Downeast Institute and nine partner communities have established a Clam Recruitment Monitoring Network that spans the coast of Maine. This network measures soft-shell clam and other shellfish recruitment and survival, at two flats in each of nine- twelve towns from Wells in southern Maine to Sipayik (at Pleasant Point) in eastern Maine.
DEI’s Network partners include the Wells Shellfish Committee, Scarborough Shellfish Conservation Commission, Brunswick Marine Resources Committee, Phippsburg Shellfish Commission, Wiscasset Shellfish Conservation Committee, Bremen Shellfish Conservation Committee, Islesboro Shellfish Conservation Committee, Deer Isle & Stonington Shellfish Committee, Frenchmen’s Bay Regional Shellfish Committee, Beals Shellfish Committee, the Unorganized Township of Edmunds, and the Natural Resources Board of the Passamaquoddy at Sipayik. Clammers, municipal officials, students, and community volunteers work with DEI researchers to collect soft-shell clam recruitment and survival data.
Clam Recruitment is Measured by Using a Simple Tool
At each of the eighteen sites, an array of 16 recruitment boxes is deployed in the lower mid intertidal gradient. The boxes are deployed prior to soft-shell clam spawning season and sediment core samples are taken to assess baseline densities of clams. Boxes are retrieved at the end of the clam growing season in November, and sediment core samples from outside the boxes are collected again. These samples from the adjacent unprotected mud, compared to samples from the box, reveal the rate of predator success that season.
May 2020 Baseline Clam Survey Results
In May of 2020, DEI scientists, along with community members, conducted clam surveys in the each of the areas where the clam recruitment monitoring stations were deployed in order to establish baseline densities of clams and their sizes.
The results of the survey, along with information about the Soft-Shell Clam Recruitment Monitoring Network, can be found in Technical Report #1: 2020 Spring Baseline Clam Survey Results. Click on the report to the left to read it.
2020 Clam Recruitment Monitoring Network Final Report
Results from the 2020 Clam Recruitment Monitoring Network can be found in the Technical Report #2: Clam Recruitment Monitoring Results. The report summarizes and shares data from the fall mudflat survey, information about clam recruitment, temperatures, clam recruit growth, and presence and size of green crabs on a town and statewide basis.
Across the coast, clam recruitment densities were lower than expected based on data from previous years. Eight of the eighteen sites had average clam densities of less than 10 clams per sq. ft. Only three sites recorded average clam recruit densities of over 100 clams per sq. ft. (Winnock Neck in Scarborough, Dobbins Island in Beals, and Gleason Cove in Sipayik). At Gleason Cove we found a single recruitment box with 4,331 recruits, the second highest number of clams ever recorded in a single box. Gleason Cove received more than 1,000 recruits per sq. ft.
2021 Clam Recruitment Monitoring Network Final Report
Results from the 2021 Clam Recruitment Monitoring Network can be found in the upcoming Technical Report #3: Clam Recruitment Monitoring Results. The report summarizes and shares data from the fall mudflat survey, information about clam recruitment, temperatures, clam recruit growth, recruitment and growth of other commercially important shellfish species, along with presence and size of green crabs on a town and statewide basis.
Across all sites average clam recruitment density in 2021 was substantially lower than it was in 2020. Last year we found only 19 clams per square ft. in our predator protected boxes vs. 95 clams per square ft. in 2020. The low number of recruits found was likely due to higher numbers of green crabs. In 2021 there were 4.5 green crabs per square ft. across all 21 sites, while in 2020 we found only 2 crabs on average across all 18 sites.
From 2020-2021 this project was funded by Maine Sea Grant. Luke’s Lobster Keeper Fund supported the work of documenting recruitment and growth of other commercial shellfish species. In 2022, funding is provided by Maine Economic Improvement Fund Small Campus Initiative and Maine Outdoor Heritage Fund.