R-08-01 Growth and long-term abundance patterns of the bloodworm (Glycera dibranchiate)

William Ambrose, Jr.
Bates College
Lewiston, ME 04240
207.786.6114
wambrose@abacus.bates.edu

Commercial harvesting of bloodworms (Glycera dibranchiata) supports about 1,000 licensed diggers and 48 licensed dealers, making it the fifth-largest wild fishery in Maine.
The effects of bloodworm harvest on other species in the mudflat, and on the mudflat itself, are not known. In areas where clams and bloodworms live side by side, digging for bloodworms disturbs habitat and can injure or kill neighboring clams.

In a previous Sea Grant-funded project (R-06-01), Ambrose and his colleague Curtis Bohlen documented patterns of bloodworm digging on heavily dug flats in midcoast Maine, using a combination of aerial photography and GIS to quantify the frequency and timing of digging. The study showed that bloodworm density on intertidal flats varies independently of harvesting pressure, and bloodworm size has not changed significantly over several decades Bloodworm harvesting does not significantly increase clam mortality, so both species can be harvested on the same flat. The preliminary data suggest growth may be much faster than previously thought and may, in part, explain why the bloodworm fishery generally returns consistently strong landings year after year despite heavy harvest pressure.

In this current project, Ambrose and Bohlen are quantifying bloodworm growth, developing a series of Catch Per Unit (CPU) effort based on data from worm dealers in midcoast and downeast Maine, and extend the record of bloodworm abundance at the Wiscasset Conservation Area back to the 1960s.

The investment of Sea Grant funds in Ambrose’s research through program development and competitive research awards has supported the most recent and robust scientific inquiry into the bloodworm,  providing fundamental information about the peculiarities of this intertidal organism and the fishery that depends on it. These findings may help in the implementation of management strategies and harvest practices that ensure successful bloodworm and soft-shell clam fisheries, while minimizing the long-standing conflicts between the fisheries.

2-year project, 2008-2010
Total Sea Grant funds: $49,728