Biological Report 8Wl-84)

September 1988

TR EL-82-4

Species Profiles: Life Histories and

Environmental Requirements of Coastal Fishes

and Invertebrates (Pacific Southwest)

CALIFORNIA SEA MUSSEL AND BAY MUSSEL

QL

155

.S63

no.82-

11.84

Fish and Wildlife Service

Coastal Ecology Group

Waterways Experiment Station

U.S. Department of the Interior U.S. Army Corps of Engineers

Biological Report 82(11.84)

TR EL-82-4

September 1988

Species Profiles: Life Histories and Environmental Requirements

of Coastal Fishes and Invertebrates (Pacific Southwest)

CALIFORNIA SEA MUSSEL AND BAY MUSSEL

William N. Shaw

Fred Telonicher Marine Laboratory

Humboldt State University

Trinidad, CA 95570

Thomas J. Hassler

U.S. Fish and Wildlife Service

California Cooperative Fishery Research Unit

Humboldt State University

Arcata, CA 95521

and

David P. Moran

U.S. Fish and Wildlife Service

National Wetlands Research Center

1010 Gause Boulevard

Slidell, LA 70458

Project Officer

Carroll Cordes

U.S. Fish and Wildlife Service

National Wetlands Research Center

1010 Gause Boulevard

Slidell, LA 70458

Performed for

Coastal Ecology Group

Waterways Experiment Station

U.S. Army Corps of Engineers

Vicksburg, MS 39180

and

U.S. Department of the Interior

Fish and Wildlife Service

Research and Development

National Wetlands Research Center

Washington, DC 20240
This series may be referenced as follows:

U.S. Fish and Wildlife Service. 1983-19 . Species profiles: life histories

and environmental requirements of coast3 fishes and invertebrates. U.S. Fish

Wildl. Serv. Biol. Rep. 82(11). U.S. Army Corps of Engineers, TR EL-82-4.

This profile may be cited as follows:

Shaw, W.N., T.J. Hassler, and D.P. Moran. 1988. Species profiles: life

histories and environmental requirements of coastal fishes and invertebrates

(Pacific Southwest)--California sea mussel and bay mussel. U.S. Fish Wildl.

Serv. Biol. Rep. 82(11.84). U.S. Army Corps of Engineers, TR EL-82-4. 16 pp.
PREFACE

This species profile is one of a series on coastal aquatic organisms,

principally fish, of sport, commercial, or ecological importance. The profiles

are designed to provide coastal managers, engineers, and biologists with a brief

comprehensive sketch of the biological characteristics and environmental

requirements of the species and to describe how populations of the species may be

expected to react to environmental changes caused by coastal development. Each

profile has sections on taxonomy, life history, ecological role, environmental

requirements, and economic importance, if applicable. A three-ring binder is

used for this series so that new profiles can be added as they are prepared.

This project is jointly planned and financed by the U.S. Army Corps of Engineers

and the U.S. Fish and Wildlife Service.

Suggestions or questions regarding this report should be directed to one of

the following addresses.

Information Transfer Specialist

National Wetlands Research Center

U.S. Fish and Wildlife Service

NASA-Slide11 Computer Complex

1010 Gause Boulevard

Slidell, LA 70458

or

U.S. Army Engineer Waterways Experiment Station

Attention: WESER-C

Post Office Box 631

Vicksburg, MS 39180

iii
CONVERSION TABLE

Metric to U.S. Customary

Multiply !!Y

millimeters (mm) 0.03937

centimeters (cm) 0.3937

meters (m) 3.281

meters (m) 0.5468

kilometers (km) 0.6214

kilometers (km) 0.5396

square meters (m*) 10.76

square kilometers (km*) 0.3861

hectares (ha) 2.471

liters (1)

cubic meters (m3)

cubic meters (m3)

milligrams (mg)

grams (9)

kilograms (kg)

metric tons (t)

metric tons (t)

kilocalories (kcal)

Celsius degrees ("C)

inches 25.40 millimeters

inches 2.54 centimeters

feet (ft) 0.3048 meters

fathoms 1.829 meters

statute miles (mi) 1.609 kilometers

nautical miles (nmi) 1.852 kilometers

square feet (ft*)

square miles (mi*)

acres

0.0929 square meters

2.590 square kilometers

0.4047 hectares

gallons (gal)

cubic feet (ft3)

acre-feet

3.785 liters

0.02831 cubic meters

1233.0 cubic meters

ounces (oz) 28350.0

ounces (oz) 28.35

pounds (lb) 0.4536

pounds (lb) 0.00045

short tons (ton) 0.9072

0.2642

35.31

0.0008110

0.00003527 ounces

0.03527 ounces

2.205 pounds

2205.0 pounds

1.102 short tons

3.968 British thermal units

1.8('C) + 32 Fahrenheit degrees

U.S. Customary to Metric

To Obtain

inches

inches

feet

fathoms

statute miles

nautical miles

square feet

square miles

acres

gallons

cubic feet

acre-feet

milligrams

grams

kilograms

metric tons

metric tons

0.2520 kilocalories

0.5556 (OF - 32) Celsius degrees

iv

British thermal units (Btu)

Fahrenheit degrees (OF)

4
CONTENTS

PREFACE ................................................................ iii

CONVERSION FACTORS ..................................................... i v

ACKNOWLEDGMENTS ........................................................ vi

NOMENCLATURE/TAXONOMY ..................................................

MORPHOLOGY/IDENTIFICATION AIDS .........................................

California Sea Mussel ................................................

Bay Mussel ...........................................................

REASON FOR INCLUSION IN SERIES .........................................

LIFE HISTORY ...........................................................

Spawning .............................................................

Larval Stage .........................................................

Postlarvae and Recruitment ...........................................

Maturity .............................................................

Age and Growth .......................................................

COMMERCIAL AND SPORT FISHERIES AND AQUACULTURE .........................

ECOLOGICAL ROLE ........................................................

Feeding ..............................................................

Competitors ..........................................................

Predators ............................................................

Commensals, Parasites, and Encrusting Epifauna .......................

ENVIRONMENTAL REQUIREMENTS .............................................

Temperature and Salinity .............................................

Habitat ..............................................................

Physical Disturbance .................................................

Other Environmental Factors ..........................................

Page

11

1 1

11

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3

V
ACKNOWLEDGMENTS

We acknowledge the reviews by James Peterson, Los Angeles County Natural

History Museum, and Michael Martin, Califor'nia Department of Fish and Game.

vi
Figure 1. Shells of the California sea mussel (A), and bay mussel (B).

CALIFORNIA SEA MUSSEL AN0 BAY MUSSEL

NOMENCLATURE/TAXONOMY

Scientific name . . . . . . . Mytilus

californianus Conrad

Preferred common name . . California

sea mussel (Figure 1A)

Other common names . . . Rock mussel,

big mussel, California mussel, sea

mussel

Scientific name . . . Mytilus edulis

Linnaeus

Preferred common name. . . Bay mussel

(Figure 1B)

Other common names . . .Edible mussel,

black mussel, blue mussel, pile mussel

Geographic range: The California sea

mussel ranges from the Aleutian

Islands to Socorro Island, Mexico

(California distribution is shown in

Figure 2) and the bay mussel from

the Arctic Ocean to Cape San Lucas,

Baja California (Fitch 1953).

MORPHOLOGY/IDENTIFICATION AIDS

California Sea Mussel

Umbo at extreme anterior end of

shell. Shell covered with a heavy,

black periostracum. Older specimens,

from which this covering is worn off,

are blue and have an eroded

appearance. Exterior of shell with

radiating ridges and concentric growth
TOMALES BA

SAN FRANCISCO BA

PACIFIC OCEAN

0

0N

I

p!zmq Mytills adulis

mh4ytilus californianus

Mytilus edulis

NEVADA

\

‘\

\

\

CALIFORNIA

Y LOS ANGELES

* SAN DIEGO

KILOMETERS

J--___

- -

Figure 2. Coastal distribution of the California sea mussel and bay mussel in

California.

2
lines. Interior of shell bluish-black

iridescence shows in reflected light.

Length to 25 cm. Differs from the bay

mussel in having up to a dozen broad

radial ribs (Fitch 1953).

Bay Mussel

Shell wedge-shaped, with umbos at

extreme anterior tip. Periostracum

usually heavy, smooth, satiny black.

Interior of shell smooth, blue-black

around margin, and showing some

iridescence in reflected light. Flesh

a dull brolmish-orange. Length to 10

cm. Differs from the California sea

mussel partly in having a smooth exterior unmarked by radiating ridges and

grooves (Fitch 1953).

REASONS FOR INCLUSION IN SERIES

The California sea and bay

mussels are relatively common along

the rocky coastline and in bays and

estuaries. They support a small

commercial bait fishery and are

cultured for food on a small scale in

Tomales Bay and just north of San

Diego.

The areas of greatest potential

for the commercial harvest of M.

edulis in California for food, Tn

descendinn order of imoortance. are

Humboldt -Bay, Tomales ’ Bay, Drakes

Estero, San Francisco Bay, Elkhorn

Slough, Morro Bay, San Diego Bay, and

Tijuana Bay (Chalfant et al. 1980).

Mussels are an important food

item throughout the world. There is a

potential for culturing both of these

species for food more extensively in

California. Problems associated with

such culturing are seasonal closures

caused by pollution and paralytic

shellfish poisoning (PSP), finding

appropriate culture sites, and

obtaining public acceptance to use

these sites.

Man's manipulation of the coastal

zone could provide additional habitats

for mussels. Piers, floating marinas,

jetties, and pilings for oil rigs are

examples of surfaces ideal for

settling mussels. In fact, in

Humboldt Bay. California. the onlv

substantial -population of- M. edulis

occurs on the under surfaces-of floats

in a newly constructed marina.

LIFE HISTORY

Spawning

The California sea mussel

continually spawns throughout the year

at a very low level (Suchanek 19811,

with breeding peaks in July and

December (Morris et al. 1980). In

northern California, Edwards (1984)

found no definite spawning cycle.

Ripe mussels were seen from February

to May and from December to February.

Spawning was observed in January,

February, May, and December.

The bay mussel has a single

massive spawning output each year

(Suchanek 1981) which can occur in

late fall and/or winter along the

central California coast (Morris et

al. 1980). In northern California

spawning was first observed in May and

again from July through November

(Edwards 1984).

In the laboratory, spawning has

been stimulated by raising and

lowering the water temperature, adding

single cell algae, using water treated

with ultraviolet light, adding mussel

sperm, and using water containing

hydrogen peroxide. Breese et al.

(1963) found 4% Kraft mill effluent to

be a highly effective stimulus in

triggering mussel spawning. In the

natural environment, temperature does

not seem to provide a major stimulus

for spawning. Mechanical stimuli,

such as pulling on the byssal threads,

may initiate the release of gametes.

Also, spawning of one animal may

stimulate others to spawn (Morris et

al. 1980).
During spawning the eggs and

sperm are discharged through the

excurrent chamber. The eggs, which

appear as orange ribbons, are

fertilized in the open water.

Larval Stage

The embryos develop into

trochophore larvae (60-80 micrometers)

about 24 h after fertilization. The

veliger (straight-hinge stage) develops 24 h later (Figure 3A). A

ciliated velum forms and helps the

larva swim and maintain itself in the

water column. Larvae feed on

phytoplankton and are about 0.17 awn

long after 1 week. The veliger, which

develops an umbo, may reach a length

of 0.20 to 0.24 mm in 2 weeks.

Loosanoff and Davis (1963) found that

the size of mussel larvae (M. edulis)

at metamorphosis varied by almost 0.09

mm; lengths ranged from 0.21 mm to

almost 0.30 mm in length (Figure 3K).

Just before metamorphosis, the larva

develops an eyespot and foot.

The larvae of M. californianus

have been reared in tithe laboratory to

metamorphosis in 17-24 days after

fertilization. Eyespots were observed

when the larvae were 0.23 to 0.24 mm

long (Skidmore and Chew 1985).

Breeding success or failure is

frequently determined during the

critical larval stage. The larvae are

at the mercy of currents and may be

carried away from setting areas and

die.

Postlarvae and Recruitment

Mytilus edulis sets on the byssal

threads of adults, on a variety of

algae, and on newly exposed hard

surfaces; M. californianus sets on

barnacles, old mussel shell, and newly

exposed hard surfaces (Petraites

1978). In California, M. edulis

settled immediately on scraped, bare

substrate (i.e. no succession

occurred) in winter and spring; it did

not settle in summer and fall (Reish

1964). Density of newly settled M.

californianus was highest on filamentous algae (Peterson 1984). The

author observed in the laboratorv that

M. edulis larvae avoided adult M.

californianus. Investiaators disaaree

about settling behavior: For exam/;le,

the presence of adult M. edulis may

inhibit larval settlemeni. Seed mussels appear to set elsewhere, and then

migrate to adult beds, where they

attach to byssal threads of the adults

wherever there is space (Jamieson et

al. 1975). M. californianus preferred

to set on b&Sal threads from adults

(Trevelyan and Chang 1983).

In southern California M. edulis

settles in massive numbers-inyears, but sparsely in others (Morris

et al. 1980). In areas where both

species have settled, M. edulis was

the more mobile and was generally

found on the outer part of the colonies. It was also more susceptible

to wave action. californianus Mytilus

holds its position more strongly than

does M. edulis (Harger 1970a).- _

Chalfant et al. (1980) stated

that settlement of M. edulis was

generally gregarious; in Maine, for

example, mussel

exceeding 300,000/m2

spat densities

have been found

in shallow, subtidal areas.

The cleaning of surface areas

("brushing the flats") has increased

recruitment. Also, the placement of

pilings, stakes, or poles is a common

commercial method of collecting seed

mussels. In the Santa Barbara

Channel, natural sets of M.

californianus are collected from tEe

legs of oil drilling platforms.

Setting areas are prepared by cleaning

unwanted growth or wrapping areas with

special materials that attract wild

spat.

It probably takes many years for

Mytilus to become established in the

high intertidal zone at approximately

+1.8 to +2.4 m above mean lower low

4
A

93x65

0

110x82 125x98

D

139x116

152x129 170x149 190x166

232x210

3

260x247

215x201

MYTILUS EDULIS

x 112

K

296x282

Figure 3. Larval development of the bay mussel, size (height and length) in

micrometers.

5
water (Dayton 1971). Establishment is

faster at lower levels (Dayton 1971).

Maturity

Sex ratios are generally equal

and there is no indication of sex

change with age. Some sexually mature

mussels were only 4 months old or 25

mm long. Viable sperm was observed in

mussels 30 mm long. Spawning occurred

near the end of the first year or when

the mussels were 70 mm 1

Fox 1942).

ong (Coe and

Age and Growth

The age of mollusks

by three methods: (1) !5’

is determ ined

ize-frequency

studies; (2) the interpretation of

growth interruption lines on the

shell; and (3) experimental methods

involving the release and recovery of

marked individuals (Haskin 1954).

Jamieson et al. (1975) reported that

growth rates of mussels in any given

population were so variable that year

classes could not be determined from

size. Most workers have attempted to

age mussels through interpretation of

growth interruption lines, although

some have studied marked individuals.

Lutz (1976) aged mussels by using

acetate on polished longitudinal shell

sections.

Factors influencing growth of M.

edulis were divided into two

categories by Jamieson et al. (19751:

biological (age, size, and genotype),

and physical (light, temperature,

depth, food, salinity, and current).

Of these, water temperature was the

only factor which influenced growth

throughout the mussel's geographic

range. In some areas (e.g., Maine),

growth was seasonal, whereas in

California, where the annual

temperature range was relatively

narrow, there was no obvious seasonal

variation in shell growth rate

(Chalfant et al. 19801. Lutz and

Porter (1977) reported that water

temperature above 25 'C not only

seriously decreased growth, but also

caused mortalities of 89%-100%.

In extensive growth studies

conducted in Puget Sound, Washington,

by Skidmore and Chew (19851, sets of

y. edulis in four of five experiments

attainedmarket size (50 mm) within 12

to 13 months. The growth rates of M.

edulis and M. californianus were also

compared at-two sites in Puget Sound.

Mytilus edulis grew the fastest for

the first three months, but size

differences between the two species

were small by the end of 9 months.

In southern California (Scripps

Institution of Oceanography dock, San

Diego) M. californianus sometimes

grows as much as 7 mm per month. This

species may reach a length of 80-86 mm

within a year of settlement, 120 mm

after 2 years, and 140-150 mm after 3

years (Coe and Fox 1942). Maximum

size is 200-250 mm (Harger 1972).

Growth is fastest during the colder

months and slowest (sometimes nil) in

mid-summer or above 20 'C.

Mytilus edulis does not grow as

large as y. californianus (Figure 41.

In southern California, the bay mussel

grew to a length of 66 to 76 mm after

1 year and 90-99 mm after 2 years (Coe

1945). Thereafter, growth was very

slow (Table 1). Maximum size ranges

from 120-150 mm (Harger 1972).

Mussels eat a variety of

organisms, such as dinoflagellates,

organic particles, small diatoms,

zoospores, minute ova and spermatozoa,

flagellates and other protozoans,

various unicellular algae, and

detritus (consisting of particles from

the cytolysis of cells of a large

variety of plants and animals).

Growth rates are related to the

abundance of dinoflaaellates (Coe and

Fox 1942). Mytilus californianus from

southern California arew 100% faster

in height and 50% faster in width at

+O.l m (the plus sign in this report

indicates vertical height above mean

6
2 3 4 5 6 7 8

Prcwcted Time (yews)

Figure 4. Projected growth curves for

Mytilus edulis . (open symbols) and

F;"ilE;;us califor;;ta;us (closed symbols)

on obtained from

undisturbed populations of mussels at

Santa Barbara Harbor, California

(Harger 1970b).

lower low water) than at +0.3 m where

feeding time was shorter (Dehnel

1956). Males grow faster than females

the first 1.5 years (Coe and Fox

1942).

Food particles, drawn through an

inhalent aperture by ciliary action,

are caught on sheets of mucus and

carried along the sides of palps to

the mouth. Some particles are

ingested but others, if excessive, are

discharged from the mantle cavity as

pseudofeces. The most common food is

the dinoflagellate Prorocentrum

micans, at a size of 57 x 30 urn (Fox

and Coe 1943).

Table 1. Growth of M tilus edulis in

relation to size (Coe+----- 945).

Size (mm)

Average increase

per month (mm)

11-20 11.3

21-30 11.1

31-40 9.9

41-50 8.0

51-60 5.9

61-90

91-103 E5

COMMERCIAL AND SPORT FISHERIES AND

AQUACULTURE

Both species of mussels were once

commercially important in California.

Over 69,000 pounds were landed in

1917 (Table 2), but in 1927, and

thereafter, most areas were closed to

fishing by the California State Board

of Health, due to mussel poisoning.

No mussels can now be sold for human

consumption from May 1 to October 31

because of the presence of paralytic

shellfish poisoning. The consumption

of mussels that have concentrated

large amounts of the poison-producing

microscopic dinoflagellate Gonyaulax

catenella sometimes causes serious

illness (Nishitani and Chew 1983). In

1980, for example, poisoning was

recorded in 98 residents of Marin and

Sonoma counties, California, of whom

two died (Estes and VanBlaricom 1985).

A limited sport fishery, where

mussels are usually removed from

piling or rocks by hand, now exists

during the open season. A daily

harvest of 25 pounds is allowed.

Four companies have shown

interest in farming mussels for human

consumption in Tomales Bay, California, because the demand for a yearround supply of quality mussels has

outgrown the supply from native beds.

They hang ropes from longlines

supported by floats to collect a

natural set. The seed is then placed

in plastic netting, which is then hung

from the longlines.

One company cultures mussels from

the legs of oil drilling platforms in

the Santa Barbara channels. Seed,

placed in plastic netting, is wrapped

around the legs. When the mussels

reach maturity divers scrape them off

the legs. The mussels are conveyed to

the surface throuah suction hoses and

are cleaned, packaged,

fresh to market.

and shipped

The ratio of meat to total weight

is high in mussels. The composition

7
Table 2. Yearly landings of mussels crude fat, 2.6%-3.5%; ash, 2.0%-2.7%;

in California. and carbohydrate, 1.2%-5.8%.

Year

1916'

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929

1930

1931

1932

1933

1935

1936

1937

1938

1939

1940

1942

1946b

1947

1974d 1972c

1975e

1976f

Landings

(lb)

53,799

69,042

49,154

35,095

33,112

9,196

43,872

60,026

49,223

25,942

14,614

29,631

1,610

1,028

325

1,800

230

465

10

750

1,490

150

1,800

100

50

639

530

111,7999

81,642g

53,691g

47,336h

ECOLOGICAL ROLE

Feeding

Mussels are suspension feeders,

are considered to be scavengers, and

collect anything in the plankton that

is small enough to ingest. Digestion

is intracellular (Coe and Fox 1944).

Competitors

aYears 1916-1947 (Bureau of Marine

bFisheries 1949).

No commercial landings between 1948-

1971.

When a resource is potentially

limiting (as in the case of living

space for sessile organisms in the

rocky intertidal zone) one species of

competitor may potentially dominate

the others in procuring or holding the

resource. Predation or physical

disturbance may cause mortality of the

dominant competitor sufficient to

prevent the exclusion of the other

competitors, allowing several species

to coexist. Such phenomena occur in

the rocky intertidal zone of the

Pacific coast of the United States,

where significant insights into such

processes of community function have

been obtained especially from studies

done on the coast of Washington. As

shown in the following discussion, the

distribution of M. californianus is

controlled by praation and physical

disturbance, while the distribution of

fl. edulis is controlled by these two

factors and competition as well.

'Pinkas 1974

dMcAllister i976.

FPinkas 1977.

Oliphant 1979.

ZBait.

2,357 pounds for human consumption;

rest for bait.

On Washington's exposed outer

coast, M. californianus is the

dominant -competitor for available

space and will form dense monospecific

stands unless deterred (Paine 1966).

Mytilus californianus is one of the

most consistent occupants of space in

the intertidal barnacle-mussel

association there, along with the

barnacles Chthamalus dalli, Balanus

alandula. and B. cariosa. and the sea

of cultured M. edulis, analyzed by

Slabyj et al_ (1978), is moisture,

71.1%-75.7%; protein, 14.1%-21.0%;

dJ

anemone ’ *elegantissima

(Dayton 1971). The name "California

sea mussel" was given to y.

8
californianus because of its

restriction mostly to the outer coast.

Mytilus californianus will settle

among Balanus and completely cover the

barnacles (Dayton 19711, eventually

excluding them (Paine 1966). Mytilus

californianus denies space to M.

edulis on the open coast, but it seeFirs

to offer protection from wave action

to those M. edulis that do become

attached (Tiarger970c). Mytilus

edulis is called the "bay mussel"

because it has long been thought to be

common mostly in quiet waters, but it

is now known to be common on the outer

coast as well (Suchanek 1978).

Mytilus edulis on the exposed outer

coast of Washington usually occupies a

band 0.3 m in vertical height (at

about t2.9 to t3.2 m) above the M.

californianus zone, which is at aboiit

to.5 to t2.9 m (Suchanek 1978). The

lower limit of M. edulis zone is

probably set by competitive exclusion

by M. californianus and by predation

(Suchanek 1978).

Predators

A number of predators prey on

mussels in California. Harger (1972a)

reported that M. edulis was preferred

over M. CaTifornianus by nine

invertebrate predators: two sea stars,

Pisaster giganteus and P. ochraceusi

five species of muricid qastropods,

Thais emarginata,

Ocenebra

Acanthina spiratai

poulsoni, Ceratostoma

nuttalli, and Jaton festivus, and two

species of crabs, Cancer antennarius

and Pachygrapus crassipes. A third

crab, Pugettia producta, ate mussels

but showed no oreference for a

particular species. Harger and

Landenberger (1971) observed greater

losses from predation in shallow water

compared to deep water.

Mytilus californianus occupies

only about 4% of the space (between

about +3 m and a depth of about -27 m)

that it would occupy under physically

mild and predator-free conditions

(Paine 1976b). The sea star P.

ochraceus may clear patches of FI. -

californianus (Dayton 19711, one of

its preferred prey (Paine 1966). In

an experiment in Washington, p.

ochraceus was removed and the area

eventually became a monosoecific stand

of M. Ealifornianus (Paine 1966).

PisaFter ochraceus controls the

abundance of the dominant mussel and

thus allows other species to coexist

(Paine 1966). Mytilus californianus

escapes predation from whelk predators

(Thais Vspp.) by attaining a variable

minimum size of invulnerability

(Dayton 1971). This mussel escapes

predation by P. ochraceus by growing

to a minimum>ize that increases as

the size of the sea star increases

(Paine 1976b). Mean density of P.

ochraceus may vary locally by-at leayt

two orders of maanitude. affectina

local abundance of- M. californianur

(Paine 1976b). In Washington, areas

of low M. californianus abundance and

high P.ochraceus density occur sideby-si&e with dense stands of large M.

californianus that have low B.

ochraceus density; the mussels hzd

probably escaped predation by

attaining an invulnerable size (Paine

1976b).

Pisaster ochraceus may indirectly

enhance recruitment of M.

californianus by the following series

of events: 1) P. ochraceus consumes

limpets (less preferred prey) and may

reduce their abundance; 21 as shown

experimentally, a reduction in limpet

density would consequently enhance the

abundance of one of the limpet's major

foods, the red alga Endocladia; and

3) mussel recruitment mav be enhanced

because Endocladia is- the major

settling substrate for M.

californianus larvae (Dayton 1971). -

On the outer coast of Washington,

y. edulis will become established in a

patch cleared by physical disturbance

or predation in the M. californianus

zone (which is at -about to.5 to

t2.9 m) only if the patch diameter is

greater than about 40 cm (Suchanek

1978). Smaller patches

settling y.

expose

edulis (and the

9
filamentous algae used as settling

substrate) to removal by grazers

(limpets, chitons, and the

opisthobranch gastropod Onchidella

borealis) that move in from the edge

of the patch (Suchanek 1978). Those

M. edulis that do invade the M.

californianus zone grow quickly bet

are preferred over M. californianus by

whelk predators, Th>is spp. (Suchanek

1978). On the outer coast, the lower

limit of M. edulis band (about t2.9 m)

is probably determined partly by

predation by gastropods, birds, and

sea stars (Suchanek 1978). Pisaster

ochraceus has more time to feed and

thus can eat more mussels at lower

intertidal levels. The abrupt lower

limit of M. californianus band (about

to.5 m) i? almost certainly the most

conspicuous feature of the rocky

intertidal community (Paine 1976) and

is probably set by predation by p.

ochraceus (Paine 1966, 1974).

The sea otter (Enhydra lutris) is

known to eat both 5. califorz and

VanBlaricom

!985,edut!l: m,',',",:"," foa,nmd only a small

porti& of its diet in California.

Consumption of mussels by sea otters

appears to be sufficiently scattered

in time and space to preclude the

regional depletion of harvestable

stocks. The exposure of much of the

central California coast to heavy surf

probably provides an important refuge

for mussels from foraging sea otters.

Predation by the black oystercatcher,

Haematopus bachmani, and dislodgement

by storm waves are probably at least

as important as sea otter predation in

limiting the availability of mussels

for human consumption in California.

Diving ducks, especially scoters,

are mussel predators. Three species

of ducks are responsible for most of

the losses--the surf scoter, Melanitta

delgandi, white-winged scoter, M.

perspicillata, and black scoter,

Oidemia amereicana. In feeding, the

ducks dive underwater, remove a clump

of mussels, return to the surface,

shake the clump, and dislodge one

mussel and swallow it whole. The

other mussels in the clump sink to the

bottom (Skidmore and Chew 1985).

Commensals, Parasites, and Encrustinq

Epifauna

The commensal crab, Pinnotheres

sp., has been found in M. edulis. The

crabs eat the food -mussels have

filtered out and decrease the pumping

rates of mussels. Mature female crabs

can reduce the meat yield by as much

as 26% (Pregenzer 1981).

In California the parasitic

copepod Mytilicola orientales was

found in 13 of 20 M. californianus and

in 24 M. edulis TChew et al. T964)

Bradley- andSiebert (1978) found

M tilicola in M. edulis from San

+--- rancisco Bay (incidence- range, 36.8%-

48.5%); they believed the parasite was

imported with the Japanese oyster

(Crassostrea gigas). The gonads of

one fi. californianus, from Humboldt

;;;r;lat;;;e ,",e,;;~~y,, parasitized with

of the family

Bucephalidae (Edwards 19841, and

trematode sporocysts were found in the

digestive gland and gonadal tissue of

E. edulis (Brousseau 1983).

Subtidal y. californianus may be

overgrown by sponges, barnacles,

anemones, and other epifauna

1976a). Heavily encrusted rnL!iACE

weighed less (in tissue weight) than

those less encrusted (Paine 1976a).

ENVIRONMENTAL REQUIREMENTS

Temperature and Salinity

Temperature plays an important

role in growth. Coe and Fox (1944)

found that the growth of M.

galifornianus was most rapid at 17-20

C and decreased sharply above 20 'C.

Growth hontinued (but at a lower rate)

at 14 C or lower but less rapidly.

Feeding continued at 7-8 OC and

27-28 OC. Filtration rate and oxygen

10
consumption were highest at 20 'C (Coe edulis needs to be submerged at least

and Fox 1942). half the time to show significant

growth.

In California the optimum temperature range for growth was lo-20 OC

(Morris et al. 1980). Feldmeth and

Alpert (1977) found that the mean wet

weight of mussels from the cooler

waters of Alamitos Bay, California

(14.8-15.8 'C) was four times greater

than those from San Gabriel River

(22.7-25.0 '0.

Physical Disturbance

Wave action or wave-borne logs in

exposed areas may remove whole mats of

mussels in the intertidal zone (Dayton

1971). At the edge of a cleared

patch, substantial numbers of

additional mussels may be removed by

wave action (Dayton 1971). Mussels

high in the intertidal zone away from

starfish predation may survive for a

great many years, until some are

killed by wave-borne logs, unusual

cold, or other physical stresses

(Dayton 1971). The upper limit to the

E. edulis zone in the high intertidal

area at Tatoosh Island, Washington,

was controlled by extreme summer heat

that killed mussels, or made their

shells gape and made them easy prey

for gulls (Suchanek 1978).

In nature, M. californianus is

rarely found in rays and estuaries--

perhaps because eggs, sperm, and

larvae cannot withstand dilutions

below 75% sea water (Robertson 1964).

In contrast, M. edulis can accommodate

a wide saliniFy range (Bayne 1965)--an

interspecies difference that explains

its wider distribution both in the

open coastal waters and in protective

bays.

Habitat

edulis Mytilus is sensitive to

the effects of waves (Harger 1970a).

It appears that y. californianus holds

its position more strongly than does

B. edulis.

Mytilus edulis is behaviorally

adapted to quietwaters better than M.

californianus. Mussels may form

clumos UD to 25 cm thick: iuvenile M.

edulis crawl to the outside of su'?h

ClUrnDS which mav include M.

californianus, but the latter mussel

does not (Harger 1968). This crawling

behavior protects M. edulis from

harmful silt that ac?umulates inside

the clumps in quiet waters. This silt

may tend to exclude M. californianus

there (Harger 1968). -

The growth of M. edulis was

seriously affected by tidal exposure.

Little or no growth took place at 80%

exposure and the mussels died within 3

months; growth was significantly less

at 40% and 60% exposure than at 0% and

20% exposure (Christensen 1984).

Morris et al. (1980) stated that M.-

1

Other Environmental Factors

Because mussels--particularly M.

edulis--are distributed along tTie

coast, and in bays and estuaries, they

are often subjected to sewage and

other kinds of pollution (Roberts

1976). The mussels may be unsafe to

eat and must be depurated before

marketing. In addition, both species

of mussels ingest certain dinoflagellates that make them toxic to

humans, causing paralytic shellfish

poisoning.

Mussels concentrate hydrocarbons

in their tissues. The hydrocarbons

are rapidly taken up by the gill

tissues and eventually are deposited

in high concentrations in the

alimentary canal (Roberts 1976).

Although oil is only slightly toxic to

mussels, it may affect the marketing

of the animals by tainting them.

Clark and Finley (1975) reported that

the uptake and loss of petroleum

hydrocarbons was related to the
magnitude of exposure. When mussels

were placed in clean water, most

hydrocarbons were lost but significant

quantities of No. 2 fuel oil remained

for as long as 35 days. Fuel oil and

outboard motor oil may inhibit byssal

thread formation but at Long Beach

Harbor, California, motor boat

activity posed little threat (Carr and

Reish 1978).

A number of trace metals are

found in the soft tissues of mussels,

including Ag, Cu, Cr, Mn, Pb, Cd, and

Zn. Levels in M. edulis from

California (Table 3) xgreem those

of the same species in New Zealand

(Graham 1972).

Since 1977 the California

Department of Fish and Game has been

monitoring the amount of trace metals

in mussels (State Mussel Watch) along

the coast (Stephenson et al. 1980a,

1980b). Of the sites investigated,

Royal Palms, Corona de1 Mar, and La

Jolla were "hot spots" for silver,

copper, lead, and zinc. Silver was

especially high in mussels in South

San Francisco Bay. Los Angeles Harbor

and Santa Catalina Island had the

highest concentration of silver and

lead while mussels in San Diego had

the highest concentration of zinc.

The amount of trace metals in mussels,

depending on site, were in many

instances much higher than those found

by Graham (1972).

Table 3. Dry weight (ppm) of trace metals in soft parts of whole bodies of

Mytilus edulis. Values are approximate means (ranges in parentheses) (Graham

1972).

Location N Ag cu Cr Mn Pb Cd Zn

California 24

(<I-11.3) (5-7111 (<24_8) (6?8) (2:8)

5 284

(3-7) (204-341)

New

Zealand 6

(O.Ik3) (8-'II) (9$4) (122-738) (3$5) (509:80)

12
LITERATURE

Bayne, B.L. 1965. Growth and delay

metamorohosis of the larvae of

Mytilus' edulis (L). Ophelia 2(1):1-

47.

Bradley, W., and A.E. Siebert, Jr.

1978. Infection of Ostrea lurida

and Mytilus edulis bytheparasite

copepod Mytilicolaorientalis in San

Francisco Bay, California. Veliger

21(l): 131-134.

Breese, W.P., R.E. Millemann, and R.E.

Dimick. 1963. Stimulation of

spawning in the mussel Mytilus

edulis Linnaeus and Mytilus

californianus. Biol. Bull. (Woods

Hole) 125(2):197-205.

Brousseau, D.J. 1983. Aspects of

reproduction of the blue mussel,

Mytilus edulis (Pelecypoda:

Mytilidae) iig Island Sound.

U.S. Natl. Mar. Fish Serv. Bull.

81(41:733-739.

California Bureau of Marine Fisheries.

1949. The commercial fi'sh catch of

California for the year 1947 with an

historical review 1916-1947. Calif.

Dep. Fish Game Fish. Bull. 74. 267

PP.

Carr, R.S., and D.J. Reish. 1978.

Studies on the Mytilus edulis

community in Alamitos Bay, California: VII. The influence of watersoluble petroleum hydrocarbons on

byssal thread formation. Veliger

21(2):283-287.

Chalfant, J-S., Jr., T. Archambault,

and A.E. West, J.G. Riley, and N.

Smith. 1980. Natural stocks of

mussels: growth, recruitment and

harvest potential. Pages 36-68 inITED

R.A. Lutz, ed. Mussel culture and

harvest: A North American

perspective. Elsevier Scientific

Publishing Company, Amsterdam.

Chew, K.K., A.K. Sparks, and S.C.

Katkanskv. 1964. First record of

Mytilicoia orientalis Mori in the

California mussel Mytilus edulis

Conrad. J. Fish. Res. Board Can.

21(1):205-207.

Christensen, F.W. 1984. Intertidal

growth response of Mytilus edulis

(Linnaeus) in Humboldt Bay, California. M.S. Thesis. Humboldt

State University, Arcata. 35 pp.

Clark, R.C. Jr., and J.S. Finley.

1975. Uptake and loss of petroleum

hydrocarbons by mussels, Mytilus

edulis, in laboratory experiments.

U.S. Natl. Mar. Fish. Serv. Fish

Bull. 73(3):508-515.

Coe, W.R. 1945. Nutrition and growth

of the California bay-mussel

(Mytilus edulis diegensis) J. Exp.

Zool. 99(1):1-14.

Coe, W.R., and D.L. Fox. 1942.

Biology of the California sea-mussel

(Mytilus californianus). I.

Influence of temperature, food

supply, sex and age in the rate of

growth. J. Exp. Zool. 90(11:1-30.

Coe, W.R., and D.L. Fox. 1944.

Bioloav of the California sea-mussel

(MytiTus californianus). III.

Environmental conditions and rate of

growth. Biol. Bull. (Woods Hole)

87(1):59-72.

Dayton, P.K. 1971. Competition,

disturbance, and community organ1 3
ization: the provision and subsequent utilization of space in a

rocky intertidal community. Ecol.

Monogr. 41(4):351-389.

Dehnel, P.A. 1956. Growth rates in

latitudinally and vertically

separated populations of Mytilus

californianus. Biol. Bull. 110:43-

53.

Edwards, R.L. 1984. The reproductive

and percentage solids cycles of

Mytilus edulis and

californianus

Mytilus

Humboldt County,

California. M.S. Thesis. Humboldt

State University, Arcata. 57 pp.

Estes, J.A., and G.R. VanBlaricom.

1985. Sea-otters and shellfisheries. Pages 187-235 in J.R.

Beddington, R.J.H. Bevertox and

D.M. Lavigne, eds. Marine Mammals

and Fisheries. George Allen and

Unwin, London.

Feldmeth, C.R., and M. Alpert. 1977.

The effect of temperature on the

distribution and biomass of Mytilus

edulis in the Alamitos Bay area.

Veliger 20(1):39-42.

Fitch, J.E. 1953. Common marine

bivalves of California. Calif. Dep.

Fish Game Fish. Bull. 90. 102 pp.

Fox, D.L., and W.R. Coe. 1943.

Biology of the California sea-mussel

(Mytilus californianus) II.

Nutrition, metabolism, growth and

calcium deposition. J. Exp. Zool.,

93:205-249.

Graham, D.L. 1972. Trace metal

levels in intertidal mollusks of

California. Veliger 14(4):365-372.

Harger, J.R.E. 1968. The role of

behavioral traits in influencing the

distribution of two species of sea

mussel, edulis Mytilus and M.

californianus. Veli$$-ii11(1):45-49.

Harger, J.R.E. 1970a. The effect of

wave impact on some aspects of the

biology of sea mussels. Veliger

12(4):401-414.

Harger, J.R.E. 1970b. Comparison

amonq qrowth characteristics of two

species of sea mussels, .Mytilus

edulis and Mytilus californianus.

Veliger 13(1):44-56.

Harger, J.R.E. 197Oc. The effect of

species composition on the survival

of mixed oooulations of the sea

mussels, Mytilus californianus and

Mvtilus edulis. Velioer 13(2):147-

1152.

Harger, J.R.E. 1972. Competitive

coexistence: maintenance of

interacting associations of the sea

mussels Mytilus edulis and Mytilus

californianus. Veliger 14(4):387-

410.

Harger, J.R.E., and D.E. Landenberger.

1971. The effect of storms as a

density dependent mortality factor

populations

Voiliger 14(2):195-%I.

sea mussels.

Haskin, H.H. 1954. Age determination

in mollusks. Trans. N.Y. Acad. Sci.

16:300-304.

Jamieson, G.S., I.C. Neish, and C.S.L.

Clark. 1975. Perspective and development prospects of mussel cultivation in the Maritime Provinces of

Canada. Mar. Ecol. Lab. Nova

Scotia. Ref. AMRL74-11. 75 pp.

Loosanoff, V.L., and H.C. Davis.

1963. Rearing of bivalve mollusks.

Advances in Marine Biology l:l-136.

Lutz, R.A. 1976. Annual growth

patterns in the inner shell layer of

Mytilus edulis L. J. Mar. -Biol.

Ass. U.K.56:723-731.

Lutz, R.A., and B. Porter. 1977.

Experimental culture of blue mussels

edulis Mytilus in heated effluent

waters of a nuclear power plant.

Proc. World Maricult. Sot. 8:427-

445.

14

California mussel watch 1979-1980.

Trace metal concentrations in the

California mussel, Mytilus

californianus, and bay mussel, M.

edulis, along the California coa?t

and selected harbors and bays. Part

I . California Water Quality

Monitoring Rep. 80-8. 95 pp.

Suchanek, T.J. 1978. The ecology of

Mytilus edulis L. in exposed rocky

intertidal communities. J. Exp.

Mar. Biol. Ecol. 31:105-120.

Suchanek, T.H. 1981. The role of

disturbance in the evolution of life

history strategies in the intertidal

mussels Mvtilus edulis and Mvtilus II

californianus. Oecologia (B&l.).

50:143-152.

Trevelyan, G.A., and E.S. Chang.

1983. Experiments on larval rearing

of the California mussel (Mytilus

californianus). J. World Maricult.

Sot. 14:137-148.

16
REPORT DOCUMENTATION 1. “(mRT Ho. 2. 2 nulPl*na’a Lc;.r,.on NO

PACE Biological i&port 87(1&841

*

L li(la .,., ,btltl~

Species Profiles: Life Histories and Environmental

% nwr( o*t*

Requirements of Coastal Fishes and Invertebrates

September 1988

(Pacific Southwest)--California sea mussel and bay mussel

L

7. Autholi~l

aWilliam N. Shaw, b

Thomas J. Hassler, and 'David P. Moran

L hdonnin~ Orgamzation R*m. ?a0

9. ?*lfomlin~ O~.rlr~llon l4.m. .n* Add,.,.

aHumboldt State University bU.S. Fish & Wildl. Ser. 'U.S. Fish and Wildlife Service

Department of Fisheries Calif. Coop. Fishery Unit National Wetlands Research Center

Fred Telonicher Marine Lab. Humboldt State University 1010 Gause Boulevard

Trinidad, CA 95570 Arcata, CA 95521 Slidell, LA 70458

12 fgonsorin~ O~snlr~tlom “.m. and Addrass I

U.S. Department of the Interior U.S. Army Corps of Engineers 1%. TY,,. 01 R*‘,.X, ‘,.,,od CX,.w.d

Fish and Wildlife Service Waterways Experiment Station

Research and Development P.O. Box 631

National Wetlands Research Center Vicksburg, MS 39180 14.

Washington, DC 20240

*U.S. Army Corps of Engineers Report No. TR EL-82-4

Species profiles are literature summaries of the taxonomy, morphology, distribution, life

history, and environmental requirements of coastal aquatic species. They are prepared

to assist in environmental impact assessment.

californianus, and the bay mussel,

The California sea mussel, Mytilus

M_. edulis, are commonly collected for bait. Some

commercial landing and aquaculture occurs at a very low level of production. Both

species are distributed along the California coast; the sea mussel is more comnonly

found on intertidal coastal rocks and the bay mussel on pilings and other hard substrates

in bays and estuaries. The eggs of both soecies develop into a trochophore stage in

12-24 hours after fertilization, and the planktonic larval stage lasts 3-4 weeks. Sexual

maturity can occur in one year. Spawning of the sea mussel occurs sporadically throughout the year; the bay mussel spawns in central California in late fall and winter.

Maximum length is 120-150 mm for the bay mussel and 200-250 mm for the sea mussel. Both

species are regarded as unsafe to eat from May 1 to October 31 due to the possible

presence of paralytic shellfish poisoning.

Life cycles Feeding habits Estuaries

Fisheries Growth Salinity

Mussels Competition Temperature

Aquaculture Water pollution .Contaminants

b. Idwatlfirn/O,a.n.End~d T.rms

Bay mussel Ecological role

Mytilus edulis

California mussel

Commercial fishery

Sport fishery

Mytilus ~californianus Ecological requirements

c COSATI field/Gmu~

1.. Av~ll~blli~ Slatam~nt

Unlimited release

1,. sec”tity Clas* (Thh Rww-t) 21. No. 01 PasUnclassified 16 - -

zo. kuri~ Class Vhlr Par*) a l Iic*

Unclassified

ta* ANfl-239.11~ OrTlONAL fORU 272 (4-71

(fo,,,..rly NTISlS)

oe~.Qem.“, 01 commwc*
As the Nation’s principal conservation agency, the Department of

the Interior has responsibility for most of our nationally owned

public lands and natural resources. This includes fostering the

wisest use of our land and water resources, protecting our fish

and wildlife, preserving the environmental and cultural values of our

national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses

our energy and mineral resources and works to assure that their

development is in the best interests of all our people. The Department also has a major responsibility for American Indian reservation

communities and for people who live in island territories under U.S.

administration.

U.S. DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

TAKE PRIDE

in America

UNITED STATES

DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

National Wetlands Research Center

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