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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Notices
on their behalf collectively industry operators, in Federal waters of the U.S. Gulf of Mexico GOM over the course of 5 years 86 FR 5322; January 19, 2021. The rule was based on our findings that the total taking from the specified activities over the five-year period will have a negligible impact on the affected species or stocks of marine mammals and will not have an unmitigable adverse impact on the availability of those species or stocks for subsistence uses. The rule became effective on April 19, 2021.
Our regulations at 50 CFR 217.180 et seq. allow for the issuance of LOAs to industry operators for the incidental take of marine mammals during geophysical survey activities and prescribe the permissible methods of taking and other means of effecting the least practicable adverse impact on marine mammal species or stocks and their habitat often referred to as mitigation, as well as requirements pertaining to the monitoring and reporting of such taking. Under 50 CFR
217.186e, issuance of an LOA shall be based on a determination that the level of taking will be consistent with the findings made for the total taking allowable under these regulations and a determination that the amount of take authorized under the LOA is of no more than small numbers.
Summary of Request and Analysis Fugro plans to conduct a 3D UltraUltra High Resolution 3DUUHR
seismic survey in the Mississippi Canyon Block 20 using two sparkers and a multibeam echosounder. The objective of the 3DUUHR survey is to provide targeted subsurface data in the vicinity of the well bay where gas in the shallow section can be seen to attenuate high frequency sub bottom data. Please see Fugros application for additional detail.
Consistent with the preamble to the final rule, the survey effort proposed by Fugro in its LOA request was used to develop LOA-specific take estimates based on the acoustic exposure modeling results described in the preamble 86 FR 5322, 5398; January 19, 2021. In order to generate the appropriate take number for
authorization, the following information was considered: 1 Survey type; 2
location by modeling zone 1; 3
number of days; and 4 season.2 The acoustic exposure modeling performed in support of the rule provides 24-hour exposure estimates for each species, specific to each modeled survey type in each zone and season.
Exposure modeling results were generated using the single airgun proxy.
Because those results assume use of a 90-in3 airgun, the take numbers authorized through this LOA are considered conservative i.e., they likely overestimate take due to differences in the sound source planned for use by Fugro, as compared to those modeled for the rule. The survey is planned to occur for 10 days in Zone 5 during the winter, which provides the basis for the take estimation.
In this case, use of the exposure modeling produces results that are substantially smaller than average GOM
group sizes for multiple species 3 i.e., estimated exposure values are less than 10 percent of assumed average group size for the majority of species MazeFoley and Mullin, 2006. NMFS typical practice in such a situation is to increase exposure estimates to the assumed average group size for a species in order to ensure that, if the species is encountered, exposures will not exceed the authorized take number. However, other relevant considerations here lead to a determination that increasing the estimated exposures to average group sizes would likely lead to an overestimate of actual potential take. In this circumstance, the very short survey duration and relatively small Level B
harassment isopleths produced through use of the sparker compared with an airgun array mean that it is unlikely that certain species would be encountered at all, much less that the encounter would result in exposure of a greater number of individuals than is estimated through use of the exposure modeling results. As a result, in this case NMFS has not increased the estimated exposure values to assumed average group sizes in authorizing take.
Based on the results of our analysis, NMFS has determined that the level of
taking expected for this survey and authorized through the LOA is consistent with the findings made for the total taking allowable under the regulations. See Table 1 in this document and Table 9 of the rule 86 FR
5322; January 19, 2021.
Small Numbers Determination Under the GOM rule, NMFS may not authorize incidental take of marine mammals in an LOA if it will exceed small numbers. In short, when an acceptable estimate of the individual marine mammals taken is available, if the estimated number of individual animals taken is up to, but not greater than, one-third of the best available abundance estimate, NMFS will determine that the numbers of marine mammals taken of a species or stock are small. For more information please see NMFS discussion of the MMPAs small numbers requirement provided in the final rule 86 FR 5322, 5438; January 19, 2021.
The take numbers for authorization, which are determined as described above, are used by NMFS in making the necessary small numbers determinations, through comparison with the best available abundance estimates see discussion at 86 FR 5322, 5391; January 19, 2021. For this comparison, NMFS approach is to use the maximum theoretical population, determined through review of current stock abundance reports SAR;
www.fisheries.noaa.gov/national/
marine-mammal-protection/marinemammal-stock-assessments and modelpredicted abundance information https seamap.env.duke.edu/models/
Duke/GOM/. For the latter, for taxa where a density surface model could be produced, we use the maximum mean seasonal i.e., 3-month abundance prediction for purposes of comparison as a precautionary smoothing of monthto-month fluctuations and in consideration of a corresponding lack of data in the literature regarding seasonal distribution of marine mammals in the GOM. Information supporting the small numbers determinations is provided in Table 1.

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TABLE 1TAKE ANALYSIS
Authorized take 1

Species Rices whale 3
1 For purposes of acoustic exposure modeling, the GOM was divided into seven zones. Zone 1 is not included in the geographic scope of the rule.

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2 For purposes of acoustic exposure modeling, seasons include Winter DecemberMarch and Summer AprilNovember.
3 These species include: Bottlenose dolphins, short-finned pilot whales, Atlantic spotted dolphin,
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Abundance 2
0

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Percent abundance n/a
Clymene dolphin, false killer whale, Frasers dolphin, melon-headed whale, pantropical spotted dolphin, pygmy killer whale, Rissos dolphin, rough-toothed dolphin, spinner dolphin, striped dolphin.

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