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The inland waters of Washington State are inhabited regularly by 10 species of marine mammals. Updated and comprehensive information regarding marine mammal occurrence, distribution, and behavior in the area is critical when addressing local anthropogenic impact, management, and conservation concerns. We conducted a total of 16,198 km of observation effort during systematic line-transect surveys from a high-wing, twin-engine airplane throughout Puget Sound in all 4 seasons during 2013 to 2016, and in the Strait of Juan de Fuca and San Juan Islands area during summer 2014 and spring 2015. Ten marine mammal species were confirmed across 5772 groups of an estimated 10,673 individuals sighted, including some seasonal patterns of occurrence. The most commonly sighted species in terms of individuals were Harbor Seals (n = 8012), Harbor Porpoises (n = 2168), California Sea Lions (n = 238) and Steller Sea Lions (n = 77). The most common behavior states documented across species among the total 5670 groups were rest (73%) and medium travel (16%); probable foraging was observed among 13 groups (0.2%) and included Gray Whale foraging pits in tidal mudflats. Potential behavioral reactions to the aircraft were rare (0.3% of total individuals), primarily by Harbor Seals and Harbor Porpoises. Results of these surveys represent the most comprehensive up-to-date information available on marine mammal occurrence, distribution, and behavior across seasons in the Puget Sound region. [ABSTRACT FROM AUTHOR]

The estuaries and tidal rivers of the Gulf of Maine have rarely been surveyed systematically for marine mammals. We report here on three years of survey data, 2017 to 2019. This study employed a shipboard visual line-transect methodology study design, collecting data on marine mammals in the lower Piscataqua River, which is confluent with the Gulf of Maine. Marine mammal species observed most often were harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus), with a resulting in-water density estimate of 1.02 seals/km2 and an abundance estimate of seven harbor seals and one gray seal (CV = 19.3%) in the survey area. Seals were present in all months of the year. No live pups were detected. Harbor porpoises (Phocoena pho-coena) and minke whales (Balaenoptera acuto-rostrata) were also observed, but the sightings (6 harbor porpoises; 7 minke whales) did not yield enough data to estimate density or abundance. The minke whales were present during August and September 2018, concurrent with an influx of Atlantic menhaden (Brevoortia tyrannus), a prey species. The consistent albeit relatively low marine mammal species sightings and abundances suggest that the lower Piscataqua River is used regularly by a relatively small number of harbor and gray seals, although not for pupping, and occasionally by harbor porpoises and by foraging minke whales. This is the first study of its kind in an estuarine environment in the Gulf of Maine. [ABSTRACT FROM AUTHOR]