Measuring the impact of pollution closures on commercial shellfish harvest: The case of soft-shell clams in Machias Bay, Maine

Temporary closures of polluted coastal waters to shellfish harvesting protect human health but also generate broad socioeconomic impacts on rural, fishing-dependent communities. Improved understanding of these impacts could help coastal managers prioritize investments to protect water quality and mitigate the effects of coastal pollution. Using a regression model of monthly landings, we explore the impact of temporary closures on the commercial harvest of soft-shell clams (Mya arenaria) in the Machias Bay region of Maine (USA). We find that economic losses are significant and depend heavily on tidal activity, and the size, frequency and timing of closures. Over the nine-year sample period (2001-2009), temporary pollution closures contributed to the loss of $3.6 million in forgone revenue (2014 dollars), approximately 27.4% of total revenue. Closures linked to combined sewer overflows from the Machias wastewater system produce the majority of these losses ($2.0 million) with the largest occurring during the peak clamming season (May-August). Our results highlight the variability of the impacts of closures and the information burden for efficient management of shellfish areas and coastal waters. By strategically reducing pollution, managers could limit public health risks, avoid destabilizing harvesting and revenue, and bolster the resilience of fishing communities.