Friday, October 17, 2008
We had a great field trip at Hadley Point this week, where we helped with a student project on clams and collected all manner of worms to look at back in class. More on the worms in a later post. First, we helped Sarah census her baby clams to see if soft-shelled clams, Mya arenaria, exhibit enhanced recruitment in her two treatments (raked and brushed) compared to control plots. Raking roughens the bottom while "brushing," in which small branches of spruce trees are stuck into the mud, provides structure that affects water flow, which may increase the likelihood that clam larvae that are ready to settle out of the plankton encounter the bottom. Using sections of 6 inch PVC pipe to collect core samples, students scooped out the mud and counted all the little clams they found in the sample. I'm hoping Sarah will present her results to the class soon and will also comment here in the blog. Adequate recruitment is only the first step in maintaining a population that's able to be harvested sustainably. Subsequent predation on the baby clams before they reach harvestable size is also an important factor, and some resource managers will seed clam flats with babies from hatcheries or elsewhere, thus ensuring there are plenty of individuals there to start with, and then protect those flats with netting to exclude predators. That's an approach used here on MDI, in Southwest Harbor. Soft-shelled clams are an important component of Maine's fishing industry, although their importance is dwarfed by the commercial lobster fishery. To find out more about Maine's fisheries, including both recreational and commercial, check out the Department of Marine Resources website.