I think the main thing with some areas with these mussels is that they take up valuable territory and spread faster than native species, in some areas that depend on the native species for food, I.E. Prince Edward Island Mussels, Maine, and the Pacific northwest, etc. people's livelihoods and whole local economies are at stake. The Zebra mussel is no good for food. Here is a cut and pasted description of said issue.
D. Jude, Center for Great Lakes Aquatic Sciences
Threat to Other Species
Zebra mussels are filter feeders. An adult zebra mussel filters up to a quart of water per day, which multiplied by millions of mussels means that the mussels may be filtering all the water in a lake or stream in a day. The animals and algae that are the food of zebra mussels are also the food for larval fish and other native species, so a large zebra mussel population may cause a decline in other animals, including native fish, mollusks, and birds. The filter-feeding activity of zebra mussels causes a related and frequently dramatic increase in water clarity in infested lakes and rivers.
Zebra mussels can severely effect native mussels and clams by interfering with their feeding, growth, movement, respiration, and reproduction. For example, zebra mussels can colonize a clam shell to such an extent that the clam cannot open its shell to eat. Some native mussels have been found with more than 10,000 zebra mussels attached to them. In addition to colonizing native mussels and clams, zebra mussels may attach to slow-moving species such as crayfish and turtles.
GLSGN Exotic Species Graphics Library Water and environmental management agencies are working to protect endangered native species from the threat of zebra mussels. The primary emphasis of this effort is to education so that boaters and fishermen do not inadvertently transfer mussel larvae from one water body to another. In some rivers, boaters are prohibited from traveling upstream from infected areas in an attempt to keep the mussels from spreading.
Zebra mussels do have a positive impact on some native species. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and sunfish. The increase in aquatic plants due to increased water clarity provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River. However, these native species do not feed heavily enough on zebra mussels to keep the populations under control.
Threat to Navigation, Boating, and Industry
In addition to the impact on wildlife, zebra mussels cause many problems for people. They may colonize water intake pipes, severely restricting the water flow to power plants or other municipal or private facilities that rely on fresh water. Impacts include damage to the facilities as well as the cost of removing or controlling the mussels. Zebra mussels may also foul beaches and create boating and navigation hazards. Increased plant growth provides an additional hazard to navigation.
Zebra mussels will attach to almost any hard surface, either natural or manmade. On boats, they may attach to the hull, motor, or any item immersed in the water. Both large and small boats can be severely impacted by increased drag caused by thousands of mussels. Small zebra mussels may get into engine cooling systems, causing overheating and other damage.
In addition to threatening boats, zebra mussels pose a threat to navigational buoys, piers, docks, and other structures in the water. Navigational buoys have been sunk under the weight of attached zebra mussels. Wood, steel, and concrete are all damaged by prolonged attachment of the mussels.
Threat to Outdoor Recreation
Shells of zebra mussels foul beaches and near-shore swimming areas. Bare feet are at risk from the sharp shells, and clean up costs are high. Due to changes in fish populations, zebra mussels also adversely impact recreational fishing.
I know I have no life for knowing this but they are a pretty nasty nuisance creature. But they are better than these damn Stinkbugs all over everything!