(DRAFT) - Taxonomy
Species mussel, blue
Species Id M060008
Date 26 AUG 96
TAXONOMY
NAME - mussel, blue
OTHER COMMON NAMES - blue mussel, bay mussel, edible mussel, black mussel and pile mussel
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - Mollusca,
CLASS AND SUBCLASS - Bivalvia,
ORDER AND SUBORDER - Mytiloida,
FAMILY AND SUBFAMILY - Mytilidae,
GENUS AND SUBGENUS - Mytilus,
SPECIES AND SSP - edulis,
SCIENTIFIC NAME - Mytilus edulis
AUTHORITY - Linnaeus, 1758
TAXONOMY REFERENCES - 186 and 9
Taxonomy - 1 (DRAFT) - Status
Species mussel, blue
Species Id M060008
Date 26 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Commercial/consumption
Commercial/bait
Game (Consumptive Recreational)
See Comments
REFERENCES FOR STATUS - 168 and 9
COMMENTS ON STATUS -
Blue mussels have been cultured and harvested in western France and Spain
for hundreds of years. Although they have substantial commercial potential,
blue mussels have not been harvested as extensively in the United States.
Recently, the demand for mussels as fresh food has increased in the
U.S.*168*
Evidence indicates that mussel populations may be depleted if harvesting
continues at present or greater levels (Dow and Wallace 1954; and MARITEC
1978).
The bay mussel, along with the California 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, blue
Species Id M060008
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Estuarine UB1
Estuarine AB2
Estuarine FL3
REFERENCES FOR NWI - 168
Habitat Associations - 1 (DRAFT) - Food Habits
Species mussel, blue
Species Id M060008
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
FILTERER
REFERENCES FOR TROPHIC LEVEL - 168
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
General Phytoplankton Not Applicable
REFERENCES FOR GENERAL FOOD - 168 and 9
COMMENTS ON FOOD -
The diet of mussels consists of phytoplankton and detritus filtered from the
surrounding water.*168*
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 *9*.
Food Habits - 1 (DRAFT) - Environment Associations
Species mussel, blue
Species Id M060008
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
L Water Temperature: Between 15-21 degrees C
L
L
L
G Flow: Specified in Comments
LIM Water Level: Specified in Comments
LIM Wave intensity: specified in comments
LIM Currents: specified in comments
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 168
REFERENCES FOR LIMITING ENVIRONMENTAL ASSOC_ - 9
REFERENCES FOR FEEDING LARVAE ENVIRONMENTAL ASSOC_ - 168
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
Subtidal beds are located almost exclusively in areas with good currents,
especially around offshore islands and in the mouths of estuaries. These
beds are far less numerous than intertidal beds.*168*
Mussel abundance in coastal waters is determined by a number of natural
limiting factors which include predation, competition, and climatic
factors. The most significant competition among blue mussels is for food
and space between individuals. As younger mussels settle and accumulate on
established beds, older ones are buried and may be smothered. Mussels
regularly clean their shell surfaces with their foot, and this cleaning
action may ward off other mussels trying to settle on them. Mussels may
also move within the bed, out from other mussels to a more exposed
position.
Waves generated during storms can cause high mortality rates in mussels.
Some storms destroy entire mussel mats in the intertidal zone.
Consequently, on exposed rocky shores, the majority of blue mussels are
juveniles.*168*
COMMENTS ON LIMITING ENVIRONMENTAL ASSOC_ -
Mytilus edulis is sensitive to the effects of waves. The growth of M.
edulis is seriously affected by tidal exposure. In one study, 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. It has been stated that M. edulis needs to be submerged at
Environment Associations - 1 (DRAFT) - Environment Associations
Species mussel, blue
Species Id M060008
Date 26 AUG 96
least half the time to show significant growth *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*.
COMMENTS ON FEEDING LARVAE ENVIRONMENTAL ASSOC_ -
Pelagic larvae live in the water columns of estuarine and marine systems.
Optimal conditions include an adequate food supply, salinities between 15
and 40 ppt and temperatures ranging from 41 to 68 degrees F (5 to 20
degrees C).*168*
Environment Associations - 2 (DRAFT) - Life History
Species mussel, blue
Species Id M060008
Date 26 AUG 96
LIFE HISTORY
Completion of the life cycle requires about one year. In the
characterization area, spawning occurs at low levels throughout the year,
but the principal spawning period in the northeast is between mid-May and
mid-June, with another spawning possibly occurring in the fall.
Between 5 and 12 million eggs may be produced by a single female mussel in a
year. Sexes are separate and gametes are shed into the water where
fertilization occurs. Depending on environmental conditions, the larvae are
pelagic for approximately 19 days. In the pelagic environment, the larvae
are subjected to biotic and abiotic stresses. Mortality at this stage is
believed to be very high.
The larvae first settle on flexible substrate such as algae, hydroids, or
byssal threads but they may detach and resettle one or more times until they
find an appropriate substratum. The larva may delay metamorphosis for some
time if the appropriate substratum is not available; however, after about 8
weeks or when a length of 0.06 to 0.4 inches (1.5 to 10mm) is reached the
larva will settle wherever it is at that time. Upon metamorphosis, the
mussel is considered a juvenile.
In the first year juvenile mussels have been observed to reach a length of
0.8 to 1.6 inches (20 to 40 mm) in Massachusetts.*168*
SPAWNING ON THE WEST COAST
The bay mussel has a single massive spawning output each year which can
occur in late fall and/or winter along the central California coast. In
northern California spawning has been observed first in May and again from
July through November. In the natural environment, temperature does not
seem to provide a major stimulus for spawning *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*.
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*.
RECRUITMENT
In southern California M. edulis settles in massive numbers in some years,
but sparsely in other. Settlement of M. edulis is generally gregarious *9*.
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 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
Life History - 1 (DRAFT) - Life History
Species mussel, blue
Species Id M060008
Date 26 AUG 96
from size. Most workers have attempted to age mussels through
interpretation of growth interruption lines, although some have studied
marked individuals *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. edulis is controlled by predation and physical disturbance as well as
by competition *9*.
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.
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
edulis has been found to be preferred over M. californianus by nine
invertebrate predators: two sea stars, five species of muricid gastropods,
and two species of crabs. A third crab that ate mussels showed no
preference for a particular species *9*.
On the outer west coast, the lower limit of M. edulis band (about +2.9 M) is
probably determined partly by predation by gastropods, birds, and sea stars
*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*.
REFERENCES FOR LIFE HISTORY- 168 and 9
Life History - 2 (DRAFT) - Management Practices
Species mussel, blue
Species Id M060008
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Regulating harvest of species being described
Beneficial Restricting/regulating human disturbance of populations
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 Regulating harvest - setting bag/creel limits
Beneficial Other management practices [specified in comments]
Adverse Dredging
Adverse 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]
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 168 and 9
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 168 and 9
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 9
COMMENTS ON MANAGEMENT PRACTICES -
Evidence indicates that mussel populations may be depleted if harvesting
continues at present or greater levels. Overharvesting and natural factors
may have contributed to the decline in abundance. Other human impacts on
mussels include habitat destruction, oil spills, dredging, and discharge of
contaminants. Evidence of the effect of these factors on populations of
mussels in coastal Maine is lacking.*168*
Mussel culture is being explored as a means of meeting market demand. For
culturing, individuals from natural populations at one location are
sometimes needed to supplement natural juvenile populations in other
locations. This practice potentially impinges on natural populations
because it strips juvenile mussels and associated animals (amphipods and
oligochaetes) from exposed rocky shores. Transplanting mussels carries the
same risks as transplanting clams, i.e., the potential for spreading "red
tide" via ingested cysts.*168*
Other problems include potential overharvesting and the harvesting of poor
quality mussels (those that are small in size or contain pearls). If
harvests continue to be low in quality, commercial demand is likely to
decline.*168*
THE FISHERY
The bay mussel, along with the California sea 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, California *9*.
Mussels are an important food item throughout the world. There is potential
for culturing the bay mussel for food more extensively in California.
Management Practices - 1 (DRAFT) - Management Practices
Species mussel, blue
Species Id M060008
Date 26 AUG 96
Management Practices - 2 (DRAFT) - Management Practices
Species mussel, blue
Species Id M060008
Date 26 AUG 96
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 *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
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 significant 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
Management Practices - 3 (DRAFT) - Management Practices
Species mussel, blue
Species Id M060008
Date 26 AUG 96
cleaned, packaged, and shipped fresh to market *9*.
Management Practices - 4 (DRAFT) - References
Species mussel, blue
Species Id M060008
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.
168* Fefer, S. and P. Schettig. 1980. An Ecological Characterization of
Coastal Maine. 1-3. Department of the Interior.
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.
References - 1