(DRAFT) - Taxonomy
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
TAXONOMY
NAME - mussel, California sea
OTHER COMMON NAMES - California sea mussel, rock mussel, big mussel, California mussel and sea mussel
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - ,
CLASS AND SUBCLASS - Bivalvia - clams or bivalves,
ORDER AND SUBORDER - Mytiloida,
FAMILY AND SUBFAMILY - Mytilidae,
GENUS AND SUBGENUS - Mytilus,
SPECIES AND SSP - californianus,
SCIENTIFIC NAME - Mytilus californianus
AUTHORITY - Conrad, 1837
TAXONOMY REFERENCES - 9 and 186
COMMENTS ON TAXONOMY -
The name "California sea mussel" was given to M. californianus because of
its restriction mostly to the outer coast *9*.
Taxonomy - 1 (DRAFT) - Status
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Commercial/consumption
Commercial/bait
See Comments
REFERENCES FOR STATUS - 9
COMMENTS ON STATUS -
The California sea mussel, along with the bay mussel, supports a small
commercial bait fishery and is cultured for food on a small scale in
Tomales Bay and just north of San Diego *9*.
SPORT FISHERY
A limited sport fishery, where mussels are usually removed from pilings or
rocks by hand, now exists during the open season. A daily harvest of 25
pounds is allowed *9*.
Status - 1 (DRAFT) - Distribution
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
REFERENCES FOR HABITAT - 9
LAND USE -
Water
Bays and Estuaries
REFERENCES FOR LAND USE - 9
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine
Marine, intertidal
Estuarine
Estuarine, intertidal
Marine OW0
REFERENCES FOR NWI - 9
COMMENTS ON HABITAT ASSOCIATIONS -
The California sea and bay mussels are relatively common along the rocky
coastline and in bays and estuaries. The name "California sea mussel" was
given to M. californianus because of its restriction mostly to the outer
coast *9*.
The eggs are fertilized in the open water. Larvae feed on phytoplankton and
are at the mercy of currents. (They may be carried away from setting areas
and die). M. californianus sets on barnacles, old mussel shell, and newly
exposed hard surfaces. Density of newly settled M. californianus has been
found to be highest on filamentous algae. They prefer to set on byssal
threads from adults. It probably takes many years for Mytilus to become
established in the high intertidal zone at approxiamtely +1.8 to +2.4 m
above mean lower low water. Establishment is faster at lower levels.
Mytilus californianus from southern California grew 100% faster in height
and 50% faster in width at +0.1 m (the plus sign indicates vertical height
above mean lower low water) than at +0.3 m where feeding time was shorter
*9*.
On Washington's exposed outer coast, M. californianus is the dominant
competitor for available space and will form dense monospecific stands
unless deterred. Mytilus californianus is one of the most consistent
occupants of space in the intertidal barnacle-mussel association there.
Habitat Associations - 1 (DRAFT) - Food Habits
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
SCAVENGER
REFERENCES FOR TROPHIC LEVEL - 9
LIFESTAGE FOOD FOOD PART
General Microorganisms Not Applicable
General Protozoans Not Applicable
General Bacillariophyceae Not Applicable
General Detritus - Organic Not Applicable
General See Comments; Food Not Applicable
Larva Phytoplankton Not Applicable
REFERENCES FOR GENERAL FOOD - 9
REFERENCES FOR LARVAE FOOD - 9
COMMENTS ON FOOD -
Mussels are suspension feeders, are considered to be scavengers, and collect
anything in the plankton that is small enough to ingest. Digestion is
intracellular *9*.
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 dinoflagellates.
Mytilus californianus from southern California grew 100% faster in height
and 50% faster in width at +0.1 m (the plus sign here indicates vertical
height above mean lower low water) than at +0.3 m where feeding time was
shorter. Males grow faster than females the first 1.5 years *9*.
FEEDING HABITS
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 micrometers *9*.
COMMENTS ON LARVAE FOOD -
Larvae feed on phytoplankton *9*.
Food Habits - 1 (DRAFT) - Environment Associations
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Water Temperature: Greater than 27 degrees C
G Water Temperature: Between 21-27 degrees C
G Water Temperature: Between 15-21 degrees C
G Water Temperature: Below 15 degrees C
G Water Temperature: Specified in Comments
G Substrate: Specified in Comments
G Relation to Substrate: Attached - normally sessile
G Relation to Substrate: Specified in Comments
G Water Level: Specified in Comments
G Human Association: Specified in Comments
LIM Currents: specified in comments
LIM Water Level: Specified in Comments
LIM
J Relation to Substrate: Attached - normally sessile
J Relation to Substrate: Specified in Comments
L Currents: specified in comments
L
E
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 9
REFERENCES FOR LIMITING ENVIRONMENTAL ASSOC_ - 9
REFERENCES FOR JUVENILE ENVIRONMENTAL ASSOC_ - 9
REFERENCES FOR LARVAE ENVIRONMENTAL ASSOC_ - 9
REFERENCES FOR EGG ENVIRONMENTAL ASSOC_ - 9
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
HUMAN ASSOCIATIONS
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 *9*.
TEMPERATURE
Temperature plays an important role in growth. In one study the growth of
M. californianus was most rapid at 17-20 degrees C and decreased sharply
above 20 degrees C. Growth continued (but at a lower rate) at 14 degrees C
or lower but less rapidly. Feeding continued at 7-8 degrees C and 27-28
Environment Associations - 1 (DRAFT) - Environment Associations
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
degrees C. Filtration rate and oxygen consumption were highest at 20
degrees C *9*.
In southern California growth is fastest during the colder months and
slowest (sometimes nil) in mid-summer or above 20 degrees C *9*.
TIDAL INFLUENCE
Mytilus californianus from southern California grew 100% faster in height
and 50% faster in width at +0.1 m (the plus sign here indicates vertical
height above mean lower low water) than at +0.3 m where feeding time was
shorter *9*.
SALINITY
In nature, M. californianus is rarely found in bays and estuaries, perhaps
because eggs, sperm, and larvae cannot withstand dilutions below 75% sea
water *9*.
COMMENTS ON LIMITING ENVIRONMENTAL ASSOC_ -
CURRENTS
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 *9*.
TIDAL INFLUENCE
Mytilus californianus from southern California grew 100% faster in height
and 50% faster in width at +0.1 m (the plus sign here indicates vertical
height above mean lower low water) than at +0.3 m where feeding time was
shorter *9*.
SALINITY
In nature, M. californianus is rarely found in bays and estuaries, perhaps
because eggs, sperm, and larvae cannot withstand dilutions below 75% sea
water *9*.
WAVE ACTION
While Mytilus edulis is sensitive to the effects of waves, M. californianus
holds its position more strongly. Mytilus edulis is behaviorally adapted
to quiet waters better than M. californianus. Mussels may form clumps up
to 25 cm thick. Juvenile M. edulis crawl to the outside of such clumps,
which may include M. californianus, but the latter mussel does not. This
crawling behavior protects M. edulis from harmful silt that accumulates
inside the clumps in quiet waters. This silt may tend to exclude M.
californianus there *9*.
Wave action or wave-borne logs in exposed areas may remove whole mats of
mussels in the intertidal zone. At the edge of a cleared patch,
substantial numbers of additional mussels may be removed by wave action.
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 *9*.
Environment Associations - 2 (DRAFT) - Environment Associations
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
COMMENTS ON JUVENILE ENVIRONMENTAL ASSOC_ -
Mytilus californianus sets on barnacles, old mussel shell, and newly
exposed hard surfaces *9*.
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 the legs of oil
drilling platforms. Setting areas are prepared by cleaning unwanted growth
or wrapping areas with special materials that attract wild spat *9*.
COMMENTS ON LARVAE ENVIRONMENTAL ASSOC_ -
SALINITY
In nature, M. californianus is rarely found in bays and estuaries, perhaps
because eggs, sperm, and larvae cannot withstand dilutions below 75% sea
water *9*.
CURRENTS
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 *9*.
COMMENTS ON EGG ENVIRONMENTAL ASSOC_ -
SALINITY
In nature, M. californianus is rarely found in bays and estuaries, perhaps
because eggs, sperm, and larvae cannot withstand dilutions below 75% sea
water *9*.
Environment Associations - 3 (DRAFT) - Life History
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
LIFE HISTORY
MORPHOLOGY/IDENTIFICATION AIDS
The umbo is at extreme anterior end of the shell. Shell is 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 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 *9*.
SPAWNING
The California sea mussel continually spawns throughout the year at a very
low level, with breeding peaks in July and December. In a study conducted
in northern California, no definite spawning cycle was found. Ripe mussels
were seen from February to May and from December to February. Spawning was
observed in January, February, May, and December. In the natural
environment, temperature does not seem to provide a major stimulus for
spawning. 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 *9*.
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. 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 mm long
after 1 week. The veliger, which develops an umbo, may reach a length of
0.20 to 0.24 mm in 2 weeks. Just before metamorphosis, the larva develops
an eyespot and foot *9*.
The larvae of M. californianus have been reared in the laboratory to
metamorphosis in 17-24 days after fertilization. Eyespots were observed
when the larvae were 0.23 to 0.24 mm long *9*.
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 *9*.
POSTLARVAE AND RECRUITMENT
Mytilus californianus sets on barnacles, old mussel shell, and newly exposed
hard surfaces. One study found density of newly settled sea mussels was
highest on filamentous algae. Investigators disagree about settling
behavior *9*.
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 the legs of oil drilling
platforms. Setting areas are prepared by cleaning unwanted growth or
wrapping areas with special materials that attract wild spat *9*.
It probably takes many years for Mytilus to become established in the high
intertidal zone at approximatedly +1.8 to +2.4 m above mean lower low water.
Establishment is faster at lower levels *9*.
MATURITY
Sex ratios are generally equal and there is no indication of sex change with
Life History - 1 (DRAFT) - Life History
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
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 long *9*.
AGE AND GROWTH
The age of mollusks is determined by three methods: (1) size-frequency
studies; (2) the interpretation of growth interruption lines on the shell;
and (3) experimental methods involving the release and recovery of marked
individuals. One researcher 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 *9*.
In southern California, 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. Maximum
growth is 200-250 mm. Growth is fastest during the colder months and
slowest (sometimes nil) in mid-summer or above 20 degrees C *9*.
COMPETITORS
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. The distribution
of M. californianus is controlled by predation and physical disturbance *9*.
On Washington's exposed outer coast, M. californianus is the dominant
competitor for available space and will form dense monospecific stands
unless deterred. Mytilus californianus is one of the most consistent
occupants of space in the intertidal barnacle-mussel association there,
along with the barncles Chthamalus dalli, Balanus glandula, and B. cariosa,
and the sea anemone Anthopleura elegantissima *9*.
The name "California sea mussel" was given to M. californianus because of
its restriction mostly to the outer coast *9*. Mytilus californianus will
settle among Balanus and completely cover the barnacles, eventually
excluding them. Mytilus californianus denies space to M. edulis on the open
coast, but it seems to offer protection from wave action to those M. edulis
that do become attached *9*.
PREDATORS
A number of predators prey on mussels in California. Greater losses from
predation have been found 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. The sea star P. ochraceus may clear patches of M.
californianus, one of its preferred prey. In an experiment in Washington,
P. ochraceus was removed and the area eventually became a monospecific
stand of M. californianus. Pisaster ochraceus controls the abundance of the
dominant mussel and thus allows other species to coexist. Mytilus
californianus escapes predation from whelk predators (Thais spp.) by
attaining a variable minimum size of invulnerability. This mussel escapes
Life History - 2 (DRAFT) - Life History
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
predation by P. ochraceus by growing to a minimum size that increases as the
size of the sea star increases. Mean density of P. ochraceus may vary
locally by at least two orders of magnitufde, affecting local abundance of
M. californianus. In Washington, areas of low M. californianus abundance
and high P. ochraceus density occur side-by-side with dense stands of large
M. californianus that have low P. ochraceus density. The mussels had
probably escaped predation by attaining an invulnerable size *9*.
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; 2) 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 may be enhanced because Endocladia is the major settling
substrate for M. californianus larvae *9*.
The abrupt lower limit of M. californianus band (about +0.5m) is almost
certainly the most conspicuous feature of the rocky intertidal community and
is probably set by predation by P. ochraceus *9*.
The sea otter (Enhydra lutris) is known to eat both M. californianus and M.
edulis, but mussels form only a small portion 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
*9*.
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 *9*.
PARASITES AND ENCRUSTING EPIFAUNA
In California the parasitic copepod Mytilicola orientales was found in 13 of
20 M. californianus. The gonads of one M. californianus, from Humboldt Bay,
were heavily parasitized with trematode cercariae of the family Bucephalida
*9*.
Subtidal M. californianus may be overgrown by sponges, barnacles, anemones,
and other epifauna. Heavily encrusted mussels weighted less (in tissue
weight) than those less encrusted *9*.
LIFE HISTORY CODES -
Foraging Strategy: Scavenging
Gestation/Incubation Period: 1-2 days
Dispersion: Clumped
REFERENCES FOR LIFE HISTORY- 9
Life History - 3 (DRAFT) - Management Practices
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Constructing/maintaining piers
Beneficial Constructing/maintaining moring piles, dolphins, and bouys
Beneficial Constructing/maintaining jetties, groins, and breakwaters
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Other management practices [specified in comments]
Existing Regulating harvest of species being described
Existing Transplanting wild animals
Existing Stocking captive-reared wild-strain animals
Existing Regulating harvest - setting bag/creel limits
Existing Mariculture activities
Existing Other management practices [specified in comments]
Adverse Other management practices [specified in comments]
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 9
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 9
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 9
COMMENTS ON MANAGEMENT PRACTICES -
THE FISHERY
The California sea mussel, along with the bay mussel, supports a small
commercial bait fishery and is cultured for food on a small scale in
Tomales Bay and just north of San Diego *9*.
Mussels are an important food item throughout the world. There is potential
for culturing the California sea mussel for food more extensively in
California.
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 the legs of oil drilling
platforms. Setting areas are prepared by cleaning unwanted growth or
wrapping areas with special materials that attract wild spat *9*.
It probably takes many years for Mytilus to become established in the high
intertidal zone at approximatedly +1.8 to +2.4 m above mean lower low water.
Establishment is faster at lower levels *9*.
PROBLEMS WITH THE FISHERY
Problems associated with culturing the mussel for food are seasonal closures
caused by pollution and paralytic shellfish poisoning (PSP), finding
appropriate culture sites, and obtaining public acceptance to use of these
sites *9*.
No mussels can now be sold for human consumption from May 1 to October 31
because of the presence of paralytic shellfish poisoning *9*.
The consumption of mussels that have concentrated large amounts of the
poison-producing microscopic dinoflagellate Gonyaulax catenella sometimes
causes serious illness. In 1980, for example, poisoning was recorded in 98
residents of Marin and Sonoma counties, California, of whom two died *9*.
POLLUTION
Management Practices - 1 (DRAFT) - Management Practices
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
Because mussels are distributed along the coast, they are often subjected to
sewage and other kinds of pollution. The mussels may be unsafe to eat
and must be depurated before marketing *9*.
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. Although oil is only slightly toxic
to mussels, it may affect the marketing of the animals by tainting them. One
study 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 signigicant quantities of No.2 fuel
oil and outboard motor 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 *9*.
A number of trace metals are found in the soft tissues of mussels, including
AG, Cu, Cr, Mn, Pb, Cd, and Zn *9*.
HUMAN ASSOCIATIONS
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 *9*.
SPORT FISHERY
A limited sport fishery, where mussels are usually removed from pilings or
rocks by hand, now exists during the open season. A daily harvest of 25
pounds is allowed *9*.
AQUACULTURE
Four companies have shown interest in farming mussels for human consumption
in Tomales Bay,California, because the demand for a year-round 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 through suction hoses and are
cleaned, packaged, and shipped fresh to market *9*.
Management Practices - 2 (DRAFT) - References
Species mussel, California sea
Species Id M060009
Date 26 AUG 96
References
9* Shaw, W., Hassler, T., Moran, D. 1988. Species Profiles: Life
Histories and Environmental Requirements of Coastal Fishes and
Invertebrates (Pacific Southwest)--California sea mussel and bay
mussel. U.S. Fish and Wildlife Service Biol. Rep. 82(11.84) pp 16.
186* Turgeon, D.D., A.E. Bogan, E.V. Coan, W.K. Emerson, W.G.
Lyons, W.L. Pratt, C.F.E. Roper, A. Scheltema, F.G. Thompson,
J.D. Williams. 1988. Common and scientific names of aquatic
invertebrates from the United States and Canada: mollusks.
American Fisheries Society Special Publication 16. (ed.):277.
References - 1