Author: Chadwick V. Jay Publisher: ISBN: Category : Sea ice Languages : en Pages : 90
Book Description
A Bayesian network model was developed to analyze potential effects of changing environmental conditions and human-caused stressors on the future status of the Pacific walrus through the twenty-first century. This report was written to focus new research and monitoring efforts as well as to aid a review of walrus status that was prompted by the U.S. Fish and Wildlife Service in 2009 to determine if listing the subspecies as threatened or endangered is warranted under the Endangered Species Act. This government concern was raised due to climate warming and reductions in sea ice habitats.
Author: Tracie E. Merrill Publisher: ISBN: Category : Walrus Languages : en Pages : 196
Book Description
"With ongoing climate change, food resources may be reduced for Pacific walruses (Odobenus rosmarus divergens). Significant differences in walrus foraging habitat (benthic communities) or diet might indicate changes in prey quality or quantity. In this study, benthic infaunal biomass, abundance, and composition were compared between 1970-1974 and 2006 at stations southwest of St. Lawrence Island. Sediment grain size was compared because it strongly determines benthic community structure. Wet weights, counts, and species composition of prey items found in stomachs of walruses collected near the island were compared between the 1980s and 2007. Benthic invertebrate biomass and abundance increased mainly due to high Nuculidae biomass and abundance, although results may be skewed by low sample size. Silt fractions increased regionally. No significant dietary differences were detected in walruses. Walruses may have undergone a population redistribution or decline in response to benthic community changes that would be undetected in stomach content analyses"--Leaf iii.
Author: Patrick Maron Charapata Publisher: ISBN: Category : Walrus Languages : en Pages : 326
Book Description
The Pacific walrus (Odobenus rosmarus divergens) is an iconic Arctic marine mammal that Alaska Natives rely on as a subsistence, economic, and cultural resource. A decrease in critical sea ice habitat and uncertain population numbers have led to walruses being listed as a candidate for the Endangered Species Act. However, there is no clear understanding of how walruses might be affected by climate change. The first objective of this study was to describe how bone steroid hormone concentrations relate to commonly used blubber and serum steroid hormone concentrations (i.e., cortisol, estradiol, progesterone and testosterone), because steroid hormones have not been extracted from marine mammal bone until now. Bone, blubber, and serum were collected from individual adult walruses (n = 34) harvested by Native Alaskan subsistence hunters during 2014 and 2015. Complete turnover of cortical bone in a walrus skeleton was estimated as ~33 years, approximately the lifetime of a walrus. Results showed bone and blubber steroid hormone concentrations were similar (P = 0.96, 0.51, 0.27 for cortisol, estradiol, and progesterone (males only), respectively), but not testosterone (males and females, P = 0.003) nor progesterone in blubber of female walruses (P = 0.007). Progesterone concentrations in males were significantly correlated between bone and blubber (R2 = 0.51, P 0.001). Estradiol measured in bone had high interannual variability (P
Author: Jenell T. Larsen Tempel Publisher: ISBN: Category : Subsistence hunting Languages : en Pages : 260
Book Description
An interdisciplinary approach is used in understanding change and resiliency in St. Lawrence Island (SLI) resources and resource users throughout this dissertation. Historically SLI inhabitants have relied on the Pacific walrus (Odobenus rosmarus divergens) for their survival and this resource is still highly valued for cultural and dietary purposes. The responses of Pacific walruses and SLI subsistence users to environmental change was analyzed. In walruses, reproductive capacity was analyzed using an anatomical approach as well as reproductive plasticity which was determined using a physiological approach to characterize their estrus cycle. A suite of anatomical measurements were developed to characterize reproductive capacity of walruses by analyzing ovaries from three distinct time frames during a 35-year period. Reproductive capacity was reduced during time frames when carrying capacity (K) was reached and when large environmental changes occurred in the Bering Sea, including years of very low sea ice extent. Reproductive capacity was high in times when K was lower and harvest levels were greater. Our results explained how perturbations in K and environmental changes may have influenced reproductive capacity of the population in the past. Endocrine techniques were used in ovarian tissues to determine if progesterone and total estrogens are useful indicators of female reproductive status in walruses harvested during the spring hunt. Progesterone and total estrogen concentrations were greater in the reproductive tissues of unbred and pregnant females than postpartum females, however neither hormone could distinguish between pregnant and unbred animals. These results provide the first physiological evidence for pseudopregnancy in this species, rather than a postpartum estrus. Lastly, discussions were held with SLI community members to determine changes in key subsistence resources and community resiliency with regard to food security. Walruses ranked highest among key resources. Stakeholders reported limited access and increased effort to hunt walruses, changes in crab abundance, and increases in commercially exploitable fish stocks. Changes were attributed to loss of sea ice, “bad” weather, and climate change. In order for SLI communities to continue their subsistence-based way of life, inhabitants may need to expand their diet to include less-preferred food items in place of harvested ice-associated species. In conclusion, loss of sea ice and rapid environmental changes in the Bering Sea have the potential to greatly impact walrus reproduction and the marine subsistence way of life that is practiced by SLI stakeholders.
Author: U.S. Fish and Wildlife Service. Region 7. Marine Mammals Management Publisher: ISBN: Category : Marine mammal populations Languages : en Pages : 20
Author: Joseph R. Geraci Publisher: National Aquarium in Baltimore ISBN: 0977460908 Category : Marine mammals Languages : en Pages : 386
Book Description
Comprehensive manual for understanding and carrying out marine mammal rescue activities for stranded seals, manatees, dolphins, whales, or sea otters.
Author: Chadwick V. Jay
Author: Tracie E. Merrill
Author: 
Author: Patrick Maron Charapata
Author: U.S. Fish and Wildlife Service
Author: U.S. Fish and Wildlife Service
Author: Jenell T. Larsen Tempel
Author: James Spencer Taggart
Author: U.S. Fish and Wildlife Service. Region 7. Marine Mammals Management
Author: Joseph R. Geraci