Marine mammal observations were recorded along-track from the northern Bering Sea (175.21 W, 62.01 N) northward to Barrow Canyon at the boundary of the Chukchi and Beaufort Seas (158.46 W, 71.62 N) aboard R/V Sir Wilfrid Laurier, during a July, 2015 research cruise. Observations include individual mammal species identification and counts, ice-cover percent, sea state, visibility and weather. Marine Mammal Watch observations were made as part of the Distributed Biological Observatory (DBO) to more systematically track the broad biological response to sea ice retreat and associated environmental change. The spatially-explicit DBO network, five regional biological "hotspot" locations along a latitudinal gradient, is organized through the Pacific Arctic Group (PAG), an international collaboration sanctioned by the International Arctic Science Committee.