Secrets Uncovered by the Oyster Shell

Maybe I'm just an oyster nerd, but I am totally fascinated by the shells. Once upon a time, many months ago, I had some oysters at The John Dory Oyster Bar. After finishing the lot, I began to wonder...

Why do the Hama Hamas have barnacles stuck to them? Where do the stripes on the Hog Island Sweetwater come from? What made that hole in the Peconic Bay? Playing detective not your cup of tea? Well, here are some reasons why you should consider the oyster shell...

They can help you differentiate different East and West coast oysters very quickly. Practical application: No one is going to pull a fast one and serve you the wrong oyster!

They can provide context for the oyster's flavor and texture. Practical application: This will help you appreciate the flavors even more, which brings you one slurp closer to connoisseur-dom.

They are unusual, interesting, and natural conversation starters. Practical application: Being able to explain why the shell is the way it is will come in handy on dates.

A Study of Shells

An array of oyster shells

After doing some research by speaking to oyster farmers and aquaculture experts, I began to solve these peculiar mysteries. Here's are some shell deciphering basics...

Oyster Shell Shapes Explained

The shape of the oyster depends on the species, how fast it grows, and how much space its been given to grow. Confirmed by Lissa James of Hama Hama Company, an oyster's growth rate is a function of water temperature and food availability. The more warped, stretched or "rabbit eared" the oyster appears, the less growing space was involved. Or it could be oddball genetics. In some cases, it might be indicative of a "wild" oyster, where its appearance isn't meticulously managed.

In general, Eastern oysters or Virginicas, tend to be teardrop shaped. European oysters such as the Belon are round and flat like saucers. The Pacific oyster, or the Gigas, tend to be guitar-pick shaped, intricately fluted along its fringe, and (watch out) jaggedly sharp. John Finger of Hog Island Oyster Farm also noted that some oysters such as the Kumamoto and Kusshi are intentionally manicured via tumbling, which results in a strong, smooth, deeply cupped shell.

If you look closely at the shell, you'll notice that it's slightly tiered. The oyster builds its shell gradually, layer by layer, by extracting calcium carbonate (lime) from the water. It uses its mantle, the delicate band of tissue along the outside of its body, to produce the protective shell. The oyster grows its shell the fastest during warm seasons when it has plenty of food. Once the temperature drops below a certain point, they halt all growth and go into hibernation mode. The distinctive bands around the shell mark when the oyster halted its shell production.

Oyster Shell Colors Explained

The two major factors that impact color are: minerals or nutrients in the water and growing location. Genetics also can affect the patterns, intensity or frequency of color that an oyster produces. The Hama Hama Oyster Blog has an intriguing post about this, and Lissa swears that the more colorful and fluted Hama Hamas are, the better they taste!

According to Aquaculture Specialist Gregg Rivarra from the Cornell University Cooperative Extension of Suffolk County, a green tinge signifies an oyster that has been growing near the surface—probably teaming with algae. Orange tints found on the Peconic Bays may be attributed to a high concentration of iron in the water. The brightness of an oyster may depend on its growing conditions, but it may also be a result of intentional grooming. Some oysters are cleaned and brightened by pressure washing before they hit the premium market.

Other Curious Marks on Oyster Shells

You typically won't encounter severe abnormalities at restaurants, but every oyster bar has its day! Chipped shells are a sign that they are brittle (weak composition, prone to breaking). Oysters that live easy lives (e.g., no tumbling, little exposure to open air, resides in warmer waters) will often have weaker shells than those that have endured the elements.

Barnacles tend to appear on beach-grown oysters, such as the Hama Hamas. Oysters are actually a great foundation for other sea critters to settle on. Barnacles are one of the most common attachments, but seaweed or rocks can also appear.

Holes are created by critters such as boring sponges (lots of little holes), oyster drills (one small round hole), and moon snails (beveled hole).

So the next time when you slurp an oyster down, turn the shell around and have a look!