In 2001, Canadian imports provided 78.6% of all U.S. Blue mussel sales by volume, most of this product coming from Prince Edward Island (Lanteigne 2002). The rest of the Blue mussels in the U.S. market are farmed or wild-caught in Maine and to a lesser extent, Washington (NMFS 2004). Off-bottom culture is far more common than on-bottom farming in the United States (Seafood Business 2002). In Canada, all commercial Blue mussels are farmed using longline suspended culture systems (DFO 2003b; Preston, pers. comm. 2004). Suspension culture is typically used because harvest-per-area is much larger, predation is generally lower, and mussels tend to grow faster (Gosling 1992; DFO 2003b).

Depending on location, off-bottom systems utilize poles (known as “bouchets”), stakes, ropes and lines to catch and/or grow out seeds (Batten 2004; Gosling 1992).

In the U.S., many farms employ a raft culture system. Great Eastern Mussels Farm (GEM) Inc., the largest Blue mussel producer in the U.S., uses on-bottom and raft systems (Shumway, pers. comm. 2004). The rafts are comprised of foam floats, steel and wood timbers, and anchored in place. Each raft is 40' x 40', with four hundred 45’ long ropes seeded and hung to each raft. The seeded ropes are left to hang off of the raft for 12 to 18 months before harvesting (GEM 2004). Farmers sometimes use mesh tubes to hold the mussels together (GEM 2004; Seafood Business 2002).

Farmers in Canada culture Blue mussels instead on “longlines,” which consist of two large buoys spread hundreds of feet from each other, attached by a line, with many lines hanging from this main line (Preston, pers. comm. 2004).

Part of what makes Blue mussels such a good candidate for aquaculture is that they often grow at very high densities in the wild, and therefore their cultivation at high densities does not cause significant environmental impact. As an example of density, GEM reports yields of about 15,000 pounds per acre (GEM 2004). Blue mussels grow to about 4 inches long (Batten 2004), with a market size beginning at 2.25 inches (Gosling 1992).

However, density may be used to manipulate the populations in different ways. During the grow-out phase of their cultivation, Blue mussels may be re-seeded in order to lower the density, thereby increasing the rate of growth. Alternatively, some farmers may intentionally overcrowd the mussels in order to slow growth to extend the season during which market-sized product is available (Gosling 1992).

We neither add nor subtract here, because although Blue mussels are raised at high densities, there is no evidence of environmental impact.

Controls on farm locations vary by state, region, and often by locality. In Maine, where most of the farms in the U.S. are located, the Department of Marine Resources grants aquaculture leases for up to 10 years and up to 200 acres per lease. Lease proposals are subject to an adjudicatory hearing, which considers the impact of an aquaculture operation on navigation, fishing, access for riparian owners and coastal zoning statutes. Some environmental impacts that are taken into consideration are: displacement of rooted or attached marine vegetation, alteration of current flow, increased rates of sedimentation or sediment resuspension and disruption of fish migration (Maine DMR 2003). As of May 1997, there were 6 mussel leases in Maine that covered a total area of 154.5 acres. This was way down from 32 leases over 696 acres in 1986 (Maine DMR 2004).

In Canada, the provinces and territories are responsible for the majority of site approvals and for overseeing the industry’s day-to-day operations. The federal role involves such areas as research, technology transfer, training and development, access to financing and environmental sustainability relating to the industry. Federal regulations are applied by a number of departments, including Fisheries and Oceans Canada (DFO), Agriculture and Agri-Food Canada, Environment Canada, Health Canada, and by bodies such as the Pest Management Regulatory Agency, the Canadian Food Inspection Agency and others (DFO 2004). The regulations require that sites undergo environmental assessments, under the Canadian Environmental Assessment Act (CEAA), are accessed for the possibility of a harmful alteration, disruption or destruction (HADD) of fish habitat under section 35 of the Fisheries Act, or interfere with native rights and land claims, migratory birds, utilization by other groups, and shellfish food safety (DFO 2004). Both U.S. and Canadian permitting practices thoroughly consider adverse effects of siting.

Absolutely no feed is used to farm Blue mussels. Unlike other mollusks, there is no hatchery phase (Gosling 1992), during which algae may be added to seawater as feed for larvae. Mussels are suspension feeders and compared to other mollusks, they are the most efficient feeders. They feed by actively filtering particles from the water, which passes into and out of the mantle cavity through the frilled siphons. Living and dead phytoplankton constitute the main source of food (DFO 2003b). Mussels filter 10-15 gallons of water a day (Batten 2004).

No feed is used (Preston 2004).

No feed is used (Preston 2004).

No feed is used (Preston 2004).

Treatment is not necessary, because supplemental feed is not used.

Mussels themselves improve water quality by filtering out algae and other plankton, reducing chlorophyll, nutrient and suspended solid levels (Downey, pers. comm. 2004).

Chemicals are never used (Preston 2004).

While shellfish do not negatively impact water quality, there are consumption concerns if they are raised in poor quality water. Both the U.S. and Canada have managing agencies that address this issue. In the U.S., The National Shellfish Sanitation Program (NSSP) coordinates water quality standards. State and local agencies responsible for fisheries management must comply with NSSP regulations (Kraeuter and Castagna 2001). These agencies are responsible for issuing permits, overseeing leasing of beds, exercising control over uncertified areas, monitoring water quality and classifying areas along NSSP guidelines.

Canada has implemented the Canadian Shellfish Sanitation Program (CSSP), which is jointly administered by DFO, the Canadian Food Inspection Agency (CFIA) and Environment Canada. The CSSP’s primary objective is to protect the public from the consumption of contaminated shellfish by ensuring that bivalve shellfish are harvested from waters of acceptable sanitary quality. Growing areas are classified based on the sanitary and bacteriological water quality conditions of the area and the classifications categories are “approved,” “conditionally approved” (quality varies), and “closed” (DFO 2003b; DFO-CSSP 2004).

Blue mussels are filter feeders. Therefore, farming this species does not create waste (Downey, pers. comm. 2004).

Blue mussels are distributed worldwide in most polar and temperate waters (Batten 2004). Operations in Canada and the United States are within their native range and pose minimal risk to native populations and ecosystems.

This farmed species is a native mollusc.

No concerns have been raised to date over the impact of Mytilus edulis establishment. As seed is collected from within or nearby the sites where they are farmed, their genetics are the same, and interbreeding between escaped and wild individuals does not compromise the genetic integrity of wild population.

Incidence of disease is low.

Blue mussels do not have any major disease problems (Gosling 1992). Also, there tend to be fewer problems with disease in suspension culture systems than in bottom cultures. However, there are several types of human illnesses caused by marine biotoxins that are connected with the consumption of contaminated bivalve shellfish. They include Paralytic Shellfish Poisoning (PSP), Amnesic Shellfish Poisoning (ASP), and Diarrhetic Shellfish Poisoning (DSP). The toxins are named for the most notable symptom they cause, i.e., paralysis, amnesia and diarrhea, respectively.

In the U.S., The National Shellfish Sanitation Program (NSSP) oversees the transfer of live shellfish (spat or full grown individuals) between states (Kraeuter and Castagna 2001). The Canadian Shellfish Sanitation Program (CSSP) closely follows NSSP guidelines, and also regulates transfer of shellfish to help prevent invasions of non-native species and disease problems(DFO-CSSP 2004).

Blue mussels are raised in sheltered coastal areas of the intertidal and subtidal zones. They are frequently raised in partially enclosed embayments (Gosling 1992).

Farmers using a raft system may hang nets from the four sides of the rafts to protect their mussels from birds. In Maine, the major predator on these systems are Eider ducks, which eat seed that has set on adult mussels, and cause the mussels to fall off of the lines. The nets are made of fine mesh and are heavily weighted, and there have been no entanglement problems (Preston, pers. comm. 2004).

Farmers collect seed from the wild. Spat can be collected on a variety of substrates, such as old rope, Italian socking material, nylon bags, fuzz rope, artificial seaweed, and mesh. Whatever the material used, the collectors are usually hung on the lines just before the spat are expected to settle in the summer (DFO 2003b). Some farms use a special machine specifically made for wrapping the seed on the ropes. The mussel seed is placed in a hopper on top, and then the empty rope is fed into the machine. The mussel seed and rope are then wrapped with biodegradable cotton to hold the mussels in place. Seeding takes place primarily in the spring and fall of the year (GEM 2004). In response to concern over overharvesting of seed, the Maine Department of Natural Resources established four "seed mussel conservation areas", from which only seed-size mussels may be removed for growout. A permit issued by the Department of Marine Resources is required to remove any mussels from the conservation areas. The mussel regulation defines seed mussels and their use, describes the seed mussel conservation areas, establishes size limits of mussel drags, and prohibits nighttime harvesting (Maine DNR 2004). We added points here, because concern about overcollecting wild spat is being addressed, and there is no evidence of wild mussel populations suffering great decline (Shumway, pers. comm. 2004).