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Gulf Watch Alaska Nearshore Component: Sea Otter Aerial Survey Data Katmai National Park and Preserve, 2008 - 2018 (ver 2.0, March 2020)

March 30, 2020

These data are 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 Katmai National Park and Preserve from surveys conducted in 2008, 2012, 2015, and 2018. 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 (CSV) 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 91 meters 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 meters 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 (less than 20) not detected along transect swaths (e.g., due to diving behavior or the presence of kelp canopy), 400 meter 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 (greater than or equal to 20) were sighted on transect, they were circled until a complete count was made. Data are presented as three CSV files: KATM sea otter strip transect counts in dd.csv, KATM sea otter ISU counts.csv, KATM sea otter survey transect coordinates in dd.csv