Publication Date
Fall 2024
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Moss Landing Marine Laboratories
Advisor
Birgitte McDonald; Amanda Kahn; Kerstin Wasson
Abstract
This project investigated small-scale habitat use patterns of harbor seals (Phoca vitulina). The goals were to provide an updated overview of the harbor seal population in Elkhorn Slough, California, USA, identify haul-out areas that are seasonally relevant for pupping and molting, and analyze environmental factors that may influence the harbor seals’ abundance and distribution in the slough. Seal counts were conducted by Elkhorn Slough volunteers throughout the entire slough June 2020-May 2023. Additional survey data at the 5 most populated haul-out sites were collected by volunteers from MLML April 2022-May 2023. A comparison to harbor seal abundance data from 1991-1992 revealed a mean daily increase from 108 to 163 harbor seals hauled out in Elkhorn Slough. Results indicated that harbor seal abundance varied seasonally, with more seals hauled-out during the molting period (June-August). The primary environmental factor influencing harbor seal abundance was tide height with more seals hauled-out during lower tides. Harbor seal distribution also fluctuated in Elkhorn Slough, with the proportion of harbor seals changing among the 5 most populated haul-out sites depending on season and tide height. Harbor seal pups were not distributed evenly throughout the slough, nor did they match the distribution of the adults. This indicated preferential haul-out site use by harbor seals with pups. The knowledge gained in this study is important for future research and conservation decisions and can inform the design of seal population surveys to increase accuracy and efficacy.
Recommended Citation
Nicholson, Emma, "Use of a California Wetland: Harbor Seal (Phoca Vitulina) Haul-out Patterns in Elkhorn Slough" (2024). Master's Theses. 5602.
DOI: https://doi.org/10.31979/etd.8ku6-pw2v
https://scholarworks.sjsu.edu/etd_theses/5602
