Four species of oysters
Four species of oysters, from top to bottom: Virginica, Pacific, Kumamoto, Olympia. Source.

Many of us have heard that oysters are an important part of our ecosystem, but many do not know why, or how to help protect them! In the Puget Sound we have two primary oyster species: the native Olympia oyster, and the non-native Pacific oyster, which was brought over from Japan. When identifying between them, there are some key differences to look out for. Pacific oysters often grow to be much larger than their Olympia counterparts, up to 12 inches, have much more ridged shells, and are white to gray colored with new growth often being purple. Olympia oysters are small, up to 3.5 inches, have much more round/oval shells, a gray exterior, and a white or iridescent green interior. (Source)

Due to overharvesting, water pollution, habitat loss, and competition from the Pacific Oyster, our native Olympia oysters populations crashed many decades ago and have failed to recover. One of the goals of many wildlife agencies, and this lab, is to help restore Olympia oyster populations.

Let’s take a brief look at why we want to sustain our oyster populations:

  1. Oysters are natural water filters. Adult oysters filter up to 2.5 gallons of water per hour, which improves water quality. (Source)
  2. Oysters build reefs, which provide habitat for fish, shrimp, crabs, and other animals.
  3. Oyster reefs are natural breakwaters (a barrier built in body of water to protect a coast or harbor from the force of waves). These breakwaters protect shorelines and control erosion.
  4. The shellfish industry is present in 12 of the 39 counties in Washington state, provides over 2,000 jobs, and brings an estimated $184 million to Washington’s economy. (Source)
  5. Many people think oysters taste yummy and would like to keep eating them!

So why are shells specifically so important? When an oyster larva is around 2-3 weeks old, they must attach themselves to a hard substrate. Their ideal substrate is an oyster shell, living or dead. If no suitable substrate exists, the oyster settles on less desirable material or dies. Intense harvesting and population decline has impacted oyster abundance. Worldwide, shellfish reefs have a reported loss of 85% (Source). Therefore, we’ve seen reduced availability in prime oyster real-estate for the larvae.

You may now be wondering; what is being done about all this? Where do I fit in? On the East Coast, many organizations dedicated to shellfish restoration have teamed up with restaurants to take their empty oyster shells for recycling. Normally these shells would end up in a landfill. Now, the shells are carefully collected and cured for several months by experts to ensure there is no risk of contamination. Then, the shells are placed into designated areas along the coast to build oyster reefs back up. Recycling these oyster shells back into the ocean is an easy and very important way to ensure that oyster beds can form and yield a new generation of oysters in the future.

As for us non-experts, to reduce possible contamination, live oysters purchased at the store, markets, or restaurants, should never be placed back into the water, but instead composted. Washington shellfish harvest rules state that when harvesting oysters on the beach, you have to shuck them and leave the shells in place. Always remember to bring a container to put the meat in, and never take the shells with you! These are easy practices that all shellfish eaters and harvesters can do to help keep our oyster populations alive and well at sustainable levels.

Oyster Sustainability
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