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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
months, a few occasionally range into the Beaufort Sea in late summer Mymrin et al. 1990; Garlich-Miller and Jay 2000; USFWS 2017. Industry monitoring reports have observed no more than 38 walruses in the Beaufort Sea ITR geographic region between 1995
and 2015, with only a few instances of disturbance to those walruses AES
Alaska 2015, Kalxdorff and Bridges 2003, USFWS unpubl. data. The USGS
and the Alaska Department of Fish and Game ADF&G have fitted between 30
60 walruses with satellite transmitters each year during spring and summer since 2008 and 2013 respectively. In 2014, a female tagged by ADF&G spent about 3 weeks in Harrison Bay, Beaufort Sea ADF&G 2014. The USGS tracking data indicates that at least one tagged walrus ventured into the Beaufort Sea for brief periods in all years except 2011. Most of these movements extend northeast of Utqiagvik to the continental shelf edge north of Smith Bay USGS
2015. All available information indicates that few walruses currently enter the Beaufort Sea and those that do, spend little time there. The Service and USGS are conducting multiyear studies on the walrus population to investigate movements and habitat use patterns, as it is possible that as sea-ice diminishes in the Chukchi Sea beyond the 5-year period of this rule, walrus distribution and habitat use may change.
Walruses are generally found in waters of 100 m 328 ft or less where they utilize sea-ice for passive transportation and rest over feeding areas, avoid predators, and birth and nurse their young Fay 1982; Ray et al.
2006; Rosen 2020. The diet of walruses consists primarily of benthic invertebrates, most notably mollusks Class Bivalvia and marine worms Class Polychaeta Fay 1982; Fay 1985;
Bowen and Siniff 1999; Born et al. 2003;
Dehn et al. 2007; Sheffield and Grebmeier 2009; Maniscalco et al. 2020.
When foraging, walruses are capable of diving to great depths with most dives lasting between 5 and 10 minutes with a 12-minute surface interval Fay 1982;
Bowen and Siniff 1999; Born et al. 2003;
Dehn et al. 2007; Sheffield and Grebmeier 2009. The foraging activity of walruses is thought to have a significant influence on the ecology of the Bering and Chukchi Seas by disturbing the sea floor, thereby releasing nutrients into the water column that provide food for scavenger organisms and contributing to the diversity of the benthic community Oliver et al. 1983; Klaus et al. 1990; Ray et al. 2006. In addition to feeding on benthic invertebrates, native hunters
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have also reported incidences of walruses preying on seals, fish, and other vertebrates Fay 1982; Sheffield and Grebmeier 2009; Seymour et al.
2014.
Walruses are social and gregarious animals that often travel and haul-out onto ice or land in groups where they spend approximately 2030 percent of their time out of the water Gilbert 1999;
Kastelien 2002; Jefferson et al. 2008;
Monson et al. 2013; USFWS 2017.
Hauled-out walruses tend to be in close physical contact, with groups ranging from a few animals up to tens of thousands of individualsthe largest aggregations occurring at land haul-outs Gilbert 1999; Monson et al. 2013;
MacCracken 2017. In recent years, the barrier islands north of Point Lay, Alaska, have held large aggregations of walruses 20,00040,000 in late summer and fall Monson et al. 2013;
USFWS 2017.
The size of the walrus population has never been known with certainty. Based on large sustained harvests in the 18th and 19th centuries, Fay 1957
speculated that the pre-exploitation population was represented by a minimum of 200,000 animals. Since that time, population size following European contact fluctuated markedly in response to varying levels of human exploitation. Large-scale commercial harvests are thought to have reduced the population to 50,000100,000 animals in the mid-1950s Fay et al. 1989.
Following the implementation of harvest regulations in the 1960s and 1970s, which limited the take of females, the population increased rapidly and likely reached or exceeded the food-based carrying capacity of the region by 1980 Fay et al. 1989, Fay et al. 1997, Garlich-Miller et al. 2006, MacCracken et al. 2014.
Between 1975 and 1990, aerial surveys conducted jointly by the United States and Russia at 5-year intervals produced population estimates ranging from about 200,000 to 255,000
individuals with large confidence intervals Fay 1957; Fay 1982;
Speckman et al. 2011. Efforts to survey the walrus population were suspended by both countries after 1990 following problems with survey methods that severely limited their utility. In 2006, the United States and Russia conducted another joint aerial survey in the pack ice of the Bering Sea using thermal imaging systems to more accurately count walruses hauled out on sea-ice and applied satellite transmitters to account for walruses in the water Speckman et al. 2011. In 2013, the Service began a genetic mark-recapture study to estimate population size. An
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initial analysis of data in the period 20132015 led to the most recent estimate of 283,213 Pacific walruses with a 95% confidence interval of 93,000 to 478,975 individuals Beatty 2017. Although this is the most recent estimate of Pacific walrus population size, it should be used with caution as it is preliminary.
Taylor and Udevitz 2015 used data from five aerial surveys and with shipbased age and sex composition counts that occurred in 19811984, 1998, and 1999 Citta et al. 2014 in a Bayesian integrated population model to estimate population trends and vital rates in the period 19752006. They recalculated the 19751990 aerial survey estimates based on a lognormal distribution for inclusion in their model. Their results generally agreed with the large-scale population trends identified by Citta et al. 2014 but with slightly different population estimates in some years along with more precise confidence intervals. Ultimately, Taylor and Udevitz 2015 concluded i that though their model provides improved clarity on past walrus population trends and vital rates, it cannot overcome the large uncertainties in the available population size data, and ii that the absolute size of the Pacific walrus population will continue to be speculative until accurate empirical estimation of the population size becomes feasible.
A detailed description of the Pacific walrus stock can be found in the Pacific Walrus Odobenus rosmarus divergens Species Status Assessment USFWS
2017. A digital copy of the Species Status Assessment is available at:
https ecos.fws.gov/ServCat/
DownloadFile/
132114?Reference=86869.
Polar bears are known to prey on walruses, particularly calves, and killer whales Orcinus orca have been known to take all age classes of walruses Frost et al. 1992, Melnikov and Zagrebin 2005; Rode et al. 2014; Truhkin and Simokon 2018. Predation rates are unknown but are thought to be highest near terrestrial haulout sites where large aggregations of walruses can be found;
however, few observations exist of predation upon walruses further offshore.
Walruses have been hunted by coastal Alaska Natives and native people of the Chukotka, Russian Federation, for thousands of years Fay et al. 1989.
Exploitation of the walrus population by Europeans has also occurred in varying degrees since the arrival of exploratory expeditions Fay et al. 1989.
Commercial harvest of walruses ceased in the United States in 1941, and sport
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