Blue mussel, common blue mussel, bay mussel • Mytilus trossulus, M. edulis, and M. galloprovincialis
Heiltsuk/Haíɫzaqv - k̓vás • Nuxalk - smiks
Left: blue mussels (and barnacles) attached to rocks in a sheltered intertidal area of Calvert Island. Photo by Joel White. Right: blue mussels under attack by six ray stars (Leptasterias hexactis). Photo by Jessica Brown.
Identification
Blue mussels have smooth, shiny shells that are usually blue to black or occasionally brown to tan. The shells have little erosion of the outer layer (the periostracum), smooth growth lines, and no major radiating lines running lengthwise. Their shells are usually less than 7 cm long, though they may grow up to 11 cm. The shell shape is somewhat pointed at the anterior (narrower) end, and rounded at the posterior (wider) end.
There are 3 species of Mytilus found on the BC coast that are visually indistinguishable: M. edulis, M. trossulus, and M. galloprovincialis. They are differentiated using genetic testing, and were determined to be separate species only relatively recently. To complicate matters, these species have all hybridized in the Pacific Northwest. Researchers therefore often consider the “Mytilus edulis/trossolus/galloprovincialis species complex” rather than a single species.
Habitat & Range
Blue mussels can be found throughout the intertidal in calm, sheltered locations. They often forms dominant mats that cover the underlying substrate completely. They use their strong byssal threads to attach to rocks, docks, pilings, and other solid substrates. Their range off the west coast of North America extends from northern Alaska to northern Mexico. The ranges of the three species appear to overlap and hybridization occurs, though there appears to be a general pattern of M. trossulus occuring in more northern areas along the coast and M. galloprovincialis in more southern locations. Exact ranges of the three species are unknown - however whether native or introduced, one or more of these species is present along most coastlines throughout the world. See Cowles (2005), ISSG (2006), ARKive.org, and Riginos and Cunningham (2005) for some further range information.
Similar Species
Aside from the M. trossulus/edulis/galloprovincialis confusion, the other main mussel species found on the BC coast is the California mussel (Mytlius californianus). It is usually larger, with thicker and more eroded shells marked by strong radial lines. It is also found in more exposed locations, as compared to the sheltered areas preferred by blue mussels.
Human uses
All three species are edible. M. edulis is widely grown in commercial aquaculture productions; M. galloprovincialis is also grown in some regions of the world, especially in China and Japan. Both are longer lived than M. trossolus, and so are better suited to aquaculture.
Intruiging Info
M. trossulus appears to be native to the Pacific Northwest, while M. edulis and M. galloprovincialis seem to be introduced. M. galloprovincialis, also known as the Mediterranean blue mussel, is native to the Mediterranean coast and the Black and Adriatic Seas. It has spread to locations around the globe through ballast water and through its use in aquaculture. It is listed by the Global Invasive Species Database as one of the 100 world's worst invaders.
M. edulis is likely introduced to the Pacific Northwest and originally from the Atlantic Ocean, however the difficulty in differentiating these species and their extensive use in aquaculture creates difficulty in understanding the native and introduced range of M. edulis.
iNaturalist
https://www.inaturalist.org/taxa/130239-Mytilus-trossulus
https://www.inaturalist.org/taxa/117650-Mytilus-edulis
https://www.inaturalist.org/taxa/81648-Mytilus-galloprovincialis
Blue mussels have smooth, shiny shells that are usually blue to black or occasionally brown to tan. The shells have little erosion of the outer layer (the periostracum), smooth growth lines, and no major radiating lines running lengthwise. Their shells are usually less than 7 cm long, though they may grow up to 11 cm. The shell shape is somewhat pointed at the anterior (narrower) end, and rounded at the posterior (wider) end.
There are 3 species of Mytilus found on the BC coast that are visually indistinguishable: M. edulis, M. trossulus, and M. galloprovincialis. They are differentiated using genetic testing, and were determined to be separate species only relatively recently. To complicate matters, these species have all hybridized in the Pacific Northwest. Researchers therefore often consider the “Mytilus edulis/trossolus/galloprovincialis species complex” rather than a single species.
Habitat & Range
Blue mussels can be found throughout the intertidal in calm, sheltered locations. They often forms dominant mats that cover the underlying substrate completely. They use their strong byssal threads to attach to rocks, docks, pilings, and other solid substrates. Their range off the west coast of North America extends from northern Alaska to northern Mexico. The ranges of the three species appear to overlap and hybridization occurs, though there appears to be a general pattern of M. trossulus occuring in more northern areas along the coast and M. galloprovincialis in more southern locations. Exact ranges of the three species are unknown - however whether native or introduced, one or more of these species is present along most coastlines throughout the world. See Cowles (2005), ISSG (2006), ARKive.org, and Riginos and Cunningham (2005) for some further range information.
Similar Species
Aside from the M. trossulus/edulis/galloprovincialis confusion, the other main mussel species found on the BC coast is the California mussel (Mytlius californianus). It is usually larger, with thicker and more eroded shells marked by strong radial lines. It is also found in more exposed locations, as compared to the sheltered areas preferred by blue mussels.
Human uses
All three species are edible. M. edulis is widely grown in commercial aquaculture productions; M. galloprovincialis is also grown in some regions of the world, especially in China and Japan. Both are longer lived than M. trossolus, and so are better suited to aquaculture.
Intruiging Info
M. trossulus appears to be native to the Pacific Northwest, while M. edulis and M. galloprovincialis seem to be introduced. M. galloprovincialis, also known as the Mediterranean blue mussel, is native to the Mediterranean coast and the Black and Adriatic Seas. It has spread to locations around the globe through ballast water and through its use in aquaculture. It is listed by the Global Invasive Species Database as one of the 100 world's worst invaders.
M. edulis is likely introduced to the Pacific Northwest and originally from the Atlantic Ocean, however the difficulty in differentiating these species and their extensive use in aquaculture creates difficulty in understanding the native and introduced range of M. edulis.
iNaturalist
https://www.inaturalist.org/taxa/130239-Mytilus-trossulus
https://www.inaturalist.org/taxa/117650-Mytilus-edulis
https://www.inaturalist.org/taxa/81648-Mytilus-galloprovincialis
References
Cowles, D. (2005). Mytilus trossulus Gould, 1850.Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 06/08/2014.
Harbo, R. M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 89.
Invasive Species Specialist Group (ISSG). (2006). Mytilus galloprovincialis (mollusc). Global Invasive Species Database. IUCN Species Survival Commission. Accessed 06/08/2014.
Mytilus trossulus Gould, 1850. In Klinkenberg, Brian. (Ed.). E-Flora BC: Electronic Atlas of the Plants of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 06/08/2014.
Authors and editors of page
Joel White, Kelly Fretwell, and Brian Starzomski (2014).
Cowles, D. (2005). Mytilus trossulus Gould, 1850.Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 06/08/2014.
Harbo, R. M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 89.
Invasive Species Specialist Group (ISSG). (2006). Mytilus galloprovincialis (mollusc). Global Invasive Species Database. IUCN Species Survival Commission. Accessed 06/08/2014.
Mytilus trossulus Gould, 1850. In Klinkenberg, Brian. (Ed.). E-Flora BC: Electronic Atlas of the Plants of British Columbia. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. Accessed 06/08/2014.
Authors and editors of page
Joel White, Kelly Fretwell, and Brian Starzomski (2014).