A map of the brushing study sites across the Maine coast. Map by Kaitlyn Raffier.

DEI scientists recently deployed studies across the Maine coast that will determine if the brushing method works to increase clam populations. This study marks the first time ever that this popular clam enhancement method has been tested to determine its effectiveness. The results will provide valuable information to clam managers about tools they can use to increase clam harvests and adapt the fishery to the changing marine ecosystem.

The studies are taking place in each of three regions of the Maine coast – Downeast, Midcoast, and Southwest, in the towns of Gouldsboro, Bremen, and Harpswell, respectively. DEI scientists are working directly with the town’s Shellfish Conservation Committees and clammers to deploy the experiments, as well as collect and process the data.

Brushing is the practice of inserting tree boughs into the mudflats. In concept, the brush reduces tidal and wind currents that help to create eddies providing bottom zones of slow-moving water where recently settled soft-shell clam juveniles may congregate.

The study deployed three sets of brush in each town, and will measure the amount of clams that settle and survive around the brush. In addition, at each location, three nets that protect clams from predators also were deployed. The number of clams that settle and survive in brushed areas will be compared to the number of clams that settle and survive in netted plots. This comparison will clarify the utility of the two methods and demonstrate to local shellfish managers the most effective method to increase clam populations.

Clammers and municipal staff were part of the crew that helped with the Harpswell experimental deployment.

During deployment DEI scientists took samples (n=108) of the mud to establish baseline densities of clams in each location. Clams were found in half the samples in Gouldsboro, 26% of the samples in Bremen, and 13% of the samples in Harpswell. The average density of clams in Gouldsboro was 3.4 clams per sq. ft., in Bremen the average density was 1.6 clams per sq. ft., and in Harpswell the average density was 0.6 clams per sq. ft.

The baseline survey results show that clam densities were highest in the eastern site, and decrease the further south the location. This finding correlates with previous field experiments DEI has done across the coast of Maine. Read more about the baseline survey results here.

The final results will be determined after sampling in November 2019.

To read more about the study design, click here.

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