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Mussel aquaculture in the Northeast

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Consumption of blue mussels (Mytilus edulis and M.
trossulus) and use as fishing bait have long been sup-
ported in the northeastern United States by a small-scale
fishery supplying largely niche markets. Mussels have
been consumed since pre-colonial times and served as a
ready supply of inexpensive seafood protein during
wartime periods (1917 and 1942) in America (Miller,
1980). Markets for mussels expanded in the 1970s and
1980s leading to the introduction of mussel farming in
the Northeast. The first U.S. mussel farm was estab-
lished by Mr. Edward Meyers of Walpole, Maine, who in
1973 founded Abandoned Farm on a 5-acre (2-hectare)
site in the nearby Damariscotta River. Other early mus-
sel farms established in the 1970s included the 60-acre
Blue Gold Mussel Farm on the East Passage of Narra-
gansett Bay in the town of Middletown, Rhode Island
and The Great Eastern Mussel Farm in Tenants Harbor,
Maine (Hurburt and Hurlburt, 1980). Since these pio-
neering farms, others have become established in Maine,
New Hampshire, Massachusetts and Rhode Island.
The process of mussel farming involves the collec-
tion of juvenile mussels (“mussel spat”), harvesting the
spat and placing it into culture equipment and growing
the mussels to market size for harvest and sale. In gen-
eral, most of the mussel farms in the Northeast Region
are of the off-bottom type in which mussels are grown
on ropes either suspended from rafts, or strung on sock-
ing materials that are suspended from rafts or in either
floating or submerged longline systems. Bottom culture
of mussels occurs in Maine, using methods similar to
those developed in the Netherlands and Germany,
though most new efforts employ off-bottom mussel
farming methods that produce a cleaner more uniformly
sized product (Hurlburt and Hurlburt, 1980).
The aim of this NRAC fact sheet is to provide a gen-
eral overview of the various mussel farming techniques
as they are currently practiced in the Northeastern Unit-
ed States. References are cited that provide more in-
depth information on particular production systems, and
prospective growers are also encouraged to contact their
local marine extension agent, aquaculture association,
state marine fisheries agency, or the Northeast Regional
Aquaculture Center.
Mussel farming systems
Mussel production can be generally categorized into
suspension culture–where the mussels are grown in the
water column–or bottom culture. As a general rule, sus-
pension culture is more expensive in labor and equip-
ment, but results in a product with high meat-to-shell
ratio–often in excess of 50 percent–and less grit. Bottom
culture has the advantage of lower cost, though more
care is needed to provide a grit-free product, and meat
University of Maryland, 2113 Animal Science Building
College Park, Maryland 20742-2317
Telephone: 301-405-6085, FAX: 301-314-9412
E-mail: ssadams@umd.edu Web: http://www.nrac.umd.edu
Mussel Aquaculture in the Northeast
Dana Morse, University of Maine, Maine Sea Grant
Michael A. Rice, University of Rhode Island Cooperative Extension
NRAC Publication No. 211-2010
yields are typically lower than suspension culture. The
two basic suspension systems used in the Northeastern
United States are rafts and submerged longlines,
although floating longline systems are in common use in
Canada.
Modern mussel rafts are constructed with steel I-
beam main frames, wooden crossmembers, and large
polyethylene floats. Most measure 40 feet square and
are capable of supporting up to 400 droplines of roughly
45 feet-long each (Figure 1). Roughly 40,000 lbs. of
mussels can be reasonably expected in an 18-month
cycle from seeding to harvest. Raft systems are most
appropriate for reasonably protected areas, in fairly shal-
low water. They have the advantage of providing a sta-
ble work platform, and the disadvantage of being
susceptible to damage from heavy weather (Clime and
Hamill, 1979).
Longline systems consist of a main horizontal line,
anchored at both ends, with flotation along the center
segment (Figure 2). Dropper lines are then suspended
from the main line into the water column (Figure 3).
Longline systems have the advantages of being adapt-
able to deeper waters, or more exposed sites, and can
support high capacity and high efficiency. The disad-
vantage of longline systems is that they can be more dif-
ficult to deploy, particularly in deeper waters, and they
often require larger work boats with specialized hauling
gear (Lutz, 1985).
Bottom culture is an approach that uses reduced
densities of mussels on the sea floor to achieve high
growth rates and a good meat-to-shell ratio. A producer
may locate an appropriate site and seed small mussels on
to it, or may find an established bed, and use a strategy
of thinning and dispersal to grow the product. Careful
site selection is especially important, as the influences of
temperature, primary productivity, siltation, predators
and other competing organisms can have great effects on
the crop. Bottom culturists avoid the capital and main-
tenance costs of growout gear, but must spend extra
attention to quality, and generally experience lower meat
weights than suspension culture methods.
2
Figure 2. Diagrammatic representation of a submerged
longline system used in offshore waters in New Hampshire.
Diagram courtesy of Richard Langan, University of New
Hampshire.
Figure 3. A diver inspecting dropper lines with mussels on
a submerged longline system in New Hampshire. Photo
courtesy of Richard Langan, University of New Hamp-
shire.
Figure 1. Mussel raft: 40 square foot, with some dropper
lines visible under the platform. Photo courtesy of Dana
L. Morse, Maine Sea Grant.
190 kg
buoyancy
10 M
130 M
200 M
3,500 kg
concrete
anchors
Mussel spat collection
Unlike the practices of clam farming or much of the
oyster farming in the Northeast that rely upon hatcheries
for a source of seed, mussel farms rely upon the collec-
tion of setting mussels from the wild as their seed
source. Mussels typically spawn in the late spring as
water temperatures rise and develop for about two weeks
as planktonic larvae in the water column. At the end of
the larval period, the mussels settle and metamorphose
into small juveniles known as spat. (For a more complete
discussion of the reproduction and life history of mus-
sels refer to NRAC Fact Sheet 210-2010.) In the North-
east Region, mussel spatfall typically occurs as an
annual maximum between late April and early July and
is largely dependent upon water temperature. However
temperature alone is not the only criterion determining
the time of mussel spawning; available phytoplankton in
the estuary during the spring months also affects spawn
timing (Newell et al., 1982). Since maximum spatfall
varies by location, it is most important as part of the
mussel farming site selection process to evaluate spatfall
timing and abundance by placing test collectors into the
water during mid-spring or fall depending upon location.
An alternative to using spat collectors for predicting
the timing of spatfall is to monitor the appearance of the
mussel larvae in the water. This can be done by using a
small 12-volt bilge pump (15 gpm) attached to a weight-
ed line and lowered into the water (Figure 4). Water is
then passed through a plankton net, with a mesh size of
about 60µm. Such nets are available from an aquacul-
ture equipment supplier. Water samples can be pre-
served in alcohol and stained with a few milligrams (a
tiny pinch) of Rose Bengal aboard a boat, and the sam-
ples examined using a stereoscopic microscope for the
presence of mussel larvae and other plankton. Rose
Bengal is a biological stain often sold in 5g-quantities by
biological laboratory supply companies. To make things
simpler aboard the boat, it is recommended that before
setting out to collect plankton samples, it is easiest to
prepare sample transport bottles with 100mL of ethanol
with the small pinch of Rose Bengal stain added (Figure
4). You can later examine the samples at your conven-
ience in the laboratory using a stereoscopic microscope.
Identification of the mussel larvae and other plank-
ton can be aided by appropriate guide materials (e.g.
Loosanoff et al., 1966; Smith and Johnson, 1996). Your
local aquaculture extension agent can help you get start-
ed if you choose to use this method of predicting spatfall
timing in your area.
Originally, mussel spat collectors consisted of sec-
tions of frayed rope tied to rafts or floating longlines.
There are now a variety of spat collector materials com-
mercially available that consist of a rope core, with radi-
ally extended fibrous material or looped fibrous
material. Spat collectors with looped fibrous material
generally collect mussel spat more effectively in waters
with higher current speeds, but the fibrous collectors
(also sometime known as a “Christmas tree” type collec-
tor) have the advantage of being able to be mechanical-
ly stripped of adherent seed mussels with lesser
frequency of breakage losses.
The process of spat collection involves hanging spat
collectors in the water just prior to the predicted maxi-
mum spatfall. Timing is critical, as deploying the collec-
tors too late will miss the set, and deploying too early
will allow fouling by other marine organisms that would
compete with the setting mussels for space. Once mus-
sels set they typically remain on the spat lines until they
grow to become 1 cm (about 0.5 inch) long seed mussels
at which time they can be stripped from the spat lines
(Figure 5).
3
Figure 4. Mr. Joseph Goncalo demonstrating the
method of using a submerged 12-V bilge pump to obtain
water samples for analysis of larval bivalves in the water
column. Note the presence of a 1-liter glass sample bot-
tle containing a pre-measured volume of alcohol to kill
and preserve the mussel larvae and all the other plank-
ton in the water sample. Photo by Michael A. Rice, Uni-
versity of Rhode Island.
One frequent question among those new to farming
mussels is why the mussels cannot be simply left on spat
collectors until they grow to market size. The answer is
that mussel densities can be so high that they will be
stunted because of competition for food resources, and if
the set of spat is thick enough, the weight of the crowd-
ing mussels causes section or the entire mass of collect-
ed mussels to fall off and drop to the bottom. However,
some of the seed ‘dropoff’ problem can be controlled by
cross-pegging of spatlines (Figure 6).
Mussel seed stripping and socking
Once mussel seed is available, it needs to be trans-
ferred to the growout lines for either raft or longline
production – in a step called ‘socking.’ This procedure
allows mussels to attach (or ‘knit’) themselves to the
load-bearing portion of the mussel line, by way of
attachment by their byssal threads.
Once mussels reach about 1 cm (0.5 inch), the spat
collectors are retrieved and the mussel seed is stripped
from them. In small mussel farming operations, spat
collectors may be typically about 4.5 m (15 feet) in
length and the can be manually stripped of mussel seed
by using some rugged gloves. For larger mussel farm-
ing operations there are a variety of spat line stripping
machines that can be used either aboard a vessel or on
shore as is convenient.
Socking can be accomplished by allowing mussels
to fill the inner space of a long tube of socking materi-
al, or by wrapping the mussels and center line in a
biodegradable material, such as cotton. For larger-
scale mussel farming operations there is commercially
available machinery, either to fill long lengths of cotton
socking (ie; for continuous longlines), or to alternative-
ly to wrap long dropper lines in cotton sheeting (such
as for mussel rafts) (Figure 7).
Discontinuous longlines, with drop lines of 4.5m
(15ft) or so, most often use polyethylene socking,
whereas the continuous longlines and mussel rafts most
4
Figure 5. Freshly set mussels on a spat collector suspend-
ed from a floating longline. Photo by Michael A. Rice,
University of Rhode Island.
Figure 7. Mussel socking machine, manufactured by
Aguin, used in mussel raft culture. Drop lines are fed
under the hopper, and mussels are wrapped up against
the line by cotton sheeting. The cotton sheet degrades,
after the mussels have attached their byssal threads to the
dropline. Photo courtesy of Carter Newell, Pemaquid
Mussel Farms.
Figure 6. Mussel seed on raft drop line, with cross pegs
still visible. Photo by Carter Newell, Pemaquid Mussel
Farms.
often use cotton socking or wrapping as socking mate-
rial. Shorter drop lines can be created with the use of a
socking table; essentially a hopper for seed mussels. At
the bottom of the socking table is a pipe (the ‘horn’) of
a diameter that snugly fits inside socking. Prior to
placing mussels in the sock, a rope is inserted down the
center of the sock to provide strength to bear the weight
of the mussels as they grow. Mussels are then filled
into the sock by running water into the socking table,
which carries seed mussels into pipe and the sock,
much as meat is forced into sausage casings in the
sausage making process. For larger-scale mussel farm-
ing operations there are commercially available
machinery to fill socks that can be in the hundreds of
meters in length (Figure 8).
Once the mussel socks are suspended into the water
either from rafts or longlines, the mussels will grow
and eventually work their way through the netting
holes in the socking material so that the socking mate-
rial and its internal reinforcement rope are internal to
the growing mass of mussels (Figure 9). In especially
long mussel socks with lines in excess of 10 meters, the
mass of growing mussels still can be heavy enough to
rip away masses of mussels from the sock. To prevent
mussel drop-off, socking pins, which are simply rigid
plastic rods (about 20cm long and 1.5cm diameter) that
are tapered at both ends, can be placed at two- to three-
meter intervals to provide horizontal reinforcement to
the mussel sock. Alternatively, socking collars (Figure
10) can be used. In this way the weight of the mussels
is borne by either the socking pins or the socking col-
lars at short intervals instead of the weight bearing
down along the entire length of the socking tube.
5
Figure 8. A shipboard continuous socking machine for
seed socking of continuous longline droppers. Photo cour-
tesy of Richard Langan, University of Hew Hampshire.
Figure 9. A mussel sock after deployment showing mus-
sels that have emerged from the sock. Photo by Michael
A. Rice, University of Rhode Island
Figure 10. A typical mussel socking collar or anti-slough-
ing disk that is made of polypropylene plastic and is 20cm
(8 inches) in diameter. Photo courtesy of Fukui North
America
Problems occasionally encountered
during growout
Among the various problems to be managed during
the mussel growout process is losses due to predation.
Refer to NRAC Fact Sheet No 2010-210 for a discussion
of common predators associated with mussel farms. As
stated earlier, mussel farms using on-bottom techniques
are prone to greater predation losses to bottom-dwelling
predators. However, mussel farmers engaged in on-bot-
tom mussel farming use a variety of methods to lessen
the impact of predators, including the use of crab traps.
Pests could include organisms such as barnacles,
and solitary or colonial ascidians, also known as sea
squirts. Sea squirts such as Ciona intestinalis, Styela
clava, Botryllus scholsseri, Molgula manhattensis and
Botrylloides violaceous can smother the crop, and make
the gear too heavy to service. (Figure 11).
For suspension growers, lifting culture lines and
spraying with a 5 percent solution of hydrated lime
mixed in seawater, followed by a short air-drying peri-
od, will help to control sea stars and crabs, and many
fouling pests such as sea squirts. Bottom culturists need
to use good site selection in limiting the impacts from
fouling organisms, although in many cases, the other
organisms existing on the sea bed can limit excessive
fouling as well. Predator control for bottom culture is a
mixture of seeding the correct size seed, good timing
(seed when predators are less active, such as late fall or
early spring), and occasionally trapping or using so-
called ‘starfish mops’.
On occasion, various mussel pests such as pea crabs
and mussel pearls are problematic. In some locations
such as Rhode Island, mussel farms are challenged by
infestation of pea crabs that act to decrease the mar-
ketability of mussels. Pea crabs slightly affect the
growth of mussels and may be a stressor, but their pres-
ence is more of a nuisance (Bierbaum and Ferson,
1986). At present there is no good means to control pea
crab infestations other than to select sites that are less
prone to infestations. Pea crabs are much less of a prob-
lem in Maine and other northern locations, but in these
locations mussel pearls, resembling gritty grains of sand
that can form in mussels, also reducing their marketabil-
ity. (Lutz, 1980). Much like control of pea crabs, initial
site selection to avoid areas where pearl formation is
critical, but harvest of mussels prior to their reaching
three-years of age is helpful in avoiding pearl formation.
Predation from diving ducks such as the Common
Eider (Somateria mollissima) can be devastating to the
mussel producer, certainly with the potential to wipe out
an entire crop (Figure 12). Raft producers can use pred-
ator nets to surround the raft, whereas longline and bot-
tom culturists cannot. The best control against duck
predation is a personal presence by the farmer, to chase
ducks away. Since a personal presence is often not pos-
sible on a daily basis, such as when weather does not
allow it, producers may rely on a set of deterrents.
Deterrents are best used in rotation and combination.
Common approaches include the use of owl decoys,
chasing the ducks off the site – sometimes using ‘crack-
ers’ fired from a hand gun-like device, lasers (both over
and under the water) or mooring an unmanned skiff on
the farm. But the birds become accustomed to many of
6
Figure 11. Sea Stars and other fouling organisms on a
drop line from raft culture. Photo courtesy of Carter
Newell, Pemaquid Mussel Farm.
Figure 12. A group of Common Eider ducks – Somateria
mollissima. An adult bird can eat over 30% of its body
weight in mussels per day, and eiders often collect in
groups, called ‘rafts’ of several hundred individuals.
Photo courtesy of Erick Swanson, Maine Cultured Mus-
sels.
these methods rendering them useless over time, and the
noise makers often do more to annoy the neighbors of
the farms than they do to the birds! Sometimes floating
netting material over the farms can exclude some of the
ducks.
In recent years, the use of underwater acoustics has
come into play, to keep ducks from feeling comfortable
on the farm site, and to keep them from coming too close
in the first place. Pioneering work in Western Europe
has led to the adoption of underwater acoustic deterrents
in Maine, and advances in this area are anticipated. By
recording the sound of the specific chase boat used on
the farm, and then constructing a device to periodically
play the sound of that boat (and other sounds, typically
in rotation), diving ducks can be kept reasonably at bay,
without the producer being on site. Again, ducks will
acclimate to this method if over used, but underwater
acoustics can be a critical piece of an overall deterrent
strategy (Ross et al, 2001).
Harvesting re-socking
In today’s industry, harvesting requires speed and
high capacity; much different from the harvests of years
past, where fishermen employed long-handled rakes to
fill a skiff or dory. Nowadays, harvesting on bottom
sites is generally restricted to drags of various construc-
tion, such as the chain sweep drag used commonly in
fisheries for scallops and urchins. Drags (commonly
referred to as ‘dredges’) are high-capacity equipment,
often up to 4m in width, and capable of catches in the
hundreds or thousands of pounds. The harvest vessel
may also be equipped with a tumbler, a cylinder of weld-
ed steel rod commonly mounted on the stern of the ves-
sel, which allows small mussels, rocks and debris to be
removed from the catch. Bottom-dragged mussels may
then be purged in tanks or baskets for several hours to a
few days, to allow sand and mud to pass from the mus-
sel, prior to packaging and shipment.
Harvesting from rafts is most frequently done with a
mast-and-basket arrangement; a large steel basket is
lowered under the hanging lines of the raft a few at a
time, and the basket is raised beneath them. The basket
is hinged such that it opens like a clamshell, and mussel
lines are allowed to drop to the floor of the work barge
or vessel, ready for stripping and processing.
Longline harvesting is an efficient process. Most
vessels, no matter what kind of longline arrangement
(continuous or discontinuous), use a set of star wheels, to
raise the backline of the mussel ropes to a good working
height. At that point, continuous longlines can be cut
from the backline and run through the mussel stripper.
Single dropper lines can be cut by hand, and collected in
a container. The function of the star wheel (one is driv-
en, usually hydraulically, and the other is simply a roller)
is to allow the vessel to pull alongside the backline and
remain in proper position. By running the star wheel
forward or backward, the vessel moves along the back-
line, without having to engage the propeller.
Processing: purging, declumping,
debyssing and grading
Bottom-grown mussel producers will often include a
purging step, where the mussels are placed into a large
container or a tank, with a high flow of clean seawater
pumped through the stock. The function of this step is to
reduce the amount of mud and grit inside the mussel,
leaving a cleaner product.
Regardless of culture type, the steps of declumping,
debyssing and grading are virtually always taken prior to
packaging. Each stage requires specialized equipment;
these are often placed in series with conveyers in
between, and are usually hydraulically operated.
Hydraulics can employ vegetable oil in place of petrole-
um-based hydraulic oil, and this can reduce the negative
impacts of leaks or spills. In recent years, processing
machinery is often mounted on a floating barge, placed
close to the production site.
First, a declumper is employed to reduce the groups
of mussels down to individuals. Some growers replace
the harder paddles inside the declumping unit with soft-
er rubber paddles, to reduce the amount of breakage.
The declumper needs to work at the proper angle and the
proper speed, and it will take a little trial and error to
work out the correct feed rate. The declumper should
have a good output of single mussels (not still attached
to one another with byssal threads), and should have a
minimum of broken shells; less than 2 or 3 percent.
The debyssing machine uses a set of narrow cylin-
ders that rotate counter to one another to grab the byssal
threads (the ‘beard’) and pull them from the mussel.
This leaves a cleaner and more palatable product, but
also reduces shelf life somewhat, as the mussel is unable
to close its’ shell completely and will gradually lose the
shell liquor. In many cases, the last step in processing is
grading, so that the product has uniform size. Mechani-
cal graders use rolling bars placed nearly parallel to one
another, but with an increasing distance between them
7
along their length. Mussels travel over the rolling bars,
and the smallest mussels drop out first, based on the
width of the mussel. Bins placed at certain distances
along the length of the grader allow similarly-sized mus-
sels to be retained together. At this point, when the orig-
inal clumps of mussels have been separated into
individuals, have had the beards removed, and have been
grouped by size, they are ready for packaging.
Packaging and Shipping
Mussels coming from the production site and
through the processing plant should be cooled as quick-
ly as possible, to approximately 38oF, to retard the
growth of bacteria, and to achieve maximum shelf
life–seven days. Depending on customer preferences,
mussels are often packed into two-pound mesh or perfo-
rated plastic bags, or into larger quantities usually up to
20 pounds. Packaging should allow liquid to drain, and
should be easy to handle. If individual bags are then
consolidated, insulated, wax boxes with the company
name, logo and other details should be used. Boxes that
sag or leak are not satisfactory with many shippers, and
the identifying marks on the box are beneficial in mar-
keting and branding your product. Larger amounts may
require the use of pallet-size insulated containers
(Newell, 1990).
Selecting a site to culture mussels
Choosing a good site for farming mussels requires
considerable local knowledge of the area as to its exist-
ing uses and an assessment of the area’s potential for
producing mussels. Among other things, this should
include the availability of a steady setting mussel seed
supply, as well as sufficient currents and phytoplankton
(food) concentration to allow for rapid growth. The fol-
lowing factors should be considered when siting your
mussel farm:
Speed of the current
Phytoplankton and other suspended food abundance
Water temperature
Water salinity
Exposure to wave action and storm surges
Sediment type
Water depth
Predators & pests, including excessive fouling
potential
Frequency of occurrence of harmful algal blooms
(HABs)
Occurrence of ice
Road access to the site (proximity to shore)
Security concerns
Sanitary water quality classification (approved,
conditional, or prohibited)
Navigational concerns
Presence or absence of existing fisheries
It is often advisable to establish several small-scale
experimental trial farming sites as part of a site selection
procedure. A whole host of potential problems including
lack of adequate seed set to conflicts with other users of
the proposed aquaculture site can be discovered through
farming trials.
A major consideration for the siting of any mussel
farm is the availability of adequate food for the mussels
and adequate current such that food (phytoplankton and
particulate detritus) can be carried to the mussels and
that the waste products from the mussels can be carried
away. Considerable work has been done to correlate
mussel food availability, current speed and the growth of
mussels using various types of culture gear (Incze et al,
1991; Newell et al., 1998). In general mussel culture
sites are best when there is in excess of 10 mg/L avail-
able particulate food in the water with average current
speeds in excess of 30 cm/sec. Slower current speeds,
however, could be offset by higher food concentrations
in the water.
Most of the food for mussels consists of live phyto-
plankton cells in the water column, however, particulate
detritus and some bacteria are also food for mussels.
Available food for mussels can be measured in a variety
of ways. Since all phytoplankton carry chlorophyll-a
(chl-a) as a photosynthetic pigment, measurement of chl-
a concentrations in the water is a good index of available
food. Alternatively, samples of seawater of known vol-
ume from potential mussel aquaculture sites could be
vacuum filtered using fiberglass filters with pore sizes of
about 1 µm or less, then dried in a drying oven at 100oC
and weighed the ashed at 450oC and weighed again to
obtain an organic biomass measurement. If you are
unfamiliar with some of the equipment or methods for
determining food availability for mussels or how to
make the water quality measurements, contact your
state’s aquaculture extension specialist for some assis-
tance.
Not all phytoplankton is good for mussels. Certain
types of algal blooms can be aging to mussel farming by
posing a health threat to consumers (Jin and Hoagland,
2008). As part of the mussel farm site selection process,
studying the history of official closures of your area to
8
harvest of mussels can be a good indicator if the area is
problematic and to be avoided.
A simple way of measuring current speed is to use a
tethered current drogue (float), a measuring tape, and a
stopwatch. Release the current drogue from a boat and
note the time it takes to travel to extend the drogue teth-
er to its full outstretched maximum. The current speed
is then the length of the drogue tether divided by the
travel time in seconds. So if, for example, the drogue
traveled 1,000 cm in 40 seconds, its speed would be 25
cm/sec. Drogues can be complicated, or as simple as
using an orange floating on the water surface.
You can measure temperature and salinity on your
site using a thermometer and salinity refractometer or a
hydrometer that can be purchased from an aquaculture
gear suppliers. Another useful measurement is the over-
all water turbidity measured by a Secchi disk. The over-
all turbidity of water is affected by the amount of
particulate material (including phytoplankton) in the
water, so Secchi disk turbidity measurements can be an
indicator of relative food abundance in the water. Make
sure you record all of your observations at your sites. All
of these data can help you understand the differences
among your sites and the sites of other mussel farms, and
give you insights into how varying water conditions
affect mussel growth and productivity. If you are unfa-
miliar with some of the equipment or methods for deter-
mining food availability for mussels or how to make the
water quality measurements, contact your state’s aqua-
culture extension specialist for some assistance.
Planning a Business
in Mussel Production
Shellfish aquaculture requires a broad range of
expertise and ability, in everything from permitting and
regulation to the production technology and husbandry
itself. However, since mussel production nearly always
relies on significant volume of product to be profitable,
the prospective grower needs to be prepared especially
in the areas of sales and marketing, equipment, and
financing. Strong consideration should be given to
developing a thorough business plan, and an accompa-
nying marketing plan. In addition, appropriate capital-
ization is critical, to account for the known costs and to
allow for the things that always take longer or cost more.
Business planning outlines relative to raft culture and
longline culture are available, to help in these exercises
(Hoagland et al., 2003; Anonymous, 1999).
Acknowledgments
This work was conducted with the
support of the Northeastern Regional
Aquaculture Center, through grant
number 2006-38500-17605 from the
National Institute of Food and Agri-
culture (NIFA), U.S. Department of
Agriculture. Any opinions, findings,
conclusions, or recommendations ex -
pressed in this publication are those of
the authors and do not necessarily
reflect the view of the U.S. Depart-
ment of Agriculture.
References
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References continued
... While mussels are grown in New England with a variety of gears (Morse and Rice, 2010), offshore sites have found the most success with submerged longline systems. This technology, used in New Zealand, Japan, and elsewhere, " support[s]high capacity and high efficiency " (Morse and Rice, 2010, p. 2) allowing operators to take advantage of offshore conditions, such as space for economies of scale and beneficial water quality for growth (Cheney et al., 2010;Langan, 2013). ...
... While mussels are grown in New England with a variety of gears (Morse and Rice, 2010), offshore sites have found the most success with submerged longline systems. This technology, used in New Zealand, Japan, and elsewhere, " support[s]high capacity and high efficiency " (Morse and Rice, 2010, p. 2) allowing operators to take advantage of offshore conditions, such as space for economies of scale and beneficial water quality for growth (Cheney et al., 2010;Langan, 2013). Both " the biological and engineering feasibilities of this new kind of technology " have been demonstrated in regional pilot projects (Hoagland et al., 2003, p. 11), and all offshore mussel operations in New England are using this technology. ...
... Informants agreed that environmental conditions are viable for offshore mussel expansion in New England, with some caveats. Some expressed concerns about interactions with pest species, but none felt these would be prohibitive (see alsoMorse and Rice, 2010). In the case of pea crabs and sea squirts that can infest or foul mussels, for instance, offshore currents are believed to be more conducive to dispersing pest larvae away from farm sites (whereas semi-enclosed inshore sites run a greater risk of larval settlement), and care can be taken to avoid transporting them to sites via boat (e.g., O4, O6, P5). ...
... The suspension of crop lines can be achieved with different strategies and different infrastructures. There are two main types of suspension culture: Raft culture and longline system [2]. In modern raft system, mussel crop lines are put within a structure made from a combination of wooden and steel frames to make a stable platform along with large floaters [2]. ...
... There are two main types of suspension culture: Raft culture and longline system [2]. In modern raft system, mussel crop lines are put within a structure made from a combination of wooden and steel frames to make a stable platform along with large floaters [2]. However, it can also be made from an old wooden boat or a catamaran boat to accommodate up to 1000 crop lines [1]. ...
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This paper describes a numerical model to simulate the behavior of a mussel longline system, subjected to environmental loads such as waves and current. The mussel line system consists of an anchor, a mooring chain, a long backbone line, mussel collector lines and buoys. The lumped-mass open-source code MoorDyn is modified for the current application. Waves are modelled as a directional spectrum, and the current as a homogeneous velocity field with an exponential vertical distribution. A Coulomb model is implemented to model the horizontal friction between nodes and the seabed. Cylindrical buoys with three translational degrees-of-freedom are modelled by extending the simplified hydrodynamic model in use for line's internal nodes with additional properties like cylinder height, diameter and mass. Clump weights are modelled in a similar way. For validation purposes, the results of the present software are compared with the commercially available lumped-mass based mooring dynamic software, OrcaFlex.
... that would greatly increase global food production (Morse & Rice, 2010;Langan, 2013). Some countries, such as China, have already advanced farm technology that has been implemented as far as eight miles offshore (Marra, 2005). ...
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Aquaculture is the fastest growing food production system in the world. Aquaculture growth is heavily influenced by the governance system that establishes property rights and determines the rules by which individuals and communities must follow. This dissertation focuses on the social and ecological factors that influence development of marine aquaculture, as they exist within the governance system, in Maine, USA. In Maine, the marine aquaculture industry is experiencing a period of intense growth necessitating further understanding of the factors shaping its development. Chapter 2 analyzes semi-structured key informant interviews to identify challenges and opportunities to inform sustainable industry growth. Research participants identified regulatory, environmental, technological, socio-cultural, and economic challenges and opportunities. The leasing system, climate change, infrastructure, public perceptions, and access to capital were major challenges identified. Opportunities include favorable environmental conditions, farm innovation, skilled workforce, strong product demand, and the research and development capacity in Maine. Chapter 3 identifies factors influencing development of intertidal soft-shell clam (Mya arenaria) aquaculture in Maine and how it would intersect with the wild fishery. Intertidal clam aquaculture has the potential to diversify and sustain a declining wild fishery that is important to the economies and ii cultures of coastal communities. This qualitative study utilized semi-structured interviews with wild clam harvesters, state regulators and other key stakeholders. Participants identified predation, environmental change, and failing state management efforts as leading causes for the overall decline in wild clam populations. Maine’s intertidal property rights system, loss of access to the intertidal, and community preferences regarding privatization of this resource are primary challenges for development of intertidal clam aquaculture. Chapter 4 examines why non-governmental organizations (NGOs) are becoming involved in aquaculture in Maine and how they are shaping its development. NGOs have played instrumental roles in development and management of a variety of natural resources. In aquaculture, NGOs have historically organized in opposition to development, but this is changing. Semi-structured interviews with Maine NGOs involved in the aquaculture sector indicate they are playing critical roles in development processes including research, economic development, training, education and outreach. Findings suggest most NGOs have become involved in aquaculture in response to rapid industry growth and new funding opportunities. The research conducted in this dissertation used a qualitative research approach to help identify factors influencing development of aquaculture in Maine. The social and ecological context of a place are unique so while global trends may inform development, site specific data is needed in order to approach development of the sector in a sustainable fashion. Particular attention is given to the governance system, a major component of social-ecological systems, which has enormous influence over the use and management of natural resources. The findings of these chapters indicate a need for marine planning which could reduce user conflicts as competition for coastal waters intensifies.
... Mussel farming industry has experienced that older mussels starts to produce pearls and have advised harvesting individuals before they reach three years to prevent pearl occurrence (Morse & Rice 2010). ...
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Full-text available
Mussels (Mytilus spp.) from the Norwegian coast produce pearls, up to as many >360 pearls per individual, and it seems to be a southern-northern gradient with more pearls in mussels from the south than from the north. Out of the 280 mussels studied, nearly 2000 pearls were found, and the mussels producing pearls were all >4 cm. Size and condition index did correlate with the pearl frequency, while microplastics did not. Mussel health is important to study as they are important actors in the coastal ecosystem, as bioindicators for environmental monitoring, as a food source as well as the recent reports on changes in their distribution across the Norwegian coast.
... Mussel farmers, who use ''buchot'' and suspended culture techniques, collect seed directly from the water column on spat collectors, which are typically ropes hung on wooden supports or from rafts and longlines (Camacho et al. 1991, Morse & Rice 2010, Hurlburt & Hurlburt 1975. For bottom cultures, seed is collected from the benthos by dredging, an environmentally controversial method of harvest (Smaal 2002, Dolmer et al. 2012. ...
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A critical aspect of blue mussel (Mytilus edulis L.) aquaculture is industry dependence on a highly variable supply of wild seed. The objective of this study was to investigate responses of cultured pediveligers of blue mussels to different types of rope collectors. The study consisted of two trials in which competent larvae (approximately 5,000 per experimental tank-400 L) were exposed to rope collectors (polyethylene and polypropylene) exhibiting diverse structural features such as long loops, short loops, long filaments, short filaments, and smooth (Trial I-four rope types; Trial II-five rope types). In Trial I, rope segments (3 cm long) were placed at two different levels in four culture tanks (top and bottom of water column). In Trial II, segments were placed in the middle of the water column in six culture tanks. After 5 days, rope collectors were removed from experimental tanks and the number of settled larvae on each segment was counted. Rope collectors with the highest structural complexity/greatest surface area (long loops) elicited the strongest settlement response (highest densities) of mussel larvae, whereas those with the lowest complexity/least surface area (smooth) elicited the weakest response. Position within tank (top versus bottom; Trial I) had no significant effect on settlement density. Hatchery-reared mussel seed could be a reliable alternative to wild seed, and ropes with complex features should be used as larval collectors as they enhance settlement density which, in turn, could reduce production costs.
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The United States is the top seafood importer in the world. Nevertheless, opportunities to expand national seafood production, such as offshore aquaculture, are restricted by unclear frameworks for licensing, permitting and regulating new enterprises. Currently, domestic mussel demand is reliant upon international trade but demand could be met by aquaculture within the Exclusive Economic Zone (EEZ), especially in suitable areas off the northeast coast. With national public seafood preferences pointing towards the need for a larger mussel farming industry, science-based efforts to develop offshore farming will contribute to local economies and domestic supply of high-quality, traceable seafood. Beyond a scientific foundation, perceptions that offshore farming represents environmental and privatization threats instead of a national economic development and sustainable opportunity, will have to be addressed. The situation will only change when managers decide to include offshore aquaculture as one of the many legitimate activities for New England’s ocean waters, so that spatial planning can be done and conservation measures and offshore farming develop in tandem.
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Experimental measurements and numerical simulations are carried out to determine the hydrodynamics induced by suspended canopies of limited width and height for canopies with six different densities and canopy element arrangements and two different upstream velocities. Measurements of velocity are obtained using acoustic Doppler velocimetry and the drag force via a load cell. Numerical simulation results using OpenFOAM agree very well with the experimental data and are used to investigate the generated flow fields in detail. The bulk features of the flow are similar to those of other canopies, including emergent and submerged canopies, but the finite dimensions of the canopy results in flow patterns that differ from suspended canopies of essentially infinite width. The detailed hydrodynamics of the flow are controlled by the blockage of the suspended canopy which depends both on the canopy density and the lateral spacing between consecutive longitudinal rows of canopy elements. Increased flow blockage results in increases in the drag coefficient from 0.72 to 1.4, reduction in the flow rate inside the canopy from 58 to 98 % (of the diverted flow, 20–43 % is diverted below the canopy) and increases in the steady wake zone length from 0.6 to 4 times the canopy length. Flow blockage has relatively little effect on the length of the upstream adjustment and total wake zones at 1.09 and 7 times the canopy length respectively. The flow also depends only weakly on the upstream velocity.
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ABsTRACr Pea crabs living within the mantle cavities ofa variety ofbivalve hosts have several adverse effects. In blue mussels (Mytilus edulis L.), the crab Pinnotheres maculatus (Say) steals food strands and causes gil lesions. We studied the long-term stress of P. maculatus on its host by measuring shell accretion in the field, and by numerically characterizing shell shape. Shell form in M. edulis is presumed to reflect environmental and physiological history. We computed growth increments in infested populations of mussels over a three-month period at two sites with high and low nutrient regimes. When growth was measured by change in shell length, significant differences between mussels with and without large pea crabs occurred at the low nutrient site, but not where mussels enjoyed a high nutrient regime. To integrate very long-term disparity in growth rates associated with infestation, we used mussels from a robust, naturally occurring population. We recorded and analyzed mussel sithouette shapes with a video digitizer. Elliptic Fourier approximation completely characterized the two-dimensional outlines of shells in such a way that the allometric dependence of shape variables on shell size could be easily removed. At this evidently favorable site, infested mussels displayed significant shell shape distortion characteristic of reduced growth rates. Thus, even in apparently benign environments, pea crab infestation appears to be a chronic stress to M. edulis.
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Standard accounting procedures in ecological energetics would approach the carrying capacity problem by attempting to quantify gross energy needs of a cultivated population and comparing these with “available” energy (seston) flow through the culture area. Inability to distinguish between “available” and “utilizable” particles is only one of several difficulties encountered in formulating energy budgets for large-scale cultivation in natural waters, however. A model based on maintaining critical levels of particle flow through culture areas is offered as an alternative. This approach reduces the problem to terms which are easier to obtain than those involved in equations of energy flow. Application of the model depends on a priori knowledge that seasonal patterns in seston composition and other environmental conditions are conducive to growth of the cultivated species.
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The reproductive condition of seven latitudinally separated populations of the mussel Myti!us edu!is on the east coast of the United States was determined using histological analysis and stereology. Differences in the timing of various phases of the gametogenic cycle among populations did not have any discernible latitudinal trend. Two populations at the same latitude on Long Island, N. Y. had the greatest temporal differences observed in gametogenic cycle, with summer reproduction maxima separated by a 3-month interval. There was no difference in the water temperature regime between these two habitats and thus the rate of gametogenic development was not a constant function of temperature. The observed differences in the gametogenic cycle were attributed to temporal and quantitative differences between habitats in the energy content of the mussel's food supply.