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Gulf Watch Alaska Nearshore Component: Sea Otter Aerial Survey Data Kenai Fjords National Park, 2002-2016

September 18, 2017

These data are is part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. Specifically, these data describe sea otter (Enhydra lutris) aerial survey observations from the waters around Kenai Fjords National Park between 2002 and 2016. Sea otters are a keystone predator, well known for structuring the nearshore marine ecosystem through their consumption of invertebrate prey. The dataset consists of 3 comma delimited files exported from Microsoft Excel. The data consists of 1. Strip transect counts, 2. Intensive Search Unit (ISU) counts, and 3. Transect coordinates. For each aerial survey, a pilot flew an airplane at an altitude of 91m over pre-determined transects while an observer searched on one side of the plane and recorded sea otter group counts and locations. Sea otters observed within 400 m of each transect were later used to estimate abundance. Sea otters sighted beyond the confines of designated transect swaths were also counted and mapped, time permitting. To estimate the number of sea otters in small groups (<20) not detected along transect swaths (e.g., due to diving behavior or the presence of kelp canopy), 400m diameter circles (i.e. ISUs) were searched intensively by periodically flying 5 concentric circles around an initiating group. These ISUs were distributed throughout the survey area in an attempt to accurately represent the full range of observation conditions encountered during the survey. When large groups of sea otters (≥20) were sighted on transect, they were circled until a complete count was made.