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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations vicinity of industrial infrastructure and not be noticed by humans. These unnoticed bears may also experience Level B harassment. To determine whether our calculated encounter rate should be corrected for unnoticed bears, we compared our encounter rates to Wilson et al.s 2017 weekly average polar bear estimates along the northern coast of Alaska and the South Beaufort Sea.
Wilson et al.s weekly average estimate of polar bears across the coast was informed by aerial surveys conducted by the Service in the period 20002014 and supplemented by daily counts of polar bears in three highdensity barrier islands Cross, Barter, and Cooper Islands. Using a Bayesian hierarchical model, the authors estimated 140 polar bears would be along the coastline each week between the months of August and October.
These estimates were further partitioned into 10 equally sized grids along the coast. Grids 47 overlap the SBS ITR
area, and all three encompass several industrial facilities. Grid 6 was
estimated to account for 25 percent of the weekly bear estimate 35 bears;
however, 25 percent of the bears in grid 6 were located on Cross Island. Grids 5
and 7 were estimated to contain seven bears each, weekly. Using raw aerial survey data, we calculated the number of bears per km of surveyed mainland and number of bears per km of surveyed barrier islands for each Service aerial survey from 2010 through 2014 to determine the proportion of bears on barrier islands versus the mainland. On average, 1.7 percent, 7.2 percent, and 14
percent of bears were sighted on the mainland in grids 5, 6, and 7, respectively.
While linked encounter records in the LOA database were removed in earlier formatting, it is possible that a single bear may be the focus of multiple encounter records, particularly if the bear moves between facilities operated by different entities. To minimize repeated sightings, we designated a single industrial infrastructure location in each grid: Oliktok Point in grid 5, West Beach in grid 6, and Point
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Thomsons CP in grid 7. These locations were determined in earlier analyses to have constant 24-occupancy; thus, if a polar bear were within the viewing area of these facilities, it must be reported as a condition of each entitys LOA.
Polygons of each facility were buffered by 1.6 km 1 mi to account for the industrial viewing area see above, and then clipped by a 400-m 0.25-mi buffer around the shoreline to account for the area in which observers were able to reliably detect polar bears in the Services aerial surveys i.e., the specific area to which the Wilson et al.s model predictions applied. Industrial encounters within this area were used to generate the average weekly number of polar bears from August through October. Finally, we divided these numbers by area to generate average weekly bears/km2 and multiplied this number by the total coastal Service aerial survey area. The results are summarized in the table below Table 3.

TABLE 3COMPARISON OF POLAR BEAR ENCOUNTERS TO NUMBER OF POLAR BEARS PROJECTED BY WILSON ET AL.
2017 AT DESIGNATED POINT LOCATIONS ON THE COAST OF THE NORTH SLOPE OF ALASKA
Grid 5
Total coastline viewing area km2
Industry viewing area km2
Proportion of coastline area viewed by point location
Average number of bears encountered AugustOctober at point location
Number of weeks in analysis
Average weekly number of bears reported at point location
Average weekly number of bears projected in grid
Average weekly number of bears projected for point location

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These comparisons show a greater number of industrial sightings than would be estimated by the Wilson et al.
2017 model. There are several potential explanations for higher industrial encounters than projected by model results. Polar bears may be attracted to industrial infrastructure, the encounters documented may be multiple sightings of the same bear, or specifically for the Point Thomson location, higher numbers of polar bears may be
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travelling past the pad to the Kaktovik whale carcass piles. However, because the number of polar bears estimated within the point locations is lower than the average number of industrial sightings, these findings cannot be used to create a correction factor for industrial encounter rate. To date, the data needed to create such a correction factor i.e., spatially explicit polar bear densities across the North Slope have not been generated.

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34
0.31
0.009
3.2
13
0.246
7 0.064

Grid 6
45
0.49
0.011
4.6
13
0.354
26
0.283

Grid 7
33.4
1.0
0.030
28.8
13
2.215
7 0.210

Estimated Harassment We estimated Level B harassment using the spatio-temporally specific encounter rates and temporally specific take rates derived above in conjunction with AOGA supplied spatially and temporally specific data. Table 4
provides the definition for each variable used in the take formulas.

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