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Dive Dry with Dr. Bill

#686: Mussel Beach

I apologize to my lady readers if you thought this week's column might be about steroid-ridden weight lifters working out on the sand at Venice Beach. Of course you do deserve a little excitement, too... but you'll just have to get it some other way today because I'm going to talk about mussels of a different sort. Yep, mussels as in bivalves rather than muscle as in beefcake.

I remember when mussels would give a girl a thrill. Back in Chicago I dated a lovely lady whose favorite appetizer was steamed common or blue mussels of the species Mytilus edulis and a glass (or three) of wine. Ah, those were the days. Even in my Toyon years here on the island we would sometimes harvest a bunch of California mussels (Mytilus californianus) and Marge Lewis, the school nurse, would cook them up.

For my more enlightened readers, you may realize that I'm back on the track of the group of molluscs known as bivalves. You know, the ones like clams and scallops with two shells. And I'm sure most of you also know that these critters can be quite tasty. Why on my very first Catalina dive at Arrow Point on August 24, 1969, i was offered a piece of rock scallop sushi while still underwater.

Out of patriotism I'll focus on our very own California mussel in this column. Actually it is not found just in our State, but can be seen in waters from northern Mexico to the Aleutian Islands in Alaska. They are generally seen in large aggregations in the upper intertidal region along open coasts exposed to surf. We don't see many on the protected leeward side of the island, but they are usually quite common at places like Shark Harbor on the windward side.

Due to their exposure to strong surf, their shells are usually somewhat thick with coarse ribbing. The exterior of the shell is dark blue with a heavy brown protein-based periostracum that is often partially worn away. This layer is secreted from a gland in the mussel's body and it hardens through a process similar to tanning.

The brown periostracum is very important in ensuring the mussel's shell develops properly. It helps seal off the growth region of the shell. It also provides a structural framework for the deposition and crystallization of the calcium carbonate shell. This layer is also found in many kinds of molluscs including other bivalves and gastropods (snails). The interior of the shell is a light blue in color and like the surface of a pearl.

Given their existence in high energy environments, the mussel needs a secure point of attachment to the rocky substrate. To achieve this they secrete a very strong, elastic thread (or series of them) known as a byssus. To initiate attachment they create a vacuum like region above the rock and secrete a mix of different proteins including keratin, polyphenolic proteins and others. It then curls its food into a tube and forces the mixture through it to create the thread-like structure. Another protein is then added to crate the adhesive.

Like most bivalves, mussels are filter feeders. They draw currents of water into the shell and extract the oxygen and plankton food from it, then expel the wastes out. In turn mussels are a favorite food of predators such as the knobby and ochre sea stars (starfish to the non-PC crowd). Large fish like sheephead, octopus and lobster will also eat them. You can often tell what predator was involved by looking at the bite marks or drill holes on the shell.

Now it wasn't just my girlfriend Sarah in Chicago that loved mussels. The Native peoples in our region harvested them for thousands of years. Some archaeologists believe they have detected periods of overharvesting of this resource. Today they are still harvested for food and for bait. I love them in ciopinno my at The Lobster Trap or El Galleon.

However, be careful if you're going to chow down on them. During periods of red tide they may concentrate harmful levels of toxins associated with paralytic shellfish poisoning (PSP). These toxins come from some of the tiny planktonic algae they filter out. Unlike some toxins, heat from cooking does not denature them and render them harmless. You don't want your dessert to be interrupted by a painful trip to the hospital... or death!

© 2016 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Mass of mussels on rocky reef and exterior of shells; interior of shell and the munchables inside.

This document maintained by Dr. Bill Bushing.
Material and images © 2015 Star Thrower Educational Multimedia