Sep 16, 2009: Oyster Culture

Farm work Oysters

Here are the oysters spawning earlier this summer:

spawn1

And now here are their babies!

oysterset

The black specks on this shell are miniature oysters, called spat. We'll leave this cluster out on the beach for about 3 to 5 years so it can grow into a cluster of big guys.

Oyster farmers in the Hood Canal are lucky to be able to farm wild oysters. A "farmed but still wild" operation challenges a bunch of assumptions that we don't need to explore on in this post... just know that it's a really beautiful way to grow food. We basically work to make our beach more habitable for the things we want to eat, like some kind of aquatic food forest.

The trick to catching baby oysters is to give them something to latch onto... during a baby oyster's metamorphose from zooplankton to a sedentary animal, it's attracted to oyster shell (a solid evolutionary trick for finding tried-and-true oyster habitat).

Through the ages and across the world, farmers have used various materials to entice oysters to their beach... sticks, rocks, etc. Oyster shell works best, of course, but if you don't have shell you can use something similar. On a recent vacation in Vietnam, one of our own found oyster farmers there using slate roofing tiles as substrate for oyster culture. In the mid-50s to early 60s, when our oyster farm was first getting established, oyster shell was scarce, so we used concrete to mimic the chemical composition of oyster shell. We dipped lath in concrete and used these stakes to collect larvae. After about a year, we could knock off the concrete, breaking the oysters apart into clusters and singles.

My beautiful picture

As soon as we had enough shells (starting in the the late 60s and throughout the 70s, 80s, and early 90s) we suspended bags of oyster shell (called cultch) from floating racks out in the middle of the Canal. Deploying the "seed racks" was a pretty big undertaking, one that took the whole family. It was a fun (albeit dangerous!) job on sunny August afternoons. Here are the racks up on shore:

My beautiful picture

My beautiful picture

And here they are floating out in the water:

My beautiful picture

In the late 90s, the permitting for the seed racks got pretty complicated and we decided we'd rather not use so much styrofoam. Since then we've gone back to basics: in the springtime we bag shell up into cultch bags (we try to get this done before the Oyster Rama, and then we use the cultch bags for our Rama fence) and when the oysters spawn in July or August, we put pallets of cultch bags out on the beach in hopes they'll attract larvae at high tide.

cultchbags

Sometimes this works. But nothing's a given! Sometimes the wind picks up during the larval period, drops the water temperature, and everything dies. Here are year old oysters growing on cultch bags:

cultchoysters

And here's a 5 to 7 year old oyster cluster, the end result of this process:

cluster

Since Hood Canal has such a prolific wild oyster population, Canal farmers were a little slow to embrace hatchery seed. Why pay for something you get for free? Of course, using seed produces a much higher quality product for the half shell market, more reliable in shape, size, and appearance. And for the past 6 years or so the wild oysters really haven't reproduced in the Canal, so we've had to scramble to get our seed operations up and running. The lack of a natural set may be normal (we did have a big set in 2012) or it may be related to ocean acidification... the Canal has seen some of the lowest pH ever recorded on earth. To learn more about how to grow oysters from seed, read this post.

oysterseed


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