INVESTIGATING THE 2018-2020 PINNIPED UNUSUAL MORTALITY EVENT ALONG THE NORTHEAST COAST THROUGH AERIAL SURVEY DATA

Abstract:

Beginning in July 2018, there has been an increased number of mortalities among harbor seal (Phoca vitulina) and gray seal (Halichoerus grypus) populations in the Northeast United States, which commenced the 2018-2020 Pinniped Unusual Mortality Event (UME). Necropsies that were conducted on the stranded or deceased seals revealed that the pathogen, Phocine Distemper Virus (PDV), was responsible for the mass strandings and mortalities. Additionally, mortality data shows that gray seals display a higher resilience to PDV than harbor seals. It is hypothesized that gray seals act as a vector of disease to harbor seals and accelerate transmission within the harbor seal population. The objective of this investigation was to determine areas of species mixing and high contact areas using aerial survey data. In November and December of 2018, aerial surveys were flown over the Northeast region. Using Adobe Photoshop and QGIS, population distributions will be compared to stranding data from the years of the UME. It is hypothesized that areas of species mixing and high contact populations will correspond with increased stranding cases. Understanding these trends will provide further insight into the transmission of PDV and enable a more educated and efficient response to future UMEs.