Black mussels at the Namibian coastline
Black mussels in Namibia include following species: Ribbed mussel (Aulacomya atra), Black mussel (Choromytilus meridionalis), Mediterranean mussel (Mytilus galloprovincialis), Brown mussel (Perna perna) and Bisexual mussel (Semimytilus algosus).
Black mussels are black or brown with a tinge of green or blue. They are enclosed by a pair of shell valves that are linked together by an elastic ligament. The flesh of females is orange and that of males is off-white.
They are not very mobile and attach themselves with a ‘beard’ of byssal threads to sand, rock, or wood. They are filter feeders, sucking water in through an inhalant siphon, sieving it through sheet-like gills, and expelling wastewater via an exhalant siphon.
Their sizes range, depending on the type of bivalve, between 40 – 150mm.
The flesh of all the above-mentioned bivalves is edible. It can be eaten raw but is tastier once steamed. Black mussels are also used for bait to catch Cob or Galjoen along the Namibian coastline.
Nutritionally, bivalves are an excellent source of omega-3 fatty acids, iron, selenium, zinc, and vitamin B12, which can be see from the article provided at this link.
Finding and harvesting
Black mussels grow on rocks in the intertidal zone. They are commonly hand-picked at low tide. They are normally harvested at a size of 6cm or bigger, as this is a good size for consumption.
The mussel flesh is larger and more flavoursome during winter when the water temperature drops to between 12-15⁰C.
Mussels may only be picked by hand, and no mechanised implements or tools may be used, therefore it is quite labour-intensive. Legally 50 mussels may be harvested per person.
Note: Black mussels are poisonous during plankton blooms as these filter-feeders ingest the toxins of such occurrences. Plankton blooms can be recognized by the reddish-brown color of the water. After about 3 clear days after a plankton bloom, mussels can be safely eaten.
Lessons learned from Black mussels
- Black mussels occur on rocks at the intertidal zone
- They are most flavorsome at wintertime in cold waters
- During plankton bloom, they are poisonous but can be safely eaten about 3 days after the bloom ends.
Branch G. M. et al (2016) Two Oceans: A guide to the marine life of Southern Africa 4th edn., Struik Nature.