Hayden Cook, Fisheries Intern
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Posted on July 18, 2012 | Permalink
Clam Shell Experiment for Spat
Location: Deal Island
Thursday I went to Deal Island with three members of the Shellfish Program: Frank Marenghi, Maude Livings, and Eric Weissberger. Ten days earlier two bushels of both oyster and clam shells were evenly spread on the bottom of a huge tank. The tank was approximately five feet in diameter and five feet tall. All the shells in the tank were placed in quarters kind of like a pizza, the oyster shells were across from each other and the clam shells were across each other all coming to a point in the middle. Then staff from the University of Maryland oyster hatchery would come and put spat in the tank with the shells. The point of this experiment is to figure out if spat will settle on clam shells and start to grow, either at the same rate of oyster shells or maybe better by counting the amount of spat on both the oyster and clam shells. There is not an unlimited supply of oyster shells for oyster projects in the Bay, and clam shells are a lot more abundant and cheaper to buy from nearby states.
The process for this experiment was to first drain the water (which came directly from a Bay tributary next to the tanks), spray the oysters with a hose (oysters had brown muddy sediments and algae on them), then Maude got in the tank an scooped out the oysters. We couldn't count the spat on all of the shells (there were too many), so we took out four nine-liter buckets of oyster and clam shells to count from each tank. The rest of the shells were put in oyster cages and placed in the water off the dock. When fall comes around, the Shellfish Program will go back out and see if the spat on the shells survived to become young oysters. Back to the experiment: Maude and I had to clean the tank while Eric and Frank started to count spat. Once we finished cleaning, after about twenty minutes, Eric and Frank had only counted about two liters of oyster shells (itís safe to say counting spat was going to take a lot longer than we expected). Now with three counters and me recording the number of spat, it took about a half hour to count the spat on nine liters of shell. That sounds fast but only two buckets were counted like that and each shell had many spat on it, sometimes over a hundred. Counting the spat in one bucket of oyster shells would take one person more than one hour. There was still one more tank that needed the same process. We also had to refill the tanks with new oyster and clam shells for a second round of trials. With the first tank taking four of us about five hours, we decided to get the second tank ready and come back another day to count the spat.
From what I noticed about the first tank, the experiment was so far a success. There was the same or maybe more spat on the clam shells than oyster shells. If the second round of the experiment shows the same result, DNR and the public will know that clam shells are a good alternative to oyster shells. This will cheapen the cost of projects and for oyster farmers, and also relieve some of the demand for oyster shells.