worms,
and fish eggs in significant quantities. The occurrence of benthic forms
like Upogeb/a, Callianasa and Uteehis and various clam necks indicates
a shoveling or burrowing habit by leopard sharks in capturing prey.
This idea is supported by findings on concentrations of chlorinated
hydrocarbons in leopard and brown smoothhound liver tissues.

INTRODUCTION

Brown smoothhounds (Mustelus henlei) and leopard sharks (Triakis
semifasciata) are two of the most frequently encountered and abun-
dant sharks inhabiting the estuarine waters of central and northern
California. Brown smoothhounds are common, primarily in bays north
of Monterey, with extensive populations in San Francisco, Tomales
and Humboldt Bays (Herald and Ripley 1951; E. A. Best, Interna-
tional Pacific Halibut Commission, pers. comm.). Smoothhounds appear
to be scarce in Elkhorn Slough (Herald et al. 1960) and absent in
Morro Bay (Fierstine, et al. 1973). Leopard sharks are common from
Magdalena Bay, Lower California to Oregon (Miller and Lea 1972).

Both leopard and brown smoothhound sharks are typical bottom
forms. Both seem to spend an equal amount of time on or near the
bottom, even though an earlier report indicated that leopards spend
far less time near the bottom than smoothhounds (Russo and Herald
1968).

Although both of these sharks are frequently caught by sport fisher-
men and taken for food, little has been reported on their ecology and
natural history in the estuarine ecosystem. Questions by sport fisher-
men on the effect of these sharks on the fisheries, along with observa-
tions of large numbers of sharks dead and dying on the beaches of

1 Accepted for publication November, 1974.

(95)

96 CALIFORNIA FISH AND GAME

Alameda, California (Russo and Herald 1968), prompted me to in-
vestigate the dietary habits of these elasmohranehs.

In 1951, Herald and Ripley reported that brown smoothhounds fed
by preference on small crabs and shrimp in San Francisco Bay. Later,
in 1960, it was reported that leopard sharks in Elkhorn Slough fed
upon crabs, clams and fish, particularly the midshipman (Porichthys
notatus) (Herald, et al I960). Information on the food habits of both
these sharks has been sketchy and general in nature.

The purpose of this study was to accumulate data on the species
composition, and frequency of occurrence of their food items. In May
of 1970 I began analysing stomach contents from leopard and brown
smoothhound sharks as a part of a study of the sharks of San Fran-
cisco Bay. The occurrence of the Tomales Bay Shark-and-Ray Derby,
sponsored by the Petaluma Outdoorsmen in June of 1971 and 197:},
provided an opportunity for parallel analyses in a similar ecological
situation. Difficulties in obtaining use of a vessel on a regular basis,
foul weather, and problems with equipment, hampered attempts to
conduct a year-round seasonal analysis in San Francisco Bay. Most of
the observations made occur from the early spring months through
the summer. Within San Francisco Bay a small number of samples
were taken during the fall and winter months, though too few to reach
conclusions about seasonal patterns.

STUDY AREA

Sharks were collected in south San Francisco Bay from subtidal
waters between the Alameda Naval Air Station and Hunter's Point
Naval Shipyard to the west, then south to the San Mateo Bridge. Most
of the fishing was done within Alameda and San Francisco Counties.
The areas fished ranged in depth from 4.57-17.08 m (15-56 ft).

METHODS

All of the San Francisco Bay specimens were collected on 152 m long
(500 ft.) set lines using 5/0 hooks baited with squid. Most of the fish-
ing was done on the bottom, although a few sets were made with the
ends of the lines about 3-4.5 m (9.8 to 15 ft.) above the bottom. The
center of these lines rested near the bottom. The Tomales Bay speci-
mens were caught by rod and reel by derby contestants using squid
and sardines as bait. Fishing depth, hook size, and location of capture
varied.

All specimens were examined as soon as possible following capture.
Some sharks were observed regurgitating under the stress of capture
and handling. This may account for a small percentage of those in the
"empty" category. The stomach contents of each shark were separated,
analysed, identified and recorded prior to disposal. Spiral valves were
not examined. In some cases of field identification, it was possible to
identify individual food items to the species level, while in other cases
only the generic identity was possible. Because of the volume of
stomachs and contents analysed on site, it was not practical to preserve
food specimens for later analysis.

LEOPARD SHARK FOOD HABITS

97

TABLE 1 — Food Items of Leopard Sharks From San Francisco and Tomales Bay

1970-1973

Tomales Bay
(98)*

%Ft

Ft

San Francisco Bay
(45)*

%F

Totals
(143)*

%F

Shrimp
Crago, sp.,
Upogebia sp.,
Callianasa sp..

Crabs

Cancer Crabs
Cancer sp...

Fish
Perch

Cymatogaster aggregata.

Anchovy

Engraulis mordax

Goby

Clevelandia ios

Plainfin Midshipman

Porichthys natatus

Sanddab

Citharichthys sp

Bat Ray

Myliobatis californicus _
Brown Smoothhound

Mustelus hcnlei

Unidentified Fish

Fish Eggs
Herring

Clupea pallasi

Smelt

Atherinopsis sp

Plainfin Midshipman

Porichthys notatus..

Clam (Necks) .

Worms

Bristle Worm

Nereis sp

Fat Innkeeper

Urechis caupo.

Miscellaneous

Squid (Bait)

Eelgrass

Zostera marina.
Octopus

Octopus sp.

Empty.

14.3

13.3

3.06

1.02

4.08

4.08

2.04
5.10

16.3
2.04
12.2

2.04
16.3

9.18
14.3

1.02
31.6

14

13

16

2

12

2
16

9
14

1
31

22.2

22.2

4.44
2.22
4.44
2.22

6.66
15.5

2.22

2.22
17.7

6.66
17.7

10

10

16.8
16.1

2.09

2.09
.699

4.19
.699

2.79

1.39
5.59

4.89
11.2
1.39
9.09

2.09
16.8

8.39
9.77
.699
27.3

24

23

3

1
6

1

4

2
8

7
16

2
13

3
24

12

14

1

39

* Number of shark stomachs examined.

t Percentage frequency: percentage of stomachs which contained a given food item.

X Frequency: number of stomachs which contained a given food item.

The data presented in Tables 1 and 2 relate only to the number
of stomachs in which listed items occurred. Data on percentage fre-
quency (%F) and frequency (F) of occurrence of food items in
sharks' stomachs indicates those organisms which are commonly taken
and those taken less often for food. No attempt was made to determine
the percentage of volume of listed food items.

98

CALIFORNIA FISH AND GAME

RESULTS

During the collecting period from May, 1970 to June, 1973, a total
of 143 leopard sharks and 77 brown smoothhounds were processed.
Forty-five leopards and 25 smoothhounds from San Francisco Bay
were examined between May, 1970 and March, 1972. Ninety-eight
leopards and 52 smoothhounds from Tomales Bay were analysed for
food habits in June of 1971, and June, 1973.

Leopards from San Francisco Bay ranged in size from 53-130 cm
(21-51 inches), while Tomales Bay specimens ranged from 72-150 cm
(28-59 inches) (TL). Brown smoothhounds fiom San Francisco Bay
ranged from 53 to 87 cm (21-34 inches), while Tomales Bay speci-
mens ranged from 63 to 94 cm (25-37 inches) (TL).

While there is a bias in the unequal and low sampling of leopard
and brown smoothhound sharks, several comparisons can be made.
In both leopards and smoothhounds crabs, shrimps and miscellaneous

TABLE 2 — Food Items of Brown Smoothhound Sharks From
San Francisco and Tomales Bay, 1970-1973

Tomales Bay
(52)*

%Ft

Ft

San Francisco Bay
(25)*

%F

Totals

(77)*

%F

Shrimp
Crago sp.,
Upogebia sp.,
Callianasa sp

Crabs

Cancer Crabs

Cancer sp

Shore Crabs

Hemigrapsus oregonensis

Fish
Perch

Cymatogasler aggregates ._
Anchovy

Engraulis mordax

Goby

Clevelandia ios

Sanddab

Citharichthys sp

Unidentified Fish

Fish Eggs
Smelt

Atherinopsis sp

Worms

Bristle Worm

Nereis sp.. -

Miscellaneous

Squid (Bait)...

Sea Squirt

Molgula manhattensis

Empty

30.8

32.7

48.1

1.92

3.84

1.92
11.5

1.92

1.92

9.61
1.92
9.61

16

17
25

56.0

40.0
4.00

4.00
8.00
4.00

12.0

12.0

14

10

1

1
2
1

38.9

35.1
33.7

2.59

2.59

3.89

1.29
11.8

1.29

1.29

6.49
1.29
11.6

30

27
2fi

2

2

3

1
9

• Number of shark stomachs examined.

t Percentage frequency: percentage of stomachs which contained a given food item.

t Frequency: number of stomachs which contained a given food item.

LEOPARD SHARK FOOD HABITS 99

fishes are important food items (Tables 1 and 2). Generally, the range
of items selected by leopard sharks is broader than that of smooth-
hounds.

Many sharks contained a variety of items, while others had fed
extensively on a single type of food. It should be noted here that in all
cases except one, eel grass was found in association with fish eggs.
One leopard contained only a clump of eel grass within its stomach.
Over 27% of the leopards and 11% of the smoothhounds examined
had empty stomachs.

The composition of species taken by both sharks suggests behavioral
differences between the two in the areas where feeding takes place
(intertidal and subtidal) and the amount of time spent on or near the
bottom.

Food Items
Shrimp:

Shrimp belonging to three generic groups occurred in 39% of the
smoothhounds and 17% of the leopards. The blue mud shrimp (Upo-
gebia pugettensis) and whole specimens of the bay shrimp (Crago
franciscorum) appeared frequently: Upogebia and different species of
Crago dominated the type of shrimp taken by both sharks. Often the
partially digested remains of shrimp were not enough for species iden-
tification. On four occasions, pink ghost shrimp (Callianasa calif or-
niensis) appeared in the stomachs examined — one in a leopard and
three in different brown smoothhounds.

Since both Upogebia and Callianasa are burrowing forms that rarely
leave the shelter of their burrows, some questions are raised regarding
how they are captured. Both shrimp rise to the mud's surface to
discharge sand from their burrows and it is possible that capture
might occur at this point.

Crabs:

Crabs of the genus Cancer sp. were found in 16% of the leopards and
35% of the brown smoothhounds. Cancer crabs measured from 1.27 cm
(0.5 inch) across the carapace to over 4 cm (1.57 inches) in most cases.
One partially digested cancer crab measured 8 cm (3.1 inches) in
width. Cancer crabs usually occurred in quantity with as many as 14
occurring in the stomach of a brown smoothhound. Two young striped
forms of Cancer productus were found in a leopard. Other species
identification was made difficult by missing parts and advanced diges-
tion. Cancer was the only genus of crabs found in leopard sharks, even
though several other crabs exist in the same habitat and are potential
food.

Of notable distinction was the appearance of shore crabs (Hemigrap-
sus oregonensis) in 34% of the smoothhounds. Both Cancer and Hemi-
grapsus crabs are staple items in the diet of brown smoothhounds. It
was not uncommon to find half a dozen of each crab (Cancer and
Hemigrapsus) in the stomach of a single smoothhound. The frequent
occurrence of shore crabs in smoothhounds suggests intertidal feeding,
which is not evident in leopard sharks. Of interest, however, was the
absence in smoothhounds of other intertidal crabs such as H. nudus
and Pachygrapsus crassipes, which share the same environment as H.
oregonensis.

100 CALIFORNIA FISH AND GAME

Fish:

Various species of fish appeared in over 19% of the leopards and
22% of the smoothhounds examined. In general, a greater diversity of
fish was taken by leopards than smoothhounds. Shiner perch (Cymato-
rjaster aggregata), anchovies (Engraulis mordax), gobies (Clevelandia
ios), and sanddabs (Citharichthys sp.) were the main fishes occurring
in both leopard and smoothhound stomachs. In addition to these, 4%
of the leopard sharks also contained the plainfin midshipman (Porich-
thys not at us) . Midshipmen occurred more frequently than any other
species of fish in leopards. A 117 cm (46 inch) male leopard contained
a 23 cm (9 inch) midshipman. Other midshipmen were smaller. Mid-
shipmen were not found in smoothhounds. Anchovies appeared in 2%
of the leopards and smoothhounds, and often occurred in numbers
with as many as six full-grown anchovies in a shark's stomach. In July
of 1972 I visited the San Rafael Bridge after receiving reports from
Mike Valentine, engineer with the Division of Bay Toll Crossings.
Mike had reported seeing sharks within the walls of the bridge sup-
ports. This structure appears as a concrete box with four walls that
rise well above the high-tide mark and extend to within a few feet
of the bottom, but supported at the corners. The opening under the
support walls allows fish to move into the enclosure where currents
are subdued and where the fish become temporarily trapped. During
the field trip, we observed leopard sharks and spiny dogfish (Squalus
acanthias) capturing anchovies by swimming into oncoming schools
with their mouths open. No rapid or overt aggressiveness was noted.
Periodically an anchovy appeared to swim right into a shark's mouth.
Several leopard and dogfish sharks swam leisurely counter-clockwise
to the clockwise movement of anchovies within the perimeter of the
concrete walls. All of this took place at the surface, making observa-
tion easy.

San Francisco Bay Leopard sharks have not been known to eat other
elasmobranchs. Nor have other large sharks like sevengill cowsharks
Notorhynchus maculatus, which I have examined, been known to eat
leopard sharks. Two leopard sharks from Tomales Bay, however, con-
tained brown smoothhound pups (one per shark) measuring 23 cm
(9.06 inches) (TL). Other Tomales Bay leopard sharks contained pre-
maturely born bat rays (Myliobatis calif ornicns) . I suspect that leopard
sharks took advantage of the numbers of young rays and smoothhound
pups being dropped by the pregnant adults under the stress of capture
and handling. A 107 cm (42 inches) female leopard shark contained a
young ray which measured 15 em (5.9 inches) across. Two other leopard
sharks also contained young bat rays. One leopard shark had bitten
off the wing tip of a large ray. The piece measured 7.62 cm (3 inches)
across by 2.54 cm (1 inch) thick. Mature female bat rays examined at
dockside in Tomales Bay contained young of the same size and condi-
tion as those found in leopard sharks. No elasmobranchs were found
in smoothhounds.

Fish Eggs:

The appearance of fish eggs in sharks' stomachs was the only clear
evidence of a seasonal feeding pattern in this limited study. Fish eggs
are a much more important source of food to leopard sharks than to

LEOPARD SHARK FOOD HABITS 101

smoothhounds. Only 1% of the smoothhounds had taken eggs, while
17% of the leopard sharks fed on fish eggs.

Leopard sharks examined in February and March from south San
Francisco Bay contained large quantities of sticky eggs measuring
about 2 mm. each. Masses of these eggs were also found clinging to
set lines. Shark stomachs were often full of just fish eggs. Because of
the time of year and general nature of the egg masses, I believe these
to belong to herring (Clupea narengus pallasi).

Leopard sharks examined in June from Tomales Bay also included
vast quantities of eggs in their stomachs. Most of these 1 mm. eggs were
associated with eelgrass (Zostera marina). These eggs were grayish-
green, possessed a prominent integument and formed grape-like clus-
ters. Apparently these belong to smelt (Atherinopsis sp.) (Roger Green,
"Max" Eldridge, National Marine Fisheries Service, pers. comm.).
Sharks were often so engorged with eggs that regurgitation resulted
from handling. The stomachs of two leopards in the study held several
midshipman eggs in each. Since midshipmen normally lay their eggs
on the undersides of intertidal rocks, I can only think that these eggs
were taken under unusual circumstances.

During the spawning season for herring and smelt, thousands of eggs
are probably consumed by leopard sharks, and possibly other sharks.
This adds a new predator to the eggs of herring as discussed by Hard-
wick (1973).

Clam Necks:

While clam necks were totally absent in the smoothhounds examined,
they appeared as an important food item in leopard sharks. Clam
necks and a single clam foot appeared in 9% of the leopard sharks.
The upper sections of the necks had been bitten off. Most neck pieces
measured from 1.27 to 2.54 cm (0.5 to 1 inch) in length. Physical dif-
ferences among these neck pieces indicated that more than one species
of clam was involved. A 135 cm (53 inch) female leopard from Tomales
Bay contained 6 large necks thought to belong to the gaper or horse-
neck clam (Schizothaerus nuttali) . The 6 pieces measured from 8 to 13
cm (3.1 to 5.1 inches) in length, by 2.54 cm (1 inch) in diameter.

While diving I have observed the siphons of horseneck clams ex-
tending 8-10 cm (3 to 4 inches) out of the mud. The clam immediately
withdraws the siphon upon the slightest contact with any object. A
hungary leopard shark would have to have a quick and sharp bite to
obtain a clam neck of this size without having its face pulled into
the mud by the power of the horseneck. Other, smaller clams probably
do not extend their necks as far as Schizothaerus. For the shark, this
would result in smaller pieces of neck and more contact with bottom
sediments.

Another difference in feeding habits between leopard sharks and
brown smoothhounds was observed in the case of worms. Only one of
the smoothhounds examined contained a worm of any kind. In this case
it was a bristle worm (Nereis sp.). However, in the base of leopard
sharks, worms — like clam necks— proved an important food item. Less
than 3% of the leopards contained bristle worms, but more than 16%
of the leopards held the fat innkeeper (Urechis caupo). In many cases,
a leopard had eaten several 13 cm (5.1 inches) long whole specimens.

102 CALIFORNIA FISH AND GAME

One leopard contained 10 whole innkeeper worms, measuring about
10 cm (4 inches) each.

MacGinitie and MacGinitie (1068) stated that "Urechis is readily
eaten by fish or crabs, but, since it never leaves its burrow, the one
that is occasionally found in the stomach of a fish must be made a avail-
able to the fish by some disturbance of the mud significantly great to
expose Urechis. " Since leopards are known to take Urechis frequently
along with other nmd-dwelling forms like Upof/cbia, CaUianasa and
clams (necks), it appears as though the leopard shark may employ
some rapid burrowing, shoveling or side to side motion of the head to
expose and grasp these animals. Poor visibility usually prevents ob-
serving this phenomenon in the shark's natural environment.

Miscellaneous:

The only miscellaneous items that appeared in the shark stomach
samples worthy of note was a sea squirt (Molgula manhattensis) and
an octopus (Octopus sp.) .

A brown smoothhound from Tomales Bay contained several sea
squirts along with shrimp parts and crabs. None of the sea squirts were
attached to seaweed, as they are usually found in nature. On the same
day a leopard was found to contain a 5 cm (2 inches) long by 2.54 cm
(1 inch) thick section of an octopus tentacle. Digestion had not pro-
ceeded far and the suction discs were apparent. Another leopard shark
contained two 22-caliber bullet shells, several pebbles, and a single
Urechis.

DISCUSSION

Both leopard and brown smoothhound sharks are important elements
in the food web of estuarine communities. The evidence presented indi-
cates no significant effect on the quality of the bay sports fishery. While
anchovies are taken by both sharks and while leopards feed on smelt
and herring eggs, it seems doubtful that a decline in the shark popu-
lation would result in an improved fishery. Too many other predators
are involved. The types of other fishes taken by these sharks are not
generally regarded as important forasre fish for game species. Many of
the clams taken are probably subtidal and beyond the reach of the
sportsman.

This study suggests little or no intertidal feeding by leopards, even
though they are frequently caught by inshore fishermen, while estab-
lishing such behavior for smoothhounds. Since there arc also distinct
differences in the types of food taken by each shark, competition is
probably reduced, allowing each to co-exist in the same general environ-
ment. Because of the variety of benthic forms taken by leopards and
the frequency of leopards caught on bottom set lines, this shark may
spend more time on or near the bottom than previously thought.

Leopard shark feeding behavior apparently involves a disturbance
of bottom sediments as indicated by the food species involved. Although
shrimp are taken in quantity by smoothhounds, a similar form of
behavior is not otherwise indicated. Because sediments usually have a
higher concentration of pesticides than open water, bottom fishes that
regularly disturb the mud in capturing food may contain higher con-
centrations than similar midwater fishes or bottom fishes that do not

LEOPARD SHARK FOOD HABITS 103

disturb the mud. This idea is supported by pesticide analysis of liver
tissues from leopard and brown smoothhound sharks I collected. Pesti-
cide analyses of 5 liver samples from each of the 2 species of sharks
completed in 1969 at the Environmental Protection Agency laboratory
in Alameda, California, revealed that leopard sharks contained an aver-
age concentration of PCB (polychlorinated biphenyls) of 46.9 ppm,
while smoothhounds had an average of 22.5 ppm of PCB. The same
liver tissues revealed an average TICH reading (total identifiable
chlorinated hydrocarbons— which included DDT, DDD, DDE) of 108.2
ppm for leopards and 36.9 ppm for smoothhounds. While the effect of
these concentrations on the sharks was not determined, nor was any
"normal" concentration established, the data suggest that because of
a habit of nosing into the mud, leopards concentrate higher levels of
pesticides than smoothhounds who do not engage in this activity to
any great extent.

ACKNOWLEDGMENTS

I wish to express my appreciation to Paul Ferreira, Curtis Jones,
and Timothy Gordon of the East Bay Regional Parks and to the Sea
Scouts of Piedmont and Captain John Laingor for assistance in gather-
ing data from San Francisco Bay; to Dr. George W. Barlow of the
University of California, Berkeley, for editorial review and sugges-
tions ; to Roger Green and ' ' Max ' ' Eldridge of the National Marine
Fisheries Service for information on smelt eggs; to E. A. Best of the
International Pacific Halibut Commission for information on shark
ecology; to Michael Valentine of the Division of Bay Toll Crossings
for his interest and assistance ; to Constance Rogers for typing the
manuscript ; and finally, a posthumous debt of gratitude to Earl Herald
for his interest and encouragement in this endeavor.

•&

REFERENCES

Fierstine, Harry L.. Kurt F. Kline, and Gregory R. Garman. 1973. Fishes Col-
lected in Morro Bay. California Between January, 1968 and December, 1970.
Calif. Fish Game 59 (1) : 73-88.

Hardwick, James E. 1973. Biomass Estimates of Spawning Herring, Clupea
harengus pallasi, Herring Eggs, and Associated Vegetation in Tomales Bay.
Calif. Fish Game 59 (1) : 36-61.

Herald, Earl S., Walter Schneebeli, Norval Green, and Kenneth Innes. 1960.
Catch Records for Seventeen Shark Derbies Held at Elkhorn Slough, Monterey
Bay, California. Calif. Fish Game 46 (1) : 59-67.

Herald, Earl S., and William Ellis Ripley, 1951. The Relative Abundance of
Sharks and Bat Stingrays in San Francisco Bay. Calif. Fish Game 37
(3) : 315-329.

MacGinitie, G. E., and MacGinitie, Netti, 1968. Natural History of Marine Ani-
mals. McGraw-Hill Book Company, New York, 521 p.

Miller, Daniel J., and Robert N. Lea. 1972. Guide to the Coastal Marine Fishes
of California. Calif. Dep. Fish and Game, Fish Bull. (157) : 235 p.

Russo, Ronald A., and Earl S. Herald. 1968. The 1967 Shark Kill in San Fran-
cisco Bay. Calif. Fish Game 54 (3) : 215-216.

NOTES

A PRELIMINARY LIST OF FISHES COLLECTED FROM
RICHARDSON BAY, CALIFORNIA 1972-1973

From June 1972 to July 1973 sampling of fish eggs and larval,
juvenile and adult fishes was conducted by Tiburon Fisheries Labora-
tory (National Marine Fisheries Service, NOAA) in Richardson Bay,
a part of the San Francisco Bay system (Fig. 1). The sampling was
part of a pilot program to lead toward a more extensive baseline study
of fishery resources and their ecological relationships within and
dependence upon San Francisco Bay.

Richmond

PROJECT AREA

Berk e It i

FIGURE 1. Location Map.

Sampling for adult and juvenile fishes was conducted with gill nets
and trawls at 9 randomly selected stations each month with the excep-
tion of October 1972. The gill nets used were 6 ft in depth by 100 ft
long and made of monofilament nylon. Each net was constructed from
different panels laced together. The mesh sizes of these panels were
randomly selected from 1, 1£, 2, 2i, 3, 4 and 6 inch stretched mesh, each
size being used twice in the four nets that we used. At each station
selected, one net was fished for 2 hours at the surface. Often, in
waters less than 6 ft deep, the nets covered the entire water column.

The trawl was a standard shrimp "try net" with head rope length

(104)

NOTES 105

TABLE 1— Fishes Collected From Richardson Bay, 1972-1973

Scientific name

Mustelus henlei

Triakis semifasciata

Squalus acanthias

Raja trachura

Myliobatis californica

Acipenser medirostris

A losa sapidissima

Clupea harengus pallasi

Dorosoma petenense

Engraulis mordax

Hypomesus pretiosus

Porichthys notatus

Merluccius productus

Microgadus proximus

Brosmophycis marginata

Atherinops affinis

Atherinopsis californiensis

Syngnathus griseolineatus

Morone saxatilis

Trachurus symmetricus

Cynoscion nobilis

Genyonemus lineatus

Cymatogaster aggregata

Embiotoca jacksoni

Hyperprosopon argenteum

Hypsurus caryi

Micrometrus minimus

Phanerodon furcatus

Rhacochilus toxotes

Rhacochilus vacca

Neoclinus uninotatus

Clevelandia ios

Lepidogobius lepidus

Peprilus simillimus

Sebastes auriculatus

Hexagrammos decagrammus-.

Ophiodon elongatus

Enophrys bison

Leptocot*->is armatus

Oligocotius maculosus

Scorpaenichlhys marmoratus.

Citharichthys sordidus

Citharichthys stigmaeus

Paralichthys californicus

Hypsopsetta guttulata

Parnphrys retulus

Platichthys stellatus

Symphurus atricauda

Eggs or

Number of

larvae

juveniles or

Common name

collected

adults captured

Brown smoothhound

38

Leopard shark

42

Spiny dogfish

1

Roughtail skate

1

Bat ray-

4

Green sturgeon

3

American shad

1

Pacific herring

X

22

Threadfin shad

7

Northern anchovy

X

9

Surf smelt

5

Plainfin midshipman

16

Pacific hake

X

Pacific tomcod

34

Red brotula

X

Topsmelt

265

Jacksmelt

351

Bay pipefish

X

14

Striped bass

72

Jack mackerel

X

White seabass

X

White croaker

1

Shiner perch

1,716

Black perch

49

Walleye surfperch

23

Rainbow seaperch

9

Dwarf perch

133

White seaperch

1,353

Rubberlip seaperch

8

Pile perch

93

Onespot fringehead

1

Arrow goby

1

Bay goby

3

Pacific pompano

1

Brown rockfish

9

Kelp greenling

1

Lingcod

16

Buffalo sculpin

2

Pacific staghorn sculpin

X

176

Tidepool sculpin

X

Cabezon

1

Pacific sanddab

X

7

Speckled sanddab

165

California halibut

X

Diamond turbot

X

3

English sole

674

Starry flounder

X

70

California tonguefish

X

of 20 ft and foot rope of 23^ ft. Otter boards measured 1 ft by 2 ft
and were hung from 10 ft bridles. Mesh size in the main body of the
net was If inch stretched mesh with 1 inch stretched mesh in the cod
end. The trawl was always fished on the bottom. At each station, one
3-minute tow was made at a speed of 3.5 knots.

Ichthyoplankton was sampled with surface plankton tows using a
half-meter net and on 24-hr monitoring stations using an anchored
channel net (Lewis, et al. 1970). Three-minute tows were made in
replicates of two at 15 randomly selected stations each 6 weeks. Each
12 weeks, 24-hr monitoring was conducted at 2 fixed stations, one in
the main ship channel off the Corps of Engineers dock in Sausalito,
the other inside Cone Kock, near the mouth of Kichardson Bay. The

106 CALIFORNIA FISH AND GAME

direction of the channel net was reversed at each tidal change.

All of the juvenile and adult fish sampling and surface plankton
tows were conducted during daylight hours.

This preliminary list (Table 1.) of fishes collected and their relative
abundance in the catch is published here for the possible interest of
other workers in the shallow areas of San Francisco Bay. Two species
in this list have not to my knowledge been reported previously from
San Francisco Bay: roughtail skate (Raja trachura) and white seabass
(Cynoscion nobilis). Unaware of its rarity, I identified the male rough-
tail skate in the field, using Miller and Lea's (1972) guide and re-
turned it to the water. It was caught in the trawl on May 31, 1973.
The white seabass larva was collected and identified by Maxwell Eld-
ridge (Tiburon Fisheries Laboratory) in June 1972. Identification was
verified by Elbert H. Ahlstrom. The specimen is preserved in the
reference collection at Tiburon Fisheries Laboratory.

I do not presume that the list is completely representative of fishes
found in Kichardson Bay. Shortcomings of gear and sampling methods
normally preclude this possibility. Much of the plankton material is
still being worked up. We expect additional species will show up in
these collections. More detailed publications will follow a more inten-
sive examination of our data and collected materials.

REFERENCES

Lewis, R. M., W. F. Hettler, Jr., E. P. H. Wilkens, and G. N. Johnson. 1970.
A channel net for catching larval fishes. Chesapeake Science. 11(3) : 19G-197.

Miller, D. J. and R. N. Lea. 1972. Guide to the coastal marine fishes of Cali-
fornia. Calif. Dep. Fish and Game, Fish Bull. (157) : 1-235.

— Roger E. Green, Tiburon Fisheries Laboratory, National Marine
Fisheries Service, NOAA, P.O. Box 98, Tiburon, California 94920.
Accepted June 1974.

CHANGES IN THE SPECIES COMPOSITION OF SHARKS
IN SOUTH SAN FRANCISCO BAY

Sharks were collected in San Francisco Bay between the Dumbarton
and San Mateo Bridges between May, 1972 and April, 1973. Data
collected from this 57 km 2 (22 mile 2) area were used to examine cyclic
changes in shark species composition. Herald (1951) using data com-
piled from the annual summer shark derbies at Coyote Point located
3.2 km (2 miles) north of this collecting area, noted yearly changes
in species composition and abundance. This is the first published study
examining the general seasonal changes in shark abundance and species
composition in San Francisco Bay.

Marine Ecological Institute, Redwood City, California, provided the
78-foot research vessel, Inland Seas, for the collection of specimens.
Collection stations are shown in Figure 1. Catches from all stations
have been combined for analysis.

The three capture methods used in this study were: otter trawl,
deployed from the Inland Seas; a twelve hook set line, deployed along-
side the anchored vessel ; and rod and reel. The latter two methods
used No. 3 snelled hooks. Cut anchovv was used for bait.

NOTES

107

NAUTICAL MILES

Sampling Stations
South fBan Francisco
Bay

1372^373

FIGURE 1. Sampling stations — South San Franisco Bay — 1972-1973.

108

CALIFORNIA FISH AND GAME

Sharks were weighed and measured and inspected for external para-
sites upon capture. The species, sex and general physical condition of
each shark was also noted.

Shark specimens were preserved in 15% formalin. A slit through the
ventral surface insured internal organ preservation. Stomachs used in
food analj'sis were removed immediately, and only the stomach itself
was preserved. Volumetric and quantitative analysis of the food items
was performed within 1 week of capture.

TABLE 1 — Monthly Catches of All Species Expressed as Total Number of Individuals

Month

No.

samples*

M.

henlei

T.
semifasciata

S.
acanthias

-V.

maculatus

O.

zyopterus

May (1972)

June

11
4
6
4
2
5
7
3
2
5

n

3

6

9

28

49

3

14

18

4

0

1

0

0

19
5
5
7
1
8

11

16
1
2
5

12

0

0

0

0

0

0

10

8

2

20

17

7

0
0
0
0
0
1
0
0
0
0
0
0

0
2

July..

0

August.. .

0

September

October

November

December

January (1973)...

February

March

0
0
0
0
0
0
0

April

0

Total

63

131
(45.2)

92

(31.7)

64
(22.0)

1

(0.36)

2

Percent of total..

(0.74)

* Sample = One (1) deployment of each method at each station per month.

TABLE 2 — Monthly Percentages of the Shark Species Catches Expressed as Percent
of the Total

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

M. henlei

24

76

0

0

0

56
31

0
13

0

85

15

0

0

0

88

12

0

0

0

75
25

0
0
0

61
35

0

0

4

46
28
26

0
0

9

57

34

0

0

0

33

67

0

0

4

9

87

0

0

0
23

77
0
0

0

T. semifasciata

S. acanthias

63

37

G. zyopterus

0

N. maculatus

0

Numbered tags were tied around the openings of the extruded stom-
achs for identification. Volumetric analysis of the contents wTas per-
formed using a water-filled graduated cylinder. Displacement of the
water column by the added contents was measured as the total volume.
Individual food items were removed and the volume of each item
measured using a similar process.

Brown Smoothhound, Mustelus henlei

Constituting 45.2% (131/290) of the total catch, the brown smooth-
hound was most numerous in the catches from June through September
(Table 1, 2). Females outnumbered males 2.3 to 1, and averaged 58.6
cm (28 inches) while the males averaged only 41 cm (20 inches).
Herald (1951) states that this species constitutes about 45 to 50% of
the total shark population in San Francisco Bay. The results of this
study agree with this statement, however, no brown smoothhounds

NOTES

109

were collected in this study, from January through April, 1973. There-
fore, it may be said that in comprising a majority of the shark popula-
tion on a yearly basis, winter and spring months find few, if any, of
this species present in the south bay.

Bane (1971) states that the brown smoothhound females reach ma-
turity at about 76 cm Of the 13 specimens of this species and
size, all were females, and 5 of the 13 had embryos within the uteri.
Varying in degrees of development, the size of these embryos ranged
from 3 to 19 cm. The smallest specimen of brown smoothhound cap-
tured in this study was a 19 cm male, collected in July, 1972; numerous
brown smoothhounds ranging from 20 to 23 cm were collected through-
out the summer months.

Leopard Shark, Triakis semifasciata

This species was the second most abundant collected in the study.
Constituting 31% (92/290) of the total, leopard sharks were collected
in every month of the year. The leopard shark was the dominant species
in the spring months, May, 1972 and April, 1973, constituting 76 and
63% of the month's catches, respectively.

The largest shark collected in this study was a female leopard shark
measuring 121 cm (59 inches) and weighing 7.7 kg (17 lbs.). This
specimen had six 10 cm embryos within the uteri. No other female
leopard sharks were found to have developing young, however, five
females over 110 cm did have eggs within the uteri. These eggs ranged
from 2 to 5 cm in diameter.

As in the brown smoothhound, females were consistently larger than
males, averaging 65 and 49 cm respectively. Males and females, how-
ever, were about equal in number (45 to 47).

Spiny Dogfish, Squalus acanthias

The spiny dogfish, enumerated by Herald (1953) as the second most
abundant shark in the south San Francisco Bay, was the dominant
species during the winter months in the study. Constituting only 22%
(64/290) of the total catches, this species outnumbered all others from
January, 1973 through March, 1973, ten to one (Table 1, 2).

Females, outnumbered males 7 to 1 (56 to 8) and were larger, aver-
aging 77 cm total length, and weighed, on the average, in excess of
five pounds. Males ranged in length from 65 to 80 cm, averaging 71 cm.

Females were found to be numerous in the study area and tended
to school by size. A large school was found near the San Mateo Bridge,
in January and February, however, this species could be caught
throughout the entire south bay during the winter months. As many as

TABLE 3 — Percentages of the Food Items of Three Species of Sharks Collected
From San Francisco Bay '

Crabs

Isopods

Shrimp

Worms

Fish

Clams

Fish eggs

Misc.

M. henlei (57) 2

28.6

12.7

2.4

27.4
2.8
0.0

19.5

9.0

11.7

12.3

63.7

0.0

5.4

5.1

83.5

0.0
7.0
0.0

0.0
5.0
0.0

6.8
0.0

2.4

T. semifasciata (26)

S. acanthias (28)

1 Percentages indicate number of specific items/total number of all food items X 100.

2 ( ) indicates number of stomachs analyzed.

110 CALIFORNIA FISH AND GAME

15 spiny dogfish all within 2 cm in length were caught, using hook and
line and set line methods, in one 90-minute period in January, 1973.

Soupfin Shark, Galeorhinus zyopterus

The soupfin shark, historically an important Vitamin A source
(Templeman 1944), was represented by only two specimens in this
study. Both of these, a 72 cm male and a 76 cm female, were collected
in June, 1972. Constituting only 0.74% of the total catch, the decline of
this species, apparently due to extensive fishing, has been noted by
Herald (1951) and others for some time.

Sevengill Shark, Notorynchus maculatus

A single 76 cm male sevengill shark, collected in October, 1972. was
the only specimen of this species collected.

Food Habits

One of the purposes of this study was to examine differences in food
habits, as well as species composition of the sharks collected.

Crabs, predominantly Hcmigrapsus orcgonensis, constituted the
largest number of items of brown smoothhound, followed by isopods,
shrimp and polychaete worms (Table 3). Clam reivains and siphons,
present in the stomachs of leopard sharks were absent in brown smooth -
hounds. Both of these shark species are considered benthic feeders by
Herald, thus the absence of clam shells and siphons in brown smooth-
hounds is unexplained.

Polychaete worms, constituting only 12.3% of the items in brown
smoothhound were most numerous (63.7%) in the diet of leopard
sharks. Crabs, shrimp, clams, and fish as well as atherinid eggs followed
in abundance in the diet of leopard sharks.

Spiny dogfish apparently preferred pelagic fish to the embiotocids
found in leopard sharks' diets. Consisting predominantly of striped
bass (Morone saxatilis), and jacksmelt, (Atherinopsis calif or nicnsis)
fish items consituted 83.5% of the food items of spiny dogfish. Scales
within the stomachs of the spiny dogfish indicated that on at least one
occasion, the shark had been feeding on a 7 year old striped bass.
Anchovies, other than bait items, and herring also were present in the
stomachs of spiny dogfish.

Distinct changes in the species composition of the shark population
were observed in records of catches covering a full year. The brown
smoothhound, most numerous in the summer months, disappeared from
the catches in January, March and April. The leopard shark, collected
every month, was the dominant species in the early spring, while the
spiny dogfish appeared from November through March.

Forty-two brown smoothhound ranging in size from 19 to 25 em
constituted the smallest specimens collected. This data tends to support
the premise that San Francisco Bay is indeed a nursery ground for
some species of sharks, apparently brown smoothhound and spiny dog-
fish.

Food habit differences for the three dominant species is one reason
for the coexistence of these species in a small area throughout the year.

The percentages enumerated in this study, because of the unusually
heavy rainfall recorded in 1972-73 and subsequent decrease in salinity

NOTES 111

and water temperatures of San Francisco Bay, may not be indicative
of a "normal" species composition of bay sharks. It is, however, indic-
ative of distinct changes in species composition during the year.

REFERENCES

Bane, G. W., and A. W. Bane, 1971 Bay Fishes of Northern California. Mariscos

Publications, New York, 143 pages.
Herald, E. S., and W. E. Ripley, 1951 The Relative Abundance of Sharks and Bat

Stingrays in San Francisco Bay, California Fish & Game 37(3) : 315-329.
Herald, E. S., 1953 The 1952 Shark Derbies at Elkhorn Slough, Monterey Bay, and

at Coyote Point, San Francisco Bay, California Fish & Game 39(2) : 237-243.
Templeman, W., 1944 The Life History of the Spiny Dogfish (Squalus acanthias)

and the Vitamin A values of the Dogfish Oil, Fish Bulletin 15, Newfoundland,

Department of Natural Resources, 76 pages.

— Leray A. de Wit, Dames and Moore, Marine Services, 1100 Olendon
Ave., Los Angeles 90024. Accepted November, 1974.

FIRST CALIFORNIA RECORD OF THE SERRANID
FISH ANTHIAS GORDENSIS WADE

EDMUND S. HOBSON

During February, 1974, James R. Chess and I collected a single
specimen of Anthias gordensis Wade, 102 mm (4 inches) standard
length (sl) (Figure 1), at Ship Rock, Santa Catalina Island (33° 28'
N, 118° 29' W). When speared, this fish was the only member of its
species seen amid a large aggregation of blacksmith, Chromis puncti-
pinnis, that hovered close above a rocky ledge at a depth of about 40 m
(132 ft). The specimen, now in the fish collection at Scripps Institution
of Oceanography (SIO 74-22), was identified by Richard H. Rosen-
blatt of that institution.

Anthias gordensis was described by Wade (1946) from a 127 mm
(5 inch) sl holotype and a 130 mm (5.1 inch) sl paratype, both
dredged at a depth of about 150 m (495 ft) near inner Gorda Bank,
Cape San Lucas, Lower California, Mexico. Dr. Rosenblatt (pers.
comm.) observed large numbers of this species from the Cousteau div-
ing saucer at depths between 100 and 200 m (330 and 660 ft) at Cape
San Lucas, but because this fish inhabits infrequently sampled deeper
reefs, relatively few specimens have been collected. Until now, the
northernmost record of the species is a single individual 205 mm (8.1
inches) sl taken near the bottom 110 m (363 ft) deep at Guadalupe
Island, Mexico (29° N, 118° 30' W), by Albert Stover, Scripps Institu-
tion of Oceanography (SIO 63-161).

Only one other species of this genus has been reported from the
eastern Pacific: Anthias sechurae (Barton) from Peru, based on a 188
mm (7.4 inch) sl holotype and a 192 mm (7.6 inch) paratype (Barton
1947). Hildebrand and Barton (1949) recognized that A. sechurae
may be a junior synonym of A. gordensis, with differences in descrip-
tions being partly due to differences in size between type specimens,
but the question remains unresolved.

The following combination of characters of the specimen from Santa
Catalina Island confirm its identity : dorsal X, 15 ; anal III, 7 ; body
depth and head both 3 in standard length; eye 3.7 in head; scales

112 CALIFORNIA FISH AND GAME

ctenoid, 48 on lateral line; head and maxillary scaled, dorsal and anal
fins without scales.

Stomach contents of the specimen from Santa Catalina Island, identi-
fied by James R. Chess, and ranked as percentage by volume of
identifiable material, were as follows: 67 calanoid copepods, 0.6 to 1.2
mm (0.02 to 0.05 inch) long, 75$ ; 14 cyclopoid copepods, 0.8 mm
(0.03 inch) long, 10%; 6 euphausid larvae, 1.0 mm (0.04 inch) long,
5%; and 9 fish eggs, 1.0 mm (0.04 inch) in diameter, 10%. Clearly
this fish is a planktivore, as is the blacksmith (Quast 1968), with which
it was swimming when collected.

■in

REFERENCES

Barton, O. 1947. Two new fishes, an Eques and a Holanthias, from Peru.
Amer. Mus. Nov. (1350) : 1-3.

Hildebrand, S. F., and O. Barton. 1949. A collection of fishes from Talara, Peru.
Smithsonian Misc. Coll. 111(10) : 1-36.

Quast, J. C. 1968. Observations on the food of kelp bed fishes, p. 109-142. In
W. J. North and C. L. Hubbs (eds.), Utilization of kelp-bed resources in southern
California. Calif. Dep. Fish Game, Fish Bull. (139) : 1-264.

Wade, C. B. 1946. New fishes in the collections of the Allan Hancock Founda-
tion. Allan Hancock Pac. Eped. 9(8) : 215-236.

— Edmund S. Hobson, Tiburon Laboratory, Southwest Fisheries Cen-
ter, National Marine Fisheries Service, P.O. Box 98, Tiburon, Cali-
fornia 94920. Accepted November 1974.

V

FIGURE 1. Specimen of Anthias gordensis Wade, 102 mm SL, collected at Santa Catalina
Island (SIO 74-22).

A87293 — 800 12-74 5M LDA

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