Epizootic shell disease (ESD) is a significant concern to the southern New England lobster fishery. Although ESD has been reported in the southern Gulf of Maine off Massachusetts, there are few reports from Maine waters. We report on the occurrence and distribution of ESD in American lobsters from nearshore Gulf of Maine from the Maine Commercial Lobster Sea Sampling Program. Overall, average prevalence levels of ESD by trip were very low (\u3c0.16%) through 2010, then increased from 2011 to the present, reaching 1.2% in 2013. As with previous studies, recent prevalence levels in legal and sublegal (\u3c127 mm CL) animals were higher (6%–7%) in egg-bearing females than in males and non-ovigerous females. This pattern was amplified in oversized (\u3e127 mm CL) lobsters, regardless of sex and reproductive state, with much higher prevalence levels (up to 22%). Spatially, prevalence levels of ESD were significantly higher in western regions of the Gulf of Maine than off eastern Maine. Using histology and microbiome analyses, the etiology of the disease was investigated and common signs of lobsters with ESD were described. Aquimarina homari, a bacterium associated with ESD, was significantly more prevalent on lobsters with lesions and abundance was correlated with severity of ESD. Our report indicates that ESD is present on lobsters throughout the nearshore waters of the Gulf of Maine. Given the effect of the disease on lobsters from southern New England and its increasing prevalence over time, further monitoring of ESD in the Gulf of Maine is warranted
