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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

The free mailing list will be limited by budgetary considera-
tions to libraries, scientific institutions, and conservation agencies.

Subscriptions must be renewed annually by returning the post-
card enclosed with each October issue. Subscribers are asked to
report changes in address without delay.

Please direct correspondence to:

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

Individuals and organizations who do not qualify for the free
mailing list may subscribe at a rate of $5 per year or obtain
individual issues for $1 .50 per copy by placing their orders with
California Department of Fish and Game, 1416 Ninth Street,
Sacramento, California 95814. Money orders or checks should
be made out to California Department of Fish and Game, 1416
Ninth Street, Sacramento, California 95814. Inquiries regarding
paid subscriptions should be directed to the editor.



u













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%
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 m 2 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 ft 2 ) 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% . 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/m 2 (4.9 ft 2 ), while the same station
had a density of 1-2 clams/m 2 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 m 2 (10.76
ft 2 ) 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 m 2 (10.76 ft 2 ). 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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76



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

. 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)


(N = I)'


2.


2.3mm (N = 1)2


3


(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 H 2 0, and 5 g I 2 in 50 ml H 2 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


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