Truthfully, I have no idea. Some mussels have one pearl; some are much larger, and so they have many up to 28-30 in a single shell. Below are the links to a large mussel, and my personal favorite mussels because of the large pearl size.

https://www.amazon.com/dp/B077ZPZV3B/ref=cm_sw_r_apan_glt_i_GDZZQG5QAE6WJ9TGHB0H?_encoding=UTF8&psc=1

https://www.amazon.com/dp/B095HC7H3W/ref=cm_sw_r_apan_glt_i_J05J1XKRHRVR4G7RAQYX?_encoding=UTF8&psc=1