Shellfish harvesting is a large part of our sea island lifestyle.
It brings the community together over meals, to bond and appreciate our natural resources. Oysters, clams and ribbed mussels are the major players when it comes to our non-summer harvests.
The Atlantic ribbed mussel, Geukensia demissa, is the most common mussel species in our area. They are also known as the horse-mussel. These bivalves live within the inter-tidal zone, the space between the high and low tide lines. They can be found partially buried in our pluff mud, found among oyster reefs or attached to pilings and other hard substrates. Their natural habitat is found along the Atlantic and Gulf Coasts.
Ribbed mussels are oval shaped, named for the prominent ribs running down their shell.
They have a narrow blunt head that tapers to their connective joint. They are glossy, ranging from olive-brown to olive-black. At times you may be able to find patches of white or yellow on the outside of their shells. The interior of their shell ranges in highly glossy purple hues. During breeding season you can identify males from females by taking a look at the interior soft tissue that encloses the body. Females will be a medium brown tone, while males will be a yellow or cream color.
Adult ribbed mussels have been known to live up to 15 years. On average they will reach lengths of up to 10 inches. You can identify the age of a mussel by counting the ribs on the outside of the shell. They will reach their maturity at 12 millimeters. Spawning occurs once a year, usually between June and September. Eggs and sperm are released into the water column, where fertilization takes place. It is thought that only 55 percent of larvae will make it through their first year. This is due to severe cold water temperature and freezing in shallow estuaries.
Ribbed mussels are filter feeders.
When the tide is high, they will suck water into their shells, where their gills will then remove plankton and algae for the mussel to consume. A single mussel can filter 6.8 liters of water each hour when submerged. If a mussel is covered by water for 12 hours a day, that means they are filtering almost 22 gallons of water each day, per mussel.
Warmer water creates more bacteria and thus could be a danger for human consumption. Harvesting season usually occurs in any month with an “R” in it. It is also important to harvest ribbed mussels at a high tide, when their valves continuously open and close. During a low tide, the mussel closes its valve and retains water in its body for the duration of the low tide. By keeping water inside of itself, it is also keeping waste products that can be toxic to human consumption.
By Kathleen McMenamin, Master Naturalist