Watershed = Foodshed

A couple of months ago we were invited to give a guest lecture at a University of Washington seminar about human interactions along the land/water interface.

One of the trippy things about oyster farming is how much you have to think about the surrounding environment... about what you, and your neighbors near and far, are doing to the waterways. Our farm has seen its fair share of human intervention, but it's relatively unique in that there are very few people living in the watershed, and no real industry upstream besides tree farming. Around the world, most oyster farmers have to contend with dams, cities, power plants, water treatment facilities, and animal waste.

One of the things we discussed in the seminar was how nutrients from the forest, brought by the river, can influence oyster flavor and algae growth. Oysters eat tiny bits of organic material and algae, and what they consume changes their flavor, growth rate, and health. 

Below are some photos we used as talking points. Left, you'll see a photo we took last May of the barge dumping a tub of oyster cultch on the beach. The interesting thing about it is how clear the water is, especially for mid-May. Our farmer hypothesis (unproven, untested) is that this is due to the drought. Normally in May, there's a ton of snowmelt running down the rivers on the Olympic Peninsula, bringing nutrients that fuel algae growth in the Canal. This May, the snow had already melted, river levels were super low, and the Canal was very clear (albeit a bit turquoise).

On the other extreme, sometimes it's very obvious that the Canal is full of algae. The photo below right is not a photo of "red tide," but rather a harmless dinoflagellate called noctiluca.

Algae is something we've been thinking a lot about this year, because for the first time ever, we did have a "red tide" on the Canal. It was invisible, and very scary, but we are fortunate to farm in a place with rigorous State testing, so we were able to stop harvesting before levels became harmful. Now the toxic algae is gone, but we're left wondering if it was caused by something in the river water (maybe lack of freshwater?) or, more likely, something from the ocean, maybe related to changing water chemistry.

Here are two photos of the river as it flows through our farm. The one on the left was taken late September 2012 after a series of fairly heavy fall rains muddied up the water a bit. The photo on the right was taken this May, when the water was quite a bit less cloudy.

Another thing we discussed: how geology influences an oyster's shape and life history. Oysters grown on gravel or sandy soil have different shapes than those grown on softer substrates. Our beach has lots of gravel: Hood Canal is a glacially-carved fjord, and when the glaciers receded they left behind piles of gravel. In the thousands of years since, the rivers have been moving the gravel out into the water, stone by stone. So there's lots of small cobble on the beach for oysters to attach to. Because of this, we've always gotten a fair number of naturally-recruited "pebble set" single shell oysters (see below). One of our tasks as farmers is to make sure there's substrate on the beach (gravel, or shell) to catch as many of these babies as possible.