Assessment of the reproductive ecology of harbor seals (Phoca vitulina) and northern sea otters (Enhydra lutris kenyoni) in Alaska using subsistence biosampling programs

• Main Author: Hutchinson, Emily A.
• Other Authors: Atkinson, Shannon, Hoover-Miller, Anne, Kruse, Gordon, Wynne, Kate
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: Fairbanks; Gulf of Alaska; harbor seal; Phoca vitulina; Alaska
• Online Access: http://hdl.handle.net/11122/4655

Thesis (M.S.) University of Alaska Fairbanks, 2014. Harbor seals (Phoca vitulina) and northern sea otters (Enhydra lutris kenyoni) in Alaska have experienced extreme fluctuations in abundance in recent decades. The purpose of this study was to examine growth and determine the age and size at sexual maturity in populations of these two species, as spatial and temporal variations in environmental conditions and changes in ecological constraints as a result of population fluctuations can influence growth and reproductive characteristics of individuals. All samples for this research were collected via biosampling, the collection of measurements and biological tissue samples, as a component of subsistence harvesting by Alaska Natives. In Chapter 1, morphometric measurements and reproductive tracts were collected by the Alaska Native Harbor Seal Commission's Biosampling Program from female harbor seals harvested throughout the Gulf of Alaska from 1998 through 2005. Seals attained an asymptotic standard length (SE) of 147.7 ± 2.6 cm and body mass of 82.2 ± 4.8 kg. Female harbor seals did not mature until a minimum age of 3 yr, a standard length of 122 cm, and a weight of 48 kg. The average age of sexual maturity was 4.2 ± 0.7 yr (95% CI). Fetal growth was measured by standard length, curvilinear length, axillary girth, the cube root of fetal mass, skull length, condylobasal length, zygomatic width, and skull width against the day of the year the mother was harvested. The x-intercept of the linear regression of each fetal growth measurement against the day of the year produced estimates of the implantation date that ranged from September 22nd to October 17th, with a mean date of September 30th ± 8 d (SD). Harbor seals from this study are smaller in length, have a later implantation date, and are larger at sexual maturity compared to harbor seals in the Gulf of Alaska from the 1960s. In Chapter 2, morphometric measurements and reproductive tracts were collected by a Native Alaskan subsistence hunter from 40 male sea ...