Exploring the effects of winter harvesting closures for Northern Quahogs (Mercernaria mercenaria)

Town: Freeport, ME

Watershed: Concord Gully

Project type: Restoration

Organism of focus: Northern Quahog


Jessica Joyce- Project Manager

Charles Tetreau- Marine Resource Officer

Project Timeline

  • April 2019 – DMR permits and approval

  • May 6th, 2019

    Project was sited and quahogs were transplanted

  • July 10th, 2019

    The first survey was conducted in two plots, determining the success of the quahog transplant and survival

  • October 16th, 2019

    The second survey was conducted in two plots, determining the success of the quahog transplant and survival

  • January 22, 2020

    Winter disturbance of 10 plots

  • May 14, 2020

    Dig out remaining plots to count and asses quahog condition

additional Information

The Town of Freeport, along with many other shellfish communities, have increased their dependence on the quahog fishery, particularly as soft-shell clam populations have declined. In the context of these declines, quahogs provide an important source of income for harvesters. Scientific research highlights that quahogs are sensitive to cold temperatures and it has been observed anecdotally that winter harvesting closures may increase local populations of quahogs. With the growing interest in quahogs in Maine, this study presents initial insights into the topic.

This group focused on determining if digging during freezing temperatures had an effect on quahog mortality, thus exploring the effectiveness of winter harvesting closures on a municipal level. To do this, the group established a study area in Staples Cove in Freeport, Maine. The objectives of this study include: 1) assess feasibility of transplanting quahogs within the same cove; 2) understand the implications of this work among local harvesters, and local and state shellfish managers; 3) generate preliminary field data on mortality of quahogs from winter disturbance at a single site; and 4) test field methodology to refine for potential future studies with larger scale and geographic scope.

As this was a small-scale pilot study in one site, a need exists for larger studies in other locations of the state to help determine if these findings are consistent. Additionally, COVID-19 delayed the final field work in spring of 2020, so it is unknown whether leaving the quahogs in the study site for an additional month affected the results. Within this test site, this study observed that quahogs that were undisturbed (i.e., left alone in the mud) survive at a higher rate than those that were disturbed (i.e., dug and brought to the surface) during the winter. As a secondary finding, Staples Cove had a moderate success rate for transplanted quahogs of various sizes during the first six months.

For more information about this project, please see the executive summary.